It is an efficient obstacle to material exchange and avoids the skin's drying out.

它是物质交换的有效阻隔并防止皮肤干燥。

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Between the reservoir system and the external environment the constant material exchange makes the dynamic reservoir system more complex.

油藏系统与外界不断地进行物质交换，造成油藏动态系统更加复杂化。

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The gas flow and the liquid complete the energy exchange and the material exchange between gas phase and liquid phase in the flowing process.

气流和液体在流动的过程中完成气相与液相之间的能量交换与物质交换。

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The amendment makes it a crime for anyone to deploy peer-to-peer technology that facilitates the exchange of copyrighted material online.

VOA: standard.2009.04.23

Typically these are created when two existing strains infecting an animal such as a bird or a pig exchange genetic material.

BBC: La Nina 'linked' to flu pandemics

File-exchange sites like Gnutella and Hotline, which act as matchmakers for people who want to exchange movies and other copyrighted material, aren't nearly as easy to use as the popular music-exchange program Napster.

CNN: Studios hope to prevent a movie 'Napster' from taking hold

That is, they produce a stream of electrons (electricity) by forcing two bits of charged material, say nickel and cadmium, to exchange electrons.

FORBES: Running in place