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   1528590篇
  免费   27822篇
  国内免费   7073篇
电工技术   34700篇
综合类   6530篇
化学工业   266674篇
金属工艺   65339篇
机械仪表   44128篇
建筑科学   46215篇
矿业工程   11616篇
能源动力   50401篇
轻工业   115619篇
水利工程   15512篇
石油天然气   37655篇
武器工业   157篇
无线电   197891篇
一般工业技术   289646篇
冶金工业   176037篇
原子能技术   34302篇
自动化技术   171063篇
  2021年   15465篇
  2020年   11930篇
  2019年   14693篇
  2018年   17002篇
  2017年   16403篇
  2016年   21999篇
  2015年   17566篇
  2014年   28833篇
  2013年   88224篇
  2012年   36398篇
  2011年   49902篇
  2010年   43905篇
  2009年   52158篇
  2008年   46391篇
  2007年   43950篇
  2006年   45425篇
  2005年   40757篇
  2004年   42392篇
  2003年   42104篇
  2002年   41272篇
  2001年   37859篇
  2000年   36206篇
  1999年   35369篇
  1998年   48026篇
  1997年   41254篇
  1996年   36716篇
  1995年   31618篇
  1994年   29434篇
  1993年   29289篇
  1992年   26500篇
  1991年   23184篇
  1990年   23594篇
  1989年   22564篇
  1988年   21108篇
  1987年   19347篇
  1986年   18824篇
  1985年   22152篇
  1984年   22228篇
  1983年   20187篇
  1982年   19154篇
  1981年   19235篇
  1980年   17969篇
  1979年   18426篇
  1978年   17703篇
  1977年   17888篇
  1976年   19430篇
  1975年   15997篇
  1974年   15460篇
  1973年   15576篇
  1972年   13116篇
排序方式: 共有10000条查询结果,搜索用时 932 毫秒
991.
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   
992.
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   
993.
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   
994.
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   
995.
996.
997.
998.
999.
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   
1000.
The partitioning of predominant lipophilic olive bioactives (squalene, β-sitosterol and α-tocopherol) in olive oil processing was studied for the first time using common integrated olive milling plant. 7% of the oil and 5% of the squalene present in the olives was lost in the last pomace. β-sitosterol and α-tocopherol, which are mainly concentrated in the seed of the olive fruit, was recovered in virgin olive oil to a lesser extent (66%, 67%) while 10% were lost in last pomace. Thus, the loss of β-sitosterol and α-tocopherol was higher than that of squalene and oil, due to nonrecovered bound forms. 19% of the α-tocopherol and 21% of the β-sitosterol loss was unaccounted for, which can be attributed to degradation of α-tocopherol and incomplete recovery of sterols from the olive and pomace matrices. This study provides a basis for process development studies.  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