全文获取类型
收费全文 | 67894篇 |
免费 | 2329篇 |
国内免费 | 1463篇 |
专业分类
化学 | 45230篇 |
晶体学 | 422篇 |
力学 | 1967篇 |
综合类 | 10篇 |
数学 | 9979篇 |
物理学 | 14078篇 |
出版年
2023年 | 462篇 |
2022年 | 650篇 |
2021年 | 889篇 |
2020年 | 912篇 |
2019年 | 915篇 |
2018年 | 1235篇 |
2017年 | 1034篇 |
2016年 | 2026篇 |
2015年 | 1801篇 |
2014年 | 1884篇 |
2013年 | 4095篇 |
2012年 | 4579篇 |
2011年 | 4729篇 |
2010年 | 2816篇 |
2009年 | 2712篇 |
2008年 | 3864篇 |
2007年 | 3883篇 |
2006年 | 3401篇 |
2005年 | 3416篇 |
2004年 | 3333篇 |
2003年 | 2584篇 |
2002年 | 2303篇 |
2001年 | 1310篇 |
2000年 | 1088篇 |
1999年 | 817篇 |
1998年 | 652篇 |
1997年 | 609篇 |
1996年 | 730篇 |
1995年 | 537篇 |
1994年 | 509篇 |
1993年 | 537篇 |
1992年 | 539篇 |
1991年 | 455篇 |
1990年 | 449篇 |
1989年 | 424篇 |
1988年 | 374篇 |
1987年 | 374篇 |
1986年 | 323篇 |
1985年 | 515篇 |
1984年 | 498篇 |
1983年 | 353篇 |
1982年 | 455篇 |
1981年 | 426篇 |
1980年 | 399篇 |
1979年 | 355篇 |
1978年 | 351篇 |
1977年 | 305篇 |
1976年 | 345篇 |
1975年 | 328篇 |
1974年 | 320篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C
1 transformation. 相似文献
22.
Régine Barthelmé 《Comptes Rendus Mathematique》2005,341(11):689-694
This Note introduces a new integral form of the charge and current deposition scheme given in 1992 by Villasenor and Buneman, which permits the conservation of charge in PIC codes. This integral form extends directly to higher order spline shape factors, whose use produces less numerical noise. We thus get a discrete charge conserving method for high order shape factors. This method extends easily to nonuniform Cartesian grids for first order shape factors. To cite this article: R. Barthelmé, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献
23.
Tereza C. R. dos Santos Ricardo Q. Aucélio Reinaldo C. Campos 《Mikrochimica acta》2003,142(1-2):63-66
A simple and direct spectrofluorimetric method has been developed for the determination of aluminum using alizarin red PS
(1,2,4-trihydroxy 9,10-anthraquinone-3-sulfonic acid). The method is based on the strong fluorescence (480/564 nm) of Al3+ and alizarin red. Experimental parameters such as pH, concentration of the ligand, ionic strength of the solution, reaction
time and temperature were optimized in order to maximize the analytical signal. Interferences of several ions (anions and
cations) were studied and evaluated. The linear range of the method extends from 3 to 100 μg L−1. Limit of detection (3sb) was 0.9 μg L−1. The method was tested with a silicate certified reference material. Interferences were eliminated by a liquid extraction
with cupferron.
Author for correspondence. E-mail: aucelior@rdc.puc-rio.br
Received September 10, 2002; accepted January 15, 2003
Published online May 5, 2003 相似文献
24.
C Guéret N Jussien O Lhomme C Pavageau C Prins 《The Journal of the Operational Research Society》2003,54(5):458-465
In this paper, we describe an aircraft loading problem submitted by the French military agency (DGA) as part of a more general military airlift planning problem. It can be viewed as a kind of bi-dimensional bin-packing problem, with heterogeneous bins and several additional constraints. We introduce two-phase methods for solving this NP-hard problem. The first phase consists in building good initial solutions, thanks to two fast algorithms: a list-based heuristic and a loading pattern generation method. Both algorithms call a constraint-based subroutine, able to determine quickly if the items already loaded can be reshuffled to accommodate a new object. The second phase improves these preliminary solutions using local search techniques. Results obtained on real data sets are presented. 相似文献
25.
Various physical systems of dispersive waves admit solutions in the form of generalized solitary waves. Such waves result from the resonance between a long localized wave and short periodic oscillations. Many estimates (rigorous and numerical) have been given for the amplitude of the ripples in the tail of the generalized solitary wave when its central part has a sech2 shape. This Note provides estimates (not yet rigorous) for the ripple amplitude when the central part is flat and wide. To cite this article: C. Fochesato, F. Dias, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
26.
Biosorption of Chromium(III) by Biomass of Seaweed Sargassum sp. in a Fixed-Bed Column 总被引:2,自引:0,他引:2
Eneida Sala Cossich Edson Antonio da Silva Célia Regina Granhen Tavares Lúcio Cardozo Filho Teresa Massako Kakuta Ravagnani 《Adsorption》2004,10(2):129-138
This work aimed at modeling chromium biosorption using the biomass of seaweed Sargassum sp. in a fixed-bed column. The mathematical model used was obtained from the mass balance of the component in the liquid phase and in the biosorbent material. The effects of both axial dispersion in the column and the resistance to mass transfer in the solid were considered for the solution of the partial differential equations of the model, using the Galerkin method on finite elements. To represent the equilibrium data of the batch system the Langmuir isotherm were used. The chromium ion adsorption capacity of the seaweed Sargassum sp., at a temperature of 30°C and pH 3.5, was 2.61 mmol/g. The model performance was evaluated from experimental data obtained at 30°C for flow rates of 2, 6 and 8 mL/min. The parameters of the model, mass transfer and axial dispersion coefficients, were adjusted from these experimental data. The model proved adequate to describe chromium biosorption dynamics in fixed-bed columns. 相似文献
27.
28.
5,6-Dihydro-OSW-1 (1) was synthesized following our previous procedure for the total synthesis of OSW-1. This compound demonstrated slightly stronger potency than that of OSW-1 against the growth of cancer cells. 相似文献
29.
We deal with MAXH0-FREE PARTIAL SUBGRAPH. We mainly prove that 3-locally optimum solutions achieve approximation ratio (δ0+1)/(B+2+ν0), where B=maxv∈VdG(v), δ0=minv∈V(H0)dH0(v) and ν0=(|V(H0)|+1)/δ0. Next, we show that this ratio rises up to 3/(B+1) when H0=K3. Finally, we provide hardness results for MAXK3-FREE PARTIAL SUBGRAPH. 相似文献
30.
Ricardo Mañé 《Bulletin of the Brazilian Mathematical Society》1997,28(2):141-153
The objective of this note is to present some results, to be proved in a forthcoming paper, about certain special solutions of the Euler-Lagrange equations on closed manifolds. Our main results extend to time dependent periodic Lagrangians with minor modifications.We have chosen the autonomous case because this formally simpler framework allows to reach more easily the core of our concepts and results. Moreover the autonomous case exhibits certain special features involving the energy as a first integral that deserve special attention. They are closely related to the link found by Carneiro [C] between the energy and Mather's action function [Ma].Reprinted by permission of Addison Wesley Longman Ltd. 相似文献