Any of a series of chemically similar, radioactive elements with atomic numbers ranging from 89 ( actinium ) through 103 ( lawrencium ).锕类任何化学性质相似, 原子序数在89 ( 锕 ) 与103 ( 铹 ) 之间变化的放射性元素.The extraction mechanism and separat...
It is IBM appoints new presiding apparitor formally firstly.其一是IBM正式任命新的首席执行官.Charles II appoints John Flamsteed to the new post of Astronomer Royal.查理二世任命约翰·弗兰斯蒂德去新成立的皇家天文学家任职.In place of the former president the Mayor ...