全文获取类型
收费全文 | 203845篇 |
免费 | 2301篇 |
国内免费 | 506篇 |
专业分类
化学 | 111781篇 |
晶体学 | 3656篇 |
力学 | 8033篇 |
综合类 | 11篇 |
数学 | 19338篇 |
物理学 | 63833篇 |
出版年
2020年 | 1772篇 |
2019年 | 1976篇 |
2018年 | 2295篇 |
2017年 | 2409篇 |
2016年 | 3589篇 |
2015年 | 2234篇 |
2014年 | 3633篇 |
2013年 | 9209篇 |
2012年 | 6633篇 |
2011年 | 8139篇 |
2010年 | 5781篇 |
2009年 | 5741篇 |
2008年 | 7268篇 |
2007年 | 7163篇 |
2006年 | 6760篇 |
2005年 | 6111篇 |
2004年 | 5571篇 |
2003年 | 5130篇 |
2002年 | 4908篇 |
2001年 | 6156篇 |
2000年 | 4636篇 |
1999年 | 3528篇 |
1998年 | 2750篇 |
1997年 | 2710篇 |
1996年 | 2606篇 |
1995年 | 2454篇 |
1994年 | 2350篇 |
1993年 | 2193篇 |
1992年 | 2846篇 |
1991年 | 2743篇 |
1990年 | 2688篇 |
1989年 | 2706篇 |
1988年 | 2725篇 |
1987年 | 2736篇 |
1986年 | 2609篇 |
1985年 | 3321篇 |
1984年 | 3325篇 |
1983年 | 2606篇 |
1982年 | 2719篇 |
1981年 | 2775篇 |
1980年 | 2545篇 |
1979年 | 2889篇 |
1978年 | 2866篇 |
1977年 | 2986篇 |
1976年 | 2820篇 |
1975年 | 2557篇 |
1974年 | 2514篇 |
1973年 | 2471篇 |
1972年 | 1705篇 |
1968年 | 1704篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
981.
K. M. Kojima 《Applied magnetic resonance》1997,13(1-2):111-122
Muon spin relaxation (μSR) and nuclear magnetic resonance (NMR) are powerful probes of magnetism, which have been extensively applied to studies of spin gap systems. Comparison of results obtained with the two techniques gives complementary results, as each is sensitive to different aspects of spin gap magnetism. We discuss recent μSR measurements of the spin ladder compounds Sr n?1Cu n+1O2n , pure and doped Haldane materials (Y2?x Ca x )Ba(Ni1?y Mg y )O5, and doped spin Peierls compounds (Cu1?x Zn x )(Ge1?y Si y )O3. 相似文献
982.
983.
Joachim Käschel 《Proceedings Mathematical Sciences》1992,102(2):155-158
In Venkaiah [1] an algorithm for solving linear optimization problems based on the idea of the projective algorithm of Karmarkar,
is proposed. The essential simplification in the new algorithm is the use of a fixed projection operator. In this way the
algorithm requires onlyO(n
2
) operations to obtain a sufficient exact solution. In this note it is shown that in some special cases the algorithm of Venkaiah
yields a feasible solution that is far from the optimal one. 相似文献
984.
985.
The processing of oil sands materials and upgrading of bitumens present a variety of problems for conventional technologies. This article describes a preliminary study of the concept of using microwave induced catalytic techniques to decompose the complex and viscous hydrocarbon compounds contained in these materials to allow efficient extraction of volatile and economically useful organic products such as C2 and C3 hydrocarbons. Addition of water to the tar sand material prior to reaction facilitated separation from the sand component as well as promoting the formation of economically very useful, liquid, oxygenated hydrocarbon products. 相似文献
986.
987.
K. Prokeš 《Czechoslovak Journal of Physics》2002,52(2):253-258
Many materials exhibit various magnetic phenomena as a function of magnetic field, temperature and/or pressure. Usually, bulk magnetic measurements provide first information on the magnetic state of the material by measuring their response on the applied magnetic field. However, it is necessary to investigate materials also on a microscopic scale. This is often done by means of neutron scattering. In this contribution we discuss basic ideas of this method and we report on few experimental results obtained with a split-pair coil 14.5 T superconducting magnet which can be combined with dilution stick offering temperatures as low as 30 mK and/or with a small clamped-type pressure cell which offers pressure up to 1.0 GPa. 相似文献
988.
Y. Masuda K. Asahi J. Kura Y. Mori H. Sato H. M. Shimizu 《Hyperfine Interactions》1992,74(1-4):149-157
An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is
discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering
amplitudes. The nuclear polarizations of proton,3He and139La are discussed for the T-violation experiment. 相似文献
989.
A two-dimensional self consistent model of the Beam-Plasma-Discharge (BPD) has been developed to calculate the discharge ignition of a bandlike electron beam in a discharge chamber. The discharge was considered in Argon with an initial concentration of 1014 cm?3. The model allows calculation of the time evolution of perpendicular profiles of electron density, temperature and the potential. 相似文献
990.
Prof. Dr. K. Ikegami Prof. Dr. T. Sugibayashi Mr. K. Matsuo 《Archive of Applied Mechanics (Ingenieur Archiv)》1994,65(1):44-53
Summary A method of joining two metal cylindrical shafts with adhesive coupling is proposed. Two cylindrical shafts with the same diameter are connected by bonding through a cylindrical coupling with epoxy resin. The strength of the shaft joint under tensile loading and torsional loading is investigated analytically and experimentally. The stress and strain distributions of the shaft joint is analyzed by the finite element method. The analyzed strain distributions in the joint are compared with experimental values. The joint strength is predicted by applying the strength laws of shafts, coupling, adhesive layer and adhesive interface between shaft and adhesive coupling. The effects of the coupling dimension on the joint strength are examined. It is shown that the adhesive shaft joint can transfer the load by which the cylindrical shafts are plastically deformed.This paper was refined by the author, K. Ikegami, during statying at Technische Universität München under the support of Deutscher Akademischer Austauschdients. The author is grateful to Professor Lippmann of Technische Universität München who is the host professor of the support. 相似文献