In this form, the signs of the disease appear and begin to grow worse, with no periods of disappearance.

VOA: special.2009.01.06

We've probably had four major periods in American history of there's one other picture I wanted to put up.

在美国历史上,我们大约经历了四个时期,在我想贴的另一张图片上

耶鲁公开课 - 美国内战与重建课程节选

And the cold periods last like for...I'd say, from like from September to like maybe near to like May.

寒冷时节会持续大概……我想说，从九月份到可能接近五月左右。

关于伦敦的天气 - SpeakingMax英语口语达人

In Kenya,a project aims to educate girls about H.I.V.prevention while helping them stay in school during their monthly periods.

VOA: special.2009.03.16

Cells can stop in their lifetime at some point in the cell cycle and persist for long periods of time.

细胞生命期可以停止在细胞周期的某个点,并保持很长时间

耶鲁公开课 - 生物医学工程探索课程节选

Other scientists have shown that sun spot activity can be measured in periods of time that last about eleven years.

VOA: special.2009.09.29

But think of the various periods during the night in which you are in a deep, deep dreamless sleep.

但请设想你处在这样的夜晚,你处于熟睡，安枕无梦。

耶鲁公开课 - 死亡课程节选

These problems may appear and then disappear, sometimes resulting in long periods when there are no problems at all.

VOA: special.2009.01.06

Relative to the whole market, It's well known that over periods of multiple decades the market has a tendency to go up.

是和整个市场相关的对吗，我们都知道经过几十年的时间周期,市场会有上涨的倾向。

麻省理工公开课 - 计算机科学及编程导论课程节选

Charles Darwin developed the theory of how living things develop from simpler organisms over long periods of time.

VOA: special.2009.02.25

They thrust together different texts, different languages, writing from different historical periods, all there, compressed in that remarkable mad song that concludes the poem.

它们将不同文字，不同语言，不同历史时代的书写，相互交织穿插，都呈现在那里，摘要叙述在一首举世闻名却又疯狂的结尾歌里。

耶鲁公开课 - 现代诗歌课程节选

Archeologists are able to estimate the age of these objects by dividing layers of dirt into time periods.

VOA: special.2009.08.18

So war time periods were typically periods of great inflation and debasement of the currency.

所以，战争时期通常是,严重的通货膨胀,和货币改造的时期。

耶鲁公开课 - 金融市场课程节选

The two time periods tested whether people were more likely to act differently in the short term than in the long term.

VOA: special.2009.03.03

And then in the intervening periods, they are on distant learning modules that the students complete.

其余时间，学生通过远程学习模式完成。

哈佛公开课 - 幸福课课程节选

Their purpose was to explore some of the problems of manned flight, during short periods,in lower space.

VOA: special.2010.07.07

He also shows, however, that normal politics is, itself, dependent upon extraordinary politics, periods of crisis, anarchy, instability, revolution, where the normal rules of the game are suspended.

然而他也同时了解到常态政治，本身有赖于破例政治，诸如危机，失序，不稳定，革命等时期，当游戏的常态规范,遭搁置。

耶鲁公开课 - 政治哲学导论课程节选

The next time you think about going without sleep, consider this: Laboratory animals that are kept awake for long periods of time ...die.

VOA: special.2009.08.26

We have probably four great reform periods in American history.

我们美国历史上约有四个大改革时期

耶鲁公开课 - 美国内战与重建课程节选

There are also twenty historical rooms which show different periods of American building and furniture design.

VOA: special.2010.08.04

The trouble is, you just don't know when that explosion took place, and since there are several periods in this general area that we're talking about now, in which something big happened, some great change takes place, it turns out different people want to have their explosion at different times.

问题是,你不了解火山爆发的,确切时间以及这种爆发,在这个区域又延续了很多个时期,这些时期发生了许多重大事件和重大变化,结果就是不同人对,火山爆发的时间推测各不相同

耶鲁公开课 - 古希腊历史简介课程节选

Rebecca Skloot tells this complex story by going back and forth between subjects and time periods.

VOA: special.2010.07.21

What we are hearing were periods of quietness and periods of a lot of action potentials.

我们听到的是一段寂静,然后是可能出现很多活动的一段时间。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选

But once the seeds are planted, she does suggest covering the soil with a little mulch to protect it during rains and dry periods.

VOA: special.2010.03.02

The trouble with the etymology of theory and the way in which the word has been used traditionally is that sometimes it actually means practice, and then at other historical periods it means something very different from practice, something typically from which practice is derived.

理论这个词在词源,和传统的使用方法上的复杂之处在于,它有时候指的是实践，但在特定的历史时期,它指的是和实践非常不同的东西，也就是实践产生的依据。

耶鲁公开课 - 文学理论导论课程节选

Mister Chavez often went for long periods without food to protest the conditions under which the farm workers were forced to do their jobs.

VOA: special.2009.09.06

And that explains the succession of rulers that have held the region: the Egyptians, the Amorites, the Israelites, the Assyrians, the Babylonians, the Persians, the Greeks, the Greek Ptolemies, the Seleucids, the Romans, and the list continues as we go on into the medieval and the modern periods.

这也解释了众多的统治者占领这一地区的原因：,埃及人，亚摩利人，以色列人，亚述人，巴比伦人，波斯人，希腊人，希腊的托勒密人，塞琉西人，罗马人，这个列表可以继续下去,如果我们考察中世纪和现代时期。

耶鲁公开课 - 旧约导论课程节选

An astronomer at Harvard College, Henrietta Leavitt, had discovered that these periods of brightness could be used to measure the star's distance from Earth.

VOA: special.2009.04.29

You see like the hot periods and the really cold periods.

你可以看到酷暑时节和寒冷时节。

关于伦敦的天气 - SpeakingMax英语口语达人

A lot of these processed foods have very long shelf lives and therefore can be stored for long periods of time.

很多加工食品为了便于储藏销售,都有很长的保质期

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选