当晶体管处于放大状态时,其特征是:发射结处于()偏置,集电结处于反向偏置。
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某急性心梗病人发病14小时后,进行LD同工酶检查AMI时,LD最早出现变化的间时为()
A. 2~4小时
B. 4~8小时
C. 8~12小时
D. 12~24小时
E. 24小时以上
Evaluate the CREATE TABLE statement: CREATE TABLE products (product_id NUMBER (6) CONSTRAINT prod_id_pk PRIMARY KEY, product_name VARCHAR2 (15)); Which statement is true regarding the PROD_ID_PK constraint?()
A. It would be created only if a unique index is manually created first.
B. It would be created and would use an automatically created unique index.
C. It would be created and would use an automatically created nonunique index.
D. It would be created and remains in a disabled state because no index is specified in the command.
恶意呼叫识别(MCI):移动用户可要求在网络中识别并记录一个不希望的呼入源()
A. 正确
B. 错误
晶闸管导通的条件是在阳极和阴极加上正向电压,然后给控制极加上一个触发电压。
A. 正确
B. 错误