我们都知道SCI论文写作是有章法可循的，掌握好这几个要素，可以让你更加得心应手：标题、章节标题、专业术语、主动被动语态、时态、参考文献等。
从今天起，笔者就给大家分享以上要素的SCI写作经验，以期能够助力您的SCI论文写作水平的提升。本期，笔者主要给大家总结SCI论文的时态、主动语态和被动语态，并结合具体的例句。
本文主要包括6个内容：
1、时态
2、被动语态与主动语态
3、什么时候使用被动语态?
4、什么时候应该避免被动语态?
5、你可以使用被动，也可以使用主动
6、学习一些在方法部分之外介绍主动语态的基本技巧
SCI论文中最常见的两种时态是现在时态和过去时态。将来完成时和现在完成时远远排在第三位和第四位。
- 当你阐述一个现象或概念时，使用现在时态，例句：Turtles are bigger than beetles.
- 当你描述你或别人所做的事情时，使用过去时态，例句：Darwin observed the difference in adaptability between turtles and beetles.
- 当你陈述将来计划时，请使用将来时态，例句：In my final project, I will compare survival strategies in turtles and beetles. 注意，论文中可以使用第一人称单数。
- 当你描述过去重复做过的事情并一直持续到现在时，使用现在完成时，例句：Over the past several months I have collected data on turtles and beetles.
- 注意，我们可以在一个句子中混合使用不同的时态，例句：Darwin observed that beetles are more adaptable than turtles.
- 用过去时来描述别人的工作是自然科学和人文社科论文的一个关键区别。在人文社科论文中，当我们陈述作家、艺术家或学者的观点时，我们认为自己参与了一场发生在永恒当下的对话，例句：Shakespeare compares the poet’s lover to a summer’s day.
- 在人文社科论文中，强调过去的时候需要使用过去时态，例句：Shakespeare wrote many of his tragedies during a period of great political instability.
在人文社科论文中，应该尽可能使用主动语态。自然科学论文经常鼓励使用被动语态，被动语态有助于强调科学的客观性，例句：The element radon was discovered in 1900.
一些简单的主动语态句型，可以帮助你的写作。例如，在句首而不是句末引用图表、表格和方程式。例句：Figure 1 illustrates the quadratic relationship between distance and velocity.
对于“结果”、“研究”和“证据”等单词和短语也要这样做，例句：Experimental evidence shows that the typical dose-response curve has an inverted J-shape.
如果你介绍一种技巧或程序，通过主动语句来达到更直接的效果，例句：PCR analysis produced clones of the toxin B DNA originally isolated in cultures of C. difficile from hospital patients.
请注意，自然科学论文允许使用第一人称 “我”和“我们”。在某些学科中，有些专家仍然坚持在使用被动语态(过去时态)：换句话说，他们不接受任何主动结构，即使你避免使用“我”和“我们”。
在一些句子中，被动语态是完全可以接受的。你可以在以下情况下使用它:
- 行动者未知，例句：The cave paintings of Lascaux were made in the Upper Old Stone Age. [读者不知道是谁画的壁画]
- 行动者无关紧要，例句：An experimental solar power plant will be built in the Australian desert. [我们不关心谁建立它]
- 故意含糊不清，例句：Mistakes were made. [官僚写作中常见]
- 阐述一个普遍真理，例句：Rules are made to be broken. [任何人，无论何时]
- 你想要强调被行动的人或事，例句：Insulin was first discovered in 1921 by researchers at the University of Toronto. It is still the only treatment available for diabetes.
被动句在SCI写作中会给你带来麻烦，因为它们模糊地说明了行为人，例句：Both Othello and Iago desire Desdemona. She is courted. [谁追求Desdemona? 是Othello? 是Iago?还是他们两人?]SCI写作通常关注不同研究人员观点的差异，或者你自己的观点和你所讨论的研究人员的观点的差异，使用太多的被动句会造成混乱，例句：Research has been done to discredit this theory. [谁做了这项研究?你吗?你的教授吗?另一个作者吗?]使用被动句可以隐藏他们研究中的漏洞，例句：The telephone was invented in the nineteenth century. [读者无法知道谁发明了电话!]最后，被动句听起来比较啰嗦和间接。由于被动句通常比主动句要长，所以它们在你的论文中占据了宝贵的空间，例句：Since the car was being driven by Michael at the time of the accident, the damages should be paid for by him.让我们比较一下来自同一期《分子生物学》的两篇文章，都是用被动语态写的。第一个是引言:More than 50 LRRK2 mutations are known now. All of the mutations (mostly, missense mutations) were found in heterozygote, segregated with the disease and were not detected in a control sample. In addition, LRRK2 mutations were not detected in other neurological disorders. Autosomal dominant PD was demonstrated to result not only from the most common G2019S mutation, but also from at least five other mutations.这里的问题是，读者无法从句子本身知道谁对每个发现负责。是同一个人还是不同的人?他们的专业是什么?他们使用了什么技术手段来实现他们的成果?所有这些都还很模糊。相比之下，在Methods部分，使用被动语态要更加清晰.Nucleotide sequences were analyzed using the Staden 1.53 software package. Alignment was performed using the ClustalW program provided in the MEGA package v.5. The number of haplotypes (h), haplotype (Hd), and nucleotide (π) diversity were evaluated using DnaSP 5.10 program.Nambu et al. have reported a theoretical study of wake formation in the presence of a magnetic field parallel and perpendicular to the ion flow direction. (Introduction, European Physics Journal)在你的文献综述中，你可以对不同来源的结果进行归类，同时使句子传达有用信息:. . . while a large body of literature has explored large-scale geographical patterns, and several recent papers have studied disease dynamics in a metapopulation framework, few empirical studies have focused on the patterns and mechanisms behind disease clusters at small spatial scales (“disease foci”), especially in wild host–pathogen systems. (Introduction, Ecology)你也可以使用你自己报告的各个部分或图表作为句子的主语:The results of this study showed that severe hypothermia did not develop in either group. (Discussion, Journal of Obstetric, Gynecologic, & Neonatal Nursing)Table 1 shows the frequencies of the study design criteria of included studies by sponsorship source. (Results, PLOS Biology)
