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   1528209篇
  免费   27611篇
  国内免费   7038篇
电工技术   34645篇
综合类   6566篇
化学工业   272338篇
金属工艺   64653篇
机械仪表   43662篇
建筑科学   46582篇
矿业工程   11572篇
能源动力   50461篇
轻工业   115982篇
水利工程   15521篇
石油天然气   37720篇
武器工业   190篇
无线电   197661篇
一般工业技术   288781篇
冶金工业   171549篇
原子能技术   34049篇
自动化技术   170926篇
  2021年   15736篇
  2020年   12015篇
  2019年   14760篇
  2018年   16490篇
  2017年   15980篇
  2016年   21748篇
  2015年   17509篇
  2014年   28846篇
  2013年   88039篇
  2012年   36180篇
  2011年   49224篇
  2010年   43305篇
  2009年   51399篇
  2008年   45662篇
  2007年   42963篇
  2006年   45275篇
  2005年   40135篇
  2004年   42061篇
  2003年   41920篇
  2002年   40803篇
  2001年   37808篇
  2000年   36203篇
  1999年   35366篇
  1998年   47249篇
  1997年   40673篇
  1996年   36346篇
  1995年   31331篇
  1994年   29359篇
  1993年   29179篇
  1992年   26495篇
  1991年   23607篇
  1990年   23864篇
  1989年   22874篇
  1988年   21479篇
  1987年   19785篇
  1986年   19153篇
  1985年   22456篇
  1984年   22505篇
  1983年   20465篇
  1982年   19354篇
  1981年   19479篇
  1980年   18089篇
  1979年   18666篇
  1978年   17860篇
  1977年   17754篇
  1976年   19024篇
  1975年   16124篇
  1974年   15646篇
  1973年   15702篇
  1972年   13142篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
901.
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   
902.
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   
903.
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   
904.
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   
905.
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   
906.
Clean Technologies and Environmental Policy - Manufacturing organizations are under continuous pressure to implement sustainability in their activities. There is a need to identify the...  相似文献   
907.
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   
908.
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   
909.
910.
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