现在完成时态的有关知识
一、现在完成时态的基本结构：
二、现在完成时的两种用法：
1、已完成用法。
He has turned off the light.
他已把灯关了。（动作结束于过去，但说明的是现在的情况——灯现在不亮了。）
I have bought a new computer.
我买了一台新电脑。（动作发生并结束于过去，但说明现在的情况——现在我有了一台新电脑。）
现在完成时的“已完成用法”的特点是动作不延续，因此，该时态只能与
●频度时间状语（如：节日的焰火打一成语never从不, ever曾经, once一次, twice两次, three times三次,等）、
●包括现在时刻在内的时间状语（如：this morning /month/ year…,today等）连用。如：
Have you found your pen yet? 你已到你的钢笔了吗？
I have seen the movie twice. 这部电影我已经看过两次。
Lucy has just been to the teachers’ office. 露西刚去过过教师的办公室。
They have already cleaned the classroom. 他们已经打扫了教室。
2、未完成用法（或“持续用法”）
现在完成时的“未完成用法”——指的是动作开始于过去某一时刻，一直延续到现在，或可能还要继续下去。即：表示过去已经开始，持续到现在的动作或状态。
玉琉璃●此用法常和表示从过去某一时刻延续到现在（包括“现在”在内）的一段时间的状语连用，即：
for +一段时间；
since +过去的时间点；
since +从句（句子用一般过去时）
●或表示与现在时刻相连的时间状语：
担当的事例素材so far, up to now, by now, in/during the past few weeks,等。如：
He has lived here since 1978.
自从1978年以来，他一直住要这儿。（动作起始于1978年，一直住到现在，可能还要继续住下去。）
I have been in the army for more than 5 years.
我在部队已经呆了五年多了。（动作开始于5年前，一直延续至今，有可能还要继续下去。）
I have done a lot of useful work in the past few years. 在过去的几年间我做了很多有益的工作。
So far we have learned three thousand English words. 到目前为止我们已经学习了三千个英语单词。
注意：
（1）现在完成时的“未完成用法”必须用延续性动词（即：表示行为动作可以持续不断进行的动词，动作发生的时间是长期的。如：live, work, have, keep, know, learn…），不可用
短暂性动词（即：表示瞬间就结束或动作发生的时间是短暂有动词。如：come, go, arrive, leave, join, become, die, buy…）。因为延续性动词可以和表示一段时间的时间状语连用，而短暂性动词不能与since, for 引导的表一段时间的状语的肯定句连用。
幼儿园数学教案如果短暂性动词要与表一段时间的时间状语连用，需先将短暂性动词变成延续性动词。
（2）现在完成时常见两种句型：
① 主语+have / has been …+ for短语
② It is + 一段时间 + since从句
如：He has been in the League for three years. 或 It is three years since he joined the League.
他入团已经三年了。
练习：
( )1. Sorry, we’ve ________ the tickets.
A. sell out B. sold out C. sell of D. sold of
( )2. ---Where is your father? --- He _______ America on business, he isn’t at home now.
A. has been go B. have been to C. have gone to D. has gone to
( )3. ______ she ever ______ Nanning?
A. Does, visit B. Are, visiting C. Has, visited D. Have, visited
( )4. We have lived in Beijing ______ ten years.
A. in B. at C. for D. since
( )5. ---________ have you known her? --- For two years.
隋朝多少年历史 A. How long B. How often C. How far D. How many
( )6. ---Have you ever been to Guilin? --- Yes, I _______ there twice.
A. have been B. have gone C. have been to D. have gone to
( )7. Have you ______ visited the Great Wall ?
A. ever B. before C. did D. done
( )8. --- What have you done? --- I’ve just _______ the floor.
A. cleaned B. clean C. to clean D. wash
( )9. I have ______ finished my homework., but I haven’t cleaned my room ________.
A. already, already B. yet, yet C. just, already D. already, yet
( )10. _____ Jack ________ the book before?
A. Have , seen B. Has, seen C. Has, read D. Has, watched
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