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排序方式: 共有169条查询结果,搜索用时 46 毫秒
31.
The Simplest Amino‐borane H2B=NH2 Trapped on a Rhodium Dimer: Pre‐Catalysts for Amine–Borane Dehydropolymerization 下载免费PDF全文
Amit Kumar Nicholas A. Beattie Dr. Sebastian D. Pike Prof. Stuart A. Macgregor Prof. Andrew S. Weller 《Angewandte Chemie (International ed. in English)》2016,55(23):6651-6656
The μ‐amino–borane complexes [Rh2(LR)2(μ‐H)(μ‐H2B=NHR′)][BArF4] (LR=R2P(CH2)3PR2; R=Ph, iPr; R′=H, Me) form by addition of H3B?NMeR′H2 to [Rh(LR)(η6‐C6H5F)][BArF4]. DFT calculations demonstrate that the amino–borane interacts with the Rh centers through strong Rh‐H and Rh‐B interactions. Mechanistic investigations show that these dimers can form by a boronium‐mediated route, and are pre‐catalysts for amine‐borane dehydropolymerization, suggesting a possible role for bimetallic motifs in catalysis. 相似文献
32.
Whitby CP Djerdjev AM Beattie JK Warr GG 《Langmuir : the ACS journal of surfaces and colloids》2007,23(4):1694-1700
Droplet size distributions of concentrated, polydisperse oil-in-water emulsions have been measured using ultra small angle neutron scattering (USANS). The mean radii calculated by fitting a model for polydisperse hard spheres with excluded volume interactions to the USANS data were consistent with those derived from electroacoustics on diluted emulsions after correction for conductance behind the shear plane. The Porod radii measured by USANS were similarly consistent with the mean surface-area-weighted radii derived from electroacoustics, irrespective of the drop concentration or polydispersity. 相似文献
33.
Zhou J Beattie DA Ralston J Sedev R 《Langmuir : the ACS journal of surfaces and colloids》2007,23(24):12096-12103
Gold nanoparticles surface-coated with thyminethiol derivatives containing long hydrocarbon chains have been prepared. The diameter of the particles is 2.2 and 7.0 nm, respectively, with a relatively narrow size distribution. Thyminethiol derivatives are attached to the gold particle surfaces with thymine moieties as the end groups. The colloid stability of the gold nanoparticles as a function of the type and concentration of monovalent salt, pH, and particle size was investigated in alkaline, aqueous solutions. The gold particles are stable in concentrated NaCl and KCl solutions, but are unstable in concentrated LiCl and CsCl solutions. The larger gold particles are more sensitive to salt concentration and aggregate at lower salt concentrations. The reversible aggregation and dispersion of the gold particles can be controlled by changing the solution pH. The larger gold particles can be dispersed at higher pH and aggregate faster than the smaller particles, due to stronger van der Waals forces between the larger particles. Hydration forces play an important role in stabilizing the particles under conditions where electrostatic forces are negligible. The coagulation of the gold nanoparticles is attributed to van der Waals attraction and reduced hydration repulsion in the presence of LiCl and CsCl. 相似文献
34.
J. Renwick Beattie Josephine V. Glenn Michael E. Boulton Alan W. Stitt John J. McGarvey 《Journal of Raman spectroscopy : JRS》2009,40(4):429-435
Spectral signal intensities, especially in ‘real‐world’ applications with nonstandardized sample presentation due to uncontrolled variables/factors, commonly require additional spectral processing to normalize signal intensity in an effective way. In this study, we have demonstrated the complexity of choosing a normalization routine in the presence of multiple spectrally distinct constituents by probing a dataset of Raman spectra. Variation in absolute signal intensity (90.1% of total variance) of the Raman spectra of these complex biological samples swamps the variation in useful signals (9.4% of total variance), degrading its diagnostic and evaluative potential. Using traditional spectral band choices, it is shown that normalization results are more complex than generally encountered in traditionally designed sample sets investigating limited chemical species. We demonstrate that no choice of a single band proves to be appropriate for predicting all the reference parameters, instead requiring a tailored normalization routine for each parameter. Of the reference parameters studied in the chosen system, signals from pathogenic adducts in ocular tissues called advanced glycation endproducts were most prominent when normalizing about the 1550–1690 cm−1 region of the spectrum (17.5% of total variance, compared with 0.3% for unnormalized), while prediction of pentosidine and gender were optimized by normalization about the 1570 (R2 = 0.97 vs 0.57 for unnormalized) and 1003 cm−1 (p < 0.0000001 vs p < 0.01 for unnormalized) bands, respectively. The data obtained point to the extreme sensitivity of multivariate analysis to signal intensity normalization. Some general guidelines for making appropriate band choices are given, including the use of peak‐finding routines. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
35.
Margaret Beattie 《Acta Appl Math》2009,108(1):19-31
This short survey is based on a talk on the classification of finite dimensional Hopf algebras given at Memorial University
of Newfoundland in St. John’s in May of 2008. This seminar was given in conjunction with the mini-course “Introduction to
pointed Hopf algebras” offered by Professor Nicolás Andruskiewitsch which concentrated on classification methods and results
for the pointed case. Here we will outline some low dimensional classifications for the general case. 相似文献
36.
37.
Beattie DA Beaussart A Mierczynska-Vasilev A Harmer SL Thierry B Puskar L Tobin M 《Langmuir : the ACS journal of surfaces and colloids》2012,28(3):1683-1688
Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid-solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of <2.5 nm thin monolayer lubricant layers in the solid-solid contact, in addition to allowing for spectral acquisition from specific regions of the contact. Spectra of hydration water from within a confined polyelectrolyte multilayer film have also been acquired, highlighting the altered hydrogen bonding environment within the polymer layer. 相似文献
38.
Hexadecane-in-water emulsion droplets were formed in a homogeniser in the presence of a mixture of an anionic surfactant
(sodium dodecyl sulfate, SDS) and nonionic surfactants of various chain lengths [nonylphenol ethoxylate (C9φEN, N=100, 40 and 30) or an alcohol ethoxylate (Brij35)]. The dynamic mobility of the oil droplets was then measured using a flow-through
version of an AcoustoSizer. Large changes were observed in the dynamic mobility of the particles formed with the mixed surfactants
compared to particles formed with SDS alone. O'Brien's “gel layer” model was employed to interpret the data. The characteristics
of the adsorbed layer appeared to be similar whether the nonionic surfactant was adsorbed concurrently with the SDS as the
emulsion formed or was merely added afterwards to the emulsion established. The particle size, the charge and the molar fraction
of SDS had virtually no effect. The layers formed with the nonionic surfactants decreased in thickness with decreasing molecular
weight as expected. Passage through the homogeniser itself had no effect on the properties of the largest nonionic surfactant
and, hence, on the adsorption layer formed with it.
Received: 4 October 2000 Accepted: 16 October 2000 相似文献
39.
The rate constant for the homogeneous recombination of F-atoms with F2 as the third body was found to be (3.6 ± 1.4) × 1014 cm6/mol2s at 300 to 320 K. The corresponding rate constants with He and Ar as third bodies were also measured. 相似文献
40.
Poly(tetramethyl-p-silphenylene siloxane) and a series of copolymers with dimethylsiloxane have been prepared and characterised by means of ir and nmr spectroscopy and number average molecular weight measurements. Thermal gravimetry (TG) and Thermal Volatilisation Analysis (TVA) have been used to demonstrate the relationships which exist between stability and composition. 相似文献