全文获取类型
收费全文 | 349521篇 |
免费 | 3055篇 |
国内免费 | 417篇 |
专业分类
电工技术 | 5611篇 |
综合类 | 192篇 |
化学工业 | 55146篇 |
金属工艺 | 19801篇 |
机械仪表 | 12918篇 |
建筑科学 | 6373篇 |
矿业工程 | 4486篇 |
能源动力 | 6171篇 |
轻工业 | 17148篇 |
水利工程 | 5684篇 |
石油天然气 | 16551篇 |
武器工业 | 31篇 |
无线电 | 30192篇 |
一般工业技术 | 83514篇 |
冶金工业 | 51390篇 |
原子能技术 | 13617篇 |
自动化技术 | 24168篇 |
出版年
2021年 | 3513篇 |
2019年 | 3466篇 |
2018年 | 6759篇 |
2017年 | 6983篇 |
2016年 | 7450篇 |
2015年 | 3885篇 |
2014年 | 6831篇 |
2013年 | 14286篇 |
2012年 | 9743篇 |
2011年 | 12189篇 |
2010年 | 9952篇 |
2009年 | 11033篇 |
2008年 | 11170篇 |
2007年 | 10846篇 |
2006年 | 9047篇 |
2005年 | 8050篇 |
2004年 | 7826篇 |
2003年 | 7601篇 |
2002年 | 7397篇 |
2001年 | 7276篇 |
2000年 | 7093篇 |
1999年 | 6557篇 |
1998年 | 13027篇 |
1997年 | 9985篇 |
1996年 | 7465篇 |
1995年 | 5910篇 |
1994年 | 5393篇 |
1993年 | 5592篇 |
1992年 | 4642篇 |
1991年 | 4735篇 |
1990年 | 4861篇 |
1989年 | 4672篇 |
1988年 | 4560篇 |
1987年 | 4433篇 |
1986年 | 4362篇 |
1985年 | 4563篇 |
1984年 | 4404篇 |
1983年 | 4292篇 |
1982年 | 4019篇 |
1981年 | 4210篇 |
1980年 | 4141篇 |
1979年 | 4393篇 |
1978年 | 4716篇 |
1977年 | 4778篇 |
1976年 | 5732篇 |
1975年 | 4330篇 |
1974年 | 4372篇 |
1973年 | 4445篇 |
1972年 | 4050篇 |
1971年 | 3673篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Xin Sun Qiang Lu Moroz V. Takeuchi H. Gebara G. Wetzel J. Shuji Ikeda Changhwan Shin Tsu-Jae King Liu 《Electron Device Letters, IEEE》2008,29(5):491-493
A tri-gate bulk MOSFET design utilizing a low-aspect-ratio channel is proposed to provide an evolutionary pathway for CMOS scaling to the end of the roadmap. 3-D device simulations indicate that this design offers the advantages of a multi-gate FET (reduced variability in performance and improved scalability) together with the advantages of a conventional planar MOSFET (low substrate cost and capability for dynamic threshold-voltage control). 相似文献
992.
We identify the time dependence of temperature of a surface of a long hollow thermosensitive cylinder and its thermal and
thermal stressed states according to the known temperature and strains on the other surface. The posed problem is reduced
to the inverse problem of thermoelasticity. By using the solution of the direct problem of thermoelasticity, we perform the
numerical verification of the proposed procedure of solution of the inverse problem.
__________
Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 43, No. 6, pp. 55–61, November–December, 2007. 相似文献
993.
V. F. Ivanov A. A. Nekrasov K. V. Tcheberiako A. V. Vannikov A. S. Posed'ko S. I. Lishik Yu. V. Trofimov 《Journal of the Society for Information Display》2003,11(1):11-14
Abstract— An all solid‐state photoelectrochromic element (PECE) was developed on the basis of electrochromic layers of WO3 and polyaniline with a layer of polymer electrolyte placed on a base of polyamidosulfoacid, in which a thin‐film CdSxSe1?x photoresistor was used as an electronic key. The dependence of the sensitometric characteristics of the PECE on the applied voltage was studied. 相似文献
994.
A multi-agent architecture for dynamic scheduling of steel hot rolling 总被引:13,自引:0,他引:13
Peter I. Cowling Djamila Ouelhadj Sanja Petrovic 《Journal of Intelligent Manufacturing》2003,14(5):457-470
Steel production is a complex process and finding coherent and effective schedules for the wide variety of production steps, in a dynamic environment, is a challenging task. In this paper, we propose a multi-agent architecture for integrated dynamic scheduling of the hot strip mill (HSM) and the continuous caster. The scheduling systems of these processes have very different objectives and constraints, and operate in an environment where there is a substantial quantity of real-time information concerning production failures and customer requests. Each process is assigned to an agent which independently, seeks an optimal dynamic schedule at a local level taking into account local objectives, real-time information and information received from other agents. Each agent can react to real-time events in order to fix any problems that occur. We focus here, particularly, on the HSM agent which uses a tabu search heuristic to create good predictive–reactive schedules quickly. The other agents simulate the production of the coil orders and the real-time events, which occur during the scheduling process. When real-time events occur on the HSM, the HSM agent might decide whether to repair the current schedule or reschedule from scratch. To address this problem, a range of schedule repair and complete rescheduling strategies are investigated and their performance is assessed with respect to measures of utility, stability and robustness, using an experimental simulation framework. 相似文献
995.
996.
Viktor G. Khizhnyak Vitalii I. Korol' Alexei D. Kostenko 《Powder Metallurgy and Metal Ceramics》2003,42(11-12):644-648
Wear resistance measurements have been made with U8A steel bearing protective coatings based on the carbides of titanium, vanadium, and chromium or iron borides, for various forms of wear. The carbide and boride coatings raise the wear resistance considerably (by factors of 6-30 in accordance with the type of wear). Measurements have been made on the microhardness, microbrittleness, and adhesion of the coating to the substrate, which are effective characteristics that quite fully reflect the effects of the microhardness and state of stress, structure, and defectiveness on the wear resistance. 相似文献
997.
Ya. A. Ilyushin V. E. Kunitsyn 《Journal of Communications Technology and Electronics》2008,53(5):545-549
The possibility for determining the structure of the surface layer of a cometary nucleus from the data of bistatic radar sensing is investigated. A rigorous solution formulated for this problem on the basis of vector equations of the electromagnetic field is presented. 相似文献
998.
Porous carbon nanofibers are synthesized by CVD method from acetylene with use of iron-containing catalysts. Activation of the nanofibers in melted potassium hydroxide results in increasing surface area from initial 300–400 m2 g−1 to 1700 m2 g−1. As follows from XRD data, activated nanofibers do not contain regular packages of graphene layers, but retain high electric conductivity. Deposition of copper improves electrochemical hydrogen storing characteristics of carbon nanofibers. Carbon nanomaterials obtained can be used as hydrogen storing materials in batteries instead of hydride forming metals. 相似文献
999.
A membrane reactor containing different types of ZSM-5/porous SS membranes was used to perform the xylene isomerization reaction. The parent Na-ZSM-5 layer was synthesized by secondary growth on top of porous stainless steel tubes. The xylene isomerization reaction was carried out at different temperatures in the membrane reactor and in a fixed-bed reactor of identical geometry for comparison. Two different kinds of membranes were prepared by ion exchange: a Pt/H-ZSM-5 catalytic membrane and two Ba-ZSM-5 composites with different Ba2+ concentration. The p-xylene production using 100% exchanged Ba-membrane was about 28% higher than the fixed-bed reactor at 370 °C, when m-xylene was fed. 相似文献
1000.
V. Morandi F. Marabelli V. Amendola M. Meneghetti D. Comoretto 《Advanced functional materials》2007,17(15):2779-2786
Polystyrene artificial opals with few gold nanoparticles (AuNp) embedded in the interstices (doping) are grown by using the meniscus technique starting from a mixed suspension of microspheres and AuNp. Samples having different sphere diameters and nanoparticle loads have been prepared. Their reflectance spectra clearly show a dramatic bathochromic shift of the photonic stop band (up to 1400 cm–1) and a reduction of its full width half maximum, due to an increase of the effective refractive index of about 8 % with respect to bare opals, which is accounted for by analytical theoretical models. Reflectance spectra do not show any direct evidence of AuNp absorption even at the higher AuNp doping level. Nanosecond transient absorption measurements on these systems indicate that a variation of transmission (optical switching) of about 150 % is observed for AuNp doped opals upon photoexcitation with 9 ns laser pulses at 532 nm. No switching is instead observed for bare opals. 相似文献