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   4580篇
  免费   93篇
  国内免费   50篇
化学   381篇
晶体学   5篇
力学   34篇
综合类   5篇
数学   4033篇
物理学   265篇
  2023年   13篇
  2022年   12篇
  2021年   23篇
  2020年   23篇
  2019年   132篇
  2018年   142篇
  2017年   65篇
  2016年   64篇
  2015年   43篇
  2014年   146篇
  2013年   318篇
  2012年   130篇
  2011年   245篇
  2010年   227篇
  2009年   339篇
  2008年   353篇
  2007年   358篇
  2006年   270篇
  2005年   199篇
  2004年   172篇
  2003年   138篇
  2002年   112篇
  2001年   83篇
  2000年   75篇
  1999年   75篇
  1998年   87篇
  1997年   55篇
  1996年   101篇
  1995年   87篇
  1994年   90篇
  1993年   78篇
  1992年   66篇
  1991年   36篇
  1990年   40篇
  1989年   26篇
  1988年   19篇
  1987年   27篇
  1986年   23篇
  1985年   28篇
  1984年   34篇
  1983年   16篇
  1982年   28篇
  1981年   30篇
  1980年   24篇
  1979年   13篇
  1978年   16篇
  1977年   16篇
  1976年   19篇
  1974年   4篇
  1973年   1篇
排序方式: 共有4723条查询结果,搜索用时 46 毫秒
1.
First, by using linear and trilinear estimates in Bourgain type analytic and Gevrey spaces, the local well‐posedness of the Cauchy problem for the modified Kawahara equation on the line is established for analytic initial data that can be extended as holomorphic functions in a strip around the x‐axis. Next we use this local result and a Gevrey approximate conservation law to prove that global solutions exist. Furthermore, we obtain explicit lower bounds for the radius of spatial analyticity given by , where can be taken arbitrarily small and c is a positive constant.  相似文献   
2.
We consider a Schrödinger operator L=?d2/dx2+V(x) on R, where V is a real-valued measurable function, and give an explicit and simple characterization of intrinsic ultracontractivity (IU) of the Schrödinger semigroup generated by L for a wide class of potentials. By making use of it, we also give new examples of potentials for which the semigroups satisfy (IU) or non-(IU).  相似文献   
3.
This paper concerns with the problem of how to running an insurance company to maximize his total discounted expected dividends. In our model, the dividend rate is limited in [0,M] and the company is allowed to transfer any proportion of risk by reinsuring. So there are two strategies which we call dividend strategy and reinsurance strategy. The objective function and the corresponding optimal two strategies are the solution and the two free boundaries of the following Barenblatt parabolic equation
vt?max0a1?(12a2σ2vxx+aμvx)+cv?max0lM?[(1?vx)l]=0
under certain boundary conditions on an angular domain
QT={(x,t)|0<x<Mt,0<tT}.
The main effort is to analyze the properties of the solution and the free boundaries to show the optimal decision for the insurance company.  相似文献   
4.
We present novel inorganic–organic hybrid catalyst to accomplish domino multi‐component reaction (MCR) for synthesis of 3‐amino‐2′‐oxospiro[benzo[c]pyrano[3,2‐a]phenazine‐1,3′‐indoline]‐2‐carbonitrile/carboxylate derivatives. This methodology offers remarkable development by easy production of H3PMo12O40/Hyd‐SBA‐15 in regard to solving the problem of using harsh catalysts, also it demonstrates to be impressive and environmentally friendly in term of low reaction times and high yields.  相似文献   
5.
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 C1) nonlinearities.  相似文献   
6.
General Lp dual curvature measures have recently been introduced by Lutwak, Yang and Zhang [24]. These new measures unify several other geometric measures of the Brunn–Minkowski theory and the dual Brunn–Minkowski theory. Lp dual curvature measures arise from qth dual intrinsic volumes by means of Alexandrov-type variational formulas. Lutwak, Yang and Zhang [24] formulated the Lp dual Minkowski problem, which concerns the characterization of Lp dual curvature measures. In this paper, we solve the existence part of the Lp dual Minkowski problem for p>1 and q>0, and we also discuss the regularity of the solution.  相似文献   
7.
8.
9.
We prove the existence of a travelling wave solution for a gravity-driven thin film of a viscous and incompressible dilatant fluid coated with an insoluble surfactant. The governing system of second order partial differential equations for the film's height h and the surfactant's concentration γ are derived by means of lubrication theory applied to the non-Newtonian Navier–Stokes equations.  相似文献   
10.
Bacterial adhesion, biofilm formation and host cell invasion of the ESKAPE pathogen Pseudomonas aeruginosa require the tetravalent lectins LecA and LecB, which are therefore drug targets to fight these infections. Recently, we have reported highly potent divalent galactosides as specific LecA inhibitors. However, they suffered from very low solubility and an intrinsic chemical instability due to two acylhydrazone motifs, which precluded further biological evaluation. Here, we isosterically substituted the acylhydrazones and systematically varied linker identity and length between the two galactosides necessary for LecA binding. The optimized divalent LecA ligands showed improved stability and were up to 1000-fold more soluble. Importantly, these properties now enabled their biological characterization. The lead compound L2 potently inhibited LecA binding to lung epithelial cells, restored wound closure in a scratch assay and reduced the invasiveness of P. aeruginosa into host cells.  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