晶闸管直流斩波器的换流方式有()和电流换流两种。
参考答案:电压换流
Jay Chow's __________is so beautiful that most young people like his songs.[ ]
A. sound
B. whisper
C. noise
D. voice
蛋白质生物合成的抑制剂是
A.卡那霉素
B.甲氨蝶呤
C.利福霉素
D.氮杂丝氨酸