If he had been here yesterday,the experiment would have been successful.
问题描述：
If he had been here yesterday,the experiment would have been successful.
If you had taken your medicine yesterday,you would be better today.
同样是虚拟语气,这两句话前半句都是过去完成时,为什么后半句一个是过去完成时,一个是一般过去时?
答
前半句都是讲过去的事.用had+过去分词.
例1的后半句也是讲过去的事.也用had+过去分词.译成：
如果他昨天在这儿,（昨天）这个实验就会成功了.
例2的后半句讲现在的事.用would+动词原形.译成：
如果你昨天服了药,你今天就会好些了.