远在公元11世纪,中国已使用火药.Gunpowder was used in China as far back as the 11 th century.在14世纪上半叶,火药传入欧洲.Gunpowder was introduced into Europe during the first half of the 14 th century.他们正在把火药和武器搬进前舱.They are putting the powder and...
Today many radioisotopes are produced using the particle accelerator called a cyclotron.今天许多放射性同位素是用被称为回旋加速器的粒子加速器来制造的.The cyclotron frequency can also be derived by an elementary argument.回转频率也可以通过浅显的论证导出来.How well is t...