北京到旧金山如何选择通道？

How to choose the channel from Beijing to San Francisco?

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不明海关规定或不知如何选择通道的旅客，应选“申报”通道，向海关办理申报手续。

Passengers that do not understand the Customs regulations or do not know how to choose the right channel shall choose the "GOODS to DECLARE" channel to go through the formalities for declaration.

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当您完成了护照检查后，请携带您所有的行李(包括托运行李)，自行选择通道通关。

After you have gone through the passport checking points, please take all of your baggage including your checked baggage, and choose the right channel to pass through the Customs.

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However, when that gate is opened, the sodium channel is now going to be incredibly selective and only let through sodium ions and no other type of ion.

但是，当闸门打开的时候，钠离子通道,将会有极高的选择性,不允许除钠离子以外的任何其它离子通过。

麻省理工公开课 - 化学原理课程节选

And all ion channels are selective for a single type of ion, and we can think about how that selectivity takes place, and that's where this idea of atomic radius is going to become very important.

所有的离子通道都是仅对某一种离子具有选择性的，而我们可以来想一想这种选择性是如何发生的，这也就是原子半径这个概念将会变得，非常重要的地方。

麻省理工公开课 - 化学原理课程节选

What all of these channels have is what's called a selectivity filter, so this filter filters out the type of ion that's going to be allowed through.

这些离子通道都有的一部分,就是所谓的选择性过滤器，这个过滤器,会滤过允许穿过的离子。

麻省理工公开课 - 化学原理课程节选