一位牧民计划用篱笆为他的马群围一个面积为1600米2的矩形牧场,由于受自然环境的

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问题:

一位牧民计划用篱笆为他的马群围一个面积为1600米2的矩形牧场,由于受自然环境的限制,矩形的一边不能超过a米,求用最少篱笆围成牧场后矩形的长和宽.

考点:指数函数模型的应用对数函数模型的应用
题型:解答题

关于热导池检测器的使用,下列叙述中错误的是()。

A、使用时热导池要置于恒温箱中

B、热导池检测器温度应高于或和柱温相近,以防止样品在热导池内冷凝,沾污热导池

C、在热丝接通电源之后再通入载气

D、工作完毕要先停电源,再关载气

题型:解答题

Part 1


·Read the fllowing passages, eight sentences have been removed from the article.
·For each gap (1-8) mark one letter (A-H) on the Answer Sheet.
·Do not mark any letter twice.
There’s a story in Texas about the rancher who complained when a well driller found oil instead of the water he had been sent to look for. "Cattle can’t drink that stuff!" the rancher cried.
That story is no longer funny. We are short of both oil and water, but the water shortage is worse. (1) And we are using water a great deal faster than it is being replaced. The replacement rate is dependent on rainfall (sometimes in the form of snow) to resupply rivers, lakes, and ground water. (2) Worse, droughts are occurring more frequently and are increasing in severity, not only in the United States but also abroad.
Even without droughts, rainfall is insufficient to maintain a balance. (3) So much water has been taken from the Colorado River by Arizona and California that Mexico has complained that those states have exceeded the U.S. share under a 1944 treaty on water-sharing. Southern Californians also have elaborated arrangements to transport water from the Pacific North west, which has it in abundance, to their area, which doesn’t have nearly enough to support its population. (4)
Short of a fanciful solution, the U.S. has two broad options, neither pleasant. We can conserve or we can produce. The former is inconvenient or worse: less irrigation (and thus less food), fewer swimming pools golf courses, and green lawns. (5) In the quantities necessary, this would probably require nuclear power. It is technically feasible, but expensive, and was considered 30 years ago as a joint U.S.-Mexican project in the Gulf of California to alleviate the Colorado river problem. As more of it is done, the cost could be expected to come down; and as we became more desperate for water, we would be more willing to pay the cost even if it didn’t come down. (6) This is an arrangement whereby large landowners would sell the groundwater under their land, for whatever the market would bear, to cities that might be hundreds of miles distant. This would involve the considerable cost of pipeline construction and would mean faster depletion of groundwater reserves. (7)
It’s a good bet that during the 21st century some new arrangements are going to have to be made about the nation’s — and the world’s — water supplies. These are likely to be neither cheap nor easy. They are more likely to be cheaper and easier if we have thought about them in advance. (8) We have been sued to choices of guns or butter. This one might be water or meat.
  • A. A century ago, a drought affected only farmers and perhaps inland navigation; now it affects everybody.
  • B. The Northwest is showing signs of getting tired of this drain.
  • C. It is not too soon to begin.
  • D. We cannot live without oil in the style to which we have become accustomed, but we cannot live at all without water.
  • E. Rivers are running dry, especially in the West.
  • F. It would also mean less food production.
  • G. A solution currently being advanced in west Texas is a concept called "Water Ranching".
  • H. The latter is expensive: desalinization of seawater.

题型:解答题

脑囊虫病发病机制是()

A.囊尾蚴对周围脑组织的压迫和破坏

B.作为异种蛋白引起的脑组织变态反应与炎症

C.囊尾蚴堵塞脑脊液循环通路引起颅内压增高

D.囊尾蚴移行过程中机械损伤

E.囊尾蚴进入神经元造成损伤

题型:解答题

人造板材的种类很多,主要有胶合板、纤维板、刨花板等。除胶合板外,所使用的原料均系木材采伐过程上的剩余物,如木屑。

题型:解答题

可以向城镇职工出售的公有住房是()

A.办公、经营和住房混合在一起的住房

B.两户或者两户以上共用厨房、厕所的单元房

C.国有企业、事业单位的套间住房

D.已列入城市规划有待改造拆迁的住房

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