三级管工作在放大区,要求()
A. 发射结正偏,集电结正偏
B. 发射结正偏,集电结反偏
C. 发射结反偏,集电结正偏
D. 发射结反偏,集电结反偏
_is the first nation to manufacture true porcelain in the world and has been recognized as “the home of porcelain”()
A. Japan
B. France
China
D. Greece
Since the founding of the People’s Republic of China, the country has conducted ____ population censuses()
A. 4
B. 5
C. 6
D. 7
理想气体组成的封闭系统吸热后其温度必定增加,其比熵也必定增加()