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   242462篇
  免费   2877篇
  国内免费   893篇
电工技术   4616篇
综合类   1217篇
化学工业   36173篇
金属工艺   10338篇
机械仪表   8234篇
建筑科学   6227篇
矿业工程   1910篇
能源动力   5511篇
轻工业   18943篇
水利工程   2885篇
石油天然气   5234篇
武器工业   21篇
无线电   29158篇
一般工业技术   47365篇
冶金工业   41388篇
原子能技术   5481篇
自动化技术   21531篇
  2022年   4109篇
  2021年   5284篇
  2020年   3945篇
  2019年   4982篇
  2018年   3657篇
  2017年   3349篇
  2016年   3144篇
  2015年   2112篇
  2014年   3419篇
  2013年   9608篇
  2012年   5539篇
  2011年   8505篇
  2010年   6792篇
  2009年   7662篇
  2008年   7078篇
  2007年   7180篇
  2006年   6322篇
  2005年   6099篇
  2004年   6958篇
  2003年   6654篇
  2002年   6413篇
  2001年   6181篇
  2000年   5603篇
  1999年   5543篇
  1998年   12223篇
  1997年   8854篇
  1996年   6909篇
  1995年   5088篇
  1994年   4828篇
  1993年   4504篇
  1992年   3602篇
  1991年   3363篇
  1990年   3162篇
  1989年   3344篇
  1988年   3156篇
  1987年   2652篇
  1986年   2662篇
  1985年   3022篇
  1984年   2702篇
  1983年   2624篇
  1982年   2333篇
  1981年   2401篇
  1980年   2175篇
  1979年   2243篇
  1978年   2351篇
  1977年   2624篇
  1976年   3401篇
  1975年   2050篇
  1974年   1920篇
  1973年   1869篇
排序方式: 共有10000条查询结果,搜索用时 0 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