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191.
192.
This article investigates the chaotic Lotka–Volterra system as an optimal nonlinear design problem for biological pest control strategies. In the biological control strategy, natural enemies are introduced such that the pest density is stabilized below the economic injury level, and the population of natural enemies remains sufficiently high to control the pests. Applying dynamic programming, this problem was reduced to the Hamilton–Jacobi–Bellman equation. The functions satisfying the reduced equation were obtained among the correspondent Lyapunov functions of the considered Lotka–Volterra system. A closed-form optimal feedback control law was derived. The effectiveness of the method is verified by numerical simulations of biological pest control. The biological implications of these results are also discussed. 相似文献
193.
The canonical point singularity of elliptically polarized light is an isolated point of circular polarization, a C point. As one recedes from such a point the surrounding polarization figures evolve into ellipses characterized by a major axis of length a, a minor axis of length b, and an azimuthal orientational angle alpha: at the C point itself, alpha is singular (undefined) and a and b are degenerate. The profound effects of the singularity in alpha on the orientation of the ellipses surrounding the C point have been extensively studied both theoretically and experimentally for over two decades. The equally profound effects of the degeneracy of a and b on the evolving shapes of the surrounding ellipses have only been described theoretically. As one recedes from a C point, a and b generate a surface that locally takes the form of a double cone (i.e., a diabolo). Contour lines of constant a and b are the classic conic sections, ellipses or hyperbolas depending on the shape of the diabolo and its orientation relative to the direction of propagation. We present measured contour maps, surfaces, cones, and diabolos of a and b for a random ellipse field (speckle pattern). 相似文献
194.
We give a corrected proof of an extension of the Robinson Splitting Theorem for the d. c. e. degrees. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
195.
Ted Schaefer Kirk Marat Alberta Lemire Alexander F. Janzen 《Magnetic resonance in chemistry : MRC》1982,18(2):90-91
In 2-trifluoromethylphenyldifluorophosphine the proximate couplings 4J(19F31P) and 5J(19F19F) are + 68.3 and + 8.3 Hz, respectively. 1J(13C31P) is ?57.0 Hz, 2J(13C-1, 10F) is + 9.9 Hz and 2J(13C-6, 13C-6, 31P) is + 10.1 Hz. The trifluoromethyl substituent induces substantial changes in some coupling constants, particularly those between the 31P and ring 13C nuclei. 相似文献
196.
P. M. Akhmet’ev 《Proceedings of the Steklov Institute of Mathematics》2012,278(1):10-21
Two new nonlocal asymptotic invariants of magnetic fields frozen into a finite domain filled with an ideal liquid conducting medium are introduced. The velocity of variation of the invariants in a nonideal medium is estimated for magnetic fields described by the induction equation. The invariants are used to study the spectral characteristics of magnetic fields. 相似文献
197.
Ab initio electronic structure theory calculations on cluster models support the characterization of the signature absorption spectrum of a solvated hydroxyl OH radical as a solvent-to-solute charge transfer state modulated by the hydrogen-bonding environment. Vertical excited states in OH(H2O)n clusters (n = 0-7, 16) calculated at the TDDFT level of theory (with companion calculations at the EOM-CCSD level of theory for n = 7) show an intense band in the region of approximately 250 nm. The calculations suggest that the intensity of the solvent-to-solute charge transfer transition depends strongly on a favorable alignment of the donor and acceptor molecular orbitals, as observed in one (n = 16) cluster. In the other (smaller) clusters, the transitions in this region were found to be weak as the clusters do not offer the necessary favorable alignment of orbitals. The present findings are consistent with the experimentally observed absorption at 230 nm that has been assigned to a solvent-to-solute charge transfer and provide insight into the electronic states and orbitals that give rise to the intensity of the band. 相似文献
198.
Ziganshin MA Yakimov AV Safina GD Solovieva SE Antipin IS Gorbatchuk VV 《Organic & biomolecular chemistry》2007,5(9):1472-1478
The effect of macrocycle size on the structure-property relationships was studied for inclusion compounds of tert-butylcalix[n]arenes (n=4,5) with volatile organic guests having various molecular size and group composition. Vapor-sorption isotherms, guest-inclusion stoichiometry and Gibbs energy, thermostability parameters and decomposition enthalpies were determined for host-guest compounds (clathrates) obtained using saturation of solid calixarene powder with guest vapor. The increase of the host macrocycle in the studied calixarene pair changes the observed structure-property relationship from the guest-binding selectivity mostly seen in inclusion Gibbs energy to the high sensitivity for guest structure in inclusion stoichiometry. The host with the larger macrocycle has more clathrates with stepwise formation and decomposition. Specific types of guest binding with solid hosts are discussed. 相似文献
199.
Zhanna DobrokhotovaAnna Emelina Aleksei SidorovGrigory Aleksandrov Mikhail Kiskin Pavel KoroteevMikhail Bykov Marat FazylbekovArtem Bogomyakov Vladimir NovotortsevIgor Eremenko 《Polyhedron》2011,30(1):132-141
Lithium-containing heterometallic complexes with cobalt (Li2Co2(Piv)6(2,4-Lut)2 (2, Piv is the pivalate anion) and Li2Co2(O2CCH2But)6(2,4-Lut)2 (3)) and with nickel (Li2Ni2(Piv)6(DME)2 (4) and Li2Ni2(Piv)6(2,2′-bpy)2 (5)) were synthesized. The structures of the complexes were established by X-ray diffraction. The magnetic properties of complexes 2 and 4 were studied. The thermal behavior of compounds 2, 3, and 5 was investigated. It was shown that the compounds under study can be used as molecular precursors for the synthesis of lithium cobaltate and nickelate. 相似文献
200.
Coates L Tuan HF Tomanicek S Kovalevsky A Mustyakimov M Erskine P Cooper J 《Journal of the American Chemical Society》2008,130(23):7235-7237
Hydrogen atoms play key roles in enzyme mechanism, but as this study shows, even high-quality X-ray data to a resolution of 1 A cannot directly visualize them. Neutron diffraction, however, can locate deuterium atoms even at resolutions around 2 A. Both neutron and X-ray diffraction data have been used to investigate the transition state of the aspartic proteinase endothiapepsin. The different techniques reveal a different part of the story, revealing the clearest picture yet of the catalytic mechanism by which the enzyme operates. Room temperature neutron and X-ray diffraction data were used in a newly developed joint refinement software package to visualize deuterium atoms within the active site of the enzyme when a gem-diol transition state analogue inhibitor is bound at the active site. These data were also used to estimate their individual occupancy, while analysis of the differences between the bond lengths of the catalytic aspartates was performed using atomic resolution X-ray data. The two methods are in agreement on the protonation state of the active site with a transition state analogue inhibitor bound confirming the catalytic mechanism at which the enzyme operates. 相似文献