如图所示,处在磁感应强度为B的匀强磁场中的单匝矩线圈abcd,以恒定的角速度ω绕

题型:选择题

问题:

如图所示,处在磁感应强度为B的匀强磁场中的单匝矩线圈abcd,以恒定的角速度ω绕ab边转动,磁场方向垂直于纸面向里,线圈所围面积为S,线圈导线的总电阻为R.t=0时刻线圈平面与纸面重合,且cd边正在离开纸面向外运动.则正确的是(  )

A.时刻t线圈中电流的瞬时值icosωt

B.线圈中电流的有效值I

C.线圈中电流的有效值I=

D.线圈消耗的电功率P

考点:正弦式交变电流交变电流的周期和频率
题型:选择题

下列抽样中,最适宜用系统抽样法的是[ ]

A.某市的4个区共有2000名学生,且4个区的学生人数之比为3∶8∶8∶2,从中抽取200名学生做样本

B.从某厂生产的2000个电子元件中随机抽取5个做样本

C.从某厂生产的2000个电子元件中随机抽取200个做样本

D.从某厂生产的20个电子元件中随机抽取5个做样本

题型:选择题

蛛网膜下腔出血后出现脑血管痉挛多发生在出血后()。

A.立即

B.3~14天

C.1天

D.14天以后

E.1个月以后

题型:选择题

男性,41岁,农民。发热3d于某年12月住院,同村已有多名发热病人住院,确诊为流行性出血热,该病人此时抗病毒的治疗是。()

A.头孢拉定

B.病毒唑

C.氟喹酮类

D.两性霉素B

E.氨苄青霉素

题型:选择题

秦艽碱甲升高血糖的作用机制是

A.促进糖原异生
B.抑制组织对糖的利用
C.促进消化道对糖的吸收
D.促进肾上腺素的释放
E.抑制胰岛素的释放

题型:选择题

To produce the upheaval (激变) in the United States that changed and modernized the domain of higher education from the mid-1860s to the mid-1880s, three primary causes interacted. The (1) of a half-dozen leaders in education provided the personal force that was needed. (2) , an outcry (呐喊) for a fresher, more practical, and more advanced kind of instruction (3) among the alumni (校友) and friends of nearly all of the old colleges and grew into a movement that overrode (压倒) all (4) opposition. The aggressive "Young Yale" movement appeared, demanding partial alumni control, a more (5) spirit, and a broader course of study. The graduates of Harvard College simultaneously (6) to relieve the college’s poverty and demand new (7) . Education was pushing toward higher standards in the East by (8) off church leadership everywhere, and in the West by finding a wider range of studies and a new (9) of public duty.

The old-style classical education received its most crushing (10) in the citadel (城堡) of Harvard College, (11) Dr. Charles Eliot, a young captain of thirty-five, son of a former treasurer of Harvard, led the (12) forces. Five revolutionary advances were made during the first years of Dr. Eliot’s (13) They were the elevation and amplification of entrance requirements, the enlargement of the (14) and the development of the (15) system, the recognition of graduate study in the liberal arts, the raising of professional training in law, medicine, and engineering to a postgraduate level, and the fostering (培养) of greater (16) in student life. Standard of admission were sharply advanced in 1872—1877. (17) the appointment of a clean (院长) to take charge of student affairs, and a wise handling of (18) , the undergraduates were led to regard themselves more as young gentlemen and (19) as young animals. One new course of study after another was (20) —science, music, the history of the fine arts, advanced Spanish, political economy, physics and international law.

17()

A.By

B.With

C.Upon

D.At

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