现在完成时与过去完成时和过去进行时有什么区别?

    现在完成时 Present Perfect Tense 现在完成时：主语+动词的过去分词。 对于汉语圈的人来说，关键在于这个时态的用法。这个时态在英语和美语之间，使用上也存在一些差别。
  一般来说，用于如下三种情况： 过去的经验： Experience from the past。  We are not interested in when you did something。
   We only want to know if you did it。我们不想知道你是什么时候做的某件事情，我们只想知道你是否作过。这就是和过去时的区别，过去是强调是过去。   例如：I have read that book。
   He has lived in America。 这些事情发生在过去（与过去有联系），现在在我的脑海里有这个记忆，我知道了过去发生的这些事情，我有了这些事情的经验（与现在有联系）。 改变 A change or new information。
    例如：I have bought a notebook computer。就是说，上周我还没有笔记本电脑，但是现在我有了。这就是状态的改变(说话者并不关心你是什么时候买的，他只是关心你的状态的改变：没有→有)，用现在完成事。
  又如：The police have arrested the killer。   持续的状态 A State started in the past and continues in the present (and will probably continue into the future)。
   也就是说一个状态，从过去持续到现在，而且很有可能继续持续到将来。  例如：I have studied here since June。这是一个状态（而不是动作），我们经常与for或者since连用。
  又如：They have been married for five years。 过去进行时 Past Continuous Tense The past continuous tense is an important tense in English。
     We use it to say what we were in the middle of doing at a particular moment in the past。
   结构： 主语+was/were+V-ing。否定：主语+was not (wasn't)/were not (weren't)+V-ing。  疑问：Was/Were+主语+V-ing。
   The past continuous tense expresses action at a particular moment in the past。 The action started before that moment but has not finished at that moment。
     For example, yesterday I watched a film on TV。 The film started at 7pm and finished at 9pm。
  =>I was watching TV at 8pm yesterday。 有一些动词不能用在进行时态，这些动词都是表示感情或感觉的动词，而没有实际的动作。  如： hate, like, love, need, prefer, want, wish believe, imagine, know, mean, realize, recognize, remember, suppose, understand belong, concern, consist, contain, depend, involve, matter, need, owe, own, possess appear, resemble, seem, hear, see With verbs that we don't use in the continuous tense, there is no real action or activity。
     Compare "to hear" and "to listen"。 "To hear" means "to receive sound in your ears"。
   There is no real action or activity by you。 We use "to hear" with simple tenses only。   But "to listen" means "to try to hear"。
   You make an effort to hear。 There is a kind of action or activity。 We can use "to listen" with simple or continuous tenses 我们经常用 过去进行时+一般过去时。
    这样组合起来使用，用过去仅形式来表现一个长的动作；用过去时来表示一个短的动作，这个短的动作发生在那个长的动作中间。我们通常可以用when或者while来把两者联系起来。
   We often use the past continuous tense with the simple past tense。   We use the past continuous tense to express a long action。
   And we use the simple past tense to express a short action that happens in the middle of the long action。
     We can join the two ideas with when or while。 例如：I was watching TV when you telephoned。
  long action (watching TV), expressed with past continuous tense；short action (telephoned), expressed with simple past tense。
     Notice that "when you telephoned" is also a way of defining the time [8pm]。 when + short action (simple past tense) while + long action (past continuous tense) While I was walking past the car it exploded。
     = When the car exploded I was walking past it。 The car exploded while I was walking past it。
   = I was walking past the car when it exploded。   过去进行时和过去时的区别是前者表示正在进行的动作，后者表示一个完成的动作。
  另外，和现在进行时一样，过去进行时可以用来代替一般过去时，表示赞美、厌烦等情绪。 如：All the time he was thinking of his work。->他老是想着他的工作。
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