Tritium is one of the mildest radioactive isotopes.氚是最和缓的放射性同位素之一.More reactive are the heavier isotopes of hydrogen, deuterium and tritium.更为活跃的是氢的较重同位素, 氘和氚.Tritium has a half - life of 12.4 years.氚的半衰期为12.4年,地球形成时的氚早已...
They are not second - order approximations, but are exact for any amount of deformation.它们不是二次近似, 而是对任何变形量都成立的精确表达式.We do not have the true figures so we will have to make some approximations.我们没有真实的数字，因此只能作些粗略的估计。There ...