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以硅胶为固定相的TLC按作用机制属于
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中国药典(2005版)收载的用气相色谱法测定含量的药物是
中国药典规定“精密称定”时，系指重量应准确在所取重量的
There was a time when parents who wanted an educational present for their children would buy a typewriter, a globe or an encyclopedia set.Now those (21) seem hopelessly old-fashioned: this Christmas, there were a lot of (22) computers under the tree. (23) that computers are their key to success, parents are also frantically insisting that children (24) taught to use them on school—as early as possible. The problem for schools is that when it (25) computers, parents don’t always know best. Many schools are (26) parental impatience and are purchasing hardware without (27) educational planning, so they can say, OK, we’ve moved into the computer age. Teachers (28) themselves caught in the middle of the problem — between parent pressure and (29) educational decisions.Educators do not even agree (30) how computers should be used. A lot of money is going for computerized educational materials (31) research has shown can be taught (32) with pencil and paper. Even those who believe that all children should (33) to computer warn of potential (34) to the very young.The temptation remains strong largely because young children (35) so well to computers. First graders have been (36) willing to work for two hours on math skills. Some have an attention span of 20 minutes.(37) school, however, can afford to go into computing, and that creates (38) another problem: a division between the have’s and havenot’s. Very few parents ask (39) computer instruction in poor school districts, (40) there may be barely enough money to pay the reading teacher. 26().
编制工程结算时，计算和确定一个规定计量单位的分项工程或结构构件的人工、材料、机械台班耗用量的标准是( )。
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