题目内容
为了防止或减轻房屋的正常使用条件下,由温差和砌体干缩引起的墙体竖向裂缝,对于装配整体式钢筋混凝土结构有保温层屋盖的砌体房屋伸缩缝的最大间距取以下何值？()
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Radiation is the greatest known danger to explorers in space. The unit of radiation is called "rem". Scientists have reason to think that a man can put up with far more radiation than 0. 1 rem without being damaged, the figure of 60 rems has been agreed on. The trouble is that it is extremely difficult to be sure about radiation damage--a person may feel perfectly well, but the cells of his or her sex organs may be damaged, and this will not be discovered until the birth of deformed children or even grandchildren Missions of the Apollo flights have had to cross belts of high radiation and, during the outward and return journeys, the Apollo crew accumulated a large amount of rems. So far, no dangerous amounts of radiation have been reported, but the Apollo missions have been quite short. We simply do not know yet how men are going to get on when they spend weeks and months.
According to the first paragraph, the atmosphere is essential to man in that ______.
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