首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4804篇
  免费   158篇
  国内免费   10篇
电工技术   68篇
综合类   29篇
化学工业   1349篇
金属工艺   109篇
机械仪表   93篇
建筑科学   298篇
矿业工程   8篇
能源动力   77篇
轻工业   436篇
水利工程   26篇
石油天然气   2篇
无线电   293篇
一般工业技术   842篇
冶金工业   789篇
原子能技术   40篇
自动化技术   513篇
  2021年   61篇
  2020年   50篇
  2019年   67篇
  2018年   77篇
  2017年   64篇
  2016年   100篇
  2015年   83篇
  2014年   116篇
  2013年   221篇
  2012年   181篇
  2011年   268篇
  2010年   194篇
  2009年   175篇
  2008年   202篇
  2007年   196篇
  2006年   147篇
  2005年   168篇
  2004年   140篇
  2003年   113篇
  2002年   93篇
  2001年   90篇
  2000年   88篇
  1999年   97篇
  1998年   145篇
  1997年   114篇
  1996年   89篇
  1995年   88篇
  1994年   81篇
  1993年   87篇
  1992年   78篇
  1991年   57篇
  1990年   84篇
  1989年   54篇
  1988年   50篇
  1987年   63篇
  1986年   54篇
  1985年   65篇
  1984年   60篇
  1983年   51篇
  1982年   58篇
  1981年   45篇
  1980年   38篇
  1979年   46篇
  1978年   50篇
  1977年   77篇
  1976年   49篇
  1975年   42篇
  1974年   59篇
  1972年   46篇
  1970年   40篇
排序方式: 共有4972条查询结果,搜索用时 265 毫秒
31.
Thirty-four heifers (24 Holstein, 8 Ayrshire, 2 Jersey) and 12 Holstein steer calves were grouped into 23 blocks of 2 animals each according to breed, sex, and body weight. Animals in each block were randomly assigned to control or treated groups. The treated group received an anthelmintic bolus containing morantel tartrate before they were permitted access to pasture. A 2.6 ha pasture was divided in half with a double fence; the resulting two pastures had separate feed and water troughs. Steer calves were slaughtered upon termination of the trial to ascertain gastrointestinal parasite burdens. Two worm-free tracer calves were placed on each pasture every 2 mo and slaughtered after 4 wk of grazing to determine parasite infectivity of pastures. Herbage samples were obtained monthly and analyzed for infective larvae. The trial was conducted for 141 d during the grazing season. Treatment resulted in 90% reduction in infective larvae on pasture, 74% reduction in fecal worm-eggs, 91% reduction in adult worm burdens, and a trend toward reduced worm burdens in tracer calves by 52%. An overall average daily gain of .68 and .88 kg was obtained for control and treated animals. Reproductive data for the heifers remaining in the herd from the trial showed that treatment resulted in 44 less days to first breeding.  相似文献   
32.
European consumers, in general, have negative attitudes towards the use of gene technology in food production. The objective of this study was to examine whether taste and health benefits influence the acceptability of genetically modified (gm) products when they are presented as real product alternatives. Consumers in Denmark, Finland, Norway and Sweden (n=738) assessed two cheeses: one was labelled as genetically modified (preferred in an earlier product test) and the other as conventional (neutral in an earlier product test). A smaller control group received two cheeses with blind codes. Labelling decreased consumers' intentions to buy the originally preferred gm-labelled cheese, but still the intentions were at the same level with the conventionally labelled option. Participants chose two gm cheeses out of five possible when given the option to take cheese home after tasting. Intentions to buy gm cheese could best be explained by respondents' attitudes towards gene technology and perceived taste benefits. General health interest was also a reinforcer of intentions for gm cheese with reduced fat content.  相似文献   
33.
34.
Works of adhesion WSL between aqueous solutions with pH values in the range from 1 to 14 and carbon fibers from different sources, which were additionally treated in an inert atmosphere or in oxygen, were measured by use of a microbalance. These works of adhesion WSL were found to show distinct stepwise dependencies on the pH value. The works of adhesion WSL are attributed to dispersion interactions WSL1 and various acid-base interactions wslab—in the latter case between the acidic and basic surface groups of carbon and the various basic and acidic aqueous solutions.  相似文献   
35.
36.
The proposed new color-difference formula of CIE TC 129, which is a modified version of CIELAB, was tested with a recently published data set of textile pass/fail judgments. Goodness of fit is improved, if the parameter of lightness is set near 2, and if, additionally, a weight function for lightness is defined that reduces the weight of a lightness difference with lightness level in relation to chroma or hue scaling. © 1994 John Wiley & Sons, Inc.  相似文献   
37.
改进的DMT/PTA工艺技术是由苏尔寿化工有限公司和H&G Hegmanns公司联合开发的。该技术对Witten-Katzschmann工艺进行了大量改进,并结合了苏尔寿公司的环境友好熔融结晶技术。改进的工艺包括:氧化反应部分(有效回收了副产品和能量);粗酯和副产品蒸馏;采用熔融结晶技术精制DMT。  相似文献   
38.
[Correction Notice: An erratum for this article was reported in Vol 29(6) of Journal of Experimental Psychology: Learning, Memory, and Cognition (see record 2007-16865-001). On page 684, Table 4, all correlations should have been identified as having a pp then q") as indicating a high conditional probability P(q|p). Participants estimated the probability that a given conditional is true (Experiments 1A, 1B, and 3) or judged whether a conditional was true or false (Experiments 2 and 4) given information about the frequencies of the relevant truth table cases. Judgments were strongly influenced by the ratio of pq to p?q cases, supporting the conditional probability account. In Experiments 1A, 1B, and 3, judgments were also affected by the frequency of pq cases, consistent with a version of mental model theory. Experiments 3 and 4 extended the results to thematic conditionals and showed that the pragmatic utility associated with believing a statement also affected the degree of belief in conditionals but not in logically equivalent quantified statements. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
39.
Steel production is an energy- and water-intensive process: large quantities of water are used for cooling, process and environmental-technical applications. In the mid-1990s, Arcelor Gent, a large integrated carbon steel producing company in Flanders (Belgium), started a number of water-related projects: the existing water infrastructure was adapted: the water from the coke plant was biologically treated; canal water was demineralised using reverse osmosis; waste water from the blast furnaces was neutralised with alkaline water from the steel plant. As a result of these projects, the quantity of discharged waste water was reduced by a factor of 2 (water recycling doubled from a factor of 10 to a factor of 20), and the discharge of pollutants decreased. Also resource consumption decreased: lime used in the steel plant, could be recovered to precipitate Zn in the waste water of the blast furnaces. Arcelor Gent obtained for these projects several Environmental Awards.  相似文献   
40.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号