全文获取类型
收费全文 | 869篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
化学 | 509篇 |
晶体学 | 2篇 |
力学 | 30篇 |
数学 | 86篇 |
物理学 | 270篇 |
出版年
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 22篇 |
2018年 | 19篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 24篇 |
2014年 | 36篇 |
2013年 | 48篇 |
2012年 | 58篇 |
2011年 | 56篇 |
2010年 | 38篇 |
2009年 | 24篇 |
2008年 | 30篇 |
2007年 | 40篇 |
2006年 | 20篇 |
2005年 | 25篇 |
2004年 | 19篇 |
2003年 | 22篇 |
2002年 | 18篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 11篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 14篇 |
1993年 | 9篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 13篇 |
1987年 | 20篇 |
1986年 | 12篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 8篇 |
排序方式: 共有897条查询结果,搜索用时 62 毫秒
91.
92.
The present communication reports the experimental values of NMR spin-lattice relaxation time (T1) and dielectric relaxation time (τ) of piperidine, pyrrole, pyridine, diethylamine, triethylamine and pyrrolidine. The values of activation energy (ΔEA) obtained using dielectric relaxation time, have been correlated with calculated values of ΔEA obtained using Arrhenius equation of NMR relaxation time (T1) for pyridine, diethylamine and pyrrole. Authors have also established a correlation between the experimental values of NMR spin-relaxation time (T1) with its calculated values obtained using different equations of dielectric relaxation time (τ). 相似文献
93.
J. G. Santos L. B. Silveira A. C. Oliveira V. K. Garg B. M. Lacava A. C. Tedesco P. C. Morais 《Hyperfine Interactions》2007,175(1-3):71-75
Transmission electron microscopy, X-ray diffraction and Mössbauer spectroscopy were used in the characterization of a nanocomposite containing magnetic nanoparticles dispersed in a glycolic acid-based template. Maghemite nanoparticles were identified as the iron oxide phase dispersed in the polymeric template. From the low-temperature Mössbauer data the amount of the iron-based, non-magnetic material at the nanoparticle surface was estimated as roughly one monolayer in thickness. 相似文献
94.
M.A.G. Soler G.B. Alcantara W.R. Viali J.R.L. Fernandez V.K. Garg P.C. Morais 《Surface science》2007,601(18):3921-3925
In this study γ-Fe2O3 nanoparticle, surface-coated with increasing amount of oleic acid, have been prepared while the stability against particle degradation under laser excitation intensity was investigated. Maghemite nanoparticle was obtained via oxidation of magnetite nanoparticle, the latter synthesized by co-precipitation of Fe (II) and Fe (III) ions in alkaline medium. By varying the experimental conditions of surface-coating maghemite nanoparticles with oleic acid, samples with different grafting coefficient were obtained and investigated using X-ray diffraction and different spectroscopic techniques, namely Raman, Mössbauer, and infrared. The amount of oleic acid adsorbed on the maghemite surface was estimated via the carbon content obtained from elemental analysis. 相似文献
95.
Polycyclic aromatic hydrocarbons (PAHs), apart from their carcinogenic and mutagenic nature, create many problems in the petrochemical industry due to their tendency toward carbonization. Compounds in C8 aromatic isomer feed are analyzed by means of sample concentration, followed by separation of individual compounds by gas chromatography on a stainless steel OV-101 phase capillary column and identification by gas chromatography/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy. Various compounds belonging to different classes (mainly monocyclic, dicyclic, and tricyclic aromatics), oxygenated aromatics, and aliphatic saturates are quantified in the concentrated hydrocarbon residue of C8 isomer feed. Both unsubstituted and alkyl substituted ring type compounds are present. Concentrations obtained for PAH compounds in the C8 isomer feed range from 0.2 to 0.42 micrograms/mL. 相似文献
96.
This is a study of the completeness properties of the space C
ps
(X) of continuous real-valued functions on a Tychonoff space X, where the function space has the pseudocompact-open topology. The properties range from complete metrizability to the Baire
space property.
Dedicated to Professor Robert A. McCoy 相似文献
97.
U. Garg A. Chaudhury M. W. Drigert E. G. Funk J. W. Mihelich 《Physics letters. [Part B]》1986,180(4):319-323
Lifetimes for levels in the yrast band of 184Pt have been measured up to spin 16+ using the recoil distance technique. The B(E2) values exhibit a marked increase in going from spin 2 to 10, consistent with a proposal that two bands of different deformations are mixing at low spin. This provides further support for shape coexistence occuring at low excitation energies in this region. 相似文献
98.
Santanu Mandal Ashok Kumar Rout Anupam Ghosh Guillaume Pilet Debasis Bandyopadhyay 《Polyhedron》2009,28(17):3858-3862
Two new mononuclear complexes of manganese(III) viz. [MnL2(LH)2]ClO4 (1) and [MnL2(N3)]·0.5CH3OH (2) have been synthesized by reacting manganese perchlorate with furfurylamine and salicylaldehyde (plus sodium azide in 2) where L = (2-hydroxybenzyl-2-furylmethyl)imine, an asymmetric bidentate Schiff base formed in situ to bind the Mn(III) ion. The complexes have been characterized by elemental analysis, IR spectroscopy, TGA and single crystal X-ray diffraction studies. Structural studies reveal that the complexes 1 and 2 adopt an octahedral and a square pyramidal geometry, respectively. The antibacterial activity of the complexes has been tested against Gram(+) and Gram(?) bacteria. 相似文献
99.
A series of novel luminescent cyclometalated Au(III) neutral complexes of the type cis-[(N(∧)C)AuL] [N(∧)C = 2-phenylpyridine (ppy), L = 1,1'-biphenyl (1)] and cis-[(N(∧)C)AuL(2)] [N(∧)C = 2-phenylpyridine (ppy), L = C(6)H(5) (2), C(6)F(5) (3), C(6)H(4)-CF(3)-p (4), 2-C(4)H(3)S (5)]; [N(∧)C = 2-(2-thienyl)pyridine (thpy), L = C(6)H(5) (6), C(6)F(5) (7)]; [N(∧)C = 2-(5-methyl-2-thienyl)pyridine (5 m-thpy), L = C(6)F(5) (8)] were successfully synthesized. The X-ray crystal structures of all compounds except 3 have been determined. These complexes were found to show long-lived emission in solution at room temperature. The emission origins of the complexes have been tentatively assigned to be derived from triplet states predominantly bearing intraligand (IL) character with some perturbation from the metal center. Density functional theory (DFT) calculations were performed to evaluate the stability associated with the complexes and TD-DFT calculations to ascertain the nature of the excited state. Variation of the cyclometalated ligands in the complexes readily leads to the tuning of the nature of the lower energy emissive states. 相似文献
100.