全文获取类型
收费全文 | 1179篇 |
免费 | 33篇 |
国内免费 | 4篇 |
专业分类
化学 | 880篇 |
晶体学 | 41篇 |
力学 | 15篇 |
数学 | 58篇 |
物理学 | 222篇 |
出版年
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 37篇 |
2017年 | 17篇 |
2016年 | 23篇 |
2015年 | 32篇 |
2014年 | 33篇 |
2013年 | 84篇 |
2012年 | 65篇 |
2011年 | 61篇 |
2010年 | 39篇 |
2009年 | 43篇 |
2008年 | 44篇 |
2007年 | 65篇 |
2006年 | 53篇 |
2005年 | 48篇 |
2004年 | 35篇 |
2003年 | 26篇 |
2002年 | 46篇 |
2001年 | 24篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 14篇 |
1996年 | 13篇 |
1995年 | 8篇 |
1994年 | 19篇 |
1993年 | 10篇 |
1992年 | 24篇 |
1991年 | 11篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 10篇 |
1984年 | 22篇 |
1983年 | 19篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1977年 | 10篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 8篇 |
1972年 | 6篇 |
1969年 | 9篇 |
排序方式: 共有1216条查询结果,搜索用时 0 毫秒
1.
S. M. Lenzi C. H. Dasso M. A. Nagarajan H. M. Sofia A. Vitturi 《Acta Physica Hungarica A》1997,6(1-4):95-98
The existence of a neutron skin in neutron-rich nuclei is discussed in connection with the excitation of isovector dipole and quadrupole giant modes via isoscalar nuclear probes. In the case of large neutron excess, important contributions are obtained from the nuclear excitation, which may even become predominant according to proper kinematical conditions. At variance with the usual situation encountered in inelastic processes, constructive interference can be found between nuclear and Coulomb contributions. 相似文献
2.
Scaling analysis of the magnitude series (volatile series) has been proposed recently to identify possible non-linear/multifractal signatures in the given data [Y. Ashkenazy, et al. Phys. Rev. Lett. 86 (2001) 1900; Y. Ashkenazy, et al. Physica A 323 (2003) 19; T. Kalisky, Y. Ashkenazy, S. Havlin. Phys. Rev. E 72 (2005) 011913]. In this article, correlations of volatile series generated from stationary first-order linear feedback process with Gaussian and non-Gaussian innovations are investigated. While volatile correlations corresponding to Gaussian innovations exhibited uncorrelated behavior across all time scales, those of non-Gaussian innovations showed significant deviation from uncorrelated behavior even at large time scales. The results presented raise the intriguing question whether non-Gaussian innovations can be sufficient to realize long-range volatile correlations. 相似文献
3.
Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy. 相似文献
4.
5.
R. Nagarajan S. Ayyappan C. N. R. Rao 《Physica C: Superconductivity and its Applications》1994,220(3-4):373-376
While YSr2Cu3O7 cannot be prepared under ambient conditions, partial substitution of the phosphate group for copper, as in YSr2Cu2.8(PO4)0.2Oy, stabilizes this phase in the orthorhombic structure, but the material is not superconducting. Superconductivity in YSr2Cu2.8(PO4)0.2Oy is obtained by increasing the hole concentration through partial substitution of Y by Ca, as in Y0.7Ca0.3Sr2Cu2.8(PO4)0.2Oy (Tc≈40 K). By incorporating the phosphate group in orthorhombic YBaSrCu3O 7, a stable tetragonal derivative of the formula YBaSrCu2.8(PO4)0.2Oy (Tc≈ 47 K) has been prepared; the Tc increases to 70 K by partial substitution of Y by Ca as in Y0.7Ca0.3BaSrCu2.8(PO4)0.2Oy. 相似文献
6.
Mariappan Periasamy Neela Kishorebabu K. Natarajan Jayakumar 《Tetrahedron letters》2007,48(11):1955-1958
N,N-Dialkylarylamines react with trimethyl orthoformate and TiCl4 under ambient conditions to give the corresponding formyl derivatives in 75-89% yields, whereas the corresponding arylated products are obtained from benzyl ethers and acetals in 42-78% yields. 相似文献
7.
Samath S. Abdul Raman Mani Raman Natarajan Jeyasubramanian Kadarkarai Thangam Ramalingam Suthamalli K. 《Transition Metal Chemistry》1992,17(1):13-15
Transition Metal Chemistry - The synthesis and structural characterization of new metal(II) chelates (M = CoII, NiII, CuII and ZnII) of neutral conjugated bidentate β-diketone ligands, having... 相似文献
8.
The syntheses of 7′-methoxy- and 5′,7′,6-trimethoxy-coumarino(3′,4′:3,2)coumarones (IIa and IIb) are described. 相似文献
9.
Extraction of promethium(III), uranium(VI), plutonium(IV), americium(III), zirconium(IV), ruthenium(III), iron(III) and palladium(II) has been carried out with a mixture of octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and tributyl phosphate (TBP) in dodecane. The effects of nitric acid, TBP and CMPO concentrations on the extraction of these metal ions have been studied. The nature of the species of the above metal ions extracted into the organic phase has been suggested. 相似文献
10.
Vijayasarathi Nagarajan Barbara Müller Oksana Storcheva Klaus Köhler Andreas Pöppl 《Research on Chemical Intermediates》2007,33(8):705-724
Interactions and binding sites of the solvent molecules chloroform and ethanol to bis(acetylacetonate)oxovanadium(IV) (VO(acac)2) complexes in (frozen) solutions have been investigated by pulsed electron nuclear double resonance, sum peak electron spin
echo envelope modulation and hyperfine sublevel correlation spectroscopy. The experimental proton hyperfine coupling data
of coordinating solvent molecules have been interpreted using quantum chemical calculations (density functional theory). Experimental
and computed hyperfine couplings indicate that ethanol coordinates to vanadium in the equatorial plane of VO(acac)2 and chloroform interacts via hydrogen bonding to oxygens of the acac ligands. 相似文献