masking level difference(双耳)掩蔽级差 mean lethal dose平均致死量 minimal lethal dose最小致死量 mean lung dose平均肺剂量 mesencephalicus lateralis dorsalis中脑背外侧 medical laser diffractometer医用激光衍射仪 mixed liver disease混合型肝病 minimal lesion disease轻微病变性疾病