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   102343篇
  免费   7768篇
  国内免费   2806篇
电工技术   4193篇
技术理论   4篇
综合类   3703篇
化学工业   18830篇
金属工艺   5361篇
机械仪表   6868篇
建筑科学   5262篇
矿业工程   1774篇
能源动力   3721篇
轻工业   7622篇
水利工程   1430篇
石油天然气   2914篇
武器工业   555篇
无线电   13655篇
一般工业技术   16736篇
冶金工业   6506篇
原子能技术   1429篇
自动化技术   12354篇
  2024年   311篇
  2023年   1508篇
  2022年   2535篇
  2021年   3780篇
  2020年   2826篇
  2019年   2671篇
  2018年   3109篇
  2017年   3213篇
  2016年   3416篇
  2015年   3546篇
  2014年   4914篇
  2013年   6285篇
  2012年   7054篇
  2011年   7794篇
  2010年   6263篇
  2009年   6218篇
  2008年   5943篇
  2007年   5136篇
  2006年   4833篇
  2005年   4092篇
  2004年   3341篇
  2003年   3116篇
  2002年   3017篇
  2001年   2595篇
  2000年   2179篇
  1999年   2067篇
  1998年   2342篇
  1997年   1619篇
  1996年   1396篇
  1995年   1066篇
  1994年   829篇
  1993年   716篇
  1992年   535篇
  1991年   444篇
  1990年   398篇
  1989年   331篇
  1988年   303篇
  1987年   217篇
  1986年   176篇
  1985年   140篇
  1984年   115篇
  1983年   79篇
  1982年   50篇
  1981年   47篇
  1980年   36篇
  1979年   41篇
  1978年   31篇
  1977年   45篇
  1976年   63篇
  1975年   24篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
棋盘格图像在摄像机标定中有非常广泛的应用,对于复杂环境且测量精度要求非常高的场合,会需要特定的且有一定复杂度的算法,但通常情况下,使用这样的标定系统是没有必要的,且会让初次应用的人觉得困难。这里提供一套应用简单,快速,对棋盘格图像具有旋转不变性,良好的鲁棒性,且对非复杂环境具有高精度的标定系统。所有算法均是在前辈们的算法上稍作改变而来,应用效果非常好。  相似文献   
22.
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   
23.
24.
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   
25.
This study was designed to evaluate the acid stability, release property and antimicrobial efficacy of Escherichia coli O157:H7 bacteriophages encapsulated in chitosan–alginate microspheres under the simulated gastrointestinal conditions. The bacteriophages belonging to Myoviridae family were stable at the pH above 4 in trypticase soy broth. The chitosan–alginate microspheres exhibited protective effect on the viability of bacteriophages in the simulated gastric conditions at pH 2.0 and pH 2.5, showing 4.8 and 5.6 log PFU mL‐1, respectively, after 1 h of incubation at 37 °C. The release per cent of bacteriophages from microspheres gradually increased up to 65% in the simulated intestinal condition (pH 7.5) at 37 °C for 6 h. The lytic efficacy of chitosan‐ and alginate‐encapsulated bacteriophages against Ecoli O157:H7 was significantly maintained in the simulated intestinal conditions to 10 h of incubation (1.3 log reduction). The results suggest that the chitosan–alginate microspheres can be used as a reliable delivery system for bacteriophages.  相似文献   
26.
27.
28.
29.
This paper considers a novel distributed iterative learning consensus control algorithm based on neural networks for the control of heterogeneous nonlinear multiagent systems. The system's unknown nonlinear function is approximated by suitable neural networks; the approximation error is countered by a robust term in the control. Two types of control algorithms, both of which utilize distributed learning laws, are provided to achieve consensus. In the provided control algorithms, the desired reference is considered to be an unknown factor and then estimated using the associated learning laws. The consensus convergence is proven by the composite energy function method. A numerical simulation is ultimately presented to demonstrate the efficacy of the proposed control schemes.  相似文献   
30.
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