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排序方式: 共有70条查询结果,搜索用时 109 毫秒
41.
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Ying Liu Chunhua Li Shuang Chen Ellen Wachtel Tadanori Koga Jonathan C. Sokolov Miriam. H. Rafailovich 《Journal of polymer science. Part A, Polymer chemistry》2009,47(24):2501-2508
Poly(ethylene-co-vinyl acetate)/clay nanocomposite fibers were fabricated using electrospinning. The fiber diameters were controlled by varying the polymer/chloroform concentration, which resulted in fibers with diameters ranging from 1 to 15 μm. The clay concentration was varied from 0.35 to 6.6 wt %. Scanning electron microscopy revealed that the fiber diameter increased with increasing clay concentration, whereas beading decreased. Transmission electron microscopy revealed a disruption of the spherulite structures by clay, which is consistent with heterogeneous nucleation. Shear modulus force microscopy indicated a reduction in melting point (Tm) with decreasing diameter for fibers thinner than 15 μm, which was confirmed by temperature dependent X-ray diffraction data. For fibers thinner than 8 μm, the presence of clay further enhanced the reduction of Tm. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2501–2508, 2009 相似文献
43.
Alcohol ethoxylates (AEs) are nonionic surfactants. They are industrially important compounds that have historically been difficult to analyze, with the best results to date achieved through derivatization (e.g., silylation) followed by analysis by gas chromatography/mass spectrometry (GC/MS). Recently, mass spectrometric techniques such as field desorption (FD), time-of-flight secondary ion mass spectrometry (TOF-SIMS), fast atom bombardment (FAB), electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) have been employed to analyze surfynol(R) 4xx. In an effort to produce low-cost alkyl-capped AEs and anionic detergents from AEs, a fast and reliable measure of the product yields and conversions from AEs is required in research. We found that the product yields and conversions from reactions of AEs, obtained by the employment of atmospheric pressure chemical ionization (APCI), were in good agreement with those obtained from proton nuclear magnetic resonance spectroscopy ((1)H-NMR). Therefore, APCI can be used as a validated tool for studying AE reactions. Mixtures that contain either silylated or unsilylated ethoxylates and/or carboxylates yield the same APCI mass spectra. Copyright -Copyright 1999 John Wiley & Sons, Ltd. 相似文献
44.
M. H. Rafailovich E. Dafni G. Schatz S. Y. Zhu K. Dybdal S. Vajda C. Alonso-Arias S. Rolston G. D. Sprouse 《Hyperfine Interactions》1983,15(1-4):43-54
The current status of g-factor measurements of fission isomers is reviewed. In particular, we concentrate on magnetic and electric extranuclear perturbations affecting the fission isomers in solid environments. Recent results for isomers in237Pu and239Am are summarized and the single particle nature of these states is discussed.This work was supported in part by the National Science Foundation. 相似文献
45.
Drying of DNA droplets 总被引:1,自引:0,他引:1
Fang X Li B Petersen E Seo YS Samuilov VA Chen Y Sokolov JC Shew CY Rafailovich MH 《Langmuir : the ACS journal of surfaces and colloids》2006,22(14):6308-6312
The evaporation kinetics of droplets containing DNA was studied, as a function of DNA concentration. Drops containing very low DNA concentrations dried by maintaining a constant base, whereas those with high concentration dried with a constant contact angle. To understand this phenomenon, the distribution of the DNA inside the droplet was measured using confocal microscopy. The results indicated that the DNA was condensed mostly on the surface of the droplets. In the case of high concentration droplets, it formed a shell, whereas isolated islands were found for droplets of low DNA concentrations. Rheologic results indicate the formation of a hydro gel in the low concentration drops, whereas phase separation between the self-assembled DNA structures and the water phase occurred at higher concentration. 相似文献
46.
We have performed x-ray specular and diffuse scattering on liquid polymer films and analyzed the spectra as a function of film thickness and molecular weight. The results show that films whose molecular weight is close to the entanglement length behave as simple liquids except that the shortest wavelength is determined by the radius of gyration (R(g)) rather than the monomer-monomer distance. When the molecular weight is higher than the entanglement length, the strong deviations from liquidlike behavior are observed. We find that the long wavelength cutoff vector, q(l,c), scales with film thickness, d as d(-1.1+/-0.1) rather than the usual d(-2) expected for simple liquids. If we assume that these deviations are due to surface pinning of the polymer chains, then our results are consistent with the formalism developed by Fredrickson et al. to explain the capillary wave spectrum that can propagate in a polymer brush. 相似文献
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E. Dafni M. Hass E. Naim M.H. Rafailovich A. Berger H. Grawe H.-E. Mahnke 《Nuclear Physics A》1985,441(3):501-510
The electric quadrupole interaction of the 212 Rn 8+ and 6+ isomers in a Bi single crystal was measured. The experimental results together with a shell-model calculation of the quadrupole moments provide a calibration of the electric field gradient for Rn impurities in Bi, to be used in future quadrupole-moment measurements of Rn isomers. A two-level analysis procedure was employed for the combined data of the 8+ and 6+ isomers. 相似文献
50.
The conventional type of magnetic well is formed by superposition of two types of magnetic field, axial bumpy field and radial
multipole field. It is used to contain plasma that consists of neutrals, ions and electrons. These particles are in constant
motion in the well and energetic electrons create plasma by violent collisions with neutrals and ions. The confined electrons
are constantly heated by ECR technique in the presence of magnetic field. In this paper it has been shown theoretically that
how the electron motion is influenced in terms of heating, containment and azimuthal uniformity of plasma, by the axial rotation
of the multipole magnetic field [1,2]. Afterwards, the feasibility of achieving a rotating magnetic multipole field is discussed
to some extent. And it is seen that it is not beyond the capability of the scientific community in the present scenario of
the advanced technology. Presently, it can be achieved for lesser field and slightly larger size of the multipole electromagnet
and can be used for improvement of the ECR ion source (ECRIS). 相似文献