以下哪种操作产生中度气溶胶()。A.玻片凝集试验 B.毒液滴在不同表面上 C.接种鸡

题型:单项选择题

问题:

以下哪种操作产生中度气溶胶()。

A.玻片凝集试验

B.毒液滴在不同表面上

C.接种鸡胚

D.倾倒毒液

考点:生物学生物安全生物安全题库
题型:单项选择题

击剑有主被动之分(重剑除外)获得“优先裁判权”的一方(重剑除外)击中对方,使裁判器亮红灯或绿灯才能得分。

题型:单项选择题

分布于上肢内侧后缘的经脉是

A.手太阴肺经

B.手阳明大肠经

C.手厥阴心包经

D.手少阴心经

E.手太阳小肠经

题型:单项选择题

George Gershwin, born in 1998, was one of America’s greatest composers. He published his first song when he was eighteen years old. During the next twenty years he wrote more than five hundred songs.

Many of Gershwin’s songs were first written for musical plays performed in theatres in New York City. These plays were a popular form of entertainment in the 1920s and 1930s. Many of his songs have remained popular as ever. Over the years they have been sung and played in every possible way — from jazz to country.

In the 1920s there was a debate in the United States about jazz music. Could jazz, some people asked, be considered serious music? In 1924 jazz musician and orchestra leader Paul Whiteman decided to organize a special concert to show that jazz was serious music. Gershwin agreed to compose something for the concert before he realized he had just a few weeks to do it. And in that short time, he composed a piece for piano and orchestra which he called Rhapsody in Blue. Gershwin himself played the piano at the concert. The audience were thrilled when they heard his music. It made him world-famous and showed that jazz music could be both serious and popular.

In 1928, Gershwin went to Paris. He applied to study composition (作曲)with the well-known musician Nadia Boulanger, but she rejected him. She was afraid that classical study would ruin his jazz-influenced style. While there, Gershwin wrote An American in Paris. When it was first performed, critics (评论家)were divided over the music. Some called it happy and full of life, to others it was silly and boring. But it quickly became popular in Europe and the United States. It still remains one of his most famous works.

George Gershwin died in 1937, just days after doctors learned he had brain cancer. He was only thirty-nine years old. Newspapers all over the world reported his death on their front pages. People mourned the loss of the man and all the music he might have still written.

小题1:Many of Gershwin’s musical works were ________ .

A.written about New Yorkers

B.Composed for Paul Whiteman

C.played mainly in the countryside

D.performed in various ways小题2:What do we know about the concert organized by Whiteman?

A.It attracted more people to theatres

B.It proved jazz could be serious music

C.It made Gershwin leader of the orchestra

D.It caused a debate among jazz musicians小题3:What did Gershwin do during his stay in Paris?

A.He created one of his best works

B.He studied with Nadia Boulanger

C.He argued with French critics

D.He changed his music style小题4:What do we learn from the last paragraph?

A.Many of Gershwin’s works were lost

B.The death of Gershwin was widely reported

C.A concert was held in memory of Gershwin

D.Brain cancer research started after Gershwin’s death.小题5:Which of the following best describes Gershwin?

A.Talented and productive

B.Serious and boring

C.popular and unhappy

D.Friendly and honest

题型:单项选择题

如图所示,质量均匀分布的甲、乙两球的重力相等,均为150N,球半径和BD、BC的轻绳长均为R,今由轻绳AB连接悬挂在处于水平位置的杠杆OE上,悬挂点距支点O的距离为0.2m,杠杆为质量均匀分布的直棒,每米的重力为30N,则当所有物体处于静止时,绳AB的拉力为______N,杠杆的长度为______m时,在E端所用力F为最小.

题型:单项选择题

膨胀机后压力越高,膨胀机内的压降(),单位制冷量()。

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