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   3927篇
  免费   338篇
  国内免费   307篇
化学   355篇
晶体学   5篇
力学   321篇
综合类   65篇
数学   2894篇
物理学   932篇
  2024年   4篇
  2023年   30篇
  2022年   68篇
  2021年   97篇
  2020年   77篇
  2019年   83篇
  2018年   73篇
  2017年   91篇
  2016年   117篇
  2015年   65篇
  2014年   133篇
  2013年   356篇
  2012年   174篇
  2011年   214篇
  2010年   198篇
  2009年   238篇
  2008年   260篇
  2007年   276篇
  2006年   232篇
  2005年   204篇
  2004年   159篇
  2003年   197篇
  2002年   169篇
  2001年   129篇
  2000年   120篇
  1999年   109篇
  1998年   119篇
  1997年   101篇
  1996年   70篇
  1995年   53篇
  1994年   39篇
  1993年   41篇
  1992年   28篇
  1991年   21篇
  1990年   25篇
  1989年   20篇
  1988年   28篇
  1987年   23篇
  1986年   15篇
  1985年   25篇
  1984年   14篇
  1983年   9篇
  1982年   17篇
  1981年   9篇
  1980年   6篇
  1979年   5篇
  1978年   6篇
  1977年   4篇
  1976年   9篇
  1973年   5篇
排序方式: 共有4572条查询结果,搜索用时 31 毫秒
841.
Peter Poelt 《Mikrochimica acta》2000,132(2-4):129-135
 Use of the L-lines in connection with the elements of the first transition series entails a lot of problems. The corresponding X-ray peaks are composed of contributions of a group of several lines. Because of the incompletely filled 3d-shells, the intensity ratios of the lines and thus the overall peak shapes of the X-ray peaks vary with the type of bonding of the respective element. A special problem posed is that of high energy satellites, which could be strongly absorbed even by use of low electron energies. Crucial for reliable quantitative results is a careful choice of reference spectra for peak deconvolution and peak fit. Nevertheless, with appropriate care results with an accuracy of around 10–15 wt% relative may be obtained. This has been tested by performing quantitative analysis on a haematite and magnetite specimen by use of the Fe-L lines.  相似文献   
842.
金铁英 《数学杂志》2000,20(4):469-472
本文研究了一类多分子生化反应模型Dx=δ-ax-x^py^p,Dy=x^py^p-by当a≠0,p=3,q=2的情形,得出了不存在闭轨的参数区域;至少分支出两个极限环的参数区域以及极限的唯一性的参数区域的一些结果。  相似文献   
843.
混沌时序相空间重构的分析和应用研究   总被引:7,自引:1,他引:6  
在国内外学者工作的基出上,应用Legendere坐标法重构动力系统的相空间,研究了时序时隔τ的取值范围,讨论了时序间隔τ对相空间重构工作的影响,并用所提方法重构了系统的吸引子.算例表明所提方法是有效的.  相似文献   
844.
半平面上的无限级随机Dirichlet级数的值分布   总被引:14,自引:4,他引:10  
本文通过 Dirichlet级数增长性研究结果改进 ,以及对独立随机变量列 { Zn} ,在条件 EZn=0 , 正数α>0 ,使得 ,0 相似文献   
845.
Based on a continuity property of the Hadamard product of power series we derive results concerning the rate of convergence of the partial sums of certain polynomial series expansions for Bessel functions. Since these partial sums are easily computable by recursion and since cancellation problems are considerably reduced compared to the corresponding Taylor sections, the expansions may be attractive for numerical purposes. A similar method yields results on series expansions for confluent hypergeometric functions. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
846.

It is shown that the concept of bounded variation in the mean is not a meaningful generalization of ordinary bounded variation. In fact, it is a characterization of functions which differ from functions of bounded variation on a zero set.

  相似文献   

847.
In this paper we have given transformations for the partial mock theta functions of order five and also some identities between these partial mock theta functions analogous to the identities given by Ramanujan.  相似文献   
848.
We consider the development of a competing risks system following a two-stage stopping rule. This stopping procedure takes into account a desired probability of successfully completing an assigned task. Upon termination, the asymptotic properties of the estimator of the system reliability, as well as the stopping time variable, are examined. Moreover, the asymptotic risk associated with the two-stage procedure is presented. This risk is anchored on a loss function that considers losses incurred in not attaining the desired reliability and that of excessive testing.  相似文献   
849.
刘涵  刘丁  邓凌峰 《中国物理》2006,15(6):1196-1200
Support vector machines (SVM) have been widely used in chaotic time series predictions in recent years. In order to enhance the prediction efficiency of this method and implement it in hardware, the sigmoid kernel in SVM is drawn in a more natural way by using the fuzzy logic method proposed in this paper. This method provides easy hardware implementation and straightforward interpretability. Experiments on two typical chaotic time series predictions have been carried out and the obtained results show that the average CPU time can be reduced significantly at the cost of a small decrease in prediction accuracy, which is favourable for the hardware implementation for chaotic time series prediction.  相似文献   
850.
焦小玉  楼森岳 《中国物理 B》2009,18(9):3611-3615
The approximate direct reduction method is applied to the perturbed mKdV equation with weak fourth order dispersion and weak dissipation. The similarity reduction solutions of different orders conform to formal coherence, accounting for infinite series reduction solutions to the original equation and general formulas of similarity reduction equations. Painlevé II type equations, hyperbolic secant and Jacobi elliptic function solutions are obtained for zero-order similarity reduction equations. Higher order similarity reduction equations are linear variable coefficient ordinary differential equations.  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