全文获取类型
收费全文 | 17233篇 |
免费 | 2081篇 |
国内免费 | 1358篇 |
专业分类
化学 | 7186篇 |
晶体学 | 267篇 |
力学 | 334篇 |
综合类 | 33篇 |
数学 | 566篇 |
物理学 | 12286篇 |
出版年
2024年 | 25篇 |
2023年 | 112篇 |
2022年 | 287篇 |
2021年 | 315篇 |
2020年 | 314篇 |
2019年 | 375篇 |
2018年 | 384篇 |
2017年 | 474篇 |
2016年 | 711篇 |
2015年 | 624篇 |
2014年 | 821篇 |
2013年 | 1618篇 |
2012年 | 968篇 |
2011年 | 1295篇 |
2010年 | 939篇 |
2009年 | 1229篇 |
2008年 | 1117篇 |
2007年 | 1291篇 |
2006年 | 999篇 |
2005年 | 888篇 |
2004年 | 796篇 |
2003年 | 632篇 |
2002年 | 628篇 |
2001年 | 517篇 |
2000年 | 514篇 |
1999年 | 448篇 |
1998年 | 340篇 |
1997年 | 232篇 |
1996年 | 277篇 |
1995年 | 237篇 |
1994年 | 190篇 |
1993年 | 165篇 |
1992年 | 170篇 |
1991年 | 102篇 |
1990年 | 77篇 |
1989年 | 67篇 |
1988年 | 81篇 |
1987年 | 60篇 |
1986年 | 39篇 |
1985年 | 52篇 |
1984年 | 43篇 |
1983年 | 22篇 |
1982年 | 37篇 |
1981年 | 39篇 |
1980年 | 17篇 |
1979年 | 18篇 |
1978年 | 17篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
S.K. Mahapatra B.K. Dandapat 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,102(2):277-292
The current study addresses the mathematical modeling aspects of coupled conductive and radiative heat transfer in the presence of absorbing, emitting and isotropic scattering gray medium within two-dimensional square enclosure. A blended method where the concepts of modified differential approximation employed by combining discrete ordinate method and spherical harmonics method, has been developed for modeling the radiative transport equation. The gray participating medium is bounded by isothermal walls of two-dimensional enclosure which are considered to be opaque, diffuse and gray. The effect of various influencing parameters i.e., radiation-conduction parameter, surface emissivity, single scattering albedo and optical thickness has been illustrated. The adaptability of the present method has also been addressed. 相似文献
62.
Michael I. Mishchenko 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,101(3):411-415
The volume integral equation formalism is used to prove the scale invariance rule for an arbitrarily sized scatterer with an arbitrary shape, morphology, and orientation. The only assumptions are that the scatterer is made of optically isotropic linear materials and is embedded in a homogeneous, linear, isotropic, and nonabsorbing infinite medium. 相似文献
63.
64.
65.
66.
K. Prokeš 《Czechoslovak Journal of Physics》2002,52(2):253-258
Many materials exhibit various magnetic phenomena as a function of magnetic field, temperature and/or pressure. Usually, bulk magnetic measurements provide first information on the magnetic state of the material by measuring their response on the applied magnetic field. However, it is necessary to investigate materials also on a microscopic scale. This is often done by means of neutron scattering. In this contribution we discuss basic ideas of this method and we report on few experimental results obtained with a split-pair coil 14.5 T superconducting magnet which can be combined with dilution stick offering temperatures as low as 30 mK and/or with a small clamped-type pressure cell which offers pressure up to 1.0 GPa. 相似文献
67.
IR and Raman spectra of (NH4)3ZnCl5 have been recorded. The observed spectra have been analysed on the basis of the vibrations of ZnCl
4
2−
and NH
4
+
ions. The appearance of multiple Raman bands indicates the presence of two different types of ammonium ions. The effect of
anisotropic crystalline field over the ZnCl4 and NH4 tetrahedra is also discussed. The assignment of internal modes has been verified by the potential energy distribution calculations. 相似文献
68.
Justina Grabowska Karuna Kar Nanda R.T. Rajendra Kumar J.P. Mosnier M.O. Henry Simon B. Newcomb Patrick McNally Lisa OReilly Xu Lu Enda McGlynn 《Superlattices and Microstructures》2007,42(1-6):327
Self-organized ZnAl2O4 nanostructures with the appearance (in SEM) of high aspect ratio horizontal nanowires are grown on uncatalysed c-sapphire by vapour phase transport. The nanostructures grow as three equivalent crystallographic variants on c-sapphire. Raman and cathodoluminescence spectroscopy confirm that the nanostructures are not ZnO and TEM shows that they are the cubic spinel, zinc aluminate, ZnAl2O4, formed by the reaction of Zn and O with the sapphire substrate. 相似文献
69.
B. Sahoo W. Keune E. Schuster W. Sturhahn T. S. Toellner E. E. Alp 《Hyperfine Interactions》2006,168(1-3):1185-1190
Amorphous (a-) Fe x Mg1?x alloys are interesting materials for the investigation of non-Debye-like low-energy vibrational excitations. We have prepared a-Fe x Mg1?x alloy thin films (0.3 ≤ × ≤0.7) by vapour quenching. The amorphous state was confirmed by conversion electron Mössbauer spectroscopy between 4.2–300 K, and the x- and temperature-dependence of the isomer shift and hyperfine magnetic field was measured. For x= 0.6 and 0.7, magnetic ordering occurs below ~150 K. The atomic vibrational density of states, g(E), was determined by nuclear resonant inelastic scattering, providing clear evidence for the non-Debye-like low-energy vibrational excitations. 相似文献
70.
Chemisorption of polybenzimidazole on silver and copper etched with nitric acid has been observed by surface-enhanced Raman scattering (SERS). The polymer is found to react chemically with silver, forming a complexed film on the surface. The SERS spectra show that polybenzimidazole film inhibits oxidation of the metal at high temperature, unlike chemisorbed benzimidazole, benzotriazole, and poly(4-vinyl pyridine). © 1992 John Wiley & Sons, Inc. 相似文献