首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   168篇
  免费   0篇
  国内免费   1篇
化学   73篇
力学   4篇
数学   25篇
物理学   67篇
  2022年   3篇
  2021年   3篇
  2020年   1篇
  2019年   1篇
  2018年   2篇
  2017年   2篇
  2016年   8篇
  2014年   3篇
  2013年   12篇
  2012年   12篇
  2011年   11篇
  2010年   4篇
  2009年   3篇
  2008年   9篇
  2007年   9篇
  2006年   4篇
  2005年   4篇
  2004年   6篇
  2003年   3篇
  2002年   10篇
  2001年   3篇
  2000年   2篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1995年   4篇
  1994年   5篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   2篇
  1987年   1篇
  1986年   3篇
  1985年   6篇
  1984年   3篇
  1982年   4篇
  1981年   3篇
  1980年   5篇
  1979年   4篇
  1974年   2篇
  1973年   1篇
  1972年   1篇
排序方式: 共有169条查询结果,搜索用时 406 毫秒
91.
We present a new result based on an analysis of the data collected by the MEG detector at the Paul Scherrer Institut in 2009 and 2010, in search of the lepton-flavor-violating decay μ(+)e(+)γ. The likelihood analysis of the combined data sample, which corresponds to a total of 1.8×10(14) muon decays, gives a 90% C.L. upper limit of 2.4×10(-12) on the branching ratio of the μ(+)→e(+)γ decay, constituting the most stringent limit on the existence of this decay to date.  相似文献   
92.
Fine and well dispersed Pt-Cu bimetallic nanoparticles stabilized by polyvinyl pyrrolidone (PVP) were synthesized by alkaline polyol method. The molar ratio of Pt to Cu was 1 : 1. Further, the Pt-Cu bimetallic nanoparticles were supported on alumina and their catalytic behavior in methane combustion was investigated. The as-prepared as well as the supported Pt-Cu nanoparticles were characterized by transmission elec-tron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), fractal analysis and X-ray diffraction (XRD). The dependence of methane combustion on the morphology and surface composition of Pt-Cu nanoparticles was analyzed based on the experimental results.  相似文献   
93.
Let G = (V, E) be a graph and ${R\subseteq E}$ . A matching M in G is called R-feasible if the subgraph induced by the M-saturated vertices does not have an edge of R. We show that the general problem of finding a maximum size R-feasible matching in G is NP-hard and identify several natural applications of this new concept. In particular, we use R-feasible matchings to give a necessary and sufficient condition for the existence of a systems of disjoint representatives in a family of hypergraphs. This provides another Hall-type theorem for hypergraphs. We also introduce the concept of R-feasible (vertex) cover and combine it with the concept of R-feasible matching to provide a new formulation and approach to Ryser’s conjecture.  相似文献   
94.
Problem-dependent interpolation functions for displacements and rotations are obtained from the exact analytical solution of the 3D Timoshenko beam problem by introducing a full set of boundary conditions. The developed methodology allows us to derive a new solution that coincides with the classical result of the engineering beam theory. In addition, the proposed interpolation enables exact strain recovery at any point within the problem domain.  相似文献   
95.
The title compound, [PtCl(C3H7NO)2(C18H15P)]Cl·H2O or trans‐[PtCl{Z‐HN=C(Me)OMe}2(PPh3)]Cl·H2O, crystallizes from an acetone solution of isomeric trans‐[PtCl{E‐HN=C(Me)OMe}2(PPh3)]Cl. The two HN=C(Me)OMe ligands show typical π‐bond delocalization over the N—C—O group [Cini, Caputo, Intini & Natile (1995). Inorg. Chem. 34 , 1130–1137] and have the unprecedented Z–anti configuration. The relative orientation of the imino ether ligands is head‐to‐tail.  相似文献   
96.
Many-body correlations generated by the symmetry potential naturally arise in the molecular-dynamics CoMD-II model. The effect of these correlations on the collision dynamics at Fermi energies is discussed. In particular we show that two-body correlations generated by the symmetry potential are able to produce large effects in simple observables such as the charge distributions. A comparison with the predictions, based on EOS static calculations, is also discussed.  相似文献   
97.
The nature of a metal-insulator transition tuned by external gates in quantum Hall systems with point constrictions, as reported in recent experiments [S. Roddaro, Phys. Rev. Lett. 95, 156804 (2005)10.1103/PhysRevLett.95.156804], is examined. We attribute this phenomenon to a splitting of the integer edge into conducting and insulating stripes, the latter wide enough to allow for the stability of the edge structure. Interchannel impurity scattering and interchannel Coulomb interactions do not destabilize this picture.  相似文献   
98.
This work is a collection of selected, significant references focussing upon magnetic materials and their interaction with electromagnetic fields. The major topics included are ferrites, plasmas (both atmospheric and laboratory), magnetic composites, magnetic dielectric fluids, ferroelectric liquid crystals. Sections discussing general magnetic materials and phenomena are also included.  相似文献   
99.
As part of a study of large pT phenomena in photon-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is 〈γ/all〉 = 0.074 ± 0.012 for 6 GeV/c < pT 10 GeV/c, and 〈γ/all〉 = 0.26 ± 0.04 for pT > 10 GeV/c, with an additional systematic uncertainty of ±0.05 for both values.  相似文献   
100.
New Tetrathiocyanato Diamin Chromiates with Naphthylamines Substitution reactions of anhydrous K3[Cr(NCS)6] with α- and β-naphthyl- amine without applying of solvents were carried out. The formulae of the new positionisomer complex anions were established with a series of double decomposition reactions with the hydrochlorides of some heterocyclic N-bases and cobalt(III) amines. From spectroscopical investigations -UV and UR) some structural problems are resolved.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号