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101.
N. George B. V. Kamath A. G. Basrur K. R. Krishnamurthy 《Reaction Kinetics and Catalysis Letters》1997,60(2):379-386
The function of hydrogen used as carrier gas in catalytic dehydrogenation is to increase the selectivity and stability of
catalysts. It slows down catalyst deactivation by either inhibiting deposition of potential coke precursors or facilitating
their desorption by rehydrogenation. This function, in gas-solid catalytic dehydrogenation appears to be interphase mass transfer
controlled by increased hydrogen linear flow velocities decreasing the extent of deactivation. Besides, deactivation appears
to progress through two regimes, an initial short term followed by a long term deactivation. 相似文献
102.
103.
Ruppa P. Kamalesh Babu Setharampattu S. Krishnamurthy Munirathinam Nethaji 《Heteroatom Chemistry》1991,2(4):477-485
Two new diphosphazane ligands, PriN(PPh2)(PO2C6H4) ( 1 ) and PriN{P(O2C6H4)}2 ( 3 ), have been synthesized and characterized by spectroscopic data. The structure of 1 has been confirmed by single crystal X-ray diffraction. Crystal data: Monoclinic, C2/c, Z = 16, a = 34.149(5) Å, b = 9.717(6) Å, c = 29.439(5) Å, β = 125.11(2)°, V = 7991 Å3, R = 0.058, Rw = 0.061. This compound shows two different P–N bond lengths (1.654 (4) and 1.743(4) Å) and a P–N–P angle of 120.7(2)°. Variable temperature 31P NMR measurements for 1 and 3 throw light on the nature of the conformers present in solution. 相似文献
104.
David J. Lingley Robert A. Shaw Michael Woods S. S. Krishnamurthy 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):379-382
Abstract The three isomers of N3P3Cl4(NHPr1)2 have been prepared and separated by gas-liquid chromatography. Their structures have been assigned on the basis of 1H and 31P nmr data. 相似文献
105.
106.
107.
108.
Reddy AR Krishnamurthy NV Bhudevi B 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(3):700-708
Electron donor-acceptor molecular complexes of a few phenolic donors with some quinonoid and tetracyanoethylene acceptors have been prepared by two different methods, i.e., by simple grinding of the respective component pair in the solid-state and in solution. Both the methods yielded identical dark colored 1:1 stoichiometric complexes. Spectral studies revealed that the complexes are ionic in nature. The g values obtained in ESR spectral studies for all these molecular adducts vary between 2.000 and 2.022, confirming the free radical nature of the adducts. The electronic absorption spectral studies proved that the donor-acceptor complexes formed initially, exhibit new electronic transitions at longer wavelengths, are less stable and disassociate readily into ionic type of adducts. The absorption maximum at longer wavelengths, i.e. >or=550 nm, are assigned to the charge transfer complexes, while the new transition at around 410 +/- 5 nm is attributed to the anion radical of the adducts. The ease of complexation not only depends on the ionization potential and electron affinities of the phenolic donors and the acceptors but is also structure sensitive. Complexation is confirmed by the shift in IR absorption of the phenolic hydroxyl group and the carbonyl group of quinone acceptors and the cyano group of tetracyanoethylene. Proton magnetic resonance studies indicate an interaction between the phenolic donors and acceptors on basis of the altered chemical shifts. Further, IR and NMR studies show that the stability of the adducts is governed not only by the charge transfer interaction but also by hydrogen bonding. 相似文献
109.
Krishnamurthy D Kasper GD Namuswe F Kerber WD Narducci Sarjeant AA Moënne-Loccoz P Goldberg DP 《Journal of the American Chemical Society》2006,128(44):14222-14223
The synthesis of a mononuclear, five-coordinate ferrous complex [([15]aneN4)FeII(SPh)](BF4) (1) is reported. This complex is a new model of the reduced active site of the enzyme superoxide reductase (SOR), which is comprised of a [(NHis)4(Scys)FeII] center. Complex 1 reacts with alkylhydroperoxides (tBuOOH, cumenylOOH) at low temperature to give a metastable, dark red intermediate (2a: R = tBu; 2b: R = cumenyl) that has been characterized by UV-vis, EPR, and resonance Raman spectroscopy. The UV-vis spectrum (-80 degrees C) reveals a 526 nm absorbance (epsilon = 2150 M-1 cm-1) for 2a and a 527 nm absorbance (epsilon = 1650 M-1 cm-1) for 2b, indicative of alkylperoxo-to-iron(III) LMCT transitions, and the EPR data (77 K) show that both intermediates are low-spin iron(III) complexes (g = 2.20 and 1.97). Definitive identification of the Fe(III)-OOR species comes from RR spectra, which give nu(Fe-O) = 612 (2a) and 615 (2b) cm-1, and nu(O-O) = 803 (2a) and 795 (2b) cm-1. The assignments for 2a were confirmed by 18O substitution (tBu18O18OH), resulting in a 28 cm-1 downshift for nu(Fe-18O), and a 46 cm-1 downshift for nu(18O-18O). These data show that 2a and 2b are low-spin FeIII-OOR species with weak Fe-O bonds and suggest that a low-spin intermediate may occur in SOR, as opposed to previous proposals invoking high-spin intermediates. 相似文献
110.
de la Presa P. Alonso R.E. Ayala A.P. Krishnamurthy V.V. Lieb K.P. López García A. Neubauer M. Uhrmacher M. 《Hyperfine Interactions》1999,120(1-8):479-483
The temperature dependence of the hyperfine parameters in SrHfO3 powder samples has been investigated by means of Perturbed Angular Correlation spectroscopy using implanted 111In probes. Three quadrupole interactions have been established, with the largest fraction showing a pronounced dynamic interaction.
We assign this fraction to 111In / 111Cd probe atoms on substitutional Hf sites. The temperature dependence of the dynamic interaction has been associated to the
Pnma↔Imma phase transition at ∼700 K. We discuss the results in relation to those obtained for 181Hf / 111Ta-probes in AHfO3 (A=Ba, Sr, Ca) and for 111In / 111Cd-probes in PbZrO3 and BaTiO3.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献