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   1506525篇
  免费   27564篇
  国内免费   6918篇
电工技术   33990篇
综合类   6467篇
化学工业   261650篇
金属工艺   64026篇
机械仪表   42335篇
建筑科学   45948篇
矿业工程   11350篇
能源动力   50110篇
轻工业   115080篇
水利工程   15448篇
石油天然气   36456篇
武器工业   136篇
无线电   195907篇
一般工业技术   287421篇
冶金工业   170489篇
原子能技术   33790篇
自动化技术   170404篇
  2021年   15366篇
  2020年   11829篇
  2019年   14607篇
  2018年   14840篇
  2017年   14035篇
  2016年   21049篇
  2015年   17359篇
  2014年   28765篇
  2013年   87875篇
  2012年   36170篇
  2011年   48466篇
  2010年   42205篇
  2009年   50364篇
  2008年   45360篇
  2007年   42606篇
  2006年   45607篇
  2005年   39885篇
  2004年   42442篇
  2003年   42289篇
  2002年   41341篇
  2001年   38377篇
  2000年   36639篇
  1999年   35624篇
  1998年   46987篇
  1997年   40250篇
  1996年   33867篇
  1995年   31001篇
  1994年   29049篇
  1993年   28592篇
  1992年   26012篇
  1991年   23192篇
  1990年   23500篇
  1989年   22429篇
  1988年   20961篇
  1987年   19285篇
  1986年   18828篇
  1985年   22213篇
  1984年   22344篇
  1983年   20211篇
  1982年   19119篇
  1981年   19165篇
  1980年   17815篇
  1979年   18470篇
  1978年   17677篇
  1977年   17737篇
  1976年   19288篇
  1975年   15883篇
  1974年   15445篇
  1973年   15522篇
  1972年   13084篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
991.
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   
992.
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   
993.
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   
994.
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   
995.
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   
996.
997.
998.
999.
1000.
Itaconate (ITA) is an emerging powerhouse of innate immunity with therapeutic potential that is limited in its ability to be administered in a soluble form. A library of polyester materials that incorporate ITA into polymer backbones resulting in materials with inherent immunoregulatory behavior is developed. Harnessing hydrolytic degradation release from polyester backbones, ITA polymers result in the mechanism specific immunoregulatory properties on macrophage polarization in vitro. In a functional assay, the polymer-released ITA inhibits bacterial growth on acetate. Translation to an in vivo model of biomaterial associated inflammation, intraperitoneal injection of ITA polymers demonstrate a rapid resolution of inflammation in comparison to a control polymer silicone, demonstrating the value of sustained biomimetic presentation of ITA.  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