全文获取类型
收费全文 | 30288篇 |
免费 | 2319篇 |
国内免费 | 1112篇 |
专业分类
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 |
出版年
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.
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.
33.
Yu‐Qing Cao Zhan Zhang Yan‐Xin Guo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1441-1444
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.
Sosnowchik B.D. Azevedo R.G. Cao A. Lin L. Pisano A.P. 《Advanced Packaging, IEEE Transactions on》2005,28(4):626-634
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.
Jiayong Cao Yu Zhu Jinsong Wang Wensheng Yin Guanghong Duan 《IEEE transactions on magnetics》2004,40(6):3490-3494
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.
Xi-Ren Cao Han-Fu Chen 《Automatic Control, IEEE Transactions on》1997,42(10):1382-1393
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