现在完成时的构成形式是“ have +过去分词， has +过去分词”。
现在完成时常被称为“与现在有联系的过去”，因此它不能与明确的过去时间状语连用。
有人把窗户打破了。Someone has broken the window
我最近不常见到她。I haven't seen much of her lately
他们结婚多长时间了？How long have they been married？
现在完成时着眼于过去的动作对现在产生的结果或影响。这是现在完成时的“已完成”用法。
我买了一支笔。I have bought a pen
我现在有一支笔I have a pen now
温度上升了十摄氏度。The temperature has increased by ten degrees centigrade
现在很热了。it is quite hot now
空气污染已经夺去了很多人的生命。Air pollution has taken the lives of many people
空气污染现在很严重了。Air pollution is very serious now
现在完成时的上下文所指的时态必须呼应。
我买了一支笔，但我已经把它丢了。I bought a pen but I have lost it now
我丢了一支笔，但现在已经找到了。I lost my pen but I have found it now
强调过去某一时刻到说话时这段时间中的经历。
你去过长城吗？Have you ever been to the Great Wall？
北京我至少访问过十次了。I have visited Beijing at least ten times
她从未到海滨度过假。She has never spent a holiday at the seaside
这是现在完成时的“未完成”用法，表示一个动作或状态从过去某时开始，持续到现在，可能要继续下去。
他爱好钓鱼为时已久。（他现在仍爱好钓鱼）He's loved fishing for a long time
我已在这儿住了三十多年了。（也许还会继续住下去）I have lived here for more than thirty years
现在完成时的“未完成”用法既可用于动态动词（主要是持续动词），也可用于状态动词，但它一般不适用于表示短暂动作或位置转移的动词，如： open, break, go, come, arrive, leave, 等。如用这类动词表示“未完成”，通常只限于否定结构。
我已经好几个星期没看电影了。I haven't seen a film for weeks
自从九月份以来她还没给我写过信呢。She hasn't written to me since September
现在完成时表示的动作或状态发生在现在时间以前的某个未明确指出的过去时间内，和它连用的时间状语要与现在时间有关，不能是明确地表示过去的时间状语。
不确定的过去时间状语：已经， already, 然而，yet, 之前，before,最近，recently, 最近，lately, 等
我以前看过这部电影。I've seen the film before
近来你去过那里吗Have you been there lately？
频度时间状语： 经常，often, 有时，sometimes，曾经， ever ，从不， never, 一次，once, 很少，rarely,等
我们从未听说过这事。We have never heard of that
他有时打网球。He has sometimes played tennis
大本钟很少出差错。Big Ben has rarely gone wrong
包含现在时间在内的时间状语： now， just today， this morning， this week， this year， 等
我现在刚写完信。I have just finished the letter now
你刚好错过公共汽车。You have just missed the bus
他今天做了很多工作吗？Has he done much work today？
already， 常用于肯定句，置于句中。
yet， 常用于否定句和疑问句，置于句末。
但 already， 有时也可用在疑问句中暗示惊讶的心情。
她早就走了。She has already gone
你已经吃过饭了？Have you eaten your dinner already?
他还没有来。He has not come yet
与“已完成”用法一样，表示具体的过去的时间状语不能与“未完成”用法连用。与其连用的往往是指一段时间的状语以具体表示某一动作或状态持续了多久。
since +具体时间，表示动作或状态从何时开始
自那以后他养成了另一个坏习惯。Since then he has developed another bad habit
他毕业后就没回过家。He hasn't been home since he graduated
for +一段时间，表示动作或状态持续了多久
我们在这里工作很久了。We have worked here for ages
这里已经近两个月没有下雨了。There has been no rain here for nearly two months
到目前为止until now,
up till now,
so far,
up to the moment
到目前为止我没见过他。I have not seen him so far
到目前为止一切正常。up to the present, everything has been OK
在刚刚过去的五年里in the last five years,
during the past five years,
in the past five years,
during the last five years
过去的几个星期里他没在学校。He has been away from school during the last few weeks
在过去的几年中他们已经和好几家跨国公司做成了生意。in the past few years, they have dealt with quite a few international corporations successfully
一直，一整天 all the while,
all day
她忙了一整天。She has been busy all day