突触前抑制的发生是由于A．突触前膜兴奋性递质释放减少 B．突触后膜超极化 C．突触前

晕厥的原因考虑为

A．癫痫发作

B．缺氧发作

C．脑栓塞

D．脑脓肿

E．化脓性脑膜炎

在“测定直流电动机的效率”实验中，用如图（a）所示的电路测定一个额定电压为6V、额定功率为3W的直流电动机的机械效率。

（1）请根据图（a）完成图（b）中的实物图；

（2）实验中保持电动机两端电压U恒为6V，重物每次匀速上升的高度h均为1.5m，所测物理量及测量结果如下表所示：

计算电动机效率η的的表达式为______________（用题目中的符号表示），前4次实验中电动机工作效率的平均值为_______________。

（3）在第5 次实验中，电动机的输出功率是___________；可估算出电动机线圈的电阻为_______________Ω。

骨肉瘤的基本X线表现?

　　亲爱的同学们，在《怎样搜集资料》这次综合性学习中，你们一定熟练掌握了搜集资料这项基本技能，你们一定在知识的海洋中自由地邀游，不妨把你的学习所得向大家展示一下。

（1）中秋节是我国的传统节日，自古以来，许多诗文作品中都写到了中秋节，你一定搜集了不少，不妨写出一两句来。

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（2）端午节也是我国的传统节日，请将你搜集到的有关端午节的历史故事写出来与大家共享。

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（3）长江三峡工程是一项举世瞩目的伟大工程，你知道它坝址选在何处吗？你能向大家简单介绍一下它的工程方案吗？

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My Space and other Web sites have unleashed a potent new phenomenon of social networking in cyberspace, (1) at the same time, a growing body of evidence is suggesting that traditional social (2) play a surprisingly powerful and under-recognized role in influencing how people behave.

The latest research comes from Dr. Nicholas A. Christakis, at the Harvard Medical School, and Dr. James H. Fowler, at the University of California at San Diego. The (3) reported last summer that obesity appeared to (4) from one person to another (5) social networks, almost like a virus or a fad. In a follow-up to that provocative research, the team has produced (6) findings about another major health (7) : smoking. In a study published last week in the New England Journal of Medicine, the team found that a person’s decision to (8) the habit is ply affected by (9) other people in their social network quit—even people they do not know. And, surprisingly, entire networks of smokers appear to quit virtually (10)

For (11) of their studies, they (12) of detailed records kept between 1971 and 2003 about 5,124 people who participated in the landmark Framingham Heart Study. Because many of the subjects had ties to the Boston suburb of Framingham, Mass. , many of the participants were (13) somehow—through spouses, neighbors, friends, co-workers—enabling the researchers to study a network that (14) 12,067 people.

Taken together, these studies are (15) a growing recognition that many behaviors are (16) by social networks in (17) that have not been fully understood. And (18) may be possible, the researchers say, to harness the power of these networks for many (19) , such as encouraging safe sex, getting more people to exercise or even (20) crime.

3（）

A.pair

B.sociologists

C.spouse

D.universities