全文获取类型
收费全文 | 145篇 |
免费 | 6篇 |
专业分类
化学 | 66篇 |
晶体学 | 1篇 |
力学 | 12篇 |
数学 | 15篇 |
物理学 | 57篇 |
出版年
2023年 | 1篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 9篇 |
2011年 | 4篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有151条查询结果,搜索用时 31 毫秒
1.
The effect of iodine sorption on the free volume of polycarbonate is investigated by Positron Annihilation Lifetime method.
The observed results are interpreted in terms of the Charge Transfer Complex formation and precipitation of iodine at the
initial and final stages of sorption, respectively. At higher levels of sorption, changes in the second lifetime and its intensity
seem to suggest a conformational transformation, probably due to the net change in the amorphous-crystalline boundary regions
of the polymer matrix. The free volume cavities have been predominantly occupied by I-
3 species and the diffusion process obeys Fick’s law. An exponential type correlation has been observed between fractional
free volume and the diffusion coefficient.
Received: 13 June 1996/Accepted: 20 September 1996 相似文献
2.
Grammaticos B. Otha Y. Ramani A. Satsuma J. Tamizhmani K. M. 《Letters in Mathematical Physics》1997,39(2):179-186
We present Miura transformations for the continuous and several discrete Painlev\'e I equations. In the case of the continuous PI, we use the Hamiltonian formulation of the Painlev\'e equations and show that there exists a Miura transformation between PI and the binomial, second degree, equation of Cosgrove SDV. In the case of the discrete PI's we obtain two different kinds of Miuras. One kind relates a d-PI to some other d-PI while the other leads to discrete four-point equations which are the discrete analogs of the derivative of Cosgrove's equation SDV. 相似文献
3.
The complexes [1,3-diphenyl-1,3-propanedionato]tricyclohexyltin(IV), (tropolonato)triphenyltin(IV), and (tropolonato)tricyclohexyltin(IV) have been prepared for the first time and have been found to be five-coordinate in the solid state. These and related five-coordinate complexes prepared previously have been studied by a variety of physical methods; 13C NMR, UV, IR, Raman, dipole moments and the Kerr effect. While all structures are demonstrably five-coordinate, and all chelates bidentate in the solid state, the geometries of two of the complexes in solution appear to vary somewhat from the expected fac or mer. There is evidence from the solution Kerr effect and 13C NMR that cyclohexyl derivatives may disproportionate. 相似文献
4.
We introduce the Schlesinger transformations for the Gambier, linearisable, equation and by combining the former construct the contiguity relations of the solutions of the latter. We extend the approach to the discrete domain obtaining thus the Schlesinger transformations and the contiguity relations of the solutions of the Gambier mapping. In all cases the resulting contiguity relation is a linearisable equation, involving free functions, and which can be related to the generic Gambier mapping. 相似文献
5.
Chetan Tambe John Kaufmann Daniel Graiver Ramani Narayan 《Journal of polymer science. Part A, Polymer chemistry》2016,54(19):3086-3093
Reactive blends prepared from methoxysilane terminated silicone polymers and silylated soybean oil are described and characterized. Although simple mixing of soy and silicones results in gross phase separation, homogeneous polymeric products are obtained by introducing reactive sites. These products can be used as protective coatings, additives to adhesives and new sealants. Exposure of the mixtures to moisture leads to hydrolysis of the methoxysilanes and subsequent condensation of the resulting silanols that yields stable siloxane linkages between the two immiscible phases. FTIR, TGA, and swell‐gel analyses indicate effective formation of these siloxane crosslinks. Reactive blends containing less than 20% silylated oil appeared completely transparent but increasing the soy content decreased the optical transparency. SEM micrographs reveal the silicone polymer as the continuous phase with individual spherical silylated soy oil particles distributed in it. The properties of these reactive blends vary from high elongation elastomers to high modulus resins depending on the composition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3086–3093 相似文献
6.
Treatment of α,β-unsaturated esters with triethylsilane in benzene in the presence of a catalytic amount of tris(triphenylphosphine)rhodium chloride at room temperature followed by chromatography on silica gel gave rise to the corresponding saturated esters. Under similar conditions, fully conjugated diene esters were reduced to the dihydrolevel to give β,γ- or γ,δ-unsaturated esters depending upon the substitution pattern of the starting substrate. 相似文献
7.
8.
Prediction of stagnation point heat transfer for a single round jet impinging on a concave hemispherical surface 总被引:1,自引:0,他引:1
This paper deals with a systematic procedure for assessment of fluid flow and heat transfer parameters for a single round jet impinging on a concave hemispherical surface. Based on Scholkemeier's modifications of the Karman-Pohlhausen integral method, expressions are derived for evaluation of the momentum thickness, boundary layer thickness and the displacement thickness at the stagnation point. This is followed by the estimation of thermal boundary layer thickness and local heat transfer coefficients. A correlation is presented for the Nusselt number at the stagnation point as a function of the Reynolds number for different non-dimensional distances from the exit plane of the jet to the impingement surface.
Nomenclature c p specific heat at constant pressure - d diameter of single round nozzle - h 0 heat transfer coefficient at the stagnation point - H distance from the exit plane of the jet to the impingement surface - k thermal conductivity - Nu 0.5 Nusselt number based on impinging jet quantities=h 0.50/k - Nu 0.5, 0 stagnation point Nusselt number=h 0 0,50/k - p pressure - p a ambient pressure - p 0 maximum pressure or stagnation pressure - p(x) static pressure at a distancex from the stagnation point - R radius of curvature of the hemisphere - Re J jet Reynolds number=U Jd/ - Re 0.5 Reynolds number based on impinging jet quantities=u m0 0.50/ - T temperature - T a room temperature - T J jet temperature - T W wall temperature - u velocity component inx andx directions (Fig. 1) - u m jet centerline (or maximum) free jet velocity: external (or maximum) boundary layer velocity aty= m - u m0 arrival velocity defined as the maximum velocity the free jet would have at the plane of impingement if the plane were not there - U J jet exit velocity - x* non-dimensional coordinate starting at the stagnation point=x/2 0.50 - x, y rectangular Cartesian coordinates - y coordinate normal to the wall starting at the wall - ratio of thermal to velocity boundary layer thickness= T/m - 0 ratio of thermal to velocity boundary layer thickness at the stagnation point - * inner layer displacement thickness - 0.50 jet half width at the plane of impingement if the plate were not there - m inner boundary layer thickness atu=u m - Pohlhausen's form parameter - dynamic viscosity - kinematic viscosity=/ - fluid density - momentum thickness - 0 momentum thickness at the stagnation point 相似文献
Bestimmung des Staupunktes bei der Wärmeübertragung für einen einzelnen Strahl, der auf eine konkave halbkugelige Oberfläche trifft
Zusammenfassung Diese Arbeit beschäftigt sich mit dem systematischen Verfahren der Bewertung von Fluidströmungen und Wärmeübertragungsparametern für einen einzelnen runden Strahl, der auf eine konkave halbkugelförmige Oberfläche trifft. Das Verfahren beruht auf Scholkemeiers Modifikation des Karman-Pohlhausen Integrationsverfahrens. Ausdrücke sind für die Berechnung der Impuls-Dicke, der Grenzschichtdicke und der Verschiebungsdicke am Staupunkt hergeleitet worden. Dies ist aus der Berechnung der thermischen Grenzschichtdicke und des lokalen Wärmeübertragungskoeffizienten abgeleitet worden. Es wird eine Gleichung für die Nusselt-Zahl am Staupunkt als Funktion der Reynolds-Zahl für verschiedene dimensionslose Abstände vom Strahlaustrittspunkt bis zum Auftreffpunkt auf die Oberfläche vorgestellt.
Nomenclature c p specific heat at constant pressure - d diameter of single round nozzle - h 0 heat transfer coefficient at the stagnation point - H distance from the exit plane of the jet to the impingement surface - k thermal conductivity - Nu 0.5 Nusselt number based on impinging jet quantities=h 0.50/k - Nu 0.5, 0 stagnation point Nusselt number=h 0 0,50/k - p pressure - p a ambient pressure - p 0 maximum pressure or stagnation pressure - p(x) static pressure at a distancex from the stagnation point - R radius of curvature of the hemisphere - Re J jet Reynolds number=U Jd/ - Re 0.5 Reynolds number based on impinging jet quantities=u m0 0.50/ - T temperature - T a room temperature - T J jet temperature - T W wall temperature - u velocity component inx andx directions (Fig. 1) - u m jet centerline (or maximum) free jet velocity: external (or maximum) boundary layer velocity aty= m - u m0 arrival velocity defined as the maximum velocity the free jet would have at the plane of impingement if the plane were not there - U J jet exit velocity - x* non-dimensional coordinate starting at the stagnation point=x/2 0.50 - x, y rectangular Cartesian coordinates - y coordinate normal to the wall starting at the wall - ratio of thermal to velocity boundary layer thickness= T/m - 0 ratio of thermal to velocity boundary layer thickness at the stagnation point - * inner layer displacement thickness - 0.50 jet half width at the plane of impingement if the plate were not there - m inner boundary layer thickness atu=u m - Pohlhausen's form parameter - dynamic viscosity - kinematic viscosity=/ - fluid density - momentum thickness - 0 momentum thickness at the stagnation point 相似文献
9.
An experimental investigation is made to study the flow characteristics of slot jet impingement on a cylinder. The velocity profiles and pressure distribution around the cylinder are reported for various parameters namely, the flow rate, width of the nozzle, distance of the cylinder from the jet exit and eccentricity of the cylinder to the jet axis.
Nomenclature B breadth of the nozzle at the exit - D diameter of the cylinder - C p pressure coefficient - g acceleration due to gravity - L distance of the cylinder from jet exit - P a atmospheric pressure - P c static pressure along the jet center-line - P 0 stagnation pressure - P W wall static pressure - Re D Reynolds numberu j D/ a - Re W Reynolds numberu j W/ a - r distance measured from cylinder surface in radial direction - r m position of maximum velocity from cylinder surface - r 0.5 half width of the jet - u mean velocity - u j mean velocity at the jet exit - u m maximum velocity - W width of the nozzle - a density of air - m density of mercury - w density of water - absolute viscosity - kinematic viscosity 相似文献
Experimentelle Untersuchung über die Strömungseigenschaften eines Düsenstrahls, der auf einen Zylinder aufprallt
Zusammenfassung Es wurde eine experimentelle Untersuchung gemacht, um die Strömungseigenschaften eines Düsenstrahls zu unterschen, der auf einen Zylinder prallt. Die Geschwindigkeitsprofile und die Druckverteilungen an dem Zylinder wurden für unterschiedliche Parameter dokumentiert. Die Parameter sind die Strömungsgeschwindigkeit, Düsengröße, Abstand zwischen Zylinder und Strahlaustritt und die Exzentrizität von Zylinder und Strahlachse.
Nomenclature B breadth of the nozzle at the exit - D diameter of the cylinder - C p pressure coefficient - g acceleration due to gravity - L distance of the cylinder from jet exit - P a atmospheric pressure - P c static pressure along the jet center-line - P 0 stagnation pressure - P W wall static pressure - Re D Reynolds numberu j D/ a - Re W Reynolds numberu j W/ a - r distance measured from cylinder surface in radial direction - r m position of maximum velocity from cylinder surface - r 0.5 half width of the jet - u mean velocity - u j mean velocity at the jet exit - u m maximum velocity - W width of the nozzle - a density of air - m density of mercury - w density of water - absolute viscosity - kinematic viscosity 相似文献
10.
Robert D. Bongard Michael Lepley Khushabu Thakur Marat R. Talipov Jaladhi Nayak Rachel A. Jones Lipinski Chris Bohl Noreena Sweeney Ramani Ramchandran Rajendra Rathore Daniel S. Sem 《BMC biochemistry》2017,18(1):10