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   270956篇
  免费   2810篇
  国内免费   660篇
电工技术   5076篇
综合类   231篇
化学工业   37871篇
金属工艺   14472篇
机械仪表   11449篇
建筑科学   6191篇
矿业工程   2015篇
能源动力   5745篇
轻工业   18246篇
水利工程   3323篇
石油天然气   5364篇
武器工业   8篇
无线电   29810篇
一般工业技术   58690篇
冶金工业   42800篇
原子能技术   6061篇
自动化技术   27074篇
  2021年   1606篇
  2019年   1572篇
  2018年   10864篇
  2017年   11457篇
  2016年   7394篇
  2015年   2323篇
  2014年   3164篇
  2013年   8996篇
  2012年   7615篇
  2011年   15117篇
  2010年   13354篇
  2009年   12980篇
  2008年   12816篇
  2007年   14858篇
  2006年   5661篇
  2005年   8725篇
  2004年   6939篇
  2003年   6505篇
  2002年   5176篇
  2001年   4731篇
  2000年   4724篇
  1999年   4756篇
  1998年   11404篇
  1997年   8137篇
  1996年   6430篇
  1995年   4692篇
  1994年   4309篇
  1993年   4108篇
  1992年   3239篇
  1991年   3103篇
  1990年   2872篇
  1989年   2957篇
  1988年   2834篇
  1987年   2400篇
  1986年   2309篇
  1985年   2716篇
  1984年   2507篇
  1983年   2345篇
  1982年   2091篇
  1981年   2205篇
  1980年   2032篇
  1979年   2124篇
  1978年   2121篇
  1977年   2368篇
  1976年   3192篇
  1975年   1834篇
  1974年   1761篇
  1973年   1776篇
  1972年   1446篇
  1971年   1340篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
11.
Chronic stress is a combination of nonspecific adaptive reactions of the body to the influence of various adverse stress factors which disrupt its homeostasis, and it is also a corresponding state of the organism’s nervous system (or the body in general). We hypothesized that chronic stress may be one of the causes occurence of several molecular and cellular types of stress. We analyzed literary sources and considered most of these types of stress in our review article. We examined genes and mutations of nuclear and mitochondrial genomes and also molecular variants which lead to various types of stress. The end result of chronic stress can be metabolic disturbance in humans and animals, leading to accumulation of reactive oxygen species (ROS), oxidative stress, energy deficiency in cells (due to a decrease in ATP synthesis) and mitochondrial dysfunction. These changes can last for the lifetime and lead to severe pathologies, including neurodegenerative diseases and atherosclerosis. The analysis of literature allowed us to conclude that under the influence of chronic stress, metabolism in the human body can be disrupted, mutations of the mitochondrial and nuclear genome and dysfunction of cells and their compartments can occur. As a result of these processes, oxidative, genotoxic, and cellular stress can occur. Therefore, chronic stress can be one of the causes forthe occurrence and development of neurodegenerative diseases and atherosclerosis. In particular, chronic stress can play a large role in the occurrence and development of oxidative, genotoxic, and cellular types of stress.  相似文献   
12.
Journal of Machinery Manufacture and Reliability - The problem of calculating the reliability and fatigue life of machine parts by the fatigue failure under random changes in the actual and limit...  相似文献   
13.
14.
15.
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   
16.
Topics in Catalysis - In this work, a simple thermal-catalytic system was used to valorize peanut shells (Arachis hypogaea), the residual biomass from the peanut industry. To accomplish this...  相似文献   
17.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution.  相似文献   
18.
The price of cobalt has increased by some 450% in the past two years, mainly due to increasing demand for lithium–ion batteries. With an official 2017 production of 64 kt, the Democratic Republic of Congo produces more than half of the world’s cobalt. African Copperbelt operations have traditionally focused on copper production; however, it has now become imperative to also consider cobalt recovery from these ores. A plethora of processing routes is possible. Most hydrometallurgical flowsheets recover cobalt from the raffinate of the low-grade copper solvent-extraction circuit. Downstream purification processes include sequential precipitation with a variety of reagents, solvent extraction, and ion exchange. Product choices include hydroxide, carbonate, sulfate, and metal cathode. This study assesses technical and economic advantages and limitations of various approaches to the hydrometallurgical processing of cobalt in an African context.  相似文献   
19.
Multidimensional Systems and Signal Processing - The paper is devoted to the development of the octonion Fourier transform (OFT) theory initiated in 2011 in articles by Hahn and Snopek. It is also...  相似文献   
20.
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