为什么成为明星?因为少见，千分之几的机率！
Why become a star? because the rare chance of a few thousandths!
氖是空气中的稀有气体，只占空气体积的千分之几。
Neon, a rare gas in the air, takes only fractional percentage point of the volume.
用电生醌分别进行毫克量亚钛和二价钒的库仑滴定，误差为千分之几。
Coulometric titrations of milligram quantities of titanous ion and hypovanadous ion give errors less than 1 per cent.
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