【判断题】在图( a )所示锯齿波 -矩 形波发生器中,已知 A 1 、 A 2 均为理想运算放大器,其输出电压的两个极限值为 ± 12V ; 二极管的伏安特性如图( b )所示;设振荡周期为 T ,一个周期内 u O1 为高电平的时间为 T 1 ,占空比= T 1 / T 。(温馨提示,以下9个问题的电路图相同,请先copy电路以便答题) 判断以下结论是否正确: R 2 阻值增大,输出电压 u O2 的幅...
【单选题】听力原文:London: Researchers say women increase the risk of getting breast cancer with every alcoholic drink they consume. The study by Cancer Study UK says smoking, which causes 15 other types of the dis...
A.
Smoking cigarette causes breast cancer among women.
B.
Alcoholic consumption may lead to more cases of breast cancer among women.
C.
150,000 women suffer the disease of breast cancer in Britain.
D.
Alcoholic consumption causes more than 15 types of diseases.