当空气温度较高时，含有较重同位素氧-18的蒸汽比含有氧-16的蒸汽更容易凝结，并形成雪状的降水。
When the air was warm, vapor containing the heavier isotope, oxygen-18, condensed and formed precipitation, in the form of snow, more readily than did vapor containing oxygen-16.
水中几乎所有的氧都是氧16，但每一千个分子中就有几个含有较重的同位素18。
Almost all the oxygen in water is oxygen 16, but a few molecules out of every thousand incorporate the heavier isotope 18.
通过测量一束头发上较重的氢和氧同位素的比例，科学家可以构建一个地理时间轴。
By measuring the proportion of heavier hydrogen and oxygen isotopes along a strand of hair, scientists can construct a geographic timeline.
当水从海洋表面蒸发时，往往会留下较重的同位素，所以剩余的海水会逐渐富含氧18这种同位素。
Heavier isotopes tend to be left behind when water evaporates from the ocean surfaces, the remaining ocean water becomes progressively enriched in oxygen 18.
在水中大多数氢原子和氧原子是稳定的，但这两个元素也有微量以较重的同位素形式存在。
Most hydrogen and oxygen atoms in water are stable, but traces of both elements are also present as heavier isotopes.
冰河时期海洋中多空虫贝壳化石中积聚的较重的氧同位素比较多，而另一种轻的氧同位素则更多地积聚在古代冰层和积雪中。
During glacial periods, the forams' shells contain more of the heavier of two oxygen isotopes, as the lighter one is preferentially accumulated in snow and ice rather than the ocean.
氘是氢的同位素，在地球上的海洋中广泛存在，其质量较重，很难逃离金星大气。
Deuterium is a heavier form of hydrogen that is common in Earth's oceans and that would have too much mass to escape Venus' atmosphere.
相似的模式在全美都存在。通过测量一缕头发中较重的氢氧同位素的比例，科学家们可以构建一个地理学的时间轴。
Similar patterns exist throughout the U. S. By measuring the proportion of heavier hydrogen and oxygen isotopes along a strand of hair, scientists can construct a geographic timeline.
氘是普氢较重的、稳定同位素。
Deuterium is a heavier and stable isotope of ordinary hydrogen.
铀（U）元素就是一个很好的例子。天然铀有两种同位素；较轻的负235可以裂变，较重的铀238则不会裂变。
The prime example is the element uranium (U), which occurs naturally as two isotopes-the lighter, fissionable U-235 and the heavier, non-fissionable U-238.
通过测量一缕头发中较重的氢氧同位素的比例，科学家们可以构建一个地理学的时间轴。
S. By measuring the proportion of heavier hydrogen and oxygen isotopes along a strand of hair, scientists can construct a geographic timeline.
通过测量一缕头发中较重的氢氧同位素的比例，科学家们可以构建一个地理学的时间轴。
S. By measuring the proportion of heavier hydrogen and oxygen isotopes along a strand of hair, scientists can construct a geographic timeline.
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