全文获取类型
收费全文 | 746篇 |
免费 | 26篇 |
国内免费 | 3篇 |
专业分类
化学 | 508篇 |
晶体学 | 4篇 |
力学 | 25篇 |
数学 | 80篇 |
物理学 | 158篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 16篇 |
2021年 | 22篇 |
2020年 | 25篇 |
2019年 | 17篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 36篇 |
2015年 | 27篇 |
2014年 | 36篇 |
2013年 | 45篇 |
2012年 | 43篇 |
2011年 | 52篇 |
2010年 | 15篇 |
2009年 | 42篇 |
2008年 | 36篇 |
2007年 | 48篇 |
2006年 | 32篇 |
2005年 | 27篇 |
2004年 | 26篇 |
2003年 | 14篇 |
2002年 | 20篇 |
2001年 | 24篇 |
2000年 | 18篇 |
1999年 | 17篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 9篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有775条查询结果,搜索用时 15 毫秒
91.
A multicomponent reacting gas with an arbitrary number of chemical species and one reversible reaction is studied at a kinetic level in the frame of discrete velocity models of the Boltzmann equation, with the main objective of deriving the reactive Navier Stokes equations of the model, and characterizing the dissipative terms related to shear viscosity, thermal conductivity and thermal diffusion. The closure of the system formed by conservation and chemical rate equations is based on a first-order Chapman-Enskog method, to be applied in the strong reaction regime, and on a convenient representation of the density vector space in terms of the macroscopic variables. A mathematical procedure is proposed which leads to identification of the transport coefficients, and may be applied to a quite large variety of reactive gas flows. Moreover, it allows characterization of the functional form of the transport coefficients in dependence on the local gas concentrations, once the model is specified.Received: 4 October 2004, Accepted: 3 December 2004, Published online: 18 March 2005PACS:
51.10. + y, 51.20. + d, 47.70.Fw
Correspondence to: A.J. Soares 相似文献
92.
A class of Bianchi IX cosmological models is shown to have chaotic gravitational collapse, due to Poincaré's homoclinic phenomena. We can program such models so that for any given positive integer N (N=∞ included) the universe undergoes N non-periodic oscillations (each oscillation requiring a long time) before collapsing. For N=∞ the universe undergoes periodic oscillations. 相似文献
93.
Rodríguez-Redondo JL Sastre-Santos A Fernández-Lázaro F Soares D Azzellini GC Elliott B Echegoyen L 《Chemical communications (Cambridge, England)》2006,(12):1265-1267
A photoswitchable azobenzene-phthalocyanine-azobenzene triad has been synthesized and its electrochemical properties determined. Energy transfer among the subunits allows for modification of the E-Z ratio by selective excitation of the phthalocyanine moiety. 相似文献
94.
F. H. M. Cavalcante M. R. Gomes A. W. Carbonari L. F. D. Pereira D. A. Rossetto M. S. Costa L. M. Redondo J. Mestnik-Filho R. N. Saxena J. C. Soares 《Hyperfine Interactions》2010,198(1-3):41-45
The hyperfine field at 181Ta lattice sites in nanostructured HfO2 thin films was studied by the Perturbed Angular Correlation (PAC) technique. Thin oxide films were deposited by Electron Beam Evaporation on a silicon substrate. The thickness of the films was ~100 nm and ~250 nm. Radioactive 181Hf nuclei were produced by neutron activation of the film samples in the Brazilian Research Reactor (IPEN IEA-R1) by the reaction 180Hf(n,γ)181Hf. PAC measurements were carried out after annealing at 1473 K. The PAC technique allows the determination of the electric field gradient (EFG) at the probe sites. 相似文献
95.
Lopes SC Soares CM Baptista AM Goormaghtigh E Cabral BJ Castanho MA 《The journal of physical chemistry. B》2006,110(7):3385-3394
The analgesic dipeptide kyotorphin (L-Tyr-L-Arg) and an acylated kyotorphin derivative were studied by a combination of theoretical (molecular dynamics simulation and quantum mechanics methods) and experimental (fluorescence and infrared spectroscopies) approaches both in solution and in model systems of membranes. At biological pH the peptides have a neutral net charge. Nevertheless, their phenolic rings interact with phospholipid molecules (partition coefficient varies from 6 x 10(2) to 2 x 10(4), depending on the lipid and pH used) despite being exposed to the aqueous bulk medium. The lowest energy transition dipole moment is displaced from the normal to the lipid bilayer by 20 degrees on average. The observed extensive interaction, pK(a), precise location, and well-defined orientation in membranes combined with the ability to discriminate rigid raftlike membrane domains suggest that kyotorphin meets the structural constraints needed for receptor-ligand interaction. The acylated kyotorphin derivative mimics kyotorphin properties and represents a promising way for entrapment in a drug carrier and transport across the blood-brain barrier. 相似文献
96.
Single crystalline SrTiO 3 samples were implanted with Er ions of 150 v keV at room temperature with fluences of 5 ‐ 10 14 and 5 ‐ 10 15 . Annealing treatments were carried out both in reducing and oxidising atmospheres to recover the implantation damage. Infrared 1.54 v m Er 3+ luminescence between the two lowest spin-orbit levels 4 I 13/2 M 4 I 15/2 as well as emission from higher excited states 4 S 3/2 M 4 I 15/2 , 4 F 9/2 M 4 I 15/2 and 4 S 3/2 M 4 I 13/2 were observed in the implanted samples with highest fluence, annealed either in air or in vacuum. Multiple site location of Er 3+ ion is discussed and compared with RBS/C and emission channelling results that indicate that Er goes to Sr and Ti sites. 相似文献
97.
98.
The mechanical properties of a rare sample of kaolinite macroscopic crystals were evaluated using instrumented indentation. The crystals were also characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy before and after heat treatment at 1100°C. The results are explained in terms of the fracture process occurring in the layered structure of kaolinite, and of the effect of roughness on the hardness and elastic modulus. Data analysis using One-way ANOVA (p?<?0.05) showed that the values of hardness and elastic modulus obtained are statistically homogeneous. Before heat treatment, the sample was composed essentially of kaolinite, with hardness of 42?MPa and elastic modulus equal to 1.3?GPa. After calcination at 1100°C, the sample keeps its layered habit and consists of amorphous metakaolinite. The hardness increases to 360?MPa and the elastic modulus increases to 6.9?GPa. 相似文献
99.
100.