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71.
C. N. R. Rao P. C. Dwivedi Abha Gupta H. S. Randhawa 《Journal of Molecular Structure》1976,30(2):271-290
Properties of hydrogen bonds formed by 1:1 interaction of H2O with oxygen, nitrogen, sulphur and other electron donors have been evaluated by extended Hückel and CNDO methods and the results are discussed in relation to the experimental data. A detailed analysis of the variation of the dissociation energies and charge densities with bond distances is presented for the amine-water system. 1:2 complexes of water with donors are found to contain weaker hydrogen bonds than 1:1 complexes. Results of molecular orbital calculations on the hydrogen bonding of H2S and CH3SH with some donors are presented. The theoretical value of hydrogen bond dissociation energy varies linearly with the overlap population, and stretching force constant of the hydrogen bond as well as with the experimental O—H frequency shift. 相似文献
72.
Methylindium(III) dithiolate complexes of the general formulae [Me2In(S∩S)] ( 1 ) and [MeIn(S∩S)2] ( 2 ) [S∩S = (EtO)2PS2?, (PriO)2PS2?, Et2NCS2?, , O(CH2CH2)2NCS2?, EtOCS2? and PriOCS2?] have been isolated conveniently by the reaction of Me3In·OEt2 with In(S∩S)3 ( 3 ) in an appropriate stoichiometry. Both 1 and 2 have been characterized by indium analysis, IR, NMR (1H, 13C{1H} and 31P{H}) and mass spectral data. NMR data of 3 are also included for comparison. The Me–In and S∩S resonances are sensitive to the number of methyl groups attached to indium metal. The mass spectral data indicate that these complexes are monomeric in nature. The thermal behavior of a few complexes has been investigated. The xanthate and dithiocarbamate complexes on pyrolysis under dynamic vacuum or flowing nitrogen atmosphere gave either In2S3 or a mixture of InS, In2S3 and In6S7, which were characterized using EDAX and powder XRD. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
73.
Oxy anions 3 generated from 1,2-dihydrocyclobutabenzen-1-ones 1 through addition of a charged nucleophile or from 1-hydroxy-1,2-dihydrocyclobutabenzenes 2 by deprotonation with base lead to stable products through distal and/or proximal cleavage of the strained four-membered ring via benzyl carbanion 4 and/or aryl carbanion 5. A systematic study of this process reveals the relative stability of the two isomeric carbanions 4 and 5 as a key factor in determining the course of the ring-cleavage reaction. While benzyl carbanions 4 can be trapped with carbon electrophiles, attempts at trapping aryl carbanions 5 with electrophiles other than H+ failed. In protic solvents, the magnesium salt of the tertiary alcohol 2 shows an increased rate of proximal cleavage as compared to its alkali salts. From this, we conclude that, in contrast to benzyl carbanions 4 , free aryl carbanions 5 are of transient existence only. Proximal C,C-bond cleavage seems to occur either through protonation of 5 from a fast, reversible equilibrium 3 ? 5 in which 3 strongly predominates, or in protic solvents possibly even through a rate-limiting protonation of 3 at the aromatic C-atom, bypassing free anion 5 altogether. Thus, additional factors other than just the relative stability of isomeric carbanions 4 and 5 are of importance in determining the regiochemistry of the base-induced C,C-bond cleavage in ketones 1 and in alcohols 2 . 相似文献
74.
Sharma VK Saharo PD Sharma N Rastogi RC Ghoshal SK Mohan D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(6):1161-1170
Absorption and fluorescence emission of 4 and 7 substituted coumarins viz. C 440, C 490, C 485 and C 311 have been studied in various polar and non-polar organic solvents. These coumarin dyes are substituted with alkyl, amine and fluorine groups at 4- and 7-positions. They give different absorption and emission spectra in different solvents. The study leads to a possible assignment of energy level scheme for such coumarins including the effect on ground state and excited state dipole moments due to substitutions. Excited state dipole moments of these dyes are calculated by solvetochromic data experimentally and theoretically these are calculated by PM 3 method. The dipole moments in excited state, for all molecules investigated here, are higher than the corresponding values in the ground state. The increase in dipole moment has been explained in terms of the nature of excited state and resonance structure. 相似文献
75.
76.
Structural Chemistry - This study focuses on the biological prospects of oxygen-depleted calix[4]arene ligands on a protein target. Because of their extensive medical relevance, the oxygen-depleted... 相似文献
77.
Kaur Pushpinder Chaudhary Abha Katiyar Arti Singh Bikram Gopichand Singh Rakesh D. 《平面色谱法杂志一现代薄层色谱法》2012,25(5):415-419
JPC – Journal of Planar Chromatography – Modern TLC - A reverse phase high-performance thin-layer chromatography (RPHPTLC) method was developed for determination of vitexin, hyperoside,... 相似文献
78.
Sushanta Ghoshal Mubarak A. Khan Farhana Gul-E-Noor Ruhul A. Khan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(10):975-982
In this study the mechanical properties of shellac films, prepared by solution casting, were evaluated with varying amounts of Ethylene Glycol (EG) and 2-Ethyl-2-(hydroxymethyl)-1,3-propandiol-trimethacrylate (EHMPTMA). Mechanical properties such as tensile strength (TS) and elongation at break (Eb) of the raw shellac film were found to be 1.86 MPa and 4%, respectively. A series of formulations was prepared using shellac and varying percentages of EG and EHMPTMA in methanol. The films were prepared and irradiated under gamma (Co-60) radiation at different doses (50–500 krad). Grafting of EHMPTMA showed better results compared to raw shellac and EG treated films. Thermal properties, degradation tests in water and soil of the films were also evaluated. 相似文献
79.
A facile chemoenzymatic synthesis of the harzia lactone A enantiomers was developed. A lipase-catalyzed acylation and an enantio-controlled substrate and reagent-controlled Sharpless’ asymmetric dihydroxylation are the key features of the synthesis. 相似文献
80.
Sandhya Choubey D. Indumathi S. Agarwalla A. Bandyopadhyay G. Bhattacharyya E. J. Chun B. Dasgupta A. Dighe P. Ghoshal A. K. Giri S. Goswami M. Hirsch T. Kajita M. Kaplinghat H. S. Mani R. Mohanta M. V. N. Murthy S. Pakvasa M. K. Parida G. Rajasekaran S. Ray W. Rodejohann P. Roy S. Uma Sankar T. Schwetz N. Sinha 《Pramana》2009,72(1):269-275
This is the report of the neutrino physics working group at WHEPP-X. We summarize the problems selected and discussed at the
workshop and the papers which have resulted subsequently.
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