全文获取类型
收费全文 | 12825篇 |
免费 | 1213篇 |
国内免费 | 843篇 |
专业分类
化学 | 2800篇 |
晶体学 | 194篇 |
力学 | 729篇 |
综合类 | 112篇 |
数学 | 1309篇 |
物理学 | 9737篇 |
出版年
2024年 | 10篇 |
2023年 | 100篇 |
2022年 | 149篇 |
2021年 | 139篇 |
2020年 | 202篇 |
2019年 | 199篇 |
2018年 | 233篇 |
2017年 | 363篇 |
2016年 | 449篇 |
2015年 | 401篇 |
2014年 | 956篇 |
2013年 | 897篇 |
2012年 | 627篇 |
2011年 | 1159篇 |
2010年 | 784篇 |
2009年 | 934篇 |
2008年 | 881篇 |
2007年 | 974篇 |
2006年 | 786篇 |
2005年 | 593篇 |
2004年 | 530篇 |
2003年 | 498篇 |
2002年 | 460篇 |
2001年 | 391篇 |
2000年 | 325篇 |
1999年 | 339篇 |
1998年 | 298篇 |
1997年 | 159篇 |
1996年 | 171篇 |
1995年 | 130篇 |
1994年 | 109篇 |
1993年 | 99篇 |
1992年 | 75篇 |
1991年 | 66篇 |
1990年 | 66篇 |
1989年 | 43篇 |
1988年 | 45篇 |
1987年 | 45篇 |
1986年 | 22篇 |
1985年 | 31篇 |
1984年 | 31篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
71.
H. P. Gunnlaugsson 《Hyperfine Interactions》2006,167(1-3):851-854
The general problem of finding a distribution in hyperfine interaction parameters from experimental Mössbauer spectra is outlined. Existing methods may lack flexibility to be easily applicable to simple problems. A line shape for hyperfine parameter distributions is given, which is based on linear segments in the probability function. This method is applied in the analysis of samples containing iron in a silicate glass. 相似文献
72.
G. Gargaro F. Gasparrini D. Misiti G. Palmieri M. Pierini C. Villani 《Chromatographia》1987,24(1):505-509
Summary Enantiomers of several sulfoxides and some selenoxides can be easily separated by using a new chiral stationary phase (CSP-DACH-DNB)
containing the 3,5-dinitrobenzoyl derivative of R,R-(-)1,2-diamino-cyclohexane as selector, covalently bonded to the siliceous
matrix. The easy operative conditions and the high enantioselectivity values (α) allow a direct transfer of the analytical
separations to a semi-preparative and preparative scale. 相似文献
73.
We discuss the spectral lineshapes of reflectance and modulated reflectance (MR) measurements on optoelectronic device structures such as epi-layers, quantum wells (QWs), vertical-cavity surface emitting-lasers (VCSELs) and resonant-cavity light-emitting diodes (RCLEDs). We consider the various methods for the extraction of built-in electric fields and band-gap energies from Franz-Keldysh oscillations (FKO), using the example of a tensilely strained InGaAs QW system, whose InGaAsP barriers yield strong FKO. We describe how critical point transition energies can be easily obtained by eye from Kramers-Kronig (KK) transforms of low field or QW modulation spectra, using the example of the modulated transmittance spectra of dilute-nitrogen InGaAsN p-i-n structures. We also discuss how the ordinary reflectivity spectrum, usually acquired at the same time as the MR signal, may also be exploited to extract layer thicknesses and compositions, and information about the active QW absorption spectrum in VCSEL and RCLED structures. 相似文献
74.
Dendritic nanocrystalline CdS film was deposited at liquid-liquid interface of surfactants and an electrolyte containing 4 mmol L−1 cadmium chloride (CdCl2) and 16 mmol L−1 thioacetamide (CH3CSNH2) with an initial pH value of 5 at 15 °C by electrochemical synthesis. The nanofilm was characterized by transmission electron microscopy (TEM), field emission scanning electron microscope (FE-SEM), atomic force microscopy (AFM), ultraviolet visible (UV-vis) absorption spectroscopy and fluorescence spectroscopy. The surface morphology and particle size of the nanofilm were investigated by AFM, SEM and TEM, and the crystalline size was 30-50 nm. The thickness of the nanofilm calculated by optical absorption spectrum was 80 nm. The microstructure and composition of the nanofilm was investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), showing its polycrystalline structure consisting of CdS and Cd. Optical properties of the nanofilm were investigated systematically by UV-vis absorption and fluorescence spectroscopy. A λonset blue shift compared with bulk CdS was observed in the absorption spectra. Fluorescence spectra of the nanofilm indicated that the CdS nanofilm emitted blue and green light. The nanocomposites film electrode will bring about anodic photocurrent during illumination, showing that the transfer of cavities produces photocurrent. 相似文献
75.
In this paper, the possibility of using the gradients of the temperature and of the internal parameters as additional state variables in Continuum Thermodynamics is considered. The expressions of the two principles are discussed and Clausius–Duhem inequality is derived under an appropriate statement of the internal entropy production. Several formulations are proposed and compared to existing results in the literature. To cite this article: P. Ireman, Q.S. Nguyen, C. R. Mecanique 332 (2004). 相似文献
76.
Deependra Das Mulmi Nozomi Kamiya Yutaka Murakami 《Journal of Physics and Chemistry of Solids》2004,65(6):1181-1185
Nb-doped anatase TiO2 single crystal has been grown by chemical vapour transport method. Raman spectra shows that the obtained crystal with Nb of 0.08 wt% has typical anatase structure. An absorption band was observed at around 2.2 eV, which seems to be due to the d-d transition in the conduction band. The electron paramagnetic resonance and electric resistivity measurements show that the doped niobium makes quite shallow donor level whose orbital is dxy-like centered at the titanium position of anatase. 相似文献
77.
Othman Belhadj Miled David Grosso Jacques Livage 《Journal of Physics and Chemistry of Solids》2004,65(10):1751-1755
This paper describes the synthesis and optical pH sensing properties of a pH indicator dye activated mesostructured silica coated optical fibre. The pH-sensitive dye bromothymol blue was incorporated into the mesostructure sol precursor and thin films/coatings were used for pH-sensing applications without prior removal of the surfactant. The pH sensitivity range and operating wavelength were analysed by absorption measurements on layer dip-coated on glass slides. The pH sensing properties of coated optical fibre were tested by evanescent wave method. Experiments were carried out by using a series of solutions of known pH. No leaching was observed (except at very high pH) and an excellent reversibility was obtained between pH=2 and 5. 相似文献
78.
P.S Erdman M Fajardo K.M Sando W.C Stwalley 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,88(4):447-481
Experimental results are reported for a unique spectroscopic device called the Plasma Spectroscopy Cell. Optical absorption of lithium metal vapor was observed at high density and temperature. Absorption spectra are analyzed using theoretical calculations of absorption cross sections for lithium-helium interactions, and singlet and triplet state transitions of diatomic lithium in the visible spectral range. This is believed to be the most complex example yet calculated in which absolute bound-bound, bound-free, free-bound, and free-free contributions for all possible optically allowed transitions are all included, in quite respectable agreement with experiment. 相似文献
79.
A detailed study of the generalized M2 factor of hard-edged diffracted beams based on the truncated second-order moments method, asymptotic analysis and self-convergent beam width approach is performed. The dependence of the generalized M2 factor on the parameters characterizing the spatial profile, and beam truncation, etc. is analyzed. 相似文献
80.