全文获取类型
收费全文 | 716篇 |
免费 | 23篇 |
国内免费 | 13篇 |
专业分类
化学 | 257篇 |
晶体学 | 3篇 |
力学 | 8篇 |
数学 | 148篇 |
物理学 | 336篇 |
出版年
2020年 | 12篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 17篇 |
2014年 | 12篇 |
2013年 | 37篇 |
2012年 | 20篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 13篇 |
2008年 | 29篇 |
2007年 | 26篇 |
2006年 | 24篇 |
2005年 | 14篇 |
2004年 | 25篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 25篇 |
1999年 | 10篇 |
1997年 | 11篇 |
1996年 | 7篇 |
1995年 | 13篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 15篇 |
1991年 | 18篇 |
1990年 | 23篇 |
1989年 | 8篇 |
1988年 | 13篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 11篇 |
1981年 | 10篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 15篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 15篇 |
1974年 | 16篇 |
1973年 | 12篇 |
1971年 | 6篇 |
1970年 | 6篇 |
1964年 | 4篇 |
排序方式: 共有752条查询结果,搜索用时 15 毫秒
101.
Adjoint‐based and feature‐based grid adaptive strategies are compared for their robustness and effectiveness in improving the accuracy of functional outputs such as lift and drag coefficients. The output‐based adjoint approach strives to improve the adjoint error estimates that relate the local residual errors to the global error in an output function via adjoint variables as weight functions. A conservative adaptive indicator that takes into account the residual errors in both the primal (flow) and dual (adjoint) solutions is implemented for the adjoint approach. The physics‐based feature approach strives to identify and resolve significant features of the flow to improve functional accuracy. Adaptive indicators that represent expansions and compressions in the flow direction and gradients normal to the flow direction are implemented for the feature approach. The adaptive approaches are compared for functional outputs of three‐dimensional arbitrary Mach number flow simulations on mixed‐element unstructured meshes. Grid adaptation is performed with h‐refinement and results are presented for inviscid, laminar and turbulent flows. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
102.
D.M. Newman M.L. Wears R. Atkinson D. McHugh 《Applied physics. B, Lasers and optics》2002,74(7-8):715-718
The concept of using comparison between magneto-optic measurements taken in the linear and second-harmonic reflected fields
to address problems attending the development of ultra-high-density recording media as the limits of thermal stability are
approached is presented. It is shown how magneto-optical measurements made routinely in the linear reflected field to access
many of the bulk characteristics of such media may, by operating in the second-harmonic field, be fruitfully extended. To
illustrate the techniques being explored, reference is made to initial measurements on a longitudinal recording medium under
continuing development at Coventry. This medium, already shown to support recording at linear densities in excess of 100 kfci,
is based on cobalt particles around 10 nm in diameter.
Received: 16 October 2001 / Revised version: 14 March 2002 / Published online: 29 May 2002 相似文献
103.
A simulation technique is used to study the properties of the “hole modulated hopping” model introduced by Hirsch. The superconducting order parameter, energy gap and pair size have been determined for a range of particle densities and temperatures in the neighbourhood of the superconducting phase transition. Results are consistent with the interpretation of the superconducting transition to be Bose-like at low hole densities and BCS-like at high hole densities, with a crossover near the Tc maximum in the Tc versus hole density curve. This behaviour is related to the existence of small non-overlapping pairs at low hole densities and large strongly interpenetrating pairs at hole densities above the Tc maximum. 相似文献
104.
P.R. Newman M.D. Ewbank C.D. Mauthe M.R. Winkle W.D. Smolyncki 《Solid State Communications》1981,40(11):975-978
Observations of anisotropic transport in (CH)x reported to date have been made on stretch-oriented films in the plane of the film. We report the first observations of anisotropy in the thermal conductivity measured parallel and perpendicular to the plane of unstretched films. The room-temperature value measured along the film is , and is almost a factor of 20 higher than that observed perpendicular to the film . Finally, the temperature dependences for the parallel and perpendicular thermal conductivities are reported. 相似文献
105.
A.L.S. Angelis H.-J. Besch B.J. Blumenfeld L. Camilleri T.J. Chapin R.L. Cool C. del Papa L. Di Lella Z. Dimčovski R.J. Hollebeek L.M. Lederman D.A. Levinthal J.T. Linnemann C.B. Newman N. Phinney B.G. Pope S.H. Pordes K.K. Young 《Nuclear Physics B》1982,209(2):284-300
We present data on proton-proton collisions, obtained at the CERN Intersecting Storage Rings, in which two roughly back-to-back π0's of high transverse momentum (pT) were produced. The angular distribution of the dipion axis relative to the collision axis is found to be independent of both the effective mass m of the dipion system and the centre-of-mass energy √s of the proton-proton collision. The cross-sections at the values of √s satisfy a scaling law of the form . We show from our data that the leading π0 carries most of the momentum of the scattered parton. Given this fact, the axis of the dipion system follows closely the direction of the scattered constituents, and we exploit this to determine the angular dependence of the hard-scattering subprocess. We also compare our data with the lowest order QCD predictions using structure functions as determined in deep-inelastic scattering and fragmentation functions from electron-positron annihilation. 相似文献
106.
A.L.S. Angelis G. Basini H.-J. Besch R. Breedon L. Camilleri T.J. Chapin R.L. Cool P.T. Cox C. von Gagern C. Grosso-Pilcher D. Hanna J.T. Linnemann C.B. Newman R.B. Nickerson N. Phinney S.H. Pordes K. Powell J.M. Yelton 《Physics letters. [Part B]》1982,116(5):379-382
The invariant cross sections for π0 meson production in alpha—alpha and alpha—proton collisions at the ISR were meas- ured up to transverse momenta of and , respectively. These measurements are compared with π0 production in pp collisions at the same values of nucleon, and the variation of the nuclear A-dependence with pT is determined. 相似文献
107.
A. Helfer M. S. Hickman C. Kozameh C. Lucey E. T. Newman 《General Relativity and Gravitation》1988,20(9):875-880
The general solution to the strong coupling limit of the vacuum Einstein field equations is obtained. This limit is related to the theory of symmetric spaces.On leave from the Department of Mathematics, Monash University, Clayton, Victoria, 3168, Australia.On leave from F.A.M.A.F., Laprida 854, University of Cordoba, 5000 Cordoba, Argentina.On leave from the Physics Department, Jamestown Community College, Jamestown, N.Y. 14701. 相似文献
108.
Silicon-29 and carbon-13 n.m.r. studies of organosilicon chemistry. VII—trimethylsilylated silicates
Silicon-29 n.m.r. was used to study the products from trimethylsilylation of minerals. Chemical shifts are reported for four model compounds, viz. the monomer, dimer, linear trimer (from natrolite) and cyclic tetramer (from laumontite). Information is then obtained from the products of trimethylsilylation of the anhydrous calcium silicates wollastonite and pseudo-wollastonite. In the latter case it is shown that the principal products are the four model compounds, and percentage yields are obtained for these. 相似文献
109.
The thermal conductivity of tellurium dioxide is reported as a function of temperature. At 77K, the thermal conductivity is 0.09 W/cm-K and it decreases approximately as the inverse of the temperature to a value of 0.02 W/cm-K at 300K. The anisotropy between the a- and c-axes is less than 20% over the entire experimental temperature range, with the a-axis more conductive than the c-axis. By making some simplifying assumptions, the phonon mean free paths and relaxation times are deduced. 相似文献
110.