原子中半径最小的壳层是A.K层B.L层C.M层D.N层E.O层

题型:单项选择题

问题:

原子中半径最小的壳层是

A.K层
B.L层
C.M层
D.N层
E.O层

考点:放射医学技师放射技师相关专业知识初级放射医学技师相关专业知识
题型:单项选择题

当碳原子的核外电子排布由转变为时,下列说法正确的是 [ ]

A.碳原子由基态变为激发态

B.碳原子由激发态变为基态

C.碳原子要从外界环境中吸收能量

D.碳原子要向外界环境中释放能量

题型:单项选择题

大约六千年前,古巴比伦的人们开始制作黏土代币作为交易的记录。不同形状的黏士代币表示不同的物品。当一次交易需要用到很多代币时,人们就用黏土把它们包裹起来,交易者用削尖的木棍在上面刻上不同的符号,用以表示里面包了些什么。后来一些人想到了更简洁的办法,只需简单地将符号刻在黏土上,就可以表示交易内容,这样就摆脱了烦琐的代币。于是文字被发明了,而这正是文明的开始。 这段文字主要介绍了

A.古巴比伦的货币发展史

B.古巴比伦文字是如何产生的

C.文字对文明发展的重要意义

D.古巴比伦人怎样进行商品交换

题型:单项选择题

关于热现象和热学规律,下列说法正确的是(  )

A.随着低温技术的发展,我们可以使温度逐渐降低,并最终达到绝对零度

B.根据热力学第二定律,热量不可能从低温物体传到高温物体

C.理想热机可以把从单一热源吸收的热量全部转化为机械能,而不引起其他变化

D.任何机械都不可能从单一热源吸收热量并把它全部用来做功,而不引起其他变化

题型:单项选择题

张大妈去超市二楼购物,如果人不走任由电梯载上需要10秒钟,电梯不动张大妈自己走到二楼需要15秒钟,买完东西后张大妈下楼,如果她下楼的速度是上楼的两倍,但手中提了东西后速度又是空手时的,则张大妈在电梯运行的情况下走到一楼需要多少秒钟()

A.10

B.6

C.5

D.4

题型:单项选择题

(A)

Around the world more people are taking part in dangerous sports and activities. Now, there are people who look for an immediate excitement from a risky activity which may only last a few minutes or even seconds.

I would consider bungee jumping (蹦极) to be a good example of such an activity. You jump from a high place 200 meters above the ground with an elastic (弹性的) rope tied to your feet. You fall at up to 150 kilometers an hour until the rope stops you from hitting the ground. It is said that about 2 million people around the world have now tried bungee jumping. Other activities which most people would say are as risky as bungee jumping include jumping from tall buildings and diving into the sea from the top of high cliffs.

Why do people take part in such activities as these Some psychologists suggest that it is because life in modem societies has become safe and boring. Not very 10ng ago, people’s lives were constantly in danger. They had to go out and hunt for food, diseases could not easily be cured, and life was a continuous battle for survival.

Nowadays, according to many people, life offers little excitement. They live and work in quite safe conditions: they buy food in shops, and there are doctors and hospitals to look after them if they become ill. The answer for some of these people is to look for danger in activities such as bungee jumping.

The writer of the passage has a () attitude towards dangerous sports.

A. positive

B. negative

C. neutral

D. critical

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