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我国封建社会文书工作的确立时期是______
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The Earth"s daily clock, measured in a single revolution, is twenty-four hours. The human clock,【C1】______, is actually about twenty-five hours. That" s 【C2】______ scientists who study sleep have determined from human subjects who live for several weeks in observation chambers with no【C3】______of day or night. Sleep researchers have【C4】______other surprising discoveries as well.We spend about one-third of our lives asleep, a fact that suggests sleeping, 【C5】______eating and breathing, is a fundamental life process. Yet some people almost never sleep, getting by on as 【C6】______as fifteen minutes a day. And more than seventy years of【C7】______ into sleep deprivation, in which people have been kept 【C8】______for three to ten days, has【C9】______ only one certain finding: Sleep loss makes a person sleepy and that" s about all; it causes no lasting ill【C10】______ . Too much sleep, however, may be 【C11】______ for you. These findings【C12】______some long-held views of sleep, and they【C13】______questions about its fundamental purpose in our lives. In【C14】______, scientists don"t know just why sleep is necessary. Some scientists think sleep is more the result of evolutionary habit than【C15】______actual need, Animals sleep for some parts of the day perhaps because it is the 【C16】______thing for them to do: it keeps them【C17】______ and hidden from predators; it"s a survival tactic. Before the advent of electricity, humans had to spend at least some of each day in【C18】______and had little reason to question the reason or need for【C19】______. But the development of the electroencephalograph and the resulting discovery in 1937 of dramatic【C20】______ in brain activity between sleep and wakefulness opened the way for scientific inquiry in the subject. 【C13】
公文同图书、情报资料、通讯报道以及一般文章作品的显著区别是______
1912年元月，南京临时政府内务部奉大总统令，颁发了______
我国古代实行公文统一用纸，始于东晋末年的______
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