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   43738篇
  免费   14423篇
  国内免费   9篇
电工技术   798篇
综合类   7篇
化学工业   18766篇
金属工艺   386篇
机械仪表   828篇
建筑科学   1910篇
矿业工程   10篇
能源动力   1036篇
轻工业   7893篇
水利工程   323篇
石油天然气   63篇
无线电   7214篇
一般工业技术   12394篇
冶金工业   1158篇
原子能技术   42篇
自动化技术   5342篇
  2024年   22篇
  2023年   111篇
  2022年   378篇
  2021年   649篇
  2020年   1613篇
  2019年   3355篇
  2018年   3321篇
  2017年   3597篇
  2016年   4139篇
  2015年   4139篇
  2014年   4135篇
  2013年   5345篇
  2012年   3045篇
  2011年   2799篇
  2010年   2922篇
  2009年   2772篇
  2008年   2363篇
  2007年   2152篇
  2006年   1829篇
  2005年   1534篇
  2004年   1493篇
  2003年   1433篇
  2002年   1355篇
  2001年   1159篇
  2000年   1116篇
  1999年   512篇
  1998年   150篇
  1997年   136篇
  1996年   91篇
  1995年   57篇
  1994年   57篇
  1993年   59篇
  1992年   50篇
  1991年   36篇
  1990年   24篇
  1989年   20篇
  1988年   19篇
  1987年   19篇
  1986年   15篇
  1985年   13篇
  1984年   13篇
  1983年   19篇
  1982年   16篇
  1981年   10篇
  1980年   10篇
  1979年   19篇
  1978年   7篇
  1977年   9篇
  1976年   11篇
  1973年   4篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
121.
122.
Since the end of the Cold War and due to the needs to produce titanium more cost‐efficient and thus more attractive for its civilian use, the electroslag remelting (ESR) process has become an increasingly important topic of international research programmes, because titanium and titanium aluminides can be chemically refined by ESR in some degree. Using ESR, titanium turnings from machining steps and scrap from foundries can be remelted, refined and provided as secondary titanium for the market at relatively favourable prices. This article investigates the removability of the main impurities out of titanium and titanium‐aluminium alloys by electroslag remelting using the active slag system CaF2‐Ca‐(CaO). Thermochemical and kinetic aspects of the ESR process are considered.  相似文献   
123.
124.
125.
Glyconanoparticles which present carbohydrate and amino groups motifs at their surface were produced. These particles were highly stable and soluble in aqueous solutions. The presence of the carbohydrate groups also allowed the inclusion of more strongly binding groups, without affecting solubility. The binding of a model DNA, plasmid by these nanoparticles was studied by atomic force microscopy, transmission electron microscopy, and gel electrophoresis. Significant differences between the nanoparticles based on their affinities for the DNA were found, with implications for their potential use as nonviral gene delivery agents.  相似文献   
126.
127.
This paper presents an application of digital signal processing to data acquired by the radio imaging method (RIM) that was adopted to measure moisture distribution inside the human body. RIM was originally developed for the mining industry; we are applying the method to a biomedical measurement because of its simplicity, economy, and safety. When a two‐dimensional image was constructed from the measured data, the method provided insufficient resolution because the wavelength of the measurement medium, a weak electromagnetic wave in a VHF band, was longer than human tissues. We built and measured a phantom, a model simulating the human body, consisting of two water tanks representing large internal organs. A digital equalizer was applied to the measured values as a weight function, and images were reconstructed that corresponded to the original shape of the two water tanks. As a result, a two‐dimensional image containing two individual peaks corresponding to the original two small water tanks was constructed. The result suggests the method was applicable to biomedical measurement by the assistance of digital signal processing. This technique may be applicable to home‐based medical care and other situations in which safety, simplicity, and economy are important.  相似文献   
128.
129.
130.
The degree to which real and hypothetical rewards were discounted across delays ranging from 6 hr to 1 year was explored in a within-subjects design. An adjusting-amounts procedure was used to estimate the subjective value of real and hypothetical rewards at each delay. A hyperbolic discounting function provided a significantly better fit to individual participants' preferences than did an exponential function. No significant effect of reward type on degree of hyperbolic discounting or area under the discounting curves was detected. These findings offer some support for the validity of using hypothetical rewards to estimate discounting rates in substance-abusing and other populations, but caution is suggested because this support is gleaned from a failure to detect an effect of reward type. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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