全文获取类型
收费全文 | 94647篇 |
免费 | 9234篇 |
国内免费 | 5199篇 |
学科分类
工业技术 | 109080篇 |
出版年
2024年 | 527篇 |
2023年 | 1786篇 |
2022年 | 3434篇 |
2021年 | 4499篇 |
2020年 | 3496篇 |
2019年 | 2619篇 |
2018年 | 3026篇 |
2017年 | 3348篇 |
2016年 | 2968篇 |
2015年 | 4134篇 |
2014年 | 5386篇 |
2013年 | 6281篇 |
2012年 | 7109篇 |
2011年 | 7255篇 |
2010年 | 6748篇 |
2009年 | 6301篇 |
2008年 | 6065篇 |
2007年 | 5892篇 |
2006年 | 5352篇 |
2005年 | 4355篇 |
2004年 | 3023篇 |
2003年 | 2352篇 |
2002年 | 2153篇 |
2001年 | 1757篇 |
2000年 | 1701篇 |
1999年 | 1559篇 |
1998年 | 1084篇 |
1997年 | 983篇 |
1996年 | 883篇 |
1995年 | 716篇 |
1994年 | 543篇 |
1993年 | 412篇 |
1992年 | 303篇 |
1991年 | 243篇 |
1990年 | 167篇 |
1989年 | 162篇 |
1988年 | 126篇 |
1987年 | 70篇 |
1986年 | 68篇 |
1985年 | 31篇 |
1984年 | 40篇 |
1983年 | 21篇 |
1982年 | 23篇 |
1981年 | 23篇 |
1980年 | 26篇 |
1979年 | 9篇 |
1977年 | 2篇 |
1966年 | 1篇 |
1959年 | 8篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
A photochromic nanocomposite based on Keggin structure phosphomolybdic acid (PMoA) well dispersed in polyethyleneglycol (PEG) was fabricated. TEM image showed that PMoA nanoparticles with narrow size distribution were finely dispersed in polymer matrix. FT-IR results showed that the Keggin geometry of polyoxometalates was still preserved inside the composites and strong coulombic interaction was built between PMoA and polymer matrix. Under UV irradiation, the film was reduced photochemically to yield a blue species, which was in accordance with a charge-transfer mechanism. 相似文献
32.
33.
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
34.
目前的电路仿真软件通常是在电路中所有元件值都是给定的情况下得到一些数值结果,而非解析结果。该文利用Matlab的符号运算功能编程,通过节点列表法,实现了任意线性电路的自动解析求解,为电路分析提供了一个有效的辅助工具。 相似文献
35.
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
36.
37.
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
38.
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
39.
40.