The researchers haven't nailed down the exact reasons behind this trend.

研究人员尚未弄清这一趋势背后的确切原因。

Did try nailing a couple of the boards down.

我把几块板子钉下去了。

I'm just having problems nailing down a background source.

我只是在定下背景起源时碰到了一点点问题。

It's as high as I could nail down so far.

目前是我能找到的最好的线人了。

To nail down the potential environmental influences, researchers focused on the classroom.

为了明确可能存在的环境影响，研究人员将研究重点放在了教室这个特殊场所上。

Others prefer to look for connections between ideas rather than nailing down facts.

另一些人则更喜欢寻找观点之间的联系，而不是弄清真相。

And we've yet to nail down the precise mechanisms behind mucosal destruction.

我们还不能明确粘膜损伤具体的机制。

Finally, after all these centuries, the astronomical unit was nailed down.

几个世纪后，这个天文单位终于被确定下来。

Scientists have not nailed down one single answer, but there are a few possibilities.

科学家们还没有确定一个单一的答案，但有几种可能性。

So without those specific details nailed down, why would the White House accept the invitation?

在这些具体细节都没有确定的情况下，为什么白宫会接受这一会面邀请？