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   848篇
  免费   48篇
  国内免费   4篇
电工技术   11篇
综合类   2篇
化学工业   218篇
金属工艺   21篇
机械仪表   23篇
建筑科学   43篇
矿业工程   7篇
能源动力   32篇
轻工业   75篇
水利工程   10篇
石油天然气   5篇
无线电   96篇
一般工业技术   169篇
冶金工业   65篇
原子能技术   5篇
自动化技术   118篇
  2024年   3篇
  2023年   9篇
  2022年   22篇
  2021年   27篇
  2020年   26篇
  2019年   24篇
  2018年   27篇
  2017年   31篇
  2016年   29篇
  2015年   30篇
  2014年   32篇
  2013年   62篇
  2012年   46篇
  2011年   66篇
  2010年   39篇
  2009年   37篇
  2008年   35篇
  2007年   39篇
  2006年   34篇
  2005年   23篇
  2004年   13篇
  2003年   24篇
  2002年   17篇
  2001年   13篇
  2000年   7篇
  1999年   15篇
  1998年   17篇
  1997年   16篇
  1996年   10篇
  1995年   9篇
  1994年   10篇
  1993年   6篇
  1992年   7篇
  1991年   6篇
  1990年   9篇
  1989年   5篇
  1988年   5篇
  1987年   10篇
  1986年   3篇
  1985年   6篇
  1983年   4篇
  1982年   4篇
  1980年   4篇
  1979年   5篇
  1976年   6篇
  1973年   4篇
  1972年   5篇
  1970年   2篇
  1968年   2篇
  1966年   2篇
排序方式: 共有900条查询结果,搜索用时 15 毫秒
161.
This paper outlines an historical institutionalist (HI) research agenda for planning history. HI approaches to the understanding of institutions, path dependence, positive feedback effects in public policy, and patterned processes of institutional change offer a robust theoretical framework and a valuable set of conceptual and analytic tools for the analysis of continuity and change in public policy. Yet, to date, there has been no systematic effort to incorporate historical institutionalism into planning history research. The body of the paper proposes planning history relevant definitions of institutions, path dependence, critical junctures, and incremental change processes, outlines recent HI literature applying and extending these concepts, and frames a number of research questions for planning history that these approaches suggest. A concluding section explores the potential application and leverage of HI approaches to the study of planning history and international comparative planning studies and outlines a research agenda.  相似文献   
162.
163.
Bridge infrastructure managers are facing multiple challenges to improve the availability and serviceability of ageing infrastructure, while the maintenance planning is constrained by budget restrictions. Many research efforts are ongoing, for the last few decades, ranging from development of bridge management system, decision support tools, optimisation models, life cycle cost analysis, etc. Since transport infrastructures are deeply embedded in society, they are not only subject to technical requirements, but are required to meet the requirements of societal and economic developments. Therefore, bridge maintenance planning should accommodate multiple performance goals which need to be quantified by various performance indicators. In this paper, an application of Multi-Attribute Utility Theory (MAUT) for bridge maintenance planning is illustrated with a case study of bridges from the Netherlands road network. MAUT seeks to optimise multiple objectives by suggesting a trade-off among them and finally assigns a ranking to the considered bridges. Moreover, utility functions of MAUT appropriately account for the involved uncertainty and risk attitude of infrastructure managers. The main contribution of this study is in presenting a proof-of-concept on how MAUT provides a systematic approach to improve the decision-making of maintenance planning by making use of available data, accommodating multiple performance goals, their uncertainty, and preferences of infrastructure managers.  相似文献   
164.
<正>当一座建筑呈现在室内设计师的眼前时,它往往已经粉刷了墙体,隐藏了所有管线,你已经无法认识它最本原的面貌,设计师无非是在此基础上不断地叠加更多的装饰,让它越来越华丽,遮盖一切最初的痕迹,抹去所有最原始的结构。有没有一位设计师的工作是主动剥去建筑的外衣,让它更加暴露更加原始?总部位于巴西的MNMA Studio就用这样的逆向思维为时尚品牌Haight设计了一个80 m~2零售店,  相似文献   
165.
Biological hazards associated with the collection of solid and compostable waste have not been well characterized in North America. This is an issue because workers who handle such materials may be exposed to bioaerosols (airborne bacteria and fungi) and dusts resulting in infections or allergic diseases. We conducted a personal sampling campaign for culturable bacteria and fungi in the breathing zones of waste collectors in a variety of typical work settings (scenarios) in the province of Quebec, Canada. Total culturable bacterial and fungal counts were analyzed and compared to ambient environmental levels (background) to determine the degree of incremental exposure among workers. In several scenarios, worker exposure counts were significantly (p < or = 0.05) higher than ambient levels measured upwind, with the highest personal exposures to bacteria observed for urban compostable waste collectors (median = 50,300 Colony Forming Units/m(3) of air (CFU/m(3))). On the other hand, fungal counts collected on an every-other-week cycle were highest among a group of rural compostable waste collectors (median = 101,700 CFU/m(3)). Similar exposures to culturable bacteria and fungi have been reported in European workers who showed such adverse health effects as nausea, diarrhea, upper respiratory tract irritation, and allergy. Therefore, it may be necessary to modify certain work practices in order to minimize exposure. Recommendations include automation of waste and compost collection, use of personal protective equipment including goggles, gloves, and disposable masks, and meticulous personal hygiene.  相似文献   
166.
167.
We have studied, by means of neutron powder diffraction, the temperature evolution of the hydrogen solid solutions ZrV2Dx in the intermediate range, 2.18≤x≤2.73, separating two hydrogen-ordered phases, ZrV2D≤2 with k=(1/2, 1/2, 1/2) and ZrV2D≥2.8 with k=(0, 0, 1−δ). Instead of ordinary phase separation, we have found an uncommon phase. This phase is a kind of a disordered one and, simultaneously, it keeps a modulation of hydrogen density with the same k as for the ordered phase, one or another. Under favourable conditions this modulation transforms into the regular ordered phase.  相似文献   
168.
We have studied the crystal structure of the uncommon phase with k=0 in ZrV2Dx, 2.2<x<2.5, which is an intermediate between the hydrogen-disordered phase and two hydrogen superstructures, ZrV2D<2 with k=(1/2 1/2 1/2) and ZrV2D>2.7 with k=(001). This phase is a primary superstructure combining the features of the disordered phase and, depending on the hydrogen concentration, one or another superstructure with k≠0. Its lattice (translational symmetry) is the same as in the disordered phase, which is k=0. Simultaneously, the lattice sites (the hydrogen arrangement in them) are prototypes of the sites of the subsequent superstructure with k≠0. Specifically, each site of the primary superstructure with k=0 is a mix of the sites with different spatial orientation of the superstructure with k≠0. In this sense the primary superstructure can be considered as a ‘lattice liquid crystal’ whereas usual superstructure with k≠0 is a ‘lattice crystal’. In addition, we have determined the crystal structure of the ‘ordered’ phase with k=(001) in ZrV2D2.73. It is a transitional state between the primary superstructure and the regular superstructure with the same k.  相似文献   
169.
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   
170.
Freestanding silicon nanocrystals (Si‐ncs) offer unique optical and electronic properties for new photovoltaic, thermoelectric, and other electronic devices. A method to fabricate Si‐ncs which is scalable to industrial usage has been developed in recent years. However, barriers to the widespread utilization of these nanocrystals are the presence of charge‐trapping defects and an oxide shell formed upon ambient atmosphere exposure hindering the charge transport. Here, we exploit low‐cost post‐growth treatment routes based on wet‐etching in hydrofluoric acid plus surface hydrosilylation or annealing enabling a complete native oxide removal and a reduction of the defect density by up to two orders of magnitude. Moreover, when compared with only H‐terminated Si‐ncs we report an enhancement of the conductivity by up to a factor of 400 for films of HF etched and annealed Si‐ncs, which retain a defect density below that of untreated Si‐ncs even after several months of air exposure. Further, we demonstrate that HF etched and hydrosilylated Si‐ncs are extremely stable against oxidation and maintain a very low defect density after a long‐term storage in air, opening the possibility of device processing in ambient atmosphere.  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