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951.
952.
Mauro Prencipe Lorenzo Maschio Bernard Kirtman Simone Salustro Alessandro Erba Roberto Dovesi 《Journal of Raman spectroscopy : JRS》2014,45(8):703-709
The Raman spectrum of NaAlSi2O6 jadeite is simulated and compared with two recent experimental data sets. In one experiment, only 17 (out of 30 symmetry allowed) peaks and a qualitative estimate of the intensities are provided. In the second case, the digitalized spectrum is available, from which we have been able to extract 20 evident peaks and an estimate of the relative intensities. The present calculation is based on an ab initio quantum mechanical treatment. Using an all‐electron Gaussian‐type basis set, together with the hybrid B3LYP density functional, the full set of 30 active modes and their (polycrystalline and polarized) intensities are obtained. The simulated intensities (not available in a previous study of the same system) permit the two experimental spectra to be reconciled and explain why the missing peaks were not seen. This ultimately leads to excellent agreement between experiment and theory. By artificially varying the mass of the Na + and Al3 + cations in the simulations, which can be performed automatically and at essentially no computational cost, the vibrational modes to which these ions contribute are identified. We conclude that quantum mechanical simulation can be a very useful complementary tool for the interpretation of experimental Raman spectra. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
953.
954.
Alcaro S Bolasco A Cirilli R Ferretti R Fioravanti R Ortuso F 《Journal of chemical information and modeling》2012,52(3):649-654
A computer-aided design of novel asymmetric pyrazoles with improved enantioselective properties was performed by docking experiments starting from a model of Chiralcel OJ chiral in the stationary phase. Synthesis and HPLC experiments confirmed the theoretical prediction and led to a detailed investigation of the enantioselective recognition process. For the first time, looking at the time spent by each enantiomer in contact with the CSP during long molecular dynamic simulations, the experimental analytical trend has been reproduced. 相似文献
955.
Cabras T Boi R Pisano E Iavarone F Fanali C Nemolato S Faa G Castagnola M Messana I 《Journal of separation science》2012,35(9):1079-1086
This study describes the characterization of the glycan moieties and the peptide backbone of six glycoforms of IB-8a CON1(+), a basic proline-rich protein present in human saliva. MS analyses on the intact glycoproteins before and after N-deglycosylation with PNGase F and high-resolution MS/MS sequencing by LTQ Orbitrap XL of peptides and glycopeptides from tryptic digests allowed the structural characterization of the glycan moieties and the polypeptide backbone, as well as to establish the glycosylation site at the asparagine residue at 98th position. Five of the glycoforms carry a biantennary N-linked glycan fucosylated in the innermost N-acetylglucosamine of the core and showing from zero to four additional fucoses in the antennal region. The sixth glycoform carries a monoantennary monofucosylated oligosaccharide. The glycoform cluster was detected on 28 of 71 adult saliva specimens. Level of fucosylation showed interindividual variability with the major relative abundance for the trifucosylated glycoform. Nonglycosylated IB-8a CON1(+) and the variant IB-8a CON1(-), lacking of the glycosylation site, have been also detected in human saliva. 相似文献
956.
Balmes O Resta A Wermeille D Felici R Messing ME Deppert K Liu Z Grass ME Bluhm H van Rijn R Frenken JW Westerström R Blomberg S Gustafson J Andersen JN Lundgren E 《Physical chemistry chemical physics : PCCP》2012,14(14):4796-4801
The structure and chemical composition of Pd nanoparticles exposed to pure CO and mixtures of CO and O(2) at elevated temperatures have been studied in situ by a combination of X-ray Diffraction and X-ray Photoelectron Spectroscopy in pressures ranging from ultra high vacuum to 10 mbar and from room temperature to a few hundred degrees celsius. Our investigation shows that under CO exposure, above a certain temperature, carbon dissolves into the Pd particles forming a carbide phase. Upon exposure to CO and O(2) mixtures, the carbide phase forms and disappears reversibly, switching at the stoichiometric ratio for CO oxidation. This finding opens new scenarios for the understanding of catalytic oxidation of C-based molecules. 相似文献
957.
D'Arienzo M Ruffo R Scotti R Morazzoni F Mari CM Polizzi S 《Physical chemistry chemical physics : PCCP》2012,14(17):5945-5952
The present study reports on the synthesis and the electrochemical behavior of Na(0.71)CoO(2), a promising candidate as cathode for Na-based batteries. The material was obtained in two different morphologies by a double-step route, which is cheap and easy to scale up: the hydrothermal synthesis to produce Co(3)O(4) with tailored and nanometric morphology, followed by the solid-state reaction with NaOH, or alternatively with Na(2)CO(3), to promote Na intercalation. Both products are highly crystalline and have the P2-Na(0.71)CoO(2) crystal phase, but differ in the respective morphologies. The material obtained from Na(2)CO(3) have a narrow particle length (edge to edge) distribution and 2D platelet morphology, while those from NaOH exhibit large microcrystals, irregular in shape, with broad particle length distribution and undefined exposed surfaces. Electrochemical analysis shows the good performances of these materials as a positive electrode for Na-ion half cells. In particular, Na(0.71)CoO(2) thin microplatelets exhibit the best behavior with stable discharge specific capacities of 120 and 80 mAh g(-1) at 5 and 40 mA g(-1), respectively, in the range 2.0-3.9 V vs. Na(+)/Na. These outstanding properties make this material a promising candidate to construct viable and high-performance Na-based batteries. 相似文献
958.
J Saiz-Poseu A Martínez-Otero T Roussel JK Hui ML Montero R Urcuyo MJ Maclachlan J Faraudo D Ruiz-Molina 《Physical chemistry chemical physics : PCCP》2012,14(34):11937-11943
This combined experimental (STM, XPS) and molecular dynamics simulation study highlights the complex and subtle interplay of solvent effects and surface interactions on the 2-D self-assembly pattern of a Schiff-base macrocycle containing catechol moieties at the liquid-solid interface. STM imaging reveals a hexagonal ordering of the macrocycles at the n-tetradecane/Au(111) interface, compatible with a desorption of the lateral chains of the macrocycle. Interestingly, all the triangular-shaped macrocycles are oriented in the same direction, avoiding a close-packed structure. XPS experiments indicate the presence of a strong macrocycle-surface interaction. Also, MD simulations reveal substantial solvent effects. In particular, we find that co-adsorption of solvent molecules with the macrocycles induces desorption of lateral chains, and the solvent molecules act as spacers stabilizing the open self-assembly pattern. 相似文献
959.
Dargiewicz M Biczysko M Improta R Barone V 《Physical chemistry chemical physics : PCCP》2012,14(25):8981-8989
Time-Dependent Density Functional Theory (TD-DFT) computations, with M05-2X and PBE0 functionals, have been employed for a detailed study of the Electron-Driven Proton-Transfer (PT) processes in an Adenine-Thymine Watson-Crick Base Pair in the gas phase and in solution, with the bulk solvent described by the polarizable continuum model. In the gas phase, TD-DFT computations predict that the Adenine → Thymine Charge Transfer (CT) excited state undergoes a barrierless PT reaction, in agreement with CC2 computations (S. Perun, A. Sobolewski, W. Domcke, J. Phys. Chem. A, 2006, 110, 9031.). The good agreement between the TD-DFT approach and CC2 results validates the former for the studies of excited state properties, excited state proton transfer reaction, and deactivation mechanisms in the DNA base pairs. Next, it is shown that inclusion of solvent effects significantly influences the possibility of both barrier-less excited state proton transfer and radiation-less deactivation through conical intersection with the ground state, affecting the energy of the CT excited state in the Franck-Condon region, the energy barrier associated to the PT process and the energy gap with the ground electronic state. These findings clearly indicate that environmental effects, with a special attention to proper treatment of dynamical solvation effects, have to be included for reliable computational analysis of photophysical and photochemical processes occurring in condensed phases. 相似文献
960.
Sanguineti A Monguzzi A Vaccaro G Meinardi F Ronchi E Moret M Cosentino U Moro G Simonutti R Mauri M Tubino R Beverina L 《Physical chemistry chemical physics : PCCP》2012,14(18):6452-6455
A new oxyiminopyrazole-based ytterbium chelate enables NIR emission upon UV excitation in colorless single layer luminescent solar concentrators for building integrated photovoltaics. 相似文献