The critical current density of pure MgB2 is comparable to that of triniobium tin at low magnetic fields but falls off much more rapidly at higher fields.是什么意思_The critical current density of pure MgB2 is comparable to that of triniobium tin at low magnetic fields but falls off much more rapidly at higher fields.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句