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   251730篇
  免费   22936篇
  国内免费   11046篇
电工技术   23941篇
技术理论   32篇
综合类   24644篇
化学工业   29827篇
金属工艺   10955篇
机械仪表   12366篇
建筑科学   35318篇
矿业工程   14297篇
能源动力   8934篇
轻工业   17512篇
水利工程   12222篇
石油天然气   14056篇
武器工业   3346篇
无线电   16342篇
一般工业技术   17689篇
冶金工业   12717篇
原子能技术   1996篇
自动化技术   29518篇
  2024年   1124篇
  2023年   3233篇
  2022年   6282篇
  2021年   8182篇
  2020年   7948篇
  2019年   5990篇
  2018年   5588篇
  2017年   7161篇
  2016年   8586篇
  2015年   9373篇
  2014年   17325篇
  2013年   14704篇
  2012年   18199篇
  2011年   20181篇
  2010年   14918篇
  2009年   15228篇
  2008年   13923篇
  2007年   16960篇
  2006年   15488篇
  2005年   13465篇
  2004年   11164篇
  2003年   9879篇
  2002年   8002篇
  2001年   6617篇
  2000年   5671篇
  1999年   4393篇
  1998年   3054篇
  1997年   2644篇
  1996年   2144篇
  1995年   1794篇
  1994年   1473篇
  1993年   1033篇
  1992年   828篇
  1991年   584篇
  1990年   500篇
  1989年   463篇
  1988年   275篇
  1987年   206篇
  1986年   180篇
  1985年   195篇
  1984年   150篇
  1983年   117篇
  1982年   63篇
  1981年   84篇
  1980年   83篇
  1979年   38篇
  1978年   22篇
  1977年   22篇
  1975年   17篇
  1959年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
This article presents a two-dimensional transient model for gas-solids flow and heat transfer through pipes using the coupled Computational Fluid Dynamics and Discrete Element Method approach. Numerical simulations have been conducted to examine the modification of fluid thermal structure due to the presence of particles in a pneumatic transport pipeline. Modeled results have demonstrated the key role of transversal motion of rebounding particles in the pipe cross section in altering fluid temperature. Further implementation of this modeling technique in air-drying processes is discussed and possible experimental methods for the measurement of in situ particle and fluid motion and temperature profile are cited.  相似文献   
53.
Wood shaving samples were heated in both cubic baskets and in a previously described system realising the conditions of the ‘infinite slab’ in thermal ignition. Results from the two sets of experiment were found to be totally consistent with each other.  相似文献   
54.
55.
Safe and Economic Operation of Power Plants – Research Results in the Field of Materials, Design and Maintenance Components of power plants which undergo high temperatures are subjected to complex loading situations. The requirements on the used materials result from the special operation conditions of the plants and have to be adjusted to the steadily growing requirements on higher efficiency of the complete power plant as well as to those of safe and economic operation. The expenses for control and downtimes are directly connected with economic efficiency and availability. However, in case of new procedures or components it is not possible to revert to the existing know‐how. Different failure mechanisms than known before can occur. The same goes for the load situation. Therefore the knowledge base has to be extended to in‐advance or even parallely running scientific examinations that life assessment and maintenance strategies can be applied which guarantee the operational reliability and the efficiency of the plant. The main emphasis of these F&E works has to be put on condition monitoring based on actual operational data, the standard materials’ and component’s behaviour (deformation, damage and failure behaviour) in connection with design of components and the related material laws. In the framework of applied AVIF projects, following problems are handled:. – qualification of materials by determinating parameters related to practise. – optimal design of components by making available material laws and numerical tools. – economic manufacturing of components by qualifying processing methods such as welding. – The results can be transferred to concepts for safe and economic operation of power plants, especially for newly introduced materials for which there is no operational experience available.  相似文献   
56.
龙新良 《煤炭技术》2003,22(2):49-51
总结了实际工作中防突管理的经验和问题 ,探讨了科学理论与具体实际的有机结合与统一 ,采取针对性强的有效措施 ,确保突出矿井的安全生产  相似文献   
57.
58.
全文围绕树立和落实科学发展观这一主题 ,研究和探索如何在新时期、新阶段进一步做好国土资源管理工作的新思路、新途径和新方法。提出要进一步加强国土资源宏观管理 ,更好地为甘肃省经济社会的协调、可持续发展提供保障服务。  相似文献   
59.
BACKGROUND: Two peat biofilters were used for the removal of toluene from air for one year. One biofilter was fed with pure toluene and the other received 1:1 (by weight) ethyl acetate:toluene mixture. RESULTS: The biofilters were operated under continuous loading: the toluene inlet load (IL) at which 80% removal occurred was 116 g m?3 h?1 at 57 s gas residence time. Maximum elimination capacity of 360 g m?3 h?1 was obtained at an IL of 745 g m?3 h?1. The elimination of toluene was inhibited by the presence of ethyl acetate. Intermittent loading, with pollutants supplied for 16 h/day, 5 days/week, did not significantly affect the removal efficiency (RE). Biomass was fully activated in 2 h after night closures, but 6 h were required to recover RE after weekend closures. Live cell density remained relatively constant over the operational period, while the dead cell fraction increased. Finally, a 15 day starvation period was applied and operation then re‐started. Performance was restored with similar re‐acclimatization period to that after weekend closures, and a reduction in dead cell fraction was observed. CONCLUSION: This study demonstrates the capacity of the system to handle intermittent loading conditions that are common in industrial practices, including long‐term starvation. Copyright © 2008 Society of Chemical Industry  相似文献   
60.
艺术建筑设计的探索   总被引:1,自引:0,他引:1  
通过徐州一中艺术楼的设计实践,寻求优美而独特的艺术形象,并用纯几何形体的组合来达到功能与形式的完美统一。  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