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251.
252.
We discuss the structure and the interaction of telechelic brushes. We show that the association of functionalized chain ends
is capable of giving rise to attractive interactions between telechelic brush-covered surfaces, in contrast to conventional
repulsion. Our predictions for the interaction free energy are in agreement with experimental data.
Received 12 June 2000 and Received in final form 29 January 2001 相似文献
253.
The viscosity of In–Sb liquid alloys has been measured in the vicinity of equiatomic concentration (40–60 at.% Sb). The measurements were carried out by a torsional oscillation viscometer. Temperature dependence of viscosity coefficient shows the Arrhenius like behavior with anomalous increase near the melting temperature. It is shown that viscosity isotherms reveal a sharp maximum at equiatomic composition, which becomes smoother with temperature increase. 相似文献
254.
255.
ABC triblock copolymers of the type poly[5-(N,N-dimethylamino)isoprene]-block-polystyrene-block-poly(tert-butyl methacrylate) (AiST) were synthesized and hydrolyzed to yield poly[5-(N,N-dimethylamino)isoprene]-block-polystyrene-block-poly(methacrylic acid) (AiSA) triblock copolyampholytes. Due to a complex solubility behavior the solution properties of
these materials had to be investigated in THF/water solvent mixtures. Potentiometric titrations of AiSA triblock copolyampholytes
showed two inflection points with the A block being deprotonated prior to the Ai hydrochloride block thus forming a polyzwitterion
at the isoelectric point (iep). The aggregation behavior was studied by dynamic light scattering (DLS) and freeze-fracture/transmission
electron microscopy (TEM). Large vesicular structures with almost pH-independent radii were observed.
Received 15 March 2000 相似文献
256.
M. Castelnovo P. Sens J.-F. Joanny 《The European physical journal. E, Soft matter》2000,1(2-3):115-125
We investigate the equilibrium charge distribution along a single annealed polyelectrolyte chain under different conditions.
The coupling between the conformation of the chain and the local charge distribution is described for various solvent qualities
and salt concentration. In salt free solution, we find a slight charge depletion in the central part of the chain: the charges
accumulate at the ends. The effect is less important if salt is added to the solution since the charge inhomogeneity is localized
close to the chain ends over a distance of order of the Debye length. In the case of poor solvent conditions we find a different
charge per monomer in the beads and in the strings in the framework of the necklace model. This inhomogeneity leads to a charge
instability and a first order transition between spherical globules and elongated chains.
Received 19 March 1999 and Received in final form 2 August 1999 相似文献
257.
Relaxation patterns of long,linear, flexible,monodisperse polymers: BSW spectrum revisited 总被引:1,自引:1,他引:0
Theoretical predictions for the dynamic moduli of long, linear, flexible, monodisperse polymers are summarized and compared
with experimental observations. Surprisingly, the predicted 1/2 power scaling of the long-time modes of the relaxation spectrum
is not found in the experiments. Instead, scaling with a power of about 1/4 extends all the way up to the longest relaxation
times near τ/τ
max = 1. This is expressed in the empirical relaxation time spectrum of Baumgaertel-Schausberger-Winter, denoted as “BSW spectrum,”
and justifies a closer look at the properties of the BSW spectrum. Working with the BSW spectrum, however, is made difficult
by the fact that hypergeometric functions occur naturally in BSW-based rheological material functions. BSW provides no explicit
solutions for the dynamic moduli, G
′(ω), G
″(ω), or the relaxation modulus G(t). To overcome this problem, close approximations of simple analytical form are shown for these moduli. With these approximations,
analysis of linear viscoelastic data allows the direct determination of BSW parameters. 相似文献
258.
Monte Carlo simulations are used to study the non-uniform equilibrium charge distribution along a single annealed polyelectrolyte
chain under θ solvent conditions and with added salt. Within a range of the order of the Debye length charge accumulates at
chain ends while a slight charge depletion appears in the central part of the chain. The simulation results are compared with
theoretical predictions recently given by Castelnovo et al. In the parameter range where the theory can be applied we find almost perfect quantitative agreement.
Received 7 March 2002 and Received in final form 28 May 2002 相似文献
259.
Dielectrophoresis of nanocolloids: A molecular dynamics study 总被引:1,自引:0,他引:1
Salonen E Terama E Vattulainen I Karttunen M 《The European physical journal. E, Soft matter》2005,18(2):133-142
Dielectrophoresis (DEP), the motion of polarizable particles in non-uniform electric fields, has become an important tool
for the transport, separation, and characterization of microparticles in biomedical and nanoelectronics research. In this
article we present, to our knowledge, the first molecular dynamics simulations of DEP of nanometer-sized colloidal particles.
We introduce a simplified model for a polarizable nanoparticle, consisting of a large charged macroion and oppositely charged
microions, in an explicit solvent. The model is then used to study DEP motion of the particle at different combinations of
temperature and electric field strength. In accord with linear response theory, the particle drift velocities are shown to
be proportional to the DEP force. Analysis of the colloid DEP mobility shows a clear time dependence, demonstrating the variation
of friction under non-equilibrium. The time dependence of the mobility further results in an apparent weak variation of the
DEP displacements with temperature. 相似文献
260.