Teeth have a hard surface layer called enamel.

牙齿有一层叫做釉质的坚硬表层。

The surface layer consists of oxide, sulphide and N, C compound.

表层由氧化物、硫化物和氮（碳）化合物组成；

I screamed in pain as the knife cut the surface layer of my skin.

我的皮肤被割开了，我痛苦的嘶叫着。

The filtration belongs to deep filtration or surface layer filtration.

这类过滤属深层过滤或表层过滤。

The portion of the current confined to the surface layer becomes negligible.

流经上部地层的那部分电流变得可以忽略不计。