全文获取类型
收费全文 | 3248篇 |
免费 | 181篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 44篇 |
综合类 | 1篇 |
化学工业 | 940篇 |
金属工艺 | 72篇 |
机械仪表 | 114篇 |
建筑科学 | 119篇 |
矿业工程 | 6篇 |
能源动力 | 127篇 |
轻工业 | 486篇 |
水利工程 | 28篇 |
石油天然气 | 28篇 |
无线电 | 173篇 |
一般工业技术 | 464篇 |
冶金工业 | 193篇 |
原子能技术 | 17篇 |
自动化技术 | 620篇 |
出版年
2024年 | 4篇 |
2023年 | 37篇 |
2022年 | 119篇 |
2021年 | 168篇 |
2020年 | 120篇 |
2019年 | 155篇 |
2018年 | 141篇 |
2017年 | 141篇 |
2016年 | 151篇 |
2015年 | 124篇 |
2014年 | 149篇 |
2013年 | 281篇 |
2012年 | 219篇 |
2011年 | 260篇 |
2010年 | 167篇 |
2009年 | 144篇 |
2008年 | 150篇 |
2007年 | 136篇 |
2006年 | 98篇 |
2005年 | 81篇 |
2004年 | 74篇 |
2003年 | 54篇 |
2002年 | 53篇 |
2001年 | 42篇 |
2000年 | 21篇 |
1999年 | 32篇 |
1998年 | 53篇 |
1997年 | 42篇 |
1996年 | 34篇 |
1995年 | 21篇 |
1994年 | 17篇 |
1993年 | 22篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 4篇 |
1989年 | 14篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1976年 | 6篇 |
1975年 | 2篇 |
1957年 | 1篇 |
1949年 | 1篇 |
排序方式: 共有3432条查询结果,搜索用时 0 毫秒
21.
Gabriel N. Gatica Ricardo Oyarzúa Francisco-Javier Sayas 《Computer Methods in Applied Mechanics and Engineering》2011,200(21-22):1877-1891
In this paper we develop an a posteriori error analysis of a new fully mixed finite element method for the coupling of fluid flow with porous media flow in 2D. Flows are governed by the Stokes and Darcy equations, respectively, and the corresponding transmission conditions are given by mass conservation, balance of normal forces, and the Beavers–Joseph–Saffman law. We consider dual-mixed formulations in both media, which yields the pseudostress and the velocity in the fluid, together with the velocity and the pressure in the porous medium, and the traces of the porous media pressure and the fluid velocity on the interface, as the resulting unknowns. The set of feasible finite element subspaces includes Raviart–Thomas elements of lowest order and piecewise constants for the velocities and pressures, respectively, in both domains, together with continuous piecewise linear elements for the traces. We derive a reliable and efficient residual-based a posteriori error estimator for the coupled problem. The proof of reliability makes use of the global inf–sup condition, Helmholtz decompositions in both media, and local approximation properties of the Clément interpolant and Raviart–Thomas operator. On the other hand, inverse inequalities, the localization technique based on element-bubble and edge-bubble functions, and known results from previous works, are the main tools for proving the efficiency of the estimator. Finally, some numerical results confirming the theoretical properties of this estimator, and illustrating the capability of the corresponding adaptive algorithm to localize the singularities of the solution, are reported. 相似文献
22.
Ricardo A. Aroca C. Andre T. Salama 《Analog Integrated Circuits and Signal Processing》2006,48(3):167-174
This paper presents the design and implementation of a new wide dynamic range parallel feedback (PF) transimpedance amplifier
(TIA) for 10 Gb/s optical links. The wide dynamic range is attributed to the novel TIA architecture employing both shunt-shunt
and shunt-series feedback networks. The outstanding features of the TIA are wide dynamic range, high gain, low power consumption
and design simplicity. A prototype implemented in a 0.5 μm SiGe BiCMOS technology and operating at −3.3 V power supply features
an 18.4 dBm dynamic range with a BER less than 10−12, an optical sensitivity of −16 dBm, optical overload of +2.4 dBm, a bandwidth of 8.27 GHz, a gain of 950 Ω and a power consumption
of 189 mW. The new parallel feedback architecture offers improved overload and noise performance when compared to previously
reported, state of the art, single feedback TIA designs and meets all the 10 Gigabit Ethernet and short-reach OC-192 SONET
specifications.
Ricardo Andres Aroca received the B.S. (Hons) degree in electrical engineering from the University of Windsor, Canada, and the M.S. degree from
the University of Toronto, Canada, in 2001 and 2004, respectively. In 2000 he spent two 4 month internships with Nortel Networks
in the Microelectronics Department. Mr. Aroca received the Natural Sciences and Engineering Research Counsel of Canada (NSERC)
Postgraduate Scholarship award in 2002. He is currently working toward the Ph.D. degree at the University of Toronto where
his research interests lie in the area of high-frequency integrated circuits for wireless and wireline communication systems.
C. Andre T. Salama received the B.A.Sc. (Hons.) M.A.Sc. and Ph. D. degrees, all in Electrical Engineering, from the University of British Columbia
in 1961, 1962 and 1966 respectively. From 1962 to 1963 he served as a Research Assistant at the University of California,
Berkeley. From 1966 to 1967 he was employed at Bell Northern Research, Ottawa, as a Member of Scientific Staff working in
the area of integrated circuit design. Since 1967 he has been on the staff of the Department of Electrical and Computer Engineering,
University of Toronto where he held the J.M. Ham Chair in Microelectronics from 1987 to 1997. In 1992, he was appointed to
his present position of University Professor for scholarly achievements and preeminence in the field of microelectronics.
In 1989-90, he was awarded the ITAC/NSERC Research Fellowship in information technology. In 1994, he was awarded the Canada
Council I.W. Killam Memorial Prize in Engineering for outstanding career contributions to the field of microelectronics. In
2000, he received the IEEE Millenium Medal. In 2003, he received the Outstanding Lifetime Achievement Award from the Canadian
Semiconductor Technology Conference for seminal and outstanding contributions to semiconductor device research and promotion
of Canadian University research in microelectronics. In 2004, he received the NSERC Lifetime Achievement Award of Research
Excellence for outstanding and sustained contributions to the field of microelectronics and the Networks of Centres of Excellence
(NCE) Recognition Award for research excellence and outstanding leadership.He was associate editor of the IEEE Transactions
on Circuits and Systems in 1986–88 and a member of the International Electron Devices Meeting (IEDM) Technical Program Committeein
1980–82, 1987–89 and 1996–98. He was the chair of the Solid State Devices Subcommittee for IEDM in 1998 and was a member of
the editorial board of Solid State Electronics from 1984 to 2002. He is presently a member of the editorial board of the Analog
IC and Signal Processing Journal and the Technical Program Committee of the International Symposium on Power Semiconductor
Devices and ICs (ISPSD) and the Technical ProgramCommittee of the International Symposium on Low Power Electronics and Design
(ISLPED). He chaired the technical program committee of ISPSD in 1996 and was the general chair for the conference in 1999.Dr.
Salama is the Scientific Director of Micronet, a network of centres of excellence focussing on microelectronics research and
funded by the Canadian Government and Industry. He has published extensively in technical journals, is the holder of eleven
patents and has served as a consultant to the semiconductor industry in Canada and the U.S. His research interests include
the design and fabrication of semiconductor devices and integrated circuits with emphasis on deep submicron devices as well
as circuits and systems for high speed, low power signal processing applications. Dr. Salama is a Fellow of the Institute
of Electrical and Electronics Engineers, a Fellow of the Royal Society of Canada, a Fellow of the Canadian Academy of Engineering,
a member of the Association of Professional Engineers of Ontario, the Electrochemical Society and the Innovation Management
Association of Canada. 相似文献
23.
Energy management system (EMS) computer architectures have changed significantly over the recent past increasing the difficulty and the need for a priori assessment of system performance and dependability. The old practice based on measurements is no longer acceptable because of the flexibility accrued with the deployment of the new distributed computer-based systems. The number of “what if” questions increased since EMS systems are now implemented using multiple workstations that can be interconnected in various different ways.In this paper we show how alternative configurations can be modeled and analyzed, before proposing and purchasing any equipment, with the assistance of Markov reward models. We review the concept of Markov reward models and show how they can be applied in the availability analysis of SCADA/EMS computer systems. The paper also presents a software tool that facilitates automatic generation and solution of large Markov reward models. The input language of this modeling tool uses a variation of stochastic Petri nets called stochastic reward nets, which are also reviewed. We believe this is the first time a detailed quantitative model of a SCADA/EMS computer system is proposed and solved in the general literature. 相似文献
24.
Ecotaxes allow the internalization of costs that are considered externalities associated with polluting industrial process emissions to the atmosphere. In this paper, ecotaxes internalize polluting emissions negative impacts that are added to electricity and steam generated costs of a steam turbine and heat recovery systems from a utilities refinery plant. Steam costs were calculated by means of an exergy analysis tool and Aspen Plus simulation models. Ecotaxes were calculated for specific substances emitted in the refinery flue gases, based on a toxicity and pollution scale. Ecotaxes were generated from a model that includes damages produced to biotic and abiotic resources and considers the relative position of those substances in a toxicity and pollution scale. These ecotaxes were internalized by an exergoeconomic analysis resulting in an increase in the cost per kWh produced. This kind of ecotax is not applied in Mexico. The values of ecotaxes used in the cost determination are referred to the values currently applied by some European countries to nitrogen oxides emissions. 相似文献
25.
26.
SPETA: Social pervasive e-Tourism advisor 总被引:1,自引:0,他引:1
Angel García-Crespo Javier Chamizo Ismael Rivera Myriam Mencke Ricardo Colomo-Palacios Juan Miguel Gómez-Berbís 《Telematics and Informatics》2009
Tourism is one of the major sources of income for many countries. Therefore, providing efficient, real-time service for tourists is a crucial competitive asset which needs to be enhanced using major technological advances. The current research has the objective of integrating technological innovation into an information system, in order to build a better user experience for the tourist. The principal strength of the approach is the fusion of context-aware pervasive systems, GIS systems, social networks and semantics. This paper presents the SPETA system, which uses knowledge of the user’s current location, preferences, as well as a history of past locations, in order to provide the type of recommender services that tourists expect from a real tour guide. 相似文献
27.
28.
29.
Intrinsic selectivities and yields in the catalytic hydrogenation of polyenoic fatty acid methyl esters 总被引:1,自引:0,他引:1
Ricardo J. Grau Alberto E. Cassano Miguel A. Balfanás 《Journal of the American Oil Chemists' Society》1990,67(4):226-232
Precise values of the intrinsic selectivities and yields for the hydrogenation products of methyl linolenate (Ln) and methyl
linoleate (L) obtained under carefully controlled conditions using a commercial Ni catalyst are presented and analyzed in
detail. The existence of a preferential adsorption of Ln and a significant co-hydrogenation of its double bonds are confirmed
as being the dominant features under typical vegetable oil processing conditions.
It is shown that the values of the selectivities that are obtained from the classical consecutive reactions network account
for the intrinsic selectivity of the catalyst only while hydrogenating feedstocks with moderate to low (<10%) contents of
Ln.
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Lltoral (U.N.L.) 相似文献
30.
Garrocho Charles T. B. da Silva Maurício J. Oliveira Ricardo A. R. 《Wireless Networks》2020,26(1):373-386
Wireless Networks - D2D (device-to-device) communication is one of the developments of 5G networks (5th generation mobile networks) that reduce mobile traffic load, reduce energy consumption and... 相似文献