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   30288篇
  免费   2319篇
  国内免费   1112篇
电工技术   1494篇
技术理论   2篇
综合类   1720篇
化学工业   5200篇
金属工艺   1858篇
机械仪表   2008篇
建筑科学   2392篇
矿业工程   1011篇
能源动力   794篇
轻工业   1731篇
水利工程   535篇
石油天然气   2080篇
武器工业   213篇
无线电   3223篇
一般工业技术   3713篇
冶金工业   1622篇
原子能技术   353篇
自动化技术   3770篇
  2024年   122篇
  2023年   558篇
  2022年   902篇
  2021年   1254篇
  2020年   1040篇
  2019年   792篇
  2018年   966篇
  2017年   979篇
  2016年   933篇
  2015年   1151篇
  2014年   1443篇
  2013年   1786篇
  2012年   1899篇
  2011年   1910篇
  2010年   1732篇
  2009年   1690篇
  2008年   1576篇
  2007年   1560篇
  2006年   1654篇
  2005年   1372篇
  2004年   887篇
  2003年   842篇
  2002年   750篇
  2001年   626篇
  2000年   674篇
  1999年   810篇
  1998年   694篇
  1997年   628篇
  1996年   555篇
  1995年   461篇
  1994年   354篇
  1993年   264篇
  1992年   198篇
  1991年   157篇
  1990年   117篇
  1989年   100篇
  1988年   80篇
  1987年   52篇
  1986年   50篇
  1985年   24篇
  1984年   23篇
  1983年   16篇
  1982年   18篇
  1981年   11篇
  1980年   7篇
  1979年   1篇
  1966年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
曹长娥 《焊管》2002,25(4):58-60
介绍了日本川崎制铁公司技术研究所开发出的电焊钢管采用热张力减径工艺的特性 ,及这种钢管的高强度、高延性等基本特性。用这种钢管制造的汽车零部件 ,经弯曲、冲击和疲劳特性等实验 ,证明具有良好的机械加工性能 ,是制造汽车用零部件的优良材料。  相似文献   
32.
介绍了国内外乙丙橡胶市场的供需状况,并对我国乙丙橡胶的产业发展提出了建议。  相似文献   
33.
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry  相似文献   
34.
35.
This paper presents the rapid, low-temperature bonding between silicon and steel using the rapid thermal annealing process. Three different thin-film adhesion layer systems including silver, gold, and nickel were utilized as the intermediate bonding material to assist the eutectic Pb/Sn bonding between silicon and steel. The bonding temperature was set at 220/spl deg/C for 20 s, with a 20-s ramp-up time. Five experiments were conducted to determine the strength of the bond, including static tensile and compressive four-point bend tests, axial extension tests, tensile bending fatigue tests, and corrosion resistance tests. The test results have shown that the gold adhesion layer is the most robust, demonstrating minimal creep during fatigue tests, no delamination during the tensile or compressive four-point bend tests, and acceptable strength during the axial extension tests. Additionally, all adhesion layers have withstood four months of submersion in various high-temperature solutions and lubricants without failure. Simulations of the axial stresses and strains that developed during the four-point bend and axial extension tests were performed and showed that the presence of the silicon die provides a local reinforcement of the bond as observed in the experimental tests.  相似文献   
36.
棉织物手感值的模糊综合评判研究   总被引:4,自引:0,他引:4  
利用模糊综合评判数学模型对棉织物的手感值进行了计算与分析,这种方法简单、可靠,与主观评估结果有很好的一致性,为纺织生产的质量判断提供了便利。  相似文献   
37.
3-D MCM封装技术及其应用   总被引:1,自引:0,他引:1  
介绍了超大规模集成电路(VLSI)用的3-D MCM封装技术的最新发展,重点介绍了3-D MCM封装垂直互连工艺,分析了3-D MCM封装技术的硅效率、复杂程度、热处理、互连密度、系统功率与速度等问题,并对3-D MCM封装的应用作了简要说明。  相似文献   
38.
This paper investigates three kinds of permanent-magnet arrays used in planar motors with polarity centers distributed in the lattices of a matrix. The magnetic field of every kind of magnet array is analyzed by analytical methods. First, we give a Laplace equation of magnetic scalar potential and a series of boundary conditions. Then, we derive the analytical expressions of magnet field strength and magnet flux density in the air gap of each kind of magnet array by the method of separation of variables. Finally, we compare the three types of magnet arrays on the basis of the analytical solutions.  相似文献   
39.
Domain-Driven, Actionable Knowledge Discovery   总被引:1,自引:0,他引:1  
Data mining increasingly faces complex challenges in the real-life world of business problems and needs. The gap between business expectations and R&D results in this area involves key aspects of the field, such as methodologies, targeted problems, pattern interestingness, and infrastructure support. Both researchers and practitioners are realizing the importance of domain knowledge to close this gap and develop actionable knowledge for real user needs.  相似文献   
40.
Two fundamental concepts and quantities, realization factors and performance potentials, are introduced for Markov processes. The relations among these two quantities and the group inverse of the infinitesimal generator are studied. It is shown that the sensitivity of the steady-state performance with respect to the change of the infinitesimal generator can be easily calculated by using either of these three quantities and that these quantities can be estimated by analyzing a single sample path of a Markov process. Based on these results, algorithms for estimating performance sensitivities on a single sample path of a Markov process can be proposed. The potentials in this paper are defined through realization factors and are shown to be the same as those defined by Poisson equations. The results provide a uniform framework of perturbation realization for infinitesimal perturbation analysis (IPA) and non-IPA approaches to the sensitivity analysis of steady-state performance; they also provide a theoretical background for the PA algorithms developed in recent years  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