一.现在完成时的构成:现在完成时由助动词 have(has)+动词的过去分词构成has用于第三人称单数,have用于其他各种人称. 二.现在完成时的用法:其用法主要有三种 I.“已完成”用法 :表示一个过去发生并结束的动作对现在造成的影响或结果这一类情况可以细致分为下述两种情况 1）表示开始于过去的动作刚刚结束常和just，now，already，yet，not…yet等不确定的时间状语连用 Li Ming has just turned off the light. 李明刚刚把灯关上说明现在灯关上了） I've finished my homework now. 现在我已经做完作业了说明可以交作业或做别的了） 2）表示过去动作的结果，现在仍残留着一般不用时间状语 I have lost my pen. 我把笔丢了 （说明过去某时丢的，现在我还没找到这支笔）She has become a teacher. 她已经当了老师说明她现在仍是老师） II.“未完成”用法表示动作或状态从过去某时开始，持续到现在，可能继续下去，也可能刚刚结束常和表示一段时间的状语连用如today，this week（month），lately，recently，these days，in the past few days，during the last two weeks，since，since yesterday，since 2 days ago，since 1991，for a long time，for a month，so far，up to now，till（until） now等。
He has lived here for 30 years. 他住在这儿三十年了现在还住在这儿） They've known each other since childhood. 他们从小彼此相识现在还在往来） How long have you studied English？ 你学英语多久了？（现在仍在学） III.经验性用法:表示从过去开始到目前为止这段时间中反复发生的动作或多次出现的状态常与频度副词如often,always,every week,twice等连用I have been to the Summer Palace twice. 我曾经去过颐和园两次 He has always said so.他总是这么说.三.现在完成时的时间状语 I现在完成时属于现在时范围，故不能和过去的时间状语连用如：yesterday,last Sunday,in1990,three years ago等但是，在强调动作产生的后果和影响时，可以和一些表示不确定的时间状语连用a. 用副词already和yetalready一般用于肯定句中，yet一般用于否定句和疑问句中如：We have already finished our homework.我们已完成作业了。
They haven't finished their homework yet.他们还没有完成作业b. 用ever和never.多用于否定或疑问句中，表示“曾经”或“从未“等如： -Have you ever been to the Great Wall?你曾经去过长城吗?-I have never been to the Great Wall.我从未去过长城 c. 用表示到说话为止的过去时间状语，如just, before, up to now, the past few years等例如：I have seen her before,but I can not remember where. 我以前见过她，但记不起在哪里见过 He has been there three times the last few days. 近几天他去过那里三次了 d. 用包括“现在”在内的时间状语，如now,today,this morning(month,year,term)等例如：-Have you met him today?-No,I haven't. 今天你见过他吗？我没有。
How many times have you been there this year? 今年你去过那里多少次？ II短暂性动词不能和表一段时间的时间状语连用如：come, go, arrive, reach, hear, close, leave, begin, start, lose, buy, fall, join, die, get up等但如果要保留表一段时间的时间状语，必须将动词改为延续性动词现归纳总结一下由非延续性动词到延续性动词的转换如： fall asleep (ill) →be asleep (ill) get to know→ know begin,(start)→ be on open →be open buy→ have get up→ be up die→ be dead go out→ be out come→ be in close→be closed arrive→be here join→be in, be a +名词 finish( end )→be over leave, move →be away, borrow →keep go to school→be a student catch(a cold)→ have(a cold) begin to study→study come back→be back put on→wear 或be on 如：He has been a soldier for three years.他参军三年了。
His father has been dead for two years.他父亲去世二年了 The film has been on for 5 minutes.电影已开始五分钟了 We have studied English for three years. 我们（开始）学英语已三年了 四.几点注意事项 I. have been(to)与have gone( to)的区别：have been(to)表示“去过某地（现在已经回来了）”，可用于各人称；have gone(to)表示“去某地了（说话时某人不在当地）”，常用于第三人称，前者可与once ,never,several times等连用，后者则不能如： They have been to Beijing twice.他们去过北京两次 He has gone to Beijing . 他去北京了 II.不可延续性动词现在完成时的否定式，已变成一种可以延续的状态，因此可以和表示一段时间的状语连用如： I haven't left here since 1997.自从1997年以来，我一直没有离开过这儿。
（错）I have received his letter for a month. （对）I haven't received his letter for almost a month. 练习一.用since和for填空1.______two years 2.____two years ago3.___last month 4.______ 19995._______yesterday 6._______ 4 o’clock7 4 hours 8._____an hour ago9.___we were children 10._____ lunch time11.____ she left here12. He has lived in Nanjing ___ the year before last.13. I’ve known him ______ we were children.14. Our teacher has studied Japanese ______ three years.15. She has been away from the city ______ about ten years.16. It’s about ten years __________ she left the city.二.单项选择。
1、Both his parents look sad . Maybe they ______what's happened to him . A. knew B. have known C. must know D.will know2、He has _______ been to Shanghai , has he ?A. already B.never C.ever D.still3、Have you met Mr Li ______？ A. yesterday B. ago C.before D. a moment ago4、The famous writer _____ one new book in the past two years . A. is writing B.was writing C.wrote D.has written5、—Our country ______ a lot so far . —Yes . I hope it will be even ______ . A.has changed ; well B.changed ; good C.has changed ; better D.changed ; better 6、Zhao Lan ______already ______in this school for two years . A. was ; studying B. will ; study C. has ; studied D. are ; studying 7、We ______ Xiao Li since she was a little girl . A. know B. had known C. have known D. knew8、Harry Potter is a very nice film .I______ it twice .A.will see B.have seen C.saw D.see。