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   2390篇
  免费   243篇
  国内免费   264篇
化学   86篇
晶体学   4篇
力学   171篇
综合类   69篇
数学   2010篇
物理学   557篇
  2024年   7篇
  2023年   35篇
  2022年   34篇
  2021年   52篇
  2020年   81篇
  2019年   59篇
  2018年   60篇
  2017年   62篇
  2016年   82篇
  2015年   71篇
  2014年   137篇
  2013年   144篇
  2012年   90篇
  2011年   108篇
  2010年   109篇
  2009年   138篇
  2008年   153篇
  2007年   183篇
  2006年   143篇
  2005年   134篇
  2004年   134篇
  2003年   132篇
  2002年   124篇
  2001年   87篇
  2000年   93篇
  1999年   95篇
  1998年   63篇
  1997年   77篇
  1996年   48篇
  1995年   32篇
  1994年   35篇
  1993年   17篇
  1992年   12篇
  1991年   17篇
  1990年   9篇
  1989年   9篇
  1988年   6篇
  1987年   6篇
  1986年   5篇
  1985年   5篇
  1984年   1篇
  1983年   2篇
  1980年   1篇
  1977年   2篇
  1972年   1篇
  1957年   1篇
  1936年   1篇
排序方式: 共有2897条查询结果,搜索用时 0 毫秒
21.
p阶平均曲率算子Dirichlet问题的无穷多个解   总被引:1,自引:0,他引:1  
§ 1  IntroductionSince the Mountain Pass Theorem came out,the existence of nontrivial solutions,pos-sibly multiple,ofnonlinear elliptic equations has been extensively studied.In this paper,weconsider the following Dirichlet problem for p-(generalized) mean curvature operator:-div((1 +| u|2 ) p- 22 u) =f(x,u) ,  x∈Ω,u∈ W1 ,p0 (Ω ) , (1 .1 )whereΩ is a bounded domain in Rn(n>p>1 ) with smooth boundary Ω.First let us recall the following Dirichletproblem for p-Laplacian:-Δpu≡ -div…  相似文献   
22.
In this paper, we provide simple and explicit formulas for computing Riemannian curvatures, mean curvature vectors, principal curvatures and principal directions for a 2-dimensional Riemannian manifold embedded in IR^k with k ≥ 3.  相似文献   
23.
In this paper,we derive an elementary identity for smooth solutions of the following equation:△u(x) K(x)e^2u(x)=0 in R^2 and use it to get some global properties of the solutions.  相似文献   
24.
We establish a link between rational homotopy theory and the problem which vector bundles admit a complete Riemannian metric of nonnegative sectional curvature. As an application, we show for a large class of simply-connected nonnegatively curved manifolds that, if lies in the class and is a torus of positive dimension, then ``most' vector bundles over admit no complete nonnegatively curved metrics.

  相似文献   

25.
In this paper,the authors obtain the Backlund transformation on time-like surfaces with constant mean curvature in R2,1.Using this transformation,families of surfaces with constant mean curvature from known ones can be constructed.  相似文献   
26.
For an integer n3 and any positive number , we establish the existence of smooth functions K on n {0} with |K–1|, such that the equation has a smooth positive solution which blows up at the origin (i.e., u does not have slow decay near the origin). Furthermore, we show that in some situations K can be extended as a Lipschitz function on n . These provide counter-examples to a conjecture of C.-S. Lin when n>4, and a question of Taliaferro. Mathematics Subject Classification (2000)Primary 35J60; Secondary 53C21  相似文献   
27.
Some curvature conditions about the geodesics emanating from a submanifold are obtained. These conditions are used to to study the topological and geometric properties of the ambient spaces which admit some minimal submanifolds.  相似文献   
28.
We construct two examples of spaces homeomorphic to R n (n3) each of which has a closed geodesic and admits no isoperimetric inequality. The first is a complete polyhedral metric space of nonpositive curvature, and the second is an incomplete Riemannian space with nonpositive sectional curvatures.  相似文献   
29.
In this article a simple form of expressing and studying the order conditions to be satisfied by starting algorithms for Runge–Kutta methods, which use information from the two previous steps is presented. In particular, starting algorithms of highest order for Runge–Kutta–Gauss methods up to seven stages are derived. Some numerical experiments with Hamiltonian systems to compare the behaviour of the new starting algorithms with other existing ones are presented.  相似文献   
30.
We construct a new family of cyclic difference sets with parameters ((3 d – 1)/2, (3 d – 1 – 1)/2, (3 d – 2 – 1)/2) for each odd d. The difference sets are constructed with certain maps that form Jacobi sums. These new difference sets are similar to Maschietti's hyperoval difference sets, of the Segre type, in characteristic two. We conclude by calculating the 3-ranks of the new difference sets.  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