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   1289篇
  免费   101篇
  国内免费   171篇
化学   66篇
晶体学   2篇
力学   103篇
综合类   32篇
数学   1197篇
物理学   161篇
  2023年   10篇
  2022年   11篇
  2021年   14篇
  2020年   16篇
  2019年   27篇
  2018年   30篇
  2017年   39篇
  2016年   38篇
  2015年   32篇
  2014年   59篇
  2013年   113篇
  2012年   91篇
  2011年   75篇
  2010年   71篇
  2009年   83篇
  2008年   94篇
  2007年   97篇
  2006年   97篇
  2005年   60篇
  2004年   55篇
  2003年   74篇
  2002年   57篇
  2001年   48篇
  2000年   38篇
  1999年   40篇
  1998年   40篇
  1997年   32篇
  1996年   24篇
  1995年   13篇
  1994年   11篇
  1993年   4篇
  1992年   8篇
  1991年   7篇
  1990年   9篇
  1989年   4篇
  1988年   4篇
  1986年   4篇
  1985年   5篇
  1984年   1篇
  1983年   2篇
  1982年   8篇
  1981年   4篇
  1980年   1篇
  1979年   4篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
  1959年   1篇
排序方式: 共有1561条查询结果,搜索用时 15 毫秒
51.
We demonstrated the interaction of a gold cone target with a femto second(fs) laser pulse above the relativistic intensity of 1.37×10 18 μm 2 W/cm 2.Relativistic electrons with energy above 2 MeV were observed.A 25%-40% increase of the electron temperature is achieved compared to the case when a plane gold target is used.The electron temperature increase results from the guiding of the laser beam at the tip and the intense quasistatic magnetic field in the cone geometry.The behavior of the relativistic electrons is verified in our 2D-PIC simulations.  相似文献   
52.
A particle constrained to move on a cone and bound to its tip by harmonic oscillator and Coulomb-Kepler potentials is considered both in the classical as well as in the quantum formulations. The SU(2) coherent states are formally derived for the former model and used for showing some relations between closed classical orbits and quantum probability densities. Similar relations are shown for the Coulomb-Kepler problem. In both cases a perfect localization of the densities on the classical solutions is obtained even for low values of quantum numbers.  相似文献   
53.
In this paper, we establish a theoretical framework of path-following interior point algorithms for the linear complementarity problems over symmetric cones (SCLCP) with the Cartesian P *(κ)-property, a weaker condition than the monotonicity. Based on the Nesterov-Todd, xy and yx directions employed as commutative search directions for semidefinite programming, we extend the variants of the short-, semilong-, and long-step path-following algorithms for symmetric conic linear programming proposed by Schmieta and Alizadeh to the Cartesian P *(κ)-SCLCP, and particularly show the global convergence and the iteration complexities of the proposed algorithms. This work was supported by National Natural Science Foundation of China (Grant Nos. 10671010, 70841008)  相似文献   
54.
半无限规划的一个对偶问题   总被引:1,自引:0,他引:1  
本文对半无限凸规划提出一个新的对偶问题,使用扰动函数、次微分和法锥,文中证明了相应的弱对偶性及强对偶性的充要条件.  相似文献   
55.
A NEW FIXED POINT THEOREM FOR CONE MAPS AND ITS APPLICATIONS   总被引:1,自引:0,他引:1  
1IntroductionLetEbearealBanachspace.AnonemptyconvexclosedsetPCEiscalledaconeinEifitsatisfiesthefollowingtwoconditionsf(i)xEP,A20impliesAxEP,(n)xEP,--xEPimpliesx=0.AconePiscalledsolidifitcontainsinteriorpoints,i.e.,P/gi.TheconePinEdefinesapartialorderingx5…  相似文献   
56.
四阶非线性特征值问题的正解   总被引:6,自引:1,他引:5  
本文考虑了四阶非线性特征值问题d4u/dt4=λg(t)f(u,u″),0<t<1,u(0)=u(1)=0,au″(0)-bu″′(0)=0,cu″(1)+du″′(1)=0.其中g(t)∈C((0,1),[0,∞)),f(u,v)∈C([0,∞)×(-∞,0],[0,∞)),a≥0,b≥0,c ≥0,d ≥ 0,且△=ac+ad+bc>0.利用锥压缩与拉伸不动点定理,获得了上述问题正解的存在性结果.  相似文献   
57.
A new fixed point theorem in a cone is applied to obtain the existence of at least one positive solution for the second order three-point boundary value problem
  相似文献   
58.
Semistrictly quasiconvex mappings and non-convex vector optimization   总被引:1,自引:0,他引:1  
This paper introduces a new class of non-convex vector functions strictly larger than that of P-quasiconvexity, with P m being the underlying ordering cone, called semistrictly ( m\ –int P)-quasiconvex functions. This notion allows us to unify various results on existence of weakly efficient (weakly Pareto) optima. By imposing a coercivity condition we establish also the compactness of the set of weakly Pareto solutions. In addition, we provide various characterizations for the non-emptiness, convexity and compactness of the solution set for a subclass of quasiconvex vector optimization problems on the real-line. Finally, it is also introduced the notion of explicit ( m\ –int P)-quasiconvexity (equivalently explicit (int P)-quasiconvexity) which plays the role of explicit quasiconvexity (quasiconvexity and semistrict quasiconvexity) of real-valued functions.Acknowldegements.The author wishes to thank both referees for their careful reading of the paper, their comments, remarks, helped to improve the presentation of some results. One of the referee provided the references [5, 6] and indirectly [20].  相似文献   
59.
Existence of positive solutions for the nonlinear fractional differential equation Dsu(x)=f(x,u(x)), 0<s<1, has been studied (S. Zhang, J. Math. Anal. Appl. 252 (2000) 804-812), where Ds denotes Riemann-Liouville fractional derivative. In the present work we study existence of positive solutions in case of the nonlinear fractional differential equation:
L(D)u=f(x,u),u(0)=0,0<x<1,  相似文献   
60.
Armony  Mor  Bambos  Nicholas 《Queueing Systems》2003,44(3):209-252
We study a processing system comprised of parallel queues, whose individual service rates are specified by a global service mode (configuration). The issue is how to switch the system between various possible service modes, so as to maximize its throughput and maintain stability under the most workload-intensive input traffic traces (arrival processes). Stability preserves the job inflow–outflow balance at each queue on the traffic traces. Two key families of service policies are shown to maximize throughput, under the mild condition that traffic traces have long-term average workload rates. In the first family of cone policies, the service mode is chosen based on the system backlog state belonging to a corresponding cone. Two distinct policy classes of that nature are investigated, MaxProduct and FastEmpty. In the second family of batch policies (BatchAdapt), jobs are collectively scheduled over adaptively chosen horizons, according to an asymptotically optimal, robust schedule. The issues of nonpreemptive job processing and non-negligible switching times between service modes are addressed. The analysis is extended to cover feed-forward networks of such processing systems/nodes. The approach taken unifies and generalizes prior studies, by developing a general trace-based modeling framework (sample-path approach) for addressing the queueing stability problem. It treats the queueing structure as a deterministic dynamical system and analyzes directly its evolution trajectories. It does not require any probabilistic superstructure, which is typically used in previous approaches. Probability can be superposed later to address finer performance questions (e.g., delay). The throughput maximization problem is seen to be primarily of structural nature. The developed methodology appears to have broader applicability to other queueing systems.  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