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   684111篇
  免费   63094篇
  国内免费   43597篇
电工技术   50262篇
综合类   57847篇
化学工业   88420篇
金属工艺   43933篇
机械仪表   42288篇
建筑科学   43815篇
矿业工程   23687篇
能源动力   17779篇
轻工业   71315篇
水利工程   19774篇
石油天然气   20755篇
武器工业   8734篇
无线电   72701篇
一般工业技术   73358篇
冶金工业   52711篇
原子能技术   12759篇
自动化技术   90664篇
  2024年   2119篇
  2023年   8083篇
  2022年   20580篇
  2021年   26767篇
  2020年   19189篇
  2019年   13807篇
  2018年   15489篇
  2017年   17366篇
  2016年   15903篇
  2015年   24126篇
  2014年   31509篇
  2013年   41336篇
  2012年   47976篇
  2011年   51638篇
  2010年   48538篇
  2009年   47145篇
  2008年   48773篇
  2007年   47860篇
  2006年   40610篇
  2005年   33689篇
  2004年   25302篇
  2003年   17609篇
  2002年   16641篇
  2001年   15624篇
  2000年   12878篇
  1999年   7202篇
  1998年   11196篇
  1997年   7990篇
  1996年   6121篇
  1995年   4692篇
  1994年   3893篇
  1993年   3893篇
  1992年   2894篇
  1991年   2691篇
  1990年   2575篇
  1989年   2625篇
  1988年   2467篇
  1987年   2179篇
  1986年   2131篇
  1985年   2389篇
  1984年   2225篇
  1983年   2040篇
  1982年   1903篇
  1981年   2011篇
  1980年   1939篇
  1979年   1904篇
  1978年   1759篇
  1977年   2089篇
  1976年   2665篇
  1973年   1592篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
991.
992.
Michael F. Wilson  Jerry F. Kriz 《Fuel》1985,64(8):1179-1180
In response to an interpretation made by Moore and Akgerman of data taken from a recent publication, previously unexplainable phenomena are accounted for, based on new experimental results. These relate to a thermodynamic equilibrium reaction involving saturation of aromatic hydrocarbons in synthetic crude middle distillates.  相似文献   
993.
The effect on ambient aerosols of exposure to the conditions of the respiratory system was determined by sampling simultaneously through two dichotomous samplers in parallel. In one of the samplers the aerosol was brought to 37°C and near 100% relative humidity before passing through the virtual impactor. The results show that, as a result of humidification, about 10–15% by mass of the aerosol which would normally been collected in the fine (less than 2.5 μm aerodynamic diameter) fraction of the sample grows sufficiently when humidified to be collected with the coarse fraction. It is suggested that the direct application to inhalation studies of dichotomous sampler results should be approached with some caution.  相似文献   
994.
Unsaturated Polyester resins were prepared by the reaction of cinnamylsuccinic acid with saturated diols, namely, ethylene, diethylene, propylene, dipropylene, tetramethylene, and hexamethylene glycols, and the unsaturated diols, namely, 1,4-butene- and 1,4-butynediols. All the polyester resins obtained have been characterized and were found to cure with styrene, with relatively low conversions. The properties of the cured polyesters in the form of films were determined. IR and 1H-NMR spectroscopy were used for both qualitative and quantitative analyses of the polyesters and their hydrolyzate products, after curing with styrene.  相似文献   
995.
The surface treatment of a sepiolite with two different titanate coupling agents has been studied. The results obtained from several chemical and physical analytical methods used for the organophylized surface characterization have shown a monolayer reaction has taken place. An attempt to relate the degree of organophylization to the specific surface decrease of filler has been made.  相似文献   
996.
To determine the transport properties of oxide scales growing on an alloy, a laboratory apparatus was developed which allows plotting of characteristic V = f (i) curves and oxidation with an applied electric field. The apparatus and formalism used are described; it appears that such experimental procedures allow determination of the mean ionic transport number, ti; the conductivity values σ, σi, and σ,e; and the effective charge, Z*, of the moving species in the oxide scale (A12O3 in the present case).  相似文献   
997.
A mixture of vanadyl porphyrin complexes was obtained from a metal-porphyrin concentrate (MPC) isolated from crude petroleum by selective extraction. The petroleum MPC was subjected to demetallization and the subsequent introduction of the vanadyl cation into the porphyrin ring. It was shown that the mixture of vanadyl-porphyrin complexes obtained from MPC catalyzes the cyclohexene epoxidation reaction. On the basis of experimental data, it was assumed that the mechanism of olefin oxygenation in the presence of vanadyl porphyrin complexes is similar to the mechanism of the Prilezhaev epoxidation reaction of unsaturated compounds.  相似文献   
998.
浅谈克东县水土流失的成因及存在的问题   总被引:1,自引:1,他引:0  
克东县属丘陵地带,土壤主要是黑土。近年来由于水土流失严重,对农业生产和农民生活带来了极大的不便。虽然采取治理与开发相结合的措施,取得了一定成绩,但目前的任务仍然艰巨。  相似文献   
999.
通过西霞院水利枢纽工程泄洪闸振冲碎石桩基础处理施工方法论述,给出了加砂层振冲碎石桩施工造孔水压、水量、成孔速度、填料级配、填料方法以及振密电流值、留振时间等施工控制参数。  相似文献   
1000.
王颖生  赵志星  成富全  赵勇 《钢铁》2006,41(8):16-18,23
介绍了首钢原料条件下配加扬地粉对烧结生产影响的实验室研究.随着扬地粉配入量的增加,烧结矿转鼓强度、成品率改善,燃耗有少量上升,利用系数增加,低温还原粉化指数变差.研究结果表明:在首钢目前条件下,配入10%~20%的扬地粉是可行的.二烧车间进行了扬地粉工业试验,其最高配比达到30%,工业试验时烧结各项指标变化与实验室试验结果基本一致.  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