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   241711篇
  免费   2633篇
  国内免费   427篇
电工技术   4296篇
综合类   257篇
化学工业   39478篇
金属工艺   9393篇
机械仪表   7413篇
建筑科学   5460篇
矿业工程   1392篇
能源动力   5160篇
轻工业   24840篇
水利工程   2476篇
石油天然气   5092篇
武器工业   32篇
无线电   25059篇
一般工业技术   44830篇
冶金工业   45514篇
原子能技术   5956篇
自动化技术   18123篇
  2021年   2108篇
  2019年   2021篇
  2018年   3495篇
  2017年   3431篇
  2016年   3692篇
  2015年   2241篇
  2014年   3907篇
  2013年   10197篇
  2012年   6162篇
  2011年   8317篇
  2010年   6559篇
  2009年   7242篇
  2008年   7608篇
  2007年   7731篇
  2006年   6898篇
  2005年   6060篇
  2004年   5829篇
  2003年   5604篇
  2002年   5680篇
  2001年   5566篇
  2000年   5391篇
  1999年   5310篇
  1998年   12622篇
  1997年   8917篇
  1996年   6873篇
  1995年   5343篇
  1994年   4757篇
  1993年   4638篇
  1992年   3671篇
  1991年   3390篇
  1990年   3595篇
  1989年   3476篇
  1988年   3307篇
  1987年   2905篇
  1986年   2940篇
  1985年   3375篇
  1984年   3225篇
  1983年   2900篇
  1982年   2744篇
  1981年   2826篇
  1980年   2724篇
  1979年   2625篇
  1978年   2689篇
  1977年   2956篇
  1976年   3814篇
  1975年   2371篇
  1974年   2244篇
  1973年   2376篇
  1972年   1970篇
  1971年   1858篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
971.
A method of calculating the temperature resistance coefficient and its temperature dependence for resistive materials in the approximation of a matrix-statistical structure is outlined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 477–481, September, 1985.  相似文献   
972.
Cookies enriched with 0, 5, 10, 15, 20, and 25% full-fat sweet lupine flour (FFSL) were evaluated by a sensory panel using the rank of preference and paired comparison tests. Cookies with 0, 5, and 10% FFSL were preferred while those containing 20 and 25% FFSL were rejected (p≤0.01). Studies conducted with school children showed similar acceptability for 0 and 10% FFSL-containing cookies which was different (p = 0.05) from those containing 20% FFSL. Fortification of the basic formula with 10% FFSL was recommended on the basis of acceptability.  相似文献   
973.
Over the last decade there has been much interest shown in the use of textiles in civil engineering construction, particularly in geotechnical engineering where geotextiles are associated with soil. Is this a fad, or something more profound and durable? In attempting to rationalize this dramatic development it is concluded that geotextiles do offer many technical and economic advantages. However, at present geotextiles are commonly used as a replacement for traditional building materials using traditional construction methods rather than more innovative techniques that could only be employed using geotextiles. It is concluded that the development of these techniques is the real future of geotextiles and that this future can only be secured by the close cooperation of both textile and civil engineers.  相似文献   
974.
It is shown that the corrosion resistance of automobile sheet can be improved by ensuring that steels of this type have a low content of corrosion-active nonmetallic inclusions (CANI). The main mechanisms responsible for the formation of CANI in automobile sheet have been established, and recommendations have been developed to reduce their concentration in this product • optimize the deoxidation processes that are used by ensuring that the proportions of the additions made to the steel are consistent with the composition of the ladle slag and that certain key temperature-time parameters of these processes are maintained • control the composition of the ladle slag to prevent the formation of solid phases in the slag and their transfer to the metal; certain conditions must also be observed in the argon blow and the introduction of the addtions. Use of the above recommendations to make automobile sheet and tube steels cleaner with respect to their content of CANI and thus help optimize out-of-furnace treatments at metallurgical and pipe plants will make it possible to improve the corrosion resistance of metal products used in automotive manufacturing. __________ Translated from Metallurg, No. 2, pp. 45–48, February, 2006.  相似文献   
975.
The San Diego County Water Authority of California has initiated planning for coastal desalination facilities to augment their water supplies. Integration of the different water qualities from these facilities into existing pipelines must be achieved. This investigation determined whether, and to what degree, consumers can discriminate between desalinated seawater and imported water supplies and how these investigations can contribute to decision making regarding the need for construction of facilities to blend such supplies prior to delivery. Based upon the results of the flavour profile analysis panel and the consumer evaluation sessions, it was concluded that free chlorine versus chloramine disinfection or different concentrations of disinfectants did not significantly affect consumer perception of the taste and odour of desalinated seawater or blends with Colorado River water and State project water. Consumers were able to discern between desalinated seawater and imported water, preferring imported water when forced to make a choice. However, the investigators did not believe that the difference in consumer perception was significant enough to warrant special blending facilities to mitigate the relatively minor aesthetic quality differences between imported water supplies and desalinated seawater.  相似文献   
976.
977.
Operation of a 16-tap fiber-optic delay line configured as a bandpass filter with a fundamental frequency of 2.0 GHz over the frequency range from 0 to 12.5 GHz is discussed. Equal tap weights and spacings were used to facilitate comparison of experimental and predicted results. More than 1011 analog multiplications per second are performed in this relatively simple signal processing system. Other processors for performing functions such as matched filtering and correlation can be implemented by appropriate choice of the mirror reflectances and fiber lengths  相似文献   
978.
979.
Beta-lactamase-producing mutants of Streptococcus cremoris   总被引:1,自引:0,他引:1  
Penicillin-resistant mutants were isolated for six strains of Streptococcus cremoris used in commercial Cheddar cheese manufacture after treatment with N-methyl-N-nitro-N-nitrosoguanidine. The resistant mutants had an elevated minimal growth inhibitory concentration, 2.5 micrograms (4.13 units)/ml, for penicillin G and other beta-lactam antibiotics as compared with the penicillin-susceptible parent strains, which were each sensitive to .05 micrograms (.08 units)/ml. Penicillin resistance was due to the production of beta-lactamase. Plasmid DNA was not demonstrated in partially purified lysates of four mutants. Mutants had normal cellular morphology but altered phage sensitivity patterns. All except one strain were able to support complete phage adsorption. Resistance was retained after 20 passages in absence of penicillin.  相似文献   
980.
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