The tendency of using present tense，especially present simple tense is used in scientific English to denote“permanence” ，“universality”or“truism”in the description of natural occurrence，processes or general laws，so the tense is generally timeless．

One of the most striking characteristics of modern science has been the increasing trend toward closer cooperation between scientists and scientific institutions all over the world．

　现代科学最显著的特点之一，就是全世界科学家及科学机构之间不断发展更密切的合作的趋势。

Comments The original sentence is in present perfect progressive tense to denote a trend which started in the past and which will continue into the future．

2)Frequent use of passive voice

A．Passive voice can highlight the object of description or discussion without any reference to human agent，which is characteristic of scientific language．

All business decisions must be made in the light of the market．

　所有企业都必须根据市场来做出决策。

Comments It is neither possible nor necessary to specify who make these“business decisions”in the SL sentence．In the TL sentence，we can use企业as the subject of the sentence according to Chinese linguistic habits．

No work can be done without energy．

　没有能量就不能做功。

Comments The original sentence is in passive voice since it describes a universal truth without any involvement of human agents．In the translation，we can convert the SL sentence into a subjectless sentence that frequently occurs in Chinese．

B．Passive voice can avoid subjectivity and achieve objectivity which is a prominent feature of scientific language．

All sorts of necessities of life can be made of plastics．

　各种日常用品都能用塑料制造。

Comments The use of passive voice helps to achieve objectivity in the original sentence．

An example is given to…/A discussion is presented to…

　本文举例(说明……)/本文讨论了……

Comments The original sentence typically occurs in the abstract of a scientific paper．Passive voice is used here to avoid such expressions as “The author gives an example of…”which has a little bit subjectivity．But equivalent Chinese versions本文举例(说明……)/本文讨论了…… are normally adopted in such text type．

C．Passive voice is used to serve the purpose of concision and economy．

D．Passive voice is sometimes used for smooth cohesion of discourse．

When the radiation energy of the sun falls on the earth，it is changed into heat energy to warm the earth．

　当太阳的辐射能到地球时就转化为热能，从而使大地暖和起来。

Comments The use of passive voice in the main clause enhances its cohesion with the subordinate clause“When the radiation energy…”

3)Frequent use of nominal structures

In scientific writings，a noun phrase is often used in place of a sentence．Such noun phrases are known as nominal structures．They are clear，concise，compact and information intensive in place of long clauses and sentences．

The discovery of the constant speed of light regardless of the motion of its source by Einstein threw some interesting light on the study of theoretical physics．

　爱因斯坦发现:无论光源是否运动，光的速度都恒定不变，这一发现给理论物理的研究带来了发人深省的启迪。

Comments The underlined part of the sentence is a typical nominal construction．It is equivalent to a long sentence meaning“Einstein discovered that the speed of light is constant，no matter how fast its source is moving” ．

The testing of machines by this method entails some loss of power．

　用这种方法试验机器，会浪费一些能量。

Comments“The testing of machines by this method”in the original sentence is equivalent to an adverbial clause of condition“If machines are tested by this method” ．

Continued exposure of the eye to light of high intensity would cause loss of sight．

　眼睛持续暴露在强光中会导致失明。

Comments : “Continued exposure of the eye to light of high intensity”in the original sentence is equivalent to an adverbial clause of condition “If the eye is continuously exposed to light of high intensity” ．

4)Ellipsis，inversions and separations often used

This phenomenon is due to the rhetorical and stylistic need in scientific English．Ellipsis can achieve concision and brevity．Inversions can foreground a certain element．Separations make a sentence well-balanced and symmetrical．

All bodies consist of molecules and molecules of atoms．

　所有的物体都由分子组成，而分子又由原子组成。

Comments The underlined part of the sentence is an ellipsis．Its complete form should be“all molecules consist of atoms” ．

All these forces the platform must be able to withstand without changing its operating characteristics．

　平台必须能承受所有这些力，而其作用性能不得有所改变。

Comments This is a typical inverted sentence．Its normal order should be“The platform must be able to withstand all these forces without changing its operating characteristics” ．This sentence is inverted in order to highlight“All these forces” ．

The distance to the sun，from where we are on the earth，is about 1 million walking days．

　假如从地球步行到太阳，约需一百万天。

Comments In this sentence ，“the distance”is separated from“from where we are on the earth”to keep the sentence well-balanced and to avoid ambiguity．The normal order of the sentence should be“The distance from where we are on the earth to the sun is…”

5)Frequent use of long and complicated sentences

Such long sentences usually consist of a variety of clauses，phrases and other subordinate constituents．Such a sentential structure is intended to express the different logical relationships between the things that are described in the paper explicitly and precisely．Now let us look at the following sentence．

Only by studying such cases of human intelligence with all the details and by comparing the results of exact investigation with the solutions of AI(Artificial Intelligence)usually given in the elementary books on computer science can a computer engineer acquire a thorough understanding of theory and method in AI，develop intelligent computer programs that work in a humanlike way，and apply them to solving more complex and difficult problems that present computer can＇t．

　只有很详细地研究这些人类智能的情况，并把实际研究得出的结果与计算机科学基础论著上所提出的人工智能解决方案相比较，计算机工程师才能彻底地了解人工智能的理论和方法，开发出具有人类智能的计算机程序，并将其用于解决目前计算机不能解决的更为复杂和困难的问题。

Comments The original long sentence is in inverted order．The general structure of this sentence is“Only by doing…and by doing…can a computer engineer…”There are three coordinate predicates in this sentence : “acquire…” ，“develop…”and“apply…”But there are also two attributive clauses : “that work in a humanlike way”and“that present computer can＇t” ，and a past participle phrase“given in the elementary books on computer science”and several prepositional phrases that are also modifiers．This is characteristic of English sentential structure that is hypotactic in nature．Since Chinese sentences are mostly paratactic in contrast to English sentences，in translating long sentences，we often need to break them up into short parts and convert them into correspondent short Chinese clauses．

6．2. 2 Syntactical Characteristics句法特点

6．2. 2　Syntactical Characteristics句法特点