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   425048篇
  免费   5817篇
  国内免费   1316篇
电工技术   7917篇
综合类   466篇
化学工业   61345篇
金属工艺   16825篇
机械仪表   13360篇
建筑科学   10254篇
矿业工程   2257篇
能源动力   10718篇
轻工业   36604篇
水利工程   4493篇
石油天然气   7351篇
武器工业   75篇
无线电   52803篇
一般工业技术   83035篇
冶金工业   78661篇
原子能技术   9389篇
自动化技术   36628篇
  2021年   3358篇
  2019年   3347篇
  2018年   5553篇
  2017年   5707篇
  2016年   5995篇
  2015年   3838篇
  2014年   6560篇
  2013年   18839篇
  2012年   10730篇
  2011年   14695篇
  2010年   11688篇
  2009年   13136篇
  2008年   13906篇
  2007年   13928篇
  2006年   12318篇
  2005年   11389篇
  2004年   10972篇
  2003年   10745篇
  2002年   10083篇
  2001年   10229篇
  2000年   9859篇
  1999年   10098篇
  1998年   23751篇
  1997年   17112篇
  1996年   13474篇
  1995年   10271篇
  1994年   9231篇
  1993年   9005篇
  1992年   7098篇
  1991年   6693篇
  1990年   6385篇
  1989年   6216篇
  1988年   5944篇
  1987年   5207篇
  1986年   5022篇
  1985年   5905篇
  1984年   5488篇
  1983年   5023篇
  1982年   4624篇
  1981年   4830篇
  1980年   4444篇
  1979年   4437篇
  1978年   4260篇
  1977年   4962篇
  1976年   6379篇
  1975年   3863篇
  1974年   3814篇
  1973年   3826篇
  1972年   3056篇
  1971年   2855篇
排序方式: 共有10000条查询结果,搜索用时 707 毫秒
41.
To overcome the drawbacks of solid microporous materials for CO2 capture, this proof‐of‐concept study demonstrates a low‐cost and rapid method for producing composites consisting of hypercrosslinked polymers (HCP) with a polyethyleneimine (PEI) binder. The resulting materials capture CO2 through physical and chemical absorption simultaneously. Compared with HCP, the composites exhibit higher CO2 uptake, higher volumetric density, and improved tolerance to water which is attributed to the PEI binder.  相似文献   
42.
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   
43.
Potato processing industry has a high degree of discarding, which currently has low added value being used primarily for animal feed. However, potato wastes offer a broad range of interesting components such as antioxidants, starch, protein or fibre with potential applications in the food and non-food industries. The recovery of these high valuable fractions using efficient multistage and multiproduct processes could be of great interest. This short review provides a general overview on the integral valorisation of potato wastes, offering an updated vision of the main residual parts generated during potato harvesting and processing, the high valuable obtained components focusing on the bioactive ones and the potential of the emerging extraction techniques over conventional ones. In addition, innovative applications are discussed to highlight the scientific and applied interest of these underutilised and undervalued fractions and to emphasise the integral valorisation of raw materials.  相似文献   
44.
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   
45.
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the...  相似文献   
46.
A method is proposed to generate categorical colour observer functions (individual colour matching functions) for any field size based on the CIE 2006 system of physiological observer functions. The method combines proposed categorical observer techniques of Sarkar et al with a physiologically-based individual observer model of Asano et al and a clustering technique to produce the optimal set of categorical observers. The number of required categorical observers varies depending on an application with as many as 50 required to predict individual observers' matches when a laser projector is viewed. However, 10 categorical observers are sufficient to represent colour-normal populations for personalized colour imaging. The proposed and recommended categorical observers represent a robust and inclusive technique to examine and quantify observer metamerism in any application of colorimetry.  相似文献   
47.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  相似文献   
48.
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   
49.
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   
50.
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