生物安全柜(biosafety cabinet;biological safety cabinet):
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In characterization, the_______ method of telling relies on exposition and direct commentary by the author, while the other, _________ dramatic method, involves making the characters reveal themselves directly through their dialogues and actions.
串联型稳压电路通过引入电压负反馈来稳定输出电压。
A. 对
B. 错
要获得+9V的稳定 ,集成三端稳压器应选择( )
A. CW7812
B. CW7809
CW7909
D. CW7805
三端集成稳压器W117的泄放电阻一般取()Ω。
A. 300Ω
B. 250Ω
C. 240Ω