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   288篇
  免费   2篇
电工技术   7篇
综合类   1篇
化学工业   50篇
金属工艺   4篇
机械仪表   7篇
建筑科学   21篇
矿业工程   1篇
能源动力   8篇
轻工业   19篇
石油天然气   2篇
无线电   27篇
一般工业技术   60篇
冶金工业   68篇
原子能技术   1篇
自动化技术   14篇
  2023年   2篇
  2022年   3篇
  2021年   4篇
  2020年   7篇
  2019年   6篇
  2018年   4篇
  2017年   3篇
  2016年   2篇
  2015年   5篇
  2014年   9篇
  2013年   12篇
  2012年   4篇
  2011年   10篇
  2010年   10篇
  2009年   11篇
  2008年   9篇
  2007年   5篇
  2006年   5篇
  2005年   4篇
  2004年   7篇
  2003年   9篇
  2002年   8篇
  2001年   11篇
  2000年   2篇
  1999年   6篇
  1998年   18篇
  1997年   14篇
  1996年   11篇
  1995年   11篇
  1994年   8篇
  1993年   7篇
  1990年   6篇
  1989年   3篇
  1988年   4篇
  1986年   5篇
  1985年   4篇
  1984年   3篇
  1983年   4篇
  1981年   5篇
  1980年   3篇
  1978年   4篇
  1976年   6篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
  1971年   3篇
  1967年   1篇
  1966年   1篇
  1942年   1篇
  1927年   1篇
排序方式: 共有290条查询结果,搜索用时 15 毫秒
31.
    
Alkyldiphenylphosphine oxides typically undergo α‐deprotonation with alkyllithium reagents. Here, the lithiation of differentially branched alkyldiphenylphosphine oxides was investigated and a diverse, but predictable reactivity was found. γ‐Branched derivatives undergo selective directed ortho‐metalation (DoM) using butyllithium and TMEDA as an additive. With decreasing degree of γ‐branching α‐lithiation becomes predominant. The ortho‐phosphinoyllithium intermediates are subject to functionalization and C C bond forming reactions, thus providing a convenient approach to new phosphine oxides and phosphine‐borane complexes, which have a good potential for an approach to new ligands for catalysis.

  相似文献   

32.
33.
A field-programmable, stackable memory cell using 0.15-/spl mu/m technology is demonstrated. Vertical polycrystalline silicon diodes are stacked on top of one another, with tungsten (with TiN adhesion film) interconnect wires. An SiO/sub 2/ antifuse film separates the top of each diode from the TiN-W films. The cell is programmed when sufficient biasing voltage is applied to break down the antifuse, connecting the diode to tungsten. The cell is unprogrammed when the antifuse is intact. Cell fabrication and performance are described.  相似文献   
34.
A hybrid simulation tool for real-time performance measurements of complete networks is presented. The simulation tool combines the advantages of software and hardware modules. Recorded channel data are included. They allow the reproduction of realistic situations in the laboratory. Synchronization problems and noise are considered. As an example, stabilized slotted ALOHA access protocols were implemented and investigated in land-mobile satellite environments. A slotted ALOHA-based modified channel access strategy for highly unreliable channels is proposed requiring all mobile stations to estimate the link quality before starting a transmission. The different strategies are analyzed by simulation as well as the analytical methods. Transmission parameters are determined and optimized using a combination of analysis and simulation. The results show the power of the simulation tool and the better performance of stabilized slotted ALOHA with link-quality estimation in city channels  相似文献   
35.
Ilse Jahn 《NTM》1993,1(1):37-55
Early zoological researches by P.S. Pallas and K.E. von Baer in their letters to the zoologists of Berlin. The centenaries which are celebrated in 1991 and 1992 in memory of P.S. Pallas (1791) and K.E. von Baer (born 1792) caused the following studies of hitherto unpublished sources, preserved in the collections of the Museum für naturkunde in Berlin. The earliest zoological works of Pallas are discussed in relation to his last publication on the “Zoographia Rosso-Asiatica” which should have been finished in Berlin. Some years after the death of Pallas, Baer also contacted the Berlin zoologists K.A. Rudolphi and M.H. Lichtenstein, asking for help, when he was going to establish zoology and a zoological museum at the University of Königsberg.  相似文献   
36.
37.
We report a case of birdshot retinochoroidopathy following a cataract surgery in a 78-year-old man. Low-grade forms of the affection may be discovered lately on a recurrence of the inflammation following any event as an ocular surgical procedure. Medical management of cataract surgery in uveitis is then discussed.  相似文献   
38.
In this paper, we report a methodology, developed in the context of Smart Energy Efficient Middleware for Public Spaces European Project, aimed at exploiting ICT monitoring and control services to reduce energy usage and CO2 footprint in existing buildings. The approach does not require significant construction work as it is based on commercial-off-the-shelf devices and, where present, it exploits and integrates existing building management systems with new sensors and actuator networks. To make this possible, the proposed approach leverages upon the following main contributions: (a) to develop an integrated building automation and control system, (b) to implement a middleware for the energy-efficient buildings domain, (c) to provide a multi-dimensional building information modelling-based visualisation, and (d) to raise people’s awareness about energy efficiency. The research approach adopted in the project started with the selection, as case studies, of representative test and reference rooms in modern and historical buildings chosen for having different requirements and constraints in term of sensing and control technologies. Then, according to the features of the selected rooms, the strategies to reduce the energy consumptions were defined, taking into account the potential savings related to lighting, heating, ventilation, and air conditioning (HVAC) systems and other device loads (PC, printers, etc.). The strategies include both the control of building services and devices and the monitoring of environmental conditions and energy consumption. In the paper, the energy savings estimated through simulation, for both HVAC and lighting, are presented to highlight the potential of the designed system. After the implementation of the system in the demonstrator, results will be compared with the monitored data.  相似文献   
39.
40.
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