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951.
If L is a uniformly elliptic operator in non-divergence form,the boundary Harnack principle for the ratio of positive L-harmonicfunctions holds in Hölder domains of order if > . A counterexample shows that is sharp. For Hölder domainsof order with (0,1], the boundary Harnack principle holds providedthe domain also satisfies a strong uniform regularity condition. 相似文献
952.
Krzysztof KoŁodziejczyk 《Geometriae Dedicata》1996,61(3):271-278
Let
be the tiling of R
3 with unit cubes whose vertices belong to the fundamental lattice L
1 of points with integer coordinates. Denote by L
n
the lattice consisting of all points x in R
3 such that nx belongs to L
1. When the vertices of a polyhedron P in R
3 are restricted to lie in L
1 then there is a formula which relates the volume of P to the numbers of all points of two lattices L
1 and L
n
lying in the interior and on the boundary of P. In the simplest case of the lattices L
1 and L
2 there are 27 points in each cube from
whose relationships to the polyhedron P must be examined. In this note we present a new formula for the volume of lattice polyhedra in R
3 which involves only nine points in each cube of
: one from L
2 and eight belonging to L
4. Another virtue of our formula is that it does not employ any additional parameters, such as the Euler characteristic. 相似文献
953.
Krzysztof Stempak 《Monatshefte für Mathematik》1996,122(2):187-197
We supplement our previous paper [9] by adding a theorem that transplantsL
p
-norm maximal inequalities for Laguerre multipliers. As an immediate consequence we obtain negative results concerningL
p
-estimates of partial sum maximal operators for Laguerre expansions.Research supported in part by KBN grant No. 2 PO3A 030 09. 相似文献
954.
Abstract— N-Hydroxypyridine-2-thione, 2-S-PyrNOH, a potent antimicrobial, antifungal and anticancer agent, is photochemically active and upon UV irradiation generates free radicals. We have employed EPR and the spin-trap 5,5-dimethyl-l-pyrroline TV-oxide (DMPO) to investigate the photochemistry in aqueous solutions of 2-S-PyrNOH (used here in the form of a sodium salt, 2-S-PyrNONa). We found that upon photoactivation 2-S-PyrNONa can follow two different pathways: it can produce hydroxyl radicals and/or it can act as a photoreducing agent. The capacity of 2-S-PyrNONa to produce “OH” radicals has been demonstrated by: (1) EPR detection of the DMPO/OH adduct in UV-irradiated samples; (2) inhibition of the DMPO/OH formation by OH scavengers such as methyl alcohol, formate and DMSO and (3) by detection of EPR signals of DMPO adducts with radicals derived from reaction of OH with these inhibitors. The photoreductive capacity of 2-S-PyrNONa was deduced from the observation that the amplitude of the EPR signal of the spin adduct DMPO/OH decreased on UV irradiation in air-free pH 7.0 buffers and that the signal recovered in the dark and after aeration. The ability to generate free radicals upon UV irradiation suggests that 2-S-PyrNONa can be regarded as a potential photocytotoxic agent. This feature may be relevant to the biological action of this compound. Our findings also emphasize that caution should be used when 2-S-PyrNOH is employed as a source of OH radicals in biological or chemical systems. 相似文献
955.
Samuel J. Cole Krzysztof Szalewicz Rodney J. Bartlett 《International journal of quantum chemistry》1986,30(5):695-711
The interaction energy of several conformations of the nitromethane dimer is investigated at the SCF level. The dispersion energy and counterpoise correction are computed for certain relative orientations of the monomers. Fourth-order many body perturbation theory SDQ-MBPT(4) energies are reported for selected points. Double zeta and double zeta plus polarization basis sets were used. All calculations were done with the monomer fixed at the isolated monomer geometry. Interaction energies as large as 6 kcal/mol are found at minima of hydrogen bonding orientations. 相似文献
956.
Misquitta AJ Podeszwa R Jeziorski B Szalewicz K 《The Journal of chemical physics》2005,123(21):214103
Recently, three of us have proposed a method [Phys. Rev. Lett. 91, 33201 (2003)] for an accurate calculation of the dispersion energy utilizing frequency-dependent density susceptibilities of monomers obtained from time-dependent density-functional theory (DFT). In the present paper, we report numerical calculations for the helium, neon, water, and carbon dioxide dimers and show that for a wide range of intermonomer separations, including the van der Waals and short-range repulsion regions, the method provides dispersion energies with accuracies comparable to those that can be achieved using the current most sophisticated wave-function methods. If the dispersion energy is combined with (i) the electrostatic and first-order exchange interaction energies as defined in symmetry-adapted perturbation theory (SAPT) but computed using monomer Kohn-Sham (KS) determinants, and (ii) the induction energy computed using the coupled KS static response theory, (iii) the exchange-induction and exchange-dispersion energies computed using KS orbitals and orbital energies, the resulting method, denoted by SAPT(DFT), produces very accurate total interaction potentials. For the helium dimer, the only system with nearly exact benchmark values, SAPT(DFT) reproduces the interaction energy to within about 2% at the minimum and to a similar accuracy for all other distances ranging from the strongly repulsive to the asymptotic region. For the remaining systems investigated by us, the quality of the SAPT(DFT) interaction energies is so high that these energies may actually be more accurate than the best available results obtained with wave-function techniques. At the same time, SAPT(DFT) is much more computationally efficient than any method previously used for calculating the dispersion and other interaction energy components at this level of accuracy. 相似文献
957.
A novel concept for all-plastic and all-solid-state ion-selective electrodes (ISEs) is introduced. Planar, flexible ion-selective electrodes, comprising only polymeric materials, with no internal solution, were obtained. The cast conducting polymer layer (obtained from aqueous suspension) was covered with a solvent polymeric based membrane to obtain a planar all-plastic sensor. The conducting polymer layer served both as electrical contact and as ion-to-electron transducer. To illustrate this concept, the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) ions (PEDOT-PSS, Baytron P) was chosen. Due to interaction, analyte cations-poly(4-styrenesulfonate) anions, an extended linear range of potentiometric responses was obtained, with lowered detection limit.As example, Ca2+-selective and K+-selective all-plastic electrodes were fabricated and yielded with high selectivity, near Nernstian slopes and fast responses. The detection limits obtained for Ca2+- and K+-selective sensors were 5 × 10−9 M CaCl2 and 4.4 × 10−7 M KCl, respectively.The possibilities of modifying the conducting polymer-phase composition is highlighted. This method is extremely useful to tune the desired type of responses, and cannot be directly applied for electrochemically deposited conducting polymers. 相似文献
958.
Derek H.R. Barton Jean Boivin Nubar Ozbalik Kathy M. Schwartzentruber Krzysztof Jankowski 《Tetrahedron letters》1985,26(4):447-450
The high selectivity of the Gif system for hydrocarbon oxidation is shown to depend upon the capture of radicals by pyridine; the mechanism for the secondary oxidation products has only a minor radical component as judged by competitive trapping. 相似文献
959.
Cysteamine (mercaptamine) can be determined in plasma by liquid chromatography with ultraviolet detection after precolumn derivatization. The plasma is reduced with sodium borohydride in order to convert disulfides to thiols, and derivatized with 2-chloro-1-methylquinolinium tetrafluoroborate. The 2-S-quinolinium derivative of cysteamine is then separated from other thiols derivatives present in the plasma, and quantitated using high-performance liquid chromatography and then detection at 355 nm. Peaks from the main plasma thiols cysteine, cysteinylglycine, glutathione and homocysteine are also observed and can be measured as needed. The cystamine standards added to the plasma before the reduction step show that the response of the detector is linear within the range studied, from 0.1 to 40 mol/L plasma. The imprecisions at the bottom and the top of the calibration range were 11.17 and 0.8% and the inaccuracies 8.64 and 1.50%, respectively, and the lower limit of quantitation was 0.1 nmol cysteamine in 1 ml of plasma. 相似文献
960.
Gaussian type wave functions do not reproduce the interparticle cusps which result in a slow convergence of the expectation values of the operators involved in calculations of the relativistic and QED energy corrections. Methods correcting this deficiency are the main topic discussed in this paper. Benchmark expectation values of the singular operators for several few-electron systems are presented. 相似文献