全文获取类型
收费全文 | 247187篇 |
免费 | 2164篇 |
国内免费 | 881篇 |
专业分类
化学 | 111667篇 |
晶体学 | 3578篇 |
力学 | 13797篇 |
综合类 | 3篇 |
数学 | 51130篇 |
物理学 | 70057篇 |
出版年
2020年 | 1414篇 |
2019年 | 1585篇 |
2018年 | 12208篇 |
2017年 | 12095篇 |
2016年 | 9131篇 |
2015年 | 2748篇 |
2014年 | 3443篇 |
2013年 | 8053篇 |
2012年 | 9428篇 |
2011年 | 17097篇 |
2010年 | 10506篇 |
2009年 | 10904篇 |
2008年 | 12994篇 |
2007年 | 14994篇 |
2006年 | 6328篇 |
2005年 | 6770篇 |
2004年 | 6595篇 |
2003年 | 6532篇 |
2002年 | 5446篇 |
2001年 | 5443篇 |
2000年 | 4141篇 |
1999年 | 3107篇 |
1998年 | 2668篇 |
1997年 | 2525篇 |
1996年 | 2433篇 |
1995年 | 2233篇 |
1994年 | 2173篇 |
1993年 | 2101篇 |
1992年 | 2359篇 |
1991年 | 2316篇 |
1990年 | 2248篇 |
1989年 | 2182篇 |
1988年 | 2181篇 |
1987年 | 2182篇 |
1986年 | 2081篇 |
1985年 | 2691篇 |
1984年 | 2731篇 |
1983年 | 2424篇 |
1982年 | 2538篇 |
1981年 | 2301篇 |
1980年 | 2294篇 |
1979年 | 2446篇 |
1978年 | 2469篇 |
1977年 | 2401篇 |
1976年 | 2442篇 |
1975年 | 2363篇 |
1974年 | 2324篇 |
1973年 | 2509篇 |
1972年 | 1621篇 |
1971年 | 1330篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
951.
952.
953.
We study the evolution of radiating and viscous fluid spheres assuming an additional homothetic symmetry on the spherically symmetric space-time. We match a very simple solution to the symmetry equations with the exterior one (Vaidya). We then obtain a system of two ordinary differential equations which rule the dynamics, and find a self-similar collapse which is shear-free and with a barotropic equation of state. Considering a huge set of initial self-similar dynamics states, we work out a model with an acceptable physical behavior. 相似文献
954.
In the case of number fields the embedding problem of a p-extension with non-Abelian kernel of order p4 is studied. The two kernels of order 34 with generators α, γ and relations α9 = 1, [α,α]3=1,[α,αγγ]==1,[αγγ]=α3,γ3=1 or γ3=α3 and the kernel of order 24 with generators α, β, γ and relations α4=1 β2,[αγ]=1, [α,γ]=1,[βγ]=α2 are considered. For kernels of odd order the embedding problem is always solvable. For the kernel of order 16 the solvability
conditions are reduced to those for the associated problems at the Archimedean points, and to the compatibility condition.
Bibliography: 9 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 227, 1995, pp. 74–82. 相似文献
955.
W. B. Krätzig 《Archive of Applied Mechanics (Ingenieur Archiv)》1993,64(1):1-19
Übersicht Konsistente Schalentheorien lassen sich in einer besonders anschaulichen Weise durch lineare Approximation der Erhaltungssätze eines als Multi-Direktor-Körper beschriebenen, dreidimensionalen Kontinuums herleiten. Im vorliegenden Beitrag entstchen auf diesem Wege bestmögliche, in Geschwindigkeiten formulierte innere Schalengleichungen für beliebig große Deformationen und willkürliche, in eine Leistungsaussage einpaßbare Materialgesetze. Dabei finden Schub- und Querdeformationen Berücksichtigung. Der optimale Charakter der Schalentheorie mit gleichen Unschärfen in allen Einzelbeziehungen wird durch den Herleitungsgang sichergestellt und durch Einschrankungen mittels lokaler Tensornormen bewiesen.
Best interior shell equations including transverse shear deformations and thickness changes
Summary Consistent shell theories can be derived in a particular correct manner by linear approximation of conservation laws of a three-dimensional continuum, described as a multi-director-body. In the present paper best interior shell equations-formulated in velocities—are developed, valid for arbitrarily large deformations and rather optional material laws, incorporating shear distorsions and thickness changes. The optimal character of the theory is guaranteed by the derivation process and proven by bounding techniques using tensor norms.相似文献
956.
Summary Assuming a completely disordered lattice it is shown that all the states are localized when the disorder parameterx=a
0/0 reachesthe value 0.31, wherea is the mean atomic separation anda
0 is the Bohr radius. 相似文献
957.
958.
It is shown how, with the help of approximate integral manifolds, to solve the reduction problem in stability theory in the nonsingular critical case. A generalization of the first fundamental Lyapunov-Malkin theorem in critical cases is obtained.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 10, pp. 1324–1329, October, 1991. 相似文献
959.
W. Królas A. Maj P. Bednarczyk B. Fornal W. Mceczynski J. Styczeń M. Zicebliński 《Zeitschrift für Physik A Hadrons and Nuclei》1992,344(2):145-147
High-energy gamma-rays emitted in the decay of the giant dipole resonance built on excited states of55Mn nucleus were measured with a bismuth germanate detector. Resonance parameters were extracted from the fits to the experimental spectra. Two new high-energy calibration points originating from slow-neutron capture in germanium isotopes of bismuth germanate crystal are proposed for large-volume BGO detectors. 相似文献
960.
There are essentially two schools of thought regarding the function of decision support systems. One is that the main purpose is to support the decision-maker in whatever style of decision-making he or she wishes. The other is that the support, while suiting the decision-maker's individual style, must also be based on an appropriate theoretical paradigm. The work with students of decision support systems reported here suggests that the latter, normative, view is not one which comes naturally to many of the students, even when working on an example where it seemed relatively easy to incorporate. Other conclusions are also presented, relating to the choice of software for decision support system development, the process of teaching about decision support systems, and group formation. 相似文献