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   53903篇
  免费   6249篇
  国内免费   4042篇
电工技术   3237篇
综合类   5015篇
化学工业   8991篇
金属工艺   2821篇
机械仪表   3162篇
建筑科学   5734篇
矿业工程   2448篇
能源动力   2132篇
轻工业   3368篇
水利工程   1868篇
石油天然气   2841篇
武器工业   658篇
无线电   7154篇
一般工业技术   8175篇
冶金工业   2443篇
原子能技术   1118篇
自动化技术   3029篇
  2024年   348篇
  2023年   1030篇
  2022年   1698篇
  2021年   2017篇
  2020年   2132篇
  2019年   1901篇
  2018年   1703篇
  2017年   2141篇
  2016年   2097篇
  2015年   2244篇
  2014年   3130篇
  2013年   3345篇
  2012年   3805篇
  2011年   4048篇
  2010年   3021篇
  2009年   3096篇
  2008年   2875篇
  2007年   3443篇
  2006年   3146篇
  2005年   2602篇
  2004年   2243篇
  2003年   1935篇
  2002年   1708篇
  2001年   1334篇
  2000年   1223篇
  1999年   992篇
  1998年   793篇
  1997年   731篇
  1996年   619篇
  1995年   533篇
  1994年   461篇
  1993年   372篇
  1992年   300篇
  1991年   243篇
  1990年   208篇
  1989年   169篇
  1988年   126篇
  1987年   73篇
  1986年   45篇
  1985年   34篇
  1984年   42篇
  1983年   25篇
  1982年   25篇
  1981年   12篇
  1980年   22篇
  1979年   28篇
  1965年   6篇
  1963年   5篇
  1959年   11篇
  1951年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
TiO2 hybrid molecular imprinted polymer (MIP) for ethofumesate using methacrylic acid (MAA) as the functional monomer and silane coupling agent 3-(trimethoxysilyl) propylmethacrylate (KH570) as organic–inorganic connective bridge was synthesized via photo-excitation method. Hydrogen bond was proved to act between MAA and ethofumesate for pre- and post-polymerization binding properties as testified by UV spectrometric method. KH570 modified TiO2 nanoparticles were prepared via sonochemical reaction, which can accelerate hydrolysis, increase collision chance for the reactive system and improve the dispersion of the nanoparticles. Scanning electron microscope (SEM), transmission electron microscope (TEM), binding and the adsorption kinetics experiments as well as thermogravimetric analysis (TGA) were employed for characterization. The results indicated that the hybrid MIP revealed a larger surface area and more ordered imprinting cavities with improved thermal stability compared to organic-only MIP. Furthermore, faster adsorption kinetics and enhancive adsorption capacity were achieved, which made it promising in chemical sensor applications.  相似文献   
102.
Polymer matrix RE-Fe giant magnetostrictire composite (GMPC) was prepared using bonding and magnetic field forming technique, and magnetostriction of samples was measured for different compressive stress. The experimental results show thai there is certain compressive effect in GMPC. And the influence of compressive stress on magnetostriction of sample was investigated. It offers essential reference for application and device design of GMPC.  相似文献   
103.
本文详细分析了解吸塔换热器结堵的原因和对环保装置正常运行的影响,并针对性地提出了防范和处理措施。  相似文献   
104.
The modelling of hydromechanical behavior of clayey sediments by homogenization theory is described. The rheological model of clays buried in depth requires a three-dimensional approach and laboratory experiments to quantify the model parameters. An iterative process which can be coupled to any homogenization method is used to model the porous media behavior. Hydromechanical compaction results from oedometric experiments are simulated with the proposed model.  相似文献   
105.
The effects of NOx on the performance of proton exchange membrane (PEM) fuel cell were investigated through the introduction of a mixture containing NO and NO2, in a ratio of 9:1, into the cathode stream of a single PEM fuel cell. The NOx concentrations used in the experiments were 1480 ppm, 140 ppm and 10 ppm, which cover a range of three orders. The experimental results obtained from the tests of durability, polarization, reversibility and electrochemical impedance spectroscopy (EIS) showed a detrimental effect of NOx on the cell performance. The electrochemical measurements results suggested that the impacts of NOx are mainly resulted from the superposition of the oxygen reduction reaction (ORR), NO and HNO2 oxidation reactions, and the increased cathodic impedance. Complete recovery of the cell performance was reached after operating the cell with clean air and then purging with N2 for hours.  相似文献   
106.
黄志文  郗旭林 《山西冶金》2003,26(2):41-42,56
使用液力偶合器因故障频繁,对高炉稳产、高产造成严重威胁,而且维修费用较高,对偶合器改造后,应用金属迭片挠性联轴器其故障率、维修费用都很低。  相似文献   
107.
Halo effects in rating specific pieces of work, as in educational grading, have received little attention. Grades awarded by 2 independent graders to undergraduate projects were analyzed with a correlated uniqueness model. Grades showed substantial halo despite being awarded by expert assessors at the time of reading the work. There was greater halo between different grades applying to the same section of the project than between grades applying to different sections. Supervisors who had regular contact with the student whose work they were grading showed no more halo than other graders. More reliable graders showed less within-section halo than graders of lower reliability but equal between-sections halo. The halo effects observed cannot be entirely attributable to a unitary general impression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
108.
吴金虎 《液晶与显示》2004,19(2):143-147
介绍了研制出其性能达国际先进公司同类产品水平的塑封双列直插式光耦合器的工作原理和提高绝缘耐压的技术难点,从引线框架设计、加工精度控制、内包封材料选型、理想内包封形状控制、塑封气密性的实现、环境条件的完善等方面讨论了提高绝缘耐压的设计和工艺要点。  相似文献   
109.
动态多目标决策问题的灰色分析方法   总被引:2,自引:0,他引:2  
将用于固定时间截面下静态多目标决策的灰色关联理论推广到动态情形,引入局部理想最优效果和整体理想最优效果的概念,提出一种新型的动态多目标决策问题的灰色关联模型,并通过算例说明该方法的合理可行性。  相似文献   
110.
The fracture toughness of brittle thermoset resins could be improved significantly by perfectly bonded tough, short fibers through both crack trapping and bridging effects. In this paper, the crack trapping effect was studied through the analysis of the change of strain energy associated with the crack propagation across a regular array of fibers, and the bridging effect was discussed based on the Andersson–Bergkvist model. The fracture resistance increases with the fiber volume fraction, and is independent of the elastic properties of the matrix, the crack length, and the cross-sectional diameter of the fibers.  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