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【单选题】
When we see well, we do not think about our eyes very often. It is only when we cannot see perfectly that we realize how important our eyes are. People who are nearsighted can only see things that are very close to their eyes. Everything else is not so clear. Many people who do a lot of close work, such as writing, reading and sewing, become near sighted. Then they have to wear glasses in order to see distant (远处的) things clearly'. People who are nearsighted suffer from just the opposite problem. They can see things that are far away, but they have difficulty in reading a book unless they hold it at arm's length. If they want to do much reading, they must get glasses, too. Other people do not see clearly because their eyes are not exactly the right shape. They have what is called astigmatism (散光). This, too, can be corrected by glasses. Some people's eyes become cloudy because of cataracts (白内障). Long ago these people often became blind. Now, however, it is possible to operate on the cataracts and remove them. Having two good eyes is important for judging distances. Each eye sees things from a slightly different angle (角度). To prove this to yourself, look at an object out of one eye then look at the same object out of the other eye. You will find the object's relation to the background (背景) and other things around it has changed. The difference between these two different eye views helps us to judge how far away an object is. People who have only one eye cannot judge distance as people with two eyes. We should take good care of our eyes ______.
A.
only when we cannot see perfectly
B.
only when we can see well
C.
even if we can see well
D.
only when we realize how important our eyes are
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【简答题】根据承载情况不同,轴可分为____、____、____。按轴线形状不同,轴可分为____、____、____。工作时仅承受弯矩而不传递转矩的轴是____。工作时既承受弯矩又承受转矩的轴是____。只传递转矩而不承受弯矩的轴是____。
【单选题】根据传动轴承受载荷的情况,下列说法正确的是()。
A.
只承受弯矩
B.
及承受弯矩又承受转矩
C.
只承受转矩不受弯矩或受很小弯矩
D.
既不承受弯矩又不承受转矩
【简答题】椎骨由位于前方的①___________________和后方的②___________________—组成。相邻的椎上、下切迹围成③___________________,有④___________________通过。
【单选题】在工作中只能承受转矩而不能承受弯矩的轴是()。
A.
心轴
B.
阶梯轴
C.
传动轴
D.
转轴
【单选题】半浮式半轴支承的承受载荷情况是( )
A.
只承受转矩
B.
只承受弯矩
C.
内端承受弯矩,外端承受转矩
D.
内端承受转矩,外端承受弯矩
【简答题】椎骨最前方是( )
【简答题】每块椎骨由前方的()和后方的()构成。
【简答题】椎骨由前方的________和后方的________组成,两者共同围成________。
【判断题】溶液的透光率越大,表示物质对光的吸收越小
A.
正确
B.
错误
【简答题】椎骨由位于前方的___和后方的___组成。
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