下述关于桥式整流电容滤波电路的描述不正确的是()。 A.滤波电路利用了电容的储能作用

题型:单项选择题

问题:

下述关于桥式整流电容滤波电路的描述不正确的是()。

A.滤波电路利用了电容的储能作用

B.电容滤波电路适用于小电流负载的场合

C.每只二极管导通角小于π

D.滤波电容容量一定时,若负载电阻减小,则输出电压脉动变小

考点:细胞生物学细胞基本知识细胞基本知识题库
题型:单项选择题
一根电线用去
3
4
,还剩下
1
4
米.______.
题型:单项选择题

当出现()情况时,应采取分类法进行职位评价。

A.职位类别较复杂的企业

B.小型企业

C.评价人员对企业各项职位的情况非常了解

D.较大规模企业中的管理类职位

E.处在劳动力市场相对稳定环境下的规模较大的企业

题型:单项选择题

Food prices have risen sharply over the past few years. The good news is that the rate of increase has slowed. The bad news is that prices will not go down anytime soon.

Also,the rate of global agricultural production is slowing. Yet it needs to increase 60% over the next 40 years to feed a growing world population.

These are among the findings from the OECDFAO(the Organization for Economic Cooperation and Development & the Food and Agriculture Organization)Agricultural Outlook(展望)2012-2021.

FAO Director­General Jose Graziano da Silva spoke at a news conference in Rome when the report was released. Mr.Da Silva said that,not surprisingly,the world's poorest people will feel the greatest effects of higher prices.

“For the millions and millions of extremely poor people, the effects of high food prices are clear—they might have to change their diets,usually to ones with poorer nutrition quality, ”he said.

In middle­income countries, people are gaining weight as they eat fewer fruits and vegetables and more of the cheaper but less nutritious foods.

The report also shows that farmers in poorer countries will be leading efforts to feed an expected 9,000,000,000 people by 2050.The outlook predicts that farmers in Latin America,the Caribbean and sub­Saharan Africa will drive agricultural production in the future.

Angel Gurria,Secretary­General of the OECD,said:“We can feed 9,000,000,000 people by 2050 on this planet. But we have to organize ourselves better.” But there are plenty of challenges.One­fourth of all agricultural land is damaged. Many countries face water shortages(短缺).And experts believe climate change is driving increasingly unusual weather patterns.

The report says farmers need to use more growing methods that can't cause damage to the environment.At the same time,it says governments should end economically harmful supports and spend more money to increase agricultural production.Mr.Gurria says rich and poor nations need to treat agriculture more like a business.

“In many cases,agriculture is related in people's minds to the poorest. It's related to aid. It's related to very poor living conditions,etc. We have got to shake that image away,”he said.

小题1:Why are people gaining weight in countries with average incomes?

A.They eat more food.

B.They eat less nutritious foods.

C.They eat cheaper fruits.

D.They eat cheaper vegetables.小题2:It can be inferred from the text that poorer countries ______.

A.are damaging a great part of their agricultural land

B.will play a great role in feeding the growing world population

C.are spending lots of money increasing agricultural production

D.will not be so seriously affected by food prices as rich nations小题3:What can be done to deal with the slow agricultural production?

A.Improving the growing methods.

B.Finding more agricultural land.

C.Preventing governments' involvement.

D.Improving farmers' living conditions.小题4:Which of the following might Angel Gurria agree with?

A.Agriculture means difficulty and sadness.

B.Food prices will go down in the near future.

C.It's almost impossible to feed 9,000,000,000 people by 2050.

D.Both rich and poor countries should take agriculture seriously.

题型:单项选择题

引起口腔"鹅口疮"的真菌是()

A.隐球菌

B.曲菌

C.毛霉菌

D.念珠菌

E.放线菌

题型:单项选择题

()对境内单位或者个人从事境外商品期货交易的品种进行核准。

A.国务院期货监督管理机构

B.国务院银行业监督管理机构

C.国务院商务主管部门

D.国务院证券监督管理机构

更多题库