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991.
M. Imoto S. Kusumoto T. Shiba E.Th. Rietschel C. Galanos O. Lüderitz 《Tetrahedron letters》1985,26(7):907-908
The chemical structure of E. coli lipid A was elucidated to be by determination of the nature of the individual acyl groups bound to the two hydroxyl groups in positions 3,3′ and the two amino groups of the D-glucosamine disaccharide phosphate backbone. 相似文献
992.
Influence of the Ring Atoms on the Structure of Triel‐Pentel Heterocycles – Synthesis and X‐Ray Crystal Structures of [Me2InAs(SiMe3)2]2 and [Me2InSb(SiMe3)2]3 Triel‐pentel heterocycles [Me2InE(SiMe3)2]x have been prepared by dehalosilylation reactions from Me2InCl and E(SiMe3)3 (E = As, x = 2; E = Sb, x = 3) and characterised by NMR spectroscopy and by X‐ray crystal structure analyses. In addition the X‐ray crystal structures of [Me2GaAs(SiMe3)2]2 and [Me2InP(SiMe3)2]2 are reported. The compounds complete a family of 13 identically substituted heterocycles [Me2ME(SiMe3)2]x (M = Al, Ga, In; E = N, P, As, Sb, Bi; x = 2, 3), whose structures were investigated depending on the ring atoms M and E. The tendencies that have been observed concerning the ring sizes can be explained by the interplay of the atomic radii of the central atoms and the sterical demand of the ligands. After a formal separation of the M–E bonds in σ bonds and dative bonds the characteristic differences and trends in the endocyclic and exocyclic bond angles of both centres M and E can be interpreted on the basis of a simple Lewis acid/base adduct model. 相似文献
993.
Th. Ramdahl J. Arey B. Zielinska R. Atkinson A. M. Winer 《Journal of separation science》1986,9(9):515-517
This paper reports the retention indices of eighteen of the possible twenty-five dinitrofluoranthene isomers. 相似文献
994.
Ch. Gerz Th. Hilberath G. Werth 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1987,5(2):97-99
Sr+ ions were confined in a r.f. quadrupole trap for times of the order of 30 min. The metastable 4D states were populated via laser excitation of the 5P states. The weak quadrupole transition rate into the 5S 1/2 ground state at 674 and 687 nm was deduced from observation of the exponential decay. At background pressures above 10?7 mbar the radiative decay is dominated by collisional quenching. Extrapolation of the observed decay rate to zero background pressure yields the radiative lifetimes. At pressures around 10?6 mbar fine structure mixing collisions between the 4D states have been observed, which lead to corrections of the extrapolated lifetimes. As the final result we obtain 395±38 ms for 4D 3/2 and 345±33 ms for 4D 5/2. These results are somewhat higher than theoretical predictions. 相似文献
995.
Caputo CB Geier SJ Ouyang EY Kreitner C Stephan DW 《Dalton transactions (Cambridge, England : 2003)》2012,41(1):237-242
The reaction of tBu(C(6)H(4)O(2))P, with the borane B(C(6)F(5))(3) gives rise to NMR data consistent with the formation of the classical Lewis acid-base adduct tBu(C(6)H(4)O(2))P(B(C(6)F(5))(3)) (1). In contrast, the NMR data for the corresponding reactions of tBu(C(20)H(12)O(2))P and Cl(C(20)H(12)O(2))P with B(C(6)F(5))(3) were consistent with the presence of equilibria between free phosphine and borane and the corresponding adducts. Nonetheless, in each case, the adducts tBu(C(20)H(12)O(2))P(B(C(6)F(5))(3)) (2) and Cl(C(20)H(12)O(2))P(B(C(6)F(5))(3)) (3) were isolable. The species 1 reacts with PhCCH to give the new species tBu(C(6)H(4)O(2))P(Ph)C=CHB(C(6)F(5))(3) (4) in near quantitative yield. In an analogous fashion, the addition of PhCCH to solutions of the phosphines tBu(C(20)H(12)O(2))P, tBuPCl(2) and (C(6)H(3)(2,4-tBu(2))O)(3)P each with an equivalent of B(C(6)F(5))(3) gave rise to L(Ph)C=CHB(C(6)F(5))(3) (L = tBu(C(20)H(12)O(2))P 5, tBuPCl(2)6 and (C(6)H(3)(2,4-tBu(2))O)(3)P 7). X-Ray data for 1, 2, 6 and 7 are presented. The implications of these findings are considered. 相似文献
996.
G. Th?mmes J. Becker M. Junk A.K. Vaikuntam D. Kehrwald A. Klar K. Steiner A. Wiegmann 《Journal of computational physics》2009,228(4):1139-1156
We consider the lattice Boltzmann method for immiscible multiphase flow simulations. Classical lattice Boltzmann methods for this problem, e.g. the colour gradient method or the free energy approach, can only be applied when density and viscosity ratios are small. Moreover, they use additional fields defined on the whole domain to describe the different phases and model phase separation by special interactions at each node. In contrast, our approach simulates the flow using a single field and separates the fluid phases by a free moving interface. The scheme is based on the lattice Boltzmann method and uses the level set method to compute the evolution of the interface. To couple the fluid phases, we develop new boundary conditions which realise the macroscopic jump conditions at the interface and incorporate surface tension in the lattice Boltzmann framework. Various simulations are presented to validate the numerical scheme, e.g. two-phase channel flows, the Young–Laplace law for a bubble and viscous fingering in a Hele-Shaw cell. The results show that the method is feasible over a wide range of density and viscosity differences. 相似文献
997.
Stephan Michel Jason Itri Jung H Han Kathryn Gniotczynski Christopher S Colwell 《BMC neuroscience》2006,7(1):15-11
Background
Previous studies indicate that light information reaches the suprachiasmatic nucleus (SCN) through a subpopulation of retinal ganglion cells that contain both glutamate and pituitary adenylyl cyclase activating peptide (PACAP). While the role of glutamate in this pathway has been well studied, the involvement of PACAP and its receptors are only beginning to be understood. Speculating that PACAP may function to modulate how neurons in the suprachiasmatic nucleus respond to glutamate, we used electrophysiological and calcium imaging tools to examine possible cellular interactions between these co-transmitters. 相似文献998.
Abdullin S. Banerjee S. Bellucci L. Charlot C. Denegri D. Dittmar M. Drollinger V. Dubinin M.N. Dzelalija M. Green D. Iasvili I. Ilyin V.A. Kinnunen R. Kunori S. Lassila-Perini K. Lehti S. Mazumdar K. Moortgat F. Muller Th. Nikitenko A. Puljak I. Salmi P. Seez C. Slabospitsky S. Stepanov N. Vidal R. Wu W. Yildiz H.D. Zeyrek M. 《The European Physical Journal C - Particles and Fields》2005,39(2):41-61
The European Physical Journal C - This work summarizes the studies for the Higgs boson searches in CMS at the LHC collider. The main discovery channels are presented and the potential is given for... 相似文献
999.
L. A. Oparina M. Ya. Khil’ko N. A. Chernyshova S. I. Shaikhudinova L. N. Parshina Th. Preiss J. Henkelmann B. A. Trofimov 《Russian Journal of Organic Chemistry》2005,41(5):661-666
A new catalytic system CsF-NaOH was developed for the synthesis of mono- and divinyl ethers of alkanediols exceeding in efficiency KOH. The nucleophilic addition of diols to acetylene in the presence of this system occurs both at enhance pressure (without solvent, 140–160°C) and atmospheric pressure (in DMSO medium, 100°C) of acetylene. Conditions were established of a selective preparation in a high yield of divinyl ethers from diols.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 677–683.Original Russian Text Copyright © 2005 by Oparina, Khil’ko, Chernyshova, Shaikhudinova, Parshina, Preiss, Henkelmann, Trofimov. 相似文献
1000.
G. Campi E. Cappelluti Th. Proffen X. Qiu E. S. Bozin S. J.L. Billinge S. Agrestini N. L. Saini A. Bianconi 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):15-21
We have studied temperature evolution of the local as well as the
average crystal structure of MgB2 using real-space atomic pair
distribution function (PDF) measured by high resolution neutron powder
diffraction in a wide temperature range of T=10–600 K. We find small
positive correlation factors for the B–B and B–Mg pairs, determined by
mean-square displacements (MSD) and the mean-square relative
displacements (MSRD). We analyze the PDF using both Einstein and
force constant models finding a good agreement between the
experimental data and the two models. This indicates that B and Mg
atomic correlations are not sensitive to the details of phonon
dispersion. 相似文献