1. 现在完成时的定义
现在完成时通常是指过去某一动作对现在的影响或过去某一动作持续到现在（可能要继续下去）
2. 现在完成时的构成
现在完成时是由“助动词have/has+过去分词”构成的
3. 现在完成时的基本句型

4. 现在完成时的基本用法
a. 现在完成时可表示过去发生的动作对现在所产生的影响，后面通常不用时间状语，但句中常出现already, just, yet等副词。如：
Someone has broken the window.

有人把窗户打破了。
I’ve just finished reading the novel.

我刚刚读完这本小说。
Have you seen the doctor yet?

你看过医生了吗？
注：already和yet用法上的区别
already常用于肯定句，置于句中。yet常用于否定句和疑问句，常用于句末。但already有时也可用语疑问句中暗示惊讶的心情。如：
b. 现在完成时也可表示从过去某时开始的动作，状态一直持续到现在，常和for, since引导的时间状语连用。如：
I have learned English for 5 years.
He lived in Beijing since he was born.
注：(1) for和since引导的时间状语的区别: for + 一段时间, since + 一点时间 从句（从句中常用一般过去时）
(2)表示继续的现在完成时也可和lately, recently, so far, up to now, till now, in the past(last) few years……, this week (month, year……), all day, all this week等时间状语连用。如：
Tom has had a toothache all day.
I haven’t heard from him recently.
(3)现在完成时也可表示从过去到现在曾经经历过或做过的事情，常和often, ever, never, before, once, …times等时间状语连用。如：
I’ve never been to Beijing.我从没去过北京。
He has read this book before.他以前读过这本书。

1. 现在完成时和一般过去时的区别
(1)两者都可表示过去发生过的动作，但前者表示的是过去的动作对现在的影响，而后者则是表示过去动作的事实。
(2)两者都可表示过去开始并延续了一段时间的动作，现在完成时含义为该动作仍在继续，而一般过去时则说明该动作现已终止。如：
He has lived in Beijing for four years.他在北京住了四年了。（动作仍在继续）
He lived in Beijing for four years.他在北京住了四年。（动作已结束）
2. 点动词与延续性动词的区别
    所谓点动词是指含有终止或短暂意义的动词。如：begin, end, die, buy, borrow, come, arrive, join, marry等动词。它们通常不与表示一段时间的状语连用。如：
I have bought a book.我买了一本书。
I’ve had this book for three weeks.这本书我已经买了三星期了。
    某些非延续性动词可以与since连用，表示重复的动作或状态。如：
I have met her often since I moved here.
They have gone fishing five times since last spring.
    有些非延续性动词现在完成时在否定结构中可以与since或for短语连用。如：
He has never touched beer for a whole week.
I haven't bought anything for a year.
3. has been to和has gone to的区别
has been to表示“曾经去过”说明所提及的对象一回到说话地点
has gone to表示“去……”说明所提及的对象不在说话地点。如：
I’ve been to Beijing for many times.我到过北京很多次了。
Tom has gone to Beijing and will come back next week.汤姆已到北京去了，下星期才回来。
4. have got的含义
have got形式上是现在完成时，却和have是同一个意思
She has got a slight temperature. She has a slight temperature.她有点发烧。
Have you got a new dictionary?  Do you have a new dictionary?你有一本新字典吗？
5. 注意下面各句的意思：
He has gone for two days. 他走了，将离开两天。= He has gone and will be away for two days.
She has come for a week. 她来了，要呆一个星期。= She has come and will stay here for a week.
I haven't heard from her since she lived in Nanjing. 自从她离开南京以来，我一直没有她的音信。

1.You won’t know if it fits you until you ___ it on.
  A. will try B. are trying C. try D. have tried
2.It’s said that he ___ sent to Australia to improve his English.
  A. would be B. was to be C. has been D. had been
3.This is the second time you ___ late this week.
  A. had arrived B. arrived C. have arrived D. arrive
4.The living standard of the people in Nanjing ___ since1983.
  A. has raised B. had been risen C. has risen D. rose
5.Mr. Smith has lived in Canada for twelve years, so he ___ life there.
  A. used to B. get used to C. got used to D. has got used to
6.Mike ___ with Jane for one year.
  A. has been in love B. has fallen in love C. has been loved D. has loved
7. Tom was said to ___ Mary for 40 years.
  A. have been married to B. have married with C. have been married with    D. had married with
8.Great changes ___ in the city, and a lot of factories ___.
  A. have been taken place, have been set up B. have taken place, have been set up
  C. have taken place, have set up                 D. were taken place, were set up
9.Robert is said ___ abroad, but I don’t know what country he studied in.
  A. to have studied B. to study C. to be studying D. to have been studying
10.The price ___, but I doubt whether it will remain so.
  A. went down B. will go down C. has gone down D. was going down