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考研英語作文美文范例指南

　　考生們在考研英語的復(fù)習(xí)期間，要找到英語作文的寫作方法，可以參考一些美文范例。小編為大家精心準(zhǔn)備了考研英語作文美文參考資料，歡迎大家前來閱讀。

考研英語作文美文范例指南

　　考研英語作文美文范例：鹽與新陳代謝

　　Just how salt became so crucial to our metabolism is a mystery; one appealing theory traces our dependence on it to the chemist ry of the late Cambrian seas. It was there, a half billion years ago, that tiny metazoan organisms first evolved systems for sequestering and circulating fluids. The water of the early oceans might thus have become the chemical prototype

　　for the fluids of all animal life - the medium in which cellular operations could continue no matter how the external environment changed. This speculation is based on the fact that, even today, the blood serums of radically divergent species are remarkably similar. Lizards, platypuses, sheep, and humans could hardly be more different in anatomy or eating habits, yet the salt content in the fluid surrounding their blood cells is virtually identical. As early marine specics made their way to fresh water and eventually to dry land, sodium remained a key ingredient of their interior, if not their exterior,milieu. The most successful mammalian species would have been those that developed efficient hormonal systems for maintaining the needed sodium concentrations. The human body, for example, uses the hormones renin, angiotensin, and aldosterone to retain or release tissue fluids and blood plasma. The result, under favorable conditions, is a dynamic equilibrium in which neither fluid volume nor sodium concentration fluctuates too dramatically. But if the body is deprived of salt, the effects soon become dangerous, despite compensatory mechanisms.

　　全文翻譯：鹽與新陳代謝鹽為何成為人類新陳代謝的關(guān)鍵是一個謎;一個富有吸引力的理論認(rèn)為我們對鹽的依賴可從寒武紀(jì)海洋的化學(xué)變化中得到線索。五億年前，就是在那里，微小的后生動物首先進(jìn)化成與外隔絕的循環(huán)液體系統(tǒng)。因此，早期海洋里的水可能是所有動物體內(nèi)液體的化學(xué)原型--一個無論外界環(huán)境如何改變，其細(xì)胞活動仍將繼續(xù)的環(huán)境。這個設(shè)想是建立這一事實基礎(chǔ)上：即使是在今天，物種迥異的'眾多動物血清非常相似。蜥蜴、鴨嘴獸、綿羊和人類，在解剖學(xué)和飲食習(xí)慣上完全不同，但細(xì)胞周圍的液體中的鹽含量卻基本上是相等的。在海洋生物向淡水區(qū)域并最終向陸地移動的過程中，鹽始終是它們生存環(huán)境--如果不是外部環(huán) 境，其碼也是內(nèi)部環(huán)境中的關(guān)鍵成份。最高級的哺乳類動物為保持所需的鹽濃度而進(jìn)化出了高效的內(nèi)分泌系統(tǒng)。例如，人體為了保留或釋放組織液體和血漿而使用高血壓蛋白原酶、血管緊張素、醛固酮等激素。這樣在有利的環(huán)境下，液體與其中鹽濃度之間形成的動態(tài)平衡，兩者均不致出現(xiàn)大起大落。但如果身體里喪失了的鹽分，盡管有各種的補償機制，后果將馬上極其危險。

　　考研英語作文美文范例：油和水

　　To understand the emulsifying process, we must first accept the scientific principle that oil and water do not naturally mix. Quite literally, they find each other's presence repulsive. A good illustration of this aversion is homemade oil and vinegar salad dressing.When you shake or beat your salad dressing, you do more than disperse the oil throughout the vinegar: you also break down the oil into droplets minute enough to remain temporarily suspended in the vinegar (which from now on we will call water, because that tart condiment is in effect mainly water). The second you stop agitating the dressing, the oil droplets start to combine into units too large to be suspended in the water, and thus slither their way upward, separating from the water in the process. The oil rises to the top and the water sinks because oil has a lower specific density than water. If you want a stable emulsion, you need an emulsifying agent which prevents the oil droplets from combining into larger units. Emulsifying agents occur naturally in many animal substances including egg yolks and milk. An emulsifying agent helps to keep the oil particles from combining in three basic ways. First, the agent coats the oil, serving as a physical barrier between the droplets. Second, it reduces the water's surface tension, which, in turn, reduces the water's ability to repulse oil. Third, the agent gives the surfaces of the oil droplets identical electrical charges; since like charges repel each other the

　　droplets repel each other.

　　全文翻譯：油和水為理解乳化過程的發(fā)生，我們必須首先認(rèn)識到這樣一條科學(xué)原理：水和油不能自然混合，它們實實在在互相排斥。家制的油醋沙拉調(diào)料就是一個好例子。當(dāng)你攪拌沙拉調(diào) 料時，你不僅使油擴(kuò)散到醋里，而且使油滴被攪得很小可以懸浮在醋中(自此我們改稱它為水，因為事實上這種酸性調(diào)味品的主要成份就是水)。一旦你停止了攪動，油滴就會凝聚，大到再也不能懸浮在水中時，它們就向上滑動出來而與水分離了。因為油的密度小，所以油會浮在水上。如果想得到穩(wěn)定的乳化，就需要一種乳化劑。它可以不讓油形成大的油滴。自然界中，很多動物體中含有乳化劑，如蛋黃和牛奶。乳化劑可以從以下三方面阻止油滴凝聚。一、乳化劑包裹住油滴，在油滴間形成一道物質(zhì)屏障。二、乳化劑降低水的表面張力，從而降低了水排斥油的能力。三、乳化劑使油滴表面帶上了同種電荷，因為同種電荷互相排斥，油滴之間也相互排斥。