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我国超高频辐射卫生标准(GB10437—89)规定连续波
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慢性放射性皮肤损伤的参考剂量阈值是
By far the most common difficulty in study is simple failure to get down to regular concentrated work. This difficulty is much greater for those who do not work to a plan and have no regular routine of study. Many students muddle along, doing a hit of this subject or that, as the mood takes them, or letting their set work pile up until the last possible moment.Few students work to a set time-table. They say that if they did construct a timetable for themselves they would not keep to it, or would have to alter it constantly, since they can never predict from one day to the next what their activities will be. No doubt some temperaments take much more kindly to a regular routine than others. There are many who shy away from the self-regimentatign of a weekly time-table, and dislike being tied clown to a definite programme of work. Many able students claim that they work in cycles. When they become interested in a topic they work on it intensively for three or four days at a time. On other days they avoid work completely. It has to be confessed that we do not fully understand the complexities of the motivation to work. Most people over 25 years of age have become conditioned to a work routine, and the majority of really productive workers set aside regular hours for the more important aspects of their work. The "tough-minded" school of workers is usually very contemptuous of the idea that good work can only be done spontaneously, under the influence of inspiration.Those who believe that they need only work and study as the fit takes them have a mistaken belief either in their own talent or in the value of "freedom". Freedom from restraint and discipline leads to unhappiness rather than to "self-expression" or "personality development". Our society insists on regular habits, timekeeping and punctuality, and whether we like it or not, if we mean to make our way in society we have to comply with its demands. Those workers with strict views on work （）
危险系数只适用于评价符合线性假说的______效应
The typical pre-industrial family not only had a good many children, but numerous other dependents as well — grandparents, uncles, aunts and cousins. Such "extended" families were suited for survival in slow paced (47) societies. But such families are hard to (48) . They are immobile. Industrialism demanded masses of workers ready and able to move off the land in pursuit of jobs, and to move again whenever necessary. Thus the extended family (49) shed its excess weight and the so- called "nuclear" family emerged — a stripped-down, portable family unit (50) only of parents and a small set of children. This new style of family, far more (51) than the traditional extended family, became the standard model in all the industrial countries. Super-industrialism, however, the next stage of eco-technological development, (52) even higher mobility. Thus we may expect many among the people of the future to carry the streamlining process, a step further by remaining children, cutting the family down to its more (53) components, a man and a woman. Two people, perhaps with matched careers, will prove more efficient at navigating through education and social status, through job changes and geographic relocations, than the ordinarily child-cluttered family. A (54) maybe the postponement of children, rather than childlessness. Men and women today are often torn in (55) between a commitment to career and a commitment to children. In the future, many (56) will side aside this problem by deferring the entire task of raising children until after retirement. A. transplant B. solution C. gradually D. transport E. elemental F. conflict G. continually H) mobile I) couples J) agricultural K) including L) compromise M) requires N) primary O) consisting
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