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   44574篇
  免费   4472篇
  国内免费   2059篇
电工技术   10872篇
技术理论   2篇
综合类   4377篇
化学工业   4212篇
金属工艺   1770篇
机械仪表   1467篇
建筑科学   6230篇
矿业工程   1845篇
能源动力   904篇
轻工业   1689篇
水利工程   2062篇
石油天然气   1976篇
武器工业   239篇
无线电   3196篇
一般工业技术   2258篇
冶金工业   1537篇
原子能技术   476篇
自动化技术   5993篇
  2024年   88篇
  2023年   356篇
  2022年   904篇
  2021年   1109篇
  2020年   1059篇
  2019年   836篇
  2018年   763篇
  2017年   1053篇
  2016年   1194篇
  2015年   1478篇
  2014年   3387篇
  2013年   2297篇
  2012年   3542篇
  2011年   3804篇
  2010年   2970篇
  2009年   3091篇
  2008年   2770篇
  2007年   3310篇
  2006年   3081篇
  2005年   2707篇
  2004年   2129篇
  2003年   1968篇
  2002年   1625篇
  2001年   1382篇
  2000年   1172篇
  1999年   844篇
  1998年   498篇
  1997年   372篇
  1996年   318篇
  1995年   284篇
  1994年   191篇
  1993年   109篇
  1992年   83篇
  1991年   65篇
  1990年   44篇
  1989年   39篇
  1988年   44篇
  1987年   21篇
  1986年   23篇
  1985年   22篇
  1984年   30篇
  1983年   6篇
  1982年   5篇
  1981年   9篇
  1979年   3篇
  1975年   2篇
  1961年   3篇
  1959年   3篇
  1954年   2篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
11.
《Ceramics International》2021,47(23):33280-33285
This study investigated carbon nanotube filtration technology using catalyst particles supported on silicalite-1–biomorphic carbon materials (BCMs). Aqueous solutions of Mn(II), Cu(II), Cr(III), Cd(II), and Pb(II) were used to test the efficiency of heavy metal ions removal. Carbon nanotubes (CNTs) were synthesized and grown on BCMs by the chemical vapor deposition method catalyzed with the catalyst (Co, Fe, and Ni). The synthesized CNTs with Co– and Fe– nanoparticles were typically multi-walled carbon nanotubes, and they showed good crystallinity (ID/IG = 1.05) and yield of (11.10 and 8.86) %. The removal efficiency of Mn(II), Cu(II), Cr(III), Cd(II), and Pb(II) ions using Co-catalyzed CNT filter was 97.57%, 98.01%, 97.89%, 97.42%, and 99.99%, respectively.  相似文献   
12.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。  相似文献   
13.
This paper deals with the application of wavelet transforms for the detection, classification and location of faults on transmission lines. A Global Positioning System clock is used to synchronize sampling of voltage and current signals at both the ends of the transmission line. The detail coefficients of current signals of both the ends are utilized to calculate fault indices. These fault indices are compared with threshold values to detect and classify the faults. Artificial Neural Networks are employed to locate the fault, which make use of approximate decompositions of the voltages and currents of local end. The proposed algorithm is tested successfully for different locations and types of faults.  相似文献   
14.
从电焊机自身电气特点及建筑工地工作环境入手,探讨电焊机安全技术的实施方法。分析电焊机安全隐患及事故的分类以及电焊机在使用过程中产生危险的原因。介绍电焊机在安装以及作业过程中的安全措施。  相似文献   
15.
16.
17.
A double optimal projection method that involves projections for intra-cluster and inter-cluster dimensionality reduction are proposed for video fingerprinting. The video is initially set as a graph with frames as its vertices in a high-dimensional space. A similarity measure that can compute the weights of the edges is then proposed. Subsequently, the video frames are partitioned into different clusters based on the graph model. Double optimal projection is used to explore the optimal mapping points in a low-dimensional space to reduce the video dimensions. The statistics and geometrical fingerprints are generated to determine whether a query video is copied from one of the videos in the database. During matching, the video can be roughly matched by utilizing the statistics fingerprint. Further matching is thereafter performed in the corresponding group using geometrical fingerprints. Experimental results show the good performance of the proposed video fingerprinting method in robustness and discrimination.  相似文献   
18.
随着大数据和云计算的技术的深入应用,人工智能时代的机器学习和深度学习更需要日益增长的数据,因此数据安全与隐私保护变得更加迫切。本文介绍人工智能的定义以及特征,探究数据安全和隐私保护现状,分析数据安全和隐私保护面临的诸多问题,并提出在人工智能时代对数据安全和隐私保护的措施。  相似文献   
19.
随着我国环境保护法规《大气污染防治法》的修订和《涂料征收消费税通知》的公布,探讨了其对船舶涂料企业的冲击及其应对措施。  相似文献   
20.
The potential use of stem cell-based therapies for the repair and regeneration of various tissues and organs is a major goal in repair medicine. Stem cells are classified by their potential to differentiate into functional cells. Compared with other sources, adipose-derived stem cells (ADSCs) have the advantage of being abundant and easy to obtain. ADSCs are considered to be tools for replacing, repairing, and regenerating dead or damaged cells. The capacity of ADSCs to maintain their properties depends on the balance of complex signals in their microenvironment. Their properties and the associated outcomes are in part regulated by reactive oxygen species, which mediate the oxidation-reduction state of cells as a secondary messenger. ADSC therapy has demonstrated beneficial effects, suggesting that secreted factors may provide protection. There is evidence that ADSCs secrete a number of cytokines, growth factors, and antioxidant factors into their microenvironment, thus regulating intracellular signaling pathways in neighboring cells. In this review, we introduce the roles of ADSCs in the protection of cells by modulating inflammation and immunity, and we develop their potential therapeutic properties.  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