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   582885篇
  免费   8161篇
  国内免费   1837篇
电工技术   11549篇
综合类   587篇
化学工业   86081篇
金属工艺   23506篇
机械仪表   20769篇
建筑科学   15889篇
矿业工程   1927篇
能源动力   14421篇
轻工业   54961篇
水利工程   5107篇
石油天然气   3726篇
武器工业   17篇
无线电   74797篇
一般工业技术   113427篇
冶金工业   98843篇
原子能技术   8140篇
自动化技术   59136篇
  2021年   3210篇
  2019年   3059篇
  2018年   12805篇
  2017年   13518篇
  2016年   9468篇
  2015年   4689篇
  2014年   7069篇
  2013年   24083篇
  2012年   14782篇
  2011年   25759篇
  2010年   21336篇
  2009年   22353篇
  2008年   23127篇
  2007年   25373篇
  2006年   15722篇
  2005年   18117篇
  2004年   15947篇
  2003年   15253篇
  2002年   14004篇
  2001年   13723篇
  2000年   12767篇
  1999年   13204篇
  1998年   28865篇
  1997年   21356篇
  1996年   17026篇
  1995年   13480篇
  1994年   12084篇
  1993年   11534篇
  1992年   8992篇
  1991年   8529篇
  1990年   8129篇
  1989年   7697篇
  1988年   7367篇
  1987年   6285篇
  1986年   6211篇
  1985年   7607篇
  1984年   7038篇
  1983年   6270篇
  1982年   5898篇
  1981年   5785篇
  1980年   5399篇
  1979年   5317篇
  1978年   4946篇
  1977年   6039篇
  1976年   7980篇
  1975年   4199篇
  1974年   3963篇
  1973年   3889篇
  1972年   3133篇
  1971年   2728篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015  相似文献   
53.
54.
55.
The diagnosis and treatment of prostate cancer (PCa) is a major health-care concern worldwide. This cancer can manifest itself in many distinct forms and the transition from clinically indolent PCa to the more invasive aggressive form remains poorly understood. It is now universally accepted that glycan expression patterns change with the cellular modifications that accompany the onset of tumorigenesis. The aim of this study was to investigate if differential glycosylation patterns could distinguish between indolent, significant, and aggressive PCa. Whole serum N-glycan profiling was carried out on 117 prostate cancer patients’ serum using our automated, high-throughput analysis platform for glycan-profiling which utilizes ultra-performance liquid chromatography (UPLC) to obtain high resolution separation of N-linked glycans released from the serum glycoproteins. We observed increases in hybrid, oligomannose, and biantennary digalactosylated monosialylated glycans (M5A1G1S1, M8, and A2G2S1), bisecting glycans (A2B, A2(6)BG1) and monoantennary glycans (A1), and decreases in triantennary trigalactosylated trisialylated glycans with and without core fucose (A3G3S3 and FA3G3S3) with PCa progression from indolent through significant and aggressive disease. These changes give us an insight into the disease pathogenesis and identify potential biomarkers for monitoring the PCa progression, however these need further confirmation studies.  相似文献   
56.
57.
58.
59.
60.
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