全文获取类型
收费全文 | 495篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 379篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 61篇 |
物理学 | 64篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 13篇 |
2020年 | 15篇 |
2019年 | 7篇 |
2018年 | 5篇 |
2017年 | 7篇 |
2016年 | 20篇 |
2015年 | 14篇 |
2014年 | 17篇 |
2013年 | 37篇 |
2012年 | 37篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 25篇 |
2007年 | 25篇 |
2006年 | 21篇 |
2005年 | 23篇 |
2004年 | 19篇 |
2003年 | 14篇 |
2002年 | 20篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 8篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有516条查询结果,搜索用时 288 毫秒
461.
Hans Ågren Lennart Selander Joseph Nordgren Carl Nordling Kai Siegbahn Jiri Müller 《Chemical physics》1979,37(2):161-171
Soft X-ray emission spectra of the molecules CO, N2, NO and O2 are examined for the purpose of deriving information on their core hole energy curves. Molecular force constant and equilibrium bond lengths are determined for the core hole species C*O and N2*, and a qualitative analysis is made for CO*, N*O, NO* and O2*. The results show that differences of equilibrium geometries between the core hole states and the ground states are very well reproduced (better than 1 pm) by SCF calculations within the Hartree-Fock formalism. Inclusion of anharmonicity in the Franck-Condon analysis gives a small but significant effect on the best fitted value for the core hole state bond lengths (about 0.5 pm). Oxygen is binding energies determined from the X-ray spectra are shown to agree with ESCA data, in most cases within a few tenths of an eV. Calculated ΔSCF transition energies reproduce the experimental data within a few eV. 相似文献
462.
463.
Intensities of muonic radical spectra are compared with theoretical predictions to determine whether the radicals form epithermally or via thermal muonium. 相似文献
464.
Petr Kluson Libor Cerveny Jiri Had Simona Laurentova 《Reaction Kinetics and Catalysis Letters》1993,51(1):203-209
Ruthenium(III) chloride and ruthenium(IV) oxide have been reduced to unsupported ruthenium catalyst powders. The texture and properties of the catalysts were studied by SEM, XRD and BET techniques. The activity of the catalysts was tested in the liquid phase hydrogenation of benzene to cyclohexene and cyclohexane.Dept. of Organic TechnologyDept. of Solid State ChemistryDept. of Glass and Ceramics 相似文献
465.
466.
Quantitative capillary electrophoretic analysis of chiral compounds might be difficult or even impossible when baseline separation is not reached. In this work, the use of n-th derivative of the electropherogram was studied and examined on model and experimental data. The electropherograms should be first smoothed using Savitzky-Golay method and the quantitative analysis is then possible using either a graphical method or multivariate calibration applying a combination of experimental design (ED) and artificial neural networks (ANNs). The best results were obtained for the first derivative, higher derivatives are not suitable because of noise accumulation. The method was applied to real experimental data to quantify chiral amino acids from unresolved peaks, but it is applicable for quantitative analysis of any other chiral analytes from poorly resolved peaks. Precision of analysis from partially resolved peaks reached was about +/- 3.2% relative standard deviation. 相似文献
467.
Alzbeta Hutlova Daniel Niznansky Jiri Plocek Josef Bursik Jean-Luc Rehspringer 《Journal of Sol-Gel Science and Technology》2003,26(1-3):473-477
This paper aims to characterise the systems NiFe2O4/SiO2 and CoFe2O4/SiO2 prepared by the sol-gel method. After heat treatment, the various samples have been studied by means of X-ray diffraction, Mössbauer spectroscopy, magnetic measurements and transmission electron microscopy (HR TEM).X-ray diffraction and Mössbauer spectra confirmed the presence of the spinel phase. HR TEM observations revealed the nanocrystals with the size in the range of 2–25 nm. Magnetic measurements showed a superparamagnetic behaviour of the samples heated at lower temperature (800°C) and ferrimagnetic character for the samples heated at higher temperature (900, 1000°C).The final phase composition of the heated samples depends on the preparation conditions. The samples, treated up to 300°C in vacuum and then subsequently heated at 800°C or 900°C, do not contain hematite (the most stable phase at higher temperatures). On the contrary, the samples heated at 1000°C or 1250°C display certain content of hematite. 相似文献
468.
[reaction: see text] A new synthesis of thioethers is described. The reaction of boronic acids with aryl, heteroaryl, and alkyl N-thioimides in the presence of catalytic quantities of a Cu(I) carboxylate affords good to excellent yields of thioethers. This reaction takes place in the absence of a base under mild conditions (THF, 45-50 degrees C, 2.5-12 h) and represents an interesting complement to known methods for thioether synthesis. 相似文献
469.
Jiri Pinkas 《Journal of fluorine chemistry》2003,122(2):125-150
In this review we introduce a survey of organoaluminum fluorides with some examples of other related aluminum-fluorine compounds. A systematic overview of currently available synthetic methods for the preparation of organoaluminum fluorides is presented first. Then major examples of molecular structures of different classes of compounds are discussed in connection with their structural parameters and and NMR spectroscopic characteristics. 相似文献
470.
Reactions of Pr(NO3)3 with Ph2P(O)-CH2CH2-P(O)Ph2 and Ph2P(O)-C5H3N-P(O)Ph2 yielded layered network coordination polymers with bidentate ligands spanning the lanthanide atoms in a bridging fashion. The praseodymium cations with "spacer" ligands form two-dimensional building blocks assembling into either square grid or herringbone network. 相似文献