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   242247篇
  免费   2881篇
  国内免费   900篇
电工技术   4618篇
综合类   1217篇
化学工业   36067篇
金属工艺   10351篇
机械仪表   8228篇
建筑科学   6214篇
矿业工程   1913篇
能源动力   5506篇
轻工业   18886篇
水利工程   2887篇
石油天然气   5235篇
武器工业   21篇
无线电   29195篇
一般工业技术   47335篇
冶金工业   41385篇
原子能技术   5491篇
自动化技术   21479篇
  2022年   4091篇
  2021年   5263篇
  2020年   3932篇
  2019年   4980篇
  2018年   3646篇
  2017年   3339篇
  2016年   3135篇
  2015年   2118篇
  2014年   3406篇
  2013年   9605篇
  2012年   5541篇
  2011年   8480篇
  2010年   6772篇
  2009年   7670篇
  2008年   7057篇
  2007年   7147篇
  2006年   6326篇
  2005年   6068篇
  2004年   6955篇
  2003年   6641篇
  2002年   6437篇
  2001年   6188篇
  2000年   5596篇
  1999年   5542篇
  1998年   12207篇
  1997年   8854篇
  1996年   6904篇
  1995年   5097篇
  1994年   4823篇
  1993年   4504篇
  1992年   3614篇
  1991年   3360篇
  1990年   3167篇
  1989年   3334篇
  1988年   3154篇
  1987年   2639篇
  1986年   2656篇
  1985年   3025篇
  1984年   2708篇
  1983年   2629篇
  1982年   2336篇
  1981年   2388篇
  1980年   2172篇
  1979年   2241篇
  1978年   2335篇
  1977年   2617篇
  1976年   3402篇
  1975年   2045篇
  1974年   1921篇
  1973年   1878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