全文获取类型
收费全文 | 291505篇 |
免费 | 2076篇 |
国内免费 | 295篇 |
专业分类
化学 | 135264篇 |
晶体学 | 3590篇 |
力学 | 16448篇 |
综合类 | 7篇 |
数学 | 47535篇 |
物理学 | 91032篇 |
出版年
2021年 | 2040篇 |
2020年 | 2331篇 |
2019年 | 2726篇 |
2018年 | 11388篇 |
2017年 | 12106篇 |
2016年 | 8787篇 |
2015年 | 3446篇 |
2014年 | 4600篇 |
2013年 | 9022篇 |
2012年 | 11387篇 |
2011年 | 19708篇 |
2010年 | 12814篇 |
2009年 | 12919篇 |
2008年 | 17412篇 |
2007年 | 20533篇 |
2006年 | 7375篇 |
2005年 | 11838篇 |
2004年 | 8690篇 |
2003年 | 8309篇 |
2002年 | 6608篇 |
2001年 | 5703篇 |
2000年 | 4492篇 |
1999年 | 3228篇 |
1998年 | 2908篇 |
1997年 | 2663篇 |
1996年 | 2749篇 |
1995年 | 2356篇 |
1994年 | 2301篇 |
1993年 | 2369篇 |
1992年 | 2365篇 |
1991年 | 2558篇 |
1990年 | 2465篇 |
1989年 | 2541篇 |
1988年 | 2433篇 |
1987年 | 2473篇 |
1986年 | 2284篇 |
1985年 | 2883篇 |
1984年 | 2868篇 |
1983年 | 2488篇 |
1982年 | 2539篇 |
1981年 | 2432篇 |
1980年 | 2217篇 |
1979年 | 2558篇 |
1978年 | 2727篇 |
1977年 | 2725篇 |
1976年 | 2846篇 |
1975年 | 2635篇 |
1974年 | 2554篇 |
1973年 | 2794篇 |
1972年 | 2212篇 |
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
991.
A. I. Fedoseev S. G. Lushnikov S. N. Gvasaliya S. Kojima 《Physics of the Solid State》2006,48(6):1102-1105
The behavior of acoustic phonons in crystals of a relaxor ferroelectric, namely, the lead scandium tantalate PbSc1/2Ta1/2O3 (PST), is studied in the vicinity of the diffuse phase transition. The behavior of longitudinal and transverse acoustic phonons in a PST single crystal is examined using Brillouin scattering. The phonon subsystem is found to behave anomalously in the vicinity of T = 297 K, which can probably be assigned to the existence of a phase transition. Analysis of the results obtained yields the values of the elastic moduli C11, C12, and C44 for the cubic phase of the crystal over a wide temperature range. 相似文献
992.
The atomic structure and magnetic and electric properties of the Cr0.5TiSe2-Cr0.5TiTe2 system of intercalated phases were studied in detail by gradually replacing selenium by tellurium. It was revealed that this replacement changes the crystalline structure from monoclinic in the initial compounds to hexagonal in the compounds containing various types of chalcogen atoms; this is accompanied by disordering of chromium atoms in the van der Waals gaps. The electrical resistance and magnetic characteristics vary nonmonotonically on replacement of selenium by tellurium, which is associated with a change in the degree of atomic disordering during the transition from Cr0.5TiSe2 to Cr0.5TiTe2. 相似文献
993.
D. K. Kuznetsov I. S. Baturin V. Ya. Shur N. Menou C. Muller T. Schneller A. Sternberg 《Physics of the Solid State》2006,48(6):1174-1176
The effect of irradiation with electrons and neutrons and of exposure to synchrotron radiation on cyclic switching of polarization in thin films of lead zirconate titanate Pb(Zr,Ti)O3 (PZT) was studied. It is shown that variations in the shape of switching currents are due to the generation of a spatially nonuniform bound internal field with account for an increase in the rate of bulk screening caused by irradiation. A correlation between structural variations and the evolution of the switching current measured during and after irradiation is established. 相似文献
994.
I. V. Dzedolik 《Technical Physics》2006,51(7):932-937
Conditions for spontaneous symmetry breaking and generation of quasi-particles in an insulator through which an electromagnetic field propagates are considered. The order parameter of the system is determined. The mass spectrum of the quasi-particles is found in the cases of linear and nonlinear propagation through the medium with and without interfaces. 相似文献
995.
Photoelectronic spectra of volume samples of molybdenum, tungsten, and rhenium disilicides are theoretically investigated
as functions of the excitation energy (hv = 12–1486 eV) by the method of linearized attached plane waves. The main contribution
to the spectrum at low (hv = 12–52 eV) and very high (hv = 1486 eV) excitation energies is given by the metal d-states, while
the contribution of the Si p-states is dominant at intermediate excitation energies. An analysis of the calculated results
demonstrates that the main peak of the photoelectronic spectra is displaced by 0.2 eV toward the bottom of the valence band
when going from MoSi2 to WSi2; it is displaced by 0.3 eV when going from WSi2 to ReSi1.75.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 75–80, July, 2006. 相似文献
996.
997.
998.
The viscosity behavior, index of refraction, and density of dilute polycaproamide solutions in DMAc containing lithium chloride have been studied. On the basis of temperature dependences of the index of refraction and the density of solutions, the θ-condition of polycaproamide solutions in DMAc containing 2.5% lithium chloride is estimated as 21.3°C. From intrinsic viscosity [η] measurements, the coefficients of swelling of a polymer coil, the mean-square distance between chain ends, and other parameters of macromolecules in solution are calculated. 相似文献
999.
A. P. Tyutnev R. Sh. Ikhsanov E. L. Grin’ G. P. Safonov A. I. Kononenko A. M. Sorokin I. V. Rudenko 《Polymer Science Series A》2006,48(11):1190-1195
A general theory of the phenomenon of recovered voltage in polymers was considered on the basis of representation of an actual poling process by a discrete set of Debye relaxators. Examples of numerical solution of the direct and inverse problems are given. A correlation expression between intentionally aged polymer specimens and recovered-voltage curves was proposed for use in the assessment of the material state of a polymer under actual service conditions. It was shown that it is sufficient to restrict consideration to three relaxation processes in analysis of the phenomenon. 相似文献
1000.
A. Ferreira da Silva I. Pepe S.A. Tomás W.M. de Azevedo R. Ahuja 《Applied Surface Science》2006,252(15):5365-5367
In this paper we present spectroscopic properties of doped and undoped titanium dioxide (TiO2) as nanofilms prepared by the sol-gel process with rhodamine 6G doping and studied by photoacoustic absorption, excitation and emission spectroscopy. The absorption spectra of TiO2 thin films doped with rhodamine 6G at very low concentration during their preparation show two absorption bands, one at 2.3 eV attributed to molecular dimmer formation, which is responsible for the fluorescence quenching of the sample and the other at 3.0 eV attributed to TiO2 absorption, which subsequently yields a strong emission band at 600 nm. The electronic band structure and optical properties of the rutile phase of TiO2 are calculated employing a fully relativistic, full-potential, linearized, augmented plane-wave (FPLAPW) method within the local density approximation (LDA). Comparison of this calculation with experimental data for TiO2 films prepared for undoped sol-gels and by sputtering is performed. 相似文献