下列运算正确的是( ) A.2-3=-6 B.4=±2 C.a2•a3=a5 D.3a+

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问题:

下列运算正确的是(  )
A.2-3=-6B.
4
=±2
C.a2•a3=a5D.3a+2a=5a2
考点:有理数的乘方同类项零指数幂(负指数幂和指数为1)算术平方根
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某校用维修专款更换一批课桌椅,这些款若只买课桌恰好可以买240张;若只买课椅恰好可以买400把,那么,用这批专款可以买______套课桌椅(一张桌子一把椅子).

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在易斜或急倾斜地层中钻进,以粗径加重钻具为导向管,粗径钻具与钻孔的环状间隙应小于()mm

A、5

B、10

C、15

D、20

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下列哪项不是判断风湿活动的指标()

A.发热、乏力

B.红细胞沉降率增快

C.CRP增高

D.ASO升高

E.心电图示P-R间期延长

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Attempts to understand the relationship between social behavior and health have their origin in history. Dubos (1969) suggested that primitive humans were closer to the animals (1) they, too, relied’upon their instincts to stay healthy. Yet some primitive humans (2) a cause and effect relationship between doing certain things and alleviating (3) of a disease or (4) the condition of a wound. (5) there was so much that primitive humans did not (6) the functioning of the body, magic became an integral component ofthe beliefs about the causes and cures of heath (7) Therefore it is not (8) that early humans thought that illness was caused (9) evil spirit. Primitive medicines made from vegetables or animals were invariably used in combination with some form of ritual to (10) harmful spirit from a diseased body.

One of the. earliest (11) in the Western world to formulate principles of health care based upon rational thought and (12) of supernatural phenomena is found in the work of the Greek physician Hippocrates. The writing (13) to him has provided a number of principles underiying modern medical practice. One of his most famous (14) , the Hippocratic Oath, is the foundation of contemporary medical ethics.

Hippocrates also argued that medical knowledge should be derived from a (15) of the natural science and the logic of cause and effect relationships. In this (16) thesis, On Air, Water, and Places, Hippocrates pointed out that human well-being is (17) by the totality of environmental (18) : living habits or lifestyle, climate, geography of the land, and the quality of air, and food. (19) enough, concerns about our health and the quality of air, water, and places are (20) very much written in twentieth century.

19()

A.Interesting

B.Appealing

C.Demanding

D.Exaggerating

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怎样测量汽轮机的转子推力间隙?

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