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81.
The reactivities of the stoichiometric and partially reduced rutile TiO2(110) surfaces towards oxygen adsorption and carbon monoxide oxidation have been studied by means of periodic density functional theory calculations within the Car-Parrinello approach. O2 adsorption as well as CO oxidation are found to take place only in the presence of surface oxygen vacancies (partially reduced surface). The oxidation of CO by molecularly adsorbed O2 at the O-vacancy site is found to have an activation energy of about 0.4 eV. When the adsorbed O2 is dissociated, the resulting adatoms can oxidize incoming gas-phase CO molecules with no barrier. In all studied cases, once CO is oxidized to form CO2, the resulting surface is defect-free and no catalytic cycle can be established. 相似文献
82.
We study J/psi production in pp collisions at BNL Relativistic Heavy Ion Collider (RHIC) within the PHENIX detector acceptance range using the color singlet and color octet mechanism which are based on perturbative QCD and nonrelativistic QCD. Here we show that the color octet mechanism reproduces the RHIC data for J/psi production in pp collisions with respect to the p(T) distribution, the rapidity distribution, and the total cross section at square root = 200 GeV. The color singlet mechanism leads to a relatively small contribution to the total cross section when compared to the octet contribution. 相似文献
83.
Arena DA Bartynski RA Nayak RA Weiss AH Hulbert SL Weinert M 《Physical review letters》2003,91(17):176403
The Pd M4VV and M5VV Auger spectra of the 0.1 ML Pd/Ag(100) dilute surface alloy have been measured using Auger-photoelectron coincidence spectroscopy. The M4VV spectrum indicates that Pd 3d(3/2) core holes have a Coster-Kronig decay rate that is approximately 10 times that of Pd metal. Our calculations show that this giant enhancement arises from the local electronic structure of excited Pd atoms at the surface. Anomalous features in the Auger line shape are similar to those seen in dilute bulk PdAg alloys, and these features in the M5VV and M4VV lines are in good agreement with theoretical predictions. 相似文献
84.
Nayak C 《Physical review letters》2000,85(1):178-181
We show that slave particles are always confined in U(1) gauge theories of interacting electron systems. Consequently, the low-lying degrees of freedom are different from the slave particles. This is done by constructing a dual formulation of the slave-particle representation in which the no-double-occupancy constraint becomes linear and, hence, soluble. Spin-charge separation, if it occurs, is due to the existence of solitons with fractional quantum numbers in a particular dual action. 相似文献
85.
The electron-phonon interaction in the periodic Anderson model (PAM) is considered. The PAM incorporates the effect of onsite
Coulomb interaction (U) between f-electrons. The influence of Coulomb correlation U on the phonon response of the system is studied by evaluating the phonon spectral function for various parameters of the
model. The numerical evaluation of the spectral function is carried out in the long wavelength limit at finite temperatures
keeping only linear terms in U. The observed behaviour is found to agree well with the general features obtained experimentally for some heavy fermion (HF)
systems. 相似文献
86.
87.
88.
Padma L. Nayak 《高分子科学杂志,C辑:聚合物评论》2013,53(2):267-296
Polymer chemists have been successful in applying polymerization techniques to develop copolymers of natural and synthetic macromolecules [l]. The literature abounds with examples of the successful formation of copolymers from natural and synthetic macromolecules [2–5]. Copolymerization is attractive to chemists as a means of modifying macromolecules since, in general, degradation can be minimized. Despite the heterogeneity and complexity of these copolymers, much has been achieved in their characterization. The desirable properties of the polymer are retained and additional properties are acquired through the added polymer. The desired material may be formed in situ by polymerization of a monomer or monomers, by condensation of reactants, or by the decomposition of a preformed polymer. 相似文献
89.
The process of infrared multiple photon dissociation (IRMPD) of molecules is of great fundamental importance and has practical
significance, such as isotope separation etc. Unfortunately, a clear insight into the process has been hindered by the bewildering
array of important variables affecting MPD. The dissociation probability γ (φ) i.e. the yield has been found to be a sensitive
function of laser fluence φ along with numerous other parameters like laser frequency, gas pressure etc. We have shown that
in single frequency IRMPD, an accurate quantitative characterization of the dissociation probability can be adequately expressed
by a ‘power law’ model with two fitting parameters namely critical fluence, φc and multiphoton order,m. This model was exploited in analysing our MPD results on various systems. However, the small isotope shift encountered in
heavy elements and the sticking phenomenon observed in small light molecules restrict respectively the separation factor and
the dissociation yield. These problems can effectively be tackled by irradiation with multifrequency laser beams which can
be chosen appropriately on the basis of spectroscopic features. Based on our success in single frequency model, multifrequency
IRMPD is modelled by a functional form containing the product of power law terms for individual fluences on irradiation frequencies.
This model is successfully benchmarked with our experimental results on multifrequency LIS of tritium. Such knowledge can
be utilized for appropriate separation process design, evaluation and optimization. 相似文献
90.