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...
Formal, exact and obstinate, he was also cold, suspicious, touchy and tactless.严肃、严谨、倔强的他同时又冷漠、多疑、敏感、不会变通。This successor was J . F . McLennan, the exact opposite of hispredecessor.这个后继人,就是约-弗-麦克伦南, 他和他的先驱者正好相反.I hadn...
Receding gums can be the result of disease or simply incorrect brushing.牙龈萎缩可能是疾病导致的，也可能仅仅是错误的刷牙方式引起的。Thoroughly brush teeth and gums twice daily.每天两次彻底刷净牙齿和牙龈.A bad tooth may cause an abscess on the gums.一颗病牙可使牙床脓肿....
There was no doubting the animal magnetism of the man.毫无疑问，这个男人身上透着一种野性魅力。There is no doubting them now.现在无法怀疑他们。I am a dark, self - destructive, happiness - doubting, unforgivable man.我是个阴郁, 自我 毁灭, 怀疑快乐, 不可饶恕的人....