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   82826篇
  免费   492篇
  国内免费   383篇
化学   27639篇
晶体学   824篇
力学   6824篇
数学   32382篇
物理学   16032篇
  2023年   42篇
  2022年   136篇
  2021年   193篇
  2020年   142篇
  2019年   154篇
  2018年   10511篇
  2017年   10315篇
  2016年   6245篇
  2015年   1009篇
  2014年   513篇
  2013年   627篇
  2012年   4108篇
  2011年   10845篇
  2010年   5858篇
  2009年   6286篇
  2008年   6912篇
  2007年   8994篇
  2006年   468篇
  2005年   1502篇
  2004年   1696篇
  2003年   2095篇
  2002年   1114篇
  2001年   333篇
  2000年   368篇
  1999年   206篇
  1998年   238篇
  1997年   188篇
  1996年   234篇
  1995年   153篇
  1994年   117篇
  1993年   137篇
  1992年   98篇
  1991年   87篇
  1990年   77篇
  1989年   76篇
  1988年   79篇
  1987年   72篇
  1986年   71篇
  1985年   62篇
  1984年   60篇
  1983年   57篇
  1982年   51篇
  1981年   60篇
  1980年   57篇
  1979年   56篇
  1978年   50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 15 毫秒
21.
22.
Applied Biochemistry and Biotechnology - The human exposure to bisphenol A (BPA) occurs frequently. Once, this compound was one of the highest volume chemicals produced worldwide and used as a...  相似文献   
23.
In this work, we have used the MuMax3 software to simulate devices consisting of a ferromagnetic thin film placed over a heavy metal thin film. The devices are two interconnected partial-disks where a Néel domain wall is formed in the disks junction. In our simulations we investigate devices with disk radius r=50 nm and different distance d between the disks centers (from d=12 nm to d=2R=100 nm). By applying strong sinusoidal external magnetic fields, we find a mechanism able to create, annihilate and even manipulate a skyrmion in each side of the device. This mechanism is discussed in terms of interactions between skyrmion and domain wall. The Néel domain wall formed in the center of the device interacts with the Néel skyrmion, leading to a process of transporting a skyrmion from one disk to the other periodically. Our results have relevance for potential applications in spintronics such as logical devices.  相似文献   
24.
25.
26.
27.
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   
28.
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   
29.
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   
30.
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   
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