as soon as, hardly/scarcely…when, no sooner…than用法区别
as soon as,
hardly/scarcely…when…
no sooner…than…
这三个短语都有“一……就”、“刚刚……就”的意思，它们的意思非常相近，因此有时可以互换。例如：
“我刚到公共汽车站，汽车就开了。”一句，就可以有如下几句译法：
As soon as I got to the bus stop, the bus started.
Hardly/scarcely had I got to the bus stop when the bus started.
No sooner had I got to the bus stop than the bus started.
但他们之间也有一些差异，例如，如果从两件事情的间隔时间来说，as soon as 较长，han 居中，when 间隔时间最短。其它的一些区别见下面，请大家在运用的时候要留意。
1、A（主句） as soon as B（从句）
它的意思相当于“从句B一发生以后，主句A就发生”。
发生顺序B在A之前。这个短语用的比较常用，口语和书面语都可以。它的特点是，在句子中的位置比较灵活，而且可以用于各种时态。例如：
I’ll write you as soon as I get there.
我一到那儿就给你来信。（一般现在时）
As soon as I went in, Katherine cried out with pleasure.
我一进门，Katherine 就高兴的叫起来。（一般过去时）
I’ll return the book as soon as I have read it.
我一读完就把书还回去。（现在完成时）
Andrew left as soon as he had drunk his coffee.
Andrew一喝完咖啡就走了。（过去完成时）
2、no sooner A（主句）…than B（从句）
它的意思相当于“主句A一发生，从句B就发生”。
发生顺序A在B之前。例如：
He had no sooner returned than he bought a hou.
他一回来就买了一套房子。
如果no sooner 位于句首，主句要用倒装结构。例如：
No sooner had he arrived than he went away again.
他刚到就又走了。
No sooner had the game started than it began to rain heavily.
运动会刚开始，天就下起了大雨。
有一点要注意，no sooner…than 一般用来描述做过的事情，它不能用于表示将来的事。
Andrew left as soon as he had drunk his coffee.
= No sooner had Andrew drunk his coffee than he left.
Andrew一喝完咖啡就走了。（过去完成时）
No sooner was the frost off the ground than the work began.
=The work began as soon as the frost off the ground.
地上的霜一消散，人们就开始工作了.
3、hardly/scarcely A（主句部分倒装）…when/before B（从句）
它的意思是“几乎未来得及做完A这件事，紧接着就开始B这件事。”
使用这个短语时，一般用于过去完成时；并且when有时可改用before。例如：
He had hardly/scarcely finished the article when the light went out.
他刚写完文，灯就熄了。
He had hardly/scarcely had time to ttle down when he sold the hou.
他还未安顿下来，就卖掉了那所房子。
另外，如果把hardly/scarcely放于句首，主句要用部分倒装结构即谓语动词要提前。如：
Hardly/scarcely had I finished eating when he came in.
我刚吃完他就进来了。
Hardly/scarcely had she gone out when a student came to visit her.
她还没走出家门，就有一个学生来看望她。
as soon as=the instant (when)= instantly=the moment (that)=immediately after=directly after=right after
B（主句）（一般过去） as soon as A（从句）（过完） “equals to”
= no sooner A（主句部分倒装）（过完）…than B（从句）（一般过去）
= hardly/scarcely A（主句部分倒装）（过完）…when/before B（从句）（一般过去）
下面几个个句子说明关系:
Hardly had the thief en the policeman when he ran away.
= Scarcely had the thief en the policeman before/when he ran away. =No sooner had the thief en the policeman than he ran away.
=As soon as the thief saw the policeman, he ran away.
=Upon eing the policeman, the thief ran away. <upon=on>
