2.2 如何使语义连贯
科技论文是一个语义连贯的文章，构成文章的句子之间必然存在某种逻辑上的联系，语句的衔接和连贯是语句成篇的重要保证。实现衔接与连贯主要有以下几种方式。
2.2.1 使用连接词语
英语中使用连接词将句子衔接起来，以达到意义连贯。句子之间缺乏必要的衔接手段，就显得非常松散。例如：
①Gold, a precious metal, is prized for important characteristics.②Gold has a lustrous（有光泽的）beauty that is resistant to corrosion.③It is suitable for jewelry, coins and ornamental（装饰性的） purposes.④Gold never needs to be polished, and will remain beautiful forever.⑤A Macedonian（马其顿的） coin remains as untarnished（失去了光泽的）today as the day it was minted（铸造）twenty-three centuries ago.⑥Important characteristics of gold is its usefulness to industry and science.⑦It has been used in hundreds of industrial applications.⑧The most recent use of gold is in astronauts’ suits. Astronauts wear goldplated heat shields for protection outside the spaceship.⑨Gold is treasured for its beauty, for its utility.
将该段落修改后如下：
①Gold, a precious metal, is prized for two important characteristics.②First of all, gold has a lustrous beauty that is resistant to corrosion.③Therefore, it is suitable for jewelry, coins and ornamental purposes.④Gold never needs to be polished, and will remain beautiful forever.⑤For example, a Macedonian coin remains as untarnished today as the day it was minted twenty-three centuries ago.⑥Another important characteristics of gold is its usefulness to industry and science.⑦For many years, it has been used in hundreds of industrial applications.⑧The most recent use of gold is in astronauts’ suits. Astronauts wear goldplated heat shields for protection outside the spaceship.⑨In conclusion, gold is treasured for its beauty, for its utility.
在添加了必要的衔接词后，段落变得流畅连贯了。 请再看一例：
①Lasers have found widespread application in medicine. ②For example, they play an important role in the treatment of eye disease and the prevention of blindness. ③The eye is ideally suited for laser surgery because most of the eye tissue is transparent. ④Because of this transparency, the frequency and focus of the laser beam can be adjusted according to the absorption of the tissue so that the beam “cuts” inside the eye with minimal damage to the surrounding tissue—even the tissue between the laser and the incision（切口）. ⑤Lasers are also more effective than other methods in
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treating some causes of blindness. ⑥However, the interaction between laser light and eye tissue is not fully understood.
从以上两段的分析可以看出，连接词的使用在保证语句连贯方面起着举足轻重的作用。
科技论文中常用的连接词可大致分为以下7类，表示不同类型的句间关系： （1）表示时间和顺序关系：after，before，first，second，then，next，finally，later，meanwhile（其间），in the past等。
（2）表示空间关系：here，there，nearby，under，below，in front of，in the middle of，at the back of等。
（3）表示附加、递增关系：and，also，again，in addition，besides，furthermore（此外，而且），moreover，what is more（更甚者）等。
（4）表示异同关系：however，nevertheless，but，although，yet，while，on the contrary，in spite of，instead，but，unlike，similarly，likewise，in the same way，like等。
（5）表示因果关系：since，because，as，result from，due to，thanks to（由于），for this reason，therefore，consequently，accordingly，thus等。
（6）表示列举：for example，for instance，such as，namely（即，也就是），in other words，that is to say等。
（7）表示总结：in conclusion，to sum up，in short，in a word，in brief，on the whole等。
2.2.2 重复关键词以求衔接和连贯
关键词是在科技论文中表达内容的重要概念，可能会在论文中反复提及，重复关键词可以使语句衔接紧密。例如：
The CPU memory unit is commonly called the internal memory of a computing system, on older machines this memory usually consisted of magnetic cores… Most computing systems also incorporate components that serve as auxiliary or external memory.
在上例中memory这一关键词重复4次，既使语句意义连贯，又有效地突出了主题。
2.2.3 用主从结构达到连贯
在论文中，句与句之间表达的意义关系并不是平行和并重的，有时它们之间有主次、轻重之分，有的表示背景与主题之间的关系，有的表示条件与结果的关系。在写作时，要用主从复合结构将这种意义的层次体现出来，否则，就影响意义的连贯。例如：
Some materials are liable to absorb moisture. This will adversely affect their insulating（绝缘） properties.
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上例中的两个句子意义相关联。但是，由两个单独的句子表达，结构有些松散，所以将两句合并，由主从复合结构表达。这样意义更加连贯，例如：
Some materials are liable to absorb moisture, which will adversely affect their insulating properties. 2.2.4 应避免的错误
书写时要使句子保持连贯，避免犯下列错误。 （1）误置修饰语的错误
修饰语（即定语或状语）应靠近所修饰的词。如果远离所修饰的词就成为误置修饰语，可能会影响到句子的连贯性。
例1：The engineering student made a big mess wearing the red hat. (错误) The engineering student wearing the red hat made a big mess. （正确） 注意修饰性从句同被修饰成分保持明显的关系。
例2：She borrowed a car from her friend that was bad. (意义不清楚) From her friend, she borrowed a car that was bad.
要避免不一致的修饰语。不一致的修饰语是模棱两可的，既可修饰这个词又可以修饰那个词，使读者茫然。
例3：His doctor told him frequently to exercise. (模棱两可) His doctor frequently told him to exercise. （正确） His doctor told him to exercise frequently. （正确） （2）平行结构错误
平行结构就是句中表达同样意思的并列的两部分或更多的部分以同样的语法形式连贯地表现出来。换句话说，就是主语和主语、谓语动词和谓语动词、宾语和宾语、补足语和补足语平行，或名词与名词、形容词与形容词、副词与副词、从句与从句等平行。平行结构一般由相关连词and，or，either…or…，neither…nor…，not only…but also…等引导。当并列部分的语法形式不同时，就出现了平行结构错误。
例4：To design a device and making it are two different jobs. （错误） Designing a device and making it are two different jobs. （正确） 例5：Galileo found it difficult to believe that the sun rotates around the earth and the earth to be the centre of the universe. （错误）
Gelileo found it difficult to believe that the sun rotates around the earth and that the earth is the centre of the universe. （正确）
（3）模糊指代错误
模糊指代错误是指代词可指代两个不同的先行词。为了消除模糊指代可用名词来代替代词或阐明先行词。
例6：Our responsibility in the laboratory was to remove the labels from the dishes and wash them. (误)
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Our responsibility in the laboratory was to remove the labels from the dishes and wash the dishes. (正确)
（4）泛指代的错误
泛指代中的先行词是一个泛泛的概念，是整个意思而不是一个特定的名词或名词结构。当代词指代两个以上的意思时，就会出现泛指代错误。This，that和which的含糊使用常导致这种错误。
例7：He spent his time getting help with his income tax forms, which his wife considered unfair.（错误）
His wife considered it unfair that he spent his time getting help with his income tax forms. (正确)
2.3 英语科技论文常用句型结构
在写英语科技论文时，作者有必要熟悉和掌握一些重要的常用句型，进行记忆和模仿，这对提高英语论文的语言质量非常有帮助。下面按论文语言所表达的功能分类列出。
（1）定义
定义是对一事物的本质特征或一个概念的内涵和外延的确切而简要的说明，常见的表达方式和句型有：
means...??signifies...??The term macromolecule ?is considered to be...
?is taken to be...?refers to ...?
In this article?will be taken to mean...?will be used in the ...??will be considered to be ...? ?will refer to...?????????In this paper??In this essay?? network In this context?In computer science???For this purpose?例：Paradigm（范例）refers to models of inquiry that guides scientific work. （2）分类
在科技论文中，作者有时需要对描述、说明的对象按其性质、大小、作用等分成若干种类，然后依次阐述。常见的表达分类的句型有：
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