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Natural MedicinesSince earliest days, humans have used some kinds of medicines. We know th

Natural Medicines

Since earliest days, humans have used some kinds of medicines. We know this because humans have survived. Ancient treatments for injury and disease were successful enough to keep humans from dying out completely.

They were successful long before the time of modern medicine. Before the time of doctors with white coats and shiny (发亮的) instruments. Before the time of big hospitals with strange and wonderful equipment.

Many parts of the world still de not have university-educated doctors. Nor do they have expensive hospitals. Yet injuries are treated. And diseases are often cured. How? By ancient methods. By medicines that might seem mysterious, even magical (有魔力的). Traditional medicines are neither mysterious nor magical, however.

Through the centuries, tribal (部族的) medicine men experimented with plants. They found many useful chemicals in the plants. And scientists believe many of these traditional medicines may provide the cure for some of today's most serious diseases.

Experts say almost 80% of the people in the world use plants for health care. These natural medicines are used not just because people have no other form. of treatment. They are used because people trust them. In developed areas, few people think about the source of the medicines they buy in a store. Yet many widely-used medicines are from ancient sources, especially plants. Some experts say more than 25% of modern medicines come, in one way or another, from nature.

Scientists have long known that nature is really a chemical factory. All living things contain chemicals that help them survive. So scientists' interest in traditional medicine is not new. But it has become an urgent concern. This is because the earth's supply of natural medicines may be dropping rapidly.

The passage indicates that ancient treatments for injury and disease were

A.much more successful than modern ones.

B.successful enough for humans to survive.

C.successful in all cases.

D.of little help to humans.

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第1题

液体受热越多,温度越高,蒸发得就会()

A.不变

B.越快

C.越慢

D.停止

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第2题

易燃液体的蒸气压越大,蒸发速度()。A.越快B.越慢C.与蒸气压无关D.不确定

易燃液体的蒸气压越大,蒸发速度()。

A.越快

B.越慢

C.与蒸气压无关

D.不确定

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第3题

液体的初始温度越高,其燃烧速度()。A.越快B.越慢C.与初始温度无关D.不确定

液体的初始温度越高,其燃烧速度()。

A.越快

B.越慢

C.与初始温度无关

D.不确定

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第4题

关于油罐内油品蒸发速度的说法,下列表述错误的是()。

A. 油品的温度越高,蒸发速度越大

B. B.气相中油品蒸气浓度越高,蒸发速度越低

C. C.油品的表面面积越大,蒸发速度越快

D. D.油品的相对密度越小,蒸发速度越小

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第5题

下列有关影响蒸发因素的表述中错误的是()。

A.液面外蒸汽的浓度越高蒸发越快

B.液体蒸发的面积越大蒸发越快

C.液体表面的压力越大蒸发越快

D.液体的沸点越高越大蒸发越快

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第6题

蒸发越快油品损失越小,压力越高,蒸发越慢损失越大。()
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第7题

液体的蒸发速度取决于温度,温度越高速度越快,当温度低至一定程度,液体就停止了蒸发。()
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第8题

可燃性液体的饱和蒸汽压()则蒸发速度()

A.越大;越快

B.越大;越慢

C.越小;越快

D.变化;不变

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第9题

蒸发和氧化与空气的接触情况有关,油品接触空气的面积越大,空气流通越快,则()。

A.蒸发越快,但氧化越慢

B.蒸发越慢,但氧化越快

C.蒸发和氧化都越慢

D.蒸发和氧化都越快

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第10题

在液体表面进行的汽化现象叫蒸发。温度越高蒸发速度越快()
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