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111.
Eriksen Hammer Stine Ebert Martin Weinbruch Stephan 《Analytical and bioanalytical chemistry》2019,411(8):1633-1645
Analytical and Bioanalytical Chemistry - Individual aerosol particles from an urban background site in Mainz (Germany), a traffic hotspot site in Essen (Germany), the free troposphere in the Swiss... 相似文献
112.
Sungsik Lee Dr. Luis M. Molina Dr. María J. López Prof. Julio A. Alonso Prof. Bjørk Hammer Prof. Byeongdu Lee Dr. Sönke Seifert Dr. Randall E. Winans Dr. Jeffrey W. Elam Dr. Michael J. Pellin Dr. Stefan Vajda Dr. 《Angewandte Chemie (International ed. in English)》2009,48(8):1467-1471
Epoxidation made easy : Subnanometer gold clusters immobilized on amorphous alumina result in a highly active and selective catalyst for propene epoxidation. The highest selectivity is found for gas mixtures involving oxygen and water, thus avoiding the use of hydrogen. Ab initio DFT calculations are used to identify key reaction intermediates and reaction pathways. The results confirm the high catalyst activity owing to the formation of propene oxide metallacycles. Al green, Au yellow, O red, and C gray.
113.
Michael E. Hammer 《PAMM》2011,11(1):217-218
We will present a comparison between two formulations of the normal vector field for contact algorithms based on the mortar method. First the non steady normal field is discussed. The non steadiness is a result of the C0 continuity of the boundary discretization. This is the common result if one discretize the domain with classical finite element methods. Second we will present results for a special normal field distribution. We average the nodal normal vector of two ascending edges and interpolate this nodal normal throughout the edges. We have implemented both methods and present comparisons based on numerical experiments. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
114.
Odoi MY Hammer NI Sill K Emrick T Barnes MD 《Journal of the American Chemical Society》2006,128(11):3506-3507
The temporal and spectral properties of luminescence from individual CdSe quantum dot-oligophenylene vinylene nanostructures (single quantum dots with conjugated organic ligands coordinated to the surface) are profoundly modified relative to blended films of the same components. These kinds of composite quantum dot-conjugated organic systems have attracted significant interest as a way to improve efficiency in photovoltaic device applications. By direct functionalization of the dot surface with the conjugated organic ligands, we realize a significant enhancement in energy transfer and luminescence stability. 相似文献
115.
Two distinct non-mirror-symmetric conformations of D- and L-cysteine were found after adsorption on Au(17 11 9)S. This demonstrates chiral heterorecognition, i.e., enantioselectivity of S kinks on vicinal Au(111). The structures as determined by angle scanned x-ray photoelectron diffraction agree well with those from density functional theory calculations. The calculations predict adsorption energies of approximately 2 eV where D-cysteine binds 140 meV stronger than L-cysteine. The classical three point contact model for molecular recognition fails to explain these findings. 相似文献
116.
We derive the generalization of Wigner’s causality bounds and Bethe’s integral formula for the effective range parameter to arbitrary dimension and arbitrary angular momentum. We also discuss the impact of these constraints on the separation of low- and high-momentum scales and universality in low-energy scattering. Some of our results were summarized earlier in a letter publication. In this work, we present full derivations and several detailed examples. 相似文献
117.
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119.
Shin JW Hammer NI Johnson MA Schneider H Glöss A Weber JM 《The journal of physical chemistry. A》2005,109(14):3146-3152
The (CO2)n- clusters are thought to accommodate the excess electron by forming a localized molecular anion, or "core ion", solvated by the remaining, largely neutral CO2 molecules. Earlier studies interpreted discontinuities in the (CO2)n- photoelectron spectra to indicate that both the CO2- and C2O4- species were present in a size-dependent fashion. Here we use vibrational predissociation spectroscopy to unambiguously establish the molecular structures of the core ions in the 2 < or = n < or = 17 size range. Spectra are reported in the 2300-3800 cm(-1) region, which allows us to independently monitor the contribution of each ion through its characteristic overtone and combination bands. These signature bands are observed to be essentially intact in the larger clusters, establishing that the CO2- and C2O4- molecular ions are indeed the only electron accommodation modes at play. The size dependence of the core ion suggested in earlier analyses of the photoelectron spectra is largely confirmed, although both species are present over a range of clusters near the expected critical cluster sizes, as opposed to the prompt changes inferred earlier. Perturbations in the bands associated with the nominally neutral CO2 "solvent" molecules are correlated with the changes in the molecular structure of the core ion. These observations are discussed in the context of a diabatic model for electron delocalization over the CO2 dimer. In this picture, the driving force leading to the transient formation of the monomer ion is traced to the solvent asymmetry inherent in an incomplete coordination shell. 相似文献
120.
Methylcobalt Compounds with Non-chelating Ligands, IV. Monoolefin Complexes Tris(trimethylphosphane)cobalt(I) halides in ether solvents saturated with olefin at low temperatures from monoolefin complexes which are prone to dissociation. Upon reaction with methyl-or phenyllithium more stable compounds are formed of the composition CoR(CC)L3 ( 1 – 4 ) (R CH3; CC C2H4, C3H6, cyclo-C5H8; R C6H5; CC C2H4; L P(CH3)3). In solution the fluctional molecules adopt a ground state structure containing a σ-bonded group and an olefin ligand in adjacent positions (trigonal-bipyramidal: CH3 axial and C2H4 equatorial or C6H5 and C2H4 equatorial). The latter arrangement is confirmed for the crystalline state by an X-ray structure determination of (ethene)phenyltris(trimethylphosphane)cobalt ( 4 ). An equatorial plane of coordination along a Co P bond not only contains both ethene-C atoms but also all the atoms of the phenyl group. The compound is thermally decomposed to give biphenyl and (ethene)tris-(trimethylphosphane)cobalt(0). No products of an olefin insertion reaction are observed. 相似文献