全文获取类型
收费全文 | 259822篇 |
免费 | 12919篇 |
国内免费 | 6817篇 |
专业分类
电工技术 | 10666篇 |
技术理论 | 9篇 |
综合类 | 8845篇 |
化学工业 | 38554篇 |
金属工艺 | 18689篇 |
机械仪表 | 16011篇 |
建筑科学 | 11576篇 |
矿业工程 | 4701篇 |
能源动力 | 5129篇 |
轻工业 | 11635篇 |
水利工程 | 4334篇 |
石油天然气 | 11091篇 |
武器工业 | 1056篇 |
无线电 | 26756篇 |
一般工业技术 | 51846篇 |
冶金工业 | 20234篇 |
原子能技术 | 6028篇 |
自动化技术 | 32398篇 |
出版年
2024年 | 716篇 |
2023年 | 2363篇 |
2022年 | 4714篇 |
2021年 | 6362篇 |
2020年 | 4794篇 |
2019年 | 4240篇 |
2018年 | 13622篇 |
2017年 | 14622篇 |
2016年 | 10198篇 |
2015年 | 6492篇 |
2014年 | 7915篇 |
2013年 | 10408篇 |
2012年 | 12936篇 |
2011年 | 19513篇 |
2010年 | 17466篇 |
2009年 | 16214篇 |
2008年 | 16032篇 |
2007年 | 17484篇 |
2006年 | 8436篇 |
2005年 | 10691篇 |
2004年 | 7579篇 |
2003年 | 7127篇 |
2002年 | 6156篇 |
2001年 | 5099篇 |
2000年 | 4561篇 |
1999年 | 4043篇 |
1998年 | 4058篇 |
1997年 | 3221篇 |
1996年 | 2872篇 |
1995年 | 2285篇 |
1994年 | 1936篇 |
1993年 | 1630篇 |
1992年 | 1464篇 |
1991年 | 1341篇 |
1990年 | 1241篇 |
1989年 | 1169篇 |
1988年 | 1019篇 |
1987年 | 924篇 |
1986年 | 814篇 |
1985年 | 771篇 |
1984年 | 735篇 |
1981年 | 691篇 |
1979年 | 744篇 |
1978年 | 785篇 |
1977年 | 747篇 |
1976年 | 774篇 |
1975年 | 724篇 |
1974年 | 726篇 |
1973年 | 733篇 |
1972年 | 709篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Power-handling capability for RF filters 总被引:1,自引:0,他引:1
Ming Yu 《Microwave Magazine, IEEE》2007,8(5):88-97
A simplified method for evaluating the power-handling capability inside an RF filter has been introduced based on the general cross-coupled prototype network theory, modern EM modeling techniques, and well-established breakdown threshold analysis. The electrical field strength and voltages evaluated using either the single-cavity resonator (eigen mode) model or simply the prototype model have been presented and compared against the direct EM computation of the complete filter structure. Close agreement has been found between the full EM modeling and the scaling of a single resonator or even prototype network analysis only. This procedure is expected to simplify the multipaction and ionization breakdown analysis of filters and filter-based diplexers and multiplexers. The method presented is general and is applicable to all filter types that can be described in a circuit model. Practical issues such as the multicarrier operation, sharp edge condition, design margin, and prevention techniques are also covered. 相似文献
992.
993.
The electrical properties of structures consisting of a monolayer of 1-octadecene deposited on the Si surface are investigated depending on the method of passivation of the surface prior to the deposition of the film (hydrogen and ion passivation) and the intensity of illumination which activates the addition reaction of molecules of 1-octadecene to the Si atoms. The monolayer of 1-octadecene on the Si surface is stable and provides the chemical passivation of the surface. Two types of traps are found, namely, traps for holes and electrons, whose density can be varied during deposition of the monolayer by the choice of intensity of illumination and by the method of passivation of the surface. In the case of a low level of illumination and/or the use of the iodine passivation of the surface, the electron traps prevail, and, in the case of high intensity of illumination and/or hydrogen passivation of the surface, the hole traps prevail. It is shown that the use of these films provides conductivity in thin near-surface layers of Si due to providing the mode of flat bands or accumulation of carriers near the surface. 相似文献
994.
A method for measuring the characteristics of tunneling and impact ionization in thin-film electroluminescent emitters is suggested. This method makes it possible to find time dependences of the space-charge layer thickness near the anode and the length of the impact ionization region, to determine more exactly the time dependence of the field in the potential barrier at the cathode interface, the maximum depth of the surface states from which electron tunneling occurs, the minimum thickness of the barrier, and the electron tunneling probability, as well as the impact ionization rate for the deep centers related to structural defects of the phosphor layer. 相似文献
995.
I. V. Khomskaya V. I. Zel’dovich N. Yu. Frolova 《Metal Science and Heat Treatment》2007,49(3-4):118-124
The strain behavior and phase transformations in Cu-37 wt.% Zn brass, Cu-12.5 wt.% Al bronze, and copper (99.97%) are studied
under two variants of pulse loading, i.e., converging shock waves and a flux of powder particles accelerated by explosion.
The effects connected with uniform and localized strain caused by the action of shock waves are determined and the disperse
structures formed in the materials under dynamic loading are analyzed.
__________
Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 3, pp. 28–34, March, 2007. 相似文献
996.
997.
998.
In this paper, a novel approach of automated multirobot nanoassembly planning is presented. This approach uses an improved self-organizing map to coordinate assembly tasks of nanorobots while generating optimized motion paths at run time with a modified shunting neural network. It is capable of synchronizing multiple nanorobots working simultaneously and efficiently on the assembly of swarms of objects in the presence of obstacles and environmental uncertainty. Operation of the presented approach is demonstrated with experiments at the end of the paper. 相似文献
999.
Electric-discharge cleaning of surfaces of manufacturing equipment from foreign nonmetallic deposits
T. D. Denisyuk A. R. Rizun Yu. V. Golen’ 《Surface Engineering and Applied Electrochemistry》2007,43(6):453-454
Processing characteristics of the electric-discharge cleaning of surfaces of manufacturing equipment from foreign nonmetallic deposits of different durability are researched. To expand the capabilities of the cleaning of manufacturing equipment, a complex cleaning method is proposed. 相似文献
1000.
Yu Yang Hugo Bender Kai Arstila Bart Swinnen Bert Verlinden Ingrid De Wolf 《Microelectronics Reliability》2008,48(8-9):1517-1520
Focused ion beam (FIB) and nano-probing were applied for failure analysis of three-dimensional stacked circuits with copper through-silicon-vias between the stacked chips. The failure analysis was done after high temperature storage and thermal cycling tests. Passive voltage contrast in FIB allowed to pinpoint the open sites. FIB cross-sections showed the presence of opens at the bottom of the copper vias. The failure cause was suspected to be an interlayer particle, which was confirmed by optical profilometry. Nano-probing was used on another sample to pinpoint the failure location through the measurement of the local resistance within the daisy chains. The failure was traced out to be related with surface contamination. 相似文献