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   1578187篇
  免费   29630篇
  国内免费   7123篇
电工技术   35069篇
综合类   6627篇
化学工业   280062篇
金属工艺   66219篇
机械仪表   46544篇
建筑科学   47682篇
矿业工程   11516篇
能源动力   51966篇
轻工业   119917篇
水利工程   15666篇
石油天然气   37700篇
武器工业   192篇
无线电   202948篇
一般工业技术   297936篇
冶金工业   185571篇
原子能技术   34528篇
自动化技术   174797篇
  2021年   16819篇
  2020年   12773篇
  2019年   15618篇
  2018年   17827篇
  2017年   17186篇
  2016年   23192篇
  2015年   18460篇
  2014年   30433篇
  2013年   90321篇
  2012年   38999篇
  2011年   52690篇
  2010年   45587篇
  2009年   53520篇
  2008年   48028篇
  2007年   44704篇
  2006年   46805篇
  2005年   41313篇
  2004年   43071篇
  2003年   42988篇
  2002年   41741篇
  2001年   38906篇
  2000年   37110篇
  1999年   36621篇
  1998年   52709篇
  1997年   43610篇
  1996年   38255篇
  1995年   32572篇
  1994年   30378篇
  1993年   30118篇
  1992年   26683篇
  1991年   23929篇
  1990年   24103篇
  1989年   23148篇
  1988年   21698篇
  1987年   19935篇
  1986年   19382篇
  1985年   22570篇
  1984年   22591篇
  1983年   20544篇
  1982年   19445篇
  1981年   19563篇
  1980年   18169篇
  1979年   18690篇
  1978年   17896篇
  1977年   17926篇
  1976年   19474篇
  1975年   16122篇
  1974年   15650篇
  1973年   15717篇
  1972年   13144篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
In optimization of transient problems, a robust, stable, and efficient numerical scheme for time integration is of much importance. Recently, the mixed Lag  相似文献   
972.
Bacterial cellulose membranes were employed as templates for calcium phosphates deposition by successive immersion in solutions of Ca(NO3)2·4H2O and (NH4)2HPO4, under ultrasonication. During the wet chemical reaction, mineral phases were loaded on bacterial cellulose fibrils, leading to precursor hybrid composites. These were subjected to a lyophilisation procedure in order to preserve the 3D porous aspect and afterwards to a thermal treatment with the aim of removing the polymeric phase and generating well crystallized structures. Different types of morphologies were achieved by varying the heating rate, as well as the calcination temperature and period. The as-prepared samples and the final ones were investigated from compositional and structural point of view through X-ray diffraction and Fourier-transform infrared spectroscopy and morphologically concerning by scanning electron microscopy. The magnetic properties were also evaluated in order to demonstrate the suitability of the obtained materials for the development of magnetic scaffolds dedicated to hard tissue applications.  相似文献   
973.
Nahrawy  A. M. El  Moez  A. Abdel  Saad  A. M. 《SILICON》2018,10(5):2117-2122
Silicon - Thin film nanocomposites of sodium silicate (80 SiO2 –20 Na2O)/ tartrazine dye (E102) prepared using sol gel process in acidic system. The change in the physicochemical properties...  相似文献   
974.
975.
ABSTRACT

This paper proposes the multiple-hypotheses image segmentation and feed-forward neural network classifier for food recognition to improve the performance. Initially, the food or meal image is given as input. Then, the segmentation is applied to identify the regions, where a particular food item is located using salient region detection, multi-scale segmentation, and fast rejection. Then, the features of every food item are extracted by the global feature and local feature extraction. After the features are obtained, the classification is performed for each segmented region using a feed-forward neural network model. Finally, the calorie value is computed with the aid of (i) food volume and (ii) calorie and nutrition measure based on mass value. The experimental results and performance evaluation are validated. The outcome of the proposed method attains 0.947 for Macro Average Accuracy (MAA) and 0.959 for Standard Accuracy (SA), which provides better classification performance.  相似文献   
976.
Abdellah  W. M. 《Radiochemistry》2020,62(3):347-358
Radiochemistry - The study deals with separation of uranium, thorium, and yttrium with highest possible purity from El-Garaa El-Hamara sulfate leach liquor. From the latter, almost complete...  相似文献   
977.
The ability of bacterial species to colonize and infect host organisms is critically dependent upon their capacity to adhere to cellular surfaces of the host. Adherence to cell surfaces is known to be essential for the activation and delivery of certain virulence factors, but can also directly affect host cell signaling to aid bacterial spread and survival. In this review we will discuss the recent advances in the field of bacterial adhesion, how we are beginning to unravel the effects adhesins have on host cell signaling, and how these changes aid the bacteria in terms of their survival and evasion of immune responses. Finally, we will highlight how the exploitation of bacterial adhesins may provide new therapeutic avenues for the treatment of a wide range of bacterial infections.  相似文献   
978.
979.
980.
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