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   590850篇
  免费   6777篇
  国内免费   1727篇
电工技术   10869篇
综合类   544篇
化学工业   90407篇
金属工艺   23444篇
机械仪表   18786篇
建筑科学   12973篇
矿业工程   3246篇
能源动力   15608篇
轻工业   48464篇
水利工程   6134篇
石油天然气   11451篇
武器工业   45篇
无线电   67559篇
一般工业技术   116233篇
冶金工业   111992篇
原子能技术   13293篇
自动化技术   48306篇
  2021年   5309篇
  2020年   3969篇
  2019年   5154篇
  2018年   8759篇
  2017年   8758篇
  2016年   9372篇
  2015年   5918篇
  2014年   9884篇
  2013年   27934篇
  2012年   15804篇
  2011年   21453篇
  2010年   17064篇
  2009年   19120篇
  2008年   19760篇
  2007年   19608篇
  2006年   17598篇
  2005年   15634篇
  2004年   14834篇
  2003年   14619篇
  2002年   14196篇
  2001年   13934篇
  2000年   13194篇
  1999年   13625篇
  1998年   34230篇
  1997年   23721篇
  1996年   18284篇
  1995年   13803篇
  1994年   12110篇
  1993年   12099篇
  1992年   8971篇
  1991年   8359篇
  1990年   8498篇
  1989年   8050篇
  1988年   7711篇
  1987年   6758篇
  1986年   6695篇
  1985年   7609篇
  1984年   7071篇
  1983年   6386篇
  1982年   5912篇
  1981年   6062篇
  1980年   5714篇
  1979年   5520篇
  1978年   5539篇
  1977年   6237篇
  1976年   8114篇
  1975年   4796篇
  1974年   4512篇
  1973年   4667篇
  1972年   3922篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The aqueous solution behaviour of malto oligosaccharides, amylose and amylopectin is discussed. Experimental studies, using biophysical methods, on the aggregation behaviour of these compounds are reviewed.  相似文献   
992.
During the last decade, a substantial amount of progress has been made in the understanding of the relationship between the dietary constituents and the development of colon cancer in man. The information base is sufficiently convincing with respect to an enhancing effect as a function of total fat intake and a protective effect of certain dietary fibers in colon cancer. The populations with high incidence of colon cancer are characterized by consumption of high-dietary fat which may be a risk factor in the absence of factors that are protective, such as use of whole-grain cereals, high fibrous foods and vegetables mainly of cruciferous type. Application of the findings made thus far in colon cancer research for the general public is, therefore, to have a far-reaching impact on the major premature, killing diseases in the western world.  相似文献   
993.
994.
New spectrophotometric methods for the assay of some antioxidants have been developed using potassium permanganate and metol (p-N-methyl amino phenol). Metol is oxidised at pH 3.0 with potassium permanganate and coupled with antioxidants to give λmax at 560 nm for propyl gallate and gallic acid and 510nm for butylated hydroxy anisole. The method is simple, sensitive, reproducible and accurate within ±1% and applicable to the assay of antioxidants (gallic acid, propyl gallate and butylated hydroxy anisole) in oils and fats.  相似文献   
995.
A method of calculating the temperature resistance coefficient and its temperature dependence for resistive materials in the approximation of a matrix-statistical structure is outlined.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 477–481, September, 1985.  相似文献   
996.
In order to investigate the galvanic anodic protection (GAP) of ferrous metals (such as 410, 304 and 316 stainless steels) in acid solutions by doped polyaniline (PANi), separate doped PANi powder-pressed electrodes with different surface areas (the area ratio of the PANi electrode to stainless steel is between 1:1 and 1:2) have been prepared. These were coupled with ferrous metal in the following solutions: 5 M sulphuric acid, 5 M phosphoric acid and industrial phosphoric acid (containing 5 M phosphoric acid and 0.05% chloride ion) to construct a galvanic cell, in which PANi is cathode while ferrous metal is anode. The results indicate that a PANi electrode with sufficient area can provide corrosion protection to stainless steel in these acidic solutions. A pilot scale coupling experiment was carried out. The results indicate that PANi is a promising material as an electrode for the anodic protection of ferrous metals in acidic solutions in industrial situations.  相似文献   
997.
In the paper, the problem of existence of the minimal involutive monomial basis is considered for different involutive divisions. The existence criterion is obtained in the form of a constructivity property. In the paper, new examples of constructive and nonconstructive (> σ)-divisions are presented.  相似文献   
998.
999.
Environmentally enhanced crack growth data for 33% Na2O-67% SiO2 and 33% Li2O-67% SiO2 (mol%) were obtained. Corrosion data for the same glasses as determined by infrared reflection spectroscopy and atomic absorption spectroscopy were also measured. It was determined that, of the tested environments, those and only those environments which caused surface corrosion also enhanced crack growth. Crack growth curves were more complicated for these materials than for fused silica. Water-dominated regions occurred even in environments which are known to enhance crack growth.  相似文献   
1000.
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