全文获取类型
收费全文 | 323篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 271篇 |
力学 | 7篇 |
数学 | 3篇 |
物理学 | 52篇 |
出版年
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 8篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 5篇 |
2012年 | 16篇 |
2011年 | 21篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 13篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 15篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
排序方式: 共有333条查询结果,搜索用时 343 毫秒
11.
V.V. Boldyrev O.I. Lomovsky T.O. Zaikova E.F. Gavrilov 《Journal of solid state chemistry》1984,51(1):127-130
During the topochemical decomposition of ammonium perchlorate and copper hypophosphite an enhanced acid concentration occurs near the reagent-product interface. Concentration profiles of the acid were observed after the treatment of the partially decomposed crystals by indicator solution and by microphotometry. Profiles exhibit the diffusive characteristics. The diffusion coefficient is 10?10 cm2/sec for ammonium perchlorate and 10?9 cm2/sec for copper hypophosphite at 20°C. It is concluded that the variation of the reactivity near the interface is due to the enhanced acid concentration. 相似文献
12.
Ab initio calculations of the structure, force field, frequencies and intensities of normal modes of the LiBeF3 molecule have been carried out, using basis sets of Huzinaga and Dunning in a double-zeta contraction. The calculated results are compared with the infrared spectrum of LiBeF3 in an inert matrix obtained by Snelson et al. 相似文献
13.
14.
V. P. Koropchanu F. G. Paladii S. I. Boldyrev V. Ya. Gamurar' 《Journal of Structural Chemistry》1996,37(3):398-408
Tunnel-exchange states of tetrahedral tetrameric clusters dn-dn-dn+1-dn+1 with double transfer are considered to calculate the energy levels and wave functions. A method based on the second quantization
technique and group-theoretical approach is developed. The nature of the ground spin state of the above systems is determined.
It is shown that the structures have magnetic properties that radically differ from the properties of clusters with one migrating
electron (hole).
Moldova State University. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 3, pp. 458–470, May–June, 1996. 相似文献
15.
R. Paudert H. Harenz G. Heinicke L. Dünkel R. Pthig A. S. Kolosov V. V. Boldyrev M. V. Tschaikina M. I. Taranzowa G. I. Gordejewa 《无机化学与普通化学杂志》1979,452(1):141-150
Increase in the Reactivity of Apatitic Phosphates due to Mechanical Activation The lattice of natural apatitic phosphates was severely distorted by mechanical activation. At a high energy concentration in a centrifugal mill the crystals reach the X-ray amorphous state. The structural changes are investigated by infrared and X-ray methods. At increased degrees of activation the mechanically activated apatitic phosphates show enhanced solubility as a result of structural changes. 相似文献
16.
Zhai HJ Yang X Wang XB Wang LS Elliott B Boldyrev AI 《Journal of the American Chemical Society》2002,124(23):6742-6750
Although neutral and ionic O4(0/-/+) species have been observed experimentally and considered for energetic materials, O4(2-) and O5(2-) dianions have not yet been explored. O4(2-) is valent isoelectronic to the well-known ClO3- and SO3(2-) anions, and O5(2-) is valent isoelectronic to ClO4- and SO4(2-). All are stable, common anions in solutions and inorganic salts. In this article, we explore the possibility of making covalently bound O4(2-) and O5(2-) species stabilized in the forms of M+O4(2-) and M+O5(2-) (M = Li, Na, K, Cs) in the gas phase. Laser vaporization experiments using M-containing targets and an O2-seeded carrier gas yielded very intense mass peaks corresponding to MO4- and MO5-. To elucidate the structure and bonding of the newly observed MO4- and MO5- species, we measured their photoelectron spectra and then compared them with ab initio calculations and the spectra of ClO3-, Na+SO3(2-), ClO4-, and Na+SO4(2-). Careful analyses of the experimental and ab initio results showed, however, that the observed species are of the forms, O2-M+O2- and O2-M+O3-. The more interesting M+O4(2-) and M+O5(2-) species were found to be higher-energy isomers, but they are true minima on the potential energy surfaces, which suggests that it might be possible to synthesize bulk materials containing covalently bound tetra- and pentatomic oxygen building blocks. 相似文献
17.
V. V. Aleksandrov V. V. Boldyrev V. V. Marusin V. G. Morozov V. S. Solovjev T. M. Rozhentseva 《Journal of Thermal Analysis and Calorimetry》1978,13(2):205-212
Experimental data are presented on the kinetics and mechanism of PbO2 decomposition at heating rates varying from 0 to 2.5 · 103 °/sec. The studies were carried out with a time-of-flight mass spectrometer MSKH-4, a Paulik-Paulik-Erdey derivatograph and an X-ray diffractometer DRON-0.5At low heating rates (0 to 0.2 °/s) oxygen is evolved in four stages: PbO2 PbO1.56 PbO1.44 PbO. At extremely high heating rates (2 · 102–2.5 · 103 °/s) the number of stages is reduced to two: PbO2 PbO1.4 PbO. An attempt is made to connect the observed change in the decomposition mechanism of PbO2 with the crystal structure formation of the lead oxides.
Zusammenfassung Versuchsergebnisse bezüglich der Kinetik und des Mechanismus der Zersetzung von PbO2 bei Aufheizgeschwindigkeiten zwischen 0 und 2.5 · 103°/s werden mitgeteilt. Die Untersuchungen wurden mittels eines time-of-flight Massenspektrometers MSKH-4, eines Derivatographen des Typs Paulik-Paulik-Erdey und eines Röntgendiffraktometers DRON-0.5 durchgeführt.Bei niedrigen Aufheizgeschwindigkeiten (0 bis 0.2 °/sec) wird Sauerstoff in vier Stufen entwickelt: PbO2 PbO1.56 PbO1.44 PbO. Bei extrem hohen Aufheizgeschwindigkeiten (2 · 102 – 2.5 · 103°/s) wird die Zahl der Stufen auf zwei herabgesetzt: PbO2 PbO1.4 PbO. Es wird versucht die beobachtete Ánderung in dem Zersetzungsmechanismus von PbO2 mit der Kristallstrukturbildung der Bleioxide in Verbindung zu bringen.
Résumé On présente des résultats expérimentaux concernant la cinétique et le mécanisme de la décomposition de PbO2 pour des vitesses de chauffage allant de 0 à 2.5 · 103°/s. Les études ont été effectuées à l'aide d'un spectromètre de masse du type MSKH-4, d'un Dérivatograph du type Paulik-Paulik-Erdey et d'un diffractomètre des rayons X du type DRON-0,5.Aux faibles vitesses de chauffage (0 à 0.2°/s) l'oxygène se dégage en quatre étapes: PbO2 PbO1.56 PbO1.44 PbO. Aux vitesses de chauffage très élevées (2 · 102 à 2.5 · 103°/s) le nombre des étapes se réduit à deux: PbO2 PbO1.4 PbO. On essaye de relier le changement observé dans le mécanisme de décomposition de PbO2à la structure cristalline des oxydes de plomb.
PbO2 2.5 · 103°/c. — — MCX — 4, — — — 0.5. (0–0.2°/c) : PbO2 PbO1.56. PbO1.44 PbO. (2 · 102–2.5 · 103°/c) : PbO2 PbO1.4 PbO. PbO2 .相似文献
18.
H. -G. Weikert L. S. Cederbaum F. Tarantelli A. I. Boldyrev 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,18(3):299-305
We present a theoretical analysis on the existence of doubly negative molecular ions in the gas phase. A thorough investigation involves the discussion of two main problems: the stability of the system with respect to dissociation and the stability to the loss of an electron. An adequate treatment of both problems requires the choice of proper basis sets as well as the application of higher levels of theory. As an example the BeF 4 2? dianion is studied in detail. Here we use configuration interaction and many-body Green's function approaches. Strong basis set dependencies in the calculations are observed which have no analogy in neutral systems. 相似文献
19.
Naphthphosphacyclophanes based on symmetrical dihydroxynaphthalenes linked by diethylamidophospite groups were used to synthesize rhodium(I) complexes containing carb-onyl and acetylacetonato fragments. The physicochemical and spectral characteristics of the synthesized coordination systems were studied.
相似文献