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   301925篇
  免费   4875篇
  国内免费   1336篇
电工技术   5518篇
综合类   1288篇
化学工业   46128篇
金属工艺   10797篇
机械仪表   9653篇
建筑科学   8422篇
矿业工程   1189篇
能源动力   7766篇
轻工业   30614篇
水利工程   2766篇
石油天然气   3038篇
武器工业   18篇
无线电   40007篇
一般工业技术   55865篇
冶金工业   51164篇
原子能技术   3888篇
自动化技术   30015篇
  2022年   4633篇
  2021年   6049篇
  2020年   4531篇
  2019年   5561篇
  2018年   3962篇
  2017年   3507篇
  2016年   3535篇
  2015年   2761篇
  2014年   4354篇
  2013年   13004篇
  2012年   7707篇
  2011年   11661篇
  2010年   8987篇
  2009年   10036篇
  2008年   9874篇
  2007年   9887篇
  2006年   9253篇
  2005年   8532篇
  2004年   9336篇
  2003年   9061篇
  2002年   8686篇
  2001年   8666篇
  2000年   7412篇
  1999年   7671篇
  1998年   17194篇
  1997年   12085篇
  1996年   9107篇
  1995年   7001篇
  1994年   6296篇
  1993年   6013篇
  1992年   4416篇
  1991年   4084篇
  1990年   3860篇
  1989年   3773篇
  1988年   3616篇
  1987年   2847篇
  1986年   2842篇
  1985年   3467篇
  1984年   2997篇
  1983年   2847篇
  1982年   2619篇
  1981年   2585篇
  1980年   2339篇
  1979年   2169篇
  1978年   2109篇
  1977年   2448篇
  1976年   2950篇
  1975年   1797篇
  1974年   1658篇
  1973年   1653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.
5.

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   
6.
7.
8.

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   
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