二次污染物

题型:名词解释

问题:

二次污染物

考点:大气污染控制工程大气污染控制工程题库
题型:名词解释

通电螺线管两端的磁极性质跟电流方向的关系可以用 _________ 来判断。

题型:名词解释

See a cell phone cover that you like on Taobao? Forget about placing an order, paying the bill online and waiting for days for it to be delivered to you. In the near future, you'll be able to get it in minutes just by hitting "print" on your computer.

You might find it hard to believe that you could actually "print" an object like you would a picture. But it is not that hard to understand how it would work. Just as a traditional printer sprays (喷) ink onto paper line by line, modern 3-D printers spread material onto a surface layer by layer, from the bottom to the top, gradually building up a shape.

Instead of ink, the materials the 3-D printer uses are mainly plastic, resin (树脂)and certain metals. The thinner each layer is --- from a millimeter to less than the width of a hair ---  the smoother and finer the object will be.

This may sound like a completely new technology, but the truth is that 3-D printing has been around since the late 1980s. Back then, it was hardly affordable for most people, so few knew about it.

Last year, though, saw a big change in the 3-D printing industry--- printers became much cheaper. For example, 10 years ago a desktop 3-D printer might have cost £20,000 (200,000 yuan), while now they cost only about £ 1,000, according to the BBC.

Taken out of the factory and introduced to more diverse and common uses, 3-D printing can create just about anything you can think of ---flutes (笛子), bikinis, jewelry, aircraft parts and even human organs. In fact, scientists from Cornell University in New York have just made an artificial ear using a 3-D printer, according to Science Daily. The fake ear looks and acts exactly like a natural one.

However, as 3-D printing becomes more common, it may bring about certain problems --- such as piracy(盗版). "Once you can download a coffee maker, or print out a new set of kitchen utensils (餐具) on your personal 3-D printer, who will visit a retail (零售的) store again?" an expert in 3-D printing told Forbes News. Even more frightening, what if anyone in the world could use a 3-D printer to print out a fully functioning gun?

小题1:According to the article, in the future, the 3-D printing technology will ___.

A.enable people to make better purchases online

B.be applied as widely in our daily lives as computers

C.change the way we make many products

D.shorten the time it takes for people to get what they buy online小题2:What was the big event happening in the 3-D printing industry last year?

A.The 3-D printing technology was taken out ofthe factory.

B.The 3-D printer became more affordable forconsumers.

C.The 3-D printer was used for medical treatmentfor the first time.

D.3-D printing technology began to be used invarious fields.小题3:How is the last paragraph developed?

A.By analyzing a cause and an effect.

B.By making comparisons.

C.By giving examples.

D.By presenting research findings.小题4:What is the best title of the passage?

A.Printing out everything

B.Technology in the future

C.Online shopping disappearing

D.Great demand for 3-D printers

题型:名词解释

数据库管理系统是

A.操作系统的一部分

B.在操作系统支持下的系统软件

C.一种编译系统

D.一种操作系统

题型:名词解释

导游讲解的因人而异、因地制宜、因时而变原则体现了导游活动的______,也反映了——和______的规律。

题型:名词解释

网络真是个神奇的东西,它让地球真的成了一个村庄,人们只要点点鼠标就可以了解他想要了解的未知世界,但是网络上的陷阱也是防不胜防。
网络:

A.是个村庄
B.对生活有好处
C.完全是个陷阱
D.没有好处

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