全文获取类型
收费全文 | 229篇 |
免费 | 1篇 |
专业分类
化学 | 174篇 |
晶体学 | 1篇 |
数学 | 13篇 |
物理学 | 42篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 14篇 |
2015年 | 5篇 |
2014年 | 7篇 |
2013年 | 15篇 |
2012年 | 23篇 |
2011年 | 9篇 |
2010年 | 13篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 11篇 |
2005年 | 4篇 |
2004年 | 6篇 |
2003年 | 10篇 |
2002年 | 1篇 |
2001年 | 13篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1960年 | 2篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1955年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有230条查询结果,搜索用时 812 毫秒
221.
Density functional theory methods in combination with vibrational spectroscopy are used to investigate possible variants of molecular structure of the ion pairs of several imidazolium-based ionic liquids (ILs). Multiple stable structures are determined with the anion positioned (a) near to the C2 atom of the imidazolium ring, (b) between N1 and C5, (c) between N3 and C4, and (d) between C4 and C5. Chloride and bromide anions in vacuum also occupy positions above or below the imidazolium ring, but in the condensed state these positions are destabilized. In comparison with the halides that almost equally occupy the positions (a-d), tetrafluoroborate and hexafluorophosphate anions strongly prefer position (a). The position and the type of the anion influence the conformation of the side chains bound to the imidazolium N1 atom, which are able to adopt in vacuum all usual staggered or eclipsed conformations, although in the liquid state some of the conformations are present only as minor forms if at all. Vibrations of the cations depend both on the conformational changes and on the association with the anion. The formation of the ion pairs influences mainly stretching and out-of-plane vibrations of the imidazolium C-H groups and stretching vibrations of the perfluoroanions. Other modes of the ions retain their individuality and practically do not mix. This allows "interionic" vibrations to be separated and to regard the couple of the ions as an anharmonic oscillator. Such a model correlates the molecular structure of various ILs and their melting points without involving the energy of the interaction between the cations and anions but explains structure-melting point correlations on the grounds of quasy-elastic properties. 相似文献
222.
I. A. Zvereva I. V. Otrepina V. G. Semenov E. A. Tugova V. F. Popova V. V. Gusarov 《Russian Journal of General Chemistry》2007,77(6):973-978
The mechanism of formation of the perovskite-like layered structure of the oxide Gd2SrFe2O7 was studied. The limiting stages are those of formation of phases with perovskite (GdFeO3, SrFeO3?x ) and K2NiF4 (GdSrFeO4) structures. The Mössbauer study has shown that iron atoms exist in a heterovalent state (Fe3+ and Fe4+) only in the structure of SrFeO3?x ). 相似文献
223.
B. A. Komarov E. A. Dzhavadyan V. I. Irzhak A. G. Ryabenko V. A. Lesnichaya G. I. Zvereva A. V. Krestinin 《Polymer Science Series A》2011,53(6):502-509
The physical and mechanical properties of composite materials based on epoxy-amine systems—diglycidyl ether of diphenylolpropane-eutectic
mixture of aromatic amines (40 wt % m-phenylenediamine-60 wt % 4,4′-diaminodiphenylmethane) and epoxy-diane resin ED-20-eutectic mixture of aromatic diamines with
ultralow contents (≤0.1 wt %) of single-layer carbon nanotubes—are studied. It is shown that, for the concentration dependence
of the modulus of elasticity during tension, the additivity rule is obeyed only at the lowest concentrations of carbon nanotubes.
In this case, the presence of near-surface layers of a matrix with an increased elastic modulus should be considered. 相似文献
224.
Vladimir I. Galkin Elvira R. Zvereva Alexander A. Sobanov Irina V. Galkina Rafael A. Cherkasov 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract The Kabachnic-Fields reaction is one of the most important methods of synthesis of functionally substituted derivatives of tetracoordinated phosphorus with P-C bond. At the same time mechanism of this important and interesting reaction practically has not been investigated. 相似文献
225.
A. A. Burovikhina M. V. Chislov I. A. Rodionov D. A. Porotnikov I. A. Zvereva 《Russian Journal of General Chemistry》2014,84(10):1893-1898
Layered perovskite-like oxides ANdTa2O7 (A = H, Li, Na, K, Rb, Cs) were synthesized and characterized by means of diffuse reflection spectroscopy, thermogravimetry, and simultaneous thermal and X-ray phase analysis. Comparative analysis of the photocatalytic activity of ANdTa2O7 in the UV-induced hydrogen evolution from an aqueous isopropanol solution was performed. NaNdTa2O7 and HNdTa2O7 are able to intercalate water to the interlayer space. The compositions and thermal stability ranges of intercalates were determined. No explicit correlation between the photocatalytic activity of layered oxides and their ability to intercalate water to the interlayer space was found. 相似文献
226.
A. V. Krestinin A. V. Raevskii M. B. Kislov G. I. Zvereva O. I. Kolesova 《Kinetics and Catalysis》2008,49(1):68-78
A procedure was developed for measuring the kinetic parameters of growth of carbon fibers in the catalytic pyrolysis of hydrocarbons. In this procedure, the dependence of the averaged length of grown fibers on growth time is constructed based on the measurements of fiber lengths with an optical microscope. The procedure proposed allowed us to reliably determine the Arrhenius parameters of the rate of fiber growth and the induction period of fiber nucleation in the measurement of carbon fibers 100 nm or more in diameter. The kinetics of growth of carbon fibers from methane-hydrogen mixtures on an iron catalyst was measured over a temperature range of 950–1050°C. It was found that the rate of fiber growth as a function of methane activity in the gas phase exhibited a maximum in the activity range 200–300; the value of this maximum depends on the contribution of the products of gas-phase methane pyrolysis to the growth of fibers. It was also found that the rate of fiber growth dramatically increased as the critical concentration of pyrolysis products in the mixture was reached. This increase was interpreted as a change from one growth mechanism (growth from methane) to another growth mechanism (growth from acetylene). The experimental data explained the high sensitivity of the process of carbon fiber growth from methane to temperature and the residence time of the gas in the reactor. 相似文献
227.
Nikolay Davydov Dr. Asiya Mustafina Dr. Vladimir Burilov Dr. Elena Zvereva Prof. Sergey Katsyuba Dr. Liliya Vagapova Prof. Alexander Konovalov Dr. Igor Antipin 《Chemphyschem》2012,13(14):3357-3364
The complex formation of d‐metal ions at the interface of TbIII‐doped silica nanoparticles modified by amino groups is introduced as a route to sensing d‐metal ions and some organic molecules. Diverse modes of surface modification (covalent and noncovalent) are used to fix amino groups onto the silica surface. The interfacial binding of d‐metal ions and complexes is the reason for the TbIII‐centered luminescence quenching. The regularities and mechanisms of quenching are estimated for the series of d‐metal ions and their complexes with chelating ligands. The obtained results reveal the interfacial binding of CuII ions as the basis of their quantitative determination in the concentration range 0.1–2.5 μM by means of steady‐state and time‐resolved fluorescence measurements. The variation of chelating ligands results in a significant effect on the quenching regularities due to diverse binding modes (inner or outer sphere) between amino groups at the interface of nanoparticles and FeIII ions. The applicability of the steady‐state and time‐resolved fluorescence measurements to sense both FeIII ions and catechols in aqueous solution by means of TbIII‐doped silica nanoparticles is also introduced. 相似文献
228.
Krivoguz Yu. M. Yuvchenko A. P. Zvereva T. D. Pesetskii S. S. 《Russian Journal of Applied Chemistry》2001,74(5):845-850
The influence of carborane-containing peroxides on the efficiency of grafting of methylenebutanedioic acid to low-density polyethylene in a single-screw extrusion reactor equipped with a static mixer was studied. 相似文献
229.
V. V. Zvereva 《Journal of Applied Spectroscopy》2001,68(3):529-533
The quality of the image recorded on a synthesized hologram with different arrangements of the cameras forming the original images is analyzed. Optimum parameters of the positioning of cameras for forming images recorded on subholograms in order to construct composite holograms with minimum distortions have been obtained. 相似文献
230.
Aleksandr V. Ivanov Demid S. Popravko Irina V. Safenkova Elena A. Zvereva Boris B. Dzantiev Anatoly V. Zherdev 《Molecules (Basel, Switzerland)》2021,26(22)
Verifying the authenticity of food products is essential due to the recent increase in counterfeit meat-containing food products. The existing methods of detection have a number of disadvantages. Therefore, simple, cheap, and sensitive methods for detecting various types of meat are required. In this study, we propose a rapid full-cycle technique to control the chicken or pig adulteration of meat products, including 3 min of crude DNA extraction, 20 min of recombinase polymerase amplification (RPA) at 39 °C, and 10 min of lateral flow assay (LFA) detection. The cytochrome B gene was used in the developed RPA-based test for chicken and pig identification. The selected primers provided specific RPA without DNA nuclease and an additional oligonucleotide probe. As a result, RPA–LFA, based on designed fluorescein- and biotin-labeled primers, detected up to 0.2 pg total DNA per μL, which provided up to 0.001% w/w identification of the target meat component in the composite meat. The RPA–LFA of the chicken and pig meat identification was successfully applied to processed meat products and to meat after heating. The results were confirmed by real-time PCR. Ultimately, the developed analysis is specific and enables the detection of pork and chicken impurities with high accuracy in raw and processed meat mixtures. The proposed rapid full-cycle technique could be adopted for the authentication of other meat products. 相似文献