Either of two decay products of thorium,mesothorium I,an isotope of radium,or mesothorium II,an isotope of actinium.是什么意思_Either of two decay products of thorium,mesothorium I,an isotope of radium,or mesothorium II,an isotope of actinium.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句