首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   556篇
  免费   16篇
  国内免费   4篇
电工技术   17篇
化学工业   128篇
金属工艺   5篇
机械仪表   4篇
建筑科学   28篇
矿业工程   6篇
能源动力   23篇
轻工业   63篇
水利工程   1篇
无线电   62篇
一般工业技术   68篇
冶金工业   64篇
原子能技术   5篇
自动化技术   102篇
  2024年   2篇
  2023年   2篇
  2022年   11篇
  2021年   10篇
  2020年   7篇
  2019年   12篇
  2018年   13篇
  2017年   13篇
  2016年   16篇
  2015年   14篇
  2014年   12篇
  2013年   26篇
  2012年   23篇
  2011年   30篇
  2010年   24篇
  2009年   34篇
  2008年   40篇
  2007年   23篇
  2006年   24篇
  2005年   22篇
  2004年   22篇
  2003年   18篇
  2002年   30篇
  2001年   7篇
  2000年   6篇
  1999年   12篇
  1998年   25篇
  1997年   23篇
  1996年   5篇
  1995年   11篇
  1994年   6篇
  1993年   4篇
  1992年   5篇
  1991年   10篇
  1990年   3篇
  1989年   1篇
  1988年   2篇
  1987年   2篇
  1985年   1篇
  1984年   3篇
  1983年   3篇
  1982年   3篇
  1981年   2篇
  1979年   2篇
  1978年   4篇
  1975年   1篇
  1970年   1篇
  1966年   1篇
  1964年   3篇
  1963年   2篇
排序方式: 共有576条查询结果,搜索用时 15 毫秒
151.
The State of the Art in Mobile Graphics Research   总被引:1,自引:0,他引:1  
High-quality computer graphics let mobile-device users access more compelling content. Still, the devices' limitations and requirements differ substantially from those of a PC. This survey of mobile graphics research describes current solutions in terms of specialized hardware (including 3D displays), rendering and transmission, visualization, and user interfaces.  相似文献   
152.
Mobile graphics     
Mobile phones form a ubiquitous graphics platform; over half of the world population uses them. This special issue presents solutions that overcome some of the inherent limitations of these compact computing devices and make use of the fact that they are available at all times, not just at your desk.  相似文献   
153.
There is considerable debate in the information systems literature on how systems development methods (SDMs) are used in practice. On one side are those who take the position that these methods are not used at all. The other side posits that SDMs are used but not in the manner intended by the method developers. In practice, SDMs are adapted and modified to meet project exigencies, which results in unique methods‐in‐use in each project. We subscribe to the latter view and extend the argument by proposing that SDM modifications happen due to mismatches between the paradigmatic values inherent in the SDM, the method users and the organizational context. Further, planned modifications themselves result in shifts of paradigmatic values inherent in the SDM. To examine our contention, we conduct a case study in which we trace an SDM from its development to its deployment and use in an organization. We show where the mismatches occurred and provide explanations for the mismatches. Our results indicate that paradigm differences explain most of the mismatches, and different factors contribute to the paradigm drifts simultaneously, even towards diverging orientations. We conclude that the true value of an SDM, in addition to its tool and technique use, is a basis for examining and self‐reflecting about paradigmatic values. This is an essential part of learning to develop systems.  相似文献   
154.
Real-time arrival information, immediately available on mobile devices, can significantly enhance the usability of public transit systems. The OneBusAway system provides just such information to more than 7,000 Seattle-area bus riders per day. The authors describe a new location-aware native iPhone application for OneBusAway that provides bus stop and arrival information tailored to the user's location. Results from survey and user-study evaluations demonstrate quicker access to data using the location-aware tool. In addition, data for OneBusAway users as a whole show strikingly positive changes in rider satisfaction, the number of transit trips per week, reduced wait time at bus stops, and increased walking. The positive results also hold for the location-aware version users, suggesting the possibility of even further gains.  相似文献   
155.
In this paper we consider numerical methods for stationary free boundary problems. We start by analysing systematically different shape optimization formulations of a model problem and show how the optimality conditions relate to construction of trial type methods. Shape sensitivity analysis of the free boundary leads also to the so‐called total linearization method which combines the good properties of Newton method and trial methods, i.e. fast convergence and relative simplicity of implementation. Detailed implementation for a model problem together with numerical tests is presented. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   
156.
The major objective of the present study was to prepare structured lipids rich in stearic acid from rice bran oil (RBO) using immobilized lipase (IM 60) from Rhizomucor miehei. The effects of incubation time and temperature, substrate molar ratio, and enzyme load on incorporation of stearic acid were studied. Acidolysis reactions were performed in hexane. Pancreatic lipase‐catalyzed sn‐2 positional analysis and tocopherol analyses were performed before and after enzymatic modification. The kinetics of the reaction was studied and maximum incorporation of stearic acid was observed at 6 h, at 37 °C, when the triacylglycerol and stearic acid molar ratio was maintained at 1 : 6 and the enzyme concentration was 10% of total substrates weight. Stearic acid in RBO after acidolysis was increased from 2.28 to 48.5%, with a simultaneous decrease in palmitic, oleic and linoleic acids. HPLC analysis of tocopherols and tocotrienols was carried out and their content in modified RBO was not significantly affected compared to that of native RBO. The oryzanol content of the modified RBO was reduced from 1.02 to 0.68%. Melting and crystallizing characteristics of the modified fat were studied using differential scanning calorimetry. The total solid fat content at 25 °C increased from 26.12 to 34.8% with an increase in stearic acid incorporation into RBO from 38 to 48%, but it was comparatively less than for cocoa butter and vanaspati. However, the modified RBO completely melted at 37 °C and was useful as plastic fat for various culinary purposes, bakery and confectionary applications. The results of the present study indicated that structured lipids prepared from RBO rich in stearic acid retained their beneficial nutraceuticals; in addition, they do not contain any trans fatty acids.  相似文献   
157.
Infertility is assumed to arise exclusively from male- and female-dependent pathological factors. However, recent studies have indicated that reproductive failure may also result from the reproductive incompatibility of the partners. Selection against such incompatibilities likely occurs via female-derived reproductive secretions, including follicular fluid (FF), that mediate gamete-level mate choice towards the sperm of specific males. To facilitate potential development of diagnostic tests for human reproductive incompatibility, we examined whether sperm physiological response to female serum indicate male–female compatibility in the presence of FF. We performed a full-factorial experiment, in which the sperm of 10 males were treated with the FF and serum of 6 healthy females. We found that sperm motility and viability in both biofluids were highly similar and that in 70% of the males, sperm serum treatment predicted male–female compatibility. We also identified male human leucocyte antigen (HLA) alleles and female (FF and serum) anti-HLA antibodies and tested whether the number of allele–antibody matches predict sperm physiological response to female fluids. However, no association was found between measured sperm traits and the number of allele–antibody matches. Overall, the present results may open novel possibilities for the future development of reproductive incompatibility tests and may pave the way towards more accurate infertility diagnostics and treatments.  相似文献   
158.
Within the IAEA coordinated programme on optimizing of reactor pressure vessel surveillance programmes and their analysis, phase 3, a specially tailored radiation sensitive correlation monitor material, a Japanese steel plate with code designation JRQ, a French forging material (FFA) and a Japanese forging material (JFL) were selected for the investigations to be carried out in Finland.Based on the evaluation of the experimental results it was demonstrated that dynamic fracture toughness transition shift is equivalent to the Charpy-V shift, but the static fracture toughness transition shift may be considerably larger than the dyanamic shift. Thus, Charpy-V is not suitable for estimating the static fracture toughness transition shift.These findings have a strong impact upon the design of future surveillance programmes.  相似文献   
159.
In this article simulation and measurement results of a FPGA implementation of a baseband digital complex gain predistorter with a quadrature modulator and demodulation error correction circuits are presented. Four different methods for finding the quadrature error correction values are compared and the effect of quadrature errors to predistortion is discussed. A 50 dB three stage power amplifier chain with an analog quadrature modulator and demodulator was used in the measurements as the device to be predistorted. The signal used in the measurements and simulations was a 30 dBm 18 kHz 16-QAM signal at 400 MHz carrier frequency. In the measurements 15 dB reduction in 3rd order nonlinearity was achieved. The usage of quadrature error correction reduced the adjacent channel power by 9 dB. Ilari Teikari was born in Tampere, Finland, in 1978. He received the M.Sc. (tech.) degree from Helsinki University of Technology (HUT), Helsinki, Finland, in 2002. He is currently working toward D.Sc. (tech) degree in the electronic circuit design laboratory, HUT. His current research intrests are in the area of power amplifier linearization methods and digital circuit design. Jouko Vankka was born in Helsinki, Finland, in 1965. He received the M.S. and Ph.D. degrees in electrical engineering from Helsinki University of Technology (HUT) in 1991 and 2000, respectively. Since 1995, he has been with the Electronic Circuit Design Laboratory, HUT. His research interests include VLSI architectures and mixed-signal integrated circuits for communication applications. Kari A. I. Halonen was born in Helsinki, Finland, on May 23, 1958. He received the M.Sc. degree in electrical engineering from Helsinki University of Technology, Finland, in 1982, and the Ph.D. degree in electrical engineering from the Katholieke Universiteit Leuven, in Heverlee, Belgium, in 1987. From 1982 to 1984 he was employed as assistant at Helsinki University of Technology and as research assistant at the Technical Research Center of Finland. From 1984 to 1987 he was a research assistant at the E.S.A.T. Laboratory of the Katholieke Universiteit Leuven, enjoying also a temporary grant of the Academy of Finland. Since 1988 he has been with the Electronic Circuit Design Laboratory, Helsinki University of Technology, as senior assistant (1988–1990), and the director of the Integrated Circuit Design Unit of the Microelectronics Center (1990–1993). He was on leave of absence the academic year 1992–1993, acting as R&D manager in Fincitec Inc., Finland. From 1993 to 1996 he has been an associate professor, and since 1997 a full professor at the Faculty of Electrical Engineering and Telecommunications, Helsinki University of Technology. He became the Head of Electronic Circuit Design Laboratory year 1998. From 1997 to 1999 he was an associate editor of IEEE Transactions on Circuits and Systems I. He has been a guest editor for IEEE Journal of Solid-State Circuits and the Technical Program Committee Chairman for European Solid-State Circuits Conference year 2000. He has been awarded the Beatrice Winner Award in ISSCC'02 Conference year 2002. He specializes in CMOS and BiCMOS analog integrated circuits, particularly for telecommunication applications. He is author or co-author over a hundred and fifty international and national conference and journal publications on analog integrated circuits. He has several patents on analog integrated circuits.  相似文献   
160.
Most studies of counterproductive work behavior (CWB) are criticized for overreliance on self-report methodology. This study tested the convergence of 136 matched self-reports and coworker-reports of work stressors and CWB. For each participant dyad, the focal employee ("incumbent") completed a self-report survey and gave a coworker form to a peer familiar with the incumbent's work situation and behavior. Correlations and t tests demonstrated significant convergence between incumbent and coworker reports of key study variables, except organization-targeted CWB. Separately, both incumbent and coworker reports supported the Stressor-Emotion CWB model. In mixed-source analyses, only interpersonal relationships were significant--conflict and CWB targeting persons. Weaknesses in each report source are discussed, and multisourced triangulation to cover perceptual, experiential, and behavioral domains is recommended. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号