as（SCI论文写作:如何正确使用“As”）

在科学写作中，下列哪个句子是正确的?

As the participants discussed the problem they noted new terms and concepts.As the participants discussed the problem they were familiar with the main issues.As postgraduates all the participants said they now regularly use social media.As undergraduates the participants had all opened social media accounts.

这四个句子都可以表达清楚。首先，“as”可以是一个从属连词，但它有多重含义，所以最好重写一个句子以免读者误解。

句子（1）是正确的，在该从句中的“as”指的是在某一过程或事件发生的同时或期间。一些作者不使用逗号，但是可以添加逗号以区分介绍性短语和从属子句，进而帮助读者理解：“As the participants discussed the problem, they noted new terms and concepts.”然而，“as”也有because的意思，所以这个句子可以重写以避免误解：“While the participants discussed the problem, they noted new terms and concepts.”

句子（2）有歧义。如果"as"的意思是because，那么为了提及一个之前的事件作为理由，第一个子句的时态应该为过去完成时：“Because the participants had discussed the problem, they were familiar with the main issues.” 如果“as”的意思是while，那么第二个子句需要修改成可以一个表示正在进行的过程：“While the participants discussed the problem, they became familiar with the main issues.”

其次，“as”也可以是介词，放在名词前用来说明一个身份或目的，但它既有when/while的意思，也有because的意思。句子（3）中给出了一个理由，所以使用一个介绍性的从属子句这句话更加清晰：“Because they were postgraduates, all the participants said they now regularly use social media.”

句子（4）有歧义，这句话的意思可能是：“When/While they were undergraduates, the participants had all opened social media accounts”【参与者不再是本科生，这句话说的是开通社交账户的时间】，或者意思是：“Because they were undergraduates, the participants had all opened social media accounts.”【参与者是本科生，这说明了账户存在的理由】。