So really, you can not ever rotate a double bond, it makes your molecule very rigid.

实际上，你不能转动一个双键，它使得你的分子很坚固。

麻省理工公开课 - 化学原理课程节选

It's made of strong metal, it's got very thin slits to be able to see straight ahead, covered up; everything else is covered up, a good one will cover your neck as well.

头盔是坚固的金属制成,正面有一条很细的开口能让士兵看到前方,左右两边都包住,剩下所有地方都包住,好一点的头盔甚至能保护颈部

耶鲁公开课 - 古希腊历史简介课程节选

There are different kinds of cell walls in bacteria but they have a rigid cell wall and our cells don't have a rigid cell wall, we have a fluid lipid like cell wall.

细菌有不同种类的细胞壁,但都很坚固,人类细胞没有坚固的细胞壁,我们有一层类似细胞壁的流动的脂类

耶鲁公开课 - 生物医学工程探索课程节选

Because the Mycenaean centers all reveal for that stretch of time that they're scared. The proof of it comes from strengthening their already quite strong walls in almost all the sites that we see, and also--this is a very important fact.

因为在迈锡尼文明的中心,有迹象表明在一段时期,他们受到了威胁,这样说的证据是,我们发现的几乎所有的遗迹,都在本就很坚固的城墙上继续加固,而且,这是一个很重要的史实

耶鲁公开课 - 古希腊历史简介课程节选