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   9508篇
  免费   710篇
  国内免费   342篇
化学   2961篇
晶体学   32篇
力学   647篇
综合类   58篇
数学   4661篇
物理学   2201篇
  2024年   9篇
  2023年   155篇
  2022年   136篇
  2021年   273篇
  2020年   387篇
  2019年   335篇
  2018年   342篇
  2017年   384篇
  2016年   338篇
  2015年   305篇
  2014年   548篇
  2013年   1206篇
  2012年   562篇
  2011年   570篇
  2010年   444篇
  2009年   688篇
  2008年   693篇
  2007年   535篇
  2006年   429篇
  2005年   411篇
  2004年   305篇
  2003年   200篇
  2002年   161篇
  2001年   90篇
  2000年   99篇
  1999年   105篇
  1998年   81篇
  1997年   86篇
  1996年   93篇
  1995年   73篇
  1994年   64篇
  1993年   52篇
  1992年   46篇
  1991年   25篇
  1990年   16篇
  1989年   23篇
  1988年   16篇
  1987年   18篇
  1986年   17篇
  1985年   43篇
  1984年   50篇
  1983年   20篇
  1982年   25篇
  1981年   26篇
  1980年   17篇
  1979年   16篇
  1978年   12篇
  1977年   8篇
  1976年   7篇
  1973年   5篇
排序方式: 共有10000条查询结果,搜索用时 109 毫秒
21.
In this paper, we present existence results for a one-dimensional coupled system of nonlinear integro-differential equations on sup is="true">s="true">s="true">Ls="true">s="true">psup><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="2.642ex" height="2.086ex" viewBox="0 -796.9 1137.5 898.2" role="img" focusable="false" style="vertical-align: -0.235ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">s="true">se xlink:href="#MJMATHI-4C">se>s="true" transform="translate(681,410)">s="true">se transform="scale(0.707)" xlink:href="#MJMATHI-70">se>svg><script type="math/mml" id="MathJax-Element-1">sup is="true">s="true">s="true">Ls="true">s="true">psup>script>-spaces with s="true">s="true">1style="after" is="true">≤s="true">pstyle="after" is="true"><s="true">∞<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="10.853ex" height="2.317ex" viewBox="0 -747.2 4672.6 997.6" role="img" focusable="false" style="vertical-align: -0.582ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">se xlink:href="#MJMAIN-31">se>s="true" transform="translate(778,0)">se xlink:href="#MJMAIN-2264">se>s="true" transform="translate(1834,0)">se xlink:href="#MJMATHI-70">se>s="true" transform="translate(2615,0)">se xlink:href="#MJMAIN-3C">se>s="true" transform="translate(3672,0)">se xlink:href="#MJMAIN-221E">se>svg><script type="math/mml" id="MathJax-Element-2">s="true">s="true">1style="after" is="true">≤s="true">pstyle="after" is="true"><s="true">∞script>. This system describes the steady-state combined radiative–conductive heat transfer. We reformulate the full coupled system as a fixed point problem. This formulation is applied to prove existence results for the radiation intensity and the temperature fields. We treat separately the cases s="true">s="true">pstyle="after" is="true">=s="true">1<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="5.52ex" height="2.317ex" viewBox="-38.5 -747.2 2376.6 997.6" role="img" focusable="false" style="vertical-align: -0.582ex; margin-left: -0.089ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">se xlink:href="#MJMATHI-70">se>s="true" transform="translate(781,0)">se xlink:href="#MJMAIN-3D">se>s="true" transform="translate(1837,0)">se xlink:href="#MJMAIN-31">se>svg><script type="math/mml" id="MathJax-Element-3">s="true">s="true">pstyle="after" is="true">=s="true">1script> and s="true">s="true">pstyle="after" is="true">>s="true">1<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="5.52ex" height="2.317ex" viewBox="-38.5 -747.2 2376.6 997.6" role="img" focusable="false" style="vertical-align: -0.582ex; margin-left: -0.089ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">se xlink:href="#MJMATHI-70">se>s="true" transform="translate(781,0)">se xlink:href="#MJMAIN-3E">se>s="true" transform="translate(1837,0)">se xlink:href="#MJMAIN-31">se>svg><script type="math/mml" id="MathJax-Element-4">s="true">s="true">pstyle="after" is="true">>s="true">1script>. The analysis for s="true">s="true">pstyle="after" is="true">>s="true">1<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="5.52ex" height="2.317ex" viewBox="-38.5 -747.2 2376.6 997.6" role="img" focusable="false" style="vertical-align: -0.582ex; margin-left: -0.089ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">se xlink:href="#MJMATHI-70">se>s="true" transform="translate(781,0)">se xlink:href="#MJMAIN-3E">se>s="true" transform="translate(1837,0)">se xlink:href="#MJMAIN-31">se>svg><script type="math/mml" id="MathJax-Element-5">s="true">s="true">pstyle="after" is="true">>s="true">1script> uses the Krasnosel’skii fixed point theorem, while the existence results in the case s="true">s="true">pstyle="after" is="true">=s="true">1<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="5.52ex" height="2.317ex" viewBox="-38.5 -747.2 2376.6 997.6" role="img" focusable="false" style="vertical-align: -0.582ex; margin-left: -0.089ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">se xlink:href="#MJMATHI-70">se>s="true" transform="translate(781,0)">se xlink:href="#MJMAIN-3D">se>s="true" transform="translate(1837,0)">se xlink:href="#MJMAIN-31">se>svg><script type="math/mml" id="MathJax-Element-6">s="true">s="true">pstyle="after" is="true">=s="true">1script> are obtained via a new variant of that theorem for the weak topology established in Latrach et&nbsp;al. (2006).  相似文献   
22.
In this paper, we propose a sufficient and necessary condition for the boundedness of all the solutions for the equation s="true">s="true">s="true">xs="true">s="true">¨s="true">+sup is="true">s="true">s="true">ns="true">s="true">2sup>s="true">xs="true">+s="true">gstretchy="false" is="true">(s="true">xstretchy="false" is="true">)s="true">=s="true">pstretchy="false" is="true">(s="true">tstretchy="false" is="true">) with the critical situation that stretchy="true" maxsize="2.4ex" minsize="2.4ex" is="true">|subsup is="true">s="true">s="true">∫s="true">s="true">0s="true">s="true">2s="true">πsubsup>s="true">pstretchy="false" is="true">(s="true">tstretchy="false" is="true">)sup is="true">s="true">s="true">es="true">s="true">?s="true">is="true">ns="true">tsup>s="true">ds="true">tstretchy="true" maxsize="2.4ex" minsize="2.4ex" is="true">|s="true">=s="true">2stretchy="true" maxsize="2.4ex" minsize="2.4ex" is="true">|s="true">gstretchy="false" is="true">(s="true">+s="true">∞stretchy="false" is="true">)s="true">?s="true">gstretchy="false" is="true">(s="true">?s="true">∞stretchy="false" is="true">)stretchy="true" maxsize="2.4ex" minsize="2.4ex" is="true">| on g and p, where s="true">ns="true">∈sup is="true">s="true">s="true">Ns="true">s="true">+sup>, s="true">pstretchy="false" is="true">(s="true">tstretchy="false" is="true">) is periodic and s="true">gstretchy="false" is="true">(s="true">xstretchy="false" is="true">) is bounded.  相似文献   
23.
This paper deals with the Cauchy–Dirichlet problem for the fractional Cahn–Hilliard equation. The main results consist of global (in time) existence of weak solutions, characterization of parabolic smoothing effects (implying under proper condition eventual boundedness of trajectories), and convergence of each solution to a (single) equilibrium. In particular, to prove the convergence result, a variant of the so-called ?ojasiewicz–Simon inequality is provided for the fractional Dirichlet Laplacian and (possibly) non-analytic (but sup is="true">s="true">s="true">Cs="true">s="true">1sup>) nonlinearities.  相似文献   
24.
In this paper, we study the Heinz type inequalities for mappings satisfying Poisson’s equation. Some results generalize the ones obtained by Partyka and Sakan.  相似文献   
25.
The current response for the parameter change of a mesoscopic system is a practical issue for future's circuit design. Nowadays most considered cases are various types of bias modulation, while the effect of change of conductor Hamiltonian is seldom addressed. In this paper, we investigate the response of ballistic transport induced by a sudden change of the conductor Hamiltonian. We formulize the terminal current in language of non-equilibrium Green's function. Our method is applied to one-dimensional tight-binding chains and we find that the terminal current has a delay to the Hamiltonian change. The amount of delay is not determined by the velocity of incident electrons in the bias window, but depends on the tight-binding hopping energy γ. The delay of current response at the detecting point away from where the Hamiltonian changes is s="true">Csup is="true">s="true">s="true">γs="true">s="true">?s="true">1sup>, where C is a constant independent of the system.  相似文献   
26.
Special generating functions and Mehler's formula for the univariate complex Hermite polynomials are obtained and next employed to introduce and study some one- and two-dimensional integral transforms of Segal–Bargmann type in the framework of some specific functional Hilbert spaces; including the so-called generalized Bargmann–Fock spaces that are realized as <span class="NLM_disp-formula-image inline-formula">script>src="//:0" data-src='{"type":"image","src":"/na101/home/literatum/publisher/tandf/journals/content/gitr20/2019/gitr20.v030.i07/10652469.2019.1593407/20190428/images/gitr_a_1593407_ilm0001.gif"}' />script>src="//:0" alt="" class="mml-formula" data-formula-source="{"type" : "image", "src" : "/na101/home/literatum/publisher/tandf/journals/content/gitr20/2019/gitr20.v030.i07/10652469.2019.1593407/20190428/images/gitr_a_1593407_ilm0001.gif"}" /><span class="mml-formula">span>span><span class="NLM_disp-formula inline-formula">src="//:0" alt="" data-formula-source="{"type" : "mathjax"}" />sup>L2sup>span>-eigenspaces of a special magnetic Schrödinger operator.  相似文献   
27.
In this paper we consider the long-time asymptotics of a linear version of the Smoluchowski equation which describes the evolution of a tagged particle moving in a random distribution of fixed particles. The volumes v of these particles are independently distributed according to a probability distribution which decays asymptotically as a power law sup is="true">s="true">s="true">vs="true">s="true">?s="true">σsup>. The validity of the equation has been rigorously proved in ss="workspace-trigger">[22] taking as a starting point a particle model and for values of the exponent s="true">σs="true">>s="true">3, but the model can be expected to be valid, on heuristic grounds, for s="true">σs="true">>s="true">s="true">s="true">5s="true">s="true">3. The resulting equation is a non-local linear degenerate parabolic equation. The solutions of this equation display a rich structure of different asymptotic behaviors according to the different values of the exponent σ. Here we show that for s="true">s="true">s="true">5s="true">s="true">3s="true"><s="true">σs="true"><s="true">2 the linear Smoluchowski equation is well-posed and that there exists a unique self-similar profile which is asymptotically stable.  相似文献   
28.
Consider an elastic thin three-dimensional body made of a periodic distribution of elastic inclusions. When both the thickness of the beam and the size of the heterogeneities tend simultaneously to zero the authors obtain three different one-dimensional models of beam depending upon the limit of the ratio of these two small parameters.  相似文献   
29.
We give an explicit and purely combinatorial description of the Duskin nerve of any stretchy="false" is="true">(s="true">rstyle="after" is="true">+s="true">1stretchy="false" is="true">)<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="6.861ex" height="2.709ex" viewBox="0 -847.3 2953.9 1166.2" role="img" focusable="false" style="vertical-align: -0.741ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">se xlink:href="#MJMAIN-28">se>s="true" transform="translate(389,0)">se xlink:href="#MJMATHI-72">se>s="true" transform="translate(1063,0)">se xlink:href="#MJMAIN-2B">se>s="true" transform="translate(2063,0)">se xlink:href="#MJMAIN-31">se>s="true" transform="translate(2564,0)">se xlink:href="#MJMAIN-29">se>svg><script type="math/mml" id="MathJax-Element-1">stretchy="false" is="true">(s="true">rstyle="after" is="true">+s="true">1stretchy="false" is="true">)script>-point suspension 2-category, and in particular of any 2-category belonging to Joyal's cell category sub is="true">s="true">s="true">Θs="true">s="true">2sub><svg xmlns:xlink="http://www.w3.org/1999/xlink" width="2.862ex" height="2.341ex" viewBox="0 -794.4 1232.4 1007.7" role="img" focusable="false" style="vertical-align: -0.495ex;">stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)">s="true">s="true">s="true">se xlink:href="#MJMAIN-398">se>s="true" transform="translate(778,-150)">s="true">se transform="scale(0.707)" xlink:href="#MJMAIN-32">se>svg><script type="math/mml" id="MathJax-Element-2">sub is="true">s="true">s="true">Θs="true">s="true">2sub>script>.  相似文献   
30.
Lipid metabolism has a significant function in the central nervous system and Alzheimer's disease (AD) is an age-related senile disease characterized by central nerve degeneration. The pathological development of AD is closely related to lipid metabolism disorders. To reveal the influence of Kai-Xin-San (KXS) on lipid metabolism in APP/PSI transgenic mice and potential therapeutic targets for treating AD, brain tissue samples were collected and analyzed by high-throughput lipidomics based on UPLC–Q/TOF-MS. The collected raw data were processed by multivariate data analysis to discover the potential biomarkers and lipid metabolic profiles. Compared with the control wild-type mouse group, nine potential lipid biomarkers were found in the AD model group, of which seven were up-regulated and two were down-regulated. Orally administrated KXS can reverse the changes in these potential biomarkers. Compared with the model group, a total of six differential metabolites showed a recovery trend and may be potential targets for KXS to treat AD. This study showed that high-throughput lipidomics can be used to discover the perturbed pathways and lipid biomarkers as potential targets to reveal the therapeutic effects of KXS.  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