全文获取类型
收费全文 | 291篇 |
免费 | 12篇 |
国内免费 | 8篇 |
专业分类
化学 | 97篇 |
晶体学 | 2篇 |
力学 | 98篇 |
综合类 | 3篇 |
数学 | 11篇 |
物理学 | 100篇 |
出版年
2022年 | 4篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 23篇 |
2012年 | 7篇 |
2011年 | 6篇 |
2010年 | 7篇 |
2009年 | 16篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 11篇 |
2005年 | 11篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 16篇 |
2000年 | 11篇 |
1999年 | 12篇 |
1998年 | 15篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有311条查询结果,搜索用时 31 毫秒
71.
Electric field light scattering results on aqueous solutions of linear, flexible NaPSS at minimal ionic strength are reported.
Samples of molecular weights between 356 kg/mol and 2870 kg/mol were investigated. With increasing field strength the intensity
as a function of wavenumber develops a pronounced oscillating behaviour. Besides the well-known first peak a second maximum
is observed at the position at which a weak maximum for some samples already occurs at zero field. The overall intensity strongly
depends on the frequency of the electric field. The electro-optical effect shows a maximum at 300 kHz. Increasing the particle
concentration gives a large increase of the peak maximum, normalized to concentration. If plotted versus scattering angle the relative intensity increase is maximum for samples of medium molecular weight. The results strongly
indicate a stretching and alignment of the chains, thus leading to or enlarging the short range order of the chains.
Received 9 April 1999 and Received in final form 18 August 1999 相似文献
72.
Studies performed on strong polyelectrolytes and on a weak polyelectrolyte, sodium poly(acrylate), show that their stability
in presence of multivalent cations depends on the chemical nature of the charged side groups of the polymer. For sulfonate
groups (SO3
-) or sulfate groups (OSO3
-) phase separation generally occurs in presence of inorganic cations of valency 3 (as La3+) or larger and a resolubilization takes place at high salt concentration. The interactions of the polyelectrolyte with multivalent
cations are of electrostatic origin and the phase diagrams are weakly dependent on the chemical nature of the polymer backbone
and on the specificity of the counterions. For acrylate groups, (COO-), the phase separation was observed with inorganic cations of valency 2 (as Ca2+) or larger without resolubilization at high salt concentration. The phase separation is due to a chemical association between
cations and acrylate groups of two neighboring monomers of the same chain. This chemical association creates a hydrophobic
complex by dehydrating both monomer and cation. With organic trivalent cation, as spermidine +H3N(CH2)4NH2
+(CH2)3NH3
+, where no chemical association occurs with the charged side groups COO- or SO3
- of the polyelectrolyte, similar phase diagrams were observed whatever was the polyelectrolyte with a resolubilization at
high trivalent cation concentration.
Received 3 March 1999 and Received in final form 2 September 1999 相似文献
73.
74.
O. Theissen G. Gompper 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(1):91-100
We study the dynamics of spontaneous emulsification of an initially planar oil-water interface when surfactants are added.
The thermodynamic properties of the ternary oil-water-surfactant system are modeled by a Ginzburg-Landau-type free energy.
The lattice Boltzmann method is used to solve the dynamic equations. The dynamics is found to be governed by a complicated
interplay of convection and diffusion as the two relevant transport mechanisms. As long as the interface is almost flat, we
find the interfacial area to grow first exponentially and then linearly in time. Later finger-like structures form which grow
with a constant velocity. The tip velocity is found to increase roughly linearly with the mobility of the amphiphile, and
to decrease as with the solvent viscosity .
Received 5 January 1999 相似文献
75.
H. Stark J. Stelzer R. Bernhard 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):515-523
Recently, it was observed that water droplets suspended in a nematic liquid crystal form linear chains [Poulin et al., Science 275, 1770 (1997)]. The chaining occurs, e.g., in a large nematic drop with homeotropic boundary conditions at all the surfaces. Between each pair of water droplets a
point defect in the liquid crystalline order was found in accordance with topological constraints. This point defect causes
a repulsion between the water droplets. In our numerical investigation we limit ourselves to a chain of two droplets. For
such a complex geometry we use the method of finite elements to minimize the Frank free energy. We confirm an experimental
observation that the distance d of the point defect from the surface of a water droplet scales with the radius r of the droplet like .When the water droplets are moved apart, we find that the point defect does not stay in the middle between the droplets,
but rather forms a dipole with one of them. This confirms a theoretical model for the chaining. Analogies to a second order
phase transition are drawn. We also find the dipole when one water droplet is suspended in a bipolar nematic drop with two
boojums, i.e., surface defects at the outer boundary. Finally, we present a configuration where two droplets repel each other without a
defect between them.
Received 11 December 1998 相似文献
76.
Non-linear viscoelastic behavior of fumed silica suspensions 总被引:2,自引:0,他引:2
Suspensions of fumed silica exhibit a wide range of rheological properties depending on the nature and magnitude of the interparticle
forces. In a non-polar fluid, the particles interact through hydrogen bonding and can form a three-dimensional network. The
microstructure formation is responsible for the non-linear viscoelastic behavior of fumed silica suspensions, even at very
small strain. These non-linear rheological properties have been studied in small amplitude oscillatory experiments as a function
of particle size, surface treatment of particles, suspending medium polarity and solids concentration. The non-linear viscoelastic
behavior is characterized by a non-sinusoidal waveform of the signal response. For suspensions in a non-polar fluid, both
the elastic and the loss moduli are shown to be sensitive to the strain amplitude: the elastic modulus is decreasing with
increasing strain whereas the loss moduli is initially increasing with strain. We have chosen to examine the dissipated energy
which is clearly related to the breakup of the suspension structure. A comparison of model predictions and the experimental
data shows the limitations of these models, recently proposed in the literature to describe the behavior of colloidal suspensions.
Received: 9 March 1998 Accepted: 17 November 1998 相似文献
77.
Three test problems were simulated using five different two‐phase flow model equation sets from the open literature. The test problems chosen were a fluidized bed, a batch settling, and a horizontal jet impingement on a vertical wall. These three problems demonstrate an important cross‐section of physical phenomena, such as fluidized bed voidage oscillations, phase separation, countercurrent flow, and jet formation. The dispersed flow regime is selected for all three problems. The study was performed to assess the basic character of the five‐field equation sets responding to the same initial and boundary conditions and using the same finite difference numerical scheme. The general performance of the five equation sets was found to be similar, even though one of them was ill posed as an initial‐value problem. Broad trends are the same and quantitative differences could be assessed by examining the fine structure of the results. None of the equation sets could be entirely rejected on the basis of producing physically impossible or unacceptable results. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
78.
E. V. Korobko Prof. V. E. Dreval Z. P. Shulman V. G. Kulichikhin 《Rheologica Acta》1994,33(2):117-124
Studies have been made of concentrated (up to 60%) diatomite suspensions in transformer oil, the structure and theological properties of which depend on an applied electric field. Studies have been conducted of steady-state and transient regimes of straining involving continuous and periodic shear. The structure in such suspensions is formed in the presence of an electric field of 10–3 –102 duration. The suspensions under continuous stationary strain behave as non-Newtonian fluids with a yield stress dependent on electric intensity. Under periodic deformation conditions the test suspensions exhibit elasticity which abruptly diminishes with increasing deformation amplitude. 相似文献
79.
The non-linear instability characteristics of fiber suspensions in a plane Poiseuille flow are investigated. The evolution equation of the perturbation amplitude analogous to Landau equation is formulated and solved numerically for different fiber parameters. It is found that the equilibrium amplitude decreases with the increase of the fiber aspect ratio and volume fraction, i.e. the addition of the fibers reduces the amplitude of the perturbation, and leads to the reduction of the flow instability. This phenomenon becomes significant for large volume concentration and aspect ratio. The mechanism of the reduction of the flow instability is also analyzed by taking into account of the modification of the mean flow and the energy transfer from the mean flow to the perturbation flow. 相似文献
80.