求如图所示的交变电流的有效值,其中每个周期的后半周期的图象为半个周期的正弦曲线(

题型:选择题

问题:

求如图所示的交变电流的有效值,其中每个周期的后半周期的图象为半个周期的正弦曲线(   )

A.5A

B.5A

C.5/2A

D./2A

考点:交变电流的周期和频率交变电流的最大值、有效值、瞬时值和平均值
题型:选择题

根据短文内容及首字母提示,补全空格内单词,使短文完整、通顺。

Peter was the best table tennis player in his school and hardly(几乎不) ever lost a match. He hated losing anything. When he w__小题1:_, he would feel really good. If he lost, he would feel terrible. It seemed to Peter that losing was the w__小题2:_ thing in the world.

A new kid, Albert, came to Peter’s school. He was good at table tennis, too. Soon there would be a match b___小题3:_ Peter and Albert.. Peter worked hard to get ready for the match, but Albert didn’t seem to think m__小题4: of it. When the match began, Albert was a real player. There was always a s__小题5:__ on his face, while Peter looked serious all the time. Peter thought it was so important to win the match t__小题6:__ he even wanted to cheat(舞弊), but he lost in the end.

“You played very well, Peter. I think we can play again sometime,” said Albert.

But Peter didn’t feel happy and couldn’t f__小题7:_ asleep that night .

One day, Peter saw Albert playing basketball. T__小题8:__ he lost again and again, the happy smile never left his face. Peter found Albert was great at table tennis but bad at basketball. However, he enjoyed b___小题9:___ of them.

Whether he won or lost the game, Albert enjoyed it. Peter came to realize that e__小题10:__ a game was much more important than winning or losing it. He felt happier than ever before.

题型:选择题

生后不久出现呕吐,吐物为黄绿色物,腹部X线平片可见腹腔钙化斑

A.胃食管反流

B.先天性幽门肥厚性狭窄

C.肠旋转不良

D.环状胰腺

E.肠梗阻型胎粪性腹膜炎

题型:选择题

一个长方形的长是5cm,宽是4cm,长和宽的比是______:______,写成百分比是______%,长比宽多______%,宽比长少______%,长占周长的______%,宽占周长的______%.

题型:选择题

关于梅毒的传播途径及传染性的描述中,错误的是()

A.95%通过性接触传染

B.未经治疗的患者,感染后1~2年内具有强传染性,随时间延长,传染性越来越小

C.患梅毒孕妇,在妊娠期内梅毒螺旋体通过胎盘及脐静脉感染胎儿,导致流产、早产和死胎或分娩胎传梅毒

D.未经治疗的梅毒妇女,病程超过4年,通过性接触无传染性,亦不易传给胎儿

题型:选择题

破伤风发作期最先出现的症状是( )

A.手足抽搐
B.颈项强直
C.苦笑面容
D.张口困难
E.角弓反张

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