物理学
无摩擦环境
Maglev trains use magnets to provide a frictionless environment, so theoretically, it should be possible to get one of them to the roughly 20, 000 mph required to launch an object into orbit.
FORBES: Connect
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。