全文获取类型
收费全文 | 567295篇 |
免费 | 4538篇 |
国内免费 | 1362篇 |
专业分类
化学 | 288576篇 |
晶体学 | 8189篇 |
力学 | 28063篇 |
综合类 | 18篇 |
数学 | 73551篇 |
物理学 | 174798篇 |
出版年
2021年 | 5365篇 |
2020年 | 5815篇 |
2019年 | 6586篇 |
2018年 | 8928篇 |
2017年 | 9078篇 |
2016年 | 12417篇 |
2015年 | 6632篇 |
2014年 | 11170篇 |
2013年 | 25075篇 |
2012年 | 19705篇 |
2011年 | 23270篇 |
2010年 | 17526篇 |
2009年 | 17428篇 |
2008年 | 22046篇 |
2007年 | 21840篇 |
2006年 | 19928篇 |
2005年 | 17779篇 |
2004年 | 16526篇 |
2003年 | 14959篇 |
2002年 | 14874篇 |
2001年 | 15854篇 |
2000年 | 12188篇 |
1999年 | 9444篇 |
1998年 | 8246篇 |
1997年 | 8046篇 |
1996年 | 7454篇 |
1995年 | 6728篇 |
1994年 | 6715篇 |
1993年 | 6508篇 |
1992年 | 6884篇 |
1991年 | 7332篇 |
1990年 | 7030篇 |
1989年 | 6976篇 |
1988年 | 6718篇 |
1987年 | 6511篇 |
1986年 | 6264篇 |
1985年 | 7850篇 |
1984年 | 8317篇 |
1983年 | 6982篇 |
1982年 | 7288篇 |
1981年 | 6748篇 |
1980年 | 6415篇 |
1979年 | 6934篇 |
1978年 | 7257篇 |
1977年 | 7153篇 |
1976年 | 7067篇 |
1975年 | 6747篇 |
1974年 | 6614篇 |
1973年 | 6873篇 |
1972年 | 5042篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
A converging perturbation series that can be summed analytically has been obtained for intersubband transitions of electrons
coherently tunneling through the middle of a dimensionally quantized level in an asymmetric double-barrier structure in a
high-frequency terahertz electric field. The possibility of a substantial increase in tunneling current accompanied by either
absorption or emission of a photon has been demonstrated. The quantum efficiency of radiative transitions between dimensionally
quantized levels can be up to 66%.
Zh. éksp. Teor. Fiz. 112, 237–245 (July 1997) 相似文献
22.
The changes in the magnetization of yttrium iron garnet (YIG) when irradiated by a pulsed neodymium laser beam with wavelength
λ=1.06 μm are investigated. Measurements are performed in the temperature range from 100 K to 600 K in various external magnetic
fields. YIG single crystals grown along the crystallographic (100), (110), and (111) directions are chosen so that the external
anisotropy of the indicated processes can be determined. Characteristic temperature intervals dominated by different mechanisms
of variation of the magnetization under the influence of a laser pulse are discussed.
Fiz. Tverd. Tela (St. Petersburg) 39, 1263–1266 (July 1997) 相似文献
23.
L. K. Aminov I. N. Kurkin D. A. Lukoyanov K. P. Chernov 《Physics of the Solid State》1997,39(8):1184-1186
Results are reported for measurements of the spin-lattice relaxation times of E′1 centers in quartz glass, produced by neutron irradiation, with the measurements made at two frequencies 9.25 and 24.0 GHz
over a wide temperature interval 1.5–300 K. The experimental data are interpreted on the basis of interaction mechanisms of
the spins with two-level systems with excitation energies ∼6, ∼26, and ∼420 cm−1. A small modification of the existing theory allows us to explain a number of features of the observed temperature and frequency
dependence of the relaxation rate. The results are compared with the data available in the literature on spin-lattice relaxation
of irradiation centers in crystalline quartz and quartz glass.
Fiz. Tverd. Tela (St. Petersburg) 39, 1335–1337 (August 1997) 相似文献
24.
V. A. Krakovskii 《Russian Physics Journal》1997,40(1):6-12
The problem of exciting bulk elastic waves at the surface of a piezoelectric with symmetries 422,622 has been solved by a
successive approximation method. In the approximation of a fixed electric field, created at the surface of the piezoelectric
crystal by a two-electrode transducer, the distributions are found for the shear wave stress and the energy flux density in
the far zone. The equivalent circuit parameters for a two-electrode radiator are determined taking account of the dynamic
piezoelectric correction obtained in the second approximation. The equivalent circuit parameters and the transducer loss are
treated for TeO2 crystals. A realistic possibility of using surface transducers in the development of acousto-optic modulators in the s.h.f.
region is shown.
Tomsk State Academy of Control Systems and Radio Electronics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika,
No. 1, pp. 8–15, January, 1997. 相似文献
25.
26.
27.
J. E. Fischer E. Werwa P. A. Heiney 《Applied Physics A: Materials Science & Processing》1993,56(3):193-196
We have used both reflection-geometry and grazing-incidence-geometry X-ray scattering to study thin films of C60 evaporated onto mica substrates via a hot-wall technique. The growth mode yields close-packed C60 planes, which are parallel to the substrate surface and which exhibit out-of-plane correlation lengths of 850 Å. In the film plane the C60 is at best pseudo-epitaxial, with a 0.9° distribution of crystallite orientations, a 450 Å in-plane correlation length, and a 3.7% lattice mismatch, better than obtained by other thin film techniques but far from the accepted definition of single crystal thin film epitaxy. 相似文献
28.
V. A. Nebol'sin B. M. Darinskii E. E. Popova A. A. Shchetinin 《Russian Physics Journal》1995,38(10):1023-1026
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995. 相似文献
29.
A. E. Dorokhov 《Czechoslovak Journal of Physics》2002,52(3):C79-C90
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed. 相似文献
30.
The radiation emitted by charged, scalar particles in a Schwarzschild field with maximal acceleration corrections is calculated classically and in the tree approximation of quantum field theory. In both instances the particles emit radiation that has characteristics similar to those of gamma-ray bursters. 相似文献