文档介绍：现在完成时
现在完成时的构成:助动词have (has) + 过去分词
用法:1. 表示过去发生或已经完成的某一动作对现在造成的影响或结果。
2. 表示动作或状态从过去某一时刻开始,一直延续到现在,而且可能还要继续下去
常见时间状语有:already, yet, before, recently, for, since, never, ever, once, twice, so far, up to now, in the past/last ... years等
疑难拓展:
1. since 和 for的用法区别
since 用来说明动作的起始时间,for用来说明动作延续的长度。
1)使用since的情况:since + 一段时间+ ago . I have been here since five years ago.
since + 一个过去的时间点 . I have been busy since last Tuesday.
since + 一般过去时态的句子 . I have visited many places since I came to Canada.
2)使用for 的情况:for + 一段时间 . I have taught English for about 15 years.
2. already和yet的区别
already 多用于肯定句当中,通常位于过去分词之前;yet多用于疑问句或否定句的末尾。
3. 现在完成时中,短暂性动词与一段时间连用的两种方法
open, close, finish, begin, come, go, arrive, reach, get to, leave, move, borrow, buy, die等都是短暂性动词,不能直接跟表示一段时间的状语连用。短暂性动词与一段时间连用可通过以下两种方法:
1)用相应的延续性动词替代:e – be, come – be, close – be closed, open – be open, catch – have, come/arrive – be (in), leave/go – be away, start/begin – be on, finish – be over, buy – have, borrow/lend – keep, join – be in/be a member (of), die – be dead, fall asleep – be asleep, go to sleep – sleep, get married – be married, get up – be up, make friends – be friends, move – be out (of), put on – wear, 等。
. I have kept this book for five days. 这本书我已经借了五天了。
2)用“It is ( has been) + 时间段+since从句
. It is three years since he bought puter. 他买这台电脑已有三年了。
4. have/has been to, have