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991.
The topology of many modifications of elemental gallium is reflected in the large variety of metalloid Ga clusters that have been isolated as intermediates on the way from the metastable molecular GaX species (X=Cl, Br, I) by means of disproportionation to the bulk metal. Herein, we report the synthesis and characterization of the first metalloid cluster anion [Ga(18)(PtBu(2))(10)](3-) with the singular core topology that resembles the gallium high-pressure modification Ga-II. The stabilization of the cluster anion through ion-pair contacts with a chainlike "Li(4)Br(2) backbone" is discussed. Furthermore, the compound is discussed in context of the other metalloid clusters Ga(18)R(8) and Ga(22)R(8) (R=SitBu(3)) and their structural relation to the elemental modifications Ga-III and beta-Ga, respectively. 相似文献
992.
Akerib DS Attisha MJ Bailey CN Baudis L Bauer DA Brink PL Brusov PP Bunker R Cabrera B Caldwell DO Chang CL Cooley J Crisler MB Cushman P Daal M Dixon R Dragowsky MR Driscoll DD Duong L Ferril R Filippini J Gaitskell RJ Golwala SR Grant DR Hennings-Yeomans R Holmgren D Huber ME Kamat S Leclercq S Lu A Mahapatra R Mandic V Meunier P Mirabolfathi N Nelson H Nelson R Ogburn RW Perera TA Pyle M Ramberg E Rau W Reisetter A Ross RR Sadoulet B Sander J Savage C Schnee RW Seitz DN Serfass B 《Physical review letters》2006,96(1):011302
We report new results from the Cryogenic Dark Matter Search (CDMS II) at the Soudan Underground Laboratory. Two towers, each consisting of six detectors, were operated for 74.5 live days, giving spectrum-weighted exposures of 34 (12) kg d for the Ge (Si) targets after cuts, averaged over recoil energies 10-100 keV for a weakly interacting massive particle (WIMP) mass of 60 GeV/c2. A blind analysis was conducted, incorporating improved techniques for rejecting surface events. No WIMP signal exceeding expected backgrounds was observed. When combined with our previous results from Soudan, the 90% C.L. upper limit on the spin-independent WIMP-nucleon cross section is 1.6 x 10(-43) cm2 from Ge and 3 x 10(-42) cm2 from Si, for a WIMP mass of 60 GeV/c2. The combined limit from Ge (Si) is a factor of 2.5 (10) lower than our previous results and constrains predictions of supersymmetric models. 相似文献
993.
For annuity providers, longevity risk, i.e. the risk that future mortality trends differ from those anticipated, constitutes an important risk factor. In order to manage this risk, new financial products, so-called longevity derivatives, may be needed, even though a first attempt to issue a longevity bond in 2004 was not successful.While different methods of how to price such securities have been proposed in recent literature, no consensus has been reached. This paper reviews, compares and comments on these different approaches. In particular, we use data from the United Kingdom to derive prices for the proposed first longevity bond and an alternative security design based on the different methods. 相似文献
994.
Grid technologies and the related concepts of utility computing and cloud computing enable the dynamic sourcing of computer resources and services, thus allowing enterprises to cut down on hardware and software expenses and to focus on key competencies and processes. Resources are shared across administrative boundaries, e.g. between enterprises and/or business units. In this dynamic and inter-organizational setting, scheduling and pricing become key challenges. Market mechanisms show promise for enhancing resource allocation and pricing in grids. Current mechanisms, however, are not adequately able to handle large-scale settings with strategic users and providers who try to benefit from manipulating the mechanism. In this paper, a market-based heuristic for clearing large-scale grid settings is developed. The proposed heuristic and pricing schemes find an interesting match between scalability and strategic behavior. 相似文献
995.
A Novel Penning‐Trap Design for the High‐Precision Measurement of the 3He2 + Nuclear Magnetic Moment
Antonia Schneider Andreas Mooser Alexander Rischka Klaus Blaum Stefan Ulmer Jochen Walz 《Annalen der Physik》2019,531(5)
A new experiment is constructed aiming at the first direct high‐precision measurement of the helium‐3 nuclear magnetic moment with a relative precision of parts‐per‐billion or better. Methods similar to those used in proton and antiproton magnetic moment measurements are applied. As those techniques rely on the challenging detection of single spin‐flips, a novel Penning trap design optimized for nuclear spin‐flip detection is developed. 相似文献
996.
997.
The discovery of new or improved catalysts is often an arduous task. In several instances, empirical studies and single reactor experiments have given way to design of experiments methods and high throughput experimentation (HTE) to speed up the process. However, even with increased throughput, only small subsets of the large multivariate parameter spaces often associated with catalyst and process characteristics can be sampled. An approach termed rational design gives the opportunity to target regions of the parameter space by combining the knowledge gained from surface science experiments and modeling to efficiently guide HTE. The prediction and validation of bimetallic catalysts for ethylene epoxidation illustrates this approach. Conversely, HTE can also be used to lead the discovery cycle in reverse, identifying surface science and modeling opportunities for further development. As an example of this cycle, the use of HTE to identify model catalyst designs for the study of promoted NSR catalysts is considered. 相似文献
998.
Uwe Rau Kurt Taretto Susanne Siebentritt 《Applied Physics A: Materials Science & Processing》2009,96(1):221-234
The paper reviews the current status of the research on grain boundaries in polycrystalline Cu(In, Ga)(S, Se)2 alloys used as absorber materials for thin-film solar cells. We discuss the different concepts that are available to explain
the relatively low electronic activity of grain boundaries in these materials. Numerical simulations that have been undergone
so far to model the polycrystalline solar cells are briefly summarized. In addition, we give an overview on the experiments
that have been conducted so far to elucidate the structural, defect-chemical, and electronic properties of grain boundaries
in Cu(In, Ga)(S, Se)2 thin-films. 相似文献
999.
Enrico?Da?Como Esther?Scheler Peter?Strohriegl John?M.?Lupton Jochen?Feldmann 《Applied Physics A: Materials Science & Processing》2009,95(1):61-66
Polyfluorene represents a unique model to study the influence of intramolecular conformation on the electronic properties
of chromophores with an extended π-conjugation. According to the degree of planarity between the adjacent repeat units the electronic and optical properties
can change substantially. This peculiar spectroscopic behavior has been described by identifying different phases, namely
the glassy, the γ- and the β-phase. Here, we present low-temperature single-molecule spectroscopy of a series of oligofluorenes differing in the number
of monomeric units, in order to gain information on the influence of chain length on the polymorphism. By monitoring the energy
of the 0-0 transition we have classified single molecules belonging to the different phases. We demonstrate that a large number
of molecules start to form the β-phase only when more than 9 repeat units constitute the molecular chain. The implications for the control of morphology in
polyfluorene thin films are discussed. 相似文献
1000.
Jochen Ströhle 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(9):1622-1640
The objective of the present study is to evaluate variations of the re-ordered wide band model for non-grey radiative transfer calculations in 3D enclosures using the discrete ordinates method. First, the performance of various angular and spatial discretisation schemes of the discrete ordinates method is investigated. Then, several formulations, averaging procedures, and scaling methods of the re-ordered wide band model are tested, and the results are validated against those of a statistical narrow band model. The grey gases formulation using three optimised absorption coefficient is found to be the most efficient method. 相似文献