动词的时态：现在完成时
1. 表示到现在为止已经完成或刚刚完成的动作,即已完成用法。
Someone has broken the window. 有人把窗户打破了。
He has travelled over many lands. 他到过许多国家。
He's been ill. 他刚生过病。
2. 表示从过去持续到现在(或许还在进行下去或刚刚结束)的动作或状态,即未完成用法。
I have been here since last October. 从去年10月起,我一直在这里。
These shoes are worn out. They have lasted a long time. 这些鞋子穿破了,它们已穿了很长时间了。
3. 表示从过去开始到目前为止反复发生的动作或多次出现的状态。这时常与频度副词always,often,every day等连用。
My father has always gone to work by bike. 我父亲一向骑车上班。
I have often heard that he is the cleverest person in the government. 我常听人说,他是政府里最聪明的人。
4. 在时间、条件、让步从句中表示将来某时以前已完成的动作。
I'll go with you as soon as I have finished my work. 我工作结束了马上就跟你一块儿去。
We'll start at nine if it has stopped raining by that time. 到那时要是雨停了,我们将在9点钟出发。
5. 常用于现在完成时的状语
1）表示不确定的时间状语用于表示“已完成”。这类时间状语有already,yet,
recently,lately等。
2）More than a week has passed already. 一个多星期过去了。
I've already read that book. 我已经读过那本书了。
I haven't learned the word yet. 我还没有学会那个单词。
I have recently had my appendix removed. 我最近切除了阑尾。
3）表示包括现在在内的时间状语可用于表示“已完成”。这类时间状语有just,before,now,this morning等。
Have you been here before?你以前来过这里吗?
He's just gone. 他刚走。
I have got up very early this morning. 我今天早上起得很早。
4）表示频度的时间状语可用于表示“已完成”。这类时间状语有never,ever,often,once,sometimes,six times等。
Have you ever seen a ballet before?你曾看过芭蕾舞剧吗？
I have seen his name in the papers rather often of late. 我近来常在报纸上看见他的名字。
I have been there only once this year. 我今年只去过那儿一次。
5）since引导的表示从过去某“点”时间到现在的时间状语可用于表示“未完成”。
I have met him often since I lived here. 自从我在这里住下之后我常看见他。
I have learned a lot from him since I knew him. 自从我认识了他,我向他学到许多东西。
He has never been to see me since I was ill. 从我生病以来他一直没来看过我。
6）for引导的表示一段时间的时间状语可用于表示“未完成”。
I have lived here for more than thirty years. 我已在此住了30年。
She has been ill for three days. 她已经病了3天了。
