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   83845篇
  免费   949篇
  国内免费   406篇
电工技术   771篇
综合类   2316篇
化学工业   11477篇
金属工艺   4783篇
机械仪表   3022篇
建筑科学   2167篇
矿业工程   562篇
能源动力   1111篇
轻工业   3591篇
水利工程   1269篇
石油天然气   341篇
无线电   9249篇
一般工业技术   16281篇
冶金工业   2662篇
原子能技术   254篇
自动化技术   25344篇
  2022年   16篇
  2021年   17篇
  2020年   8篇
  2019年   8篇
  2018年   14455篇
  2017年   13382篇
  2016年   9960篇
  2015年   601篇
  2014年   225篇
  2013年   202篇
  2012年   3138篇
  2011年   9409篇
  2010年   8276篇
  2009年   5540篇
  2008年   6771篇
  2007年   7787篇
  2006年   117篇
  2005年   1210篇
  2004年   1129篇
  2003年   1171篇
  2002年   538篇
  2001年   103篇
  2000年   180篇
  1999年   65篇
  1998年   66篇
  1997年   37篇
  1996年   52篇
  1995年   18篇
  1994年   22篇
  1993年   16篇
  1992年   16篇
  1991年   24篇
  1988年   9篇
  1969年   24篇
  1968年   43篇
  1967年   34篇
  1966年   43篇
  1965年   45篇
  1964年   11篇
  1963年   28篇
  1962年   22篇
  1961年   18篇
  1960年   30篇
  1959年   35篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
  1949年   6篇
排序方式: 共有10000条查询结果,搜索用时 52 毫秒
81.
82.
83.
84.
Real world applications of a decision model of relationships between goals based on fuzzy relations are presented. In contrast to other approaches the relationships between decision goals or criteria for each decision situation are represented and calculated explicitly. The application fields are decision making for financial services and optimization of production sequences in car manufacturing.  相似文献   
85.
86.
Composition Group Vector Space (CGVS) method for estimating melting and boiling point T m , T b of organic compound has been proposed, and the principle of this method has been elucidated. The models for estimating T m , T b have been established and the numerical values of relative parameters have been presented. The average percentage deviations of T m , T b estimation are 7.53 and 1.58, respectively, which show that the present method demonstrates significant improvement in applicability to predict the above properties, compared to conventional group methods.  相似文献   
87.
88.
This article proposes an approach for investigating the exponential stability of a nonlinear interval dynamical system with the nonlinearity of a quadratic type on the basis of the Lyapunov’s direct method. It also constructs an inner estimate of the attraction domain to the origin for the system under consideration.  相似文献   
89.
Summary  Well-defined water-soluble poly(styrenesulfonate)-b-poly(ethylene glycol)-b- poly(styrenesulfonate) (PSS-b-PEG-b-PSS) triblock copolymers with narrow molecular weight distribution (1.29 < Mw/Mn < 1.36) were synthesized in aqueous solution at 70 oC via reversible addition-fragmentation chain transfer (RAFT) polymerization. The complex formed by the PSS-b-PEG-b-PSS triblock copolymer coordinated with aluminum ion was investigated with turbidimetry, dynamic light scattering (DSL), zeta-potential, and transmission electron microscopy (TEM). The aggregation formation was based on the neutralization of the SO3- groups in the PSS blocks with Al3+ ions. The appearance, size and stability of the PSS-b-PEG-b-PSS/Al3+ aggregates were controlled by varying the PSS block length and degree of neutralization (DN). At DN = 0.33, where the PSS-b-PEG-b-PSS copolymer was completely neutralized with Al3+, the aggregate size increased with increasing PSS block length. The transition from the shrinking coil of small size to the interchain aggregates of large size was found at DN of about 0.33.  相似文献   
90.
DeMIMA: A Multilayered Approach for Design Pattern Identification   总被引:1,自引:0,他引:1  
Design patterns are important in object-oriented programming because they offer design motifs, elegant solutions to recurrent design problems, which improve the quality of software systems. Design motifs facilitate system maintenance by helping to understand design and implementation. However, after implementation, design motifs are spread throughout the source code and are thus not directly available to maintainers. We present DeMIMA, an approach to identify semi-automatically micro-architectures that are similar to design motifs in source code and to ensure the traceability of these micro-architectures between implementation and design. DeMIMA consists of three layers: two layers to recover an abstract model of the source code, including binary class relationships, and a third layer to identify design patterns in the abstract model. We apply DeMIMA to five open-source systems and, on average, we observe 34% precision for the considered 12 design motifs. Through the use of explanation-based constraint programming, DeMIMA ensures 100% recall on the five systems. We also apply DeMIMA on 33 industrial components.  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