轻质活塞将一定质量的气体封闭在薄壁气缸内,活塞横截面积为S,气缸质量为m.开始时

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问题:

轻质活塞将一定质量的气体封闭在薄壁气缸内,活塞横截面积为S,气缸质量为m.开始时活塞处于气缸正中间,现用竖直向上的力提活塞使得气缸被提离地面,如图所示.当气缸内气体的压强为______时,气缸将获得最大加速度,气缸的最大加速度为______.(外界大气压强为P0

考点:牛顿第二定律气体的压强理想气体状态方程
题型:填空题

重度妊高征的产科处理,下述哪项是错误的()

A.孕<36周,经治疗病情好转而稳定,可继续妊娠 

B.孕>36周,积极治疗24~48小时症状改善,应考虑终止妊娠 

C.孕36周,经积极治疗24~48小时病情继续恶化,应继续积极治疗至病情稳定后终止妊娠 

D.子痫患者应积极治疗,控制抽搐6~12小时终止妊娠 

E.引产失败应剖宫产 

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Have you ever been ill? When you are ill, you must be unhappy because your body becomes hot, and there are pains all over your body. You don’t want to work, and you stay in bed, feeling very sad.

What makes us ill? It is germs(细菌). Germs are everywhere.  They are very small and you can’t find them with your eyes, but you can see them with a mi­croscope. They are very very small and there could be hundreds of them on a very small thing.

Germs are always found in dirty water. When we look at dirty water under the microscope, we shall see them in it. So your father and mother will not let you drink dirty water.

Germs aren’t found only in water. They are found in air  and dust. If you cut your finger, if some of the dust from the floor goes into the cut(割开处), some of the germs would go into your finger. Your finger would become big and red, and you will have much pain in it. Sometimes the germs would go into all of your body, and you would have pain everywhere.

56. Which of the following is true?

A. If things are very very small, they are germs.

B. If things can’t be seen, they must be germs.

C. Germs are only in dirty water.

D. Germs are everywhere around us.

57. What is a microscope used for?

A. Making very very small things look much bigger.

B. Making very big things look much smaller.

C. Helping you read some newspapers.

D. Helping you if you can’t see things clearly.

58. Why don’t your parents let you drink dirty water?

A. You haven’t looked at it carefully.

B. Water can’t be drunk in this way.

C. There must be lots of germs in it.

D. Water will make you ill.

59. Which of the following is not true?

A. Germs can be found both in water and in the air.

B. Germs can go into your finger if it is cut.

C. If your temperature is not OK, there must be germs in your body.

D. If your finger isn’t cut, there aren’t any germs on it.

60. What’s the main idea of the passage?

A. Germs may make us ill.    B. Germs are in dirty water.

C. Don’t drink dirty water.    D. Take care of your fingers.

题型:填空题

这里是西方文明的发源地,也是奥林匹克运动的摇篮。“这里”指的是

A.古埃及

B.古巴比伦

C.古希腊

D.古罗马

题型:填空题

吃过多的动物性蛋白质食品会增加心脏病、癌症和肥胖等发生的危险性。

题型:填空题

研究者对领导有效性进行了广泛而深入的研究,其成果归结起来有()。

A.特质理论

B.行为理论

C.民主理论

D.参与理论

E.权变理论

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