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   8360篇
  免费   967篇
  国内免费   461篇
电工技术   497篇
综合类   436篇
化学工业   1426篇
金属工艺   494篇
机械仪表   399篇
建筑科学   545篇
矿业工程   260篇
能源动力   270篇
轻工业   758篇
水利工程   179篇
石油天然气   289篇
武器工业   64篇
无线电   1319篇
一般工业技术   1226篇
冶金工业   424篇
原子能技术   81篇
自动化技术   1121篇
  2024年   27篇
  2023年   137篇
  2022年   241篇
  2021年   362篇
  2020年   287篇
  2019年   262篇
  2018年   283篇
  2017年   311篇
  2016年   336篇
  2015年   372篇
  2014年   453篇
  2013年   653篇
  2012年   565篇
  2011年   607篇
  2010年   517篇
  2009年   513篇
  2008年   476篇
  2007年   434篇
  2006年   441篇
  2005年   399篇
  2004年   265篇
  2003年   246篇
  2002年   220篇
  2001年   178篇
  2000年   176篇
  1999年   161篇
  1998年   141篇
  1997年   122篇
  1996年   95篇
  1995年   83篇
  1994年   68篇
  1993年   68篇
  1992年   31篇
  1991年   45篇
  1990年   27篇
  1989年   23篇
  1988年   24篇
  1987年   10篇
  1986年   9篇
  1985年   11篇
  1984年   16篇
  1983年   6篇
  1982年   13篇
  1981年   12篇
  1980年   11篇
  1979年   7篇
  1978年   6篇
  1977年   6篇
  1973年   6篇
  1972年   5篇
排序方式: 共有9788条查询结果,搜索用时 328 毫秒
41.
本文系统的分析了“黑客”对于ASP网站后台的入侵手段,结合我国网站管理员水平及经验参差不齐的现状,给出了简单且有效的ASP网站后台安全解决方案。使大多数编程水平不高的管理员也能杜绝网站后台的安全隐患。  相似文献   
42.
可编程序控制器在催化联锁系统的应用   总被引:3,自引:2,他引:1  
随着工厂自动化程度的提高,对可编程控制器系统的可靠性要求越来越高,特别是炼油厂、化工厂、电站、钢铁厂以及环保项目中,停车将会给工厂带来的昂贵的代价。在这种情况下,冗余控制器能显著降低生产停滞的风险。简单介绍了可编程序控制器的冗余系统,并结合具体实例说明了冗余系统在其应用过程中的安全可靠性。  相似文献   
43.
Glucosamine, which enters the hexosamine pathway downstream of the rate-limiting step, has been routinely used to mimic the insulin resistance caused by high glucose and insulin. We investigated the effect of glucosamine on insulin-stimulated glucose transport in 3T3-L1 adipocytes. The Delta-insulin (insulin-stimulated minus basal) value for 2-deoxyglucose uptake was dramatically inhibited with increasing concentrations of glucosamine with an ED50 of 1.95 mM. Subcellular fractionation experiments demonstrated that reduction in insulin-stimulated 2-deoxyglucose uptake by glucosamine was due to an inhibition of translocation of both Glut 1 and Glut 4 from the low density microsomes (LDM) to the plasma membrane. Analysis of the insulin signaling cascade revealed that glucosamine impaired insulin receptor autophosphorylation, insulin receptor substrate (IRS-1) phosphorylation, IRS-1-associated PI 3-kinase activity in the LDM, and AKT-1 activation by insulin. Measurement of intracellular ATP demonstrated that the effects of glucosamine were highly correlated with its ability to reduce ATP levels. Reduction of intracellular ATP using azide inhibited Glut 1 and Glut 4 translocation from the LDM to the plasma membrane, insulin receptor autophosphorylation, and IRS-1 tyrosine phosphorylation. Additionally, both the reduction in intracellular ATP and the effects on insulin action caused by glucosamine could be prevented by the addition of inosine, which served as an alternative energy source in the medium. We conclude that direct administration of glucosamine can rapidly lower cellular ATP levels and affect insulin action in fat cells by mechanisms independent of increased intracellular UDP-N-acetylhexosamines and that increased metabolism of glucose via the hexosamine pathway may not represent the mechanism of glucose toxicity in fat cells.  相似文献   
44.
Circular groove guide is a kind of waveguide for millimeter waves with low loss, large dimensions, and low dispersion. In this paper, the dominant mode characteristics of it is analysed. The technique that mode macthing method combines with point matching method is used to derive the Nth-order characteristic equation of the guide. The 1st order, 2nd order and 3rd order approximate curves that the normalized cutoff wavelength of circular groove guide varies with c/a are given. The attenuation curves are given at 1mm, 1.5mm and 3mm wavelength. The numerical results are in well agreement with the experimental results published.  相似文献   
45.
BACKGROUND: Although transmission of hepatitis C virus (HCV) through parental exposure is well documented, it is still controversial whether familial clustering of HCV occurs. METHODS: To investigate risk factors for HCV infection, 109 cases and 84 non-infected controls were studied. In addition, 250 family members (104 men, 146 women) of cases and 170 family members of controls (64 men, 106 women) were tested for HCV infection using an anti-HCV antibody, alanine aminotransferase (ALT), and reverse transcribed polymerase chain reaction (RT-PCR). RESULTS: In the case-control analysis, people aged > or =60 were almost three times more likely to be infected by HCV than those aged <40. Risk of HCV infection was most strongly related to a history of blood transfusion (OR = 12.6, 95% CI: 4.3-36.5) followed by a history of jaundice (OR = 4.1, 95% CI: 1.3-12.6). Only one family member of cases and no-one related to the controls had HCV infection. CONCLUSIONS: These results suggest that, in Korea, age and parenteral exposure, such as a blood transfusion, are risk factors for HCV infection and familial clustering of HCV infection, if it occurs, is rare.  相似文献   
46.
Mixed variable optimization using Taguchi's orthogonal arrays   总被引:2,自引:0,他引:2  
Taguchi's orthogonal arrays for robust design are used in this paper in a nontraditional way to solve a mixed continuous-discrete structural optimization problem. The factors of an orthogonal array correspond to the members of a structure and the levels of each factor correspond to the material choices of each member. Based on the number of factors to be studied and the number of levels of each factor, an appropriate orthogonal array is selected for each specific problem. The number of rows of the orthogonal array correspond to the number of experiments (i.e. continuous sizing optimizations) to be conducted. The response of these experiments, which are the weight of the optimal designs corresponding to different material settings, are then used to calculate the mean effect of each factor level. Some possible optimal material settings can then be determined. Three examples are presented in this paper. Analysis using Taguchi's orthogonal arrays was able to isolate several near optimal or optimal designs. The accuracy and efficiency of the proposed method compared to more traditional solution methodologies are also discussed.  相似文献   
47.
Medullary thyroid cancer is a tumor of the thyroid C cells that occurs in sporadic and hereditary clinical settings. Genetic testing of at-risk individuals is available and has been applied to patient management. Plasma calcitonin levels are a sensitive marker for the presence of disease. Surgery offers the best hope for cure and also is an effective modality for managing metastatic and recurrent disease.  相似文献   
48.
49.
Taiwan's successful industrialisation process with significant structural change now spans four decades. This paper analyses the role of small and medium enterprises and the development of secondary import substitution industries in Taiwan in relation to some policy debates. It is argued that market friendly and self-restrained industrial policies were key to the success of Taiwan's fast industrialisation. However, when Taiwan entered a more matured economy in the 1980s, a more liberal industrial policy was introduced.  相似文献   
50.
视频超分辨率(video super-resolution,VSR)的目的是利用多个相邻帧的信息来生成参考帧的高分辨率版本。现有的许多VSR工作都集中在如何有效地对齐相邻帧以更好地融合相邻帧信息,而很少在相邻帧信息融合这一重要步骤上进行研究。针对该问题,提出了基于组反馈融合机制的视频超分辩模型(GFFMVSR)。具体来说,在相邻帧对齐后,将对齐视频序列输入第一重时间注意力模块;然后,将序列分成几个小组,各小组依次通过组内融合模块实现初步融合。不同小组的融合结果经过第二重时间注意力模块;然后,各小组逐组输入反馈融合模块,利用反馈机制反馈融合不同组别的信息,最后将融合结果输出重建。经验证,该模型具有较强的信息融合能力,在客观评价指标和主观视觉效果上都优于现有的模型。  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