全文获取类型
收费全文 | 71283篇 |
免费 | 7199篇 |
国内免费 | 5836篇 |
专业分类
化学 | 44257篇 |
晶体学 | 1222篇 |
力学 | 3855篇 |
综合类 | 397篇 |
数学 | 7560篇 |
物理学 | 27027篇 |
出版年
2023年 | 682篇 |
2022年 | 1264篇 |
2021年 | 1579篇 |
2020年 | 1730篇 |
2019年 | 1803篇 |
2018年 | 1776篇 |
2017年 | 1748篇 |
2016年 | 2413篇 |
2015年 | 2282篇 |
2014年 | 3005篇 |
2013年 | 4455篇 |
2012年 | 4876篇 |
2011年 | 5331篇 |
2010年 | 3930篇 |
2009年 | 3981篇 |
2008年 | 4392篇 |
2007年 | 3889篇 |
2006年 | 3598篇 |
2005年 | 2977篇 |
2004年 | 2463篇 |
2003年 | 2101篇 |
2002年 | 2072篇 |
2001年 | 2250篇 |
2000年 | 1707篇 |
1999年 | 1406篇 |
1998年 | 1038篇 |
1997年 | 974篇 |
1996年 | 856篇 |
1995年 | 753篇 |
1994年 | 726篇 |
1993年 | 608篇 |
1992年 | 636篇 |
1991年 | 609篇 |
1990年 | 596篇 |
1989年 | 507篇 |
1988年 | 524篇 |
1987年 | 490篇 |
1986年 | 444篇 |
1985年 | 486篇 |
1984年 | 494篇 |
1983年 | 370篇 |
1982年 | 397篇 |
1981年 | 387篇 |
1980年 | 327篇 |
1979年 | 418篇 |
1978年 | 382篇 |
1977年 | 403篇 |
1976年 | 395篇 |
1975年 | 345篇 |
1973年 | 338篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
111.
112.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
113.
Inspired by the recent work [HHM03], we prove two stability results for compact Riemannian manifolds with nonzero parallel spinors. Our first result says that Ricci flat metrics which also admit nonzero parallel spinors are stable (in the direction of changes in conformal structures) as the critical points of the total scalar curvature functional. Our second result, which is a local version of the first one, shows that any metric of positive scalar curvature cannot lie too close to a metric with nonzero parallel spinor. We also prove a rigidity result for special holonomy metrics. In the case of SU(m) holonomy, the rigidity result implies that scalar flat deformations of Calabi-Yau metric must be Calabi-Yau. Finally we explore the connection with a positive mass theorem of [D03], which presents another approach to proving these stability and rigidity results. Dedicated to Jeff Cheeger for his sixtieth birthday 相似文献
114.
Comprehensive studies of X-ray diffraction, oxygen content, superconductivity and Mössbauer effect have been made on FexCu1−xBa2YCu2O7+y superconductors (0.00≤x≤0.70) synthesized by ambient (AM) and high pressure (HP). Results indicate that all the HP-samples have tetragonal structure, smaller lattice parameter c and unit-cell volume than the AM-samples. The studies of oxygen content, and Mössbauer spectroscopy indicate that the HP-samples have higher oxygen content, carrier concentration and average valence of Fe than the AM-samples. Moreover, for the HP-samples more Fe atoms located in CuOx chains have fivefold-oxygen coordination. These are important reasons for the enhancement of Tc in the HP-samples. 相似文献
115.
116.
117.
We investigate the origin of ultraviolet (UV) emission from Mg0.12 Zn0.88 O alloy thin films with a wurtzite structure fabricated on c-plane Al2O3 substrates by plasma assisted molecular beam epitaxy. At room temperature, the absorption edge and UV emission band of the Mg0.12Zn0.88O film shift to high-energy side compared with ZnO films. Temperature dependence of the photoluminescence spectra shows that the UV emission is composed of free exciton and neutral donor bound exciton emissions. Two-step dissociation processes of the UV emission are observed with the increasing temperature. The thermal quenching mechanism is attributed to the dissociation of the free exciton from the neutral donor bound exciton in the low temperature region and the dissociation of free electron and hole from the free exciton in the high temperature region. 相似文献
118.
I. A. Uspenskaya Z. S. Vakhovskaya M. M. Efremova M. L. Kovba A. L. Emelina Zh. V. Dobrokhotova Yu. V. Goryushkina L. A. Tiflova A. A. Popova A. S. Monaenkova 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(4):529-534
The thermodynamic properties of the Ln2BaO4 phases (Ln = Dy, Ho, Sm) were studied by the electromotive force method with a fluoride electrolyte (890–1180 K), solution calorimetry in 1.07 N hydrochloric acid at 298.15 K, and differential scanning calorimetry (298–860 K). The experimental data were jointly processed, and the thermodynamic functions of the compounds over the temperature range 298–1200 K were calculated. 相似文献
119.
Mo2Ni3Si/NiSi metal silicide composite coatings with a fine microstructure consisting of Mo2Ni3Si primary dendrites and the interdendritic Mo2Ni3Si/NiSi eutectics were fabricated on austenitic stainless steel AISI 321 by laser cladding process. Small amplitude reciprocating sliding wear resistance of the coatings is evaluated as functions of normal load and slip amplitude and the wear mechanisms were discussed based on worn surface morphology observations. Results showed that the Mo2Ni3Si/NiSi coatings have excellent small amplitude reciprocating sliding wear resistance. 相似文献
120.
Z. Karaoglanov 《Fresenius' Journal of Analytical Chemistry》1941,121(5-6):190-209
Ohne Zusammenfassung 相似文献