When there is a full moon, this nocturnal rodent is careful to stay in its burrow.

在有满月出现的时候，这种夜间出没的啮齿类动物小心地呆在它的洞里。

《柯林斯英汉双解大词典》

youdao

youdao

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

VOA: special.2009.01.06

So that's a big help. And equilibrium happens when there isn't any possible change of state that would satisfy this.

这个非常方便，当所有的变化,都无法满足这个公式的时候,系统就达到了平衡。

麻省理工公开课 - 热力学与动力学课程节选

which you'll think, only a ten or eleven year old, but when there is thirteen of them, it's a lot.

你会想，不就是十岁、十一岁的小孩嘛，但有十三个还是很多的。

大城市是否危险？ - SpeakingMax英语口语达人

Ms. SETZFAND: People actually look for information when there's a problem, when there's a pressure point.

NPR: Amid Meltdown, Retirement Ads Stay On Message

For example, back in March, when there was the biggest oil spill in Prudhoe Bay history.

NPR: Alaskans Speak Up About Oil Field Shutdown

There was a period of time when there wasn't much emphasis put on antibiotics.

NPR: Tracking a New Strain of Drug-Resistant Staph