（一）概說

不定式是動(dòng)詞的非謂語(yǔ)形式，但它還保留著動(dòng)詞謂語(yǔ)形式的一些特征，具有時(shí)態(tài)（一般式、完成式和進(jìn)行式）和語(yǔ)態(tài)（主動(dòng)和被動(dòng)）變化。

（二）不定式時(shí)態(tài)的用法

1．現(xiàn)在時(shí)態(tài)——現(xiàn)在時(shí)態(tài)所表示的動(dòng)作跟謂語(yǔ)動(dòng)詞所表示的動(dòng)作同時(shí)發(fā)生或在它之后發(fā)生。例如：

The scientist tries to apply newer way to production.【同時(shí)發(fā)生】科學(xué)家想把較新的方法應(yīng)用到生產(chǎn)中去。

Who heard him say that? 【在后發(fā)生】誰(shuí)聽見了他說那種話？

2．完成時(shí)態(tài)——完成時(shí)態(tài)表示的動(dòng)作在謂語(yǔ)動(dòng)詞的行為之前已經(jīng)發(fā)生或完成。例如：

They are much pleased to have designed such an electronic computer．他們因?yàn)樵O(shè)計(jì)了這樣一個(gè)電子計(jì)算機(jī)而感到很高興。

The energy of coal is found to have come from the sun．人們發(fā)現(xiàn)煤的能量來自太陽(yáng)。

I'm sorry to have troubled you so much．我很抱歉，麻煩了你這么多。

在助動(dòng)詞be和表示“意圖”、“希望”、“需要”等意義的動(dòng)詞的過去式之后用不定式的完成時(shí)；或這類動(dòng)詞的過去完成時(shí)+不定式的一般式，均可表示“過去想做而未做的事情”或“行為沒有實(shí)現(xiàn)”。這類動(dòng)詞有desire, expect, hope, intend, mean, plan，suppose, think, want, wish等。例如：

He was to have left home at nine o'clock．他本該九點(diǎn)鐘離開家。

We planned to have started the work at the beginning of the month.我們?cè)瓉碛?jì)劃月初開始這工作。

We wished to have solved the problem graphically．我們?cè)胗脠D解法解算這道習(xí)題。

I had hoped to catch the 8:30 bus, but found it was gone．我原來希望趕上8點(diǎn)30分的車，但發(fā)現(xiàn)車已開走了。

I had meant to tell you about it earlier, but I could not come．我本想早點(diǎn)把這事告訴你，但我來不了。

用在would like, had better, should, ought, be supposed等之后，也可表示事情未曾發(fā)生過或愿望沒有實(shí)現(xiàn)。例如：

She should have told him he could shower in the house if he wanted.她原該告訴他如果需要，可以用房子里的蓮蓬頭洗澡。

The letter should have been ten pages long．這封信本該有10頁(yè)長(zhǎng)。

You oughtn't to have spoken to them in that way．你本不該這樣對(duì)他們說話。

在情態(tài)動(dòng)詞must, may, might, could或can之后用不定式完成時(shí)，說明對(duì)過去發(fā)生的事情或某種情況表示懷疑或推測(cè)。例如：

You must have used the wrong data yesterday．昨天你一定用了錯(cuò)誤的數(shù)據(jù)了。

And he must have died alone, that's why he had the cameras sent to her．他死時(shí)一定是孤身一人，所以他才讓人把相機(jī)寄給她。

He may have done the work very well．他也許已經(jīng)把工作做得很出色吧。

Could she have forgotten to come？她可能忘記來了嗎？

3．進(jìn)行時(shí)態(tài)——進(jìn)行時(shí)態(tài)表示的行為在謂語(yǔ)動(dòng)詞行為發(fā)生時(shí)正在進(jìn)行。例如：

They were said to be making a new experiment．據(jù)說他們正在做一個(gè)新的實(shí)驗(yàn)。

The new satellite is reported to be flying around the earth．據(jù)報(bào)道新衛(wèi)星正在繞地球飛行。

I don't like you to be always coming late for work．我不喜歡你上班總是遲到。

The weather seems to be improving．天氣似乎正在好轉(zhuǎn)。

情態(tài)動(dòng)詞must, may等之后接不定式的進(jìn)行時(shí)表示對(duì)現(xiàn)在正在進(jìn)行的事或狀況的猜測(cè)或估計(jì)。例如：

Philip thought Rose must be looking forward to his return．菲利普想，露絲準(zhǔn)是盼望他回來。

He may be reading the book．他也許正在讀這本書。

4．完成進(jìn)行時(shí)態(tài)——說明行為在謂語(yǔ)動(dòng)詞表示的行為之前開始，并延續(xù)到那個(gè)時(shí)候可能仍在進(jìn)行。例如：

She was said to have been living in Guangzhou for ten years．據(jù)說她在廣州一直住了十年。

He seems to have been writing an article on applied physics．他似乎一直在寫一篇關(guān)于應(yīng)用物理的論文。

This project is known to have been going on for three months．大家知道這個(gè)工程已經(jīng)進(jìn)行了三個(gè)月。