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   312320篇
  免费   4918篇
  国内免费   1340篇
电工技术   5596篇
综合类   1291篇
化学工业   47916篇
金属工艺   11074篇
机械仪表   9793篇
建筑科学   8971篇
矿业工程   1238篇
能源动力   8053篇
轻工业   31436篇
水利工程   2907篇
石油天然气   3209篇
武器工业   19篇
无线电   40594篇
一般工业技术   56993篇
冶金工业   54234篇
原子能技术   3974篇
自动化技术   31280篇
  2022年   4400篇
  2021年   5883篇
  2020年   4452篇
  2019年   5573篇
  2018年   3961篇
  2017年   3543篇
  2016年   3556篇
  2015年   2747篇
  2014年   4372篇
  2013年   13640篇
  2012年   7861篇
  2011年   11943篇
  2010年   9258篇
  2009年   10358篇
  2008年   10269篇
  2007年   10361篇
  2006年   9660篇
  2005年   8960篇
  2004年   9713篇
  2003年   9421篇
  2002年   9046篇
  2001年   8897篇
  2000年   7619篇
  1999年   7880篇
  1998年   17437篇
  1997年   12296篇
  1996年   9339篇
  1995年   7250篇
  1994年   6514篇
  1993年   6241篇
  1992年   4649篇
  1991年   4252篇
  1990年   4074篇
  1989年   3980篇
  1988年   3809篇
  1987年   3024篇
  1986年   3046篇
  1985年   3680篇
  1984年   3226篇
  1983年   3079篇
  1982年   2798篇
  1981年   2779篇
  1980年   2554篇
  1979年   2378篇
  1978年   2290篇
  1977年   2637篇
  1976年   3094篇
  1975年   1944篇
  1974年   1793篇
  1973年   1798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.
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.

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   
8.
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