全文获取类型
收费全文 | 4676篇 |
免费 | 162篇 |
国内免费 | 12篇 |
专业分类
化学 | 2780篇 |
晶体学 | 87篇 |
力学 | 150篇 |
数学 | 331篇 |
物理学 | 1502篇 |
出版年
2023年 | 42篇 |
2022年 | 92篇 |
2021年 | 82篇 |
2020年 | 101篇 |
2019年 | 93篇 |
2018年 | 115篇 |
2017年 | 85篇 |
2016年 | 132篇 |
2015年 | 109篇 |
2014年 | 162篇 |
2013年 | 262篇 |
2012年 | 348篇 |
2011年 | 338篇 |
2010年 | 194篇 |
2009年 | 172篇 |
2008年 | 202篇 |
2007年 | 190篇 |
2006年 | 189篇 |
2005年 | 151篇 |
2004年 | 117篇 |
2003年 | 115篇 |
2002年 | 90篇 |
2001年 | 79篇 |
2000年 | 64篇 |
1999年 | 56篇 |
1998年 | 32篇 |
1997年 | 54篇 |
1996年 | 64篇 |
1995年 | 45篇 |
1994年 | 76篇 |
1993年 | 82篇 |
1992年 | 81篇 |
1991年 | 52篇 |
1990年 | 51篇 |
1989年 | 57篇 |
1988年 | 40篇 |
1987年 | 43篇 |
1986年 | 41篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 37篇 |
1982年 | 39篇 |
1981年 | 50篇 |
1980年 | 40篇 |
1979年 | 31篇 |
1978年 | 26篇 |
1977年 | 34篇 |
1975年 | 24篇 |
1974年 | 27篇 |
1973年 | 33篇 |
排序方式: 共有4850条查询结果,搜索用时 15 毫秒
991.
The triglyceride profiles for corn, soybean, sunflower, grapestone, olive and olive husks oils were obtained by high temperature capillary gas chromatography on HT-FS capillary columns coated with OV-17-OH. The data were treated by methods of computerized pattern analysis, involving principal component analysis, discriminant analysis, and hierarchical clustering. A graphical representation of results as “star symbol plots” allows prompt visual recognition of the characteristic profiles and straightforward qualitative identification of unknowns as well as recognition of adulterations. 相似文献
992.
Tunable mid-infra-red radiation by singly resonant optical parametric oscillation based on KTA crystal pumped by multi-axial
Gaussian shape beam from Q-switched Nd:YAG laser has been demonstrated. Threshold energy of oscillation at different idler
wavelengths for different cavity length has been demonstrated. Single pass conversion efficiency of incident pump energy to
infra-red wavelength has also been measured. 相似文献
993.
A. Poddar S. Das D. Plachke H.D. Carstanjen 《Journal of magnetism and magnetic materials》2006,300(2):263-272
We report measurements of electrical resistivity (ρ), Hall coefficient (RH), magnetization (M) and specific heat (Cp(T)) of high-quality icosahedral Al70.4Pd20.8Mn8.8 phases with different thermal treatment. An improvement in the quasi-crystallinity upon the annealing treatment caused a drastic increase in ρ up to 7000 μΩ cm accompanied by a very small electronic specific heat coefficient γ. The low temperature ρ(T) data has been analyzed in terms of weak localization and electron–electron interaction effects. The Hall resistivity (ρH) is found to be strongly temperature-dependent and varies linearly with the magnetization (M) for the same field and temperature. Magnetization measurement reveals that more conductive samples are more magnetic and vice versa. Magnetic susceptibility (χ) data of all the annealed samples agrees with the Curie–Weiss-like behavior implying the existence of localized moments. The negative Curie–Weiss temperature (θ) indicates strong antiferromagnetic coupling between individual Mn atoms. The magnetic Mn concentration is found to be small, ranging from 1.73×10-4 for the less magnetic sample studied up to 3×10-3 for the more magnetic one. The small electronic specific heat coefficient obtained for all the samples suggests a significant reduction in the electronic density of states (DOS) at the Fermi level (EF) upon thermal annealing treatment. 相似文献
994.
995.
996.
997.
998.
999.
N. R. Das 《Journal of Radioanalytical and Nuclear Chemistry》1988,122(1):13-18
The potential use of ascorbic acid as a complexing reagent in the separation and preconcentration of rare earth elements (REE) in geological materials in a suitable solid matrix has been demonstrated. Traces of REE from some USGS standard rock samples, viz., GSP-1, G-2, AGV-1 and PCC-1, have been separated after acid dissolution in two ways: (1) by ion exchange chromatography on Dowex 50×8 column and Na-ascorbate as eluent and (2) by direct complexation with ascorbic acid under specific experimental conditions. The separated REE were coprecipitated with the non isotopic diluent, calcium fluoride, before neutron activation analysis. Radiometric determinations showed that the overall recovery of REE in both cases was practically quantitative. 相似文献
1000.
Summary The reaction between sulphite and gold(III) in hydrochloric acid medium has been studied; an initial complex is formed prior to electron transfer. The reaction rate is inversely proportional to the hydrogen ion concentration and the reaction appears to proceed through the intermediate formation of a free radical which reacts with gold(III) to give the products. Evidence for the formation of dithionate together with sulphate is presented. 相似文献