现在完成时一、现在完成时构成构成：现在完成时由助动词have + 过去分词构成，助动词have 有人称和数的变化。
第三人称单数用has，其余用have.现在完成时的否定式直接在助动词后面加上not、疑问式是把助动词提到主语之前。
以study 为例，其否定式、疑问式和简单回答形式如下：1、现在完成时通常表示在说话之前已经完成的动作或存在的状态。
说话人强调的是该动作或状态对现在的结果或影响。
My daughter has just gone out. 我女儿刚出去。
I’m sure we’ve met before. 我肯定我们以前见过面。
She has arrived. 她到了。
2、表示持续到现在的动作或状态，往往和包括现在在内的表示一段时间的状语连用，如recently, already, just, lately, for…, since…,yet等。
如：I haven’t heard from her these days. 这些日子我没有收到她的信。
We haven’t seen you recently. 最近我们没有见到你。
They have been away for two years. 他们离开已经两年了。
She has been with us since Monday.①for+时段②since+过去一个时间点（译为：自从……以来）③since+时段+ago④since+从句（过去时）⑤It is+时段+since+从句（过去时）Mary has been ill for three days.I have lived here since 1998.注意：since和for的区别since后接时间点，如1993，last term, yesterday, the time I got therefor后接一段时间，表示“长达多久”，如ten years, a while, two days等。
3、表示短暂意义的动词如arrive, leave, borrow, buy, begin, start, die等，在完成时当中不能和表示一段时间的状语连用，因为它们表示的动作不可能持续。
因此，不能说：He has come here for 2 weeks. ×The old man has died for 4 months. ×They have left only for 5 minutes. ×4、has gone (to),has been (to), has been (in) 的区别Have/Has gone(to) :去了(现在不在说话现场，可能在路上和已经到)Where is your father?He has gone to Shanghai.Have/Has been (to) :去过（已不在去过的地方）My father has been to Shanghai.Have/has been in：呆了多久（还在所呆的地方）My father has been in Shanghai for two months. /since two months ago.5、现在完成时不能和表示过去的时间状语连用，如yesterday, last year, in 1976, two days ago, just now, when I came in，但可以和already, yet, sometimes, always, often, before, lately, recently, once, twice, ever, never等连用。
不能与when连用。
现在完成时往往同表示不确定的过去时间状语连用例如：She has already come. 她已经来了。
I haven’t read it yet. 我还没读过这个。
I have met him before. 我从前曾见过他。
Ma Hong has always been a good student. 马红一直是个好学生。
I have often seen him in the street. 我经常在街上看见他。
They have never been to Yan’an. 他们从未去过延安。
I haven't seen him lately. 我近来没看到他。
三、现在完成时的标志1、现在完成时的含义之一是过去完成的动作对现在仍有影响,用以下四大标志词可以表达这种含义:* 以already, just和yet为标志He has already got her help.他已得到她的帮助。
He has just seen the film.他刚刚看过这场电影。
He hasn't come back yet.他还没有回来。
* 以ever和never为标志This is the best film I have ever seen.这是我曾经看过的最好的一部电影。
He has never been to Beijing.他从没有到过北京。
* 以动作发生的次数为标志He says he has been to the USA three times. 他说他已经去过美国三次了。
* 以so far（到目前为止）为标+beforeHe has got to Beijing so far.到目前为止他已到了北京。
She has passed the exam so far.到目前为止她已经通过了考试。
2.过去已经开始的动作一直延续到现在, 甚至有可能继续延续下去,我们可以从动作“延续”的特性和“时间”点段的区分入手,进一步学习现在完成时。
①for+时段②since+过去一个时间点（过去从句）为标志四、瞬间动词buy, die, join, come，go ,leave, join ……不能直接与for since 连用。
要改变动词buy----have borrow -----keepcome/arrive/reach/get to-----be ingo out----be out leave ----be awaybegin-----be on finish----be overopen----be open close -----be closeddie----be dead1、have代替buyMy brother has had(不能用has bought) this bike for almost four years.2、用keep或have代替borrowI have kept(不能用have borrowed) the book for quite a few days.3、用be替代becomeHow long has your sister been a teacher?4、用have a cold代替catch a coldTom has had a cold since the day before yesterday.5、用wear代替put on6、用“be＋形容词”代终止性动词be＋married代marry be＋ill代fall (get) illbe＋dead代die be＋asleep代fall (get) asleepbe＋awake代wake/wake up be＋gone代lose,die,sell,leavebe＋open代open be closed代close/shutbe＋missing(gone,lost)代lose7、用“be＋副词”代终止性动词be＋on代start begin “be＋up”代get up“be＋back(to)”代return to, come back to, go back to“be here (there)”代come(arrive, reach, get) here或go (arrive, reach, get) there 8、用“be＋介词短语”代终止性动词1.“be in/at +地点”代替go to /come to2.用be in the army 代替join the army3.“be in/at +地点”代替move to常用瞬间动词变延续性动词表：1. have arrived at/in sw. got to/reached sw. come/gone/moved to sw.→have been in sw./at…相应的介词2. have come/gone back/retu rned → have been back3. have come/gone out →have been out4. have become → have been5. have closed / opened→ have been close/open6. have got up → have been up；7. have died → have been dead；8. have left sw. → have been away from sw.9. have fallen asle ep/got to sleep → have been asleep；10. have finished/ended/completed → have been over；11. have married → have been married；12. have started/begun to do sth. → have done sth.；13. have begun → have been on14. have borrowed/bought →have kept/had15. hav e lost → haven’t had16. have put on →have worn17. have caught /get a cold → have had a cold；18. have got to know → have known19. have/has gone to → have been in20. have joined/have taken part in the league/the Party/the army→have been a member of/ hav e been in/have been the Party’s member/the league member/the soldier…。