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41.
Sticking probability for oxygen adsorption on thin iron films and readsorption on surface sites liberated due to incorporation of the adsorbate adatoms below the surface during thermal treatment has been studied by means of the Wagener flow method. Sticking probability for oxygen adsorption on oxidized thin iron films has also been measured for comparison.
, . .相似文献
42.
Julia Pretula Krzysztof Kaluzynski Blazej Wisniewski Ryszard Szymanski Ton Loontjens Stanislaw Penczek 《Journal of polymer science. Part A, Polymer chemistry》2008,46(3):830-843
Conditions of synthesis of poly(ethylene phosphates) in reaction of H3PO4 with HOCH2CH2OH (EG), the actual path of polycondensation, and structure of the obtained polymers (mostly oligomers) and kinetics of reaction are described. Preliminary kinetic information, based on the comparison of the MALDI‐TOF‐ms and 31P{1H} NMR spectra as a function of conversion is given as well. Because of the dealkylation process fragments derived from di‐ and triethylene glycols are also present in the repeating units. Structures of the end groups (? CH2CH2OH or ? OP(O)(OH)2) depend on the starting ratio of [EG]0/[H3PO4]0, although even at the excess of EG the acidic end groups prevail because of the dealkylation process. In MALDI‐TOF‐ms products with Pn equal up to 21 have been observed. The average polymerization degrees (Pn) are lower and have been calculated from the proportion of the end groups. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 830–843, 2008 相似文献
43.
Ryszard Wawryk Andrzej Wojakowski Adam Pietraszko Zygmunt Henkie 《Solid State Communications》2005,133(5):295-300
Single crystals of thorium phosphorosulfide have been grown by the chemical vapour transport method. The X-ray diffraction examination showed that the unit cell of the crystals belongs to a tetragonal system of the PbFCl-type structure. The basal plane resistivity ρ(300 K)=64 μΩ cm and thermoelectric power S(300 K)=−7.7 μV/K, examined between 0.4 and 315 K, show metallic behaviour. 相似文献
44.
Ryszard Mańka 《International Journal of Theoretical Physics》1990,29(11):1155-1166
The realization of topological solitons, zero modes, and supersymmetry in theCP
1 nonlinear sigma model, a theory of high-T
c superconductivity, is presented. 相似文献
45.
46.
Several different models have been proposed to explain the origin of the complex anti-hole features observed in hole-burned (HB) spectra of excitonically coupled systems such as photosynthetic complexes. This lack of consensus presents a serious constraint on the interpretation of HB spectra and the underlying electronic structures of these systems. To resolve this problem we present results of modeling studies of non-resonant HB spectra taking uncorrelated excitation energy transfer and excitonic interactions into account. Simplified analytical results are compared with Monte Carlo simulations in which excitonic interactions are explicitly taken into account in order to disentangle a number of distinct effects. It is shown that these effects can accurately account for both hole shapes and the broad anti-hole structure observed in excitonically coupled systems. We argue that these models will provide a necessary framework for probing the electronic structure of these systems via HB spectroscopy. 相似文献
47.
Density functional theory (DFT) calculations show that in vacuum such α-diketone as 1-(pyridin-2-yl)-4-(quinolin-2-yl)butane-2,3-dione
is much less stable than its enolimine–enaminone ((1Z,3Z)-3-hydroxy-4-(pyridin-2-yl)-1-(quinolin-2(1H)-ylidene)but-3-en-2-one) and dienaminone tautomers ((1Z,3Z)-1-(pyridin-2-yl)-4-(quinolin-2-yl)buta-1,3-diene-2,3-diol). Other its tautomers (multiple basic and acidic centers in their
molecules enable multiple proton transfer to take place) are even more labile. Strength of the intramolecular hydrogen bonds
and aromatic character of the (quasi)rings [proved by the Harmonic Oscillator Model of Aromaticity (HOMA) index] in their
molecules were found to be responsible for the observed tautomeric preferences. Polar and basic solvent disfavors and favors
the enolimine and enaminone tautomers, respectively. 相似文献
48.
DFT studies on tautomeric preferences. Part 3: Proton transfer in 2-(8-acylquinolin-2-yl)-1,3-diones
8-Acetyl- and 8-benzoyl-2-(quinolin-2-yl) derivatives of 1,3-diketones were studied from point of view of their tautomeric
preferences. Effective electron delocalization and strong hydrogen bonds were found to be responsible for high stability of
the enaminone form (the most stable tautomer). Density functional theory (DFT) calculations prove that enolimine and ketimine
species are less favored. Contribution of the zwitterionic resonance structures to the enaminone form is most significant
in 2-(quinolin-2(1H)-ylidene)-2H-indene-1,3-dione derivatives. Formation of the bifurcated hydrogen bonds was found to take place only in 8-acetyl derivatives.
One of these bonds is of the RAHB (Resonance Assisted Hydrogen Bond) type. There is a steric interaction of the pyridine β-hydrogen
and carbonyl oxygen atoms in the enaminone tautomers. 相似文献
49.
Beata Zielińska Ewa Borowiak-Palen Ryszard J. Kalenczuk 《Journal of Physics and Chemistry of Solids》2011,72(2):117-123
Fe-, Ni-, Co- and Ag- loaded NaNbO3 catalysts were prepared and their activities have been investigated in the reaction of photocatalytic hydrogen generation. Me/NaNbO3 were synthesized by impregnation of NaNbO3 in an aqueous solution of metal nitrates and then by calcination at the temperature of 400 °C. The crystallographic phases and optical and vibronic properties were examined by X-ray diffraction (XRD) and diffuse reflectance (DR) UV-vis and resonance Raman spectroscopic methods, respectively. Morphology and chemical composition of the produced samples were studied using a high-resolution transmission electron microscope (HR-TEM) and an energy dispersive X-Ray spectrometer (EDX) as its mode. The detailed analysis has revealed that all the investigated catalysts exhibit high crystallinity and the presence of Fe2O3, NiO, Co3O4 and Ag2O oxides on Me/NaNbO3 was confirmed. Finally, the influence of different metal loadings (Fe, Ni, Co and Ag) on the photocatalytic activity of NaNbO3 for photocatalytic hydrogen generation has been investigated. Here we report that among all the Me/NaNbO3 photocatalysts Ag-loaded NaNbO3 exhibited higher photocatalytic efficiency for photocatalytic hydrogen generation than NaNbO3. 相似文献
50.
Adam Liwo Jarosław Pillardy Rajmund Kaźmierkiewicz Ryszard J. Wawak Małgorzata Groth Cezary Czaplewski Stanisaw Ołdziej Harold A. Scheraga 《Theoretical chemistry accounts》1999,101(1-3):16-20
A united-residue model of polypeptide chains developed in our laboratories with united side-chains and united peptide groups
as interaction sites is presented. The model is designed to work in continuous space; hence efficient global-optimization
methods can be applied. In this work, we adopted the distance-scaling method that is based on continuous deformation of the original
rugged energy hypersurface to obtain a smoothed surface. The method has been applied successfully to predict the structures
of simple motifs, such as the three-helix bundle structure of the 10-58 fragment of staphylococcal protein A in de novo folding
simulations and more complicated motifs in inverse-folding simulations.
Received: 24 April 1998 / Accepted: 4 August 1998 / Published online: 2 November 1998 相似文献