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   11893篇
  免费   248篇
  国内免费   199篇
化学   1351篇
晶体学   70篇
力学   92篇
综合类   32篇
数学   9468篇
物理学   1327篇
  2023年   34篇
  2022年   107篇
  2021年   55篇
  2020年   69篇
  2019年   251篇
  2018年   280篇
  2017年   154篇
  2016年   127篇
  2015年   145篇
  2014年   311篇
  2013年   689篇
  2012年   358篇
  2011年   814篇
  2010年   637篇
  2009年   715篇
  2008年   851篇
  2007年   905篇
  2006年   727篇
  2005年   489篇
  2004年   386篇
  2003年   390篇
  2002年   283篇
  2001年   256篇
  2000年   255篇
  1999年   291篇
  1998年   270篇
  1997年   198篇
  1996年   267篇
  1995年   334篇
  1994年   243篇
  1993年   229篇
  1992年   180篇
  1991年   114篇
  1990年   114篇
  1989年   99篇
  1988年   62篇
  1987年   70篇
  1986年   43篇
  1985年   100篇
  1984年   61篇
  1983年   47篇
  1982年   65篇
  1981年   63篇
  1980年   35篇
  1979年   34篇
  1978年   39篇
  1977年   36篇
  1976年   26篇
  1975年   11篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 12 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.
Seven new copper(II) complexes of type [Cu(A)(L)]?H2O (A = sparfloxacin, ciprofloxacin, levofloxacin, gatifloxacin, pefloxacin, ofloxacin, norfloxacin; L = 5‐[(3‐chlorophenyl)diazenyl]‐4‐hydroxy‐1,3‐thiazole‐2(3H)‐thione) were synthesized and characterized using elemental and thermogravimetric analyses, and electronic, electron paramagnetic resonance (EPR), Fourier transform infrared and liquid chromatography–mass spectroscopies. Tetrahedral geometry around copper is assigned in all complexes using EPR and electronic spectral analyses. All complexes were investigated for their interaction with herring sperm DNA utilizing absorption titration (Kb = 1.27–3.13 × 105 M?1) and hydrodynamic volume measurement studies. The studies suggest the classical intercalative mode of DNA binding. The cleavage reaction on pUC19 DNA was monitored by agarose gel electrophoresis. The results indicate that the Cu(II) complexes can more effectively promote the cleavage of plasmid DNA. The superoxide dismutase mimic activity of the complexes was evaluated by nitroblue tetrazolium assay, and the complexes catalysed the dismutation of superoxide at pH = 7.8 with IC50 values in the range 0.597–0.900 μM. The complexes were screened for their in vitro antibacterial activity against five pathogenic bacteria. All the complexes are good cytotoxic agents and show LC50 values ranging from 5.559 to 11.912 µg ml?1. All newly synthesized Cu(II) complexes were also evaluated for their in vitro antimalarial activity against Plasmodium falciparum strain (IC50 = 0.62–2.0 µg ml?1). Copyright © 2015 John Wiley & Sons, Ltd.  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.
Summary. We generalise and apply a refinement indicator of the type originally designed by Mackenzie, Süli and Warnecke in [15] and [16] for linear Friedrichs systems to the Euler equations of inviscid, compressible fluid flow. The Euler equations are symmetrized by means of entropy variables and locally linearized about a constant state to obtain a symmetric hyperbolic system to which an a posteriori error analysis of the type introduced in [15] can be applied. We discuss the details of the implementation of the refinement indicator into the DLR--Code which is based on a finite volume method of box type on an unstructured grid and present numerical results. Received May 15, 1995 / Revised version received April 17, 1996  相似文献   
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.
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