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101.
M. Shyam Sundar Harish R. Talele Hemant M. Mande Ashutosh V. Bedekar Roberto C. Tovar Gilles Muller 《Tetrahedron letters》2014
A racemic sample of 2,2′,7,7′-tetrahydroxy-1,1′-binaphthyl was resolved with (S)-proline and the separated enantiomers were independently converted to atropisomeric bis-oxazines by aromatic Mannich reaction. These chirally pure oxazines were then converted to the helicene like cyclic ethers. The circularly polarized luminescence (CPL) profile was consistent with the isolation of the targeted helical-like molecules in optically pure form, prepared from the achiral primary amines. The compounds of interest displayed active and opposite CPL activities for each set of the helicene like isomers (P)-/(M)-3 and (P)-/(M)-5. 相似文献
102.
Dr. Jared B. DeCoste Dr. Mitchell H. Weston Patrick E. Fuller Trenton M. Tovar Gregory W. Peterson Dr. M. Douglas LeVan Dr. Omar K. Farha 《Angewandte Chemie (International ed. in English)》2014,53(51):14092-14095
We present a systematic study of metal–organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST‐1 (Cu‐BTC) and NU‐125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST‐1 and NU‐125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU‐125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications. 相似文献
103.
Christopher P. Harvey John D. Tovar 《Journal of polymer science. Part A, Polymer chemistry》2011,49(22):4861-4874
The optical properties of mechanochromic materials change under mechanical stress. Segmented polyurethanes are elastomers composed of amorphous, saturated chain soft segments, and rigid pi‐conjugated hard domains. Within aggregates of hard domains pi–pi interactions may form and result in perturbation of the optoelectronic properties of the system. Disruption and restoration of these electronic interactions within the material may lead to observable mechanochromic response. A series of oligothiophene diols and diamines, as well as a naphthalene diimide diol, have been synthesized for incorporation into the hard domains of segmented polyurethanes and polyureas using long poly(tetramethylene oxide) chains as soft segments. The resulting polymers were evaluated to determine their extent of polymerization and their thermal stability. The optical properties of the materials were studied in solution and as thin films. Where possible the electrochemical properties of the polymers were also explored. The length of the soft segment chains in the segmented polyurethanes hindered electronic coupling of hard domains. Future work involving smaller, more solubilizing soft segments may allow for easier material characterization and mechanochromic response. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. 相似文献
104.
The semileptonic decay width of heavy baryons such as (Λ
b
→ Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field
operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The
present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally
measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution
inside the hadron as free parameters. 相似文献
105.
Dynamic drag force based on iterative density mapping: A new numerical tool for three‐dimensional analysis of particle trajectories in a dielectrophoretic system 下载免费PDF全文
Francisco Javier Tovar‐Lopez Xinke Tang Arnan Mitchell Khashayar Khoshmanesh 《Electrophoresis》2016,37(4):645-657
Dielectrophoresis is a widely used means of manipulating suspended particles within microfluidic systems. In order to efficiently design such systems for a desired application, various numerical methods exist that enable particle trajectory plotting in two or three dimensions based on the interplay of hydrodynamic and dielectrophoretic forces. While various models are described in the literature, few are capable of modeling interactions between particles as well as their surrounding environment as these interactions are complex, multifaceted, and computationally expensive to the point of being prohibitive when considering a large number of particles. In this paper, we present a numerical model designed to enable spatial analysis of the physical effects exerted upon particles within microfluidic systems employing dielectrophoresis. The model presents a means of approximating the effects of the presence of large numbers of particles through dynamically adjusting hydrodynamic drag force based on particle density, thereby introducing a measure of emulated particle–particle and particle–liquid interactions. This model is referred to as “dynamic drag force based on iterative density mapping.” The resultant numerical model is used to simulate and predict particle trajectory and velocity profiles within a microfluidic system incorporating curved dielectrophoretic microelectrodes. The simulated data are compared favorably with experimental data gathered using microparticle image velocimetry, and is contrasted against simulated data generated using traditional “effective moment Stokes‐drag method,” showing more accurate particle velocity profiles for areas of high particle density. 相似文献
106.
Achim Weber Melanie Dettling Herwig Brunner Günter E. M. Tovar 《Macromolecular rapid communications》2002,23(14):824-828
Ultrasensitive isothermal titration calorimetry was used to generate thermodynamic data to assess the binding properties of molecularly imprinted polymer microgels. Microgels were imprinted using L ‐boc‐phenylalanine anilide (L ‐BFA) and then utilized in binding experiments with a variety of probe molecules, structurally closely related to the template molecule. Significant differences were observed between the binding enthalpy of the original template L ‐BFA and those of D ‐BFA, L ‐boc‐phenylalanine, L ‐boc‐tryptophane, and L ‐boc‐tyrosine. 相似文献
107.
An Unusually Small Singlet–Triplet Gap in a Quinoidal 1,6‐Methano[10]annulene Resulting from Baird’s 4n π‐Electron Triplet Stabilization 下载免费PDF全文
Dr. Benjamin C. Streifel Dr. José L. Zafra Guzmán L. Espejo Prof. Carlos J. Gómez‐García Prof. Juan Casado Prof. John D. Tovar 《Angewandte Chemie (International ed. in English)》2015,54(20):5888-5893
Within the continuum of π‐extended quinoidal electronic structures exist molecules that by design can support open‐shell diradical structures. The prevailing molecular design criteria for such structures involve proaromatic nature that evolves aromaticity in open‐shell diradical resonance structures. A new diradical species built upon a quinoidal methano[10]annulene unit is synthesized and spectroscopically evaluated. The requisite intersystem crossing in the open‐shell structure is accompanied by structural reorganization from a contorted Möbius aromatic‐like shape in S0 to a more planar shape in the Hückel aromatic‐like T1. This stability was attributed to Baird’s Rule which dictates the aromaticity of 4n π‐electron triplet excited states. 相似文献
108.
Levine DR Caruso A Siegler MA Tovar JD 《Chemical communications (Cambridge, England)》2012,48(50):6256-6258
The synthesis of new boron-containing acenes (meta-B-entacenes) is reported. These compounds exhibit slightly non-planar core geometries with blue-shifted spectral properties and more negative electrochemical reduction potentials relative to known para isomers. Polarizable π-extended architectures were realized via cross-coupling procedures with chloro-functionalized precursors. 相似文献
109.
Neutron and synchrotron powder diffraction data for β‐cryolite were collected within 550‐800(880) °C. Atomic coordinates of Al, F and Na atoms were obtained by both neutron Rietveld refinement and energy minimization in solid state at DFT level of theory. It was shown that although Rietveld refinements with fluorine atoms statically displaced from the 24e to the 96k special position of the Fm‐3m space group provide a reasonable fit to the experimental data, the refined structure differ from that obtained by the total energy minimization. The structure with the minimum of the total energy corresponds to the low temperature α‐phase with a zigzag arrangement of the polyhedra built around the Al and Na atoms. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献