She says she'll come, but I can't nail her down to a specific time.

她说要来，但我无法让她敲定具体什么时候来。

《牛津词典》

youdao

By contrast, the audience encounters an opera or a play over a specific time, which is the duration of the performance.

相反，观众可以有一段具体的时间来欣赏话剧或者戏剧，这段时间就是表演的持续时间。

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The G20,which includes major industrialized powers in the Group of Eight plus developing nations with significant economies such as China and India, agreed to a specific time line for deficit reduction, while giving governments flexibility to adjust the pace of changes based on their own situations.

VOA: standard.2010.06.27

And the reason is, and this will come up on the problems and a lot of students end up using this equation, which is why I want to head it off and mention it ahead of time, we can't use an equation because this equation is very specific for light.

原因是，很多同学在解题时,都会用这个方程，所以我要,事先提醒你们一下,我们不能用这个方程，因为它只对光是用。

麻省理工公开课 - 化学原理课程节选

That's why every-- development of every specific vaccine turns out to be different because they don't all follow exactly this kind of time course.

这就是为什么,每一种疫苗的发展都是不同的,因为疫苗诱导产生应答所需时间各不相同

耶鲁公开课 - 生物医学工程探索课程节选

Rather than calling at a specific time, this Santa, based in Colorado, gives a half-hour window.

WSJ: Comparing Santa Video Chats

Ministers have given back millions because their departments cannot spend it within a specific time period.

BBC: Stormont ministers criticised over ?42m in unspent funds

Out of randomness alone there will always be some category that outperforms over a specific time period.

FORBES: Indexes Beat Active Funds Again in S&P Study