全文获取类型
收费全文 | 277篇 |
免费 | 2篇 |
专业分类
化学 | 165篇 |
力学 | 3篇 |
数学 | 26篇 |
物理学 | 85篇 |
出版年
2020年 | 1篇 |
2019年 | 2篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 6篇 |
2011年 | 14篇 |
2010年 | 8篇 |
2009年 | 4篇 |
2008年 | 20篇 |
2007年 | 12篇 |
2006年 | 20篇 |
2005年 | 10篇 |
2004年 | 17篇 |
2003年 | 10篇 |
2002年 | 2篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 14篇 |
1998年 | 4篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1971年 | 6篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1964年 | 1篇 |
1939年 | 3篇 |
1929年 | 1篇 |
1924年 | 2篇 |
排序方式: 共有279条查询结果,搜索用时 0 毫秒
81.
The rate of shrinkage of air bubbles of initial radii, r, from 50 to 150 microm injected beneath a planar air-water interface has been measured. Bubbles were stabilized by 0.05 wt% protein in approximately 0.1 mol dm(-3) ionic strength buffer at pH 7.0 and at room temperature. Four proteins were studied: commercial whey protein isolate (WPI), sodium caseinate, gelatin, and pure beta-lactoglobulin. Bubbles in all systems showed shrinkage due to diffusion of gas from the bubbles, which accelerated as the bubbles got smaller. Within approximately 1 h all bubbles had disappeared, having shrunk to below approximately 1 microm, so that in no cases was there evidence of stabilization via a surface rheological mechanism. The rates of shrinkage with the different proteins were not significantly different except in the case of gelatin, which at any given bubble size appeared to give a slightly higher rate, probably because the surface tension is higher for this system. A new theoretical analysis of the dissolution kinetics for the case of a bubble close to a planar interface has been developed. For caseinate and WPI a simple model incorporating a constant surface tension and a constant bubble-interface separation appears to account for the kinetics. Interestingly, the model predicts a linear dependence of r(n) versus time when n is closest to 3, in contrast to n = 2 expected from previous work. For gelatin and pure beta-lactoglobulin, the introduction of modest dilatational elasticities of approximately 2.3 and 7 mN m(-1), respectively, gives good agreement between theory and experiment. This is particularly the case for beta-lactoglobulin, where there is a noticeable slowing, but not cessation, of the shrinkage as the bubbles get smaller. In the light of these findings the practical significance of surface rheology with respect to stability to disproportionation is discussed. Finally, we present experimental evidence that a bubble stabilized by beta-lactoglobulin shrinks to a nonspherical protein particle consisting of the completely collapsed protein film. 相似文献
82.
83.
84.
Kuwata KT Hasson AS Dickinson RV Petersen EB Valin LC 《The journal of physical chemistry. A》2005,109(11):2514-2524
The vinoxy radical, a common intermediate in gas-phase alkene ozonolysis, reacts with O2 to form a chemically activated alpha-oxoperoxy species. We report CBS-QB3 energetics for O2 addition to the parent (*CH2CHO, 1a), 1-methylvinoxy (*CH2COCH3, 1b), and 2-methylvinoxy (CH3*CHCHO, 1c) radicals. CBS-QB3 predictions for peroxy radical formation agree with experimental data, while the G2 method systematically overestimates peroxy radical stability. RRKM/master equation simulations based on CBS-QB3 data are used to estimate the competition between prompt isomerization and thermalization for the peroxy radicals derived from 1a, 1b, and 1c. The lowest energy isomerization pathway for radicals 4a and 4c (derived from 1a and 1c, respectively) is a 1,4-shift of the acyl hydrogen requiring 19-20 kcal/mol. The resulting hydroperoxyacyl radical decomposes quantitatively to form *OH. The lowest energy isomerization pathway for radical 4b (derived from 1b) is a 1,5-shift of a methyl hydrogen requiring 26 kcal/mol. About 25% of 4a, but only approximately 5% of 4c, isomerizes promptly at 1 atm pressure. Isomerization of 4b is negligible at all pressures studied. 相似文献
85.
Pugnaloni LA Matia-Merino L Dickinson E 《Colloids and surfaces. B, Biointerfaces》2005,42(3-4):211-217
We investigate the effect of sucrose on the microstructure of sodium caseinate gels induced by acidification. The average pore size and the fractal properties of two-dimensional slices of the gels are studied using confocal scanning laser microscopy and image analysis. The addition of sucrose promotes stronger and more fine-stranded gels while re-arrangements of the network tend to be prevented. Whereas the fractal dimension itself is not sensitive to changes in the gel microstructure upon addition of sucrose, the maximum cut-off distance, up to which fractal scaling behaviour applies, is substantially reduced, as is the average pore size. The overall microstructural changes seem to be consistent with previous rheological and light scattering studies of the same system. 相似文献
86.
Fracto-emission (FE) is the emission of particles and photons during and after fracture of materials. The observed emission includes electrons, negative and positive ions, neutral species in both ground states and in excited states, and visible photons. This emission can often serve as a sensitive probe of crack growth and may prove to be a useful tool for investigating molecular and microscopic events accompanying crack growth and for studying the details of failure modes in a variety of materials. Here, we examine photon and electron emission during failure of axially loaded stainless steel fixtures (e.g., rods) embedded in epoxy. These experimental data provide time resolved information on the sequence of events leading to interfacial fracture proceeding pullout. In addition, we examine the emissions during frictional pullout which over a large range of strain rates exhibits stick-slip behavior. Relations of these emissions to the fracture and pullout processes are discussed. 相似文献
87.
C. Bandis S.C. Langford J.T. Dickinson D.R. Ermer 《Applied Physics A: Materials Science & Processing》1999,69(7):S129-S132
We report electron and Na+ ion emission from single-crystal sodium nitrate (~10 eV band gap) upon exposure to IR (1064 nm, 1.16 eV) laser radiation. The fluence dependence of both the ion and the electron yield is highly nonlinear, and the kinetic energies of the emitted ions can reach values up to 5 eV. The fluence dependence and the ion energy distributions can be understood by a previously presented model involving multiple photon charge transfer plus electrostatic ejection of adions siting atop electron traps. Further evidence for the role of defects in the observed ion emission are provided by two-beam experiments; one beam (UV laser) is used to generate defects and the second beam (IR laser) is used to photodesorb the ions. Such experiments demonstrate that exposure of the sodium nitrate surfaces to UV laser radiation significantly increases the ion emission due to IR laser radiation. 相似文献
88.
89.
J. Wright D.C. Darvill M. Davenport F. Foster G. Hughes J.V. Morris J. Allison B. Dickinson S. Hill M. Ibbotson A. Latham H.E. Mills K. Stephens R. Thompson O. Vapenikova 《Nuclear Physics B》1981,181(3):403-420
The ratio of π? to π+ electroproduction cross sections from deuterons has been measured in the resonance region at an average four-momentum transfer squared of 0.5 (GeV/c)2. Results are presented over a wide range of pion production angles and comparisons are made with theoretical predictions based on SU(6)w symmetry and the Melosh transformation. 相似文献
90.
In this article we examine the electron emission accompanying the fracture of filled elastomers, where in previous work we have shown the emission to be intense and due predominately to interfacial failure. In this study we show that there is a strong velocity dependence on the rate of electron emission during the propagation of a crack in filled silicone rubber and polybutadiene filled with glass beads. This dependence cannot be explained by a simple proportionality between emission rate and rate of surface area production. We propose that the concentration of free radicals produced by crack propagation increases rapidly with crack velocity which in turn produces more intense electron emission by a chemiemission mechanism. 相似文献