化学物质的蒸发对它们的生存是必不可少的。

The evaporation of chemicals is necessary for their survival.

youdao

对于人们来说，发明是至关重要、必不可少的，正如灵魂对人们来说是不可或缺且意义重大的一样。

Invention is momentous and fundamental to people what the soul is vital and significant to us.

youdao

对前几代人来说，大学是摆脱父母控制的一个决定性时期，同时同龄人和长者的支持与指导也是必不可少的。

For previous generations, college was decisive break from parental control; guidance and support needed help from people of the same age and from within.

youdao

First, the historical prologue that's so central to the suzerainty treaty, grounds the obligations of Israel to Yahweh in the history of his acts on her behalf.

第一点，历史开场白在领主契约中,是必不可少的，规定了犹太人,对上帝需要履行的义务。

耶鲁公开课 - 旧约导论课程节选

We're going to get a deep insight if it's a necessary truth about death that everyone dies alone.

如果这是对死亡来说必不可少的真理,那我们能得到一些深刻理解。

耶鲁公开课 - 死亡课程节选

Rights that are so essentially mine that even I can't trade them away or give them up.

这些权利如此基本，对我必不可少,连我自己都不能出售或放弃它们。

耶鲁公开课 - 公正课程节选