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   82540篇
  免费   574篇
  国内免费   425篇
化学   27390篇
晶体学   855篇
力学   6935篇
综合类   1篇
数学   32458篇
物理学   15900篇
  2023年   43篇
  2022年   180篇
  2021年   323篇
  2020年   239篇
  2019年   240篇
  2018年   10575篇
  2017年   10362篇
  2016年   6289篇
  2015年   981篇
  2014年   484篇
  2013年   748篇
  2012年   4057篇
  2011年   10754篇
  2010年   5794篇
  2009年   6176篇
  2008年   6763篇
  2007年   8923篇
  2006年   380篇
  2005年   1415篇
  2004年   1648篇
  2003年   2075篇
  2002年   1134篇
  2001年   302篇
  2000年   329篇
  1999年   188篇
  1998年   223篇
  1997年   167篇
  1996年   230篇
  1995年   148篇
  1994年   111篇
  1993年   121篇
  1992年   87篇
  1991年   98篇
  1990年   77篇
  1989年   105篇
  1988年   98篇
  1987年   85篇
  1986年   88篇
  1985年   74篇
  1984年   77篇
  1983年   62篇
  1982年   59篇
  1981年   58篇
  1980年   68篇
  1979年   62篇
  1978年   57篇
  1914年   45篇
  1912年   40篇
  1909年   41篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 20 毫秒
21.
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form.  相似文献   
22.
23.
24.
25.
26.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  相似文献   
27.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective.  相似文献   
28.
This paper describes three case studies which investigated issues relating to the implementation and management of advanced information technology. The benefits derived from information technology were found to vary from one organization to another. These studies provide further evidence to support earlier research findings that senior management has an important role to play in the effective exploitation of information technology, and that the investment approach taken by an organization has a significant effect on the development of computer-based information systems. The effectiveness of a system depends not only on applying the appropriate technology, but also on how successfully technical and behavioural issues are resolved.  相似文献   
29.
In this paper, an MILP formulation is proposed for the design of a reverse logistics network based on a warehouse location–allocation model, which optimizes, simultaneously, the forward and reverse networks. A single product model with unlimited capacity is first defined. Subsequently, the model is extended to a multi-product capacitated recovery network model, where capacity limitations and a multi-product system can be considered. The proposed model is compared to published work in the field, where different model assumptions have been proposed. Two cases are described so as to gain a better insight into the model and allow a comparative analysis.  相似文献   
30.
Well-Posedness by Perturbations of Variational Problems   总被引:3,自引:0,他引:3  
In this paper, we consider the extension of the notion of well-posedness by perturbations, introduced by Zolezzi for optimization problems, to other related variational problems like inclusion problems and fixed-point problems. Then, we study the conditions under which there is equivalence of the well-posedness in the above sense between different problems. Relations with the so-called diagonal well-posedness are also given. Finally, an application to staircase iteration methods is presented.  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