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   9227篇
  免费   730篇
  国内免费   801篇
化学   2630篇
晶体学   100篇
力学   544篇
综合类   143篇
数学   4946篇
物理学   2395篇
  2024年   7篇
  2023年   67篇
  2022年   163篇
  2021年   222篇
  2020年   281篇
  2019年   238篇
  2018年   256篇
  2017年   234篇
  2016年   321篇
  2015年   242篇
  2014年   431篇
  2013年   762篇
  2012年   411篇
  2011年   475篇
  2010年   411篇
  2009年   516篇
  2008年   569篇
  2007年   608篇
  2006年   494篇
  2005年   434篇
  2004年   396篇
  2003年   412篇
  2002年   334篇
  2001年   299篇
  2000年   264篇
  1999年   249篇
  1998年   220篇
  1997年   181篇
  1996年   188篇
  1995年   139篇
  1994年   139篇
  1993年   89篇
  1992年   71篇
  1991年   67篇
  1990年   58篇
  1989年   47篇
  1988年   61篇
  1987年   41篇
  1986年   34篇
  1985年   52篇
  1984年   43篇
  1983年   24篇
  1982年   37篇
  1981年   27篇
  1980年   16篇
  1979年   35篇
  1978年   25篇
  1977年   24篇
  1976年   20篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
本文研究了包括二阶离化过程的强激光场下的双光子自电离。导出了光电子谱的解析表达式,并对一些特殊情况下的光电子谱进行了分析。  相似文献   
72.
73.
Some solvability conditions of periodic and subharmonic solutions are obtained for a class of subquadratic nonautonomous second-order Hamiltonian systems by the minimax methods in critical point theory.  相似文献   
74.
介绍了用溶胶-凝胶法(sol-gel)在Pt/Ti/SiO2/Si衬底和石英衬底上制备Ba(Zr0.3Ti0.7)O3铁电薄膜的基本原理、工艺过程及工艺特点;Sol-gel制备的Ba(Zr0.3Ti0.7)O3铁电薄膜表面平整、厚度均匀.  相似文献   
75.
Let G(x,y) and GD(x,y) be the Green functions of rotationally invariant symmetric α-stable process in Rd and in an open set D, respectively, where 0<α<2. The inequality GD(x,y)GD(y,z)/GD(x,z)?c(G(x,y)+G(y,z)) is a very useful tool in studying (local) Schrödinger operators. When the above inequality is true with c=c(D)∈(0,∞), then we say that the 3G theorem holds in D. In this paper, we establish a generalized version of 3G theorem when D is a bounded κ-fat open set, which includes a bounded John domain. The 3G we consider is of the form GD(x,y)GD(z,w)/GD(x,w), where y may be different from z. When y=z, we recover the usual 3G. The 3G form GD(x,y)GD(z,w)/GD(x,w) appears in non-local Schrödinger operator theory. Using our generalized 3G theorem, we give a concrete class of functions belonging to the non-local Kato class, introduced by Chen and Song, on κ-fat open sets. As an application, we discuss relativistic α-stable processes (relativistic Hamiltonian when α=1) in κ-fat open sets. We identify the Martin boundary and the minimal Martin boundary with the Euclidean boundary for relativistic α-stable processes in κ-fat open sets. Furthermore, we show that relative Fatou type theorem is true for relativistic stable processes in κ-fat open sets. The main results of this paper hold for a large class of symmetric Markov processes, as are illustrated in the last section of this paper. We also discuss the generalized 3G theorem for a large class of symmetric stable Lévy processes.  相似文献   
76.
Multiple integrals generalizing the iterated kernels of integral operators are expressed as single integrals in the case of a special representation of the kernel (this is our theorem). Besides integral equations, Markov processes involve these integrals as well. As a consequence of the theorem, we obtain transition probability densities of certain Markov processes. As an illustration, we consider nine examples.  相似文献   
77.
Satya Prakash 《Pramana》1989,33(1):109-131
This article summarizes the recent radiochemical investigations on mass, charge kinetic energy and fragment angular distributions in low energy fission of actinides.  相似文献   
78.
This paper considers a two-echelon capacitated supply chain with two non-identical retailers and information sharing. We characterize the optimal inventory policies. We also study the benefits of the optimal stock rationing policy over the first come first served (FCFS) and the modified echelon-stock rationing (MESR) policies.  相似文献   
79.
We construct random locally compact real trees called Lévy trees that are the genealogical trees associated with continuous-state branching processes. More precisely, we define a growing family of discrete Galton–Watson trees with i.i.d. exponential branch lengths that is consistent under Bernoulli percolation on leaves; we define the Lévy tree as the limit of this growing family with respect to the Gromov–Hausdorff topology on metric spaces. This elementary approach notably includes supercritical trees and does not make use of the height process introduced by Le Gall and Le Jan to code the genealogy of (sub)critical continuous-state branching processes. We construct the mass measure of Lévy trees and we give a decomposition along the ancestral subtree of a Poisson sampling directed by the mass measure. T. Duquesne is supported by NSF Grants DMS-0203066 and DMS-0405779. M. Winkel is supported by Aon and the Institute of Actuaries, EPSRC Grant GR/T26368/01, le département de mathématique de l’Université d’Orsay and NSF Grant DMS-0405779.  相似文献   
80.
随机环境中分枝过程的等价定理   总被引:7,自引:0,他引:7  
给定了随机环境中分枝过程(BPRE)的精确定义,讨论了有关的可测性问题和BPRE的基本性质.在此基础上,证明了BPRE的一个等价定理.  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