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991.
Jorge Gimenez‐Lopez Christian Tihic Rasmussen Hamid Hashemi Maria U. Alzueta Yide Gao Paul Marshall C. Franklin Goldsmith Peter Glarborg 《国际化学动力学杂志》2016,48(11):724-738
A detailed chemical kinetic model for oxidation of acetylene at intermediate temperatures and high pressure has been developed and evaluated experimentally. The rate coefficients for the reactions of C2H2 with HO2 and O2 were investigated, based on the recent analysis of the potential energy diagram for C2H3 + O2 by Goldsmith et al. and on new ab initio calculations, respectively. The C2H2 + HO2 reaction involves nine pressure‐ and temperature‐dependent product channels, with formation of triplet CHCHO being dominant under most conditions. The barrier to reaction for C2H2 + O2 was found to be more than 50 kcal mol?1 and predictions of the initiation temperature were not sensitive to this reaction. Experiments were conducted with C2H2/O2 mixtures highly diluted in N2 in a high‐pressure flow reactor at 600–900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel‐rich conditions. Model predictions were generally in satisfactory agreement with the experimental data. Under the investigated conditions, the oxidation pathways for C2H2 are more complex than those prevailing at higher temperatures and lower pressures. Acetylene is mostly consumed by recombination with H to form vinyl (reducing conditions) or with OH to form a CHCHOH adduct (stoichiometric to lean conditions). Both C2H3 and CHCHOH then react primarily with O2. The CHCHOH + O2 reaction leads to formation of significant amounts of glyoxal (OCHCHO) and formic acid (HOCHO), and the oxidation chemistry of these intermediates is important for the overall reaction. 相似文献
992.
Alejandra M. P. Mendez Darío M. Mitnik Jorge E. Miraglia 《International journal of quantum chemistry》2016,116(24):1882-1890
This work presents exchange potentials for specific orbitals calculated by inverting Hartree–Fock wavefunctions. This was achieved by using a Depurated Inversion Method. The basic idea of the method relies on the substitution of Hartree–Fock orbitals and eigenvalues into the Kohn–Sham equation. Through inversion, the corresponding effective potentials were obtained. Further treatment of the inverted potential should be carried on. The depuration is a careful optimization which eliminates the poles and also ensures the fullfilment of the appropriate boundary conditions. The procedure developed here is not restricted to the ground state or to a nodeless orbital and is applicable to all kinds of atoms. As an example, exchange potentials for noble gases and term‐dependent orbitals of the lower configuration of Nitrogen are calculated. The method allows to reproduce the input energies and wavefunctions with a remarkable degree of accuracy. 相似文献
993.
Enhancing the Photocatalytic Activity of Sr4Al14O25: Eu2+, Dy3+ Persistent Phosphors by Codoping with Bi3+ Ions 下载免费PDF全文
Carlos R. García Jorge Oliva Maria Teresa Romero Luis A. Diaz‐Torres 《Photochemistry and photobiology》2016,92(2):231-237
The photocatalytic activity of Bismuth‐codoped Sr4Al14O25: Eu2+, Dy3+ persistent phosphors is studied by monitoring the degradation of the blue methylene dye UV light irradiation. Powder phosphors are obtained by a combustion synthesis method and a postannealing process in reductive atmosphere. The XRD patterns show a single orthorhombic phase Sr4Al14O25: Eu2+, Dy3+, Bi3+ phosphors even at high Bismuth dopant concentrations of 12 mol%, suggesting that Bi ions are well incorporated into the host lattice. SEM micrographs show irregular micrograins with sizes in the range of 0.5–20 μm. The samples present an intense greenish‐blue fluorescence and persistent emissions at 495 nm, attributed to the 5d–4f allowed transitions of Eu2+. The fluorescence decreases as Bi concentration increases; that suggest bismuth‐induced traps formation that in turn quench the luminescence. The photocatalytic evaluation of the powders was studied under both 365 nm UV and solar irradiations. Sample with 12 mol% of Bi presented the best MB degradation activity; 310 min of solar irradiation allow 100% MB degradation, whereas only 62.49% MB degradation is achieved under UV irradiation. Our results suggest that codoping the persistent phosphors with Bi3+ can be an alternative to enhance their photocatalytic activity. 相似文献
994.
995.
To define a metric or a similarity relation with good properties is a crucial issue in most analogy and rule induction oriented methods for multicriteria sorting. Here, we propose a valued indifference (closeness) relation which is inspired on concordance and discordance measures. The criterion “weights” are obtained from the preferential information embedded in a reference set. This proposal performs very well in several practical problems. 相似文献
996.
Jose A. López‐Barrera Alejandro Avila‐Ortega Juan Morales Jorge Cervantes Roberto Olayo 《应用有机金属化学》2007,21(10):858-861
The surface of quarry stone was modified by continuous plasma polymerization of hexamethyldisiloxane. The hydrophilic surface of the quarry stone was made hydrophobic and impermeable to water. Three different reaction times were analyzed. All of them resulted in the formation of a homogenous layer on the quarry stone surface. Contact angle and FT‐IR analyses show that the hydrophobic character of the surface is due to methyl groups on the surface. The change in the contact angle with temperature and the wetting temperature (Tw) are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
997.
We prove existence theorems for two-dimensional, noncompact, complete minimal surfaces in ℝn of annular type, which span a given contour and have a finite total curvature end and prescribed asymptotical behavior. For
arbitrary rectifiable Jordan curves, we show the existence of such surfaces with a flat end, i.e., within a bounded distance
from a 2-plane. For more restricted classes of curves, we prove the existence of minimal surfaces with higher multiplicity
flat ends as well as of surfaces with polynomial-type nonflat ends.
__________
Translated from Sovremennaya Matematika. Fundamental’nye Napravleniya (Contemporary Mathematics. Fundamental Directions),
Vol. 17, Differential and Functional Differential Equations. Part 3, 2006. 相似文献
998.
Analysis of biodiesel and frying vegetable oils by means of FTIR
photoacoustic spectroscopy 总被引:1,自引:0,他引:1
S. M. Lima T. Izida M. S. Figueiredo L. H.C. Andrade P. V. Del Ré N. Jorge E. Buba F. Aristone 《The European physical journal. Special topics》2008,153(1):535-537
Fourier Transform Infrared Photoacoustic Spectroscopy was
used to determine the mid-infrared vibrational modes of biodiesel and
vegetable oils. Our results indicate that this method can contribute
significantly to the biodiesel wash process during the sample preparation.
Besides, by analyzing the spectra of vegetable oils used to fry snacks we
could to monitor the degradation in function of the fried time. 相似文献
999.
This paper deals with the stability of the feasible set mapping of linear systems of an arbitrary number (possibly infinite) of equations and inequalities such that the variable x ranges on a certain fixed constraint set X?? n (X could represent the solution set of a given constraint system, e.g., the positive cone of ? n in the case of sign constraints). More in detail, the paper provides necessary as well as sufficient conditions for the lower and upper semicontinuity (in Berge sense), and the closedness, of the set-valued mapping which associates, with any admissible perturbation of the given (nominal) system its feasible set. The parameter space is formed by all the systems having the same structure (i.e., the same number of variables, equations and inequalities) as the nominal one, and the perturbations are measured by means of the pseudometric of the uniform convergence. 相似文献
1000.
[reaction: see text] A synthetic approach toward the liposidomycins, a family of complex nucleoside-type antibiotics, is reported based on the synthesis of epoxy-amides derived from the reaction of sulfur ylides with the uridyl aldehyde derivative 6. To this end, the epoxy-amide derivative of indoline 14 was stereoselectively prepared and, after treatment with DDQ, transformed into the corresponding N-indole epoxyamide 15. The indole 15 provides ready access to a variety of structures related to the diazepanone core present in the liposidomycins by reaction with a variety of amines. 相似文献