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排序方式: 共有235条查询结果,搜索用时 391 毫秒
51.
H. Zimmermann E. Richter C. Reichle I. Westphal P. Geggier U. Rehn S. Rogaschewski W. Bleiss G.R. Fuhr 《Applied Physics A: Materials Science & Processing》2001,73(1):11-26
During locomotion, adherently growing cells release highly ordered structures consisting of filaments and patches often dendritically
organised. Such traces can be re-incorporated by the donor cell or disconnected and lost. Here, we present the results of
a three-year research programme into trace formation and structural organisation including the influence of substrate surface
properties. Some phenomena may, ultimately, have medical or technological applications. These include: (i) the deposition
and re-incorporation of cellular material as cells move forward and backward; (ii) the ability of cells to differentiate between
their own and foreign traces; (iii) the presence of receptors in the intact membrane envelope of filaments and patches; and
(iv) the cytoplasmic content of patches. Trace formation is physiologically controlled and a characteristic of many types
of actively migrating higher animal and human cells. Possible applications and perspectives are discussed and the importance
of cell-trace elements as “bionanotubes” and biological submicron compartments of cells is explained.
Received: 5 February 2001 / Accepted: 6 February 2001 / Published online: 23 May 2001 相似文献
52.
We report theoretical results for dynamical and thermodynamic properties of the bare graphite (0001) surface, and with a physisorbed monolayer of xenon. The surface vibrations of graphite are less pronounced than those in more isotropic crystals. The surface-excess specific heat of the bare surface peaks at 45 K, that of the xenon at 13.5 K. 相似文献
53.
54.
The displacement of the peak of a wavepacket that crosses an empty Fabry-Perot cavity is measured by using photon pairs generated by parametric down conversion, a Hong-Ou-Mandel (HOM) interferometer and coincidence detection. The Fabry-Perot cavity distorts the photon wavepacket. The HOM interferometer is a good tool to map this distortion. We discuss the corrections which must be made in the two-photon inteference results, in order to achieve the true data researched. Even in the absence of active absorbers media or media with inverted atomic populations, superluminal-like effects connected with the tunnelling phenomena are observed. An interpretation of the experimental results in the causality frame is given. 相似文献
55.
切贝舍夫是俄国十九世纪最伟大的数学家之一,他第一个主张概率论的极限定理应该严格的证明,并尽可能精确地确定偏离极限的估计量,这在方法论上引起了很大变化.其创立的切贝舍夫不等式和切贝舍夫大数定律是概率论极限理论的基础,从而使概率论成为严密数学分支.切贝舍夫的概率思想是在一定数学文化背景产生的,尤其是法国数学文化对其发展的形成有着深刻影响. 相似文献
56.
Lee Siew Ling 《Journal of Non》2008,354(33):3939-3943
Sulfated silica-titania aerogel (SO4/ST) catalyst was prepared by direct synthesis and modified with H2SO4 by wet impregnation method. Brønsted acid sites were generated after sulfation of the silica-titania aerogel with a pKa of −14.52. Consecutive transformation of 1-octene, catalyzed by sulfated silica-titania aerogel using aqueous hydrogen peroxide as oxidant shows high activity towards 1,2-octanediol through the formation of 1,2-epoxyoctane. The formation of 1,2-octanediol is enabled by the co-existence of sulfated Ti species with Brønsted acid sites in the SO4/ST system. Sulfated silica-titania aerogel catalyst produced 1,2-octanediol (326 μmol) with selectivity of 63%. In contrast, no diol was produced when silica-titania aerogel was used. 相似文献
57.
We use phenomenological nonlocal Lagrangians, which lead to nontrivial forms for the quark propagator, to describe the pion.
We define a procedure based on previous studies on nonlocal Lagrangians for the calculation of the pion parton distributions
at low Q2. The obtained parton distributions fulfill all the wishful properties. Using a convolution approach we incorporate the composite
character of the constituent quarks. We evolve, using the Renormalization Group, the calculated parton distributions to the
experimental scale and compare favorably with the data and draw conclusions. 相似文献
58.
A. Aierken J. Riikonen M. Mattila T. Hakkarainen M. Sopanen H. Lipsanen 《Applied Surface Science》2007,253(14):6232-6235
The GaAs surface passivation effects of epitaxially grown ultra-thin GaP layers and surface As-P exchange have been investigated. Optical properties of passivated and unpassivated InGaAs/GaAs near-surface quantum wells (QWs) grown by metal organic vapor phase epitaxy (MOVPE) are studied by low-temperature continuous-wave and time-resolved photoluminescence (PL). By optimizing the growth conditions, smooth surface morphologies and significant improvement of optical properties were observed for both passivation methods. Passivation improved the PL intensity more than two orders of magnitude and notably increased the PL decay time. 相似文献
59.
B. Metsch 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):275-280
The scope of a relativistically covariant constituent quark model of baryons based on the Bethe-Salpeter equation in instantaneous
approximation is illustrated by a discussion of various baryon resonance observables such as static electromagnetic moments
--including a novel calculational procedure-- form factors and helicity amplitudes, semileptonic decays as well as the systematics
of two-body strong decay widths. 相似文献
60.
Miyoung Kim Young Joon Hong Jinkyoung Yoo Gyu‐Chul Yi Gyeong‐Su Park Ki‐jeong Kong Hyunju Chang 《固体物理学:研究快报》2008,2(5):197-199
High‐resolution transmission electron microscopy was employed to investigate morphologies and catalyst‐free growth mechanism of ZnO/Mgx Zn1–x O ‘multi‐quantum well’ and ‘core‐shell’ nanorod heterostructures as well as ZnO nanorods. The one‐dimensional growth mechanism and the hexagonal faceting of ZnO nanorod were explained by the surface energy anisotropy. The morphology change by alloying with Mg was successfully explained by investigating the energy gain by adatom adsorption and the reduction in the surface energy anisotropy. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献