【原子能】半衰期〔放射性同位素分裂[从生物体中排出]一半量的时间〔也作 half life 或 half life period〕〕。
the time required for something to fall to half its initial value (in particular, the time for half the atoms in a radioactive substance to disintegrate) 同义词：half life,
Half-life (t?) is the time required for a quantity to fall to half its value as measured at the beginning of the time period. In physics, it is typically used to describe a property of radioactive decay, but may be used to describe any quantity which follows an exponential decay.
例句与用法
1.
It has a half-life of about 41/2 billion years . 它的半衰期大约为45亿年。
2.
The half-life of francium is 22 minutes . 钫的半衰期是22分钟。
3.
Evolutionists have recently learned that groups of species also have what might be called a half-life . 进化论者最近发现生物属种也具有一种可以称为半死亡期的时期。
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