2015年在职工硕英语备考：现在完成时

　　定义：表示目前已经完成的动作或刚刚完成的动作，也可表示从过去某一刻发生，现在仍延续着的动作或情况。此时态强调动作对现在的影响。

　　Grain output has greatly increased in the past few years. 这几年粮食产量有了很大增长。

　　The area has suffered from disastrous floods throughout its history.这个地区历史上一直遭受水患之苦。

　　常见时间状语：

　　表示已完成：lately, already, just, yet, never, ever, before 等词连用，或不带状语。

　　He has just left.

　　He has finished his homework.

　　Tom has rung three times already this morning.

　　I have never seen him before.

　　表示未完成：since, for, so far, up to now, in the past few weeks , these days 等(多表示到目前为止这段时间)

　　The couple has lived here for 20 years.

　　We have been great friends ever since we first met in America.

　　He has finished 3 term papers up to now.

　　过去时&现在完成时

　　现在完成时的基本特点是它和现在有密切的联系，或是指迄今为止这一段时间的情况，或是过去发生的事对现在造成的影响或结果等。而过去时主要强调过去某时刻所发生的动作或情况，与现在没有任何联系。如：

　　Up till now we have planted over 10,000 apple trees. 到目前为止我们共种了一万多棵苹果树。

　　I saw him a minute ago. 我前一会还见到他的。

　　注意

　　①表示瞬间行为动词come, join, finish, marry, return等不能和表示延续的时间状语连用, 只能用系动词加表语结构来代替。如: He has been back for over a week. (不能用has come back) / I have been in the army for three years. (不能用have joined) ② since "自从…"以来;for表示时间,从过去开始延续至今,它们都是现在完成时的典型信号词。③ 句子中有表示过去时的时间副词(如yesterday, last week, in 1990, ago)时,不能使用现在完成时要用过去时态。

  本文选自新东方在线论坛。