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   64370篇
  免费   5862篇
  国内免费   2902篇
电工技术   3683篇
技术理论   2篇
综合类   4198篇
化学工业   10666篇
金属工艺   3816篇
机械仪表   4151篇
建筑科学   4737篇
矿业工程   2207篇
能源动力   1724篇
轻工业   4044篇
水利工程   1115篇
石油天然气   3955篇
武器工业   533篇
无线电   7805篇
一般工业技术   7861篇
冶金工业   3064篇
原子能技术   652篇
自动化技术   8921篇
  2024年   236篇
  2023年   1122篇
  2022年   1641篇
  2021年   2579篇
  2020年   1994篇
  2019年   1767篇
  2018年   1945篇
  2017年   2154篇
  2016年   1950篇
  2015年   2558篇
  2014年   3105篇
  2013年   3701篇
  2012年   4169篇
  2011年   4566篇
  2010年   3781篇
  2009年   3612篇
  2008年   3488篇
  2007年   3351篇
  2006年   3730篇
  2005年   3094篇
  2004年   2157篇
  2003年   1826篇
  2002年   1615篇
  2001年   1462篇
  2000年   1581篇
  1999年   1726篇
  1998年   1537篇
  1997年   1285篇
  1996年   1152篇
  1995年   958篇
  1994年   836篇
  1993年   576篇
  1992年   431篇
  1991年   366篇
  1990年   256篇
  1989年   212篇
  1988年   179篇
  1987年   109篇
  1986年   92篇
  1985年   56篇
  1984年   28篇
  1983年   17篇
  1982年   27篇
  1981年   17篇
  1980年   21篇
  1979年   10篇
  1978年   7篇
  1977年   5篇
  1976年   14篇
  1975年   9篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
41.
42.
Incorporating high level of potato flour into wheat flour enhances nutritional values of bread but induces a series of problems that lead to the decline of the bread quality. To overcome the barrier, wheat gluten and carboxymethylcellulose (CMC) were added into potato–wheat composite flour to improve dough machinability and bread quality. The rheological properties, thermo-mechanical properties and microstructures of dough were investigated. The results showed that the interaction between gluten and CMC mitigated the discontinuity of gluten matrix and gluten protein aggregation caused by the addition of potato flour, which yielded a more branched and compact gluten network. The compact three-dimensional viscoelastic structure induced improvements of gas retention capacity and dough stability, making it mimic the machinability properties of wheat flour dough. Bread qualities were apparently improved with the combined use of 4% gluten and 6% CMC, of which specific volume increased by 42.86%, and simultaneously, hardness reduced by 75.93%.  相似文献   
43.
44.
Based on the potential therapeutic value in targeting mitochondria and the fluorophore tracing ability, a fluorescent mitochondria-targeted organic arsenical PDT-PAO-F16 was fabricated, which not only visualized the cellular distribution, but also exerted anti-cancer activity in vitro and in vivo via targeting pyruvate dehydrogenase complex (PDHC) and respiratory chain complexes in mitochondria. In details, PDT-PAO-F16 mainly accumulated into mitochondria within hours and suppressed the activity of PDHC resulting in the inhibition of ATP synthesis and thermogenesis disorder. Moreover, the suppression of respiratory chain complex I and IV accelerated the mitochondrial dysfunction leading to caspase family-dependent apoptosis. In vivo, the acute promyelocytic leukemia was greatly alleviated in the PDT-PAO-F16 treated group in APL mice model. Our results demonstrated the organic arsenical precursor with fluorescence imaging and target-anticancer efficacy is a promising anticancer drug.  相似文献   
45.
This paper addresses a tracking problem for uncertain nonlinear discrete‐time systems in which the uncertainties, including parametric uncertainty and external disturbance, are periodic with known periodicity. Repetitive learning control (RLC) is an effective tool to deal with periodic unknown components. By using the backstepping procedures, an adaptive RLC law with periodic parameter estimation is designed. The overparameterization problem is overcome by postponing the parameter estimation to the last backstepping step, which could not be easily solved in robust adaptive control. It is shown that the proposed adaptive RLC law without overparameterization can guarantee the perfect tracking and boundedness of the states of the whole closed‐loop systems in presence of periodic uncertainties. In addition, the effectiveness of the developed controller is demonstrated by an implementation example on a single‐link flexible‐joint robot. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
46.
使用气-质联用仪测定餐饮废油生物柴油(WCME)和-10号柴油(-10PD)的组成,使用冷滤点试验器和运动黏度试验器测定WCME的低温流动性,同时使用调合、添加低温流动性改进剂的方法改进WCME的低温流动性。实验结果表明,WCME主要由饱和脂肪酸甲酯和不饱和脂肪酸甲酯组成,质量分数分别为27.63%和71.81%;WCME冷滤点为0℃,运动黏度(40℃)为4.41mm2/s;WCME与-10PD调合后,冷滤点降低,其中B20的冷滤点最低,为-13℃,运动黏度随着WCME的体积分数的减少,逐渐接近-10PD的运动黏度。通过添加低温流动性改进剂,WCME,B10,B20的冷滤点分别从0,-8,-13℃降至-4,-26,-25℃。  相似文献   
47.
In this study, in vitro digestion and fermentation of Flammulina velutipes -derived polysaccharides (FVP) were investigated. It was found that FVP mainly consisted of 48.45% glucose, 15.40% mannose, 14.60% xylose, 11.80% fucose and 9.90% galactose. The -human saliva, simulated gastric and small intestinal juices conditions did not break down the FVP. Based on in vitro fermentation tests, FVP modulated the composition of gut microbiota by elevating the amounts of Bifidobacteriaceae and Bacteroidaceae and reducing the numbers of genera Lachnospiraceae and Enterococcaceae. Meanwhile, FVP affected the synthesis of short-chain fatty acids derived from gut microbiota.  相似文献   
48.
49.
50.
Tian  J. Y.  Xu  G.  Hu  H. J.  Zhou  M. X. 《Strength of Materials》2019,51(3):439-449
Strength of Materials - A metallographic method, dilatometry, and X-ray diffraction were applied to investigate the effects of undercooling and holding time on bainitic transformation,...  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