全文获取类型
收费全文 | 624篇 |
免费 | 29篇 |
国内免费 | 4篇 |
专业分类
化学 | 365篇 |
晶体学 | 1篇 |
力学 | 52篇 |
数学 | 132篇 |
物理学 | 107篇 |
出版年
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 24篇 |
2020年 | 10篇 |
2019年 | 23篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 31篇 |
2015年 | 30篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 42篇 |
2011年 | 53篇 |
2010年 | 27篇 |
2009年 | 30篇 |
2008年 | 53篇 |
2007年 | 44篇 |
2006年 | 38篇 |
2005年 | 34篇 |
2004年 | 26篇 |
2003年 | 15篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有657条查询结果,搜索用时 15 毫秒
71.
In this paper, we propose a two-phased local search for vertex coloring. The algorithm alternately executes two closely interacting functionalities, i.e., a stochastic and a deterministic local search. The stochastic phase is basically based on biased random sampling that, according to a probability matrix storing the probability a vertex can be assigned to a color, iteratively constructs feasible colorings. The deterministic phase, instead, consists in assigning sequentially, according to a given ordering, each vertex to the color which causes the lowest increase of the solution penalty, and then, when the schedule is constructed, swap operations are executed to improve the performance. The interaction between the two phases is implemented by tunnelling information of what happened during a phase to the successive ones. Beyond the algorithm scheme, the novelty of the approach stems from the fact that the objective function is not minimizing the number of colors but a new penalty function. The proposed approach is tested on known benchmarks for the studied problem available on the public domain. From a comparison to the state of the art it appears that the proposed approach is robust and is able to achieve best known results. 相似文献
72.
Two novel azulene chromophores 1 and 2 were synthesized to study dynamics of ultrafast electron injection at the interface of TiO2 semiconductor nanoparticles. Fluorescence quenching was observed upon binding. 相似文献
73.
Roccatano D Sbardella G Aschi M Amicosante G Bossa C Di Nola A Mazza F 《Journal of computer-aided molecular design》2005,19(5):329-340
The dynamical aspects of the fully hydrated TEM-1 β-lactamase have been determined by a 5 ns Molecular Dynamics simulation.
Starting from the crystallographic coordinates, the protein shows a relaxation in water with an overall root mean square deviation
from the crystal structure increasing up to 0.17 nm, within the first nanosecond. Then a plateau is reached and the molecule
fluctuates around an equilibrium conformation. The results obtained in the first nanosecond are in agreement with those of
a previous simulation (Diaz et al., J. Am. Chem. Soc., (2003) 125, 672–684). The successive equilibrium conformation in solution
shows an increased mobility characterized by the following aspects. A flap-like translational motion anchores the Ω-loop to
the body of the enzyme. A relevant part of the backbone dynamics implies a rotational motion of one domain relative to the
other. The water molecules in the active site can exchange with different residence times. The H-bonding networks formed by
the catalytic residues are frequently interrupted by water molecules that could favour proton transfer reactions. An additional
simulation, where the aspartyl dyad D214–D233 was considered fully deprotonated, shows that the active site is destabilized. 相似文献
74.
75.
Amadei A D'Alessandro M Paci M Di Nola A Aschi M 《The journal of physical chemistry. B》2006,110(14):7538-7544
In this paper, we investigate the effects of a point mutation on the enzymatic activity of copper-zinc superoxide dismutase, which we recently studied in detail by means of a theoretical-computational procedure. Comparison of the reactivity of the initial catalytic steps in this mutant (G93A mutation far from the active site) with our previous data, reveals the beautiful mechanical-dynamical architecture of the enzyme, altered by such an apparently irrelevant mutation. Finally, our results suggest a possible atomic-molecular-based explanation for the mutant-pathology correlation, in line with the most recent experimental data. 相似文献
76.
Cavallini M Gomez-Segura J Albonetti C Ruiz-Molina D Veciana J Biscarini F 《The journal of physical chemistry. B》2006,110(24):11607-11610
We report a new patterning process which takes place as a result of demixing of a binary polymer/solute mixture. An efficient, sustainable approach for ordering nanosized rings of so-called single molecule magnets (SMMs) is thus provided. It exploits the self-organization process in which SMM patterned film evolves to a spatially correlated pattern of nanosized rings. At long time, the anisotropic patterning of the film drives the ring to coalesce, into parallel lines of nanometric width. 相似文献
77.
Taglienti A Cellesi F Crescenzi V Sequi P Valentini M Tirelli N 《Macromolecular bioscience》2006,6(8):611-622
[Chemical structure: see text] The interactions between a biomaterial and biomolecules present in body fluids often determine the fate of the biomaterial. This paper presents a study on hyaluronan (HA)-containing materials (in soluble or colloidal form) that focuses on their interactions with lipids and proteins and for the first time uses PFG NMR as an analytical technique for probing these events. The interactions of HA-based polymers with phospholipids (DPPC and DPPG liposomes) are shown to depend both on charge and hydrophobicity factors. Despite the difference in behavior between albumin (substantially non-adhesive) and fibrinogen (adhesive), the interactions of the polymers with proteins do not seem to be based on hydrophobic effects but on surface polar interactions. 相似文献
78.
79.
Massimiliano Ferronato Nicola CastellettoGiuseppe Gambolati 《Journal of computational physics》2010,229(12):4813-4830
The numerical solution to the Biot equations of 3-D consolidation is still a challenging task because of the ill-conditioning of the resulting algebraic system and the instabilities that may affect the pore pressure solution. Recently new approaches have been advanced based on mixed formulations. In the present paper a fully coupled 3-D mixed finite element model is developed with the aim at alleviating the pore pressure numerical oscillations at the interface between materials with different permeabilities. A solution algorithm is implemented that takes advantage of the block structure of the discretized problem. The proposed model is verified against well-known analytical solutions and successfully experimented with in realistic applications of soil consolidation. 相似文献
80.
We study light propagation in nanoscale periodic structures composed of dielectric and metal in the visible range. We demonstrate that diffraction curves of nonuniform waveguide arrays can be tailored by varying the geometric and dielectric features of the waveguides. The results obtained from a proper formulation of coupled mode theory for nonuniform arrays are validated through numerical solution of Maxwell equations in frequency domain. 相似文献