全文获取类型
收费全文 | 186篇 |
免费 | 6篇 |
国内免费 | 3篇 |
专业分类
化学 | 110篇 |
力学 | 3篇 |
数学 | 43篇 |
物理学 | 39篇 |
出版年
2020年 | 3篇 |
2018年 | 2篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 13篇 |
2012年 | 8篇 |
2011年 | 8篇 |
2010年 | 3篇 |
2009年 | 4篇 |
2008年 | 11篇 |
2007年 | 5篇 |
2006年 | 12篇 |
2005年 | 5篇 |
2004年 | 4篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 15篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1963年 | 1篇 |
1930年 | 1篇 |
排序方式: 共有195条查询结果,搜索用时 468 毫秒
181.
Abbasi R Abdou Y Abu-Zayyad T Adams J Aguilar JA Ahlers M Andeen K Auffenberg J Bai X Baker M Barwick SW Bay R Bazo Alba JL Beattie K Beatty JJ Bechet S Becker JK Becker KH Benabderrahmane ML BenZvi S Berdermann J Berghaus P Berley D Bernardini E Bertrand D Besson DZ Bindig D Bissok M Blaufuss E Blumenthal J Boersma DJ Bohm C Bose D Böser S Botner O Braun J Brown AM Buitink S Carson M Chirkin D Christy B Clem J Clevermann F Cohen S Colnard C Cowen DF D'Agostino MV Danninger M Daughhetee J 《Physical review letters》2011,106(14):141101
IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18) eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from pγ interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence. 相似文献
182.
Linear dynamical systems with an affine parameter dependence producing low-rank variation in the state matrix can be recast as a nonparameterized system operating in parallel with a parameterized feed forward term operating under output constraints. This mapping permits the application of standard (nonparametric) model reduction strategies to solve parameterized problems. We demonstrate the approach on a parameterized vibration problem using optimal tangential interpolation. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
183.
Mechanistic Investigation of the Reaction of Epoxides with Heterocumulenes Catalysed by a Bimetallic Aluminium Salen Complex 下载免费PDF全文
Christopher Beattie Prof. Michael North 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):8182-8188
The bimetallic aluminium(salen) complex [(Al(salen))2O] is known to catalyse the reaction between epoxides and heterocumulenes (carbon dioxide, carbon disulfide and isocyanates) leading to five‐membered ring heterocycles. Despite their apparent similarities, these three reactions have very different mechanistic features, and a kinetic study of oxazolidinone synthesis combined with previous kinetic work on cyclic carbonate and cyclic dithiocarbonate synthesis showed that all three reactions follow different rate equations. An NMR study of [Al(salen)]2O and phenylisocyanate provided evidence for an interaction between them, consistent with the rate equation data. A variable‐temperature kinetics study on all three reactions showed that cyclic carbonate synthesis had a lower enthalpy of activation and a more negative entropy of activation than the other two heterocycle syntheses. The kinetic study was extended to oxazolidinone synthesis catalysed by the monometallic complex Al(salen)Cl, and this reaction was found to have a much less negative entropy of activation than any reaction catalysed by [Al(salen)]2O, a result that can be explained by the partial dissociation of an oligomeric Al(salen)Cl complex. A mechanistic rationale for all of the results is presented in terms of [Al(salen)]2O being able to function as a Lewis acid and/or a Lewis base, depending upon the susceptibility of the heterocumulene to reaction with nucleophiles. 相似文献
184.
Gräfe M Beattie DA Smith E Skinner WM Singh B 《Journal of colloid and interface science》2008,322(2):399-413
The co-sorption reaction products of arsenate (As(V)) and copper (Cu(II)) on goethite (alpha-FeOOH) and natro-jarosite (Na(3)Fe(3)(SO(4))(2)(OH)(6)) were investigated with extended X-ray absorption fine structure (EXAFS) spectroscopy to determine if Cu(II) and As(V) would form precipitates or compete with each other for surface sites. The reaction products were prepared by mixing 250 microM Cu(SO(4)) with 10, 25, or 50 microM Na(2)HAsO(4) at pH 5.65 and allowing the mixture to react in 10 m(2) L(-1) goethite or jarosite suspensions for 12 days. In addition, EXAFS data of Cu(SO(4)) and As(V) sorbed on goethite and jarosite were collected as control species. All reaction conditions were under-saturated with respect to common copper bearing minerals: tenorite (CuO), brochantite (Cu(4)(OH)(6)SO(4)), and hydrated clinoclase (Cu(3)(AsO(4))(2)2H(2)O). The extents of the As(V) and Cu(II) surface adsorption reactions showed a strong competitive effect from Cu(II) on As(V) adsorption for a nominal Cu:As mole-ratio of 25:1. With increasing nominal As(V) concentration, As(V) sorption on goethite and jarosite increased without diminishing the amount of Cu(II) sorption. In the absence of either co-sorbate, As(V) and Cu(II) formed the expected surface adsorption species, i.e., bidentate binuclear and edge-sharing surface complexes, consistent with previously published results. In each other's presence, the local bonding environments of As(V) and Cu(II) showed that the co-sorbates form a precipitate on the goethite and jarosite surface at nominal concentrations of 10:1 and 5:1. At nominal Cu:As mole-ratios of 25:1, Cu(II) did not form significantly different surface complexes on goethite or jarosite from those in the absence of As(V), however, As K-edge EXAFS results distinctly showed Cu(II) atoms in As(V)'s local bonding environment on the goethite surface. The structures of the two precipitates were different and depended on the anion-layer structure and possibly the presence of structural oxyanions in the case of jarosite. On goethite, the copper-arsenate precipitate was similar to hydrated clinoclase, while on jarosite, a euchroite-like precipitate (Cu(2)[AsO(4)](OH)3H(2)O, P 2(1)2(1)2(1)) had formed. Despite under-saturated solution conditions, the formation of these precipitates may have occurred due to a seed-formation effect from densely surface adsorbed Cu(II) and As(V) for which the "new" saturation index was significantly lower than homogeneous values would otherwise suggest. Synergistic reactions between two co-sorbates of fundamentally different surface adsorption behaviour can thus be achieved if the number of available sites for surface adsorption is limited. 相似文献
185.
Mierczynska-Vasilev A Ralston J Beattie DA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(12):6121-6127
The adsorption of three modified dextrins on the basal plane of talc has been studied using in situ tapping mode atomic force microscopy (TMAFM). The images have been used to determine the layer thickness and coverage of the adsorbed polymers. Adsorption isotherms of the polymers on talc particles were also determined using the depletion technique. Values of the adsorbed amount at equilibrium were compared with the volume of adsorbed material as determined using in situ TMAFM, revealing the presence of significant amounts of hydration water in the adsorbed layer structure. This deduction was confirmed by comparing in and ex situ TMAFM images of the adsorbed dextrins. The effect of layer thickness, coverage, and hydration water content on the contact angle of talc particles treated with polymer was investigated using the Washburn method and the equilibrium capillary pressure (ECP) method. Distinct correlations were observed between adsorbed layer properties and the measured contact angles, with the ECP measurements especially highlighting the effect of the adsorbed polymer layer hydration water. The implications for the performance of the modified dextrins in flotation are discussed. 相似文献
186.
The effects of oil solubility and composition on the zeta potential and drop size of oil-in-water emulsions stabilised by sodium dodecyl sulfate (SDS) were studied by electroacoustics and ultrasonic attenuation. The zeta-potentials of toluene and alkane emulsions were found to decrease (be less negative) as the water solubility of the dispersed oil phase increased. The zeta-potentials also depended on the composition of mixed oils, becoming more negative with increasing mole fraction of an insoluble oil (hexadecane). As the water solubility of the dispersed oil phase increased, the conductance within the Stern layer relative to the diffuse layer (K/K) increased, which is interpreted as due to the displacement of the shear plane further into the diffuse layer. The shear plane was calculated to increase from approximately 0.50 nm at the insoluble oil-water interface (hexadecane) to approximately 2.5 nm at a soluble oil-water interface of toluene. The lowering of the zeta-potentials of the soluble oils is ascribed to the shift of the shear plane into the diffuse layer, resulting in a more diffuse interface. The total surface conductance of the mixed oils was related to the log of the oil solubility and decreased from approximately 7 x 10(-9) Omega(-1) to 3 x 10(-9) Omega(-1) with increasing oil solubility from hexadecane to toluene, respectively. The lower surface conductance at the soluble oil-water interface is attributed to a reduction in the dielectric constant of the water inside of the shear plane, caused by the presence of the soluble oil. 相似文献
187.
Beattie JK 《Physical chemistry chemical physics : PCCP》2008,10(2):330-1; discussion 332-3
The surface of near-neutral water is basic due to the adsorption of hydroxide ions, not acidic as has been recently claimed. 相似文献
188.
Beaussart A Petrone L Mierczynska-Vasilev A McQuillan AJ Beattie DA 《Langmuir : the ACS journal of surfaces and colloids》2012,28(9):4233-4240
The adsorption of two dextrin-based polymers, a regular wheat dextrin (TY) and a carboxymethyl-substituted (CM) dextrin, onto an anatase TiO(2) particle film has been studied using in situ attenuated total reflection (ATR) FTIR spectroscopy. Infrared spectra of the polymer solutions and the polymer adsorbed at the anatase surface were acquired for two solution conditions: pH 3 and pH 9; below and above the isoelectric point (IEP) of anatase, respectively. Comparison of the polymer solution spectra and the adsorbed layer spectra highlighted a number of spectral differences that were attributed to involvement of the carboxyl group of CM Dextrin interacting with the anatase surface directly and the adsorption of oxidized dextrin chains in the case of regular dextrin (TY) at high pH. The adsorption/desorption kinetics were determined by monitoring spectral peaks of the pyranose ring of both polymers. Adsorption equilibrium was not established for Dextrin TY for many hours, whereas CM Dextrin reached equilibrium in its adsorption within 60 min. The extent of desorption of Dextrin TY (observed by flowing a background electrolyte dextrin-free solution) was extensive at both pH values, which reflects the poor affinity and binding of the polymer on anatase. In contrast, CM Dextrin underwent almost no desorption, indicating a high affinity between the carboxyl groups of the polymer and the anatase surface. 相似文献
189.
Mountford CP Mount AR Evans SA Su TJ Dickinson P Buck AH Campbell CJ Terry JG Beattie JS Walton AJ Ghazal P Crain J 《Journal of fluorescence》2006,16(6):839-845
Conformational transitions in a 4-way DNA junction when titrated with ionic solutions are studied using time-resolved fluorescence
resonance energy transfer. Parameters characterising the transition in terms of critical ion concentration (c
1/2) and the Hill coefficient for ion binding are obtained by fitting a simple two-state model using steady-state spectra. Data
obtained from a fluorescence lifetime plate reader and analysed by fitting a single exponential to donor fluorescence lifetime
decays are shown to be in good agreement with the parameters obtained from steady-state measurements. Fluorescence lifetimes,
however, offer advantages, particularly in being independent of fluorophore concentration, output intensity, inhomogeneity
in the excitation source and output wavelength. We demonstrate preliminary FRET-FLIM images of DNA junction solutions obtained
using a picosecond gated CCD which are in agreement with results from a fluorescence lifetime plate reader. The results suggest
that time-resolved FRET-FLIM is sensitive to subtle structural changes and may be useful in assays based on 4-way DNA junctions. 相似文献
190.
Terry JG Campbell CJ Ross AJ Livingston AD Buck AH Dickinson P Mountford CP Evans SA Mount AR Beattie JS Crain J Ghazal P Walton AJ 《Langmuir : the ACS journal of surfaces and colloids》2006,22(26):11400-11404
This work reports how the use of a standard integrated circuit (IC) fabrication process can improve the potential of silicon nitride layers as substrates for microarray technology. It has been shown that chemical mechanical polishing (CMP) substantially improves the fluorescent intensity of positive control gene and test gene microarray spots on both low-pressure chemical vapor deposition (LPCVD) and plasma-enhanced chemical vapor deposition (PECVD) silicon nitride films, while maintaining a low fluorescent background. This results in the improved discrimination of low expressing genes. The results for the PECVD silicon nitride, which has been previously reported as unsuitable for microarray spotting, are particularly significant for future devices that hope to incorporate microelectronic control and analysis circuitry, due to the film's use as a final passivating layer. 相似文献