芳香烃是指 [ ] A.分子组成符合CnH2n-6 (n≥6)的化合物 B.分子

题型:选择题

问题:

芳香烃是指 [ ]

A.分子组成符合CnH2n-6 (n≥6)的化合物

B.分子中含有苯环的化合物

C.有芳香气味的烃

D.分子中含有一个或多个苯环的碳氢化合物

考点:芳香烃的通式苯的同系物
题型:选择题

一根张紧的水平弹性绳上有a,b两点,相距s=14m,.b点在a点的右方,当一列简谐横波沿此长绳向右传播时,a点达到正向最大位移时,b点的位移恰好为零,而且向上运动.经过t=1s后,a点的位移为零,且向上运动,而b的位移恰好到达负向最大位移处,求:

(1)这列简谐横波的波速.

(2)当2λ<s<3λ,3T<t<4T时,这列波的波速是多少?

(3)画出2λ<s<3λ,3T<t<4T时,1s末的波形图.

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Maybe you’ve just invented something better than the iPhone or a solar-powered car. You don’t want anyone to steal your design. What should you do? Patent (申请专利) it! Patents are the best way to get credit for your work and help others continue advancing in that field. Here’s what you need to know.

A patent gives you the right to an invention. The patent protects its owner, which means the invention can’t be copied or sold without their agreement. In exchange, the owner must reveal information about the invention. This contributes knowledge that helps other inventors improve on their own research. A patent usually lasts about 20 years.

The first step to getting a patent is the application. The person applying must name the invention, explain its use and describe it clearly. The invention must be practical and contain some new characteristic — something that hasn’t been seen or used before. But not everything “new” can be patented. Many countries don’t allow patents on things like new concepts, scientific theories, medical procedures or substances already found in nature.

You may not be able to see patents, but they’re connected to nearly everything. There are patents on things you use every day, like plastic, medicine and your computer. There are patents on things that are unavailable on the market, too. Apple is well-known for its patents on potential products, such as the “iBike” or the “iKey”.

Of course there are also patents on inventions like this. Take the anti-eating face mask for example. This device locks around your head with a metal cage covering your mouth. You can breathe and speak, but you can’t eat!

Although many patented inventions can be failures, there’s plenty of room for success. So if you have a cool invention, try to patent it.

小题1:Which of the following is NOT true according to the text?

A.A patent can last for around 20 years.

B.Everything new can be patented.

C.Your invention is protected after you have applied for a patent.

D.Some patents are on the things that we use every day.小题2:We can infer that Apple’s iBike is _____.

A.a popular product

B.a mere new concept

C.a famous brand in the world

D.a practical bike on the market小题3:The underlined word “device” in Paragraph 5 can best be replaced by “_____”.

A.weapon

B.medicine

C.equipment

D.strength小题4:The purpose of writing this passage is to _____.

A.advertise

B.persuade

C.warn

D.inform

题型:选择题

泵的效率等于()的乘积。

A.机械效率容积效率

B.机械效率容积效率流动效率

C.容积效率流动效率

D.机械效率流动效率

题型:选择题

主动进化学派认为,人类的进化是()

A、渐变的

B、突变的

C、渐变和突变相结合

D、毫无规律

题型:选择题

自溜运输的必要条件是线路应具有足够的()。

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