全文获取类型
收费全文 | 455篇 |
免费 | 8篇 |
国内免费 | 3篇 |
专业分类
化学 | 238篇 |
晶体学 | 1篇 |
力学 | 37篇 |
数学 | 123篇 |
物理学 | 67篇 |
出版年
2023年 | 1篇 |
2022年 | 11篇 |
2021年 | 19篇 |
2020年 | 15篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 18篇 |
2014年 | 15篇 |
2013年 | 46篇 |
2012年 | 24篇 |
2011年 | 35篇 |
2010年 | 22篇 |
2009年 | 20篇 |
2008年 | 21篇 |
2007年 | 17篇 |
2006年 | 15篇 |
2005年 | 21篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 5篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1940年 | 2篇 |
排序方式: 共有466条查询结果,搜索用时 15 毫秒
381.
382.
Nicolas Gogibus Ulrich Maschke Farida Benmouna Bernd Ewen Xavier Coqueret Mustapha Benmouna 《Journal of Polymer Science.Polymer Physics》2001,39(5):581-588
The phase diagrams of poly(dimethylsiloxane) (PDMS) and 4‐cyano‐4′‐n‐pentyl‐biphenyl (5CB) mixtures are studied for two systems of different molecular weights of the polymer. The experimental diagrams are established by polarized optical microscopy (POM), and analyzed using a combination of the Flory–Huggins theory of isotropic mixing and the Maier–Saupe theory of nematic order. The results are compared with those of polystyrene (PS) and 4‐cyano‐4′‐n‐octyl‐biphenyl (8CB) with analogous molecular weight of the polymer. This investigation could be useful for the choice of systems in electro‐optical devices. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 581–588, 2001 相似文献
383.
An observation of palladium membrane formation on a porous stainless steel substrate by electroless deposition 总被引:4,自引:0,他引:4
Zhongliang Shi Shanqiang Wu Jerzy A Szpunar Mustapha Roshd 《Journal of membrane science》2006,280(1-2):705-711
The membranes made of palladium and its alloys are used for the extraction of high quality hydrogen from a mixture of gases. Most of recent research is focused on the development technologies for depositing a durable ultra-thin palladium membrane on a porous substrate in order to assure a good mechanical support and maximize the flux of hydrogen permeation. The formation of a palladium membrane deposited on a porous stainless steel substrate by an electroless process is recorded and described in this paper. The palladium deposition progress around the pore area at the surface of the substrate in the initial stages is illustrated. A bridge model is presented to describe the membrane formation around the pore area of the substrate. This model, together with the micrographs showing the deposition progress on the pore areas, will lead to the control of the deposition process for a membrane fabrication as well as the design and modification of a substrate. 相似文献
384.
Romerosa A Campos-Malpartida T Lidrissi C Saoud M Serrano-Ruiz M Peruzzini M Garrido-Cárdenas JA García-Maroto F 《Inorganic chemistry》2006,45(3):1289-1298
The new water-soluble ruthenium(II) chiral complexes [RuCpX(L)(L')](n+) (X = Cl, I. L = PPh3; L' = PTA, mPTA; L = L' = PTA, mPTA) (PTA = 1,3,5-triaza-7-phosphaadamantane; mPTA = N-methyl-1,3,5-triaza-7-phosphaadamantane) have been synthesized and characterized by NMR and IR spectroscopy and elemental analysis. The salt mPTA(OSO2CF3) was also prepared and fully characterized by spectroscopic techniques. X-ray crystal structures of [RuClCp(PPh3)(PTA)] (2), [RuCpI(PPh3)(PTA)] (3), and [RuCpI(mPTA)(PPh3)](OSO2CF3) (9) have been determined. The binding properties toward DNA of the new hydrosoluble complexes have been studied using the mobility shift assay. The ruthenium chloride complexes interact with DNA depending on the hydrosoluble phosphine bonded to the metal, while the corresponding compounds with iodide, [RuCpI(PTA)2] (1), [RuCpI(PPh3)(PTA)] (3), [RuCpI(mPTA)2](OSO2CF3)2 (6), and [RuCpI(mPTA)(PPh3)](OSO2CF3) (9), do not bind to DNA. 相似文献
385.
Valter Castelvetro Mustapha RaihaneSabrina Bianchi Salima AtlasIlaria Bonaduce 《Polymer Degradation and Stability》2011,96(2):204-211
The thermal decomposition under non-oxidative conditions of a copolymer of vinylidene cyanide (VCN) and 2,2,2-trifluoroethyl methacrylate (MATRIF) was investigated by thermogravimetry (TG) and Pyrolysis-GC-MS. The type and composition of the pyrolytic products and the shape of the TG curve indicate that both the main thermal degradation process, with onset at 368 °C, and a minor weight loss at around 222 °C are mainly associated with random main-chain scission. The kinetic parameters were determined by means of dynamic and, in the case of the main degradation stage, also isothermal methods. The results obtained from the dynamic methods (Friedman, Flynn-Wall-Ozawa, and Kissinger, respectively) are in good agreement with those obtained from isothermal TG data. The activation energy was in the 177-213 kJ/mol range for the first stage, and 224-295 kJ/mol for the second stage, the highest respective values being determined from the kinetic analysis according to the Kissinger method. 相似文献
386.
Mustapha Bouakba Abderrezak Bezazi Fabrizio Scarpa 《International Journal of Solids and Structures》2012,49(18):2450-2459
This work presents a novel formulation for a Voronoi-type cellular material with in-plane anisotropic behaviour, showing global positive and negative Poisson’s ratio effects under uniaxial tensile loading. The effects of the cell geometry and relative density over the global stiffness, equivalent in-plane Poisson’s ratios and shear modulus of the Voronoi-type structure are evaluated with a parametric analysis. Empirical formulas are identified to reproduce the mechanical trends of the equivalent homogeneous orthotropic material representing the Voronoi-type structure and its geometry parameters. 相似文献
387.
The flow characteristics of an unsteady axisymmetric two-dimensional (2D) blood flow in a diseased porous arterial segment
with flexible walls are investigated. The arterial walls mimic the irregular constrictions whereas the lumen containing the
thrombus, cholesterol, and fatty plaques represents the porous medium. The governing equations with appropriate initial and
boundary conditions are solved numerically using MAC method. The discretization is done on staggered grid with non-uniform
grid size and pressure-poisson equation is solved following SOR method. The pressure and velocity corrections are made cyclically
until the steady state is achieved. It is observed that for decreasing permeability, flow is highly decelerated while pressure
drop and wall shear stress increases. The separation zones and re-circulation regions are found for severe stenoses. Flow
separation and re-circulation diminishes for decreasing permeability of the porous medium. Comparisons are provided with published
experimental and numerical results. 相似文献
388.
Isomerisation reactions of 1-phenyl 1-butanone X+? () and five other C10H12O+? ions are demonstrated to proceed via a single intennediate (); the H2O elimination occurs from the tetralol structure (). 相似文献
389.
Sami Mustapha 《Comptes Rendus Mathematique》2006,342(1):11-15
We give a version of the SAK-Fefferman principle which allows us to compare powers of subelliptic pseudo-differential operators in the setting of Weyl–Hörmander calculus. To cite this article: S. Mustapha, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
390.
Mustapha Rachdi 《Comptes Rendus Mathematique》2003,337(7):487-492
Let be a continuous-time strictly stationary and strongly mixing process. In this paper, we prove in the setting of spectral density estimation, at first, under some hard conditions on the spectral density φX (because of aliasing phenomenon), the uniformly complete convergence of the spectral density estimate from periodic sampling. Afterwards, to overcome aliasing, we consider the sampled process , where {tn} is a stationary point process independent from X. The uniform complete convergence of the spectral estimate based on the discrete time observations {X(tk),tk} is also obtained. The convergence rates are also established. To cite this article: M. Rachdi, C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献