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991.
992.
We study the vortex glass transition in disordered high temperature superconductors using Monte Carlo simulations. We use a random pinning model with strong point-correlated quenched disorder, a net applied magnetic field, long-range vortex interactions, and periodic boundary conditions. From a finite size scaling study of the helicity modulus, the rms current, and the resistivity, we obtain critical exponents at the phase transition. The new exponents differ substantially from those of the gauge glass model, but are close to those of the pure three-dimensional XY model. 相似文献
993.
Mats Anders Olofsson 《Proceedings of the American Mathematical Society》2001,129(2):515-524
We prove that every non quasi-analytic Carleman class contains functions whose graph supports measures that are absolutely continuous with respect to arc length measure and yet they have independent convolution powers in the measure algebra . The proof relies on conditions which ensure that the canonical map between two Cantor sets can be extended to a function in an arbitrary prescribed non quasi-analytic Carleman class.
994.
Wasse JC Howard CA Thompson H Skipper NT Delaplane RG Wannberg A 《The Journal of chemical physics》2004,121(2):996-1004
The microscopic structures of calcium-ammonia solutions have been established by using neutron diffraction. Total structure factors measured at 230 K reveal immediately the evolution of an uncommonly intense diffraction prepeak in the metallic solutions. As concentration is increased from 4 mole percent metal to 10 mole percent metal (i.e., saturation), this feature intensifies and shifts from 0.6 to 0.9 A(-1). It is therefore evidence of well developed intermediate-range ordering among the solvated cations, and is a microstructural signature of the observed strong phase separation of metallic (concentrated) and nonmetallic (dilute) solutions. The technique of isotopic labelling of *N by 15N was then used in conjunction with difference analysis to focus on the solvent structure in metallic solutions at 4 and 10 mole percent metal. These nitrogen-centered functions are analyzed in conjunction with classical Monte Carlo computer simulation techniques, to provide us with detailed insight into the calcium solvation and the extent of hydrogen bonding. We find that calcium is solvated by approximately 6-7 ammonia molecules, with a Ca-N distance of around 2.45 A. There is evidence of hydrogen bonding among the solvent molecules, even in the saturated 10 mole percent metal solution. 相似文献
995.
Holm A Solbu K Molander P Lundanes E Greibrokk T 《Analytical and bioanalytical chemistry》2004,378(7):1762-1768
A rapid and sensitive method for the determination of the phthalate monoesters monoethyl phthalate (MEP), monobutyl phthalate (MBP), monobenzyl phthalate (MBzP) and monoethylhexyl phthalate (MEHP), in human urine, using packed capillary column liquid chromatography coupled to electrospray quadrupole-ion trap mass spectrometry (ESI-QITMSn) has been developed. Sample volumes of 200 L of deconjugated and diluted urine were loaded onto a precolumn of 30 mm×0.32 mm I.D. packed with Hypercarb 5 m particles, using a sample carrier consisting of acetonitrile/water (15/85, v/v, adjusted to pH 2 using HCl) with a flow rate of 20 L/min. Backflushed elution onto a 100 mm×0.32 mm I.D. analytical column packed with 5 m Hypercarb particles was conducted using a tetrahydrofuran/water gradient where both solvents contained 10 mM ammonium acetate, at a flow rate of 4 L/min. Determination of the monophthalates was achieved within 8 min. Ionization was performed in the negative mode and the analytes were observed as [M-H]– at m/z=193.1, 221.1, 255.1 and 277.0 for MEP, MBP, MBzP and MEHP, respectively. Quantification was performed in the multiple reaction monitoring (MRM) mode monitoring the fragments at m/z=121.1, 177.0, 183.0 and 233.0 for MEP, MBP, MBzP and MEHP, respectively. The method was validated over the concentration range 2.5–125 ng/mL in pretreated urine samples, corresponding to 25–1250 ng/mL untreated urine, yielding correlation coefficients in the range 0.996–0.999. The within-assay (n=6) and between-assay (n=6) repeatabilities were in the range 4.0–18% and 4.8–15% RSD, respectively. The mass limits of detection were in the range 32–70 pg, corresponding to concentration limits of detection of 1.6–3.5 ng/mL of untreated urine. 相似文献
996.
Hjelm J Constable EC Figgemeier E Hagfeldt A Handel R Housecroft CE Mukhtar E Schofield E 《Chemical communications (Cambridge, England)》2002,(3):284-285
A new rod-like coordination polymer consisting of (Ru-(terpy)2) motifs bridged by bithiophene units has been prepared by electrochemical polymerisation in acidic organic medium. 相似文献
997.
Middleton DA Peng X Saunders D Shankland K David WI Markvardsen AJ 《Chemical communications (Cambridge, England)》2002,(17):1976-1977
Solid-state NMR is used to dramatically improve the efficiency and reliability of molecular crystal structure determination from X-ray powder diffraction data. 相似文献
998.
K. Anders 《Zeitschrift für Physik B Condensed Matter》1964,2(4):294-333
The thermal expansion coefficients of the following metals in the temperature region between 1,5° and 12°K have been measured: Al, Pb, Pt, Mo, Ta, W, Mg, Cd, Re, Ti, La, Ce, Nd, Gd, Yb. Except for tantalum all the specimens were polycrystalline. Is is found in accordance with theoretical prediction that the coefficient of thermal expansionβ=1/V (?V/?T) [whereV = volume,T = temperature] at sufficiently low temperatures is composed of an electronic component varying linearly with temperature, and a lattice component varying as the cube of the temperature. The electronic component is strongly modified in the superconducting state (Pb, Ta, La). The rare earth metals Gd, Ce and Nd have negative anomalies in their expansion. These are connected with the ferro- and antiferromagnetism of these substances. The results are discussed on the basis of lattice dynamics and the theory of electrons in metals. 相似文献
999.
Anders Gustavsson 《Spectrochimica Acta Part B: Atomic Spectroscopy》1984,39(1):85-94
A review of the theory for the separation of large droplets in aerosol chambers related to analytical spectroscopy is given. The theoretical treatment is used for discussing practical aspects and the behaviour of aerosol chambers. It is shown that the theories presented can be used for explaining the characteristics of aerosol chambers. The most likely processes describing the separation of large droplets in aerosol chambers are inertial deposition processes. Cyclone and jet impaction are the most interesting concepts for designing new types of aerosol chambers for atomic spectroscopy. 相似文献
1000.
The properties of the plasma of an underexpanded jet in air were examined by optical and by probe methods as described in a previous paper (Contrib. Plasma Phys. 27 (1987) 203). The jet was produced by an erosion plasmatron with xenon-filling operating in a single-pulse regime. Now, independent measurements of the space-time development of the electron density by microwave interferometry are described. The results of cut-off and phase shift measurements are in agreement with those obtained by probe diagnostics. 相似文献