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用555定时器组成施密特触发器,电源电压为5V,当5号引脚控制电压端外接4V电压时,回差电压为 。
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【简答题】计算机系统总线经历了怎样的一个发展历程?
【简答题】5 What idea did Smith learn from his military experience? How did he relate the idea to his business later?
【简答题】病历分析 [病历摘要]男性，3岁，发热、呕吐、腹泻2天。患儿2天前开始发热39℃，然后开始吐泻，每日呕吐2～3次，呕吐为非喷射性，吐出物为胃内容物，大便10余次／日，为黄色稀水便，蛋花汤样，无黏液及脓血，无特殊臭味，偶有轻咳。发病后食欲差，今日8小时以来无尿。急性病容，精神萎靡，烦躁，全身皮肤无黄染，未见皮疹，皮肤弹性差，眼窝明显凹陷。心率138次／分，律齐，心音低钝，肺（-），腹稍胀，肝肋下1c...
【单选题】-Has Sam finished his homework today, Anne? -I have no idea. But he ________ it this morning. [ ]
A.
did
B.
had done
C.
was doing
D.
had done
【简答题】广西旅游业的发展大致经历了______、______、______三个阶段的发展历程。
【单选题】When did Jack begin to try out his idea?
A.
As soon as he got his taxi license.
B.
When he arrived in the city
C.
When he was a clean-up man for the taxi company
D.
After he made friends with the author
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