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   706篇
  免费   62篇
  国内免费   21篇
化学   32篇
晶体学   1篇
力学   11篇
综合类   15篇
数学   463篇
物理学   267篇
  2024年   3篇
  2023年   5篇
  2022年   13篇
  2021年   17篇
  2020年   16篇
  2019年   22篇
  2018年   11篇
  2017年   24篇
  2016年   31篇
  2015年   9篇
  2014年   41篇
  2013年   42篇
  2012年   36篇
  2011年   54篇
  2010年   31篇
  2009年   45篇
  2008年   44篇
  2007年   54篇
  2006年   42篇
  2005年   32篇
  2004年   37篇
  2003年   39篇
  2002年   29篇
  2001年   15篇
  2000年   9篇
  1999年   7篇
  1998年   9篇
  1997年   18篇
  1996年   6篇
  1995年   4篇
  1994年   4篇
  1993年   4篇
  1992年   2篇
  1991年   4篇
  1990年   1篇
  1989年   3篇
  1987年   2篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   2篇
  1981年   5篇
  1980年   4篇
  1979年   1篇
  1978年   1篇
  1977年   2篇
  1976年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有789条查询结果,搜索用时 15 毫秒
101.
采用层次分析法(Analytic Hierarchy Process,AHP),以战时气象资料的及时性、准确性、可用性、全面性、相关性和连续性等6项指标建立战时气象资料质量评估层次结构模型,构造出两两判断矩阵,并以3个气象台提供的不同气象资料为例,通过进行层次单排序及一致性检验、层次总排序及一致性检验,最终得出质量最佳的气象资料.通过气象资料质量的综合评估,为气象台及时、全面地发现组织气象观探测、预报保障、装备性能与维护、信息传输网络等方面的问题,以及为针对问题采取相应的对策提供指导,也为战时气象资料质量的提高程度的评价提供量化依据.  相似文献   
102.
103.
104.
In this paper we investigate the semi-discrete Ablowitz–Kaup–Newell–Segur (sdAKNS) hierarchy, and specifically their Lax pairs and infinitely many conservation laws, as well as the corresponding continuum limits. The infinitely many conserved densities derived from the Ablowitz-Ladik spectral problem are trivial, in the sense that all of them are shown to reduce to the first conserved density of the AKNS hierarchy in the continuum limit. We derive new and nontrivial infinitely many conservation laws for the sdAKNS hierarchy, and also the explicit combinatorial relations between the known conservation laws and our new ones. By performing a uniform continuum limit, the new conservation laws of the sdAKNS system are then matched with their counterparts of the continuous AKNS system.  相似文献   
105.
In this paper we obtain the discrete integrable self-dual network hierarchy associated with a discrete spectral problem. On the basis of the theory of algebraic curves, the continuous flow and discrete flow related to the discrete self-dual network hierarchy are straightened using the Abel-Jacobi coordinates. The meromorphic function and the Baker-Akhiezer function are introduced on the hyperelliptic curve. Quasi-periodic solutions of the discrete self-dual network hierarchy are constructed with the help of the asymptotic properties and the algebra-geometric characters of the meromorphic function, the Baker-Akhiezer function and the hyperelliptic curve.  相似文献   
106.
In this paper, the compatibility between the gauge transformations and the additional symmetry of the constrained discrete Kadomtsev-Petviashvili hierarchy is given, which preserves the form of the additional symmetry of the cdKP hierarchy, up to shifting of the corresponding additional flows by ordinary time flows.  相似文献   
107.
The authors give finite dimensional exponential solutions of the bigraded Toda hierarchy (BTH). As a specific example of exponential solutions of the BTH, the authors consider a regular solution for the (1, 2)-BTH with a 3 × 3-sized Lax matrix, and discuss some geometric structures of the solution from which the difference between the (1, 2)- BTH and the original Toda hierarchy is shown. After this, the authors construct another kind of Lax representation of (N, 1)-BTH which does not use the fractional operator of Lax operator. Then the authors introduce the lattice Miura transformation of (N, 1)-BTH which leads to equations depending on one field, and meanwhile some specific examples which contain the Volterra lattice equation (a useful ecological competition model) are given.  相似文献   
108.
109.
A new multi-component Lie algebra is constructed, and a type of new loop algebra is presented. A (2+1)-dimensional multi-component DLW integrable hierarchy is obtained by using a (2+1)-dimensional zero curvature equation. Furthermore, the loop algebra is expanded into a larger one and a type of integrable coupling system and its corresponding Hamiltonian structure are worked out.  相似文献   
110.
Fajun Yu  Li Li 《Physics letters. A》2008,372(11):1750-1759
This Letter reports on a study of the multicomponent discrete integrable equation hierarchy with variable spectral parameters. An instance of new multicomponent lattice equation is obtained. Correspondingly, a feasible way to construct the integrable couplings is presented. It indicates that the study of integrable couplings using the block matrix-form of Lie algebra is an important and effective method.  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