当虚拟条件句的谓语部分含有were, should, had时，我们可以将连词if省略掉，而将were, should, had置于句首。如：

If she were in charge, she would do things differently.=Were she in charge, she would do things differently. 如果是她负责，她会是另一种做法。

If you should change your mind, no one would blame you.=Should you change your mind, no one would blame you.万一你改变主意，谁也不会怨你。

If the management had acted sooner, the strike wouldn’t have happened.= Had the management acted sooner, the strike wouldn’t have happened. 如果资方早些采取行动，就不会发生罢工了。

几点说明：

1. 对于条件从句含有should而主句使用陈述语气或祈使语气的句子也可以采用以上方法进行省略和倒装。如：

If I should be free tomorrow, I will come. = Should I be free tomorrow, I will come. 如果明天我有空我就来。

If they should attack us, we’ll wipe them out completely.=Should they attack us, we’ll wipe them out completely. 假如他们进攻我们，我们就把他们彻底消灭干净。

有时被提到句首的had不是助动词，而是表示“有”的实义动词。如：

Had I the time, I would go. 如有时间我就去。

2. 如果条件从句为否定式，注意要将not置于主语之后，而不置于主语之前。如：

若非你的帮助，我仍会无家可归。

误：Weren’t it for your help, I would still be homeless.

正：Were it not for your help, I would still be homeless.

要不是我亲眼所见，我都不会相信了。

误：Hadn’t I seen it with my own eyes, I would not have believed it.

正：Had I not seen it with my own eyes, I would not have believed it.

3. 在这类倒装结构中，置于句首的were习惯上不能用was代替。如：

如果我是在你的立场，我不愿意做那件事。

If I were in your place, I wouldn’t do that.

→Were I in your place, I wouldn’t do that.

引用地址: http://www.yygrammar.com/Article/201205/2942.html