全文获取类型
收费全文 | 274篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 156篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 17篇 |
物理学 | 98篇 |
出版年
2023年 | 1篇 |
2022年 | 12篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2018年 | 7篇 |
2017年 | 2篇 |
2016年 | 19篇 |
2015年 | 2篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 19篇 |
2011年 | 10篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 20篇 |
2007年 | 16篇 |
2006年 | 9篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1962年 | 1篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1937年 | 2篇 |
排序方式: 共有280条查询结果,搜索用时 0 毫秒
101.
102.
Papadopoulos P Deng X Mammen L Drotlef DM Battagliarin G Li C Müllen K Landfester K del Campo A Butt HJ Vollmer D 《Langmuir : the ACS journal of surfaces and colloids》2012,28(22):8392-8398
Describing wetting of a liquid on a rough or structured surface is a challenge because of the wide range of involved length scales. Nano- and micrometer-sized textures cause pinning of the contact line, reflected in a hysteresis of the contact angle. To investigate contact angles at different length scales, we imaged water drops on arrays of 5 μm high poly(dimethylsiloxane) micropillars. The drops were imaged by laser scanning confocal microscopy (LSCM), which allowed us to quantitatively analyze the local and large-scale drop profile simultaneously. Deviations of the shape of drops from a sphere decay at two different length scales. Close to the pillars, the amplitude of deviations decays exponentially within 1-2 μm. The drop profile approached a sphere at a length scale 1 order of magnitude larger than the pillars' height. The height and position dependence of the contact angles can be understood from the interplay of pinning of the contact line, the principal curvatures set by the topography of the substrate, and the minimization of the air-water interfaces. 相似文献
103.
In order to study the effect of sharp edges on solid particle adhesion to air-liquid interfaces, spherical colloidal probes were modified with a circumferential cut by focused ion beam milling. The interaction of the modified particles with water drops and bubbles was studied using the colloidal probe technique. When the modified particles were brought into contact with air-liquid interfaces, the contact line was pinned at the edge of the cut. Contact hysteresis between the approach and retraction components of the measured force curves was eliminated. The contact angle at the edge takes a range of values within the limits defined by the Gibbs inequality. These limits determine the adhesion force. As such, the adhesion force is a function of the particle wettability and edge geometry. 相似文献
104.
In the last two decades fluorescence correlation spectroscopy (FCS) has been increasingly applied to analyze systems and processes relevant to colloid and interface science. The method has become a routine tool to measure the hydrodynamic radii of small fluorescent molecules, macromolecules and nanoparticles, characterize their interactions and follow a possible aggregation. It was also used to study the diffusion of such species in inhomogeneous media like polymer melts, solutions, gels or porous structures. The formation kinetics and size of micelles of surfactants or block copolymers has been quantified. FCS has also been applied to characterize diffusion of tracers at fluid–liquid and solid–liquid interfaces and study the hydrodynamic boundary condition. The review is intended to summarize these applications and highlight perspectives but also limits of FCS in colloid and interface science. 相似文献
105.
This article reports the microstructural characteristics of various petroleum and pitch based nuclear graphites (IG-110, NBG-18, and PCEA) that are of interest to the next generation nuclear plant program. Bright-field transmission electron microscopy imaging was used to identify and understand the different features constituting the microstructure of nuclear graphite such as the filler particles, microcracks, binder phase, rosette-shaped quinoline insoluble (QI) particles, chaotic structures, and turbostratic graphite phase. The dimensions of microcracks were found to vary from a few nanometers to tens of microns. Furthermore, the microcracks were found to be filled with amorphous carbon of unknown origin. The pitch coke based graphite (NBG-18) was found to contain higher concentration of binder phase constituting QI particles as well as chaotic structures. The turbostratic graphite, present in all of the grades, was identified through their elliptical diffraction patterns. The difference in the microstructure has been analyzed in view of their processing conditions. 相似文献
106.
P. Buttà R. Esposito A. Giuliani R. Marra 《Communications in Mathematical Physics》2013,322(2):593-632
We investigate the ground and low energy states of a one dimensional non-local free energy functional describing at a mean field level a spin system with both ferromagnetic and antiferromagnetic interactions. In particular, the antiferromagnetic interaction is assumed to have a range much larger than the ferromagnetic one. The competition between these two effects is expected to lead to the spontaneous emergence of a regular alternation of long intervals on which the spin profile is magnetized either up or down, with an oscillation scale intermediate between the range of the ferromagnetic and that of the antiferromagnetic interaction. In this sense, the optimal or quasi-optimal profiles are “froth-like”: if seen on the scale of the antiferromagnetic potential they look neutral, but if seen at the microscope they actually consist of big bubbles of two different phases alternating among each other. In this paper we prove the validity of this picture, we compute the oscillation scale of the quasi-optimal profiles and we quantify their distance in norm from a reference periodic profile. The proof consists of two main steps: we first coarse grain the system on a scale intermediate between the range of the ferromagnetic potential and the expected optimal oscillation scale; in this way we reduce the original functional to an effective “sharp interface” one. Next, we study the latter by reflection positivity methods, which require as a key ingredient the exact locality of the short range term. Our proof has the conceptual interest of combining coarse graining with reflection positivity methods, an idea that is presumably useful in much more general contexts than the one studied here. 相似文献
107.
Ralf?S.?KappesEmail author Friedhelm?Sch?nfeld Chen?Li Jochen?S.?Gutmann Hans-Jürgen?Butt 《Applied Physics A: Materials Science & Processing》2012,106(4):791-801
To investigate the temperature profiles on laser heated polymer films, we track the thermal radiation with 1 μs time and 1
μm spatial resolution. The resulting two-dimensional temperature graphs are compared to finite element simulations in order
to understand the heat conversion and flow. The temperature measurement setup consists of a NIR laser and an optical detection
system, which includes high performance optics and a microsecond gated camera, equipped with several interference filters.
In this way the thermal radiation is detected in the visible range with spectral resolution. Fitting the spectrum with Planck’s
law, two-dimensional micrographs of the temperature distribution are obtained. For polystyrene surfaces we were able to analyze
the heating and the ablation behavior. Good agreement was found between experimental results and finite element simulations,
when ablation is limited to a few tens of nanometers of the film thickness. Ablation of polystyrene starts at 150°C, 50 K
above the glass transition temperature. We suggest a photomechanical ablation mechanism at that threshold fluence. For ablation
at higher fluence and peak temperature, experiments indicate a thermal decomposition reaction. The temperature range of spinodal
decomposition is not reached and can in our case be ruled out as ablation mechanism. 相似文献
108.
Haider Butt Qing Dai Timothy D. Wilkinson Gehan A.J. Amaratunga 《Photonics and Nanostructures》2012,10(4):499-505
We report a novel utilization of periodic arrays of carbon nanotubes in the realization of diffractive photonic crystal lenses. Carbon nanotube arrays with nanoscale dimensions (lattice constant 400 nm and tube radius 50 nm) displayed a negative refractive index in the optical regime where the wavelength is of the order of array spacing. A detailed computational analysis of band gaps and optical transmission through the nanotubes based planar, convex and concave shaped lenses was performed. Due to the negative-index these lenses behaved in an opposite fashion compared to their conventional counter parts. A plano-concave lens was established and numerically tested, displaying ultra-small focal length of 1.5 μm (~2.3 λ) and a near diffraction-limited spot size of 400 nm (~0.61 λ). 相似文献
109.
A. S. Butt M. N. Tufail Asif Ali 《Journal of Applied Mechanics and Technical Physics》2016,57(2):283-292
A three-dimensional flow of a magnetohydrodynamic Casson fluid over an unsteady stretching surface placed into a porous medium is examined. Similarity transformations are used to convert time-dependent partial differential equations into nonlinear ordinary differential equations. The transformed equations are then solved analytically by the homotopy analysis method and numerically by the shooting technique combined with the Runge–Kutta–Fehlberg method. The results obtained by both methods are compared with available reported data. The effects of the Casson fluid parameter, magnetic field parameter, and unsteadiness parameter on the velocity and local skin friction coefficients are discussed in detail. 相似文献
110.
M. N. Tufail A. S. Butt A. Ali 《Journal of Applied Mechanics and Technical Physics》2016,57(5):900-907
An investigation has been conducted on the MHD Casson fluid and heat transfer over an unsteady stretching sheet with viscous dissipation effects. With suitable dimensionless variables, partial differential equations are reduced to ordinary differential equations, which are then solved by the homotopy analysis method. Dependences of flow characteristics on various parameters involved into the equations are obtained. 相似文献