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   1585576篇
  免费   37083篇
  国内免费   6997篇
电工技术   35750篇
综合类   6441篇
化学工业   284157篇
金属工艺   66031篇
机械仪表   46319篇
建筑科学   48798篇
矿业工程   11856篇
能源动力   51111篇
轻工业   124757篇
水利工程   16077篇
石油天然气   38392篇
武器工业   148篇
无线电   203857篇
一般工业技术   302163篇
冶金工业   181794篇
原子能技术   34634篇
自动化技术   177371篇
  2021年   15967篇
  2020年   13203篇
  2019年   17227篇
  2018年   21086篇
  2017年   21081篇
  2016年   25635篇
  2015年   20244篇
  2014年   31377篇
  2013年   91920篇
  2012年   39684篇
  2011年   54122篇
  2010年   47345篇
  2009年   55177篇
  2008年   49578篇
  2007年   47153篇
  2006年   47124篇
  2005年   42693篇
  2004年   44011篇
  2003年   43560篇
  2002年   42291篇
  2001年   38606篇
  2000年   37010篇
  1999年   35891篇
  1998年   50245篇
  1997年   42649篇
  1996年   37419篇
  1995年   31977篇
  1994年   29755篇
  1993年   29585篇
  1992年   26471篇
  1991年   23637篇
  1990年   23977篇
  1989年   23068篇
  1988年   21590篇
  1987年   19820篇
  1986年   19183篇
  1985年   22527篇
  1984年   22511篇
  1983年   20492篇
  1982年   19402篇
  1981年   19493篇
  1980年   18123篇
  1979年   18622篇
  1978年   17858篇
  1977年   17870篇
  1976年   19097篇
  1975年   16107篇
  1974年   15377篇
  1973年   15501篇
  1972年   13022篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Multimedia Tools and Applications - Rapid advancement in technology has led to the use of biometric authentication in every field. In particular, from the past few years, iris recognition systems...  相似文献   
992.
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   
993.
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   
994.
995.
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   
996.
997.
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   
998.
999.
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   
1000.
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   
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