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   14292篇
  免费   1000篇
  国内免费   804篇
化学   189篇
晶体学   2篇
力学   1428篇
综合类   166篇
数学   13239篇
物理学   1072篇
  2024年   20篇
  2023年   139篇
  2022年   158篇
  2021年   199篇
  2020年   314篇
  2019年   324篇
  2018年   378篇
  2017年   385篇
  2016年   372篇
  2015年   274篇
  2014年   607篇
  2013年   1148篇
  2012年   650篇
  2011年   764篇
  2010年   679篇
  2009年   939篇
  2008年   987篇
  2007年   1017篇
  2006年   896篇
  2005年   696篇
  2004年   598篇
  2003年   666篇
  2002年   573篇
  2001年   428篇
  2000年   418篇
  1999年   377篇
  1998年   344篇
  1997年   310篇
  1996年   239篇
  1995年   204篇
  1994年   138篇
  1993年   119篇
  1992年   119篇
  1991年   104篇
  1990年   79篇
  1989年   38篇
  1988年   41篇
  1987年   38篇
  1986年   41篇
  1985年   54篇
  1984年   53篇
  1983年   28篇
  1982年   28篇
  1981年   25篇
  1980年   18篇
  1979年   21篇
  1978年   14篇
  1977年   15篇
  1976年   9篇
  1936年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We study the initial boundary value problem for the one‐dimensional Kuramoto–Sivashinsky equation posed in a half line with nonhomogeneous boundary conditions. Through the analysis of the boundary integral operator, and applying the known results of the Cauchy problem of the Kuramoto–Sivashinsky equation posed on the whole line , the initial boundary value problem of the Kuramoto–Sivashinsky equation is shown to be globally well‐posed in Sobolev space for any s >?2. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
92.
The purpose of this paper is to study the mixed Dirichlet‐Neumann boundary value problem for the semilinear Darcy‐Forchheimer‐Brinkman system in L p ‐based Besov spaces on a bounded Lipschitz domain in R 3 , with p in a neighborhood of 2. This system is obtained by adding the semilinear term | u | u to the linear Brinkman equation. First, we provide some results about equivalence between the Gagliardo and nontangential traces, as well as between the weak canonical conormal derivatives and the nontangential conormal derivatives. Various mapping and invertibility properties of some integral operators of potential theory for the linear Brinkman system, and well‐posedness results for the Dirichlet and Neumann problems in L p ‐based Besov spaces on bounded Lipschitz domains in R n (n ≥3) are also presented. Then, using integral potential operators, we show the well‐posedness in L 2‐based Sobolev spaces for the mixed problem of Dirichlet‐Neumann type for the linear Brinkman system on a bounded Lipschitz domain in R n (n ≥3). Further, by using some stability results of Fredholm and invertibility properties and exploring invertibility of the associated Neumann‐to‐Dirichlet operator, we extend the well‐posedness property to some L p ‐based Sobolev spaces. Next, we use the well‐posedness result in the linear case combined with a fixed point theorem to show the existence and uniqueness for a mixed boundary value problem of Dirichlet and Neumann type for the semilinear Darcy‐Forchheimer‐Brinkman system in L p ‐based Besov spaces, with p ∈(2?ε ,2+ε ) and some parameter ε >0.  相似文献   
93.
In this article, we discuss the integral representation of quaternionic harmonic functions in the half space with the general boundary condition. Next, we derive a lower bound from an upper one for quaternionic harmonic functions. These results generalize some of the classic results from the case of plane to the case of noncommutative quaterninionic half space. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   
94.
In this paper the modeling of a thin plate in unilateral contact with a rigid plane is properly justified.Starting from the three-dimensional nonlinear Signorini problem,by an asymptotic approach the convergence of the displacement field as the thickness of the plate goes to zero is studied.It is shown that the transverse mechanical displacement field decouples from the in-plane components and solves an obstacle problem.  相似文献   
95.
Abstract

This paper considers the garbage collection problem in which vehicles with multiple compartments are used to collect the garbage. The vehicles are considered to be Alternative Fuel-powered Vehicles (AFVs). Compared with the traditional fossil fuel powered vehicles, the AFVs have limited fuel tank capacity. In addition, AFVs are allowed to refuel only at the depot. We provide a mathematical formulation and develop two solution approaches to solve the problem. The first approach is based on the saving algorithm, while the second is based on the ant colony system (ACS) metaheuristic. New problem instances have been generated to evaluate the performance of the proposed algorithms.  相似文献   
96.
97.
98.
99.
The Hamilton–Waterloo problem asks for a 2‐factorization of (for v odd) or minus a 1‐factor (for v even) into ‐factors and ‐factors. We completely solve the Hamilton–Waterloo problem in the case of C3‐factors and ‐factors for .  相似文献   
100.
We prove new results regarding the existence of positive solutions for a nonlinear periodic boundary value problem related to the Liebau phenomenon. As a consequence we obtain new sufficient conditions for the existence of a pump in a simple model. Our methodology relies on the use of classical fixed point index. Some examples are provided to illustrate our theory. We improve and complement previous results in the literature.  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