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   218507篇
  免费   3322篇
  国内免费   925篇
电工技术   3905篇
综合类   692篇
化学工业   32428篇
金属工艺   8515篇
机械仪表   6740篇
建筑科学   5627篇
矿业工程   1483篇
能源动力   5652篇
轻工业   19023篇
水利工程   2526篇
石油天然气   4213篇
武器工业   35篇
无线电   25149篇
一般工业技术   42545篇
冶金工业   40516篇
原子能技术   5234篇
自动化技术   18471篇
  2021年   2053篇
  2020年   1421篇
  2019年   1888篇
  2018年   2935篇
  2017年   2982篇
  2016年   3156篇
  2015年   2129篇
  2014年   3571篇
  2013年   9869篇
  2012年   5781篇
  2011年   7909篇
  2010年   6279篇
  2009年   7096篇
  2008年   7183篇
  2007年   7239篇
  2006年   6234篇
  2005年   5787篇
  2004年   5624篇
  2003年   5723篇
  2002年   5656篇
  2001年   5621篇
  2000年   5119篇
  1999年   5197篇
  1998年   12549篇
  1997年   8874篇
  1996年   6979篇
  1995年   5047篇
  1994年   4549篇
  1993年   4388篇
  1992年   3388篇
  1991年   3212篇
  1990年   2996篇
  1989年   3073篇
  1988年   2940篇
  1987年   2491篇
  1986年   2412篇
  1985年   2846篇
  1984年   2586篇
  1983年   2432篇
  1982年   2166篇
  1981年   2294篇
  1980年   2118篇
  1979年   2183篇
  1978年   2166篇
  1977年   2462篇
  1976年   3368篇
  1975年   1880篇
  1974年   1790篇
  1973年   1821篇
  1972年   1473篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
Alcohol-free beer with isotonic properties is getting more popular and its production can be carried out by different production strategies; however, interrupted fermentation is still a challenge. Therefore, the objective of this study was to develop a low-alcohol isotonic beer (<0.5% v/v) by interrupted fermentation. Moreover, the major objective is to compare the developed product to commercial beverages (sports drinks, ‘Pilsen' regular beer, alcohol-free beers and low-alcohol isotonic beer). The beverages were evaluated based on pH, alcohol content (% v/v), total titratable acidity (mEq L−1), osmolality (mOsmol kg−1), bitterness International Bitterness Units, colour European Brewery Convention, total phenolic compounds (mg L−1 gallic acid), reducing and total sugars (%) and Na and K contents (mg L−1). The developed low-alcohol isotonic beer presented characteristics similar to sports drinks, with the advantage of being richer in phenolic compounds and suitable osmolality. Despite salts were added in its formulation, the grades attributed to all beers employed in the sensory evaluation, as well as the purchase intention did not present significant differences.  相似文献   
2.
ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.  相似文献   
3.
4.
5.

To increase the efficiency of designing systems intended for monitoring surface cracks in aluminum structures during their working life, we have analyzed a two-dimensional symmetric problem on uniaxial extension of an Al-polyimide-Cu layered structure with ideal adhesion between layers and a model crack in the aluminum base. The problem has been first solved for a sample with the crack modeled by a zero-thickness notch using the ANSYS engineering simulation program package. It is shown that this setting of the problem can lead to inadequate results as manifested, in particular, by significantly overstated mechanical stresses in aluminum in the region of crack emergence on the surface. In order to eliminate this difficulty, we propose to use the structure with a model defect in the form of a notch of nonzero thickness in the initial unstressed state of the structure. Recommendations for selecting the thickness of a notch used in the model structure are given.

  相似文献   
6.
7.
8.
Sequencing of rice genome has facilitated the understanding of rice evolution and has been utilized extensively for mining of DNA markers to facilitate marker-assisted breeding. Simple sequence repeat (SSR) markers that are tandemly repeated nucleotide sequence motifs flanked by unique sequences are presently the maker of choice in rice improvement due to their abundance, co-dominant inheritance, high levels of allelic diversity, and simple reproducible assay. The current level of genome coverage by SSR markers in rice is sufficient to employ them for genotype identification and marker-assisted selection in breeding for mapping of genes and quantitative trait loci analysis. This review provides comprehensive information on the mapping and applications of SSR markers in investigation of rice cultivars to study their genetic divergence and marker-assisted selection of important agronomic traits.  相似文献   
9.
10.
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