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2017考博英语阅读模拟试题及答案

基本所有博士研究生招生院校都会有考博英语阅读题型，考博英语阅读的提高不仅需要知道解题技巧更应在平时的练习中加以运用，同时还可以复习考博英语词汇，freekaobo在此给大家整理了2017考博英语阅读练习，希望大家学以致用。

　Computer programmers often remark that computing machines, with a perfect lack of discrimination, will do any foolish thing they are told to do. The reason for this lies, of course, in the narrow fixation of the computing machine’s “intelligence” on the details of its own perceptions — its inability to be guided by any large context. In a psychological description of the computer intelligence, three related adjectives come to mind: single-minded, literal-minded, and simple-minded. Recognizing this, we should at the same time recognize that this single-mindedness, literal-mindedness, and simple-mindedness also characterizes theoretical mathematics, though to a lesser extent.
　　Since science tries to deal with reality, even the most precise sciences normally work with more or less imperfectly understood approximations toward which scientists must maintain an appropriate skepticism. Thus, for instance, it may come as a shock to mathematicians to learn that the Schrodinger equation for the hydrogen atom is not a literally correct description of this atom, but only an approximation to a somewhat more correct equation taking account of spin, magnetic dipole, and relativistic effects; and that this corrected equation is itself only an imperfect approximation to an infinite set of quantum field-theoretical equations. Physicists, looking at the original Schrodinger equation, learn to sense in it the presence of many invisible terms in addition to the differential terms visible, and this sense inspires an entirely appropriate disregard for the purely technical features of the equation. This very healthy skepticism is foreign to the mathematical approach.
　　Mathematics must deal with well-defined situations. Thus, mathematicians depend on an intellectual effort outside of mathematics for the crucial specification of the approximation that mathematics is to take literally. Give mathematicians a situation that is the least bit ill-defined, and they will make it well-defined, perhaps appropriately, but perhaps inappropriately. In some cases, the mathematicians literal-mindedness may have unfortunate consequences. The mathematicians turn the scientists’ theoretical assumptions that is, their convenient points of analytical emphasis, into axioms, and then take these axioms literally. This brings the danger that they may also persuade the scientists to take these axioms literally. The question, central to the scientific investigation but intensely disturbing in the mathematical context — what happens if the axioms are relaxed? — is thereby ignored.
　　The physicist rightly dreads precise argument, since an argument that is convincing only if it is precise loses all its force if the assumptions on which it is based are slightly changed, whereas an argument that is convincing though imprecise may well be stable under small perturbations of its underlying assumptions.
　　1. The author discusses computing machines in the first paragraph primarily in order to do which of the following?
　　[A] Indicate the dangers inherent in relying to a great extent on machines.
　　[B] Illustrate his views about the approach of mathematicians to problem solving.
　　[C] Compare the work of mathematicians with that of computer programmers.
　　[D] Provide one definition of intelligence.
　　2. It can be inferred form the text that scientists make which of the following assumptions about scientific arguments?
　　[A] The literal truth of the arguments can be made clear only in a mathematical context.
　　[B] The arguments necessarily ignore the central question of scientific investigation.
　　[C] The arguments probably will be convincing only to other scientists.
　　[D] The premises on which the arguments are based may change.
　　3. According to the text, mathematicians present a risk to scientist for which of the following reasons?
　　[A] Mathematicians may provide theories that are incompatible with those already developed by scientists.
　　[B] Mathematicians may define situations in a way that is incomprehensible to scientists.
　　[C] Mathematicians may convince scientists that theoretical assumptions are facts.
　　[D] Scientists may come to believe that axiomatic statements are untrue.
　　4. The author suggests that the approach of physicists to solving scientific problem is which of the following?
　　[A] Practical for scientific purposes.
　　[B] Detrimental to scientific progress.
　　[C] Unimportant in most situations.
　　[D] Expedient, but of little long-term value.
　　5. The author implies that scientists develop a healthy skepticism because they are aware that
　　[A] mathematicians are better able to solve problems than are scientists.
　　[B] changes in axiomatic propositions will inevitably undermine scientific arguments.
　　[C] well-defined situations are necessary for the design of reliable experiments.
　　[D] some factors in most situations must remain unknown.

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于菲

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58楼发表于: 2018-01-21

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One of the simplest and best known kinds of crystal is the ionic salt, of which a typical example is sodium chloride, or ordinary table salt. The fundamental components of an ionic salt are ions: atoms or molecules that have become electrically charged by gaining or losing one more electrons. In forming sodium chloride, for example, sodium atoms give up an electron (thereby becoming positively charged) and chlorine atoms gain an electron (thereby becoming negatively charged). The ions are attracted to one another by their opposite charges, and they stack together compactly, like tightly packed spheres.

　　Recently, scientists at Michigan State University created a new kind of crystal called an electride. In electrides, the anions (negative ions) are completely replaced by electrons, which are trapped in naturally formed cavities within a framework of regularly stacked cations (positive ions). Electrides are the first examples of ionic salts in which all these anionic sites are occupied solely by electrons.

　　Unlike other types of anions, anionic electrons do not behave as if they were simple charged spheres. In particular, because of their low mass and their tendency to interact with one another over great distances, they cannot be “pinned down” to any one location. Instead, they wander close to and among the atoms lining the cavity and interact with electrons in nearby cavities, perhaps changing places with them.

　　The properties of an electride depend largely on the distance between the cavities that hold trapped electrons. When the trapped electrons are far apart, they do not interact strongly, and so behave somewhat like an array of isolated negative charges. When they are closer together, they begin to display properties associated with large ensembles of identical particles. When they are still closer, the ensemble properties dominate and the electrons “delocalize”: they are no longer tightly bound within individual cavities but are more or less free to pass through the spaces within the framework of positive ions.

　　By synthesizing electrides from a variety of materials, one can vary the geometry of the anionic cavities and their relation to the surrounding cations. The resulting properties may make it possible for electrides to become a basis for economically useful new materials and devices. For instance, because the electrons in some electrides are very weakly bound, these crystals could be effective as photosensitive detectors, in which an impinging photon liberates an electron, resulting in a small electric current. The same weak binding could also make electrides useful in solar energy converters and as cathodes in batteries. One obstacle is the tendency of electrides to decompose through reaction with air and water. Researchers are seeking ways to increase their stability.

　　1. The text is primarily concerned with discussing

　　[A] a way to isolate electrons.

　　[B] the characteristics of a new kind of crystal.

　　[C] the structure of an ionic salt.

　　[D] commercial uses for electrides.

　　2. In the first paragraph, the author is primarily concerned with

　　[A] introducing a variant on the standard atomic theory.

　　[B] describing how chlorine atoms can become negatively charged.

　　[C] describing some early research at Michigan State University.

　　[D] providing background for the technical discussion to follow.

　　3. According to the text, the defining characteristic of an electride is which of the following?

　　[A] Its positive are of particularly low mass.

　　[B] Its ions possess identical electrical charges.

　　[C] It contains a framework of regularly stacked ions.

　　[D] Its negative ions consist solely of electrons.

　　4. It can be inferred from the text that anions behaving as “simple charged spheres” (line 2, paragraph 3) could be expected to

　　[A] readily lose electrons and become positively charged.

　　[B] move freely in and out of their cavities.

　　[C] respond to photons by liberating electrons.

　　[D] remain fixed relative to their cations.

　　5. With which of the following statements regarding electrides would the author most likely agree?

　　[A] They have proven themselves to be of great commercial value.

　　[B] Their future commercial value is promising but uncertain.

　　[C] They are interesting but of no practical value.

　　[D] They have commercial value mainly in solar energy applications.

　　[答案与考点解析]

　　1. 【答案】B

　　【考点解析】本题是一道中心主旨题。本文的中心主旨句在第二段的第一句，如果抓住了这句话并且联系每段的中心主旨句，就可得出本题的正确选项B。其实本文第二段就是在讲一种新的晶体的与众不同的“characteristics”(特点)。考生在解题时一定要首先找出全文的中心主旨句，并与上下文联系。

　　2. 【答案】D

　　【考点解析】这是一道段落关系题。从第二段到尾段是本文作者阐述其中心思想的段落。在展开中心思想之前，作者为中心思想的展开进行了铺垫(讲述一般晶体的特点)，从而为第二段到尾段的陈述(讲述一种新晶体的特点)提供明确的对比。考生在解题时一定要注意段落之间的关系。

　　3. 【答案】D

　　【考点解析】这是一道审题定位题。题干中没有给出明确的审题定位信息。破解此题需要考生平时的阅读积累，这是一道较难的题目。题干中所涉及的是“the defining characteristic of an electride”(电子晶体的特点)。在第二段作者第一次在文章中谈到了“electride”，所以其特点也应该在第二段向读者交待，故本题的答案信息来源应该在第二段。综合第二段第二、三句的内容可推导出本题的正确选项D。考生在解题时一定要具备出色的审题定位能力。

　　4. 【答案】D

　　【考点解析】本题是一道句间关系与反推题。题干中的信息以将本题的答案信息确定在第三段。根据第三段所陈述的内容进行反推可得出本题的正确选项D。在进行反推时一定要注意第一句中的“do not behave as if…”以及第二句中的“cannot be pinned down”所起的作用。考生在解题时一定要具备反推即逆向推理的能力。

　　5. 【答案】B

　　【考点解析】这是一道审题定位题。本题的题干没有提供任何审题定位的信息。但是善于阅读的考生应该知道每篇文章尾段的重要性。在本题到来之前本文的尾段还没有涉及任何一道题，故考生应该首先从尾段中寻找本题的答案信息。尾段的第二句第四句表明新的晶体在商业方面的可利用性;尾段的第五句表明这种新的晶体的不足之处。可见本题的正确选项应该是B。考生在解题时一定要对文章结构以及出题点有所认识，最好对全文有整体的把握。

　　[参考译文]

　　在各种最简单和最常见的晶体中，离子盐是其中一例，它典型的实例就是氯化钠，或普通的食盐。离子盐的基本组成成份便是离子，也就是那些由于得到或失去一个或多个电子而带有电荷的原子或分子。例如，在形成氯化钠的过程中，钠原子释放一个电子(从而带有正电荷)而氯电子得到一个电子(从而带有负电荷)。这些离子由于带有相反的电荷而相互吸引，它们紧密地堆砌在一起就象紧密挤压在一起的球体。

　　最近，密西根州立大学的科学家们研制出一种新的被称为电子晶体的晶体。在电子晶体中，阴离子(即带负电荷的离子)全部被电子替代，这些电子被困在自然形成的空穴中，而空穴位于规则堆砌的阳离子(即带正电荷的离子)的框架内。电子晶体是第一种阴离子空间全被电子占据的离子盐。

　　和其它类型的阴离子不同，作为阴离子的电子不像那些简单的带电球体。特别地，由于它们的质量很小而且有与远距离的离子进行相互作用的倾向，它们不会被固定在任何一个位置。相反，它们会到处游离，或者紧靠那些在空穴边上的原子，或者在这些原子之间游离，并且还和附近空中的电子发生相互作用，甚至于可能与它们交换位置。

　　电子晶体的特征很大程度上依赖于空穴间的距离，而这些空穴便是容纳被捕获电子的地方。当这些被捕获的电子相距很远时，它们之间的相互作用不强，因而在某种程度上表现为一组相互孤立的负电荷。但当它们间的距离很近时，它们便表现出一些特征来，很像大量相同离子的集合。当它们间的距离更近时，群体集合属性更占主导地位，而且电子也出现“离位”现象：它们不再被束缚于单个的空穴之上，而是或多或少地可以在正离子的构架之间穿越。

　　通过从不同的材料来合成电子晶体，科学家们可以改变阴离子空穴的几何结构，以及改变它们同周围阴离子之间的关系。这些随之而来的特征使得电子晶体可能成为经济实用的新材料和新设备的基础。例如，由于在某些电子晶体中，电子结合得非常微弱，从而使得这些晶体可以有效地用作光敏探测器。在这种探测器中，一束光子可以释放一个电子，从而形成一股小电流。这种结合微弱的特性同样可使电子晶体对太阳能转换器和电池的阴极很有用。可电子晶体的一个缺陷在于它易于与空气和水发生反应而分解。目前，研究人员正设法寻找提高电子晶体稳定性的方法。

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56楼发表于: 2016-08-17

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The complications frequently accompanying diabetes, such as impairment of vision and of kidney function, are now thought to result from the lack of continuous control of blood glucose concentrations. The healthy pancreas, in response to increases in blood glucose concentration, releases small quantities of insulin throughout the day and thereby maintains the concentration within physiological limits (nomoglycemia). But the diabetic generally receives only one large dose daily. The diabetic’s blood glucose concentration can thus fluctuate greatly during the interval between doses, and it has been suggested that the complication result from the periods of high concentrations of blood glucose (hyperglycemia). Many investigators thus believe that restoration of normoglycemia might halt the progression of such complications and perhaps even reverse them.

　　There are three primary techniques that have been investigated for restoration of normoglycemia. They are: transplantation of whole, healthy pancreases; transplantation of islets of Langerthan, that portion of the pancreas that actually secretes insulin, and implantation of artificial pancreases. There has, in fact been a great deal of success in the development of these techniques and each seems, on the whole, promising. Nonetheless, it will undoubtedly be many years before any one of them is accepted as a treatment for diabetes.

　　To many people, the obvious approach would seem to be simply to transplant pancreases from cadavers in the same manner that kidneys and other organs are routinely transplanted. That was the rationale in 1966 when the first recorded pancreas was performed. Between 1960 and 1975, there were forty-six pancreas transplants in forty-five other patients in the United States and five other countries. But only one of these patients is still alive with a functioning graft and surgeons have found that the procedure is not simple as they once thought.

　　The surviving patient has required no insulin since the operation. Another patient survived 638 days without requiring insulin. And one patient survived a transplantation for more than a year, but died when he chose not to take immunosuppressive drugs. These results, though meager, suggest that the procedure has the potential for success.

　　The rest of the patients, however, either rejected the transplant or died within a short period. There does not appear to be any technical problem with the procedure. Rather, most of the patients were already so severely debilitated by the complications of diabetes that they could not withstand the surgery and the immunosuppressive regimen required to prevent rejection. More than half of the patients, furthermore, also required a kidney transplant. Most investigators now agree that the simultaneous transplantation of both organs is too great a shock to the patient and greatly increases the total risk.

　　1. Which of the following best states one of the main conclusions of the text?

　　[A] Although the techniques for pancreas transplants appear to be theoretically correct, there are problems that must be solved before the operation can be used as a treatment for diabetes.

　　[B] Although the techniques for pancreas transplants are still being developed, the experimental results show that the operation will be a successful treatment for diabetes in the near future.

　　[C] Although pancreas transplants are reliable, many diabetics are reluctant to undergo the operation because of the side effects of immunosuppressive drugs.

　　[D] Although pancreas transplants alone are not generally successful, the operation can be used in conjunction with other procedures to treat diabetes.

　　2. According to the text, widely spaced doses of insulin can cause

　　[A] reversal of normal kidney function.

　　[B] delay in the onset of diabetes.

　　[C] radical changes in the concentration of blood glucose.

　　[D] restoration of normoglycemia.

　　3. According to the text, a periodic high concentration of blood glucose in diabetics is a possible cause of

　　[A] deterioration of the pancreas.

　　[B] damage to the eyes and kidneys.

　　[C] rejection of transplanted organs.

　　[D] inadequate secretion of insulin.

　　4. It can be inferred from the text that one of the important contributing causes of the failure of most pancreas transplants has been the

　　[A] reluctance of patients to cooperate with physicians.

　　[B] imperfect techniques used in the operation.

　　[C] scarcity of immunosuppressive drugs.

　　[D] weakened condition of the patients.

　　5. The text suggests that the author considers the data concerning the success of pancreas transplants to be

　　[A] invalid.

　　[B] indirect.

　　[C] inaccurate.

　　[D] insufficient.

　　[答案与考点解析]

　　1. 【答案】A

　　【考点解析】本题是一道审题定位题。本题的题干比较奇怪，没有明确指出本题答案信息在原文中的确切位置。在大多数情况下，考生会迷失解题思路。我们一再重申：考生在迷失解题思路时一定要多想一想全文的中心主旨句，以及各段的主题句。本文的中心主旨句是第二段的尾句，本题的正确选项A恰恰是来自于本句。这再次说明我们在迷失解题思路时应该首先想到全文的中心主旨句或每段的主题句。

　　2. 【答案】C

　　【考点解析】这是一道细节推导题。通过本题题干中的“widely spaced doses of insulin”可将本题的答案信息来源确定在首段的第三、四句。因为这两句话提到了“doses of insulin”。通过仔细阅读和理解第三、四句，就可推导出本题的正确选项C。考生在解题时一定要善于理解和把握题干和原文所进行的同义词替换。

　　3. 【答案】B

　　【考点解析】这是一道句间关系题。通过题干中的“periodic high concentration”可将本题的答案信息来源迅速确定在第一段的第四句。通过仔细阅读和理解第四句，尤其是把第四句中的“complication”和第一句中的“complications”进行连贯的理解，就可推导出本题的正确选项B。考生在解题时要善于发现和理解句子之间的关系。

　　4. 【答案】D

　　【考点解析】这是一道细节推导题。通过题干中的“failure”一词可推断本题的正确答案信息在倒数第二段尾句的前后，因为该句所谈论的中心话题是“success”。又根据题干中的“most”一词将本题的答案信息确定在尾段的第三句，因为该句中含有“most”一词。通过阅读和理解尾段第三句，可推导出本题的正确答案是D。考生在解题时要注意灵活理解题干和原文所表达的内容，千万不能生硬地进行理解。

　　5. 【答案】D

　　【考点解析】本文是一道词汇理解题。本题题干中的“success”将本题的答案信息来源确定在倒数第二段的尾句。该句中的“meager”(不足的，贫乏的)暗示本题的正确选项是D。考生在解题时一定要对关键词加以重视并进行合理的推断。

　　[参考译文]

　　通常与糖尿病相伴的并发症，如视力和肾功能的损害，现在被认为是由于无法连续控制血液中的葡萄糖浓度所导致的。健康的胰脏，在血糖浓度增加时，会在整个白天不断地释放出少量的胰岛素，从而使血糖浓度维持在生理限度之内(正常血糖量)。但是糖尿病患者一般是每天得到一次大剂量胰岛素的注射。这样在两次注射之间，糖尿病患者的血糖浓度会发生很大波动，而且目前已被指出，并发症可能就是源于这些高血糖浓度时期(高血糖)。因此，许多研究人员相信，恢复正常的血糖浓度或许能阻止这些并发症的发展，并进而可能减轻并发症。

　　为了恢复正常的血糖浓度，已对三种主要的技术进行了研究。它们分别是：健康胰脏的整个移植;胰岛部分的移植，胰岛是胰腺中实际分泌胰岛素的部分;以及人造腺的移植。事实上，这些技术的发展都获得了成功，而且从整体上讲，每种技术都大有希望。然而，毫无疑问地，在任何一种技术被接受用作糖尿病患者的治疗手段之前，还会有很多年的时间。

　　对多数人而言，显而易见的方法看来可能是从尸体中移植胰腺，就象移植肾脏和其它器官那样。这便是1966年第一例胰腺移植手术的理论基础。在1966年至1975年间，在美国和另外五个国家，共有45名其它病人进行了46例胰腺移植手术。但目前，只有其中一个病人尚在人世，而且移植的胰腺功能健全。因此，手术医生们发现，手术过程并不像他们先前想象的那么简单。

　　幸存的病人从那次手术之后不再需要注射胰岛素。另一个病人在不需要注射胰岛素的情况下活了638天。还有一名病人在移植之后存活了一年，但他决定不服用免疫药物之后就死去了。这些结果，尽管为数不多，可也表明了手术过程有潜在成功的可能。

　　然而，其余的病人或者出现排异反应，或者在很短一段时期后死去。在手术过程中，看起来是不存在任何技术问题的。不过，大多数的病人都由于糖尿病的并发病已经很衰弱，以至于无法经受手术和为防止排异反应所需的免疫抑制疗程。另外，一大半病人还需要进行肾脏移植。目前，多数研究人员都认为同时移植两个器官对病人自身系统影响太大，而且极大地增加了整体的风险。

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55楼发表于: 2016-08-16

只看该作者 ┊ 小中大

Although recent years have seen substantial reductions in noxious pollutants from individual motor vehicles, the number of such vehicles has been steadily increasing. Consequently, more than 100 cities in the United States still have levels of carbon monoxide, particulate matter, and ozone (generated by photochemical reactions with hydrocarbons from vehicle exhaust) that exceed legally established limits. There is a growing realization that the only effective way to achieve further reductions in vehicle emissions — short of a massive shift away from the private automobile — is to replace conventional diesel fuel and gasoline with cleaner-burning fuels such as compressed natural gas, liquefied petroleum gas, ethanol, or methanol.

　　All of these alternatives are carbon-based fuels whose molecules are smaller and simpler than those of gasoline. These molecules burn more cleanly than gasoline, in part because they have fewer, if any, carbon-carbon bonds and the hydrocarbons they do emit are less likely to generate ozone. The combustion of larger molecules, which have multiple carbon-carbon bonds involves a more complex series of reactions. These reactions increase the probability of incomplete combustion and are more likely to release uncombusted and photochemically active hydrocarbon compounds into the atmosphere. On the other hand, alternative fuels do have drawbacks. Compressed natural gas would require that vehicles have set of heavy fuel tanks — a serious liability in terms of performance and fuel efficiency — and liquefied petroleum gas faces fundamental limits on supply.

　　Ethanol and methanol, on the other hand, have important advantages over other carbon-based alternative fuels: they have higher energy content per volume and would require minimal changes in the existing network for distributing motor fuel. Ethanol is commonly used as a gasoline supplement, but it is currently about twice as expensive as methanol, the low cost of which is one of its attractive features. Methanol’s most attractive feature, however, is that it can reduce by about 90 percent the vehicle emissions that form ozone, the most serious urban air pollutant.

　　Like any alternative fuel, methanol has its critics. Yet much of the criticism is based on the use of “gasoline clone” vehicles that do not incorporate even the simplest design improvements that are made possible with the use of methanol. It is true, for example, that a given volume of methanol provides only about one-half of the energy that gasoline and diesel fuel do; other things being equal, the fuel tank would have to be somewhat larger and heavier. However, since methanol-fueled vehicles could be designed to be much more efficient than “gasoline clone” vehicles fueled with methanol they would need comparatively less fuel. Vehicles incorporating only the simplest of the engine improvements that methanol makes feasible would still contribute to an immediate lessening of urban air pollution.

　　1. The author of the text is primarily concerned with

　　[A] countering a flawed argument that dismisses a possible solution to a problem.

　　[B] reconciling contradictory points of view about the nature of a problem.

　　[C] identifying the strengths of possible solutions to a problem.

　　[D] discussing a problem and arguing in favor of one solution to it.

　　2. According to the text, incomplete combustion is more likely to occur with gasoline than with an alternative fuel because

　　[A] the combustion of gasoline releases photochemically active hydrocarbons.

　　[B] the combustion of gasoline embraces an intricate set of reactions.

　　[C] gasoline molecules have a simple molecular structure.

　　[D] gasoline is composed of small molecules.

　　3. The text suggests which of the following about air pollution?

　　[A] Further attempts to reduce emissions from gasoline-fueled vehicles will not help lower urban air-pollution levels.

　　[B] Attempts to reduce the pollutants that an individual gasoline-fueled vehicle emits have been largely unsuccessful.

　　[C] Few serious attempts have been made to reduce the amount of pollutants emitted by gasoline-fueled vehicles.

　　[D] Pollutants emitted by gasoline-fueled vehicles are not the most critical source of urban air pollution.

　　4. Which of the following most closely parallels the situation described in the first sentence of the text?

　　[A] Although a town reduces its public services in order to avoid a tax increase, the town’s tax rate exceeds that of other towns in the surrounding area.

　　[B] Although a state passes strict laws to limit the type of toxic material that can be disposed of in public landfills, illegal dumping continues to increase.

　　[C] Although a town’s citizens reduce their individual use of water, the town’s water supplies continue to dwindle because of a steady increase in the total populating of the town.

　　[D] Although a country attempts to increase the sale of domestic goods by adding a tax to the price of imported goods, the sale of imported goods within the country continues to increase.

　　5. It can be inferred that the author of the text most likely regards the criticism of methanol as

　　[A] flawed because of the assumptions on which it is based.

　　[B] inapplicable because of an inconsistency in the critics’ arguments.

　　[C] misguided because of its exclusively technological focus.

　　[D] inaccurate because it ignores consumers’ concerns.

　　[答案与考点解析]

　　1. 【答案】C

　　【考点解析】这是一道中心主旨题。本文的中心主旨句是首段的尾句。通过对首段尾句以及其它段落主题句的阅读和理解，可以推导出本题的正确选项是C。考生在破解此类题型时一定要首先抓住原文的中心主旨句以及各段的主题句。

　　2. 【答案】B

　　【考点解析】本题是一道指代词题型。根据题干中的“incomplete combustion”可将本题的答案信息来源迅速确定在第二段的第四句，该句中的指代词“these”暗示本题的具体答案信息来源应该在第二段的第三句。通过阅读和理解第二段的第三句可推导出本题的正确选项是B。考生在解题时对指代词一定要认真理解。

　　3. 【答案】A

　　【考点解析】本题是一道审题定位题型。通过题干中的“air pollution”可将本题的答案信息来源迅速确定在第一段，因为第一段首句中含有“noxious pollutants”，都在谈污染的问题。通过阅读和理解第一段，尤其是第一段尾句即全文的中心主旨句，可推导出本题的正确选项是A。这是一道比较难的题。考生在解题时一定要具备审题定位能力，还要具备归纳和推导能力。

　　4. 【答案】C

　　【考点解析】这是一道类比题型，因为本题题干中含有“parallels”(与……相当，与……一样)一词。本题题干已将类比的参照对象确定在第一段的首句。通过仔细阅读和理解第一段的首句，可推导出本题的正确选项是C，因为该选项涉及的增减关系的前提条件和原文一脉相承。考生在破解这种题型时应对原文所表达的内容与关系有明确的认识和把握，不可以无根据地推导。

　　5. 【答案】A

　　【考点解析】这是一道细节推导题型。本题题干中的“the criticism of methanol”把本题的答案信息来源确定在第四段的第一、二句。通过阅读和理解这两句话，尤其是第二句话，就可推导出本题的正确选项A。考生在破解本题时一定要注意第二句话的第一个词“Yet”在语意上所起的作用。考生在解题时一定要重视启承转合词的出现和功能。

　　[参考译文]

　　近年来，尽管单个机动车辆排放的有毒污染物已大幅减少，但这些机动车辆的数量一直在持续增长，结果是，在美国有100多个城市的大气中一氧化碳、灰尘和臭氧(由车辆尾气中的碳氢化合物经光化反应产生)的含量已超出了法定的限度。人们愈来愈认识到，实现车辆废气进一步减少而又不必大规模减少私家轿车的唯一有效途径是用清洁燃料来代替传统的柴油和汽油燃料。这些清洁燃料包括压缩天然气、液化石油气、乙醇和甲醇。

　　所有这些替代产品都是碳基燃料，不过它们的分子要比汽油的分子小且简单。它们可以比汽油燃烧得更彻底，部分原因在于，即使它们含有碳—碳化学键，含量也较少，而且它们释放的碳氢化合物也不大可能产生臭氧。那些具有多重碳——碳化学键的大分子在燃烧时包含了一系列复杂的反应。这些反应增大了不完全燃烧的可能，并且更容易释放未燃烧的碳氢化合物，而这些化合物又对光化学反应很活跃。另一方面，这些替代燃料也有自己的缺点。压缩天然气可能需要车辆配备一个笨重的油箱，这对车辆性能和燃料效率又极为不利，并且液化石油气还面临着供应上的根本限制。

　　从另一方面来看，甲醇和乙醇与其它的碳基替代燃料相比有重要的益处：它们具有单位体积更高的能量含量，而且对现存的燃料销售网络只需很小地改变。乙醇通常作为汽油的替代品，但目前它比甲醇要贵两倍，因此甲醇的低廉价格便成为引人注目的特点。然而，甲醇最吸引人的特点还在于它可以减少90%形成臭氧的废气，而臭氧又是城市中最严重的污染物。

　　和其它的替代燃料一样，甲醇也遭到了非难。可大多数批评都建立在使用“汽油系列”的车辆不进行最简单的设计改进以可能使用甲醇燃料的基础上。例如，事实上一定体积的甲醇和同体积的汽油和柴油相比，只能提供相当于它们大约一半的能量。在其它因素相同的条件下，油箱可能要大一点和重一点，然而，由于甲醇燃料的车辆可以设计得比使用甲醇的“汽油系列”车辆还要高效，它们可能需要更少的燃料。同时，对发动机进行最简单的改进便可使用甲醇的车辆，这将对城市大气污染的迅速减轻做出贡献。

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54楼发表于: 2016-08-16

只看该作者 ┊ 小中大

The intensive work of materials scientists and solid-state physicists has given rise to a class of solids known as amorphous metallic alloys or glassy metals. There is a growing interest among theoretical and applied researchers alike in the structural properties of these materials.

　　When a molten metal or metallic alloy is cooled to a solid, a crystalline structure is formed that depends on the particular alloy composition. In contrast, molten nonmetallic glass-forming materials when cooled do not assume a crystalline structure, but instead retain a structure somewhat like that of the liquid — an amorphous structure. At room temperature the natural long-term tendency for both types of materials is to assume the crystalline structure. The difference between the two is in the kinetics or rate of formation of the crystalline structure which is controlled by factors such as the nature of the chemical bonding and the ease with which atoms move relative to each other. Thus, in metals, the kinetics favors rapid formation of a crystallines structure whereas in nonmetallic glasses the rate of formation is so slow that almost any cooling rate is sufficient to result in an amorphous structure. For glassy metals to be formed, the molten metal must be cooled extremely rapidly so that crystallization is suppressed.

　　The structure of glassy metals is thought to be similar to that of liquid metals. One of the first attempts to model the structure of a liquid was that by the late J. D. Bernal of the University of London, who packed hard spheres into a rubber vessel in such a way as to obtain the maximum possible density. The resulting dense, random-packed structure was the basis for many attempts to model the structure of glassy metals.

　　Calculations of the density of alloys based on Bernal-type models of the alloys metal component agree fairly well with the experimentally determined values from measurements on alloys consisting of a noble metal together with a metalloid such as alloys of palladium and silicon or alloys consisting of iron phosphors, and carbon, although small discrepancies remained. One difference between real alloys and the hard spheres area in Bernal models is that the components of an alloy have different size, so that models based on two sizes of spheres are more appropriate for a binary alloy for example. The smaller metalloid atoms of the alloys might fit into holes in the dense random-packed structure of the larger metal atoms.

　　One of the most promising properties of glassy metals is their high strength combined with high malleability. In usual materials, one finds an inverse relation between the two properties, whereas for many practical applications simultaneous presence of both properties is desirable. One residual obstacle to practical applications that is likely to be overcome is the fact that glassy metals will crystallize at relatively low temperatures when heated slightly.

　　1. The author is primarily concerned with discussing

　　[A] crystalline solids and their behavior at different temperatures.

　　[B] molten materials and the kinetics of the formation of their crystalline structure.

　　[C] glassy metals and their structural characteristics.

　　[D] metallic alloys and problems in determining their density.

　　2. The author’s attitude toward the prospects for the economic utilization of glassy metals is one of

　　[A] disinterest.

　　[B] impatience.

　　[C] optimism.

　　[D] apprehension.

　　3. According to the text, which of the following determines the crystalline structure of a metallic alloy?

　　[A] At what rate the molten alloy is cooled.

　　[B] How rapid the rate of formation of the crystalline phase is.

　　[C] How the different-sized atoms fit into a dense random-packed structure.

　　[D] What the alloy consists of and in what ratios.

　　4. Which of the following best describes the relationship between the structure of liquid metals and the structure of glassy metals, as it is presented in the text?

　　[A] The latter is an illustrative example of the former.

　　[B] The latter is a large-scale version of the former.

　　[C] The former is a structural elaboration of the latter.

　　[D] The former is a fair approximation of the latter.

　　5. It can be inferred from the text that, theoretically, molten nonmetallic glasses assume a crystalline structure rather than an amorphous structure only if they are cooled

　　[A] very evenly, regardless of the rate.

　　[B] rapidly, followed by gentle heating.

　　[C] very slowly.

　　[D] to room temperature.

　　[答案与考点解析]

　　1. 【答案】C

　　【考点解析】本题是一道中心主旨题。本文的中心主旨句是首段的第二句，该句中的“these materials”指的就是首段第一句中的“amorphous metallic alloys or glassy metals”。可见本题的正确答案应该是C。考生一定要知道：破解中心主旨题的关键在于抓住全文的中心主旨句。

　　2. 【答案】C

　　【考点解析】本题是一道审题定位题。根据题干中的“prospects”(前景)可将本题的答案信息迅速确定在尾段，因为尾段首句中的“promising”(有前途的)暗示本段讲某种事物的前景或未来。本题的确切答案信息来源在尾段的最后一句，该句中的“that is likely to be overcome”暗示本题的正确答案是C。考生在解题时一定要具备迅速地审题定位能力，还要具备理解原文深层含义的能力。

　　3. 【答案】D

　　【考点解析】这是一道细节推导题。根据题干中的“crystalline structure”可将本题的答案迅速确定在第二段的首句，该句中的“depends on”和题干中的“determines”相互呼应。通过仔细理解第二段的首句可推导出本题的正确选项是D。请考生注意原文中“composition”和选项中“consists of”的转换。考生在解题时一定要具备细节推导能力，不能只停留于文字的表面含义。

　　4. 【答案】D

　　【考点解析】这是一道细节推导题。根据题干中的“the structure of liquid metals and the structure of glassy metals”可将本题的答案信息来源迅速确定在第三段的首句。该句中的“similar”一词暗示选项D是正确答案。考生在解题时应重视对立对比关系。

　　5. 【答案】C

　　【考点解析】本题是一道总结归纳信息并进行引申推导题型。从本题题干中的“molten nonmetallic glasses”可断定本题的答案信息在本文第二段，因为该句中包含有题干中的核心词语“molten nonmetallic glasses”。我们需要归纳和总结本段的每一句话，尤其是第三、四句的内容，另外本段尾句的含义为推导(infer)出本题的正确选项C起到至关重要的作用。考生在破解此类题型时一定要注意首先归纳和总结原文中相应出题点的全面信息，更要注意逻辑推导的能力。

　　[参考译文]

　　材料科学家和固体物理学家的深入研究已促进了一种固体物质的出现，这类固体被称为非晶体金属合金，也就是玻璃金属。理论和应用研究者对这些材料的结构特性的兴趣正与日俱增。

　　当一种熔化的金属和金属合金冷却成固体时，依赖于特定的合金成份将形成各种晶体结构。相比之下，熔化的非金属、玻璃类材料在冷却后将不会形成晶体结构，而是保留一点类似于液体的非晶体结构，在室温条件下，两类材料的自然的长期倾向都形成了晶体结构。它们之间的不同在于动态性，即形成晶体结构的速度。这种动态性受下述两种因素控制：化学结合的性质和分子之间相互运动的自由程度。由此，对金属而言，动态历程有利于晶体结构的快速形成;而对非金属来说，这种形成速度非常慢，以至于任何自然冷却速度都足以形成一种非晶体结构。要想形成玻璃金属，熔化的金属必须以极快的速度冷却，以抑制晶体的形成。

　　人们认为玻璃金属的结构与液态金属的结构类似。创建这种液体结构模型的第一次尝试是已故的伦敦大学的J. D.鲍纳尔进行的，他将坚硬的球体尽可能多地填塞进一个橡胶容器中，以便得到一种最大可能的密度。这个密度结果以及随机填塞结构以后便成为试图建立玻璃金属结构模型的基础。

　　基于鲍纳尔模型，由合成金属的成份组成对合金密度的计算结果与实验测得的结果相当地吻合，当然一些细微的差异仍然存在。实验结果是通过测量由一种重金属和类金属组成的合金得到的，如钯和硅的合金，或铁磷和碳组成的合金。实际的合金和鲍纳尔模型所用的球体之间的差别在于合金的成份有不同的体积大小，因此，基于两种大小的球体的模型更适合于两类物质的合金。合金中非金属的小原子可能填进由大原子随机填塞形成的紧密结构中。

　　玻璃金属最有前景的一个特征是高强度与高延伸性的结合。在常见的晶体材料中，这两种特性一般是成反比的，但人们渴望它们同时存在。在实际用途中可能还有一个问题急待解决，即当玻璃金属在相对的低温下慢慢加热时，它会逐渐变为晶体结构。

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53楼发表于: 2016-08-16

只看该作者 ┊ 小中大

Historians have only recently begun to note the increase in demand for luxury goods and services that took place in eighteenth-century England. McKendrick has explored the Wedgwood firm’s remarkable success in marketing luxury pottery; Plumb has written about the proliferation of provincial theater, musical festivals, and children’s toys and books. While the fact of this consumer revolution is hardly in doubt, three key questions remain: Who were the consumers? What were their motives? And what were the effects of the new demand for luxuries?

　　An answer to the first of these has been difficult to obtain. Although it has been possible to infer from the goods and services actually produced what manufacturers and servicing trades thought their customers wanted, only a study of relevant personal documents written by actual consumers will provide a precise picture of who wanted what. We still need to know how large this consumer market was and how far down the social scale the consumer demand for luxury goods penetrated. With regard to this last question, we might note in passing that Thompson, while rightly restoring laboring people to the stage of eighteenth-century English history, has probably exaggerated the opposition of these people to the inroads of capitalist consumerism in general; for example, laboring people in eighteenth-century England readily shifted from home-brewed beer to standardized beer produced by huge, heavily capitalized urban breweries.

　　To answer the question of why consumers became so eager to buy, some historians have pointed to the ability of manufacturers to advertise in a relatively uncensored press. This, however, hardly seems a sufficient answer. Mckendrick favors a Veblem model of conspicuous consumption stimulated by competition for status. The “middling sort” bought goods and services because they wanted to follow fashions set by the rich. Again, we may wonder whether this explanation is sufficient. Do not people enjoy buying things as a form of self-gratification? If so, consumerism could be seen as a product of the rise of new concepts of individualism and materialism, but not necessarily of the frenzy for conspicuous competition.

　　Finally, what were the consequences of this consumer demand for luxuries? McKendrick claims that it goes a long way toward explaining the coming of the Industrial Revolution. But does it? What, for example, does the production of high-quality pottery and toys have to do with the development of iron manufacture or textile mills? It is perfectly possible to have the psychology and reality of a consumer society without a heavy industrial sector.

　　That future exploration of these key questions is undoubtedly necessary should not, however, diminish the force of the conclusion of recent studies: the insatiable demand in eighteenth-century England for frivolous as well as useful goods and services foreshadows our own world.

　　1. In the first paragraph, the author mentions McKendrick and Plumb most probably in order to

　　[A] contrast their views on the subject of luxury consumerism in eighteenth-century England.

　　[B] indicate the inadequacy of historiographical approaches to eighteenth-century English history.

　　[C] give examples of historians who have helped to establish the fact of growing consumerism in eighteenth-century England.

　　[D] support the contention that key questions about eighteenth-century consumerism remain to be answered.

　　2. Which of the following items, if preserved from eighteenth-century England, would provide an example of the kind of documents mentioned in lines 3-4, paragraph 2?

　　[A] A written agreement between a supplier of raw materials and a supplier of luxury goods.

　　[B] A diary that mentions luxury goods and services purchased by its author.

　　[C] A theater ticket stamped with the date and name of a particular play.

　　[D] A payroll record from a company that produced luxury goods such as pottery.

　　3. According to the text, Thompson attributes to laboring people in eighteenth-century England which of the following attitudes toward capitalist consumerism?

　　[A] Enthusiasm.

　　[B] Curiosity.

　　[C] Ambivalence.

　　[D] Hostility.

　　4. In the third paragraph, the author is primarily concerned with

　　[A] contrasting two theses and offering a compromise.

　　[B] questioning two explanations and proposing a possible alternative to them.

　　[C] paraphrasing the work of two historians and questioning their assumptions.

　　[D] examining two theories and endorsing one over the other.

　　5. According to the text, eighteenth-century England and the contemporary world of the text readers are

　　[A] dissimilar in the extent to which luxury consumerism could be said to be widespread among the social classes.

　　[B] dissimilar in their definitions of luxury goods and services.

　　[C] dissimilar in the extent to which luxury goods could be said to be stimulant of industrial development.

　　[D] similar in their strong demand for a variety of goods and services.

　　[答案与考点解析]

　　1. 【答案】C

　　【考点解析】本题是一道例(举)证题型。根据题干中的“McKendrick and Plumb”可将本题的答案信息来源迅速确定在首段的第二、三句。由于这两句话和首段第一句之间存在例(举)证的关系，故针对首段第一句进行认真理解。通过综合分析和归纳这三句话，可得出含有“examples”的选项C是正确答案。考生在解题时一定要善于识别题型，这一点的基础是要学会识别句子之间的关系。

　　2. 【答案】B

　　【考点解析】这是一道细节推导题。题干中的信息以将本题的答案信息来源确定在第二段的三、四行。即第二段第二句的主句，该句中的“only a study of relevant personal documents written by actual consumers”暗示本题的答案是选项B。考生在解题时一定要学会识别原文和选项中同义词的替换。

　　3. 【答案】D

　　【考点解析】本题是一道细节推导题。通过题干中的“Thompson”一词可迅速将本题的正确选项确定在第二段的尾句。从第二段尾句的前半部分即分号前面的部分我们不难推导出本题正确选项是D。原文中的“opposition”一词十分重要。考生在解题时要善于从原文的表面归纳出深刻的思想。

　　4. 【答案】B

　　【考点解析】这是一道写作手法题型。旨在考察考生的语言基本功。本题考察考生对于段落写作结构的认识。本文第三段的第一、二句是对某一个问题的一种解释。本文第三段的第三、四、五句是对同一个问题的另一种解释，本文作者对这两种解释提出了质疑。本文第三段的第六、七句是作者本人针对前面两个解释所提出的另外一种解释。可见本题的正确选项是B。考生在解题时一定要重视文章或段落的写作结构。

　　5. 【答案】D

　　【考点解析】本题是一道审题定位与关键词理解题。通过题干中的“the contemporary world of the text readers”可将本题的答案信息迅速确定在尾段，因为尾段中的“our own world”等于“the contemporary world of the text readers”。尾段最后一行中的“foreshadows”(预示;是……的预兆)一词暗示本题的正确选项是D。考生在解题时一定要有审题定位能力，并且对于原文中的关键词要有入目三分的理解。

　　[参考译文]

　　直到最近，史学家们才发现在十八世纪的英国，对豪华奢侈商品和服务的需求出现增长的现象。麦克德瑞克研究了韦奇伍德公司在营销豪华陶制品方面的极大成功;而普拉姆也著文论述了地方剧院、音乐节目以及儿童玩具和书籍激增的情形。尽管这场消费者革命的事实几乎毋庸置疑，但仍有三个关键的问题尚待解决：消费者是些什么人?他们的动机是什么?以及这种对奢侈品的新需求的社会影响是什么?

　　关于第一问题的答案是很难获得的。尽管它可能从制造商和服务行业认为消费者想要什么而实际制造的商品和提供的服务中推知，但只有对实际消费者的相关私人资料的研究才能提供一种“谁想要什么”的精确状况。我们仍然需要知道这种消费市场到底有多大，以及消费者对奢侈商品的需求向下渗透到社会的什么层次。对最后一个问题而言，我们应当注意到，在过去，汤姆逊虽然正确恢复了劳动人民在十八世纪英国历史舞台上的地位，但整体而言可能夸大了他们对资本主义消费方式侵蚀的抵抗情绪。例如，十八世纪英国的劳动人民迅速从家酿的啤酒转而饮用由那些大规模、高度资本化的城市酿酒厂生产的标准化啤酒。

　　为了回答消费者为什么变得那么急于购物这一问题，一些史学家指出，这是因为制造商们可以在无需审查的报刊上刊登广告。然而，这似乎并不是个理由充分的答案。麦克德瑞克赞成维布伦模型，即由社会地位的竞争而引起的一种引人注目的消费。“中产阶级”购买优质商品和服务，是因为他们想追随由富人建立的消费时尚。我们可能再次怀疑这种解释是否充足。难道人们喜爱购物不是一种自我满足的形式吗?如果是这样，那么上述消费主义可以被看做是一种个人主义和物质主义新兴概念的产物，而不一定是疯狂进行引人注目的竞争的结果。

　　最后，这种消费者对奢侈品的需求所导致的后果又是什么呢?麦克德瑞克声称，这将极为有助于解释工业革命的到来。但事实果真如此吗?例如，高质量的陶制品和玩具与钢铁制造和纺织工厂的发展有什么关系呢?即使没有重工业的存在，消费社会在心理上和现实上都是完全可能存在的。

　　然而，对这些关键问题的进一步探究毫无疑问是需要的，而且不应当减弱近期研究所得结论的说服力：十八世纪英国对那些有用和琐碎商品及服务的不知足的需求预示了我们目前的这个世界的特征。

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52楼发表于: 2016-08-12

只看该作者 ┊ 小中大

　As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation. The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run. The great variety of dynamic behaviors exhibited by different population makes this task more difficult: some populations remain roughly constant from year to year; others exhibit regular cycles of abundance and scarcity; still others vary wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.

　　To impose some order on this kaleidoscope of patterns, one school of thought proposes dividing populations into two groups. These ecologists posit that the relatively steady populations have “density-dependent” growth parameters; that is, rates of birth, death, and migration which depend strongly on population density. The highly varying populations have “density-independent” growth parameters, with vital rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.

　　This dichotomy has its uses, but it can cause problems if taken too literally. For one thing, no population can be driven entirely by density-independent factors all the time. No matter how severely or unpredictably birth, death, and migration rates may be fluctuating around their long-term averages, if there were no density-dependent effects, the population would, in the long run, either increase or decrease without bound (barring a miracle by which gains and losses canceled exactly). Put another way, it may be that on average 99 percent of all deaths in a population arise from density-independent causes, and only one percent from factors varying with density. The factors making up the one percent may seem unimportant, and their cause may be correspondingly hard to determine. Yet, whether recognized or not, they will usually determine the long-term average population density.

　　In order to understand the nature of the ecologist’s investigation, we may think of the density-dependent effects on growth parameters as the “signal” ecologists are trying to isolate and interpret, one that tends to make the population increase from relatively low values or decrease from relatively high ones, while the density-independent effects act to produce “noise” in the population dynamics. For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown. For irregularly fluctuating populations, we are likely to have too few observations to have any hope of extracting the signal from the overwhelming noise. But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions.

　　1. The author of the text is primarily concerned with

　　[A] discussing two categories of factors that control population growth and assessing their relative importance.

　　[B] describing how growth rates in natural populations fluctuate over time and explaining why these changes occur.

　　[C] proposing a hypothesis concerning population size and suggesting ways to test it.

　　[D] posing a fundamental question about environmental factors in population growth and presenting some currently accepted answer.

　　2. It can be inferred from the text that the author considers the dichotomy discussed to be

　　[A] applicable only to erratically fluctuating populations.

　　[B] instrumental, but only if its limitations are recognized.

　　[C] dangerously misleading in most circumstances.

　　[D] a complete and sufficient way to account for observed phenomena.

　　3. According to the text, all of the following behaviors have been exhibited by different populations EXCEPT

　　[A] roughly constant population levels from year to year.

　　[B] regular cycles of increases and decreases in numbers.

　　[C] erratic increases in numbers correlated with the weather.

　　[D] unchecked increases in numbers over many generations.

　　4. The discussion concerning population in the third paragraph serves primarily to

　　[A] demonstrate the difficulties ecologists face in studying density-dependent factors limiting population growth.

　　[B] advocate more rigorous study of density-dependent factors in population growth.

　　[C] prove that the death rates of any population are never entirely density-independent.

　　[D] underline the importance of even small density-dependent factors in regulating long-term population densities.

　　5. In the text, the author does all of the following EXCEPT

　　[A] cite the views of other biologists.

　　[B] define a basic problem that the text addresses.

　　[C] present conceptual categories used by other biologists.

　　[D] describe the results of a particular study.

　　[答案与考点解析]

　　1. 【答案】A

　　【考点解析】这是一道中心主旨题。本文的中心主旨句在第三段的首句。如果考生能够抓住第三段的首句就等于抓住了整篇文章的论述结构。该句中的“dichotomy”(两分法) 就是正确选项A中的“two categories”。考生在解题时应首先抓住每篇文章的中心主旨句，因为这决定了对全文结构的认识以及对原文整体的把握。

　　2. 【答案】B

　　【考点解析】这是一道细节推导题。根据题干中的“dichotomy”可将本题的答案信息来源迅速确定在第二段的首句。如果考生能够正确理解该句中“but”一词前后的内容，就可以找出本题的正确选项B。考生在解题时一定要正确理解原文所传达的含义，即进行正确的细节推导。

　　3. 【答案】D

　　【考点解析】这是一道审题定位与中心主旨题。根据本题题干中的“different populations”可将本题的答案信息来源确定在首段的第一句，因为该句中的“all species”实际上指的就是题干中的“different populations”。从第一段的首句入手并且仔细阅读首段的第二句，就可以找出本题的正确选项D，因为该选项所传达的信息与原文第一段第一、二句所传达的信息不一致。考生在解题时一定要学会迅速审题定位的能力。

　　4. 【答案】D

　　【考点解析】本题是一道归纳推导题。题干已明确指出该题的答案信息来源在第三段。第三段主要陈述“density-dependent factors”的作用，通过仔细阅读第三段，尤其是第三段的最后三句话，考生可以得知本文作者在第三段是在强调“density-dependent factors”的作用。可见D是本题的正确选项。考生在理解原文时一定要注意掌握归纳推导的能力。

　　5. 【答案】D

　　【考点解析】本题是一道写作手法题。这是一道比较难的题目，旨在考察考生的语言功底。本文作者在论述自己的观点时运用了各种写作手段。选项A、B、C中所涉及的内容分别在第一段、第三段和第二段中出现。考生一定要提高对原文各种写作手段的认识。

　　[参考译文]

　　正如吉尔伯特·怀特、达尔文以及其它科学家很久以前观察的那样，所有的物种都具有一种天生的能力来一代一代地增加它们种群的数量。生态学家的使命就是调查清楚环境和生态因素长期以来是如何控制这种致使种群增长的内在能力的。由于不同种群所表现出来的动态行为是如此多样化，致使这项任务显得非常困难：有些种群长期以来大致保持不变;有些表现出周期性的繁荣和稀少;而还有些变化非常大，时而暴增，时而锐减，这种增减有时显然与气候有关，而有时又与气候无关。

　　为了赋予这些千变万化的模式一种规律，科学家中的一种流派提出将所有种群划分为两类。这部分生态学家假设：那些相对稳定的种群具有和“种群密度相关”的增长参数;也就是说，这些种群的出生率、死亡率以及迁徙规律都大大地依赖于种群的密度。那些变化很大的种群具有“种群密度无关”的增长参数，其生存率随环境因素的变化而变化，并且以一种完全独立于种群密度的方式进行波动。

　　这种二分法有它的用途，但如果死板地应用也会引发一些问题。一方面，没有任何种群在所有的时间里完全只受“种群密度无关”因素的影响。无论出生、死亡率以及迁徙规律相对于长期的平均值的变化是如何的剧烈和不可预测，如果没有种群密度无关因素，从长远来看，这个种群的数量将无限地增加或减少(从而阻碍了得失正好相消的奇迹的发生)。换一句话讲，也许种群内平均99%的死亡都由“种群密度无关”因素导致的，只有1%由随种群密度变化而变化的因素所导致。导致这1%的因素也许看起来并不重要，而且它们的影响也相应地很难确定。但是，无论认识到或没有认识到，它们都将对该种群密度长期的平均值起决定作用。

　　为了能够理解生态学家们研究的性质，我们可以把种群密度相关对增长参数的影响视为一种“信号”，生态学家试图分离并解释这些“信号”，这种“信号”将使种群中个体数量从相对低的数值增长或从相对高的数值减少，同时，密度无关因素将作为一种“噪音”来影响种群的动态变化。对于那些数量保持相对不变，或者以一种循环周期进行摆动的种群而言，这种“信号”将会相当容易提取特征并描述它的影响，即使我们仍不知道作为原因的生物机制。对那些变化不规则的种群，我们可能因为观察太小而无法从繁多的“噪音”中提取那一信号。但是，现在显得很清楚的是，所有种群都受“种群密度相关”和“种群密度无关”两类因素在不同程度上的共同制约。

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51楼发表于: 2016-08-12

只看该作者 ┊ 小中大

As Gilbert White, Darwin, and others observed long ago, all species appear to have the innate capacity to increase their numbers from generation to generation. The task for ecologists is to untangle the environmental and biological factors that hold this intrinsic capacity for population growth in check over the long run. The great variety of dynamic behaviors exhibited by different population makes this task more difficult: some populations remain roughly constant from year to year; others exhibit regular cycles of abundance and scarcity; still others vary wildly, with outbreaks and crashes that are in some cases plainly correlated with the weather, and in other cases not.

　　To impose some order on this kaleidoscope of patterns, one school of thought proposes dividing populations into two groups. These ecologists posit that the relatively steady populations have “density-dependent” growth parameters; that is, rates of birth, death, and migration which depend strongly on population density. The highly varying populations have “density-independent” growth parameters, with vital rates buffeted by environmental events; these rates fluctuate in a way that is wholly independent of population density.

　　This dichotomy has its uses, but it can cause problems if taken too literally. For one thing, no population can be driven entirely by density-independent factors all the time. No matter how severely or unpredictably birth, death, and migration rates may be fluctuating around their long-term averages, if there were no density-dependent effects, the population would, in the long run, either increase or decrease without bound (barring a miracle by which gains and losses canceled exactly). Put another way, it may be that on average 99 percent of all deaths in a population arise from density-independent causes, and only one percent from factors varying with density. The factors making up the one percent may seem unimportant, and their cause may be correspondingly hard to determine. Yet, whether recognized or not, they will usually determine the long-term average population density.

　　In order to understand the nature of the ecologist’s investigation, we may think of the density-dependent effects on growth parameters as the “signal” ecologists are trying to isolate and interpret, one that tends to make the population increase from relatively low values or decrease from relatively high ones, while the density-independent effects act to produce “noise” in the population dynamics. For populations that remain relatively constant, or that oscillate around repeated cycles, the signal can be fairly easily characterized and its effects described, even though the causative biological mechanism may remain unknown. For irregularly fluctuating populations, we are likely to have too few observations to have any hope of extracting the signal from the overwhelming noise. But it now seems clear that all populations are regulated by a mixture of density-dependent and density-independent effects in varying proportions.

　　1. The author of the text is primarily concerned with

　　[A] discussing two categories of factors that control population growth and assessing their relative importance.

　　[B] describing how growth rates in natural populations fluctuate over time and explaining why these changes occur.

　　[C] proposing a hypothesis concerning population size and suggesting ways to test it.

　　[D] posing a fundamental question about environmental factors in population growth and presenting some currently accepted answer.

　　2. It can be inferred from the text that the author considers the dichotomy discussed to be

　　[A] applicable only to erratically fluctuating populations.

　　[B] instrumental, but only if its limitations are recognized.

　　[C] dangerously misleading in most circumstances.

　　[D] a complete and sufficient way to account for observed phenomena.

　　3. According to the text, all of the following behaviors have been exhibited by different populations EXCEPT

　　[A] roughly constant population levels from year to year.

　　[B] regular cycles of increases and decreases in numbers.

　　[C] erratic increases in numbers correlated with the weather.

　　[D] unchecked increases in numbers over many generations.

　　4. The discussion concerning population in the third paragraph serves primarily to

　　[A] demonstrate the difficulties ecologists face in studying density-dependent factors limiting population growth.

　　[B] advocate more rigorous study of density-dependent factors in population growth.

　　[C] prove that the death rates of any population are never entirely density-independent.

　　[D] underline the importance of even small density-dependent factors in regulating long-term population densities.

　　5. In the text, the author does all of the following EXCEPT

　　[A] cite the views of other biologists.

　　[B] define a basic problem that the text addresses.

　　[C] present conceptual categories used by other biologists.

　　[D] describe the results of a particular study.

　　[答案与考点解析]

　　1. 【答案】A

　　【考点解析】这是一道中心主旨题。本文的中心主旨句在第三段的首句。如果考生能够抓住第三段的首句就等于抓住了整篇文章的论述结构。该句中的“dichotomy”(两分法) 就是正确选项A中的“two categories”。考生在解题时应首先抓住每篇文章的中心主旨句，因为这决定了对全文结构的认识以及对原文整体的把握。

　　2. 【答案】B

　　【考点解析】这是一道细节推导题。根据题干中的“dichotomy”可将本题的答案信息来源迅速确定在第二段的首句。如果考生能够正确理解该句中“but”一词前后的内容，就可以找出本题的正确选项B。考生在解题时一定要正确理解原文所传达的含义，即进行正确的细节推导。

　　3. 【答案】D

　　【考点解析】这是一道审题定位与中心主旨题。根据本题题干中的“different populations”可将本题的答案信息来源确定在首段的第一句，因为该句中的“all species”实际上指的就是题干中的“different populations”。从第一段的首句入手并且仔细阅读首段的第二句，就可以找出本题的正确选项D，因为该选项所传达的信息与原文第一段第一、二句所传达的信息不一致。考生在解题时一定要学会迅速审题定位的能力。

　　4. 【答案】D

　　【考点解析】本题是一道归纳推导题。题干已明确指出该题的答案信息来源在第三段。第三段主要陈述“density-dependent factors”的作用，通过仔细阅读第三段，尤其是第三段的最后三句话，考生可以得知本文作者在第三段是在强调“density-dependent factors”的作用。可见D是本题的正确选项。考生在理解原文时一定要注意掌握归纳推导的能力。

　　5. 【答案】D

　　【考点解析】本题是一道写作手法题。这是一道比较难的题目，旨在考察考生的语言功底。本文作者在论述自己的观点时运用了各种写作手段。选项A、B、C中所涉及的内容分别在第一段、第三段和第二段中出现。考生一定要提高对原文各种写作手段的认识。

　　[参考译文]

　　正如吉尔伯特·怀特、达尔文以及其它科学家很久以前观察的那样，所有的物种都具有一种天生的能力来一代一代地增加它们种群的数量。生态学家的使命就是调查清楚环境和生态因素长期以来是如何控制这种致使种群增长的内在能力的。由于不同种群所表现出来的动态行为是如此多样化，致使这项任务显得非常困难：有些种群长期以来大致保持不变;有些表现出周期性的繁荣和稀少;而还有些变化非常大，时而暴增，时而锐减，这种增减有时显然与气候有关，而有时又与气候无关。

　　为了赋予这些千变万化的模式一种规律，科学家中的一种流派提出将所有种群划分为两类。这部分生态学家假设：那些相对稳定的种群具有和“种群密度相关”的增长参数;也就是说，这些种群的出生率、死亡率以及迁徙规律都大大地依赖于种群的密度。那些变化很大的种群具有“种群密度无关”的增长参数，其生存率随环境因素的变化而变化，并且以一种完全独立于种群密度的方式进行波动。

　　这种二分法有它的用途，但如果死板地应用也会引发一些问题。一方面，没有任何种群在所有的时间里完全只受“种群密度无关”因素的影响。无论出生、死亡率以及迁徙规律相对于长期的平均值的变化是如何的剧烈和不可预测，如果没有种群密度无关因素，从长远来看，这个种群的数量将无限地增加或减少(从而阻碍了得失正好相消的奇迹的发生)。换一句话讲，也许种群内平均99%的死亡都由“种群密度无关”因素导致的，只有1%由随种群密度变化而变化的因素所导致。导致这1%的因素也许看起来并不重要，而且它们的影响也相应地很难确定。但是，无论认识到或没有认识到，它们都将对该种群密度长期的平均值起决定作用。

　　为了能够理解生态学家们研究的性质，我们可以把种群密度相关对增长参数的影响视为一种“信号”，生态学家试图分离并解释这些“信号”，这种“信号”将使种群中个体数量从相对低的数值增长或从相对高的数值减少，同时，密度无关因素将作为一种“噪音”来影响种群的动态变化。对于那些数量保持相对不变，或者以一种循环周期进行摆动的种群而言，这种“信号”将会相当容易提取特征并描述它的影响，即使我们仍不知道作为原因的生物机制。对那些变化不规则的种群，我们可能因为观察太小而无法从繁多的“噪音”中提取那一信号。但是，现在显得很清楚的是，所有种群都受“种群密度相关”和“种群密度无关”两类因素在不同程度上的共同制约。

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50楼发表于: 2016-08-12

只看该作者 ┊ 小中大

Until about five years ago, the very idea that peptide hormones might be made anywhere in the brain besides the hypothalamus was astounding. Peptide hormones, scientists thought, were made by endocrine glands and the hypothalamus was thought to be the brains’ only endocrine gland. What is more, because peptide hormones cannot cross the blood-brain barrier, researchers believed that they never got to any part of the brain other than the hypothalamus, where they were simply produced and then released into the bloodstream.

　　But these beliefs about peptide hormones were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present. The immunological method of detecting peptide hormones by means of antiserums, however, is imprecise. Cross-reactions are possible and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives. Furthermore, this method cannot be used to determine the location in the body where the detected substances are actually produced.

　　New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNA’s (c DNA’s) that can serve as molecular probes seek out the messenger RNA’s (mRNA’s) of the peptide hormones. If brain cells are making the hormones, the cells will contain these mRNA’s. If the products the brain cells make resemble the hormones but are not identical to them, then the c DNA’s should still bind to these mRNA’s, but should not bind as tightly as they would to m RNA’s for the true hormones. The cells containing these mRNA’s can then be isolated and their mRNA’s decoded to determine just what their protein products are and how closely the products resemble the true peptide hormones.

　　The molecular approach to detecting peptide hormones using cDNA probes should also be much faster than the immunological method because it can take years of tedious purifications to isolate peptide hormones and then develop antiserums to them. Roberts, expressing the sentiment of many researchers, states: “I was trained as an endocrinologist. But it became clear to me that the field of endocrinology needed molecular biology input. The process of grinding out protein purifications is just too slow.”

　　If, as the initial tests with cDNA probes suggest, peptide hormones really are made in brain in areas other than the hypothalamus, a theory must be developed that explains their function in the brain. Some have suggested that the hormones are all growth regulators, but Rosen’s work on rat brains indicates that this cannot be true. A number of other researchers propose that they might be used for intercellular communication in the brain.

　　1. Which of the following titles best summarizes the text?

　　[A] Is Molecular Biology the Key to Understanding Intercellular Communication in the Brain?

　　[B] Molecular Biology: Can Researchers Exploit Its Techniques to Synthesize Peptide Hormones?

　　[C] The Advantages and Disadvantages of the Immunological Approach to Detecting Peptide Hormones.

　　[D] Peptide Hormones: How Scientists Are Attempting to Solve Problems of Their Detection and to Understand Their Function?

　　2. The text suggests that a substance detected in the brain by use of antiserums to peptide hormones may

　　[A] have been stored in the brain for a long period of time.

　　[B] play no role in the functioning of the brain.

　　[C] have been produced in some part of the body other than the brain.

　　[D] have escaped detection by molecular methods.

　　3. According to the text, confirmation of the belief that peptide hormones are created in the brain in areas other than the hypothalamus would force scientists to

　　[A] reject the theory that peptide hormones are made by endocrine glands.

　　[B] revise their beliefs about the ability of antiserums to detect peptide hormones.

　　[C] invent techniques that would allow them to locate accurately brain cells that produce peptide hormones.

　　[D] develop a theory that account for the role played by peptide hormones in the brain.

　　4. Which of the following is mentioned in the text as a drawback of the immunological method of detecting peptide hormones?

　　[A] It cannot be used to detect the presence of growth regulators in the brain.

　　[B] It cannot distinguish between the peptide hormones and substances that are very similar to them.

　　[C] It uses antiserums that are unable to cross the blood-brain barrier.

　　[D] It involves a purification process that requires extensive training in endocrinology.

　　5. The idea that the field of endocrinology can gain from developments in molecular biology is regarded by Roberts with

　　[A] incredulity.

　　[B] derision.

　　[C] indifference.

　　[D] enthusiasm.

　　[答案与考点解析]

　　1. 【答案】D

　　【考点解析】这是一道中心主旨题。全文从头至尾讨论的是“peptide hormones”在人体内产生的部位，所以有关全文中心主旨内容的答案应该包含“peptide hormones”。从各段的主题句进行分析，第一至四段主要讲如何“detect”(探测)肽激素(peptide hormones)所产生的位置，第五段主要讲有关肽激素的“function”。可见本题的正确选项应该是D。考生在解题时一定要搞清楚原文所涉及的对象并且抓住每段的主题句以及它们之间的相互关系。

　　2. 【答案】C

　　【考点解析】这是一道审题定位题。根据题干中的“a substance detected”可把本题的正确选项迅速确定在第二段的尾句。该句所涉及的核心问题是“where”，所以本题的正确选项应该是C。考生在解题时一定要迅速而准确地进行审题定位。

　　3. 【答案】D

　　【考点解析】本题是一道细节推导题。通过本题题干中的“peptide hormones are created in the brain in areas other than the hypothalamus”可将本题的答案信息来源迅速确定在尾段的第一句。尾段第一句主要就肽激素的“function”进行论述，可见本题的正确选项应该是D，选项D中的“role”就等于原文中的“function”。考生在解题时一定要善于抓住主句中的重要信息。

　　4. 【答案】B

　　【考点解析】这是一道句间关系题。根据本题题干中的“the immunological method”可将本题的答案信息来源迅速确定在第二段的第二句，而本题的确切答题点在第二段的第三句的后半部分。从第二段第三句的后半部分可以推导出本题的正确答案是B。考生在解题时一定要注意一般概括句和具体陈述句之间的相互关系。

　　5. 【答案】D

　　【考点解析】本题是一道细节推导题。根据本题题干中的人名“Roberts”可将本题的答案迅速确定在倒数第二段引号部分的第二句话，即“But”一词引导的句子。从该句中的“needed”一词可以看出本题的正确选项应该是D。考生在解题时一定要学会深入理解原文的字面含义。

　　[参考译文]

　　肽激素除了下丘脑能制造，在大脑中任何其它的地方都能够制造。大约五年前仅这一想法本身就是令人惊诧的。科学家认为，肽激素是由内分泌腺制造的，而下丘脑被认为是大脑中唯一的内分泌腺。而且，由于肽激素无法穿过血脑障碍，研究人员认为它们从不曾到过除下丘脑以外的大脑任何其它部位，肽激素仅在下丘脑制造出来，然后被释放到血管中。

　　但是关于肽激素的这种观点已经遭到质疑。通过一次又一次的实验发现，肽激素的抗血清一旦被注射到大脑中，它就会在下丘脑以外的地方粘接起来。这就说明这些地方或是有肽激素存在，或是有与抗血清发生交叉反应的其他物质存在。但是，通过抗血清来检验肽激素的免疫学方法是不精确的。交叉反应可能会发生，而且以这种手段无法确认用抗血清检测的特质确实是肽激素还是仅是与其近似的亲缘物质。另外，这种方法不能用来确定被测物质在人体内产生的部位。

　　然而，分子生物学的新技术为解决这些问题提供了一个新途径。科学家可以制造出一种特别的互补DNA’S (cDNA’s)，作为分子探子查找出肽激素的信使RNA’S (mRNA’s)。如果脑细胞正在制造肽激素，那么它应该包含这些信使RNA’S。如果脑细胞制造的产品与肽激素相似但并不完全相同，那么这些互补cDAN’S仍然会和这些信使mRNA’S粘结，但不会象和真正肽激素的信使mRNA’S结合得那么紧密，这些包含信使mRNA’S的细胞能被分开。研究者可以将信使mRNA’S解码以确定其蛋白质产品究竟是什么及这些产品在多大程度上类似于真正的肽激素。

　　采用cDAN探子这一分子生物学方法检测肽激素同时也比免疫学方法快得多，因为如果用免疫学方法，分离肽激素需要几年枯燥乏味的提纯过程，然后还需培养出他们的抗血清。罗伯茨的一番话表达了许多研究人员的心声，他说：“我是作为一名内分泌学家接受训练的，但情况对我来说很清楚，内分泌学领域需要分子生物学的输入，靠碾磨来制造蛋白质纯化物的过程实在是太慢了。”

　　如果正如用cDNA探子所做的最初测试表明的那样，肽激素确实是由大脑中下丘脑以外的部位制造出来的，则有必要建立一套理论来解释它们在大脑中的作用。某些学者指出肽激素是生长调节剂，但罗森对老鼠大脑所作的实验表明事实并非如此。很多其它的研究人员指出肽激素或许被用于大脑内细胞与细胞间的信息传输。

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