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   253660篇
  免费   3160篇
  国内免费   914篇
电工技术   4767篇
综合类   1229篇
化学工业   38584篇
金属工艺   10513篇
机械仪表   8496篇
建筑科学   6797篇
矿业工程   1992篇
能源动力   5838篇
轻工业   19781篇
水利工程   3004篇
石油天然气   5392篇
武器工业   22篇
无线电   29830篇
一般工业技术   49025篇
冶金工业   43990篇
原子能技术   5594篇
自动化技术   22880篇
  2022年   4182篇
  2021年   5401篇
  2020年   4051篇
  2019年   5094篇
  2018年   3795篇
  2017年   3486篇
  2016年   3313篇
  2015年   2249篇
  2014年   3599篇
  2013年   10338篇
  2012年   5921篇
  2011年   9013篇
  2010年   7104篇
  2009年   8018篇
  2008年   7546篇
  2007年   7625篇
  2006年   6781篇
  2005年   6460篇
  2004年   7264篇
  2003年   6949篇
  2002年   6733篇
  2001年   6382篇
  2000年   5780篇
  1999年   5736篇
  1998年   12327篇
  1997年   9001篇
  1996年   7091篇
  1995年   5291篇
  1994年   5020篇
  1993年   4750篇
  1992年   3814篇
  1991年   3522篇
  1990年   3334篇
  1989年   3522篇
  1988年   3292篇
  1987年   2815篇
  1986年   2824篇
  1985年   3222篇
  1984年   2897篇
  1983年   2789篇
  1982年   2494篇
  1981年   2549篇
  1980年   2304篇
  1979年   2400篇
  1978年   2494篇
  1977年   2736篇
  1976年   3512篇
  1975年   2201篇
  1974年   2035篇
  1973年   1994篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Clean Technologies and Environmental Policy - Food production and consumption is one of the major causes of global environmental degradation. One way to address environmental impacts in the food...  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.

Stability constants and formation enthalpies of supramolecular complexes of crown ethers and their cyclic and acyclic analogues are determined on the basis of experimental data obtained by different physicochemical methods in the terms of a general approach developed and implemented in the ChemEqui software package. The established regularities of variation of stability of complexes are discussed as dependent on the ligand structure, nature of the cation, solvent, and anion. The applicability of the suggested method of determining complexation selectivity is shown for multicomponent equilibria in solutions.

  相似文献   
5.
6.

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   
7.
8.
9.
Food Analytical Methods - The habanero pepper (Capsicum chinense Jacq.) is very aromatic and is the hottest pepper in the world. In this study, a headspace solid-phase microextraction/gas...  相似文献   
10.
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   
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