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   56511篇
  免费   3757篇
  国内免费   49篇
电工技术   441篇
综合类   25篇
化学工业   11627篇
金属工艺   1072篇
机械仪表   1201篇
建筑科学   1832篇
矿业工程   150篇
能源动力   1162篇
轻工业   9483篇
水利工程   576篇
石油天然气   222篇
武器工业   6篇
无线电   2430篇
一般工业技术   9813篇
冶金工业   11602篇
原子能技术   265篇
自动化技术   8410篇
  2023年   533篇
  2022年   578篇
  2021年   1424篇
  2020年   1223篇
  2019年   1333篇
  2018年   2351篇
  2017年   2322篇
  2016年   2455篇
  2015年   1817篇
  2014年   2276篇
  2013年   4686篇
  2012年   3364篇
  2011年   3170篇
  2010年   2660篇
  2009年   2346篇
  2008年   2329篇
  2007年   2120篇
  2006年   1483篇
  2005年   1207篇
  2004年   1127篇
  2003年   1058篇
  2002年   995篇
  2001年   709篇
  2000年   682篇
  1999年   722篇
  1998年   3576篇
  1997年   2406篇
  1996年   1570篇
  1995年   926篇
  1994年   736篇
  1993年   796篇
  1992年   319篇
  1991年   296篇
  1990年   236篇
  1989年   249篇
  1988年   243篇
  1987年   223篇
  1986年   211篇
  1985年   261篇
  1984年   229篇
  1983年   168篇
  1982年   204篇
  1981年   237篇
  1980年   242篇
  1979年   138篇
  1978年   131篇
  1977年   377篇
  1976年   768篇
  1975年   109篇
  1973年   127篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
991.
This research focused on determining the sociocultural factors that build the social perception of the social roles of senior citizens in Chile in the 2002–2012 period. For this purpose, public opinion was studied in newspapers El Mercurio and La Cuarta. Specialized opinion included the Senior Citizen Program of Pontificia Universidad Católica de Chile, the National Service for Senior Citizens, the Social Observatory for Aging and Old Age of Universidad de Chile, and the Society of Geriatrics and Gerontology of Chile. A comprehensive methodology was used, along with a bibliographical four-stage design. The following ten sociocultural factors were identified: Health and Quality of Life, Studies and Data, Social Images of Aging, Gerontological Concepts and Sociopolitical Participation, Gerontological Policies, Plans and Principles, Aging, Production and Gender, Institutionalization, Demographic Growth, Gerontological Training, and Exclusion and Old Age. This work suggests modifying the conceptual premise that emphasizes the inexistence of a social role for elderly people with a vision centered on the heterogeneity of social roles under permanent sociocultural construction.  相似文献   
992.
993.
994.
995.
In this paper, we address the problem of globally localizing and tracking the pose of a camera‐equipped micro aerial vehicle (MAV) flying in urban streets at low altitudes without GPS. An image‐based global positioning system is introduced to localize the MAV with respect to the surrounding buildings. We propose a novel air‐ground image‐matching algorithm to search the airborne image of the MAV within a ground‐level, geotagged image database. Based on the detected matching image features, we infer the global position of the MAV by back‐projecting the corresponding image points onto a cadastral three‐dimensional city model. Furthermore, we describe an algorithm to track the position of the flying vehicle over several frames and to correct the accumulated drift of the visual odometry whenever a good match is detected between the airborne and the ground‐level images. The proposed approach is tested on a 2 km trajectory with a small quadrocopter flying in the streets of Zurich. Our vision‐based global localization can robustly handle extreme changes in viewpoint, illumination, perceptual aliasing, and over‐season variations, thus outperforming conventional visual place‐recognition approaches. The dataset is made publicly available to the research community. To the best of our knowledge, this is the first work that studies and demonstrates global localization and position tracking of a drone in urban streets with a single onboard camera.  相似文献   
996.
997.
998.
999.
1000.
This review documents the uses of quantitative MS applied to colorectal cancer (CRC) proteomics for biomarker discovery and molecular pathway profiling. Investigators are adopting various labeling and label-free MS approaches to quantitate differential protein levels in cells, tumors, and plasma/serum. We comprehensively review recent uses of this technology to examine mouse models of CRC, CRC cell lines, their secretomes and subcellular fractions, CRC tumors, CRC patient plasma/serum, and stool samples. For biomarker discovery these approaches are uncovering proteins with potential diagnostic and prognostic utility, while in vitro cell culture experiments are characterizing proteomic and phosphoproteomic responses to disrupted signaling pathways due to mutations or to inhibition of drugable enzymes.  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