一．现在完成时:
1.用法：
(1)表示过去发生或已经完成的动作对现在造成的影响或产生的结果；
e.g. I have already finished my homework.
She has already read this book.
Mary and Tom have finished their lunch.
(2)也表示过去发生的动作从过去一致延续到现在，也可能是将来。此用法常与延续性动词连用。
e.g. I have studied English for three years.
She has lived here for eight years.
Tom has worked there since 1998.
They have been here since they graduated.
2.常与现在完成时搭配的时间状语：
(1)yet还（用于否定句和疑问句）;
(2)already早已，已经（用于肯定句）;
(3)for +一段时间（a year, three months, etc.）;
(4)since +表示过去的时间点;
(5)so far到目前为止；
(6)ever曾经；
(7)in the past few years（months, days, etc.）；
(8)up to now直到现在；
(9)before以前;
(10)by +现在的时间点，意为“截至……时”;
(11)by the end of +现在的时间点，意为“截至……时”;
(12)over +时间段,意为“在……期间”
e.g. I haven’t had lunch yet.
Mary has already read this book.
3.形式: have/has（助动词） + done（动词的过去分词）
4.主谓一致：
(1)have:当主语为：I, you和复数主语时使用；
(2)has:当主语为第三人称单数（he, she, Mary, etc.）时使用.
5.动词过去分词的转变规则：
(1)规则变化：和动词过去式的变法一致；
(2)不规则变化：特殊记忆（有些相同，有些不同）。
6. 现在完成时中肯定句，否定句及一般疑问句的相互转化以及疑问句的肯定和否定回答（模仿含有助动词的句子）。
e.g.(1)肯定句： I have read the book.
否定句：I haven’t read the book.
一般疑问句：Have you read the book?
肯定回答：Yes, I have.
否定回答：No. I haven’t.
(2)肯定句：She has finished lunch
否定句：She hasn’t finished lunch.
一般疑问句：Has she finished lunch?
肯定回答：Yes, she has.
否定回答：No. she hasn’t.
7.现在完成时常与since +句子连用，since从句用一般过去时，主句用现在完成时：
e.g. I have studied Japanese since I graduated from university.
She has worked here since she came Shanghai.
8. have/has been (to)与have/has gone(to)的区别:
(1) has/have been (to)意为“到过某地”，说话时此人已经不再那个地方，可能已经回来，强调经历；
(2)has/have gone(to)意为“已经去了某地”，说话时此人已经不再这里，很可能已经到达那个地方或是在路上。
e.g. He has been to Beijing.
He has gone to Beijing.
Where has Tom been?
Where has Tom gone?
9.瞬间动词与延续性动词:
(1)瞬间性动词指不能够持续的动词，如go, come, arrive, die等，不能与一段时间连用。
(2)延续性动词表示可以持续的动词，如stay, live, wait等。
e.g. She has gone to Shanghai.
I have lived in the place for three years.
10.现在完成时与一般过去时的区:
(1)一般过去时只表示过去的动作，现在完成时强调过去的动作对现在造成的影响或产生的结果；
e.g. I read the book last year.
I have read the book.
(2)现在完成时的动作开始于过去而且现在还在继续，而一般过去时的动作早已结束；e.g. He has worked in this company for
three years.
He has worked in this company for three
years.
(3)现在完成时表示动作发生在过去一个不确定的时间，常与already, yet, never, before等连用；一般过去时表示在过去某个确定的时间发生，常与过去具体的时间连用。
e.g. I have already read the book.
I lived in the countryside three years ago.
(4)用how long来询问for +一段时间或since +过去的时间点，而且这三个词必须与延续性动词连用。
e.g. ①How long have you had that bike over there?
I’ve had it for three years.
②How long has his son owned the train and railway set?
He’s owned it since his fourth birthday.
11. 动词过去式（过去分词）的转化:
(1)规则动词的转化规则：
①一般情况下直接加ed；
e.g. look----looked
play----played
start----started
②以e结尾的动词加d；
e.g. live----lived
hope----hoped
use----used
face----faced
③以重读闭音节结尾的，末尾只有一个辅音字母的，双写这个辅音字母，再加ed；
e.g. stop----stopped
plan----planned
permit----permitted
beg----begged
④以辅音字母加y结尾的动词，变y为i再加ed。
e.g. study----studied
carry----carried
worry----worried
(2)不规则动词的变化规则，需特殊记忆：
①原形，过去式和过去分词形式相同：
e.g. hit----hit----hit
set----set----set
put----put----put
cut----cut----cut
cast----cast----cast
cost----cost----cost
shut----shut----shut
hurt----hurt----hurt
burst----burst----burst
spread----spread----spread
②过去式和过去分词同形：
e.g. feed----fed----fed
bleed----bled----bled
bend----bent----bent
buy----bought----bought
breed----bred----bred
fight----fought----fought
bring----brought----brought
catch----caught----caught
sell----sold----sold
leave----left----left
meet----met----met
send----sent----sent
find----found----found
sleep----slept----slept
teach---taught----taught
think----thought----thought
③原形，过去式和过去分词均不相同：
e.g. lie----lay----lain
see----saw----seen
rise----rose----risen
give----gave----given
begin----began----begun
blow----blew----blown
二 习题专练：......