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   30926篇
  免费   2814篇
  国内免费   956篇
电工技术   1284篇
综合类   1608篇
化学工业   6692篇
金属工艺   1149篇
机械仪表   1296篇
建筑科学   1717篇
矿业工程   452篇
能源动力   901篇
轻工业   4852篇
水利工程   592篇
石油天然气   775篇
武器工业   136篇
无线电   2506篇
一般工业技术   3762篇
冶金工业   1288篇
原子能技术   265篇
自动化技术   5421篇
  2024年   127篇
  2023年   432篇
  2022年   1154篇
  2021年   1410篇
  2020年   1073篇
  2019年   960篇
  2018年   1071篇
  2017年   1176篇
  2016年   1073篇
  2015年   1376篇
  2014年   1832篇
  2013年   2407篇
  2012年   2540篇
  2011年   2780篇
  2010年   2273篇
  2009年   2226篇
  2008年   2023篇
  2007年   1891篇
  2006年   1497篇
  2005年   1107篇
  2004年   769篇
  2003年   608篇
  2002年   509篇
  2001年   349篇
  2000年   295篇
  1999年   233篇
  1998年   264篇
  1997年   211篇
  1996年   156篇
  1995年   134篇
  1994年   94篇
  1993年   83篇
  1992年   58篇
  1991年   53篇
  1990年   48篇
  1989年   47篇
  1988年   32篇
  1987年   31篇
  1986年   31篇
  1985年   35篇
  1984年   24篇
  1983年   20篇
  1982年   21篇
  1981年   21篇
  1980年   18篇
  1979年   16篇
  1978年   24篇
  1977年   8篇
  1976年   28篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
111.
112.
The martensitic transformation temperatures and the types of martensitic phases have been determined in a wide concentration range of technological interest for Cu-Al-Ni shape-memory alloys (SMAs) A stability diagram of martensitic phases as a function of alloy concentration has been determined. It is found that when the aluminum content increases, the transformation changes from β 3β3 to β 3γ3, with an intermediate concentration range where both martensites coexist due to a β 3γ3+β3 transformation. On the other hand, an increase of nickel content stabilizes the martensite β3, changing from a mixed β 3γ3 + β3 to a single β 3β3 transformation. Furthermore, linear relationships between M s and Al and Ni concentrations have been obtained for all types of martensitic phases.  相似文献   
113.
114.
针对胜索油田二区9-10单元的层间非均质和平面非均质性,运用水动力学方法,采用周期注水及增压注水改善单元的水驱油效果。经过6a的实施,单元的开发形势趋好,单元采收率提高9.62%,增加可采储量341.5kt,对同类型非均质性油藏改善水驱油效果,提高最终采收率具有借鉴意义。  相似文献   
115.
谢喜秋  武娟  彭巍  陈绚 《电信科学》2002,18(7):31-34
本文主要分析了影响宽带接入服务器性能的各种因素,介绍了如何选择宽带接入服务器,并针对REDBACK公司的SMS1800和UNISPHERE公司的ERX1400两种典型宽带接入服务器说明如何进行配置,为应用宽带接入服务器提供参考。  相似文献   
116.
Electronic commerce is an important application that has evolved significantly recently. However, electronic commerce systems are complex and difficult to be correctly designed. Guaranteeing the correctness of an e-commerce system is not an easy task due to the great amount of scenarios where errors occur, many of them very subtle. In this work we presents a methodology that uses formal-method techniques, specifically symbolic model checking, to design electronic commerce applications and to automatically verify them. Also, a model checking pattern hierarchy has been developed—it specifies patterns to construct and verify the formal model of e-commerce systems. We consider this research the first step to the development of a framework, which will integrate the methodology, an e-commerce specification language based on business rules, and a model checker. Adriano Pereira received the B.S. and M.S. degrees in computer science in 2000 and 2002, respectively, and he is currently pursuing the Ph.D. degree in computer science from the Federal University of Minas Gerais, Belo Horizonte, Brazil. His current interests are on performance analysis and modeling of e-business and distributed systems, and formal methods. Mark Song received the B.S., M.S. and Ph.D. degrees in computer science from the Federal University of Minas Gerais, Belo Horizonte, Brazil. His current interests are on distributed systems and formal methods – especially BMC (Bounded Model Checking). Gustavo Franco received the B.S. and M.S. degrees in computer science in 2001 and 2004, respectively, from the Federal University of Minas Gerais, Belo Horizonte, Brazil. His research was on modeling the user behavior of e-business and distributed systems, and formal methods. Actually his current interests are on software engeneering and project management of IT projects.  相似文献   
117.
介绍了本钢不停产安装再造煤气管道鼓形膨胀器的实践,并对制造、安装方法进行了叙述,特别是在结构上采用了独特的构槽密封焊缝和完整的安装程序,保证了实施的安全。  相似文献   
118.
Proper integration of scheduling and control in Flexible Manufacturing Systems will make available the required level of decision-making capacity to provide a flexibly-automated, efficient, and quality manufacturing process. To achieve this level of integration, the developments in computer technology and sophisticated techniques of artificial intelligence (AI) should be applied to such FMS functions as scheduling. In this paper, we present an Intelligent Scheduling System for FMS under development that makes use of the integration of two AI technologies. These two AI technologies — Neural Networks and Expert Systems — provide the intelligence that the scheduling function requires in order to generate goodschedules within the restrictions imposed by real-time problems. Because the system has the ability to plan ahead and learn, it has a higher probability of success than conventional approaches. The adaptive behavior that will be achieved contribute to the integration of scheduling and control in FMS.  相似文献   
119.
The β-hydroxyacyl-CoA-dehydrogenase (HADH) activity of unfrozen and thawed frog legs was investigated. The enzyme was extracted by either immersing frog legs in phosphate buffer 0.1 M, pH 6.0 at 25°C for 15 min or pressing them between trichinoscopy glasses. The enzyme activity was assayed using acetoacetyl-CoA as substrate and measured spectrophotometrically at 340 nm. It was possible by both extraction methods to distinguish between thawed and unfrozen samples although when the juice was obtained by pressing the HADH activity of the dilution was ~ 1.5 times higher than that obtained by immersion. The HADH activity was significantly higher (P≤0·001) in frozen-thawed frogs than in unfrozen legs because during freezing there is a release of HADH. No significative differences were found in the HADH activity in samples frozen in the temperature range -10 to -196°C. HADH activity was not affected by the storage time in crushed ice up to 6 days.  相似文献   
120.
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