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   435286篇
  免费   29636篇
  国内免费   16095篇
电工技术   21873篇
技术理论   48篇
综合类   27253篇
化学工业   70316篇
金属工艺   25226篇
机械仪表   25321篇
建筑科学   29829篇
矿业工程   12214篇
能源动力   10734篇
轻工业   27545篇
水利工程   7987篇
石油天然气   23778篇
武器工业   2838篇
无线电   47434篇
一般工业技术   54312篇
冶金工业   21026篇
原子能技术   3895篇
自动化技术   69388篇
  2024年   1473篇
  2023年   5609篇
  2022年   9985篇
  2021年   13971篇
  2020年   10529篇
  2019年   8606篇
  2018年   22828篇
  2017年   23180篇
  2016年   19209篇
  2015年   14495篇
  2014年   17787篇
  2013年   21235篇
  2012年   25724篇
  2011年   34047篇
  2010年   29987篇
  2009年   26217篇
  2008年   27030篇
  2007年   27158篇
  2006年   20272篇
  2005年   18859篇
  2004年   13062篇
  2003年   11839篇
  2002年   10448篇
  2001年   8933篇
  2000年   8963篇
  1999年   9481篇
  1998年   7244篇
  1997年   6177篇
  1996年   5877篇
  1995年   4814篇
  1994年   3913篇
  1993年   2644篇
  1992年   2093篇
  1991年   1596篇
  1990年   1237篇
  1989年   998篇
  1988年   846篇
  1987年   527篇
  1986年   411篇
  1985年   259篇
  1984年   206篇
  1983年   164篇
  1982年   128篇
  1981年   76篇
  1980年   97篇
  1968年   46篇
  1966年   45篇
  1965年   45篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
本文对吉林油田低注入井五参数测井过程中遇到的一些问题进行分析,并相应提出一系列行之有效的解决方法。  相似文献   
4.
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6.  相似文献   
5.
针对和成矿业井下原矿含泥量和含水量较大,且矿泥中存在绿泥石、高岭土等黏土类矿物,造成供矿系统粘堵严重,系统台时量仅为设计水平一半的问题,对原矿进行了洗矿工艺研究。通过洗矿工艺,将原矿中的矿块和矿泥分离,实现矿块和矿泥按粒度分选,彻底解决了供矿系统粘堵严重的问题,稳定了磨选系统给矿量。  相似文献   
6.
Amino acid modified polyaspartic acids were evaluated as calcium-scale inhibitors. Feasibility of scale inhibition experiments was analyzed by molecular dynamics simulation and Gaussian optimization, and the scale inhibition mechanism was theoretically analyzed. Scale inhibition performance was studied by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, static scale inhibition experiments, and electrochemical performance testing, which provided an experimental basis for the molecular dynamics simulation. The experimental results showed that Arg-SA-PASP has better scale inhibition and corrosion inhibition performance than His-SA-PASP. The scale inhibition effect increased with increasing concentration. Electrochemical tests indicated that Arg-SA-PASP is an excellent scale and corrosion inhibitor.  相似文献   
7.
8.
9.
10.
Malondialdehyde (MDA) was selected to represent a secondary by-product of lipid peroxidation during rice ageing. This study aimed to investigate the effects of MDA modification on the structural characteristics of rice protein. The results showed that as MDA concentration increased, rice protein carbonyl and disulphide groups increased, but sulphydryl content decreased. The blue shift of maximum fluorescence peak, the decrease of rice protein intrinsic fluorescence intensity and the reduction of surface hydrophobicity indicated the formation of protein aggregates caused by MDA oxidative modification. The results of molecular weight distribution and particle size distribution showed that MDA modification resulted in the formation of soluble protein aggregates, and the decrease of rice protein solubility indicated that insoluble protein aggregates were formed. Results of protein electrophoresis showed that MDA modification contributed to rice protein aggregation via non-disulphide covalent bonds. The results showed that rice protein gradually aggregated with increasing MDA concentration.  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