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51.
Khaliullin RZ Cobar EA Lochan RC Bell AT Head-Gordon M 《The journal of physical chemistry. A》2007,111(36):8753-8765
An energy decomposition analysis (EDA) method is proposed to isolate physically relevant components of the total intermolecular interaction energies such as the contribution from interacting frozen monomer densities, the energy lowering due to polarization of the densities, and the further energy lowering due to charge-transfer effects. This method is conceptually similar to existing EDA methods such as Morokuma analysis but includes several important new features. The first is a fully self-consistent treatment of the energy lowering due to polarization, which is evaluated by a self-consistent field calculation in which the molecular orbital coefficients are constrained to be block-diagonal (absolutely localized) in the interacting molecules to prohibit charge transfer. The second new feature is the ability to separate forward and back-donation in the charge-transfer energy term using a perturbative approximation starting from the optimized block-diagonal reference. The newly proposed EDA method is used to understand the fundamental aspects of intermolecular interactions such as the degree of covalency in the hydrogen bonding in water and the contributions of forward and back-donation in synergic bonding in metal complexes. Additionally, it is demonstrated that this method can be used to identify the factors controlling the interaction of the molecular hydrogen with open metal centers in potential hydrogen storage materials and the interaction of methane with rhenium complexes. 相似文献
52.
Pawar Umakant D. Pansare Dattatraya N. Shelke Rohini N. Pawar Chandrakant D. Pathan Asif M. Thakre Vijay J. Dobhal Bhagwan S. Pardeshi Rajendra K. 《平面色谱法杂志一现代薄层色谱法》2022,35(4):431-434
JPC – Journal of Planar Chromatography – Modern TLC - 相似文献
53.
Joby E. Joy Eric Atamanik Rohini Mani Abanti Nag R.M. Tiwari V. Thangadurai J. Gopalakrishnan 《Solid State Sciences》2010,12(12):1970-1976
We describe the synthesis, structures and dielectric properties of new perovskite oxides of the formula, Ba3MIIITiMVO9, for MIII = Fe, Ga, Y, Lu and MV = Nb, Ta, Sb. While MV = Nb and Ta oxides adopt disordered/partially ordered 3C perovskite structures where MIII/Ti/MV metal-oxygen octahedra are corner-connected, the MV = Sb oxides show a distinct preference for the 6H structure, where SbV/TiIV metal-oxygen octahedra share a common face forming (Sb,Ti)O9 dimers that are corner-connected to the MIIIO6 octahedra. The preference of antimony oxides (SbV:4d10) for the 6H structure – which arises from a special SbV–O chemical bonding that tends to avoid linear Sb–O–Sb linkages unlike NbV/TaV:d0 atoms which prefer ~180° Nb/Ta–O–Nb/Ta linkages – is consistent with the crystal chemistry of MV–O oxides in general. The dielectric properties reveal a significant difference among MIII members. All the oxides with the 3C structure excepting those with MIII = Fe show a normal low loss dielectric behaviour with ε = 20–60 in the temperature range 50–400 °C; the MIII = Fe members with this structure (MV = Nb, Ta) display a relaxor-like ferroelectric behaviour with large ε values at frequencies ≤1 MHz (50–500 °C). 相似文献
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57.
Zhongda Pan Sarah M. Pound Naveen R. Rondla Christopher J. Douglas 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(20):5270-5274
A metal‐free, Lewis acid promoted intramolecular aminocyanation of alkenes was developed. B(C6F5)3 activates N‐sulfonyl cyanamides, thus leading to a formal cleavage of the N CN bonds in conjunction with vicinal addition of sulfonamide and nitrile groups across an alkene. This method enables atom‐economical access to indolines and tetrahydroquinolines in excellent yields, and provides a complementary strategy for regioselective alkene difunctionalizations with sulfonamide and nitrile groups. Labeling experiments with 13C suggest a fully intramolecular cyclization pattern due to the lack of label scrambling in double crossover experiments. Catalysis with Lewis acid is realized and the reaction can be conducted under air. 相似文献
58.
William N. Thurmes Kundalika M. More Michael R. Meadows Matthew B. O'Neill Rohini T. Vohra Michael D. Wand 《Liquid crystals》2013,40(5):461-477
Liquid-crystalline compounds containing germanium atoms were synthesised and assessed for liquid-crystalline properties. These new compounds generally possess smectic C phases, and many also possess nematic, smectic A and higher order smectic phases. The germanium-containing liquid crystals were incorporated into smectic C mixtures. These mixtures tend to exhibit little change in smectic C*?layer thickness over temperature. This characteristic is associated with de Vries smectic A materials, but measurements show that, although they have high smectic C stability, the materials' smectic cone angles are small. Measurement of smectic cone angle versus temperature of an exemplar material and its analogues containing carbon and silicon in place of the germanium, all show small cone angles which fall smoothly and extrapolate to zero as the smectic C*?to smectic A transition is approached. These measurements largely explain the observed small layer changes and establish that the materials are not first-order de Vries materials. They must be located elsewhere along the de Vries-orthogonal continuum of smectic A phases. 相似文献
59.
Zhongda Pan Sarah M. Pound Naveen R. Rondla Prof. Dr. Christopher J. Douglas 《Angewandte Chemie (International ed. in English)》2014,53(20):5170-5174
A metal‐free, Lewis acid promoted intramolecular aminocyanation of alkenes was developed. B(C6F5)3 activates N‐sulfonyl cyanamides, thus leading to a formal cleavage of the N? CN bonds in conjunction with vicinal addition of sulfonamide and nitrile groups across an alkene. This method enables atom‐economical access to indolines and tetrahydroquinolines in excellent yields, and provides a complementary strategy for regioselective alkene difunctionalizations with sulfonamide and nitrile groups. Labeling experiments with 13C suggest a fully intramolecular cyclization pattern due to the lack of label scrambling in double crossover experiments. Catalysis with Lewis acid is realized and the reaction can be conducted under air. 相似文献
60.
Dinesh R. Garud Amol R. Jadhav Santosh V. Lahore Nilesh M. Kahar Rohini R. Joshi Ramesh A. Joshi Mamoru Koketsu 《Tetrahedron letters》2014
The regioselective iodocyclization reaction of allene–thioureas is described, for the first time, for the synthesis of bicyclic β-lactams. The substitution at the allenyl part heavily influenced the iodocyclization reaction. The iodocyclization reaction of the unsubstituted allene–thioureas afforded six-membered 3-thia-1-dethiacephems whereas, the substituted allene–thiourea afforded seven-membered thiazepines along with five-membered isopenams. 相似文献