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   243181篇
  免费   5243篇
  国内免费   2025篇
电工技术   5334篇
技术理论   2篇
综合类   2377篇
化学工业   38188篇
金属工艺   12350篇
机械仪表   9264篇
建筑科学   6924篇
矿业工程   3077篇
能源动力   5506篇
轻工业   15125篇
水利工程   3435篇
石油天然气   10319篇
武器工业   223篇
无线电   26037篇
一般工业技术   49841篇
冶金工业   36422篇
原子能技术   7017篇
自动化技术   19008篇
  2022年   2279篇
  2021年   3433篇
  2020年   2602篇
  2019年   2878篇
  2018年   4633篇
  2017年   4857篇
  2016年   5028篇
  2015年   3572篇
  2014年   5492篇
  2013年   10921篇
  2012年   7810篇
  2011年   9642篇
  2010年   8045篇
  2009年   8501篇
  2008年   8612篇
  2007年   8485篇
  2006年   7588篇
  2005年   6869篇
  2004年   5825篇
  2003年   5583篇
  2002年   5363篇
  2001年   5333篇
  2000年   5074篇
  1999年   5280篇
  1998年   11115篇
  1997年   7994篇
  1996年   6314篇
  1995年   4752篇
  1994年   4140篇
  1993年   4212篇
  1992年   3320篇
  1991年   3248篇
  1990年   3083篇
  1989年   3020篇
  1988年   3000篇
  1987年   2610篇
  1986年   2645篇
  1985年   2909篇
  1984年   2743篇
  1983年   2584篇
  1982年   2335篇
  1981年   2293篇
  1980年   2362篇
  1979年   2370篇
  1978年   2384篇
  1977年   2493篇
  1976年   2883篇
  1975年   2190篇
  1974年   2072篇
  1973年   2171篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Power Technology and Engineering - The major results from the survey and geotechnical monitoring during the leveling of the model foundation of the Zagorsk PSP-2 in test site No. 3 are presented....  相似文献   
92.
Hexagonal barium ferries is a promising and efficient microwave (MW) absorbing material, but the low dielectric loss and poor conductivity have limited their extensive applications. In this work, a simple tactic of coating conductive polymer PANI on hexaferrite BaCo2Fe16O27 is presented, wherein the dielectric properties are customized, and more significantly, the electromagnetic loss is greatly enhanced. As displayed from structural characterizations, PANI were coated equably on the surface of hexaferrite grains by an in-situ polymerization process. The outcomes exhibit the as-prepared PANI@hexaferrite composite has remarkable electromagnetic wave absorption capacity. When the thickness is 6.0 mm, the minimal RL of ?40.4 dB was achieved at 2.9 GHz. The effective absorption bandwidth (RL < ?20 dB) of 0.65 GHz, 0.53 GHz, 0.65 GHz, 0.52 GHz, 0.46 GHz and 0.39 GHz was achieved separately when the thickness ranges from 4 to 9 mm. The highly efficient MW absorbing performance of PANI@hexaferrite composite were the consequence of multiple loss mechanisms and perfect impedance matching. It is demonstrated that the PANI@hexaferrite composite with excellent MW absorption performance is expected to be potential MW absorbers for extensive applications.  相似文献   
93.
Journal of Communications Technology and Electronics - Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice...  相似文献   
94.
The chromium (Cr) evaporation behavior of several different types of iron (Fe)-based AFA alloys and benchmark Cr2O3-forming Fe-based 310 and Ni-based 625 alloys was investigated for 500 h exposures at 800 °C to 900 °C in air with 10% H2O. The Cr evaporation rates from alumina-forming austenitic (AFA) alloys were ~5 to 35 times lower than that of the Cr2O3-forming alloys depending on alloy and temperature. The Cr evaporation behavior was correlated with extensive characterization of the chemistry and microstructure of the oxide scales, which also revealed a degree of quartz tube Si contamination during the test. Long-term oxidation kinetics were also assessed at 800 to 1000 °C for up to 10,000 h in air with 10% H2O to provide further guidance for SOFC BOP component alloy selection.  相似文献   
95.
Power Technology and Engineering - The monitoring of hydraulic structures as high-risk facilities is discussed. Monitoring should ensure the reliability and functioning of a hydraulic structure...  相似文献   
96.
Theoretical Foundations of Chemical Engineering - A choline chloride–sulfosalicylic acid deep eutectic solvent (DES) is proposed for dissolving the oxides Co(II), Cu(II), Zn(II), Fe(III),...  相似文献   
97.
Atomic Energy - The results of calculations and experimental determination of the neutronics characteristics of the IRT-T research reactor are presented. The IRT-T reactor is a pool reactor with...  相似文献   
98.
Journal of Inorganic and Organometallic Polymers and Materials - The reaction of potassium tetracyanocupprate(I) with triethyltin bromide in presence of phenanthroline (Phen) and quinoxaline (Qox)...  相似文献   
99.
Strength of Materials - The paper addresses the investigation of high-strain rate compressive behavior of Al foams subjected to impact at the intermediate striking velocity ranged from 40 to...  相似文献   
100.
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