全文获取类型
收费全文 | 7091篇 |
免费 | 622篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 59篇 |
综合类 | 5篇 |
化学工业 | 1903篇 |
金属工艺 | 79篇 |
机械仪表 | 208篇 |
建筑科学 | 276篇 |
矿业工程 | 15篇 |
能源动力 | 151篇 |
轻工业 | 1490篇 |
水利工程 | 72篇 |
石油天然气 | 16篇 |
无线电 | 454篇 |
一般工业技术 | 1170篇 |
冶金工业 | 320篇 |
原子能技术 | 16篇 |
自动化技术 | 1484篇 |
出版年
2024年 | 27篇 |
2023年 | 87篇 |
2022年 | 112篇 |
2021年 | 284篇 |
2020年 | 233篇 |
2019年 | 229篇 |
2018年 | 369篇 |
2017年 | 373篇 |
2016年 | 429篇 |
2015年 | 308篇 |
2014年 | 398篇 |
2013年 | 729篇 |
2012年 | 664篇 |
2011年 | 596篇 |
2010年 | 390篇 |
2009年 | 381篇 |
2008年 | 355篇 |
2007年 | 350篇 |
2006年 | 248篇 |
2005年 | 184篇 |
2004年 | 170篇 |
2003年 | 142篇 |
2002年 | 136篇 |
2001年 | 68篇 |
2000年 | 51篇 |
1999年 | 39篇 |
1998年 | 43篇 |
1997年 | 43篇 |
1996年 | 28篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 27篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 7篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 11篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1976年 | 4篇 |
1908年 | 2篇 |
1905年 | 2篇 |
1899年 | 2篇 |
排序方式: 共有7718条查询结果,搜索用时 15 毫秒
21.
Pablo Cortés Luis Onieva Jesús Muñuzuri José Guadix 《Computers & Industrial Engineering》2013,64(1):403-411
Nowadays is very common the presence of tall buildings in the business centres of the main cities of the world. Such buildings require the installation of numerous lifts that are coordinated and managed under a unique control system. Population working in the buildings follows a similar traffic pattern generating situations of traffic congestion. The problem arises when a passenger makes a hall call wishing to travel to another floor of the building. The dispatching of the most suitable car is the optimization problem we are tackling in this paper. We develop a viral system algorithm which is based on a bio-inspired virus infection analogy to deal with it. The viral system algorithm is compared to genetic algorithms, and tabu search approaches that have proven efficiency in the vertical transportation literature. The experiments undertaken in tall buildings from 10 to 24 floors, and several car configurations from 2 to 6 cars, provide valuable results and show how viral system outperforms such soft computing algorithms. 相似文献
22.
Fermín L. Cruz José A. Troyano Fernando Enríquez F. Javier Ortega Carlos G. Vallejo 《Expert systems with applications》2013,40(8):3174-3184
Nowadays, people do not only navigate the web, but they also contribute contents to the Internet. Among other things, they write their thoughts and opinions in review sites, forums, social networks, blogs and other websites. These opinions constitute a valuable resource for businesses, governments and consumers. In the last years, some researchers have proposed opinion extraction systems, mostly domain-independent ones, to automatically extract structured representations of opinions contained in those texts. In this work, we tackle this task in a domain-oriented approach, defining a set of domain-specific resources which capture valuable knowledge about how people express opinions on a given domain. These resources are automatically induced from a set of annotated documents. Some experiments were carried out on three different domains (user-generated reviews of headphones, hotels and cars), comparing our approach to other state-of-the-art, domain-independent techniques. The results confirm the importance of the domain in order to build accurate opinion extraction systems. Some experiments on the influence of the dataset size and an example of aggregation and visualization of the extracted opinions are also shown. 相似文献
23.
José Luis Ochoa Rafael Valencia-García Alonso Perez-Soltero Mario Barceló-Valenzuela 《Expert systems with applications》2013,40(6):2058-2068
Currently, most of the information available in the Web is adapted primarily for human consumption, but there is so much information that can no longer be processed by a person in a reasonable time, either in digital or physical formats. To solve this problem, the idea of the Semantic Web arose. The Semantic Web deals with adding machine-readable information to Web pages. Ontologies represent a very important element of this web, as they provide a valid and robust structure to represent knowledge based on concepts, relations, axioms, etc. The need for overcoming the bottleneck provoked by the manual construction of ontologies has generated several studies and research on obtaining semiautomatic methods to learn ontologies. In this sense, this paper proposes a new ontology learning methodology based on semantic role labeling from digital Spanish documents. The method makes it possible to represent multiple semantic relations specially taxonomic and partonomic ones in the standardized OWL 2.0. A set of experiments has been performed with the approach implemented in educational domain that show promising results. 相似文献
24.
25.
26.
27.
Qiushi Chen José E. Andrade Esteban Samaniego 《Computer Methods in Applied Mechanics and Engineering》2011,200(33-36):2473-2482
This work presents a multiscale strong discontinuity approach to tackle key challenges in modeling localization behavior in granular media: accommodation of discontinuities in the kinematic fields, and direct linkage to the underlying grain-scale information. Assumed enhanced strain (AES) concepts are borrowed to enhance elements for post-localization analysis, but are reformulated within a recently-proposed hierarchical multiscale computational framework. Unlike classical AES methods, where material properties are usually constants or assumed to evolve with some arbitrary phenomenological laws, this framework provides a bridge to extract evolutions of key material parameters, such as friction and dilatancy, based on grain scale computational or experimental data. More importantly, the phenomenological softening modulus typically used in AES methods is no longer required. Numerical examples of plane strain compression tests are presented to illustrate the applicability of this method and to analyze its numerical performance. 相似文献
28.
Jaime Pitarch José M Catalá-Civera Felipe L Pe?aranda-Foix Beatriz García-Ba?os 《The Journal of microwave power and electromagnetic energy》2007,41(4):46-61
Waveguide structures are very popular in the microwave power industry due to their power handling capabilities. Modal expansion of the waveguide fields and application of the circuit theory allow for the division of a complex device into several simpler sections which can be analyzed separately with the best suited method. The modal techniques can be divided into two groups--those which analyze junctions or discontinuities and those which examine propagation characteristics. In this paper, a review of modal techniques for high power applications is given. Modal expansion of the fields in the waveguides is then performed and applied to modeling of k-furcated waveguides. The modal analysis based on the Coupled Mode Method is described for the waveguides partially filled with isotropic materials. A hybrid modal analysis coupled with Finite Element Method suitable for more complex waveguide structures is also described. Computational results obtained for some real-life microwave devices are presented. Excellent agreement was found when comparing the results with those generated with a commercial FDTD simulator demonstrates the validity and reliability of the proposed method. 相似文献
29.
Mihai Sima Sorin Cotofaná Jos T. J. Van Eijndhoven Stamatis Vassiliadis Kees Vissers 《The Journal of VLSI Signal Processing》2005,39(3):195-212
This paper presents a TriMedia processor extended with an IDCT reconfigurable design, and assesses the performance gain such an extension has when performing MPEG-2 decoding. We first propose the skeleton of an extension of the TriMedia architecture, which consists of a Field-Programmable Gate Array (FPGA)-based Reconfigurable Functional Unit (RFU), a Configuration Unit managing the reconfiguration of the RFU, and their associated instructions. Then, we address the computation of the 8 × 8 (2-D) IDCT on such extended TriMedia and propose a scheme to implement the 1-D IDCT operation on the RFU. When mapped on an ACEX EP1K100 FPGA from Altera, the proposed 1-D IDCT exhibits a latency of 16 and a recovery of 2 TriMedia@200 MHz cycles, and occupies 45% of the logic cells of the device. By configuring the 1-D IDCT on the RFU at application launch-time, the IEEE-compliant 2-D IDCT can be computed with the throughput of 1/32 IDCT/cycle. This figure translates to an improvement over the standard TriMedia of more than 40% in terms of computing time when 2-D IDCT is carried out in the framework of MPEG-2 decoding. Finally, the proposed reconfigurable IDCT is compared to a number of existing designs.Mihai Sima was born in Bucharest, Romania. He received the MS degree in Electrical Engineering from Politehnica University of Bucharest, and the Ph.D. degree in Electrical Engineering from Delft University of Technology, The Netherlands. He had been with the Microelectronics Company in Bucharest for 3 years, where he was involved in instrumentation electronics for integrated circuit testing. Subsequently, he joined the Telecommunications Department of Politehnica University of Bucharest, where he had been involved in digital signal processing and speech recognition for 6 years. More recently, he had been with the Faculty of Electrical Engineering, Mathematics, and Computer Science, Delft University of Technology, where he worked on reconfigurable architectures for mediaprocessing domain. He is currently an assistant professor with the Department of Electrical and Computer Engineering, University of Victoria, B.C., Canada. His research interests include computer architecture, reconfigurable computing, embedded systems, digital signal processing, and speech recognition.Sorin D. Coofan was born in Mizil, Romania. He received the MS degree in Computer Science from the Politehnica University of Bucharest, Romania, and the Ph.D. degree in Electrical Engineering from Delft University of Technology, The Netherlands. He had worked with the Research & Development Institute for Electronic Components (ICCE) in Bucharest for a decade, being involved in structured design of digital systems, design rule checking of ICs layout, logic and mixed-mode simulation of electronic circuits, testability analysis, and image processing. He is currently an associate professor with the Faculty of Electrical Engineering, Mathematics, and Computer Science, Delft University of Technology, The Netherlands. His research interests include computer arithmetic, parallel architectures, embedded systems, reconfigurable computing, nano-electronics, neural networks, computational geometry, and computer aided design.Jos T.J. van Eijndhoven was born in Roosendaal, The Netherlands. He studied Electrical Engineering at the Eindhoven University of Technology, The Netherlands, obtaining the M.Sc. and Ph.D. degrees in 1981 and 1984, respectively, for a work on piecewise linear circuit simulation. Then, he became a senior research member in the design automation group of the Eindhoven University of Technology. In 1986 he spent a sabbatical period at the IBM Thomas J. Watson Research Laboratory, Yorktown Heights, New York, for research on high level synthesis. In 1998 he joined Philips Research Laboratories in Eindhoven, The Netherlands, to work on the architectural design of programmable multimedia hardware and the associated mapping of media processing applications.Stamatis Vassiliadis was born in Manolates, Samos, Greece. He is a professor with the Faculty of Electrical Engineering, Mathematics, and Computer Science, Delft University of Technology, The Netherlands. He has also served in the faculties of Cornell University, Ithaca, NY, and the State University of New York (S.U.N.Y.), Binghamton, NY.He hadworked for a decade with IBM in the AdvancedWorkstations and Systems laboratory in Austin TX, the Mid-Hudson Valley Laboratory in Poughkeepsie, NY, and the Glendale Laboratory in Endicott, NY. In IBM he was involved in a number of projects regarding computer design, organizations, and architectures and the leadership to advanced research projects. A number of his design and implementation proposals have been implemented in commerciallyavailable systems and processors including the IBM 9370 model 60 computer system, the IBM POWER II, the IBM AS/400 Models 400, 500, and 510, Server Models 40S and 50S, the IBM AS/400 Advanced 36, and the IBM S/390 G4 and G5 computer systems. For his work, he received numerous awards including 23 levels of Publication Achievement Awards, 15 levels of Invention Achievement Awards and an Outstanding Innovation Award for Engineering/Scientific Hardware Design in 1989. In 1990 he has been awarded the highest number of USA patents in IBM, six of his 70 USA patents being rated with the highest patent ranking in IBM.Kees A. Vissers graduated the Delft University of Technology, receiving his M.Sc. in 1980. He started directly with Philips Research Laboratories in Eindhoven where he was involved in highlevel simulation and high-level synthesis. He had been heading the research on hardware/software co-design and system level design for many years, and had a significant contribution to the TriMedia VLIW processor. From 1987 till 1988 he was a visiting researcher at Carnegie Mellon University, Pittsburgh, Pennsylvania, with the group of Don Thomas. He is currently a Research Fellow with University of California at Berkeley, Department of Electrical Engineering and Computer Sciences. His research interests include video processing, embedded media processing systems, and reconfigurable computing. 相似文献
30.
Bazil Taha Ahmed José Luis Masa Campos Jose Maria Lalueza Mayordomo 《Wireless Personal Communications》2012,66(2):251-260
The purpose of this study is to characterize the indoor channel for IEEE 802.16 (WiMAX) at 3.3?C3.6?GHz frequency. This work presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include closed corridor, wide corridor and semi open corridor. Path loss equations are determined using log-distance path loss model and a Rayleigh multipath induced fading, Normal multipath induced fading or a combination of both. A numerical analysis of measurements in each scenario was conducted and the study determined equations that describe path loss for each scenario. Propagation loss is given for 300?MHz bandwidth. This work also represents the insertion loss of different materials and the obstruction loss due the existence of human beings between the transmitting antenna and the receiving one. 相似文献