Question

英语语法中的虚拟语气，怎么用呢？

能否简单一点给我个提示？谢谢

Answer 1

Subjunctive Mood (虚拟语气)

从句 主句
现在时间 陈述语气 does shall/will do
虚拟语气 did should/would do
过去时间 陈述语气 did should/ would do
虚拟语气 had done should/would have done
将来时间 陈述语气 does, am/is/are to do shall/will do
虚拟语气 should do, were to do should/would do

Wish虚拟句
现在式→过去式， 过去式→过去完成式
＊ 如果wish是过去式，虚拟从句无时态变化。
＊ wish cf· hope wish引导的从句表示愿望实现的可能性很小
hope 引导的从句表示愿望有可能实现

动词 advise, agree, appoint, arrange, argue, ask, command, decide, decree, demand, desire, determine, direct, expect, insist, intend, order, permit, persist, propose, prefer, pray, provide, recommend, request, require, suggest, urge等之后加(should) do.
动词变成过去式，从句无时态变化。
上述动词转化成名词后，引导的从句也加(should) do
eg. I suggest that a meeting (should) be held as soon as possible.
My suggestion is that a meeting (should) be held as soon as possible.
I suggested that a meeting (should) be held as soon as possible.

It is + 下述形容词+ that+ （should） do
advisable, appropriate, better, desirable, essential. Good, imperative, important, necessary, proper, right, urgent, vital
eg. It is essential that everyone (should) bear this in mind.

It is + 下述形容词+ that+ should do
absurd, amazing, annoying, awkward, funny, natural, odd, pitiful, a pity, regrettable, to be regretted, ridiculous, strange, surprising.
＊ should 不能省略

if only + 虚拟式

would rather/sooner + that + 虚拟式
＊ would rather/sooner + (to) do
eg. I would rather you came tomorrow.
I would rather wait.

It is (high) time + that + did

lest, for fear that, in case + should do

But for…, 虚拟句
But that…, 虚拟句
With/ without…, 虚拟句

公式化的虚拟句
God bless you.
Long live China.
Suffice to say that we won.
May you live a long and happy life!
Come what may, we will go ahead with our plan.
Heaven forbid that I should let my own parents suffer.

条件句中的were, had, should 等助动词移到句首，省略if, 构成倒装虚拟条件句。
Eg. If he had come earlier, he would not miss the bus.
Had he come earlier, he would not miss the bus.

Answer 2

去这里看 讲的很详细
http://baike.baidu.com/view/26751.htm

Answer 3

虚拟语气中有一种叫着虚拟条件句(或叫着含蓄条件句)，而非真实条件句中的条件从句有时不表达出来，只暗含在副词、介词短语、上下文或其他方式表示出来，这种句子叫做含蓄条件句，在多数情况下，条件会暗含在短语中，如without…，but
for…，in
the
absence
of···，otherwise等。这些句子中的结构一般如下:
主句:主语+should/would/could/might+do/have
done。
从句，but
that/otherwise
+
主语
+
过去时态
eg:
But
for
his
help,we
would
be
working
now.
要不是他的帮助，我们还会在工作呢。
Without
your
instruction,I
would
not
have
made
such
great
progress.
要是没有你的指导，我不会取得如此大的进步。
We
didn't
know
his
telephone
number,otherwise
we
would
have
telephoned
him.
我们不知道他的电话号码，否则我们就会给他打电话。
in
the
absence
of
sunlight,
there
would
be
no
moonlight.
如果没有太阳光，就不会月光。
but表示让步关系，意思是“除非，要不是”，常与that一起构成but
that,
相当于"if...not"。
例如:I
would
have
failed
but
that
your
helped
me.要不是你们帮助我，我就会失败。
其他不懂的给我留言吧，这个我擅长。