短语词组短语parabola mass -spectrograph 抛物线质谱仪mass spectra spectrograph 质谱仪mass -spectrograph velocity-focusing 速度聚焦质谱仪velocity -focusing mass-spectrograph 速度聚焦质谱仪double -focusing mass-spectrograph 双聚焦质谱仪 返回 mass spectrograph