网友您好， 请在下方输入框内输入要搜索的题目：
题目内容
（请给出正确答案）
名词解释题
阳离子交换
参考答案
参考解析
解析：
暂无解析
更多 “名词解释题阳离子交换” 相关考题
考题
单选题Questions 21 to 25 are based on the following passage.
Lead deposits, which accumulated in soil and snow during the 1960’s and 70’s, were primarily the result of leaded gasoline emissions originating in the United States. In the twenty years that the Clean Air Act has mandated unleaded gas use in the United States, the lead accumulation worldwide has decreased significantly.
A study published recently in the journal Nature shows that air-borne leaded gas emissions from the United States were the leading contributor to the high concentration of lead in the snow in Greenland. The new study is a result of the continued research led by Dr. Charles Boutron, an expert on the impact of heavy metals on the environment at the National Center for Scientific Research in France. A study by Dr. Boutron published in 1991 showed that lead levels in arctic (北极的) snow were declining.
In his new study, Dr. Boutron found the ratios of the different forms of lead in the leaded gasoline used in the United States were different from the ratios of European, Asian and Canadian gasolines and thus enabled scientists to differentiate (区分) the lead sources. The dominant lead ratio found in Greenland snow matched that found in gasoline from the United States.
In a study published in the journal Ambio, scientists found that lead levels in soil in the Northeastern United States had decreased markedly since the introduction of unleaded gasoline.
Many scientists had believed that the lead would stay in soil and snow for a longer period.
The authors of the Ambio study examined samples of the upper layers of soil taken from the same sites of 30 forest floors in New England, New York and Pennsylvania in 1980 and in 1990. The forest environment processed and redistributed the lead faster than the scientists had expected.
Scientists say both studies demonstrate that certain parts of the ecosystem (生态系统) respond rapidly to reductions in atmospheric pollution, but that these findings should not be used as a license to pollute.
It can be inferred from the last paragraph that scientists （）A
are puzzled by the mystery of forest pollutionB
feel relieved by the use of unleaded gasolineC
still consider lead pollution a problemD
lack sufficient means to combat lead pollution
考题
多选题货物贸易项下，因汇路不畅需要使用外币现钞结算的，办理外币现钞结汇时，应审核（）。A外汇局《登记表》B出口合同C出口货物报关单D经海关签章的携带外币现钞入境申报单正本（超过入境申报金额）
考题
单选题关于基层材料性质，下列说法正确的是：（ ）。A
石灰土、水泥稳定土均有良好的板体性，因此可用作高等级路面的基层。B
石灰土水稳性、抗冻性较水泥土差，但抗裂性能较水泥土强。C
二灰稳定土的力学性能、板体性、水稳性及抗冻性较石灰土强，可用作高等级路面的基层。D
二灰稳定土粒料强度高，收缩小，板体性强，可用于高等级路面的基层
考题
判断题为减少机械传动部件的扭矩反馈对电机动态性能的影响，机械传动系统的基本固有频率应低于电气驱动部件的固有频率的2~3倍，同时，传动系统的固有频率应接近控制系统的工作频率，以免系统产生振荡而失去稳定性。A
对B
错
考题
单选题男性，18岁，头部被菜刀砍伤已2天余，伤口6cm，裂开，脓性分泌物较多.处理方法是（）A
彻底清创并缝合B
清创处理伤口不缝合C
控制感染，定期更换敷料D
清创、缝合并放置引流E
清创、湿敷、包扎
考题
单选题下列选项中不属于综合实践活动课程实施过程的是（）。A
组织复习，认真考试B
问题牵引，有问必答C
整体规划，系统设计D
选取课题，开展研究
热门标签
最新试卷