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   234652篇
  免费   17994篇
  国内免费   9540篇
电工技术   12809篇
技术理论   24篇
综合类   14694篇
化学工业   39669篇
金属工艺   13367篇
机械仪表   14904篇
建筑科学   18057篇
矿业工程   7677篇
能源动力   6587篇
轻工业   13862篇
水利工程   3739篇
石油天然气   17072篇
武器工业   1740篇
无线电   25708篇
一般工业技术   27993篇
冶金工业   13036篇
原子能技术   2361篇
自动化技术   28887篇
  2024年   1022篇
  2023年   3877篇
  2022年   6648篇
  2021年   9353篇
  2020年   7286篇
  2019年   6182篇
  2018年   6897篇
  2017年   7701篇
  2016年   6894篇
  2015年   9090篇
  2014年   11571篇
  2013年   13614篇
  2012年   14600篇
  2011年   15881篇
  2010年   13801篇
  2009年   12997篇
  2008年   12732篇
  2007年   12210篇
  2006年   12691篇
  2005年   11040篇
  2004年   7447篇
  2003年   6384篇
  2002年   5623篇
  2001年   5034篇
  2000年   5576篇
  1999年   6595篇
  1998年   5534篇
  1997年   4547篇
  1996年   4268篇
  1995年   3572篇
  1994年   2860篇
  1993年   1998篇
  1992年   1557篇
  1991年   1248篇
  1990年   950篇
  1989年   766篇
  1988年   560篇
  1987年   340篇
  1986年   286篇
  1985年   199篇
  1984年   142篇
  1983年   118篇
  1982年   125篇
  1981年   103篇
  1980年   74篇
  1979年   36篇
  1978年   28篇
  1977年   20篇
  1976年   36篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
开办农民工夜校是提升农民工素质的有效途径.分析了建筑业农民工夜校开展法制教育的意义,阐述了建筑业农民工夜校法制课程教学应遵循的原则、教学内容的安排和教学手段、方法的选择.  相似文献   
992.
993.
A new method for calculating the eigenmodes of gyrotron resonators is presented. With this method, the resonant frequency, Q-factor and field profiles of the eigenmodes are determined through finding the minimum value of a function of two variables, namely the resonant frequency and the Q-factor. Compared with the traditional calculation method, the new method predicts a significantly higher Q-factor of the eigenmodes.  相似文献   
994.
Growth of hydrophobic TiO2 on wood surface using a hydrothermal method   总被引:2,自引:0,他引:2  
Hydrophobic titanium dioxide (TiO2) was successfully grown on a wood surface using a hydrothermal method. Energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and water contact angle (WCA) were employed to characterize the features of grown TiO2 and its hydrophobicity. EDS, XRD, and FTIR proved that anatase TiO2 chemically bonded to the wood surface through the combination of hydrogen groups during the hydrothermal process. The values of WCAs manifested that the hydrophobicity of the treated wood was mainly dependent on specific reaction conditions, especially on reaction pH value and hydrothermal temperature. The highest WCA reached 154° when the hydrothermal temperature was 130 °C. The treated wood thus possessed a superhydrophobic surface.  相似文献   
995.
This study builds the interdisciplinary knowledge network of China, which is used to catch the knowledge exchange structure of disciplines, and investigates the evolution process from 1981 to 2010. A network analysis was performed to examine the special structure and we compare state of the networks in different periods to determine how the network has got such properties. The dataset are get from the reference relationship in literature on important Chinese academic journals from 1980 to 2010. The analytical results reveal the hidden network structure of interdisciplinary knowledge flows in China and demonstrate that the network is highly connected and has a homogeneous link structure and heterogeneous weight distribution. Through comparing of the network in three periods, that is 1981–1990, 1991–2000 and 2001–2010, we find that the special evolution process, which is limited by the number of nodes, play an important influence on interdisciplinary knowledge flows.  相似文献   
996.
997.
In this paper, an anti-fouling composite coating was fabricated by blending zinc-graphite alloy powders with epoxy-silicone resin and characterized by EDS, SEM, XRD and ion titration. Compared with stainless steel and epoxy-silicone resin coating, the composite coating significantly inhibited the deposition of CaCO3 fouling. Only a small amount of fouling was observed on the surface of composite coating after it was immersed in CaCl2/NaHCO3 solution. The galvanic corrosion of zinc-graphite powders could release Zn2+ ions, which can reduce partially the nucleation and crystal growth rate of CaCO3 on the surface of composite coating. It was found that the morphologies of CaCO3 fouling changed from calcite to aragonite as the existence of composite coating. Meanwhile, CaCO3 fouling was prone to precipitate in bulk solution rather than on the surface of composite coating.  相似文献   
998.
A facile and sustainable mechanochemical route for the synthesis of undoped polydiphenylamine (PDPA) and inorganic acid doped nanostructures are reported. Field emission scanning electron microscopic (FESEM) images highlighted the formation of distinctly different nanostructures for each of the inorganic acid doped PDPA. Elemental analysis carried out for the polymers revealed the presence of more repeating units in their backbone. The X-ray diffraction (XRD) results of the as-prepared PDPA nanostructures indicated the high degree of crystallinity ever reported for PDPA. Spectroscopic profile of the polymers showed that the prepared PDPA is in a doped conducting form. Electrochemical studies performed for the polymeric particles ascertained the redox behaviour and the good electrochemical activity of obtained PDPA samples. The probable mechanistic aspect behind the formation of PDPA nanostructures through this simple and efficient route is discussed.  相似文献   
999.
Editorial     
  相似文献   
1000.
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