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41.
42.
Rotraut Stanik 《Journal of Geometry》1985,24(1):62-73
Rectangular planes of characteristic 2 in the sense of H. KARZEL [7] will be characterized as incidence spaces with parallelism and congruence . 相似文献
43.
44.
The IR absorption in CH3OH in the vicinity of CO2 laser lines has been measured quantitatively by use of a 300 MHz tunable waveguide CO2 laser with output powers of about 3 W. Information on frequency offsets from the CO2 line centers, small signal and saturated absorption coefficients of FIR laser pump transitions is obtained. Some stronger pump transitions with frequency offsets larger than 50 MHz gave rise to the observation of 8 new FIR emission lines with wavelengths from 43 to 125 μm. 相似文献
45.
46.
Functional MR imaging in the awake monkey: effects of motion on dynamic off-resonance and processing strategies 总被引:2,自引:0,他引:2
Pfeuffer J Shmuel A Keliris GA Steudel T Merkle H Logothetis NK 《Magnetic resonance imaging》2007,25(6):869-882
Functional MR imaging of the alert, behaving monkey is being used more and more often to detect activation patterns and guide electrophysiological research investigating the neural basis of behavior. Several labs have reported fMRI data from the awake monkey, but none of them has studied and systematically corrected the effects of monkeys' motion on fMRI time series. In this study, a significant refinement of acquisition and correction strategies is reported that can be used to minimize magnetic susceptibility artifacts induced by respiration and by jaw and body movement. Real-time acquisition of sensor signals (e.g., signals induced by jaw and body movement) and MR navigator data were combined to optimize fMRI signal-correction strategies. Within trials, the artifact-induced off-resonance changes were small and mainly reflected the effects of respiration; between trials, movements caused major changes of global frequency and shim (>20 Hz/cm). Several methods were used to assess the stability of the fMRI series: k-space analysis ('dynamic intensity and off-resonance changes in k-space', dubbed DICK and DORK) and image analysis using a Laplace operator and a center-of-mass metric. The variability between trials made it essential to correct for inter-trial variations. On the other hand, images were sufficiently stable with our approach to perform fMRI evaluations on single trials before averaging of trials. Different motion correction strategies were compared: DORK, McFLIRT (rigid body model with three translations and three rotations) and 2D image alignment based on a center-of-mass detection (in-plane translation). The latter yielded the best results and proved to be fast and robust for intra- and inter-trial alignment. Finally, fMRI in the behaving monkey was tested for spatial and temporal reproducibility on a trial-to-trial basis. Highly activated voxels also displayed good reproducibility between trials. On average, the BOLD amplitude response to a short 3-s visual stimulus was close to 2%. 相似文献
47.
Self-Organized Task Allocation for Service Tasks in Computing Systems with Reconfigurable Components
Daniel Merkle Martin Middendorf Alexander Scheidler 《Journal of Mathematical Modelling and Algorithms》2008,7(2):237-254
A self-organized scheme for the allocation service tasks in adaptive or organic computing systems is proposed. Such computing
systems are highly self-organized and the components ideally adapt to the needs of users or the environment. Typically, the
components of such systems need some service from time to time in order perform their work efficiently. Since the type of
service tasks will often change in this systems it is attractive to use reconfigurable hardware to perform the service tasks.
The studied system consists of normal worker components and the helper components which have reconfigurable hardware and can
perform different service tasks. The speed with which a service task is executed by a helper depends on its actual configuration.
Different strategies for the helpers to decide about service task acceptance and reconfiguration are proposed. These task
acceptance strategies are inspired by stimulus-threshold models that are used to explain task allocation in social insects.
Analytical results for a system with two reconfigurable helpers are presented together with simulation results for larger
systems.
This work was supported by the German Research Foundation (DFG) through the project Organisation and Control of Self-Organising
Systems in Technical Compounds within SPP 1183. 相似文献
48.
49.
Temelso B Sherrill CD Merkle RC Freitas RA 《The journal of physical chemistry. A》2006,110(38):11160-11173
Symmetric and nonsymmetric hydrogen abstraction reactions are studied using state-of-the-art ab initio electronic structure methods. Second-order M?ller-Plesset perturbation theory (MP2) and the coupled-cluster singles, doubles, and perturbative triples [CCSD(T)] methods with large correlation consistent basis sets (cc-pVXZ, where X = D,T,Q) are used in determining the transition-state geometries, activation barriers, and thermodynamic properties of several representative hydrogen abstraction reactions. The importance of basis set, electron correlation, and choice of zeroth-order reference wave function in the accurate prediction of activation barriers and reaction enthalpies are also investigated. The ethynyl radical (*CCH), which has a very high affinity for hydrogen atoms, is studied as a prototype hydrogen abstraction agent. Our high-level quantum mechanical computations indicate that hydrogen abstraction using the ethynyl radical has an activation energy of less than 3 kcal mol(-1) for hydrogens bonded to an sp(2) or sp(3) carbon. These low activation barriers further corroborate previous studies suggesting that ethynyl-type radicals would make good tooltips for abstracting hydrogens from diamondoid surfaces during mechanosynthesis. Modeling the diamond C(111) surface with isobutane and treating the ethynyl radical as a tooltip, hydrogen abstraction in this reaction is predicted to be barrierless. 相似文献
50.
Summary We give a survey of known results regarding Schur-convexity of probability distribution functions. Then we prove that the
functionF(p
1,...,pn;t)=P(X1+...+Xn≤t) is Schur-concave with respect to (p
1,...,pn) for every realt, whereX
i are independent geometric random variables with parametersp
i. A generalization to negative binomial random variables is also presented. 相似文献