全文获取类型
收费全文 | 21828篇 |
免费 | 2465篇 |
国内免费 | 1198篇 |
专业分类
电工技术 | 3910篇 |
综合类 | 1772篇 |
化学工业 | 2761篇 |
金属工艺 | 2377篇 |
机械仪表 | 1706篇 |
建筑科学 | 302篇 |
矿业工程 | 1825篇 |
能源动力 | 366篇 |
轻工业 | 901篇 |
水利工程 | 90篇 |
石油天然气 | 781篇 |
武器工业 | 263篇 |
无线电 | 1706篇 |
一般工业技术 | 3852篇 |
冶金工业 | 1350篇 |
原子能技术 | 399篇 |
自动化技术 | 1130篇 |
出版年
2024年 | 73篇 |
2023年 | 430篇 |
2022年 | 601篇 |
2021年 | 815篇 |
2020年 | 736篇 |
2019年 | 658篇 |
2018年 | 676篇 |
2017年 | 877篇 |
2016年 | 948篇 |
2015年 | 970篇 |
2014年 | 1201篇 |
2013年 | 1317篇 |
2012年 | 1468篇 |
2011年 | 1619篇 |
2010年 | 1105篇 |
2009年 | 1236篇 |
2008年 | 1105篇 |
2007年 | 1409篇 |
2006年 | 1289篇 |
2005年 | 1127篇 |
2004年 | 905篇 |
2003年 | 857篇 |
2002年 | 638篇 |
2001年 | 518篇 |
2000年 | 501篇 |
1999年 | 395篇 |
1998年 | 339篇 |
1997年 | 328篇 |
1996年 | 255篇 |
1995年 | 200篇 |
1994年 | 195篇 |
1993年 | 146篇 |
1992年 | 108篇 |
1991年 | 74篇 |
1990年 | 60篇 |
1989年 | 76篇 |
1988年 | 40篇 |
1987年 | 30篇 |
1986年 | 24篇 |
1985年 | 24篇 |
1984年 | 33篇 |
1983年 | 24篇 |
1982年 | 36篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1959年 | 2篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
This paper presents a highly stable steady-state torque control system with a feedback of a secondary current signal. The torque control system is constructed with a feedback of the secondary current (I2) signal using a quick response magnetic-field sensor constructed with an amorphous core multivibrator bridge, which can solve the secondary resistance change problem for temperature variation in the IM. Moreover, we added a state feedback to the system to improve the response speed for the unit step function of a torque order. The I2 sensor method has advantages especially at a low-speed range, in which conventional method using an integrator shows control errors. 相似文献
102.
The magnetic properties of polyethersulfone-matrix composites with 3-19 vol.% polycrystalline nickel filaments (0.4 (im diam)
were investigated. These filaments were found to exhibit hysteresis energy loss 10800 J/m3 of nickel and coercive force 16.9 kA/m, compared to corresponding values of 4930 J/m3 and 4.7 kA/m for 2 μ.m diam polycrystalline nickel fibers, 1020 J/m3 and 0.5 kA/m for 20 μm diam polycrystalline nickel fibers, and 1280 J/m3 and 2.3 kA/m for solid polycrystalline nickel. 相似文献
103.
薄膜磁头磁轭制备工艺研究 总被引:1,自引:1,他引:0
本文重点讨论了用不同的工艺方法来制备薄膜磁头中的关键元件-磁轭。采用多次光刻的方法克服湿法工艺中磁性膜NiFe层的侧向钻蚀问题,从而实现对磁轭几何尺寸的精确控制,并对几种工艺方法的优缺点作了比较详细的分析。 相似文献
104.
Bruce C. Bunker R. James Kirkpatrick Richard K. Brow Gary L. Turner Carolyn Nelson 《Journal of the American Ceramic Society》1991,74(6):1430-1438
105.
106.
107.
108.
Nuclear magnetic resonance (n.m.r.) studies of 19F nuclei in a random copolymer of vinylidene fluoride and trifluoroethylene were performed at 9.14 MHz and 20.0 MHz. The free induction decays (FIDs) were analysed in terms of two T2 components attributed to the amorphous and crystalline portions of the polymer. The changes in crystallinity as well as the effects of the ferroelectric transition were observed during cycles of heating and cooling between 20°C and 140°C. The crystalline component of the FID lengthens by a factor of 2 at 100°C on heating and decreases by this factor at 60°C on cooling, thus exhibiting the thermal hysteresis of this ferroelectric transition. The spin-lattice relaxation was also investigated. From measurements at 9.14 MHz the observed longitudinal relaxation time T1 appears to be dominated by the dynamics of the amorphous phase and exhibits no anomaly through the phase transition. However, from measurements at 20 MHz, well defined minima of T1 were observed, which are associated with the ferroelectric transition (especially after repeated annealing of the samples). Results are discussed in terms of the crystalline phase structure, which appears dynamically disordered above the ferroelectric phase transition. An analogy is considered with the plastic phase transitions encountered in molecular crystals. 相似文献
109.
110.
Criterion of Magnetic Saturation and Simulation of Nonlinear Magnetization for a Linear Multi-core Pulse Transformer 总被引:1,自引:0,他引:1
The linear multi-core pulse transformer is an important primary driving source used in pulsed power apparatus for the production of dense plasma owing to its compact,relatively low-cost and easy-to-handle characteristics.The evaluation of the magnetic saturation of the transformer cores is essential to the transformer design,because the energy transfer efficiency of the transformer will degrade significantly after magnetic saturation.This work propses analytical formulas of the criterion of magnetic saturation for the cores when the transformer driver practical loads.Furthermore,an electric circuit model based on a dependent source treatment for simulating the electric behavior of the cores related to their nonlinear magnetization is developed using the initial magnetization curve of the cores.The numerical simulation with the model is used to evaluate the validity of the criterion.Both the criterion and the model are found to be in agreement with the experimental data. 相似文献