在这种情况下，骨骼或外壳的原始成分会保留下来，但化石会变得更坚硬、更耐用。

In such cases, the original composition of the bone or shell remains, but the fossil is made harder and more durable.

youdao

这辆四轮马车外壳的油漆严重地剥落。

The wagon's paint was badly chipped on the outside.

《柯林斯英汉双解大词典》

该机器的秘密在于其一体式碳纤维外壳的流线型设计。

The secret of the machine lies in the aerodynamic shape of the one-piece, carbon-fibre frame.

《柯林斯英汉双解大词典》

So let's do a quick clicker question, and you tell me how many valence electrons does fluorine have? Remember, valence electrons are different from core, they're only the outer-most electrons in the outer-most shell.

那么让我们来做一个小选择题，请大家来告诉我,氟有多少个价电子，要记得，价电子与芯电子不同，它们是在最外壳层的最靠外面的电子。

麻省理工公开课 - 化学原理课程节选

In that case, we took the gene for the Hepatitis B protein.

在此种情况下,我们将乙肝病毒的基因同蛋白质外壳分离

耶鲁公开课 - 生物医学工程探索课程节选

So remember, that when we talked about Lewis structure, the organizing principle behind Lewis structures is the idea that within the molecule the atoms are going to arrange their valence electrons, such that each atom within the molecule has a complete octet or full outer shell.

记得，当我们讨论路易斯结构的时候，路易斯结构所遵循的组织原则是这样一种思路,那就是分子中的原子都倾向于,重新安排它们的价电子,使得分子有一个完整的,“八隅体“或者排满的外壳层。

麻省理工公开课 - 化学原理课程节选