全文获取类型
收费全文 | 205922篇 |
免费 | 2353篇 |
国内免费 | 519篇 |
专业分类
化学 | 113108篇 |
晶体学 | 3665篇 |
力学 | 8121篇 |
综合类 | 11篇 |
数学 | 19923篇 |
物理学 | 63966篇 |
出版年
2020年 | 1802篇 |
2019年 | 1995篇 |
2018年 | 2300篇 |
2017年 | 2401篇 |
2016年 | 3619篇 |
2015年 | 2285篇 |
2014年 | 3651篇 |
2013年 | 9241篇 |
2012年 | 6710篇 |
2011年 | 8299篇 |
2010年 | 5862篇 |
2009年 | 5820篇 |
2008年 | 7364篇 |
2007年 | 7276篇 |
2006年 | 6900篇 |
2005年 | 6214篇 |
2004年 | 5659篇 |
2003年 | 5221篇 |
2002年 | 4994篇 |
2001年 | 6191篇 |
2000年 | 4664篇 |
1999年 | 3557篇 |
1998年 | 2772篇 |
1997年 | 2740篇 |
1996年 | 2652篇 |
1995年 | 2475篇 |
1994年 | 2377篇 |
1993年 | 2200篇 |
1992年 | 2859篇 |
1991年 | 2759篇 |
1990年 | 2700篇 |
1989年 | 2712篇 |
1988年 | 2740篇 |
1987年 | 2742篇 |
1986年 | 2618篇 |
1985年 | 3355篇 |
1984年 | 3366篇 |
1983年 | 2637篇 |
1982年 | 2741篇 |
1981年 | 2801篇 |
1980年 | 2577篇 |
1979年 | 2924篇 |
1978年 | 2881篇 |
1977年 | 2997篇 |
1976年 | 2836篇 |
1975年 | 2564篇 |
1974年 | 2528篇 |
1973年 | 2479篇 |
1972年 | 1708篇 |
1968年 | 1715篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The three-band two-dimensional repulsive Hubbard model in the formalism of the temperature Green function is investigated.
The applicability of the weak coupling approach at the values of the dimensionless coupling constant U/t≈10–11 is justified.
The normal state, the antiferromagnetic state with Neel magnetic ordering on the “copper” sublattice, and the superconducting
state with nontrivial Cooper pairing in channels with odd angular momenta are studied. The possibility of other magnetic states
in the model is discussed. Bibliography: 20 titles.
Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 209, 1994, pp. 194–228.
Translated by K. Malyshev. 相似文献
92.
A. K. Lopatin 《Ukrainian Mathematical Journal》1997,49(1):51-74
We consider the method of normal forms, the Bogolyubov averaging method, and the method of asymptotic decomposition proposed by Yu. A. Mitropol’skii and the author of this paper. Under certain assumptions about group-theoretic properties of a system of zero approximation, the results obtained by the method of asymptotic decomposition coincide with the results obtained by the method of normal forms or the Bogolyubov averaging method. We develop a new algorithm of asymptotic decomposition by a part of the variables and its partial case — the algorithm of averaging on a compact Lie group. For the first time, it became possible to consider asymptotic expansions of solutions of differential equations on noncommutative compact groups. 相似文献
93.
94.
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
95.
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
96.
I.K. Argyros 《Applied Mathematics Letters》1997,10(6):21-28
In this note, we use inexact Newton-like methods to find solutions of nonlinear operator equations on Banach spaces with a convergence structure. Our technique involves the introduction of a generalized norm as an operator from a linear space into a partially ordered Banach space. In this way, the metric properties of the examined problem can be analyzed more precisely. Moreover, this approach allows us to derive from the same theorem, on the one hand, semilocal results of Kantorovich-type, and on the other hand, global results based on monotonicity considerations. By imposing very general Lipschitz-like conditions on the operators involved, on the one hand, we cover a wider range of problems, and on the other hand, by choosing our operators appropriately, we can find sharper error bounds on the distances involved than before. Furthermore, we show that special cases of our results reduce to the corresponding ones already in the literature. Finally, several examples are being provided where our results compare favorably with earlier ones. 相似文献
97.
Whittum D.H. Ebihara K. Hiramatsu S. Kishiro J.-i. Monaka T. Ozaki T. Takayama K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(1):136-141
Studies of microwave amplification with an in-focused electron beam drawn from an induction injector are reported. A free-electron laser (FEL) operating at 9.4 GHz and employing ion-focusing within the interaction region has achieved power in excess of 30 MW at 9.4 GHz, with a beam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, with no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are poor frequency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed 相似文献
98.
G. N. Dalimova Kh. A. Abduazimov R. K. Rakhmanberdieva V. G. Gorokhova L. N. Petrushenko B. A. Babkin N. A. Koshilev 《Chemistry of Natural Compounds》1994,30(3):400-403
On the basis of the results of acid hydrolysis, chromatographic analysis of the hydrolysates, and a study of IR spectra, it has been established that the suspended particles liberated under the action of electrohydraulic shocks on heterodisperse water—plant systems consist of small fragments of the lignocarbohydrate complex of the plant tissue. 相似文献
99.
100.
M. S. Tashmukhamedov O. K Zakirova Sh. Ya. Mirzaakhmedov Sh. I. Salikhov I. T. Yakubov M. M. Rakhimov 《Chemistry of Natural Compounds》1994,30(1):97-100
Phospholipase A2 has been isolated fromthe venom of he Central Asian green toad Bufo viridis in the electroophoretically homogeneous state for the first time by biospecific absorption chromatography. The affinity sorbent used was Affi-Gel 10 with covalently bound phosphatidylserine (PDS). The chemical inertness of the bound PDS to the hydrolytic action of phospholipase A2 and its high tendency to form biospecific complexes have been shown. Some biochemical characteristics of the enzyme isolated have been studied: influence of the pH and of the Ca2+ concentration and dependence of activity on substrate concentration.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax 627071. Tashkent State University, fax 462472. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 105–109, January–February, 1994. 相似文献