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   296763篇
  免费   26322篇
  国内免费   13881篇
电工技术   21357篇
技术理论   32篇
综合类   28373篇
化学工业   34666篇
金属工艺   12844篇
机械仪表   18834篇
建筑科学   39455篇
矿业工程   18939篇
能源动力   11530篇
轻工业   20183篇
水利工程   15106篇
石油天然气   19313篇
武器工业   3897篇
无线电   18411篇
一般工业技术   22285篇
冶金工业   14187篇
原子能技术   2953篇
自动化技术   34601篇
  2024年   1287篇
  2023年   3817篇
  2022年   7459篇
  2021年   9617篇
  2020年   9614篇
  2019年   7236篇
  2018年   6809篇
  2017年   8730篇
  2016年   10415篇
  2015年   11300篇
  2014年   20268篇
  2013年   18252篇
  2012年   22268篇
  2011年   23996篇
  2010年   17327篇
  2009年   17445篇
  2008年   15780篇
  2007年   19337篇
  2006年   17759篇
  2005年   15416篇
  2004年   13078篇
  2003年   11176篇
  2002年   9172篇
  2001年   7619篇
  2000年   6494篇
  1999年   5109篇
  1998年   3766篇
  1997年   3294篇
  1996年   2671篇
  1995年   2228篇
  1994年   1898篇
  1993年   1275篇
  1992年   1033篇
  1991年   772篇
  1990年   649篇
  1989年   591篇
  1988年   353篇
  1987年   268篇
  1986年   226篇
  1985年   248篇
  1984年   158篇
  1983年   140篇
  1982年   91篇
  1981年   97篇
  1980年   99篇
  1979年   60篇
  1978年   24篇
  1977年   28篇
  1964年   21篇
  1959年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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   
62.
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   
63.
Properly selected transformation methods obtain the most significant characteristics of metal cutting data efficiently and simplify the classification. Wavelet Transformation (WT) and Neural Networks (NN) combination was used to classify the experimental cutting force data of milling operations previously. Preprocessing (PreP) of the approximation coefficients of the WT is proposed just before the classification by using the Adaptive Resonance Theory (ART2) type NNs. Genetic Algorithm (GA) was used to estimate the weights of each coefficient of the PreP. The WT-PreP-NN (ART2) combination worked at lower vigilances by creating only a few meaningful categories without any errors. The WT-NN (ART2) combination could obtain the same error rate only if very high vigilances are used and many categories are allowed.  相似文献   
64.
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   
65.
66.
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   
67.
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   
68.
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   
69.
HLA-DRB1等位基因主要参与人类的抗原免疫功能,对其进行比较研究,有助于追溯人类的进化迁移史,开发类群特异性药物.本研究以Matlab为平台,用自组织竞争网络(Self-Organizing Competitive Neural Network),对世界54个民族和人群、14个HLA-DRB1等位基因,进行了无监督模式分类.结果表明,各民族之间存在差异性,同民族的各人群之间有相似性.西伯利亚各人群,澳洲各土著人群,黑人各人群,南美印第安各人群,犹太族各人群,日本各人群,及欧美白人各人群有相对独立性:南美印第安人与西伯利亚人有高度相似性;中国民族在南方人群和北方人群间存在较大差异;中国汉族中,广东汉族地位特殊,与少数民族如拉祜族、瑶族关系密切.  相似文献   
70.
传统的水面流速流向测量多采用经纬仪交会法,此法需要大量的人力和设备,工作量大且费时。近几年,随着全球定位系统(GPS)的广泛应用和实践,在一定范围内,采用GPS定位法替代经纬仪交会法施测水面流速流向。介绍了GPS定位法的测量原理、设备,以及测量方法。通过对GPS定位法的精度和优缺点的分析,得出采用GPS定位法施测水面流速流向具有较高的推广价值。  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