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当前学科：材料科学与工程
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为什么发光材料中一般含有的金属原子是Fe.Co.Ni等？
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关于恒定总流能量方程的应用条件，下列说法正确的是()。
Questions 26 to 30 are based on the following passage. Exercise is one of the few factors with a positive role in long-term maintenance of body weight. Unfortunately, that message has not gotten through to the average American, who would rather try switching to “light” beer and low-calorie bread than increase physical exertion. The Centers for Disease Control, for example, found that fewer than one-fourth of overweight adults who were trying to shed pounds said they were combining exercise with their diet. In rejecting exercise, some people may be discouraged too much by caloric-expenditure charts: for example, one would have to briskly walk three miles just to work off the 275 calories in one delicious Danish pastry (小甜饼). Even exercise professionals concede half a point here. “Exercise by itself is a very tough way to lose weight,” says York Onnen, program director of the President’s Council on Physical Fitness and Sports. Still, exercise’s supporting role in weight reduction is vital. A study at the Boston University Medical Center of overweight police officers and other public employees confirmed that those who dieted without exercise regained almost all their old weight, while those who worked exercise into their daily routine maintained their new weight. If you have been sedentary (极少活动的) and decide to start walking one mile a day, the added exercise could burn an extra 100 calories daily. In a year’s time, assuming no increase in food intake, you could lose ten pounds. By increasing the distance of your walks gradually and making other dietary adjustments, you may lose even more weight. Some people dislike exercise because （）
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两周龄男婴，出现呕吐，喷射性，并逐渐加重，患儿体重减轻，但食欲良好。应首先考虑的疾病是（）
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基尼系数，是国际上用来综合考察居民内部收入分配差异状况的一个重要分析指标。基尼系数的数值越低，表明财富在社会成员之间的分配越均匀。下列做法中有利于降低基尼系数的是（） ①保护居民合法的财产性收入 ②提高务工人员最低工资标准 ③个人收入按超额累进税率缴税 ④健全生产要素按贡献参与分配制度