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   19090篇
  免费   403篇
  国内免费   185篇
化学   1207篇
晶体学   65篇
力学   172篇
综合类   29篇
数学   16852篇
物理学   1353篇
  2023年   31篇
  2022年   52篇
  2021年   61篇
  2020年   76篇
  2019年   394篇
  2018年   454篇
  2017年   239篇
  2016年   201篇
  2015年   217篇
  2014年   467篇
  2013年   1172篇
  2012年   547篇
  2011年   1209篇
  2010年   937篇
  2009年   1192篇
  2008年   1384篇
  2007年   1428篇
  2006年   1009篇
  2005年   758篇
  2004年   602篇
  2003年   509篇
  2002年   410篇
  2001年   364篇
  2000年   359篇
  1999年   481篇
  1998年   425篇
  1997年   317篇
  1996年   420篇
  1995年   426篇
  1994年   413篇
  1993年   351篇
  1992年   308篇
  1991年   234篇
  1990年   215篇
  1989年   214篇
  1988年   146篇
  1987年   149篇
  1986年   129篇
  1985年   223篇
  1984年   188篇
  1983年   108篇
  1982年   187篇
  1981年   168篇
  1980年   112篇
  1979年   75篇
  1978年   108篇
  1977年   82篇
  1976年   63篇
  1975年   22篇
  1974年   19篇
排序方式: 共有10000条查询结果,搜索用时 203 毫秒
1.
In this paper, let (Mn,g,dμ) be n-dimensional noncompact metric measure space which satisfies Poincaré inequality with some Ricci curvature condition. We obtain a Liouville theorem for positive weak solutions to weighted p-Lichnerowicz equation
p,fv+cvσ=0,
where c0,m>n1,1<p<m?1+(m?1)(m+3)2,σp?1 are real constants.  相似文献   
2.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual.  相似文献   
3.
4.
We relate the distribution characters and the wave front sets of unitary representation for real reductive dual pairs of type I in the stable range.  相似文献   
5.
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism H2m+1(F)?H2m+1(L) induced by scalar extension, where L/F is a purely inseparable extension (of any degree), H2m+1(F) is the cokernel of the Artin–Schreier operator ?:ΩFm?ΩFm/dΩFm?1 given by: xdx1x1?dxmxm?(x2?x)dx1x1?dxmxm+dΩFm?1, where ΩFm is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included.  相似文献   
6.
A manifold that contains small perturbations will induce a perturbed partial differential equation. The partial differential equation that we select is the Poisson equation – in order to explore the interplay between the geometry of the manifold and the perturbations. Specifically, we show how the problem of symmetry determination, for higher-order perturbations, can be elegantly expressed via geometric conditions.  相似文献   
7.
We show the short-time existence and nonlinear stability of vortex sheets for the nonisentropic compressible Euler equations in two spatial dimensions, based on the weakly linear stability result of Morando and Trebeschi (2008) [20]. The missing normal derivatives are compensated through the equations of the linearized vorticity and entropy when deriving higher-order energy estimates. The proof of the resolution for this nonlinear problem follows from certain a priori tame estimates on the effective linear problem in the usual Sobolev spaces and a suitable Nash–Moser iteration scheme.  相似文献   
8.
9.
2 laser of wide tunability to pump 13CD3OD we could observe 10 new far infrared laser lines ranging from 109 μm to 472 μm. The lines were generated by pumping infrared absorbing transitions of large offset appertaining to the C-O stretching Q-branch. All lines were characterised in wavelength, polarisation, optimum pressure of operation and precise offset measurements. Received: 17 September 1996/Revised version: 18 November 1996  相似文献   
10.
In this note we show that the chain space belonging to a quadric can be embedded into the chain geometry over a Clifford algebra via a generalized stereographic projection.  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