全文获取类型
收费全文 | 18788篇 |
免费 | 1787篇 |
国内免费 | 2059篇 |
专业分类
化学 | 1741篇 |
晶体学 | 112篇 |
力学 | 1315篇 |
综合类 | 417篇 |
数学 | 15579篇 |
物理学 | 3470篇 |
出版年
2024年 | 24篇 |
2023年 | 207篇 |
2022年 | 222篇 |
2021年 | 299篇 |
2020年 | 399篇 |
2019年 | 518篇 |
2018年 | 467篇 |
2017年 | 520篇 |
2016年 | 597篇 |
2015年 | 464篇 |
2014年 | 880篇 |
2013年 | 1431篇 |
2012年 | 792篇 |
2011年 | 1098篇 |
2010年 | 967篇 |
2009年 | 1248篇 |
2008年 | 1360篇 |
2007年 | 1379篇 |
2006年 | 1156篇 |
2005年 | 1073篇 |
2004年 | 838篇 |
2003年 | 895篇 |
2002年 | 843篇 |
2001年 | 694篇 |
2000年 | 738篇 |
1999年 | 637篇 |
1998年 | 563篇 |
1997年 | 496篇 |
1996年 | 349篇 |
1995年 | 212篇 |
1994年 | 195篇 |
1993年 | 137篇 |
1992年 | 110篇 |
1991年 | 109篇 |
1990年 | 68篇 |
1989年 | 69篇 |
1988年 | 63篇 |
1987年 | 44篇 |
1986年 | 36篇 |
1985年 | 73篇 |
1984年 | 66篇 |
1983年 | 32篇 |
1982年 | 51篇 |
1981年 | 34篇 |
1980年 | 36篇 |
1979年 | 38篇 |
1978年 | 28篇 |
1977年 | 16篇 |
1976年 | 16篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
John A. Ekaterinaris 《国际流体数值方法杂志》2004,45(11):1187-1207
A high‐order accurate, finite‐difference method for the numerical solution of incompressible flows is presented. This method is based on the artificial compressibility formulation of the incompressible Navier–Stokes equations. Fourth‐ or sixth‐order accurate discretizations of the metric terms and the convective fluxes are obtained using compact, centred schemes. The viscous terms are also discretized using fourth‐order accurate, centred finite differences. Implicit time marching is performed for both steady‐state and time‐accurate numerical solutions. High‐order, spectral‐type, low‐pass, compact filters are used to regularize the numerical solution and remove spurious modes arising from unresolved scales, non‐linearities, and inaccuracies in the application of boundary conditions. The accuracy and efficiency of the proposed method is demonstrated for test problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
72.
Yuh-Shan Ho 《Adsorption》2004,10(2):151-158
The kinetics of four sorption systems, Cu/tree fern, Pb/tree fern, AB9/activated clay and BR18/activated clay have been studied based on the assumption of a pseudo-second order rate law. Pseudo-isotherms using the pseudo-second order kinetic expression constant have been developed to describe the four liquid-solid sorption systems. The experimental results have been analyzed using a pseudo-Langmuir and a pseudo-Redlich-Peterson isotherm. Both isotherms were found to represent the measured sorption data well. According to the evaluation using the pseudo-Langmuir equation, the monolayer sorption capacities were obtained to be 13.9, 46.6, 124 and 105 mg g–1 for copper, lead, AB9 and BR18 respectively. 相似文献
73.
Tae Young Kim Dong Myung Kim Won Jung Kim Tae Hee Lee Kwang S. Suh 《Journal of Polymer Science.Polymer Physics》2004,42(15):2813-2820
The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004 相似文献
74.
75.
Wolfgang Knirsch 《Mathematische Nachrichten》2004,265(1):15-23
On weighted spaces with strictly plurisubharmonic weightfunctions the canonical solution operator of and the ‐Neumann operator are bounded. In this paper we find a class of strictly plurisubharmonic weightfunctions with certain growth conditions, so that they are Hilbert‐Schmidt operators between weighted spaces with different weightfunctions, if they are restricted to forms with holomorphic coefficients. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
76.
77.
The exponential functional of simple, symmetric random walks with negative
drift is an infinite polynomial Y = 1 + ξ1 + ξ1ξ2 + ξ1ξ2ξ3 + ⋯ of independent
and identically distributed non-negative random variables. It has moments that are
rational functions of the variables μ
k
= E(ξ
k
) < 1 with universal coefficients. It
turns out that such a coefficient is equal to the number of permutations with descent
set defined by the multiindex of the coefficient. A recursion enumerates all numbers
of permutations with given descent sets in the form of a Pascal-type triangle.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
78.
We construct a universal space for the class of proper metric spaces of bounded geometry and of given asymptotic dimension. As a consequence of this result, we establish coincidence of asymptotic dimension with asymptotic inductive dimension. 相似文献
79.
Boris Goldfarb 《Topology and its Applications》2004,140(2-3):267-294
New compactifications of symmetric spaces of noncompact type X are constructed using the asymptotic geometry of the Borel–Serre enlargement. The controlled K-theory associated to these compactifications is used to prove the integral Novikov conjecture for arithmetic groups. 相似文献
80.
The rotating flow in the presence of a magnetic field is a problem belonging to hydromagnetics and deserves to be more widely studied than it has been to date. In the non‐linear regime the literature is scarce. We develop the governing equations for the unsteady hydromagnetic rotating flow of a fourth‐order fluid past a porous plate. The steady flow is governed by a boundary value problem in which the order of differential equations is more than the number of available boundary conditions. It is shown that by augmenting the boundary conditions based on asymptotic structures at infinity it is possible to obtain numerical solutions of the nonlinear hydromagnetic equations. Effects of uniform suction or blowing past the porous plate, exerted magnetic field and rotation on the flow phenomena, especially on the boundary layer structure near the plate, are numerically analysed and discussed. The flow behaviours of the Newtonian fluid and second‐, third‐ and fourth‐order non‐Newtonian fluids are compared for the special flow problem, respectively. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献