粒子是从天然放射性蜕变得到的带正电的氦核。
Alpha particles are positively charged helium nuclei obtained from natural radioactive decay.
少数元素，其中有铀和钍，通过它们核的变化自然蜕变成较轻的元素。
A few elements, among them uranium and thorium, spontaneously disintegrate into lighter elements by chances.
少数元素，其中有铀和钍，通过它们核的变化自然蜕变成较轻的元素。
A few elements, among them uranium and thorium, spontaneously disintegrate into lighter elements by chances.
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