概念：1) 表示过去发生或已完成的某个动作对现在产生的影响或结果，强调的是这个影响或结果，常同already, just, yet等状语连用；2)表示开始于过去、持续到现在的动作或状态，并可能继续下去（也可能不继续下去），常同包括现在在内的时间状语连用，如：today, now, this week, this morning, these days, this afternoon, recently, so far等；3) 表示从过去某一时间到说话时这段时间中反**生的动作或多次动作的总和，常同频度副词always, often, seldom, never等连用。
一、 构成方式构成：
、主语（第。
一、二人称单复数）＋h**e
、主语（第三人称复数）＋h**e
、主语（第三人称单数）＋has ＋过去分词
二、 基本用法
1) 表示过去发生或已完成的某个动作对现在产生的影响或结果，强调的是这个影响或结果，常同already, just, yet等状语连用例：i h**e just turned off the light. 我刚刚把灯关上。
（结果是灯已经关上了）
she has lost her bike. 她把自行车丢了。（影响是他现在没有自行车骑了）
the rain has stopped now. 雨已经停了。（结果是我们可以出门了）
i h**e already read the book. 我已读过这本书了。（结果是已知道这本书的内容）
she has had a good education. 她受到过良好的教育。（影响是她文化水平高，有修养）
2) 表示开始于过去、持续到现在的动作或状态，并可能继续下去（也可能不继续下去），常同包括现在在内的时间状语连用，如：today, now, this week, this morning, these days, this afternoon, recently, so far等；也同“for+时间段”或 “since＋时间点”的状语连用例： she has taught in the school for ten years.
她在这所学校教书已经10年了。
i h**en't eaten anything since breakfast. 我从早饭起就一直没有吃东西。
we h**e been busy this morning.今天上午我们一直很忙。i h**e known her since we were children.
我从小就认识她。
i h**en't seen john today. 我今天没有见到约翰。 it has rained a lot these days. 这些天多雨。
3) 表示从过去某一时间到说话时这段时间中反**生的动作或多次动作的总和，常同频度副词always, often, seldom, never等连用例：he has done a lot of work in the past two years. 在过去两年中他做了许多工作。
i h**e learned about two hundred english words this month. 本月我学了大约200个英语单词。
i h**e been to the great wall twice. 我曾经去过长城两次 it has rained every day this week.这个星期天天下雨。
i h**e never seen such a beautiful bird.我从没见过这么美丽的鸟。
i h**e often met the old man on my way to work.我在上班的路上常常遇见那位老人。
4) 现在完成时与一般过去时的区别
1．现在完成时强调过去发生的动作对现在的影响和结果，而一般过去时与现在没有联系，只是说明某个动作发生的时间是在过去。
比较：i h**e washed the car. 我洗过了车。（看上去很漂亮） i washed the car a moment ago. 我刚才洗过车了。
she has watered the flowers. 她已经浇了花。（不需要再浇了） she watered the flowers yesterday. 她昨天浇的花。
三、现在完成时表示的动作或状态延续到现在并可能延续下去，而一般过去时则单纯表示过去某段时间内的经历。比：it has rained for five hours.
雨已经下了5个小时了。
it rained for live hours yesterday. 昨天下了5个小时的雨。 he has waited for her for two hours.
他等她已经两个小时了。
he waited for her two hours and then went home. 他等她等了两个小时，然后就回家了。
i h**e reviewed two lessons this morning. 今天上午我已经复习了两课。（说话时还在上午）
i reviewed two lessons this morning. 今天上午我复习了两课。（说话时已是下午或晚上）
四、比较过去时与现在完成时。
1）过去时表示过去某时发生的动作或单纯叙述过去的事情，强调动作；现在完成时为过去发生的，强调过去的事情对现在的影响，强调的是影响。
2）过去时常与具体的时间状语连用，而现在完成时通常与模糊的时间状语连用，或无时间状语。
一般过去时的时间状语：
yesterday, last week，…ago, in1980, in october, just now, 具体的时间状语。
共同的时间状语：
this morning, tonight,this april, now, once，before, already, recently，lately
现在完成时的时间状语。
for, since, so far, ever, never, just, yet, till / until, up to now, in past years, always,不确定的时间状语。
3）现在完成时可表示持续到现在的动作或状态，动词一般是延续性的，如live, teach, learn, work, study, know.
过去时常用的非持续性动词有come, go, le**e, start, die, finish, become, get married等。
举例：i saw this film yesterday.（强调看的动作发生过了。）
i h**e seen this film. （强调对现在的影响，电影的内容已经知道了。）
why did you get up so early?（强调起床的动作已发生过了。）
who hasn't handed in his *****? （强调有卷子，可能为不公平竞争。）
she has returned from paris. 她已从巴黎回来了。she returned yesterday. 她是昨天回来了。
he has been in the league for three years.(在团内的状态可延续)
he has been a league member for three years. (是团员的状态可持续)
he joined the league three years ago. (三年前入团，joined为短暂行为。)
i h**e finished my homework now. will somebody go and get dr. white?
he's already been sent for.
句子中如有过去时的时间副词（如 yesterday, last, week, in 1960）时，不能使用现在完成时，要用过去时。
（错）tom has written a letter to his parents last night. （对）tom wrote a letter to his parents last night.
past,now and future
long long ago, many families had three or four children. they couldn't look after everyone well, so the children must do everything by themselves. they were too poor to go to school.
some of them liked learning, but they had to go to find jobs to make money. since they were children, they could do lots of difficult things like their parents. sometimes they even did better than them!
but now, many families h**e only one child and they regard their child as a pearl. they did everything for the children. every day, when the child gets up, their parents help him to make the room clean.
they also get breakfast ready for their child. when the child is free, they can sleep or do other things, but they needn't do any housework. so many children can't cook; wash their clothes, some don't even know how to clean the floor.
that's too the future, many families will h**e computers. we can work on the computer instead of going out to do everything. the children also can learn on the computers, so they don't need to move!
after a long time, we'll become fatter and fatter. we won't be able to do anything by ourselves!
so, which way is good for us? we must think more.
以上作文需背诵，要听写）
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