This large city does almost no manufacturing and very little wholesale trade. Yet without the important service (1) provides, business everywhere would quickly grind to a (2) . Chaos would reign in all other leading cities. As you have guessed, the "product" we are talking about is government, and the city is the (3) of the United States, Washington, D. C. One out of every two persons (4) in the city works for the federal government.
Washington has many (5) . It leads the nation in level of education achieved by its residents. More than fifteen percent of its adults have had four years or more of college. (6) scientists can be found here than in any other city. Since larger incomes are earned by (7) people, Washington has the highest median income of any city.
Information is the vital force of the city. The Library of Congress (8) the largest and most comprehensive warehouse of informa
A. before
B. after
C. if
D. when
Wal-Mart announced Thursday afternoon that it would introduce a program nationwide called (61) "Pick Up Today" that allows customers to submit orders online and pick up their items few hours later in their local store. (62) The move is not revolutionary— Sears and Nordstrom, as instance, already have similar programs.
(63) Retailers say that tying online and in-store inventory together lets them to sell more products. (64) Nordstrom recently combined its inventory so that if the online stockroom is out of a jacket, a store that has it can ship to the Web customer. (65) Encourage customers to retrieve items they have ordered online in a store increases visits to the stores, which usually increases sales. (66) Best Buy offers both store pickup and "ship to store," where items are shipped free from a local store. Ace Hardware, J.C. Penney and Wal-Mart itself are am
由高能加速器或对撞机产生的新粒子用大型粒子探测器来观测。将探测器安装在对撞机的粒子对撞区，尽可能把对撞点包围起来，以得到最大的接收立体角。
所有大型粒子探测器都是多种探测器的组合体，原理相似，结构各异，规模不等。各种探测器的基本原理是使带电粒子在穿过物质时，由于电离效应、辐射效应等留下径迹，用电子学方法和计算机手段捕捉这些信息，再加以放大、分析处理，以得到粒子的能量、速度、动量等。
探测器的一个重要指标是粒子的分辨率，通常是由测得的粒子能量、速度、动量等得到粒子的质量，或根据不同粒子与物质相互作用的特性来确定粒子的类别。当今的探测器都充分利用大型计算机来进行数据的获取和分析。
随着能量的增加，探测器更加庞大和复杂。对撞后产生的粒子数增多，对触发速率、数据获取率、电子学和探测器计数率、探测器的抗辐照能力、计算机数据处理和分析能力都提出了更高要求。在电子对撞机上的探测器大多是对称的，而在德国的HERA上工作的探测器则前后不对称，以适应电子、质子能量不同的要求。
工作在北京正负电子对撞机上的北京谱仪(BES)是我国自行设计、制造的粒子探测器，是国际上在该能区工作的最先进的探测器之一，运行3年来获得的物理结果受到了国际上的关注。1992年，完成T轻子质量的精确测量，将过去的结果修正为7.2兆电子伏，将精度提高了10倍，为解决τ寿命、分析比与标准模型框架之一的轻子普适性理论的矛盾问题起了关键作用。该结果在国际高能物理大会上宣布后引起普遍的重视，专家们认为这是近几年高能物理最重要的实验之一。此外，它还在J/4、粲物理研究方面取得了令人瞩目的结果。这一系列的成果已得到国际高能物理同行的承认，说明我国在τ轻子和粲夸克领域的研究方面已在国际高能物理界占有一席之地。
For about three centuries we have been doing science, trying science out, using science for the construction of what we call modern civilization. Every dispensable item of contemporary technology, from canal locks to dial telephones to penicillin, was pieced together from the analysis of data provided by one or another series of scientific experiments. Three hundred years seems a long time for testing a new approach to human inter-living, long enough to settle back for critical appraisal of the scientific method, maybe even long enough to vote on whether to go on with it or not. There is an argument.
Voices have been raised in protest since the beginning, rising in pitch and violence in the nineteenth century during the early stages of the industrial revolution, summoning urgent crowds into the streets any day these days on the issue of nuclear energy. "Give it back," say some of the voices, "It doesn’t really work, we’ve tried it and it doesn&r
A. For three hundred years there have been people holding a hostile attitude toward science.
B. Scientific experiments in the past three hundred years have produced many valuable items.
C. Some people think three hundred years is not long enough to set back for critical appraisal of scientific method.
D. Modern civilization depends on science so man supports scientific progress unanimously.
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