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   244920篇
  免费   4905篇
  国内免费   770篇
电工技术   4719篇
综合类   184篇
化学工业   37047篇
金属工艺   9544篇
机械仪表   8620篇
建筑科学   5097篇
矿业工程   769篇
能源动力   6689篇
轻工业   18142篇
水利工程   1921篇
石油天然气   2927篇
武器工业   9篇
无线电   34737篇
一般工业技术   47420篇
冶金工业   48964篇
原子能技术   4170篇
自动化技术   19636篇
  2022年   1582篇
  2021年   2706篇
  2020年   1983篇
  2019年   2442篇
  2018年   3529篇
  2017年   3498篇
  2016年   3895篇
  2015年   2763篇
  2014年   4670篇
  2013年   10885篇
  2012年   7644篇
  2011年   9906篇
  2010年   7661篇
  2009年   8595篇
  2008年   8826篇
  2007年   8266篇
  2006年   7539篇
  2005年   6931篇
  2004年   6705篇
  2003年   6502篇
  2002年   6141篇
  2001年   6356篇
  2000年   5839篇
  1999年   6311篇
  1998年   17053篇
  1997年   11220篇
  1996年   8669篇
  1995年   6281篇
  1994年   5428篇
  1993年   5377篇
  1992年   3631篇
  1991年   3516篇
  1990年   3448篇
  1989年   3266篇
  1988年   2968篇
  1987年   2390篇
  1986年   2411篇
  1985年   2707篇
  1984年   2395篇
  1983年   2120篇
  1982年   1935篇
  1981年   2079篇
  1980年   1819篇
  1979年   1681篇
  1978年   1684篇
  1977年   2059篇
  1976年   2760篇
  1975年   1439篇
  1974年   1384篇
  1973年   1333篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
41.
An explicit extraction of the retinal vessel is a standout amongst the most significant errands in the field of medical imaging to analyze both the ophthalmological infections, for example, Glaucoma, Diabetic Retinopathy (DR), Retinopathy of Prematurity (ROP), Age-Related Macular Degeneration (AMD) as well as non retinal sickness such as stroke, hypertension and cardiovascular diseases. The state of the retinal vasculature is a significant indicative element in the field of ophthalmology. Retinal vessel extraction in fundus imaging is a difficult task because of varying size vessels, moderately low distinction, and presence of pathologies such as hemorrhages, microaneurysms etc. Manual vessel extraction is a challenging task due to the complicated nature of the retinal vessel structure, which also needs strong skill set and training. In this paper, a supervised technique for blood vessel extraction in retinal images using Modified Adaboost Extreme Learning Machine (MAD-ELM) is proposed. Firstly, the fundus image preprocessing is done for contrast enhancement and in-homogeneity correction. Then, a set of core features is extracted, and the best features are selected using “minimal Redundancy-maximum Relevance (mRmR).” Later, using MAD-ELM method vessels and non vessels are classified. DRIVE and DR-HAGIS datasets are used for the evaluation of the proposed method. The algorithm’s performance is assessed based on accuracy, sensitivity and specificity. The proposed technique attains accuracy of 0.9619 on the DRIVE database and 0.9519 on DR-HAGIS database, which contains pathological images. Our results show that, in addition to healthy retinal images, the proposed method performs well in extracting blood vessels from pathological images and is therefore comparable with state of the art methods.  相似文献   
42.
Peer-to-Peer Networking and Applications - Recently, as the P2P service environment repeats evolution, its usage in mobile is rapidly increasing. Applications are being developed in various mobile...  相似文献   
43.
44.
45.
46.
47.
48.
49.
Recent studies have shown that lotus (Nelumbo nucifera) leaf has various pharmacological effects. However, there have been no scientific investigations into these leaves as a fermented crude liquid. This study compared the in vitro antioxidant capacity of lotus leaf‐fermented broth (LLFB) with that of 57° Brix sugar broth (SB) as a control over a period of 6 months based on 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity, ferric ion reducing power, superoxide dismutase‐like activity, tyrosinase inhibition and nitrite scavenging activity. The dominant species during fermentation process were Leuconostoc lactis and Saccharomyces cerevisiae for LLFB. A total of thirty‐six metabolites such as alkaloids, fatty acids, organic acids, phenolics, sugar and sugar derivatives, ethyl esters and monoterpenoids differed between SB and LLFB using gas chromatography–mass spectrometry. Meanwhile, nine volatile compounds in LLFB contributed pleasant, slightly sweetish and fruity odour of condiment and sensory evaluation score of 4.06 ± 1.52 in the proportion of 1:9 LLFB/water.  相似文献   
50.
Many e-commerce companies collect users’ personal data for marketing purposes despite privacy concerns. Information-collecting companies often offer a monetary reward to users to alleviate privacy concerns and ease the collection of personal information. This study focused on the negative effects of monetary rewards on both information privacy concerns (IPC) and information disclosure. A survey approach was used to collect data and 370 final responses were analysed using a two-way analysis of variance and a binomial logistic regression model. The results show that monetary rewards increase IPC when an information-collecting company requires sensitive information. Additional results indicate that building trust is a more effective way of collecting personal data. This study identifies how organisations can best execute information-collection activities and contributes additional insights for academia and practitioners.  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