His presidency comes to a close at a time of economic crisis.

VOA: special.2009.01.17

Why don't we have you, when the time comes, raise your hand if you're supposed to be representing a one?

为什么让家上来呢，如果你代表1，就举起你的手？

哈佛公开课 - 计算机科学课程节选

We have 266 ping-pong balls, and we need someone, hopefully you, to be some radioactive material that are going to be emitting these ping-pong balls. And when the time comes, in just a minute, I'll ask the TAs to come down and hand these out very quickly to you, so we can do this experiment.

你们有些人那天，看到我在办公室数乒乓球，我们需要几个人,希望是你,来作为放射材料，放射这些乒乓球,等会我会让助教,把这些球发给你们。

麻省理工公开课 - 化学原理课程节选

But Warren says the good news comes at a time when researchers are facing a big obstacle - limited funding.

VOA: standard.2010.07.15

The national security challenge comes at a difficult time for Mr.Obama, who later this month will mark his first year in office.

VOA: standard.2010.01.06

All of this comes at a time when Poland's confidence in the U.S.is waning.

VOA: standard.2009.10.22

This latest incident comes at a time when Afghanistan is witnessing its worst violence of the eight-year-long war following the ouster of the Taliban from power in 2001.

VOA: standard.2009.09.12

The terrorism attempt comes at a bad time for U.S.-Pakistani relations.

VOA: standard.2010.05.06

This comes at a time when opinion polls show dropping support among Americans for the military effort in Afghanistan, where Afghan,American and NATO coalition forces together are fighting the Taliban.

VOA: standard.2009.09.04

The report's release comes at a sensitive time. The Obama administration is debating whether to deepen its commitment to the war in Afghanistan, which is becoming increasingly unpopular in the United States.

VOA: standard.2009.09.11

His trip comes at a critical time with the results of the country's presidential election still uncertain and worries a disputed outcome, due to allegations of widespread ballot box stuffing, could spark further civil violence.

VOA: standard.2009.09.04

The outbreak of swine flu in Mexico comes at a time when the country is already struggling with the effects of the worldwide economic recession and some loss of tourism caused by drug violence in cities like Juarez.

VOA: standard.2009.04.30

And I still believe that in Africa we have been going through this kind of pressure for a pretty long time, so I believe that when it comes we can handle it and lift the cup on Friday,".

VOA: standard.2009.10.15

Mr.Ahmadinejad's assault against opposition leaders comes at a time when he is being criticized by his own supporters for using poor judgment in trying to form a new government, and while Supreme Leader Ayatollah Ali Khamenei has softened criticism of the opposition.

VOA: standard.2009.08.28