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21.
Reuven Rubinstein 《Methodology and Computing in Applied Probability》2009,11(4):491-549
We present a randomized algorithm, called the cloning algorithm, for approximating the solutions of quite general NP-hard
combinatorial optimization problems, counting, rare-event estimation and uniform sampling on complex regions. Similar to the
algorithms of Diaconis–Holmes–Ross and Botev–Kroese the cloning algorithm is based on the MCMC (Gibbs) sampler equipped with
an importance sampling pdf and, as usual for randomized algorithms, it uses a sequential sampling plan to decompose a “difficult”
problem into a sequence of “easy” ones. The cloning algorithm combines the best features of the Diaconis–Holmes–Ross and the
Botev–Kroese. In addition to some other enhancements, it has a special mechanism, called the “cloning” device, which makes
the cloning algorithm, also called the Gibbs cloner fast and accurate. We believe that it is the fastest and the most accurate randomized algorithm for counting known so far.
In addition it is well suited for solving problems associated with the Boltzmann distribution, like estimating the partition
functions in an Ising model. We also present a combined version of the cloning and cross-entropy (CE) algorithms. We prove
the polynomial complexity of a particular version of the Gibbs cloner for counting. We finally present efficient numerical
results with the Gibbs cloner and the combined version, while solving quite general integer and combinatorial optimization
problems as well as counting ones, like SAT. 相似文献
22.
We analyze in this work the energy transfer process of accelerated charges, the mass fluctuations accompanying this process, and their inertial properties. Based on a previous work, we use here the dipole antenna, which is a very convenient framework for such analysis, for analyzing those characteristics. We show that the radiation process can be viewed by two energy transfer processes: one from the energy source to the charges and the second from the charges into the surrounding space. Those processes, not being in phase, result in mass fluctuations. The same principle is true during absorption. We show that in a transient period between absorption and radiation the dipole antenna gains mass according to the amount of absorbed energy and loses this mass as radiated energy. We rigorously prove that the gain of mass, resulting from electrical interaction has inertial properties in the sense of Newton's third low. We arrive to this result by modeling the reacting spacetime region by an electric dipole. 相似文献
23.
The sorting buffers problem is motivated by many applications in manufacturing processes and computer science, among them car-painting and file servers architecture. The input is a sequence of items of various types. All the items must be processed, one by one, by a service station. We are given a random-access sorting buffer with a limited capacity. Whenever a new item arrives it may be moved directly to the service station or stored in the buffer. Also, at any time items can be removed from the buffer and assigned to the service station. Our goal is to give the service station a sequence of items with minimum type transitions. We generalize the problem to allow items with different sizes and type transitions with different costs. We give a polynomial-time 9-approximation algorithm for the maximization variant of this problem, which improves the best previously known 20-approximation algorithm. 相似文献
24.
Scale-free networks are ultrasmall 总被引:1,自引:0,他引:1
We study the diameter, or the mean distance between sites, in a scale-free network, having N sites and degree distribution p(k) proportional, variant k(-lambda), i.e., the probability of having k links outgoing from a site. In contrast to the diameter of regular random networks or small-world networks, which is known to be d approximately ln(N, we show, using analytical arguments, that scale-free networks with 23, d approximately ln(N. We also show that, for any lambda>2, one can construct a deterministic scale-free network with d approximately ln(ln(N, which is the lowest possible diameter. 相似文献
25.
Mordechai Deutsch Reuven Tirosh Menachem Kaufman Naomi Zurgil Arye Weinreb 《Journal of fluorescence》2002,12(1):25-44
The use of fluorescence polarization as a functional parameter in monitoring cellular activation calls for the reliable and accurate measurement of the fluorescence intensity and polarization (FI and FP) of microscopic objects. The relevant experimental parameters that enter such measurements are thoroughly discussed. The possibility of executing FP measurements properly by flow-through systems is compared with that of static cytometry. Remarks on the effects of high-power excitation on markers and cells conclude the paper. 相似文献
26.
Computer calculations of an energy transfer dye laser (ETDL) performance are presented. It is shown that the ETDL output can be manipulated by varying the donor or acceptor concentrations. Experiments done on the anthracene-perylene ETDL are in agreement with the predictions of the present calculation. 相似文献
27.
28.
Darkeyah Reuven Dwaipayan Sil Biswajit Sannigrahi Xiao-Qian Wang Barbara Baird Ishrat M. Khan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):330-338
A series of 2,4-dinitrophenyl (DNP) functionalized polypyrrole terpolymers, capable of specific binding to IgE antibodies (proteins), have been synthesized using oxidizing initiator, ammonium persulfate and were characterized by 1H-NMR, IR, DSC, Light Scattering etc. The terpolymers were composed of monomers and macromonomers: monomer (pyrrole), macromonomer A (pyrrole with pendant ethylene glycol) and macromonomer B (pyrrole with pendant DNP) with specific functionality of conductance, processiblity and binding, respectively. The terpolymers are found to be semiconductive, (5 × 10?6 S cm?1) by itself without the addition of doping agents. Molecular dynamics simulation of terpolymer shows that the DNP-(2,4-dinitrophenyl) functional group extends out from the polymer backbone and thus, is available for binding. The DNP functional groups on the terpolymer achieve steady state binding with anti-DNP IgE proteins at nanomolar concentrations in solution. The terpolymer was blended with sulfonated polystyrene and processed in fibers which exhibited effective specific binding to fluorescently tagged IgE proteins and therefore, possessed the potential to be an active component in biosensor. 相似文献
29.
Lee A Andrade GF Ahmed A Souza ML Coombs N Tumarkin E Liu K Gordon R Brolo AG Kumacheva E 《Journal of the American Chemical Society》2011,133(19):7563-7570
Further progress in the applications of self-assembled nanostructures critically depends on developing a fundamental understanding of the relation between the properties of nanoparticle ensembles and their time-dependent structural characteristics. Following dynamic generation of hot-spots in the self-assembled chains of gold nanorods, we established a direct correlation between ensemble-averaged surface-enhanced Raman scattering and extinction properties of the chains. Experimental results were supported with comprehensive finite-difference time-domain simulations. The established relationship between the structure of nanorod ensembles and their optical properties provides the basis for creating dynamic, solution-based, plasmonic platforms that can be utilized in applications ranging from sensing to nanoelectronics. 相似文献
30.
The analysis of the EM radiation from a single charge shows that the radiated power depends on the retarded acceleration of
the charge. Therefore for consistency, an accelerated charge, free from the influence of external forces, should gradually
lose its acceleration, until its total energy is radiated. Calculations show that the self force of a charge, which compensates
for its radiation, is proportional to the derivative of the acceleration. However, when using this self force in the equation
of motion of the charge, one gets a diverging solution, for which the acceleration runs away to infinity. This means that
there is an inconsistency in the solution of the single charge problem. However, in the construction of the conserved Maxwell
charge density, there is implicitly an integral over the corresponding world line which corresponds to a collection of charged
spacetime events. One may therefore consistently think of the “self force” as the force on a charge due to another charge
at the retarded position. From this point of view, the energy is evidently conserved and the radiation process appears as
an absorbing resistance to the feeding source. The purpose of this work is to learn about the behavior of single charges from
the behavior of a real current, corresponding to the set of charges moving on a world line, and to study the analog of the
self force of a charge associated with the radiation resistance of a continuum of charges. 相似文献