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   18923篇
  免费   1916篇
  国内免费   1907篇
化学   1964篇
晶体学   35篇
力学   1292篇
综合类   432篇
数学   15310篇
物理学   3713篇
  2024年   19篇
  2023年   175篇
  2022年   188篇
  2021年   305篇
  2020年   356篇
  2019年   438篇
  2018年   409篇
  2017年   515篇
  2016年   578篇
  2015年   428篇
  2014年   848篇
  2013年   1349篇
  2012年   868篇
  2011年   1036篇
  2010年   969篇
  2009年   1236篇
  2008年   1336篇
  2007年   1419篇
  2006年   1218篇
  2005年   1123篇
  2004年   899篇
  2003年   898篇
  2002年   837篇
  2001年   704篇
  2000年   686篇
  1999年   643篇
  1998年   569篇
  1997年   477篇
  1996年   375篇
  1995年   271篇
  1994年   245篇
  1993年   176篇
  1992年   154篇
  1991年   135篇
  1990年   102篇
  1989年   80篇
  1988年   73篇
  1987年   63篇
  1986年   56篇
  1985年   85篇
  1984年   85篇
  1983年   30篇
  1982年   60篇
  1981年   31篇
  1980年   38篇
  1979年   43篇
  1978年   22篇
  1977年   25篇
  1976年   19篇
  1974年   9篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
1.
2.
探讨了经济增长及金融发展与城乡收入差距之间互动影响,刻画了三者间的逻辑关系,并基于广西1990-2017年的统计数据,运用状态空间模型及卡尔曼滤波算法对三者间动态关系进行了实证分析.结果显示:经济增长对城乡收入差距呈现倒U型曲线形态,而金融发展则显示出具有不断缩小城乡收入差距的趋势.  相似文献   
3.
4.
5.
The purpose of this paper is to describe the oscillatory properties of second‐order Euler‐type half‐linear differential equations with perturbations in both terms. All but one perturbations in each term are considered to be given by finite sums of periodic continuous functions, while coefficients in the last perturbations are considered to be general continuous functions. Since the periodic behavior of the coefficients enables us to solve the oscillation and non‐oscillation of the considered equations, including the so‐called critical case, we determine the oscillatory properties of the equations with the last general perturbations. As the main result, we prove that the studied equations are conditionally oscillatory in the considered very general setting. The novelty of our results is illustrated by many examples, and we give concrete new corollaries as well. Note that the obtained results are new even in the case of linear equations.  相似文献   
6.
7.
In this paper, we study the local linear convergence properties of a versatile class of Primal–Dual splitting methods for minimizing composite non-smooth convex optimization problems. Under the assumption that the non-smooth components of the problem are partly smooth relative to smooth manifolds, we present a unified local convergence analysis framework for these methods. More precisely, in our framework, we first show that (i) the sequences generated by Primal–Dual splitting methods identify a pair of primal and dual smooth manifolds in a finite number of iterations, and then (ii) enter a local linear convergence regime, which is characterized based on the structure of the underlying active smooth manifolds. We also show how our results for Primal–Dual splitting can be specialized to cover existing ones on Forward–Backward splitting and Douglas–Rachford splitting/ADMM (alternating direction methods of multipliers). Moreover, based on these obtained local convergence analysis result, several practical acceleration techniques are discussed. To exemplify the usefulness of the obtained result, we consider several concrete numerical experiments arising from fields including signal/image processing, inverse problems and machine learning. The demonstration not only verifies the local linear convergence behaviour of Primal–Dual splitting methods, but also the insights on how to accelerate them in practice.  相似文献   
8.
《Mathematische Nachrichten》2018,291(8-9):1177-1190
We introduce homogeneous Besov and Triebel–Lizorkin spaces with variable indexes. We show that their study reduces to the study of inhomogeneous variable exponent spaces and homogeneous constant exponent spaces. Corollaries include trace space characterizations and Sobolev embeddings.  相似文献   
9.
In this paper we study the domain of the generator of stable processes, stable-like processes and more general pseudo- and integro-differential operators which naturally arise both in analysis and as infinitesimal generators of Lévy- and Lévy-type (Feller) processes. In particular we obtain conditions on the symbol of the operator ensuring that certain (variable order) Hölder and Hölder–Zygmund spaces are in the domain. We use tools from probability theory to investigate the small-time asymptotics of the generalized moments of a Lévy or Lévy-type process (Xt)t0,
limt0?1t(Exf(Xt)?f(x)),xRd,
for functions f which are not necessarily bounded or differentiable. The pointwise limit exists for fixed xRd if f satisfies a Hölder condition at x. Moreover, we give sufficient conditions which ensure that the limit exists uniformly in the space of continuous functions vanishing at infinity. As an application we prove that the domain of the generator of (Xt)t0 contains certain Hölder spaces of variable order. Our results apply, in particular, to stable-like processes, relativistic stable-like processes, solutions of Lévy-driven SDEs and Lévy processes.  相似文献   
10.
For a general dyadic grid, we give a Calderón–Zygmund type decomposition, which is the principle fact about the multilinear maximal function on the upper half‐spaces. Using the decomposition, we study the boundedness of . We obtain a natural extension to the multilinear setting of Muckenhoupt's weak‐type characterization. We also partially obtain characterizations of Muckenhoupt's strong‐type inequalities with one weight. Assuming the reverse Hölder's condition, we get a multilinear analogue of Sawyer's two weight theorem. Moreover, we also get Hytönen–Pérez type weighted estimates.  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