激光器一般由三个主要部分构成:工作物质、激发装置和光学谐振腔。下列叙述错误的是 A.

题型:单项选择题

问题:

激光器一般由三个主要部分构成:工作物质、激发装置和光学谐振腔。

下列叙述错误的是

A.激发装置的作用是把处于低能级上的原子激发到高能级
B.激发装置实现粒子数翻转
C.原子不可以长时间停留在亚稳态
D.激光器的工作物质,必须具有合适的亚稳态能级
E.只有人为地创造条件,才能得到激光

考点:放射医学技师放射技师基础知识初级放射医学技师基础知识
题型:单项选择题

在计算机网络中,用户访问网络的界面是______。

A.主机

B.终端

C.通信控制处理机

D.网卡

题型:单项选择题

I was just a boy when my father brought me to Harlem for the first time, almost 50 years ago. We stayed at the Hotel Theresa, a grand brick structure at 125th Street and Seventh Avenue. Once, in the hotel restaurant, my father pointed out Joe Louis. He even got Mr Brown, the hotel manager, to introduce me to him, a bit paunchy but still the champ as far as I was concerned.
Much has changed since then. Business and real estate are booming. Some say a new renaissance is under way. Others decry what they see as outside forces running roughshod over the old Harlem.
New York meant Harlem to me, and as a young man I visited it whenever I could. But many of my old haunts are gone. The Theresa shut down in 1966. National chains that once ignored Harlem now anticipate yuppie money and want pieces of this prime Manhattan real estate. So here I am on a hot August afternoon, sitting in a Starbucks that two years ago opened a block away from the Theresa, snatching at memories between sips of high-priced coffee. I am about to open up a piece of the old Harlem the New York Amsterdam News when a tourist asking directions to Sylvia’s, a prominent Harlem restaurant, penetrates my daydreaming. He’s carrying a book: Touring Historic Harlem.
History. I miss Mr Michaux’s bookstore, his House of Common Sense, which was across from the Theresa. He had a big billboard out front with brown and black faces painted on it that said in large letters: "World History Book Outlet on 2,000,000,000 Africans and Nonwhite Peoples." An ugly state office building has swallowed that space.
I miss speaker like Carlos Cooks, who was always on the southwest corner of 125th and Seventh, urging listeners to support Africa. Harlem’s powerful political electricity seems unplugged -- although the streets are still energized, especially by West African immigrants.
Hard-working southern newcomers formed the bulk of the community back in the 1920s and ’30s, when Harlem renaissance artists, writers, and intellectuals gave it a glitter and renown that made it the capital of black America. From Harlem, W.E.B. DuBois, Langston Hughes, Paul Robeson, Zora Neal Hurston, and others helped power America’s cultural influence around the world.
By the 1970s and ’80s drugs and crime had ravaged parts of the community. And the life expectancy for men in Harlem was less than that of men in Bangladesh. Harlem had become a symbol of the dangers of inner-city life.
Now, you want to shout "Lookin’ good!" at this place that has been neglected for so long. Crowds push into Harlem USA, a new shopping centre on 125th, where a Disney store shares space with HMV Records, the New York Sports Club, and a nine-screen Magic Johnson theatre complex. Nearby, a Rite Aid drugstore also opened. Maybe part of the reason Harlem seems to be undergoing a rebirth is that it is finally getting what most people take for granted.
Harlem is also part of an "empowerment zone"--a federal designation aimed at fostering economic growth that will bring over half a billion in federal, state, and local dollars. Just the shells of once elegant old brownstones now can cost several hundred thousand dollars. Rents are skyrocketing. An improved economy, tougher law enforcement, and community efforts against drugs have contributed to a 60 percent drop in crime since 1993.

Which of the following is NOT an appropriate depiction of the present-day Harlem

A. Harlem is now seen as a tourist attraction.
B. Harlem is becoming an expensive place to live in.
C. Harlem has transformed into a place of entertainment.
D. Harlem’s crime rate remains the same as ever.

题型:单项选择题

依照施工合同示范文本通用条款规定,施工合同履行中,发包人收到竣工结算报告及结算资料后56天内仍不支付,承包人有权( )。

A.留置该工程

B.与发包人协议将该工程折价

C.直接委托拍卖公司拍卖该工程

D.申请人民法院将该工程依法拍卖

E.就该工程折价或拍卖的价款优先受偿

题型:单项选择题

"《水利水电工程等级划分及洪水标准》(SL252—2000)规定(以下简称标准),水利水电工程根据其工程规模、效益以及在国民经济中的重要性,划分为()。"

A.三等

B.四等

C.五等

D.六等

题型:单项选择题

关于脱水,下列哪项不正确()

A.重度脱水的失水量为体重的10%以上

B.轻度脱水的失水量为体重的5%以下

C.高渗性脱水系电解质丢失比例大于水分丢失

D.低渗性脱水者易发生休克

E.低渗性脱水者易发生脑血管意外

更多题库