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   145787篇
  免费   6296篇
  国内免费   3361篇
电工技术   4405篇
技术理论   7篇
综合类   6415篇
化学工业   21702篇
金属工艺   8315篇
机械仪表   6934篇
建筑科学   6902篇
矿业工程   2534篇
能源动力   3073篇
轻工业   7574篇
水利工程   2220篇
石油天然气   4146篇
武器工业   547篇
无线电   16468篇
一般工业技术   23765篇
冶金工业   5679篇
原子能技术   1197篇
自动化技术   33561篇
  2024年   341篇
  2023年   1170篇
  2022年   1932篇
  2021年   2702篇
  2020年   2078篇
  2019年   1703篇
  2018年   16079篇
  2017年   15339篇
  2016年   11700篇
  2015年   3188篇
  2014年   3540篇
  2013年   4106篇
  2012年   7187篇
  2011年   13692篇
  2010年   11963篇
  2009年   9092篇
  2008年   10264篇
  2007年   11110篇
  2006年   3508篇
  2005年   4081篇
  2004年   3138篇
  2003年   2892篇
  2002年   2273篇
  2001年   1621篇
  2000年   1746篇
  1999年   1589篇
  1998年   1287篇
  1997年   1083篇
  1996年   1035篇
  1995年   755篇
  1994年   651篇
  1993年   426篇
  1992年   357篇
  1991年   296篇
  1990年   211篇
  1989年   177篇
  1988年   151篇
  1987年   77篇
  1986年   90篇
  1985年   46篇
  1984年   37篇
  1983年   37篇
  1968年   43篇
  1966年   42篇
  1965年   45篇
  1959年   40篇
  1958年   37篇
  1957年   36篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
The focused ion beam technique was employed to investigate the atmospheric corrosion morphology of AZ91D. It was found that the α matrix of the alloy was preferentially corroded in the areas adjacent to intermetallic phases. The most interesting finding was that the corrosion products in corrosion cavities were pelletlike, which has never been reported before.  相似文献   
2.
试论绩效考核反馈--面谈   总被引:1,自引:0,他引:1  
谢戈 《中国锰业》2006,24(1):53-55
从剖析绩效考核反馈案例入手,分析和论述了绩效反馈面谈的目的、任务、内容、原则和技巧,指明了面谈是绩效考核反馈的黄金途径,提出了面谈的具体做法和要求。为企业人力资源管理者掌握绩效考核面谈及开展此项面谈工作提供一些参考和借鉴。  相似文献   
3.
4.
Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical composition (CaO)0.75(La203)0.20(Fe2O3)6 was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO3)2 and (NH4)2HPO4 maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites could be useful for hyperthermia.  相似文献   
5.
Chloride doped polyaniline conducting polymer films have been prepared in a protic acid medium (HCl) by potentiodynamic method in an electrochemical cell and studied by cyclic voltammetry and FTIR techniques. The FTIR spectra confirmed Cl- ion doping in the polymers. The polymerization rate was found to increase with increasing concentration of aniline monomer. But the films obtained at high monomer concentration were rough having a nonuniform flaky polyaniline distribution. Results showed that the polymerization rate did not increase beyond a critical HCl concentration. Cyclic voltammetry suggested that, the oxidation-reduction current increased with an increase in scan rate and that the undoped polyaniline films were not hygroscopic whereas chloride doped polyaniline films were found to be highly hygroscopic.  相似文献   
6.
1 Introduction Propylene as an important feedstock for organic chemicals is mainly originated from steam cracking and catalytic cracking processes. During the FCC process the propylene content varies with the FCC catalyst and process technology adopted, resulting in significant difference in propylene concentration in the cracked product——LPG. The conventional FCC pro- cess generally gives a propylene yield of around 4%, while the FCC process with maximization of propylene yield can in…  相似文献   
7.
A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec.  相似文献   
8.
OA系统中的工作流技术及其新的模式   总被引:1,自引:0,他引:1  
本文在对工作流技术的理论、实现和应用研究的基础上,提出了审批平台中应用的工作流管理模型,详细讨论了该技术的实现方法,并提出了工作流技术的新模式.  相似文献   
9.
10.
带隔板底水油藏油井临界产量计算公式   总被引:25,自引:9,他引:16  
本给出了带隔板底水油藏油井的监界产量计算公式,它适用于所有带隔板底水油藏的油井。  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