临床试验中研究对象的随机分组是为了()。 A.使试验组和对照组人数相同 B.试验

题型:单项选择题

问题:

临床试验中研究对象的随机分组是为了()。

A.使试验组和对照组人数相同

B.试验组和对照组都受益

C.增加研究对象的依从性

D.避免研究者偏倚

E.平衡试验组和对照组已知和未知的混杂因素

考点:健康教育与健康促进(医学高级)流行病学流行病学题库
题型:单项选择题

-Would you like _______rice ?  -NO, thanks .

A. much                   B. some              C. any

题型:单项选择题

阅读理解。

     Excused from recycling (回收利用) because you live in a high rise with a rubbish chute (垃圾道)?

You won't be for long. Miami's Mark Shantzis has made it simple for those living in tall buildings to use

the chute and recycle too.

     In Shantzis' Hi-Rise Recycling System, a chute leads to a pie-shaped container with six boxes that

can turn around when operated. The system, which fits in the same space as the chute and container now

in use, enables glass, plastic, paper, metal, and other rubbish to go into separate boxes.

     The system is controlled from a board next to the chute door. The board has a button for each class

of recycling materials (as well as for unrecyclables).At the press of a button, a microcomputer locks all

other floors' chute door and sets the recycling container turning until the right box comes under the chute.

The computer also counts the loads and gives a signal by phone when the box is full. And a particular

piece of equipment breaks up the nonrecyclables.

     Sorting (分类) recyclables before they are collected saves the use of expensive materials recovery

equipment which otherwise has to do the sorting. Such equipment often makes recycled materials very

expensive, so expensive that tons of recyclables remain wasted. Shantzis believes his system could help

recycled materials become more cost-effective.

1.The purpose in writing this text is _________.

A. to encourage people to recycle their rubbish

B. to explain the need for rubbish collection in high rises

C. to describe the use of computer technology in recycling

D. to introduce a recycling system for high rises    

2. When he says "You won't be for long", the writer means that ________.

A. you'll soon be living in a cleaner building

B. rubbish chutes will become out of date before long

C. it won't be long before you'll have to recycle your rubbish

D. you won't wait long for your turn to recycle rubbish

3. Before dropping rubbish into the chute you have to _________.

A. press the correct button

B. check if the container is full

C. lock the other floors' chute doors      

D. break up the rubbish

4. The biggest advantage of this new system is that __________.

A. it makes better use of the existing recovery equipment

B. it saves time and space

C. it saves money for people living in high rises          

D. it reduces the cost of recycling     

题型:单项选择题

已知t℃时,纯水中[H+]=2×10-7 mol·L-1,在该温度下Mg(OH)2的溶度积Ksp[Mg(OH)2]=3.2×10-11mol3·L-3,求该温度下饱和的Mg(OH)2溶液的pH为多少?

题型:单项选择题

文字作为文化的载体有什么重要作用?

题型:单项选择题

希腊的政治制度是()

A、民主制

B、奴隶制

C、奴隶制民主政治

D、君主制

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