一、基本结构：主语+have/has+过去分词(done)
①肯定句：主语+have/has+过去分词+其他
②否定句：主语+have/has+not+过去分词+其他
③一般疑问句：Have/Has+主语+过去分词+其他
④特殊疑问句：特殊疑问词+一般疑问句（have/has+主语+过去分词+其他）
二、用法
1） 现在完成时的"完成用法"
现在完成时用来表示现在之前已发生过或完成的动作或状态,但其结果却和现在有联系,也就是说,动作或状态发生在过去但它的影响现在还存在.
He has turned off the light.他已把灯关了。(动作结束于过去，但说明的是现在的情况--灯现在不亮了。)
I have spent all of my money.(含义是:现在我没有钱花了.)
Jane has laid the table.(含义是:现在桌子已经摆好了.)
2） 现在完成时的"未完成用法"
指的是动作开始于过去某一时刻，一直延续到现在，或可能还要继续下去。这里的动词要用持续性动词。常与for（+时间段）,since（+时间点）连用.
Mary has been ill for three days.
Mary has been ill since three days ago.
注意:1.现在完成时不能单独与准确时间连用，(如表示过去的时间状语）
如yesterday(morning、afternoon),last(morning、afternoon)等，除非与for, since连用.
2.现在完成时往往同表示不确定的过去时间状语连用
,如already（肯定）, yet（否定，疑问）, just, before, recently, still, lately等:
He has already obtained a scholarship.
I haven't seen much of him recently (lately).
We have seen that film before.
Have they found the missing child yet ?
3. 现在完成时常常与表示频度的时间状语连用,
如ever, never, twice, several times等:
Have you ever been to Beijing
I have never heard Bunny say anything against her.