考博英语语法的掌握是英语科目复习的重中之重，英语阅读、写作等题型都需要良好的语法基础能力作为支撑，以下系列考博英语语法知识总结请作参考。
考博英语语法知识汇总 (1)
虚拟语气重点知识：
1.一些常见的虚拟语气的句型或结构。
2.虚拟语气的特殊形式，即用来表示要求、建议、命令、提议、意愿等的主语从句、宾语从句、表语从句和同位语从句中的虚拟形式。
3.主从句表示不同的时间概念、事实或假设情况，从而交错成为复合虚拟语气。
4.含蓄条件句中的虚拟语气的表示愿望的虚拟形式。
上述四个要点往往在完形填空或者阅读理解里面存在，尤其是每年完形填空都至少有一道直接考这方面的知识的题目，而在阅读理解里，我们掌握上述四个重点对于我们理解文章的大意和作者态度很有帮助，了解哪些观点是作者假设的、虚拟的，哪些是真实的，这样对于我们回答关于作者态度观点题很有帮助。
下面我们将主要从上述四个方面来重点论述在考试中应该注意的问题。
一、虚拟语气的常见类型和句型
(1)由wish引起的表示愿望的虚拟语气
A.用wish表示对现在的愿望时，它所引起的宾语从句中谓语动词形式为：过去式(be动词用were)。
B.用wish表示对将来的愿望时，它所引起的宾语从句中谓语动词形式为：would, could, might+ 动词原形。
C.wish用于对过去的事实表示一种不可能实现的愿望时，宾语从句中的谓语动词形式为：had+动词过去分词或could, would + have +动词过去分词。
The picture exhibition bored me to death; I wish I had not gone to it.
---“I let Joe borrow our radio for the afternoon.”
---“That’s all right, but I wish he would buy one of his own.”
I wish that he weren’t so lazy.
(2)had hoped引起的宾语从句中备用语动词形式为would+动词原形，表示一种过去未实现的愿望或令人失望的事。
His father had hoped that his son would go to business with him, but his son became an artist later.
(3)would (had) rather, would as soon, would sooner和would prefer所引起的从句中要求用过去式表示当时或将来的情况，用过去完成时表示过去的情况，表示希望或婉转的责备。例如：
I’d rather you posted the letter right away. 我倒希望你把这封信立刻寄出去。
I would prefer he didn’t stay there too long.我倒希望他不要在那儿可得太久。
I would just as soon you had returned the book yesterday.我真希望你昨天把这本书还了。
(4)It’s (high, about) time that 句型中that从句中要求用虚拟语气形式，即动词要用过去式。
It’s time that something was done about the traffic problem downtown.
It is high time that we put an end to this discussion.现在是我们该结束讲座的时候了。
(5)as, 或者whether…or…谓语多用be的原形，引导让步虚拟从句，这种用法通常采用倒装结构：
Church as we use the word refers to all religious institutions, be they Christian, Islamivc, Buddhist, Jewish, and so on.
The business of each day, be it selling goods or shipping them, went quite smoothly.
(6)由连接词in case, so that ,unless, lest ,for fear that引起的状语从句中，谓语动词要用虚拟形式，即should(might, would)+动词原形，例如：
She put a blanket over the baby for fear that he should catch cold. 她在那个婴儿身上盖上了毯子以免他着凉。
The bad man was put in the soft-padded cell lest he injure himself.
(7) if it were not for…与现在事实相反， if it had not been for与过去事实相反，两个都相当于but for：
If it had not been for his help(=but for his help),we would not have succeeded.
(8) 虚拟语气用于as if(though)引起的方式状语从句和表语从句中，其动词形式与wish宾语从句的形式相同。例如：She often laughs spontaneously, and her good humor breaks out as brightly as if it were a part of the sunshine above.她常常发出发自内心的微笑，而且她那美好的情绪像天上一道明亮的阳光一样，常常流露出来。
They talked as if they had been friends for years.他们交谈着，就好像他们是我年的老朋友一样。
She looks as if she would cry.她看起来好像要哭了。
(9)其它各种句型, as though, suppose, had rather, supposing, if only等等
If I were in a movie, then it would be about time that I buried my head in my hands for a cry.