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   229090篇
  免费   17435篇
  国内免费   9134篇
电工技术   12453篇
技术理论   24篇
综合类   14144篇
化学工业   38778篇
金属工艺   13141篇
机械仪表   14515篇
建筑科学   17561篇
矿业工程   7499篇
能源动力   6420篇
轻工业   13440篇
水利工程   3585篇
石油天然气   16616篇
武器工业   1647篇
无线电   25121篇
一般工业技术   27326篇
冶金工业   13075篇
原子能技术   2247篇
自动化技术   28067篇
  2024年   993篇
  2023年   3800篇
  2022年   6477篇
  2021年   9100篇
  2020年   7077篇
  2019年   6012篇
  2018年   6728篇
  2017年   7535篇
  2016年   6746篇
  2015年   8855篇
  2014年   11243篇
  2013年   13266篇
  2012年   14203篇
  2011年   15441篇
  2010年   13414篇
  2009年   12678篇
  2008年   12342篇
  2007年   11844篇
  2006年   12338篇
  2005年   10745篇
  2004年   7258篇
  2003年   6224篇
  2002年   5460篇
  2001年   4884篇
  2000年   5431篇
  1999年   6447篇
  1998年   5522篇
  1997年   4500篇
  1996年   4217篇
  1995年   3515篇
  1994年   2824篇
  1993年   1975篇
  1992年   1538篇
  1991年   1226篇
  1990年   933篇
  1989年   740篇
  1988年   540篇
  1987年   339篇
  1986年   284篇
  1985年   197篇
  1984年   139篇
  1983年   115篇
  1982年   124篇
  1981年   100篇
  1980年   73篇
  1979年   36篇
  1978年   28篇
  1977年   29篇
  1976年   53篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
A distributed problem solving system can be characterized as a group of individual cooperating agents running to solve common problems. As dynamic application domains continue to grow in scale and complexity, it becomes more difficult to control the purposeful behavior of agents, especially when unexpected events may occur. This article presents an information and knowledge exchange framework to support distributed problem solving. From the application viewpoint the article concentrates on the stock trading domain; however, many presented solutions can be extended to other dynamic domains. It addresses two important issues: how individual agents should be interconnected so that their resources are efficiently used and their goals accomplished effectively; and how information and knowledge transfer should take place among the agents to allow them to respond successfully to user requests and unexpected external situations. The article introduces an architecture, the MASST system architecture, which supports dynamic information and knowledge exchange among the cooperating agents. The architecture uses a dynamic blackboard as an interagent communication paradigm to facilitate factual data, business rule, and command exchange between cooperating MASST agents. The critical components of the MASST architecture have been implemented and tested in the stock trading domain, and have proven to be a viable solution for distributed problem solving based on cooperating agents  相似文献   
12.
13.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。  相似文献   
14.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。  相似文献   
15.
16.
介绍了子午轮胎硫化的各种介质性能要求及介质供应工艺流程,分析了各种介质的质量要求.介绍了系统各参数的控制调节项目及运行技术管理的一些措施.  相似文献   
17.
介绍并分析了春光油田现代油藏经营管理模式的构建与运作及实施效果.  相似文献   
18.
Previous work has shown that the enzymatic hydrolysis of sugarcane bagasse could be greatly enhanced by peracetic acid (PAA) pretreatment. There are several factors affecting the enzymatic digestibility of the biomass, including lignin and hemicelluloses content, cellulose crystallinity, acetyl group content, accessible surface area and so on. The objective of this work is to analyze the mechanism of the enhancement of enzymatic digestibility caused by PAA pretreatment. Delignification resulted in an increase of the surface area and reduction of the irreversible absorption of cellulase, which helped to increase the enzymatic digestibility. The Fourier transform infrared (FTIR) spectrum showed that the absorption peaks of aromatic skeletal vibrations were weakened or disappeared after PAA pretreatment. However, the infrared crystallization index (N.O'KI) was increased. X‐ray diffraction (XRD) analysis indicated that the crystallinity of PAA‐treated samples was increased owing to the partial removal of amorphous lignin and hemicelluloses and probable physical change of cellulose. The effect of acetyl group content on enzymatic digestibility is negligible compared with the degree of delignification and crystallinity. The results indicate that enhancement of enzymatic digestibility of sugarcane bagasse by PAA pretreatment is achieved mainly by delignification and an increase in the surface area and exposure of cellulose fibers. Copyright © 2008 Society of Chemical Industry  相似文献   
19.
Oxide films were deposited on different substrates by laser molecular beam epitaxy. Reflection high-energy electron diffraction was performed to in situ investigate the change of growth mode and the lattice relaxation during the growth. An asymmetrical phenomenon was found in the two kinds of strain states, compressive stress and tensile stress of heterostructures with different lattice mismatch. In the case of BaTiO3/SrTiO3 (2.2%), 2D layer-by-layer growth mode without lattice relaxation can be maintained for a longer period for BTO films on STO with compressive stress, comparing to STO films on BTO with tensile stress. When MgO films were deposited on SrTiO3 with a large mismatch of 7.8%, compressive stress leads to rapid lattice relaxation with a very thin wet layer, and 3D strained island were observed. As a comparison, SrTiO3 films on MgO with tensile stress were configured. No RHEED patterns can be observed duo to a large tensile stress.  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