全文获取类型
收费全文 | 525107篇 |
免费 | 8054篇 |
国内免费 | 1466篇 |
专业分类
电工技术 | 9565篇 |
综合类 | 526篇 |
化学工业 | 78744篇 |
金属工艺 | 19964篇 |
机械仪表 | 15203篇 |
建筑科学 | 12689篇 |
矿业工程 | 2270篇 |
能源动力 | 14525篇 |
轻工业 | 47087篇 |
水利工程 | 5219篇 |
石油天然气 | 9334篇 |
武器工业 | 37篇 |
无线电 | 60008篇 |
一般工业技术 | 101857篇 |
冶金工业 | 103795篇 |
原子能技术 | 10573篇 |
自动化技术 | 43231篇 |
出版年
2022年 | 3163篇 |
2021年 | 4901篇 |
2020年 | 3482篇 |
2019年 | 4561篇 |
2018年 | 7814篇 |
2017年 | 7619篇 |
2016年 | 7943篇 |
2015年 | 5563篇 |
2014年 | 9248篇 |
2013年 | 24086篇 |
2012年 | 14646篇 |
2011年 | 20167篇 |
2010年 | 15817篇 |
2009年 | 17712篇 |
2008年 | 18105篇 |
2007年 | 17794篇 |
2006年 | 15518篇 |
2005年 | 14227篇 |
2004年 | 13609篇 |
2003年 | 13411篇 |
2002年 | 12645篇 |
2001年 | 12840篇 |
2000年 | 11878篇 |
1999年 | 12617篇 |
1998年 | 32890篇 |
1997年 | 22947篇 |
1996年 | 17475篇 |
1995年 | 13062篇 |
1994年 | 11304篇 |
1993年 | 10999篇 |
1992年 | 7923篇 |
1991年 | 7426篇 |
1990年 | 7272篇 |
1989年 | 7026篇 |
1988年 | 6472篇 |
1987年 | 5775篇 |
1986年 | 5658篇 |
1985年 | 6279篇 |
1984年 | 5905篇 |
1983年 | 5176篇 |
1982年 | 4902篇 |
1981年 | 4974篇 |
1980年 | 4716篇 |
1979年 | 4615篇 |
1978年 | 4413篇 |
1977年 | 5352篇 |
1976年 | 6989篇 |
1975年 | 3803篇 |
1974年 | 3553篇 |
1973年 | 3671篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
891.
High-resolution positive and negative photoresists were used to fabricate ?/4-phase-shifted corrugations by holographic exposure. To avoid mixing these photoresists, cyclised polyisoprene was used as a midlayer. The shape and depth of the corrugations on the positive and negative photoresist regions were almost the same. Single-mode operation at the Bragg wavelength was confirmed in lasers with the corrugation. 相似文献
892.
Nagpal R. Zambonelli F. Sirer E.G. Chaouchi H. Smirnov M. 《Intelligent Systems, IEEE》2006,21(2):50-58
No generally accepted principles and guidelines currently exist to help engineers design local interaction mechanisms that result in a desired global behavior. However, several communities have developed ways of approaching this problem in the context of niched application areas. Because the ideas underlying these approaches are often obscured or underemphasized in technical papers, the authors review the role of self-organization in their work. They provide a better picture of the status of the emerging field of self-organizing systems or autonomic computing. 相似文献
893.
894.
Hayashi M. Tanaka H. Ohara K. Otani T. Suzuki M. 《Lightwave Technology, Journal of》2002,20(2):236-242
An all-optical multiplexing technique using wavelength division multiplexing (WDM)-time division multiplexing (TDM) conversion with an electroabsorption wavelength converter has been proposed and demonstrated. The effectiveness of this WDM-TDM conversion technique for various pulsewidth settings was experimentally investigated. The fluctuation of the signal performance, which was inevitably caused by the coherent crosstalk between adjacent pulses in the conventional optical time division multiplexing (OTDM) technique, were successfully suppressed, even in the case of wide pulse duration. High Q-factor performance has been maintained for a wide range of duty ration from 36% to 74%. By introducing this technique to the optical time division multiplexer, a highly stable and high-quality 40-Gb/s optical signal can be effectively produced without generating the short pulse or setting two tributaries at orthogonal polarization states, and without introducing high-speed electronics for signal multiplexing. The WDM-TDM conversion with an electroabsorption wavelength converter was extended to 60-Gb/s operation by using three 20-Gb/s tributaries. A clear eye opening was confirmed for a waveform after the WDM-TDM conversion of the 60-Gb/s signal 相似文献
895.
Design and Implementation of a Flexible Manufacturing Control System Using Neural Network 总被引:1,自引:0,他引:1
Magdy M. Abdelhameed Farid A. Tolbah 《International Journal of Flexible Manufacturing Systems》2002,14(3):263-279
Design and implementation of a sequential controller based on the concept of artificial neural networks for a flexible manufacturing system are presented. The recurrent neural network (RNN) type is used for such a purpose. Contrary to the programmable controller, an RNN-based sequential controller is based on a definite mathematical model rather than depending on experience and trial and error techniques. The proposed controller is also more flexible because it is not limited by the restrictions of the finite state automata theory. Adequate guidelines of how to construct an RNN-based sequential controller are presented. These guidelines are applied to different case studies. The proposed controller is tested by simulations and real-time experiments. These tests prove the successfulness of the proposed controller performances. Theoretical as well as experimental results are presented and discussed indicating that the proposed design procedure using Elman's RNN can be effective in designing a sequential controller for event-based type manufacturing systems. In addition, the simulation results assure the effectiveness of the proposed controller to outperform the effect of noisy inputs. 相似文献
896.
By using mathematical formulae developed in previous studies, certain pollution parameters of dye effluent obtained from reactive dyeing with a single dye can be predicted with good accuracy. In this study, the degree of pollution of reactive dyeing effluent using dye mixtures was also predicted by other approaches, such as linear and non-linear regression. The prediction accuracy was found to be satisfactory. 相似文献
897.
Letters to the editor 总被引:1,自引:0,他引:1
898.
M. Liess R. Hua K. Elsenaar 《The International Journal of Advanced Manufacturing Technology》2002,20(1):58-62
Cables to moving parts on a linear actuator in production machines, such as pick-and-place machines, are a source of unreliability
owing to the possible breaking of a cable. They further reduce the positioning precision of the actuator owing to additional
forces. Slotted waveguide systems for rail vehicles based on 2.4 GHz transmission frequency are well known, but transmitters/receivers
and waveguides are bulky. The paper reports on the reduction in size of the equipment, adapted to 5.8 GHz using a commercial
off-the-shelf RadioLan communication module. Further, the efficient termination of the wave-guide and a new way to reduce
standing-wave effects is also discussed. 相似文献
899.
We present uniaxial tensile test results for 30–50 nm thick freestanding aluminum films. Young’s modulus and ductility were found to decrease monotonically with grain size. Reverse Hall–Petch behavior was observed with no appreciable room temperature creep. Non-linear elasticity with small irreversible deformation was observed for 50 nm thick specimens. 相似文献
900.
Mass transport in pulsating flow devices using either moving boundaries or oscillating imposed pressure drops are compared with each other by means of a calculation using a simple model. We conclude that there is no difference between the two configurations as long as one is interested only in the power required to move the fluid for the convective mass transport achieved. However, the boundary driven configuration is more efficient if the power is divided by the total mass transport where both the diffusive and convective parts are taken into account, the boundary driven configuration is more efficient. The amplitude of the piston stroke in the pressure driven configuration and the amplitude in the boundary driven case are assumed to be the same, and the inertia of the moving devices themselves are ignored in this calculation. 相似文献