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   409202篇
  免费   5149篇
  国内免费   1632篇
电工技术   8009篇
技术理论   1篇
综合类   571篇
化学工业   60613篇
金属工艺   16780篇
机械仪表   13748篇
建筑科学   8562篇
矿业工程   2263篇
能源动力   11725篇
轻工业   28758篇
水利工程   4317篇
石油天然气   8036篇
武器工业   69篇
无线电   50354篇
一般工业技术   83710篇
冶金工业   75259篇
原子能技术   9241篇
自动化技术   33967篇
  2022年   2758篇
  2021年   4169篇
  2020年   3109篇
  2019年   3938篇
  2018年   6625篇
  2017年   6647篇
  2016年   7066篇
  2015年   4504篇
  2014年   7351篇
  2013年   20402篇
  2012年   11757篇
  2011年   15599篇
  2010年   12407篇
  2009年   14029篇
  2008年   14358篇
  2007年   14108篇
  2006年   12654篇
  2005年   11318篇
  2004年   10673篇
  2003年   10558篇
  2002年   9993篇
  2001年   9846篇
  2000年   9237篇
  1999年   9602篇
  1998年   24438篇
  1997年   16786篇
  1996年   12880篇
  1995年   9580篇
  1994年   8413篇
  1993年   8449篇
  1992年   6130篇
  1991年   5761篇
  1990年   5727篇
  1989年   5360篇
  1988年   5081篇
  1987年   4456篇
  1986年   4324篇
  1985年   4834篇
  1984年   4443篇
  1983年   4017篇
  1982年   3669篇
  1981年   3740篇
  1980年   3440篇
  1979年   3336篇
  1978年   3343篇
  1977年   3757篇
  1976年   4856篇
  1975年   2857篇
  1974年   2668篇
  1973年   2740篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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   
993.
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   
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.
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   
996.
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   
997.
998.
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   
999.
The total selenium within a wide variety (315 food items) of Greek foods was determined fluorimetrically. Rich selenium sources were the proteinaceous foods such as fish, meat, bread, and spaghetti. Butter, oils, vegetables, and fruits were poor sources. The selenium content of Greek foods was lower than that of many other countries and resembled more closely that of British foods. From available food consumption data and values in this study, it was estimated that the daily selenium intake of Greeks was 110 μg.  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