全文获取类型
收费全文 | 1705篇 |
免费 | 47篇 |
国内免费 | 9篇 |
专业分类
化学 | 1128篇 |
晶体学 | 5篇 |
力学 | 100篇 |
数学 | 234篇 |
物理学 | 294篇 |
出版年
2022年 | 30篇 |
2021年 | 39篇 |
2020年 | 14篇 |
2019年 | 17篇 |
2018年 | 27篇 |
2017年 | 21篇 |
2016年 | 41篇 |
2015年 | 38篇 |
2014年 | 47篇 |
2013年 | 76篇 |
2012年 | 99篇 |
2011年 | 112篇 |
2010年 | 65篇 |
2009年 | 64篇 |
2008年 | 93篇 |
2007年 | 97篇 |
2006年 | 79篇 |
2005年 | 87篇 |
2004年 | 68篇 |
2003年 | 75篇 |
2002年 | 67篇 |
2001年 | 24篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 28篇 |
1995年 | 15篇 |
1994年 | 21篇 |
1993年 | 17篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 15篇 |
1985年 | 11篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 12篇 |
1975年 | 9篇 |
1974年 | 11篇 |
1967年 | 7篇 |
1954年 | 8篇 |
排序方式: 共有1761条查询结果,搜索用时 0 毫秒
1.
2.
3.
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
4.
5.
We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design. 相似文献
6.
Alexander G. Ramm Alexandra B. Smirnova Angelo Favini 《Annali di Matematica Pura ed Applicata》2003,182(1):37-52
A nonlinear operator equation F(x)=0, F:H→H, in a Hilbert space is considered. Continuous Newton’s-type procedures based on a construction of a dynamical system with
the trajectory starting at some initial point x
0 and becoming asymptotically close to a solution of F(x)=0 as t→+∞ are discussed. Well-posed and ill-posed problems are investigated.
Received: June 29, 2001; in final form: February 26, 2002?Published online: February 20, 2003
This paper was finished when AGR was visiting Institute for Theoretical Physics, University of Giessen. The author thanks
DAAD for support 相似文献
7.
We demonstrate the surprising integrability of the classical Hamiltonian associated to a spin 1/2 system under periodic external fields. The one-qubit rotations generated by the dynamical evolution is, on the one hand, close to that of the rotating wave approximation (RWA), on the other hand to two different “average” systems, according to whether a certain parameter is small or large. Of particular independent interest is the fact that both the RWA and the averaging theorem are seen to hold well beyond their expected region of validity. Finally, we determine conditions for the realization of the quantum NOT operation by means of classical stroboscopic maps. 相似文献
8.
A new microwave dielectric method for studying photoinitiated chain radical polymerization processes
Carlo Carlini Francesco Ciardelli Pier Angelo Rolla Elpidio Tombari 《Journal of Polymer Science.Polymer Physics》1987,25(6):1253-1261
Measurements of both real and imaginary parts of the dielectric constant at a fixed microwave frequency have been performed on n-butyl acrylate/poly(n-butyl acrylate) mixtures. The dielectric constant of the mixtures has been compared with that of neat n-butyl acrylate during UV photoinitiated polymerization. The values of the imaginary part of the dielectric constant thus obtained have allowed determination of the instantaneous monomer concentration and verified the kinetic equation for the photoinitiated polymerization process. The limits of validity of the method as well as its capability of providing detailed kinetic information are also discussed. 相似文献
9.
Gianluigi Luppi Rodrigo J. Corrêa Angelo C. Pinto Quirinus B. Broxterman Claudia Tomasini 《Tetrahedron》2006,62(51):12017-12024
The first total synthesis of (R)-convolutamydine A has been achieved by the organocatalytic addition of acetone to 4,6-dibromoisatin. The absolute configuration was determined by single crystal X-ray diffraction. DFT studies were used to model the transition states for the aldol reaction and equilibrium geometries of the post-aldol reaction intermediates. The DFT study revealed that the aldol bond forming reaction was considerably endothermic. 相似文献
10.
Angelo Ricotta 《Mathematical Intelligencer》2003,25(4):4-7
The Mathematical Intelligencer encourages comments about the material in this issue. Letters to the editor should be sent
to the editor-in-chief, Chandler Davis. 相似文献