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2002北航考博英语真题阅读理解及其答案
中国考博辅导首选学校
2002北航考博英语真题阅读理解及其答案
Technically, any substance other than food that alters our bodily
or mental functioning is a drug. Many people mistakenly believe the
term drugrefers only to some sortofmedicine or an illegalchemical
taken by drug addicts. They dont realize that familiar substances
such as alcohol and tobacco are also drugs. This is why the more
neutral term substance is now used by many physicians and
psychologists. The phrase substance abuse is often used instead of
drug abuse tomake clear that substances such as alcohol and tobacco
can be just as harmfully misused as heroin and cocaine.
We live in a society in which the medicinal and social use of
substances (drugs)ispervasive: anaspirin toquietaheadache, some
wine to be sociable, coffee to get going in the morning, a cigarette
for the nerves. When do these socially acceptable and apparently
constructive uses of a substance become misuses? First of all, most
substances taken in excess will produce negative effects such as
poisoning or intense perceptual distortions. Repeated use of a
substancecanalso leadtophysicaladdictionorsubstancedependence.
Dependence ismarked first by an increased tolerance, with more and
moreofthesubstancerequiredtoproducethedesiredeffect,andthen
by the appearance of unpleasant withdrawal symptoms when the
substance is discontinued.
Drugs (substances) that affect the central nervous system and
alter perception, mood, and behavior are known as psychoactive
中国考博辅导首选学校
substances. Psychoactive substances are commonly grouped according
to whether they are stimulants, depressants, or hallucinogens.
Stimulants initiallyspeeduporactivatethecentralnervous system,
whereas depressants slow it down. Hallucinogens have their primary
effectonperception, distortingand altering it inavariety ofways
including producing hallucinations. These are th
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