全文获取类型
收费全文 | 72篇 |
免费 | 0篇 |
专业分类
化学 | 59篇 |
力学 | 2篇 |
数学 | 7篇 |
物理学 | 4篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 3篇 |
2002年 | 3篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1993年 | 1篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1970年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
1966年 | 6篇 |
1964年 | 3篇 |
排序方式: 共有72条查询结果,搜索用时 159 毫秒
1.
Serafin Fraga 《International journal of quantum chemistry》1988,34(6):505-507
The quantity ? = (Φ||(H ? E)Φ|) gives a measure of the error in the approximate solution, Φ (with corresponding energy expectation value E), to an eigenfunction of the Hamiltonian operator H of the system under consideration; this quantity vanishes for the exact function ψ. In a percentage scale (with 0% error for the exact function and 100% for a reference, approximate function), the error of Φ may be expressed as 100(?/?r), where ?r corresponds to the reference function (e.g., obtained with a minimal basis set). This approach eliminates the need of knowing beforehand the exact solution in order to have an estimate of the error of an approximate solution. 相似文献
2.
Single crystals of potassium iron hydrogen phosphate, KFe3(HPO4)2(H2PO4)6 · 4 H2O, were prepared hydrothermally by heating a mixture of Fe2O3, H3PO4 and K2CO3 with a small amount of water. It crystallizes monoclinic, space group C2/c (N° 15 Int. Tab.) with Z = 4 and a = 1701(2), b = 960.4(5), c = 1750(1) pm, β = 90.88(7)°. The crystal structure was solved by using 1716 unique reflections F0 > 4σ(F0) with a final wR2 value of 0.126 (SHELXL-93). The main feature of the crystal structure are layers formed by PO4-tetrahedra around the FeO6-octahedra parallel to (001). K+ and H2O molecules connect these layers. Effective Coordination Numbers (ECoN), Mean Fictive Ionic Radii (MEFIR), Charge Distribution (CHARDI) and the Madelung Part of Lattice Energy (MAPLE) are calculated for the title compound. The existence of hydrogen bonds is confirmed by these calculations. 相似文献
3.
Physical properties of many-electron atomic systems evaluated from analytical Hartree-Fock functions
The promotion energies, ionization potentials, electron affinities, and orbital electronegativities for the valence states of importance in atoms of the first two rows of the periodic system have been evaluated from analytical Hartree-Fock functions for the corresponding groundstates. The agreement with existing values, determined from experimental data, is very satisfactory.This work has been supported in part by the National Research Council of Canada. 相似文献
4.
Physical properties of many-electron atomic systems evaluated from analytical Hartree-Fock functions
Numerical values are presented for the electric field gradients (q) and nuclear quadrupole coupling constants (eqQ) for a series of neutral atoms and their positive and negative ions. The angular dependence of the field gradient integrals is tabulated for configurations involving equivalent p and d electrons, for LS-coupling and central-force-field functions (e.g., Hartree-Fock functions).
This work has been supported in part by the National Research Council of Canada. 相似文献
Zusammenfassung Für eine Reihe neutraler Atome und ihre positiven und negativen Ionen werden Zahlenwerte für die elektrischen Feldgradienten (q) und die Kernquadrupolkopplungskonstanten (eqQ) berechnet. Für Konfigurationen, die gleichwertige p- und d-Elektronen enthalten, wird für LS-Kopplung und Zentralkraftfeldfunktionen (z. B. Hartree-Fock-Funktionen) die Winkelabhängigkeit der Feldgradientenintegrale in Tabellenform angegeben.
Résumé On présente les valeurs numériques pour les gradients de champ (q) et les constantes de couplage quadrupolaire (eqQ) pour des atomes neutres et leurs ions positives et négatives. On a calculé les valeurs des intégrales qui donnent la dependence angulaire du gradient de champ pour des configurations avec des électrons p et d équivalents, pour le couplage LS et fonctions de champ central (par exemple, fonctions de Hartree-Fock).
This work has been supported in part by the National Research Council of Canada. 相似文献
5.
Anastasiia M. Mishura Anna S. Sklyarova Dmitriy I. Sharapa Igor’ A. Levandovsky Michael Serafin Andrey A. Fokin Vladimir N. Rodionov 《Central European Journal of Chemistry》2013,11(12):2144-2150
The rearrangement of easily accessible Cookson’s diketone with chlorosulfonic acid in chloroform followed by the acidic hydrolysis gave 6-chloro-7-hydroxy-dichloropentacyclo[6.3.0.02,6.03,10.05,9]undecane-4-one, whose syn-stereochemistry was assigned through the X-ray crystal structure analysis. This key structure was used for the stereoselective synthesis of the D 3-trishomocubane derivatives as well as for the preparation of potential drugs bearing hydroxy- and amino-functional groups. A new multigram preparative synthesis of D 3-trishomocubane was developed. 相似文献
6.
The effect of chromatographic conditions on the separation of selected alkaloids on CN-silica layers
ABSTRACTSelected alkaloids were chromatographed on cyanopropyl-silica thin layers using nonaqueous and aqueous eluents containing various free silanol blocker agents. Because of the strong retention of these basic compounds, nonaqueous eluents containing medium polar diluents, strongly polar modifiers, or aqueous eluents containing organic modifier, water, and silanol blockers (ammonia, diethylamine, and ionic liquid) were required for analysis. Mobile phases containing addition of acids were also tested for separation of investigated alkaloids. The most selective and efficient systems were used in two-dimensional separations of isoquinoline alkaloids’ mixture and plant extracts. 相似文献
7.
8.
Fluoroquinolones are defined as an important group of synthetic antibacterial compounds, having a fluorine atom at position
6 and a piperazine ring at position 7 of quinolone-3-carboxylic acid. It was proved that the activity of quinolones was decreased
in the environment of certain metal ions by the formation of sparingly soluble metal complexes. The proposed reason for such
maintenance might be the chelate bonding of the quinolone to the metal. Again, it was proposed that metal ions, especially
magnesium ions, were engaged in the mode of action of quinolones. In this review article, selected structures of fluoroquinolones
metal complexes were performed and discussed in terms of their therapeutic application. The nuclease activity and antibacterial
activity tests were presented and the effects of metal complexes were compared to free fluoroquinolones. Finally, the results
were introduced.
The article is published in the original. 相似文献
9.
Diego Cortes José Luis Rios Angel Villar Serafin Valverde 《Tetrahedron letters》1984,25(30):3199-3202
The structures of Cherimolin and Dihydrocherimolin, two new antimicrobial γ-lactone-bis-tetrahydrofuranes from Mill., Annonaceae, have been elucidated by spectroscopic analysis. 相似文献
10.
Serafin Fraga 《Theoretical chemistry accounts》1964,2(5):403-405
A reformulation of the general self-consistent-field formalism is presented.
This work has been supported in part by the National Research Council of Canada. 相似文献
Zusammenfassung Es wird eine Umformulierung des allgemeinen self-consistent-field-Formalismus angegeben.
Résumé Le formalisme de la méthode du champ «gauto-cohérent» est reformulé.
This work has been supported in part by the National Research Council of Canada. 相似文献