全文获取类型
收费全文 | 264853篇 |
免费 | 2374篇 |
国内免费 | 621篇 |
专业分类
化学 | 140575篇 |
晶体学 | 3137篇 |
力学 | 11898篇 |
综合类 | 9篇 |
数学 | 29469篇 |
物理学 | 82760篇 |
出版年
2019年 | 2289篇 |
2018年 | 3115篇 |
2017年 | 3111篇 |
2016年 | 4484篇 |
2015年 | 2658篇 |
2014年 | 4277篇 |
2013年 | 10672篇 |
2012年 | 8067篇 |
2011年 | 9894篇 |
2010年 | 7084篇 |
2009年 | 6875篇 |
2008年 | 9311篇 |
2007年 | 9510篇 |
2006年 | 8880篇 |
2005年 | 8071篇 |
2004年 | 7423篇 |
2003年 | 6733篇 |
2002年 | 6660篇 |
2001年 | 7325篇 |
2000年 | 5659篇 |
1999年 | 4359篇 |
1998年 | 3859篇 |
1997年 | 3761篇 |
1996年 | 3312篇 |
1995年 | 3238篇 |
1994年 | 3386篇 |
1993年 | 3081篇 |
1992年 | 3558篇 |
1991年 | 3568篇 |
1990年 | 3503篇 |
1989年 | 3376篇 |
1988年 | 3459篇 |
1987年 | 3395篇 |
1986年 | 3193篇 |
1985年 | 4284篇 |
1984年 | 4573篇 |
1983年 | 3801篇 |
1982年 | 3933篇 |
1981年 | 3851篇 |
1980年 | 3828篇 |
1979年 | 3807篇 |
1978年 | 4136篇 |
1977年 | 4059篇 |
1976年 | 4127篇 |
1975年 | 3796篇 |
1974年 | 3864篇 |
1973年 | 4004篇 |
1972年 | 2822篇 |
1971年 | 2349篇 |
1970年 | 2166篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
P. G. Baranov N. G. Romanov A. Hofstaetter A. Scharmann C. Schnorr F. J. Ahlers K. Pierz 《JETP Letters》1996,64(10):754-759
Two types of excitons, localized at opposite interfaces and characterized by different magnitudes of the exchange interactions
at the same radiation energies, are simultaneously in type-II GaAs/AlAs superlattices. It is shown that the additional long-wavelength
luminescence line in superlattices grown with growth interruptions after the GaAs layers is due to the recombination of an
exciton localized at an inverted interface in regions where the quantum-well width is increased by one monolayer.
Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 701–706 (25 November 1996) 相似文献
992.
993.
C. B?uerle Yu M. Bunkov S. N. Fisher H. Godfrin G. R. Pickett 《Czechoslovak Journal of Physics》1996,46(Z1):5-6
During studies of the impact of single neutrons on superfluid3He at around 100μK we have measured the thermal energy released in the superfluid following the nuclear reaction, n+3He→p+3H+764keV. However, we find that the measured energy deposited in the quasiparticle system shortly after this reaction is substantially
less than what we expect. We believe that this energy deficit represents that energy which has gone into the creation of vortices,
in analogy to the creation of cosmic strings in the early universe via the Kibble mechanism. Furthermore, from the magnitude
of the deficit, we can infer the vortex density which compares favorably with that predicted in Zurek’s scenairo. 相似文献
994.
S. E. Kubatkin A. Ya. Tzalenchuk Z. G. Ivanov P. Delsing R. I. Shekhter T. Claeson 《JETP Letters》1996,63(2):126-132
We report on a successful attempt to fabricate a Coulomb blockade electrometer consisting of an ultrasmall YBa2Cu3O7−δ (YBCO) island coupled to two gold electrodes through a high-resistance native surface tunnel barrier. A third electrode placed
near the island was used as an electrostatic gate. Spectra typical for tunneling into the YBCO superconductor were reproducibly
measured. At temperatures below 0.5 K the low-bias conductance was suppressed by the Coulomb blockade. The blockade could
be periodically varied by the gate potential. An external magnetic field of up to 5 T strongly influenced the transport via
the island but without any change in the period of the Coulomb oscillations.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 112–117 (25 January 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
995.
Yu. G. Teterin 《Journal of Mathematical Sciences》1997,83(5):664-672
It is proved that the group of spinor norms of autometries of a generalized quadratic lattice ℒ over the ring of integral
elements v
p
of a local field k
p
, in the case wherep∤2 and ℒ is a generalized translation, is generated by the spinor norms of symmetries contained in the group of autometries
of ℒ. As a corollary, an extension to the case of generalized quadratic lattices is given for known sufficient conditions
of coincidence of the genus and the spinor genus of a quadratic lattice. Bibliography: 9 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 211, 1994, pp. 161–173.
Translated by Yu. G. Teterin. 相似文献
996.
Electric fields of the anions, cations and neutral forms of 2-aminopurine and 6-thioguanine have been mapped. Certain important
features of the maps are similar to those found earlier in the neutral and ionic forms of adenine and guanine. The computed
electric field patterns satisfactorily explain reactive sites and biological activity of the molecules. 相似文献
997.
Conclusion The proposed model of formation of the reinforcing framework in the manufacture of an axisymmetric shell by the CPW method makes it possible to numerically determine the thicknesses and rates of filling the layers, reinforcement angles as a function of the main parameters of the technological process, geometry of the mandrel, and characteristics of the reinforcing filament. It was established that the thicknesses of the layers, reinforcement rates and angles, and, as a consequence, the effective stiffness characteristics of the composite are substantially variable both along the meridian and over the thickness of the shell.Translated from Mekhanika Kompozitnykh Materialov, No. 5, pp. 609–617, September–October, 1992.The authors thank V. A. Frolov for the experimental results. 相似文献
998.
V. L. Bratman G. G. Denisov A. V. Savilov 《International Journal of Infrared and Millimeter Waves》1995,16(3):459-471
A relatively high level of the minimal electron energy at the gyrotron output even at very large spread in pitch factor is explained. An estimation of the recuperation efficiency, which can be obtained due to this effect, is given. 相似文献
999.
We study general relativity in the framework of non-commutative differential geometry. As a prerequisite we develop the basic notions of non-commutative Riemannian geometry, including analogues of Riemannian metric, curvature and scalar curvature. This enables us to introduce a generalized Einstein-Hilbert action for non-commutative Riemannian spaces. As an example we study a space-time which is the product of a four dimensional manifold by a two-point space, using the tools of non-commutative Riemannian geometry, and derive its generalized Einstein-Hilbert action. In the simplest situation, where the Riemannian metric is taken to be the same on the two copies of the manifold, one obtains a model of a scalar field coupled to Einstein gravity. This field is geometrically interpreted as describing the distance between the two points in the internal space.Dedicated to H. ArakiSupported in part by the Swiss National Foundation (SNF) 相似文献
1000.
The literature published over the period 1986–1990 on the chemical properties (oxidation, addition, substitution, reactions of the functional groups, etc.) of 1,4-dihydropyridines is correlated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, No. 5, pp. 579–612, May, 1993. 相似文献