高中英语语法详解：现在完成时用法详解
<p>现在完成时的概念是过去发生或已经完成的动作对现在造成的影响或结果，或从过去已经开始，持续到现在的动作或状态。</p><p>(一)肯定式</p><p>主语+助动词<span word="have">have</span> /<span word="has">has</span> +过去分词+其它</p><p>说明：这里的<span word="have">have</span> /<span word="has">has</span>是助动词,没有什么具体意义.当主语是第三人称单数时助动词用<span word="has">has</span>,其余人称一律用<span word="have">have</span>. <span word="has">has</span>,<span word="have">have</span>的缩略式分别为'<span word="s">s</span>或'<span word="ve">ve</span>.</p><p>规则动词过去分词的构成与过去式的构成方式一样,不规则动词可参看不规则动词表.实例：</p><p>1)<span word="I">I</span>'<span word="ve">ve</span> <span word="just">just</span> <span word="copied">copied</span> <span word="all">all</span> <span word="the">the</span> <span word="new">new</span> <span word="words">words</span> .我刚抄写了所有的生词. (表示不要再抄了)</p><p>2)<span word="She">She</span> <span word="has">has</span> <span word="lost">lost</span> <span word="her">her</span> <span word="books">books</span> .她丢失了她的书. (表示到目前为止还没有找到)</p><p>(如果用过去时：<span word="She">She</span> <span word="lost">lost</span> <span word="her">her</span> <span word="books">books</span> . 则强调书是过去丢的这一动作,而不知现在有没有找到)</p><p>3)<span word="We">We</span>'<span word="ve">ve</span> <span word="just">just</span> <span word="cleaned">cleaned</span> <span word="the">the</span> <span word="classroom">classroom</span> .我们刚好打扫了教室.(表明现在教室是干净的)</p><p>(二)否定式</p><p>主语+助动词<span word="have">have</span> /<span word="has">has</span>+<span word="not">not</span>+过去分词+其它</p><p>说明：现在完成时构成否定句时,只需在助动词<span word="have">have</span> /<span word="has">has</span>后面加<span word="not">not</span>就行.<span word="have">have</span> <span word="not">not</span>,<span word="has">has</span> <span word="not">not</span>的缩略式分别为<span word="haven">haven</span>'<span word="t">t</span> ,<span word="hasn">hasn</span>'<span word="t">t</span>.另外,肯定句中有<span word="some">some</span>,<span word="already">already</span>时,改为否定时要分别改成<span word="any">any</span>,<span word="yet">yet</span>.实例：</p><p>1)<span word="I">I</span> <span word="haven">haven</span>'<span word="t">t</span> <span word="finished">finished</span> <span word="my">my</span> <span word="homework">homework</span> <span word="yet">yet</span>.我还没有完成我的作业.</p>
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