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   296179篇
  免费   3872篇
  国内免费   1438篇
电工技术   5133篇
综合类   558篇
化学工业   44386篇
金属工艺   11653篇
机械仪表   8998篇
建筑科学   6761篇
矿业工程   1622篇
能源动力   8285篇
轻工业   23609篇
水利工程   3180篇
石油天然气   5864篇
武器工业   43篇
无线电   35649篇
一般工业技术   60331篇
冶金工业   52216篇
原子能技术   7619篇
自动化技术   25582篇
  2022年   2303篇
  2021年   3291篇
  2020年   2527篇
  2019年   2993篇
  2018年   4765篇
  2017年   4576篇
  2016年   4787篇
  2015年   3062篇
  2014年   5129篇
  2013年   13373篇
  2012年   7885篇
  2011年   10695篇
  2010年   8328篇
  2009年   9494篇
  2008年   9753篇
  2007年   9674篇
  2006年   8253篇
  2005年   7588篇
  2004年   7446篇
  2003年   7214篇
  2002年   6891篇
  2001年   7006篇
  2000年   6616篇
  1999年   6909篇
  1998年   16564篇
  1997年   11805篇
  1996年   9112篇
  1995年   6996篇
  1994年   6154篇
  1993年   6190篇
  1992年   4491篇
  1991年   4284篇
  1990年   4153篇
  1989年   4136篇
  1988年   3816篇
  1987年   3472篇
  1986年   3461篇
  1985年   3820篇
  1984年   3531篇
  1983年   3285篇
  1982年   3079篇
  1981年   3111篇
  1980年   3080篇
  1979年   2868篇
  1978年   2900篇
  1977年   3173篇
  1976年   4138篇
  1975年   2431篇
  1974年   2387篇
  1973年   2406篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Filled fibrous sorbents modified with transition metal ferro- and ferricyanides capable to recover americium(III) and rare-earth metals(III) from nitric acid solutions were prepared. The most complete and rapid recovery is attained on complex-forming and cation-exchange sorbents (as filled fibrous materials) saturated with nickel ions. The sorbents are characterized by good kinetic properties and can be used for recovery of the above metals.  相似文献   
102.
Samples can be measured with different precisions and reliabilities in different experiments, or even within the same experiment. These varying levels of measurement noise may deteriorate the performance of a pattern recognition system, if not treated with care. Here we seek to investigate the benefit of incorporating prior knowledge about measurement noise into system construction. We propose a kernel density classifier which integrates such prior knowledge. Instead of using an identical kernel for each sample, we transform the prior knowledge into a distinct kernel for each sample. The integration procedure is straightforward and easy to interpret. In addition, we show how to estimate the diverse measurement noise levels in a real world dataset. Compared to the basic methods, the new kernel density classifier can give a significantly better classification performance. As expected, this improvement is more obvious for small sample size datasets and large number of features.  相似文献   
103.
Some substituted coumarins have been synthesized by von-Pechmann condensation using SnCl2 · 2H2O (10 mol %) as catalyst in ethanolic medium. The reactions are simple, easy in handling and environmentally benign.  相似文献   
104.
A range of refractories is presented for handling steel outside a furnace, which are produced by the Borovichi Refractories Corporation. The refractory characteristics and working features are given. Translated from Novye Ogneupory, No. 9, pp. 29–35, September, 2008.  相似文献   
105.
Compositions have been developed for nonshrinking vibrocast thermally insulating light refractory concretes with densities of 1.0, 1.3, 1.5, and 1.8 g/cm3 for temperatures of use up to 1400°C. The structure and properties have been examined for the concrete of density 1.3 g/cm3. __________ Translated from Novye Ogneupory, No. 4, pp. 29–32, April, 2008.  相似文献   
106.
Methods are proposed for designing interpolation models for the preliminary determination and subsequent forecasting of general and fractional breakthrough coefficients for dust used with granular filters, as employed in energy-saving and high-performance dust trapping from technological gases and ventilation discharges in refractory production. The models are supplied with nomograms, which makes them widely suitable for experts working in environmental protection at refractory-producing organizations. The main factors are identified that influence the performance. The results are of interest to experts in related areas of industry such as building materials and engineering ceramics and so on. Translated from Novye Ogneupory, No. 4, pp. 64–67, April, 2008.  相似文献   
107.
108.
109.
Results are presented on the corrosion resistance of chromium-bearing refractories of granular structure acted on by corrosive molten slags, metals, and glasses. It is possible to recommend these refractories to customers for particular conditions of use. Chromium-bearing refractories increase the working lives of furnaces considerably. __________ Translated from Novye Ogneupory, No. 1, pp. 55–61, January, 2008.  相似文献   
110.
In the OAO Borovich Refractory Combine production has been assimilated for a complete set of refractories for continuous steel casting, i.e. from a pipe for protecting a stream of metal to a submerged nozzle. In technical and life characteristics the products correspond to that of world analogs, they provide accident free steel pouring, make it possible to reduce the specific consumption of refractories per ton of steel, to increase CBCM productivity, to reduce billet scrap, and to reduce steel cost. Translated from Novye Ogneupory, No. 8, pp. 4–9, August 2008.  相似文献   
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