全文获取类型
收费全文 | 3958篇 |
免费 | 159篇 |
国内免费 | 30篇 |
专业分类
化学 | 2492篇 |
晶体学 | 17篇 |
力学 | 117篇 |
数学 | 867篇 |
物理学 | 654篇 |
出版年
2023年 | 39篇 |
2022年 | 82篇 |
2021年 | 94篇 |
2020年 | 73篇 |
2019年 | 86篇 |
2018年 | 67篇 |
2017年 | 81篇 |
2016年 | 154篇 |
2015年 | 115篇 |
2014年 | 134篇 |
2013年 | 229篇 |
2012年 | 280篇 |
2011年 | 317篇 |
2010年 | 189篇 |
2009年 | 198篇 |
2008年 | 269篇 |
2007年 | 245篇 |
2006年 | 225篇 |
2005年 | 185篇 |
2004年 | 185篇 |
2003年 | 111篇 |
2002年 | 120篇 |
2001年 | 56篇 |
2000年 | 62篇 |
1999年 | 38篇 |
1998年 | 39篇 |
1997年 | 32篇 |
1996年 | 44篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 22篇 |
1992年 | 32篇 |
1991年 | 21篇 |
1990年 | 30篇 |
1989年 | 13篇 |
1988年 | 22篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 23篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1977年 | 6篇 |
1974年 | 7篇 |
1971年 | 6篇 |
1963年 | 5篇 |
排序方式: 共有4147条查询结果,搜索用时 31 毫秒
961.
Maria Navarro‐Pascual‐Ahuir Maria J. Lerma‐García Guillermo Ramis‐Ramos Ernesto F. Simó‐Alfonso José M. Herrero‐Martínez 《Electrophoresis》2013,34(6):925-934
In this article, capillary columns constituted by lauryl methacrylate monoliths with embedded silver nanoparticles (AgNPs) were developed and tested. Two incorporation approaches of AgNPs in monoliths were explored. The AgNPs were either photogenerated in situ during polymerization of the monolith by UV irradiation, or incorporated to the polymerization mixture (ex situ). The influence of the AgNP concentration on the morphological and chromatographic properties of the polymer matrix was investigated, and both the in situ and ex situ approaches were comparatively discussed. The morphology of the monoliths was characterized by electron microscopic techniques, and their electrochromatographic performance was also evaluated with test mixtures of neutral compounds (sterols, fatty acid methyl esters, tocopherols, and polyaromatic hydrocarbons). 相似文献
962.
963.
964.
In this work we present a convective instability as the mechanism for generating vertical vortices in a cylindrical annulus non-homogeneously heated from below. Assuming axisymmetry, we study thermal and geometrical conditions under which stable vortical structures are found. The structure of these vortices appears to be qualitatively similar to that of dust devils. 相似文献
965.
Oscar RomeroAlejandro Castro Joel L. TeránDino Gnecco María L. OreaÁngel Mendoza Marcos FloresLuis F. Roa Jorge R. Juárez 《Tetrahedron letters》2011,52(45):5947-5950
The diastereoselective substitution of 3-bromolactam derived from (R)-(−)-2-phenylglycinol with a variety of arylcuprate reagents is presented. The stereochemical outcome of the substitution reaction is discussed. The method provides an efficient and straightforward route to enantiopure 3-arylpiperidines. 相似文献
966.
L. Corrêa G.A. B. Lima M.A. C. Candezano M.P. S. Braun C.M. Oishi H.A. Navarro V.G. Ferreira 《国际流体数值方法杂志》2013,72(12):1263-1285
A bounded upwinding scheme for numerical solution of hyperbolic conservation laws and Navier–Stokes equations is presented. The scheme is based on convection boundedness criterion and total variation diminishing stability criteria and developed by employing continuously differentiable functions. The accuracy of the scheme is verified by assessing the error and observed convergence rate on 1‐D benchmark test cases. A comparative study between the new scheme and conventional total variation diminishing/convection boundedness criterion‐based upwind schemes to solve standard nonlinear hyperbolic conservation laws is also accomplished. The scheme is then examined in the simulation of Newtonian and non‐Newtonian fluid flows of increasing complexity; a satisfactory agreement has been observed in terms of the overall behavior. Finally, the scheme is used to study the hydrodynamics of a gas‐solid flow in a bubbling fluidized bed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
967.
968.
Jorge S. Ayala-Arenas Reneu L. Andrioli Jr S. Watanabe M. Matsuoka B. C. Bhatt 《Radiation Physics and Chemistry》2001,61(3-6):417-419
Morganite, a pink beryl with the chemical formula Be3Al2Si6O18, was investigated in terms of its thermally stimulated luminescence (TL) and electron paramagnetic resonance (EPR) properties due to point defects. Atomic hydrogen H°-centers were induced by γ-radiation and shown to be responsible for a 165°C TL peak. The Fe3+-center concentration was found to increase with γ-dose, observed by both TL and EPR measurements, decreasing with thermal treatments beyond 250°C. A mechanism for emission around 315°C is proposed. 相似文献
969.
In this paper we present some formulae for topological invariants of projective complete intersection curves with isolated
singularities in terms of the Milnor number, the Euler characteristic and the topological genus. We also present some conditions,
involving the Milnor number and the degree of the curve, for the irreducibility of complete intersection curves. 相似文献
970.
Covering point sets with two disjoint disks or squares 总被引:1,自引:0,他引:1
Sergio Cabello J. Miguel Díaz-Bez Carlos Seara J. Antoni Sellars Jorge Urrutia Inmaculada Ventura 《Computational Geometry》2008,40(3):195-206
We study the following problem: Given a set of red points and a set of blue points on the plane, find two unit disks CR and CB with disjoint interiors such that the number of red points covered by CR plus the number of blue points covered by CB is maximized. We give an algorithm to solve this problem in O(n8/3log2n) time, where n denotes the total number of points. We also show that the analogous problem of finding two axis-aligned unit squares SR and SB instead of unit disks can be solved in O(nlogn) time, which is optimal. If we do not restrict ourselves to axis-aligned squares, but require that both squares have a common orientation, we give a solution using O(n3logn) time. 相似文献