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941.
942.
J M Mathias 《OR manager》1999,15(4):27, 29-30, 32
943.
The electronic structure of hydrogen adsorbate-induced states on Gd(0001) was investigated by means of photoelectron spectroscopy with linearly polarized radiation. The E vector of the incoming photon beam is rotatable. Clean and well-ordered rare-earth (0001) surfaces exhibit a highly localized surface state near the Fermi edge. After the adsorption of hydrogen, the surface state disappears and an additional sharp feature at about 4 eV binding energy is observed. For this latter
state, the ratio of the radial matrix elements as well as the relative phase shifts were determined to be R=Rp/Rf=2.4±0.3 and δf−δp=310±10°, respectively. The removal of the Gd surface state by hydrogen adsorption was investigated by means of scanning tunneling microscopy (STM) and spectroscopy (STS). The removal of the surface state exhibits domain-like behavior, with surface steps acting as domain boundaries. The tunneling spectra reveal that hydrogen adsorption causes a dramatic reduction in the differential conductivity near the Fermi level. 相似文献
944.
A nuclear reactor core, that is a few meters in height and diameter is composed of hundreds of fuel assemblies which are again composed of tenth of fuel rods with a diameter of about 10 mm. The relevant length scales for a Computational Fluid Dynamics (CFD) simulations range from the sub millimetre range, relevant for the sub channels up to several meters. Describing such a multi-scale situation with CFD is extremely challenging and the traditional approach is to use integral methods. These are sub channel and sub assembly analyses codes requiring closure by empirical and experimental correlations. A CFD simulation of a complete nuclear reactor set up resolving all relevant scales requires exceedingly large computational resources. However, in many cases there exists repetitive geometrical assemblies and flow patterns. Based on this observation the general approach of creating a parametrized model for a single segment and composing many of these reduced models to obtain the entire reactor simulation becomes feasible. With the Coarse-Grid-CFD (CGCFD) ( [1], [2]), we propose to replace the experimental or empirical input with proper CFD data. Application of the methodology starts with a detailed, well-resolved, and verified CFD simulation of a single representative segment. From this simulation we extract in tabular form so-called volumetric forces which upon parametrization is assigned to all coarse cells. Repeating the fine simulation for multiple flow conditions parametrized data can be obtained or interpolated for all occurring conditions to the desired degree of accuracy. Note, that parametrized data is used to close an otherwise strongly under-resolved, coarsely meshed model of a complete reactor set up. Implementation of volumetric forces are the method of choice to account for effects as long as dominant transport is still distinguishable on the coarse mesh. In cases where smaller scale effects become relevant the Anisotrop Porosity Formulation (APF) allows capturing transport phenomena occurring on the same or slightly smaller scale compared to the coarse mesh resolution. Within this work we present results of several fuel assemblies, that were investigated with our methodology. In particular, we show Coarse-Grid-CFD simulations including a 127 pin LBE cooled wire wrapped fuel assembly. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
945.
We present the software framework EWE, which is designed for coupled electromechanical simulations in computational cardiology. EWE is build on the multi-physics framework MOOSE. Numerical simulations of coupled problems on an idealized geometry for a left ventricle are shown. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
946.
Vitaly Sineshchekov Joel Mailliet Georgios Psakis Kathleen Feilke Jakub Kopycki Mathias Zeidler Lars‐Oliver Essen Jon Hughes 《Photochemistry and photobiology》2014,90(4):786-795
We report a low‐temperature fluorescence spectroscopy study of the PAS‐GAF‐PHY sensory module of Cph1 phytochrome, its Y263F mutant (both with known 3D structures) as well as Y263H and Y263S to connect their photochemical parameters with intramolecular interactions. None of the holoproteins showed photochemical activity at low temperature, and the activation barriers for the Pr→lumi‐R photoreaction (2.5–3.1 kJ mol?1) and fluorescence quantum yields (0.29–0.42) were similar. The effect of the mutations on Pr→Pfr photoconversion efficiency (ΦPr→Pfr) was observed primarily at the prelumi‐R S0 bifurcation point corresponding to the conical intersection of the energy surfaces at which the molecule relaxes to form lumi‐R or Pr, lowering ΦPr→Pfr from 0.13 in the wild type to 0.05–0.07 in the mutants. We suggest that the Ea activation barrier in the Pr* S1 excited state might correspond to the D‐ring (C19) carbonyl – H290 hydrogen bond or possibly to the hindrance caused by the C131/C171 methyl groups of the C and D rings. The critical role of the tyrosine hydroxyl group can be at the prelumi‐R bifurcation point to optimize the yield of the photoprocess and energy storage in the form of lumi‐R for subsequent rearrangement processes culminating in Pfr formation. 相似文献
947.
An Operando FTIR Spectroscopic and Kinetic Study of Carbon Monoxide Pressure Influence on Rhodium‐Catalyzed Olefin Hydroformylation
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Dr. Christoph Kubis Dr. Mathias Sawall Axel Block Prof. Dr. Klaus Neymeyr Prof. Ralf Ludwig Prof. Dr. Armin Börner Dr. Detlef Selent 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(37):11921-11931
The influence of carbon monoxide concentration on the kinetics of the hydroformylation of 3,3‐dimethyl‐1‐butene with a phosphite‐modified rhodium catalyst has been studied for the pressure range p(CO)=0.20–3.83 MPa. Highly resolved time‐dependent concentration profiles of the organometallic intermediates were derived from IR spectroscopic data collected in situ for the entire olefin‐conversion range. The dynamics of the catalyst and organic components are described by enzyme‐type kinetics with competitive and uncompetitive inhibition reactions involving carbon monoxide taken into account. Saturation of the alkyl–rhodium intermediates with carbon monoxide as a cosubstrate occurs between 1.5 and 2 MPa of carbon monoxide pressure, which brings about a convergence of aldehyde regioselectivity. Hydrogenolysis of the acyl intermediate is fast at 30 °C and low pressure of p(CO)=0.2 MPa, but is of minus first order with respect to the solution concentration of carbon monoxide. Resting 18‐electron hydrido and acyl complexes that correspond to early and late rate‐determining states, respectively, coexist as long as the conversion of the substrate is not complete. 相似文献
948.
Jörn Bruns Oliver Niehaus Prof. Dr. Rainer Pöttgen Prof. Dr. Mathias S. Wickleder 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(3):811-814
The reaction of (NO2)(CF3SO3) and elemental palladium in oleum (65 % SO3) leads to violet single crystals of Pd(HS2O7)2 (monoclinic, P21/c, Z=2, a=927.80(9), b=682.58(7), c=920.84(9) pm, β=117.756(2)°, wR2=0.0439). In the crystal structure, the Pd2+ ions show an uncommon octahedral coordination of six oxygen atoms belonging to six HS2O7? ions. The linkage of [PdO6] octahedra and the hydrogendisulfate anions leads to a layer structure, and the layers are held together by hydrogen bonds. The unusual coordination of the Pd2+ ions results in an electronic d8 high‐spin configuration, which leads to the paramagnetic behavior of the compound. Moreover, at low temperature, a ferromagnetic ordering was observed with a Curie temperature of 8 K. 相似文献
949.
Prof. René T. Boeré Janis Derendorf Prof. Carsten Jenne Dr. Sylwia Kacprzak Dr. Mathias Keßler Rainer Riebau Prof. Sebastian Riedel Dr. Tracey L. Roemmele Monika Rühle Dr. Harald Scherer Thomas Vent‐Schmidt Jonas Warneke Prof. Stefan Weber 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(15):4447-4459
The perhalogenated closo‐dodecaborate dianions [B12X12]2? (X=H, F, Cl, Br, I) are three‐dimensional counterparts to the two‐dimensional aromatics C6X6 (X=H, F, Cl, Br, I). Whereas oxidation of the parent compounds [B12H12]2? and benzene does not lead to isolable radicals, the perhalogenated analogues can be oxidized by chemical or electrochemical methods to give stable radicals. The chemical oxidation of the closo‐dodecaborate dianions [B12X12]2? with the strong oxidizer AsF5 in liquid sulfur dioxide (lSO2) yielded the corresponding radical anions [B12X12] ? ? (X=F, Cl, Br). The presence of radical ions was proven by EPR and UV/Vis spectroscopy and supported by quantum chemical calculations. Use of an excess amount of the oxidizing agent allowed the synthesis of the neutral perhalogenated hypercloso‐boranes B12X12 (X=Cl, Br). These compounds were characterized by single‐crystal X‐ray diffraction of dark blue B12Cl12 and [Na(SO2)6][B12Br12] ? B12Br12. Sublimation of the crude reaction products that contained B12X12 (X=Cl, Br) resulted in pure dark blue B12Cl12 or decomposition to red B9Br9, respectively. The energetics of the oxidation processes in the gas phase were calculated by DFT methods at the PBE0/def2‐TZVPP level of theory. They revealed the trend of increasing ionization potentials of the [B12X12]2? dianions by going from fluorine to bromine as halogen substituent. The oxidation of all [B12X12]2? dianions was also studied in the gas phase by mass spectrometry in an ion trap. The electrochemical oxidation of the closo‐dodecaborate dianions [B12X12]2? (X=F, Cl, Br, I) by cyclic and Osteryoung square‐wave voltammetry in liquid sulfur dioxide or acetonitrile showed very good agreement with quantum chemical calculations in the gas phase. For [B12X12]2? (X=F, Cl, Br) the first and second oxidation processes are detected. Whereas the first process is quasi‐reversible (with oxidation potentials in the range between +1.68 and +2.29 V (lSO2, versus ferrocene/ferrocenium (Fc0/+))), the second process is irreversible (with oxidation potentials ranging from +2.63 to +2.71 V (lSO2, versus Fc0/+)). [B12I12]2? showed a complex oxidation behavior in cyclic voltammetry experiments, presumably owing to decomposition of the cluster anion under release of iodide, which also explains the failure to isolate the respective radical by chemical oxidation. 相似文献
950.
Markus?BibingerEmail author Mathias?Vetter 《Annals of the Institute of Statistical Mathematics》2015,67(4):707-743
We consider estimation of the quadratic (co)variation of a semimartingale from discrete observations which are irregularly spaced under high-frequency asymptotics. In the univariate setting, results by Jacod for regularly spaced observations are generalized to the case of irregular observations. In the two-dimensional setup under non-synchronous observations, we derive a stable central limit theorem for the Hayashi–Yoshida estimator in the presence of jumps. We reveal how idiosyncratic and simultaneous jumps affect the asymptotic distribution. Observation times generated by Poisson processes are explicitly discussed. 相似文献