The problem is that the amount of energy required may significantly exceed that which the hydrogen can subsequently be used to generate.

问题是这些方法需要的能量可能比其生成的氢气能产生的能量高许多。

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The researchers used what's called an ion microscope to compare the amount of normal hydrogen in the moon rocks to the amount of the hydrogen isotope deuterium, which carries an extra neutron.

研究人员利用所谓的离子显微镜来比较月球岩石中正常的氢元素含量及同位素氘的含量，元素氘比氢多带一个中子。

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The expected amount of hydrogen loss matches the net excess of oxidized material on Earth today.

科学家估算出的氢气总逃逸量与地球今天氧化物的净剩馀量刚好相吻合。

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So, for example, if we look at the 2 s orbital of argon, it's going to have the same amount of nodes and the same type of nodes that the 2 s orbital for hydrogen has.

所以举例来说，如果我们看氩的2s轨道，它有相同数量的节数,和相同类型的节点,对于氢的2s轨道。

麻省理工公开课 - 化学原理课程节选

This is drawn into the engine, compressed and mixed explosively with a small amount of hydrogen.

BBC: Experimental jet 'a success'

Bees also secrete an enzyme that adds a small amount of hydrogen peroxide.

FORBES: The Buzz

Like alcohols, fatty acids are molecules that have lots of hydrogen and carbon atoms, and a small amount of oxygen (in their case two oxygen atoms, rather than one).

ECONOMIST: Advanced biofuels