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61.
Let M be complete nonpositively curved Riemannian manifold of finite volume whose fundamental group Γ does not contain a finite
index subgroup which is a product of infinite groups. We show that the universal cover is a higher rank symmetric space iff is injective (and otherwise the kernel is infinite dimensional). This is the converse of a theorem of Burger–Monod. The proof
uses the celebrated Rank Rigidity Theorem, as well as a new construction of quasi-homomorphisms on groups that act on CAT(0)
spaces and contain rank 1 elements.
Received: September 2007, Accepted: March 2008 相似文献
62.
We prove that every limit group acts geometrically on a CAT(0)space with the isolated flats property. 相似文献
63.
For the first time hexaaquaaluminium(III) tetrafluoroborate has been used as a mild acid catalyst in organic synthesis. A simple method of its preparation based on the reaction of aluminium triisopropoxide and tetrafluoroboric acid in isopropanol afforded catalyst of high purity and activity. The three-component Biginelli condensation of acetoacetate esters, urea and aldehydes catalyzed by 10 mol % of [Al(H2O)6](BF4)3 in refluxing acetonitrile afforded 3,4-dihydropyrimidonones in good to high yields on multigram scales. The tolerance to acid sensitive reactants such as thienyl and furyl carbaldehydes, applicability to sterically hindered β-ketoesters and simple recyclability without losing catalytic activity make this catalyst as good replacement to literature methods. The mechanism of the reaction includes formation of the so called ‘ureido-crotonate’ rather than corresponding acylimino intermediate as found with Brønsted type catalysts. 相似文献
64.
The geometries and energies for ground and possible transition states of the quinolone (1) and pyridones (2)–(4) were calculated by the molecular-mechanics method. The calculated energy differences between ground and the lowest transition state are in good correlation (r = 0.994) with the corresponding experimental racemization energies for interconversion of enantiomers (P) (M) in (1) – (4). However, the calculated potential energy differences do not correspond to measured differences in Gibbs energies. The fact was tentatively attributed to neglection of the entropy contribution to Gibbs energies. 相似文献
65.
Tzvetkov MV Becker C Kulle B Nürnberg P Brockmöller J Wojnowski L 《Electrophoresis》2005,26(3):710-715
Whole-genome DNA amplification by multiple displacement (MD-WGA) is a promising tool to obtain sufficient DNA amounts from samples of limited quantity. Using Affymetrix' GeneChip Human Mapping 10K Arrays, we investigated the accuracy and allele amplification bias in DNA samples subjected to MD-WGA. We observed an excellent concordance (99.95%) between single-nucleotide polymorphisms (SNPs) called both in the nonamplified and the corresponding amplified DNA. This concordance was only 0.01% lower than the intra-assay reproducibility of the genotyping technique used. However, MD-WGA failed to amplify an estimated 7% of polymorphic loci. Due to the algorithm used to call genotypes, this was detected only for heterozygous loci. We achieved a 4.3-fold reduction of noncalled SNPs by combining the results from two independent MD-WGA reactions. This indicated that inter-reaction variations rather than specific chromosomal loci reduced the efficiency of MD-WGA. Consistently, we detected no regions of reduced amplification, with the exception of several SNPs located near chromosomal ends. Altogether, despite a substantial loss of polymorphic sites, MD-WGA appears to be the current method of choice to amplify genomic DNA for array-based SNP analyses. The number of nonamplified loci can be substantially reduced by amplifying each DNA sample in duplicate. 相似文献
66.
Vesna ?aplar Zlata Raza Vladislav Tomiši? Josip Po?ar Mladen ?ini? 《Tetrahedron》2004,60(37):8079-8087
Silver(I) and copper(I) complexes of C2-symmetric bis(oxazoline) ligands were studied by UV, NMR, IR, EPR and ES-MS spectroscopies. The stability constants of the Ag-1a and Ag-1b complexes with 1:1 and 1:2 stoichiometries in acetonitrile were determined by NMR spectrometric titrations. The evidence of tetrahedral coordination for complex (Ag(1a)2(+ was obtained from the complexation induced shifts (CIS) and NOEs. Mass spectra revealed the Cu(II) mediated oxidation of methylene bridge in copper complexes of 1a and 1b, which was in accordance with the UV, NMR, IR and EPR findings. The efficiency of Cu(I) complexes of methylene-bridged 1,5-bis(oxazoline)s 1 as chiral catalysts in stereoselective cyclopropanation of styrene with ethyl diazoacetate, was compared to that of the dialkylmethylene-bridged 1,5-bis(oxazoline)s 2. 相似文献
67.
Pavel Pospisil BeatriceD. Pilger Stefania Marveggio Pierre Schelling Christine Wurth Leonardo Scapozza Gerd Folkers Mario Pongracic Mladen Mintas SilvanaRaic Malic 《Helvetica chimica acta》2002,85(10):3237-3250
In the context of broadening the knowledge on substrate specificity of Herpes simplex virus type 1 thymidine kinase (HSV‐1 TK) and Varicella‐Zoster virus thymidine kinase (VZV TK), new derivatives of 9‐(2‐hydroxypropyl)‐substituted adenine, chloropurine, hypoxanthine, guanine, thiopurine, and (methylsulfanyl)purine were synthesized and subjected to in vitro phosphorylation and binding affinity assays. The interactions between the compounds and the crystallographically determined active site residues of HSV‐1 TK have been studied by molecular modeling with the Lamarckian genetic algorithm of docking program AutoDock 3.0. All compounds mentioned bind to both enzymes in the low mM to sub‐mM range, comparable to binding affinities of existing prodrugs. Findings from the docking procedure indicate multiple binding modes for all of the compounds and are in accordance with the results of phosphorylation and binding‐affinity studies. Furthermore, the studies reveal that hypoxanthine derivatives represent a new class of TK substrates and thiopurine derivatives a new class of TK inhibitors. 相似文献
68.
Join in an orthomodular lattice is obtained inthe same form for all five quantum implications. Theform holds for the classical implication in adistributive lattice as well. Even more, the definition added to an ortholattice makes it orthomodularfor quantum implications and distributive for theclassical one. Based on this result a quantumimplication algebra with a single primitive — andin this sense unique — implication is formulated. Acorresponding classical implication algebra is alsoformulated. The algebras are shown to be special casesof a universal implication algebra. 相似文献
69.
We introduce the concept of amplifying the transverse magnetic fields produced and/or detected with inductive coils in magnetic resonance settings by using the reversible transverse susceptibility properties of magnetic nanostructures. First, we describe the theoretical formalism of magnetic flux amplification through the coil in the presence of a large perpendicular DC magnetic field (typical of magnetic resonance systems) achieved through the singularity in the reversible transverse susceptibility in anisotropic single domain magnetic nanoparticles. We experimentally demonstrate the concept of transverse magnetic flux amplification in an inductive coil system using oriented nanoparticles with uni-axial magnetic anisotropy. We also propose a composite ferromagnetic/anti-ferromagnetic core/shell nanostructure system with uni-directional magnetic anisotropy that, in principle, provides maximal transverse magnetic flux amplification. 相似文献
70.
Mladen Gros Philip T. Greenland Walter Greiner 《Zeitschrift für Physik A Hadrons and Nuclei》1977,280(1):31-37
The rotation of the quasimolecular axis in the heavy ion collision is treated dynamically by taking into account the 2pπ-2pσ electron slip. This is done by the correct quantum mechanical method in the perturbation approximation for low ion velocities. The various radiative processes resulting from initial alignments are discussed. The spectra and anisotropies are calculated. Their dependence on the electron slip is investigated. 相似文献