如图所示,相距L和平行界面将空间分为Ⅰ、Ⅱ、Ⅲ三个区域,区域Ⅰ和Ⅱ内是垂直纸面、

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问题:

如图所示,相距L和平行界面将空间分为Ⅰ、Ⅱ、Ⅲ三个区域,区域Ⅰ和Ⅱ内是垂直纸面、指向读者的匀强磁场,磁感强度分别为,区域Ⅲ内是匀强电场,电场强度为E,方向从垂直指向.现使质量为m、电量为q的带正电粒子以垂直界面的速度自O点向射出(O点与相距),若粒子所受的重力可以略而不计.为了使正电粒子能按图示的实线轨道运动 (轨道的两段圆弧半径相等)求:

(1)磁感强度之比应是多少?

(2)电场强度E的值应小于多少?

考点:带电粒子在复合场中的运动
题型:问答题

进口在港澳地区生产的麻醉药品()

A.应取得《进口药品注册证》

B.应取得《医药产品注册证》

C.应取得《进口准许证》

D.应取得《进口药品准许证》和《医药产品注册证》

E.应取得《进口药品准许证》和《进口药品注册证》

题型:问答题

甲数是52,乙、丙两数的平均数是61,甲、乙、丙三个数的平均数是______.

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My husband and I were once in Nepal(尼泊尔)to see sunrise over the Himalayas.

One morning we awoke to total darkness at 5 o’clock.As we rushed through a town with cameras in hand,I noticed the calm,gentle way the Nepalese people greeted the morning.One man boiled a huge pot of milk tea,and other villagers gathered around his fire,cupping their hands around small glasses of the steaming sweet mixture.It was fascinating,but not to be left behind,we joined the stream of tourists moving quickly up to the lookout point.

The top was crowded when we arrived,but after 10 minutes of cold waiting,the assembled group gave up.“The cloud cover is too heavy,”one said.Then one by one they rushed down the hill to the next item on their sightseeing list.I was disappointed as well,but suddenly I noticed a small Nepalese boy absently playing with a stick and shooting quick glances at the clouds.He must know something we don’t,I thought.I decided to wait with him.

The boy and I didn’t have to wait long.Moments later,a tiny stream of golden light burned through one thick cloud,then another.Rose-colored fog warmed the backs of the clouds,and suddenly the morning sun stole a glance around the side of the mountain,mile above where I’d expected it to be.

Nothing I’d seen before prepared me for the moment the clouds withdrew with bowed heads,and the magnificent Himalayas were revealed before,around,and above me.I sat in astonishment,not breathing,not daring to look away,certain that God had placed me here at the backdoor of Earth to show me what Heaven really looks like.I certainly got the message.Never again will I rush a sunrise.I now know Nature will supply her fruits to me only when I am truly ready to receive them.

小题1:What does “It” in Paragraph 2 most probably imply?

A.The darkness of the town in the morning.

B.The huge pot of milk tea boiling on the fire.

C.The way the local people welcomed the day.

D.The stream of tourists rushing to the lookout point.小题2:The author decided to wait with the Nepalese boy because _____.

A.she felt kind of having faith in him

B.the restless tourists disappointed her

C.that boy was praying to the sun with a magic stick

D.she had nothing more to see on her sightseeing list小题3:What can be concluded from the passage?

A.Do in Rome as the Romans do.

B.God helps those who help themselves.

C.Time and tide wait for no man.

D.Fortune rewards those having patience.

题型:问答题

电流通过人体时间越长,电击伤害程度越重

题型:问答题

软件的可维护性包括( )。

A.正确性、灵活性、可移植性

B.可测试性、可理解性、可修改性

C.可靠性、可复用性、可用性

D.灵活性、可靠性、高效性

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