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题型:名词解释

不完全抗原的特点是()

A.仅具有免疫原性

B.仅具有抗原性

C.具有免疫原性及抗原性

D.与抗体不产生沉淀反应

E.病原微生物

题型:名词解释

By 2010 the European Commission predicts transcontinental freight traffic will have risen 50 percent as a result of European expansion, and much of that will have to cross the enormous obstacle of the Alps. Right now the only practical way for most heavy traffic to get through is by truck and tunnel. And while that could change if safer and cleaner rail lines were opened, the chances are that won’t happen anytime soon.

Several private trucking companies have adapted quickly and creatively to the demands of European unification. Some of the bigger truckers trace cargoes with the Global Positioning System and sophisticated computers. And if trucks also bring more road hazards and pollution, at present there is no alternative. Right now only 8 percent of European merchandise moves by rail, compared with more than 40 percent in the United States. Delays are so common that the average speed for freight is about 18km an hour.

The railways have had trouble outgrowing a heritage of national rivalries and open warfare between Europe’s countries. The result is what another European Commission report calls "a mosaic of badly interconnected national systems. " Language barriers remain a problem, requiring crew changes at some borders. Switching systems and signals differ.

And efficiency is more of a dream than a goal. Europe’s railroads still have to deal with "phantom trains" that run so late that they combine with others and disappear from the railroad’s records. In an era when many companies depend on a "just-in-time" inventories to make a profit, railroads are rarely on time at all.

Yet there is little official enthusiasm for changing the system. The reality is that governments have helped create the imbalance between road and rail in Europe—and government action will likely be needed to fix it. The French emphasis on using rail to move people instead of goods, for instance, has helped cripple freight service. "All the investments went to passenger traffic," says Denis Douté, director of freight services for the French rail company SNCF. Freight trains have had to find "windows" to run in between passenger trains, unlike those in the United States, which often travel on separate tracks. The further development of the freight network requires massive investments to modernize existing infrastructure and open new ones. However, the political will to fund that kind of investment is lacking, which means the citizens will have to hold their noses for a while longer.

According to the author, the badly interconnected national system results from ().

A. serious conflicts between countries

B. different language systems

C. the bad manners of crew at borders

D. the lack of safer rail lines

题型:名词解释

伴随着科学技术的进步和人民生活水平的提高,消费者对水果品质的要求越来越高。他们不仅对色、型、味等感官品质有较高的要求,而且对食品的污染和毒害问题越来越担心。因而生产无公害食品,无疑是当前激烈的农产品市场竞争中以优取胜的途径之一。所以我们说无公害食品是满足人们需求的理想食品,是农产品生产发展的一种必然要求,也是农业生产步入现代化的一个重要标志。
为了与世界发展潮流相适应,农业部曾于1990年将无公害食品定名为“绿色食品”。绿色食品是安全、营养无公害类食品的统称。它是一个庞大的家族,主要包括粮食、蔬菜、水果、畜禽、水产等系列。由于与环境保护有关,通常都形象地冠以“绿色”二字。
绿色食品向人们提出了一个新的食品质量概念。其核心有三方面的含义:一是安全,二是营养,三是好吃。前两条是最基本的。俗话说:“民以食为天”。这充分说明了食品在人们生活中的突出地位和重要作用,但在不同的历史时期,人们对食品有不同的要求。过去,我国经济比较落后,物质生活不丰富,因而,人们对食品也不敢有过高的奢望,只讲填饱肚子,根本谈不上安全、营养、好吃。

绿色食品包括:

A.蔬菜
B.粮食
C.水果及水产
D.蔬菜、粮食、水果及水产

题型:名词解释

在什么情况下需将运行中的变压器差动保护停用?

题型:名词解释

血清补体增高常见于()

A.急性肾小球肾炎

B.慢性肾小球肾炎

C.急性炎症

D.狼疮性肾炎

E.自身免疫性溶血性贫血

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