On the inside there's a seed with a hard shell.

在这里面有一颗有硬壳的种子。

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The shell is smooth on the inside.

贝壳内壁光滑。

《牛津词典》

The hard shell on a beetle is an outside protection, as is the "skin", called cuticle, of an earthworm.

甲壳虫身上的硬壳是外表保护层，就像蚯蚓的“皮肤”，它叫角质层。

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The other main difference that we're really going to get to today is that in multi-electron atoms, orbital energies depend not just on the shell, which is what we saw before, not just on the value of n, but also on the angular momentum quantum l number. So they also depend on the sub-shell or l.

我们今天要讨论的,另一个很重要的区别就是,在多电子原子中，轨道能力不仅仅依赖于，我们以前看到的外层，不仅仅依赖于n的值，而是与角动量量子数也有关系,所以它们也依赖于亚外层或者。

麻省理工公开课 - 化学原理课程节选

"How the sound reflects off this reflecting surface with this composite object on it - which is pretty big and has a cloaking shell on it - really reflects... just like a flat surface does, " Dr Cummer said.

BBC: Acoustic 'cloaking device' shields objects from sound

Although scientists have long recognised that mid latitudes were warmer when dinosaurs walked the Earth, some researchers have held to the view - partly based on the previous shell data - that different ocean currents must have operated at the time, leading to warmer polar temperatures but, crucially, cooler tropical temperatures.

BBC: Dinosaurs felt the heat

Aquaculture techniques produce more uniform oysters, allowing growers to charge more for them on the half-shell market.

WSJ: Planting Seeds for a Better Oyster Harvest