全文获取类型
收费全文 | 209篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
化学 | 124篇 |
力学 | 4篇 |
数学 | 67篇 |
物理学 | 29篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 7篇 |
2014年 | 4篇 |
2013年 | 11篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 11篇 |
2008年 | 12篇 |
2007年 | 8篇 |
2006年 | 7篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1993年 | 4篇 |
1989年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1969年 | 4篇 |
1968年 | 4篇 |
1967年 | 6篇 |
1932年 | 2篇 |
1930年 | 1篇 |
1926年 | 1篇 |
1920年 | 1篇 |
1902年 | 1篇 |
1887年 | 1篇 |
1884年 | 1篇 |
1879年 | 1篇 |
排序方式: 共有224条查询结果,搜索用时 15 毫秒
1.
2.
Stéphanie Delbaere Gaston Vermeersch Jean-Claude MicheauAuthor vitae 《Journal of Photochemistry and Photobiology, C: Photochemistry Reviews》2011,12(2):74-105
The good understanding of a photochromic reaction mechanism requires the establishment of the list of all the transient species and the definition of their connecting processes. The purpose of kinetic studies is the determination of the main photochromic parameters, such as the quantum yields of photoisomerization, rate constants of thermal relaxation and spectra of transient species. These data allow the establishment of structure properties relationships in order to select the best substituents to improve photochromic performances within a given series. In this review, we describe the dynamic behaviour of various photochromic systems during thermal relaxation after irradiation, from the simplest mono-exponential decay to the more complicated multi-exponential dynamics. Then, we analyse the evolution of the long-lived isomers under continuous irradiation. Several pedagogical examples and tricks to perform easy kinetic analysis are given in the appendices. 相似文献
3.
4.
Zixin Huang Josie E. Auckett Peter E. R. Blanchard Brendan J. Kennedy Wojciech Miiller Qingdi Zhou Maxim Avdeev Mark R. Johnson Mohamed Zbiri Gaston Garbarino William G. Marshall Qinfen Gu Chris D. Ling 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(13):3482-3485
Pressure‐induced charge transfer from Bi to Ir/Ru is observed in the hexagonal perovskites Ba3+nBiM2+nO9+3n (n=0,1; M=Ir,Ru). These compounds show first‐order, circa 1 % volume contractions at room temperature above 5 GPa, which are due to the large reduction in the effective ionic radius of Bi when the 6s shell is emptied on oxidation, compared to the relatively negligible effect of reduction on the radii of Ir or Ru. They are the first such transitions involving 4d and 5d compounds, and they double the total number of cases known. Ab initio calculations suggest that magnetic interactions through very short (ca. 2.6 Å) M M bonds contribute to the finely balanced nature of their electronic states. 相似文献
5.
Carina Schönherr Sounia Touchene Gaston Wilser Regine Peschka-Süss Giancarlo Francese 《Journal of chromatography. A》2009,1216(5):781-786
In recent decades the use of liposomal preparations as drug delivery systems has become very attractive in pharmaceutical development. Therefore, thorough characterization and quantification of the lipids which form liposomes is wished from both investigators and regulatory authorities when the application in humans is being considered. In this study a new HPLC method for the detection of lipids in liposomal formulations was established using corona charged aerosol detection (CAD) which has the advantage to be independent of the chemical properties of the analytes. The superiority of this method over UV detection was demonstrated. Compared to UV detection no absorption effects of the organic solvent in the mobile phase interfering with the lipid signals were observed with CAD. CAD showed good linearity (R2 > 0.990) for all liposomal compounds. The acceptance criteria for precision including repeatability were met. The average recovery for each of the excipients of the liposomal formulation was in the range of 90.0–110%. 相似文献
6.
7.
Rafael de la Madrid Gaston Garcia-Calderon Juan Gonzalo Muga 《Czechoslovak Journal of Physics》2005,55(9):1141-1150
The goal of this contribution is to discuss various resonance expansions that have been proposed in the literature.
Presented at the 3rd International Workshop “Pseudo-Hermitian Hamiltonians in Quantum Physics”, Istanbul, Turkey, June 20–22,
2005. 相似文献
8.
Ortica F Moustrou C Berthet J Favaro G Samat A Guglielmetti R Vermeersch G Mazzucato U 《Photochemistry and photobiology》2003,78(6):558-566
A photophysical and photochemical study of a biphotochromic compound where two naphthopyran units are linked by an acetylene-thiophene-acetylene bridge has been carried out in toluene. Both fluorescence and intersystem crossing to the triplet manifold were found to compete with the photocoloration process. Two photoproducts (transoid-trans and transoid-cis stereoisomers), absorbing at approximately 480 nm and corresponding to the opening of a single photochromic unit, were detected by spectrophotometric analysis after short irradiation time in diluted solution and identified by 1H-nuclear magnetic resonance (NMR) spectroscopy. After prolonged irradiation at 228 K of highly concentrated solutions (up to 3 x 10(-3) mol dm(-3)), two additional isomers, absorbing at approximately 550 nm, were formed. Their NMR spectra indicate the opening of both photochromic units. An interesting effect of selective vibronic excitation was found, showing that the photoreaction is favored at excited vibronic levels to the detriment of the radiative relaxation. 相似文献
9.
Jirí Kozelka Roger Savinelli Gaston Berthier Jean-Pierre Flament Richard Lavery 《Journal of computational chemistry》1993,14(1):45-53
The antitumor drug cis-diamminedichloroplatinum(II) (cisplatin) binds preferentially to GpG and ApG sequences of DNA, forming N7,N7 intrastrand chelates. Molecular modeling of the intrastrand adducts have been handicapped, so far, by the lack of force-field data describing the Pt–guanine and Pt–adenine binding. We used ab initio calculations with relativistic pseudopotentials to evaluate three important parameters for the platinum–adenine model complex [Pt(NH3)3(Ade)]2+: (1) the force constant for the Pt? N7 bond bending out of the adenine plane; (2) the energy profile for the torsion about Pt? N7; (3) a set of fractional atomic charges that reproduce the ab initio potential for a number of space points placed around the adduct. A population analysis and comparative study on the tetrammine complex [Pt(NH3)4]2+ have shown that for platinum adenine is a better σ-donor than NH3, but its capacity as a π-acceptor is weak. © 1993 John Wiley & Sons, Inc. 相似文献
10.
Résumé Un calcul complet de constantes de couplage nucléaires J
HH, J
XH et J
XX (X = C, N, P) a été fait pour une série de molécules organiques dont les fonctions LCAO SCF MO exactes sont connues. L'influence de la charge nucléaire efficace des orbitales atomiques de base a été étudiée dans le cas particulier du méthane et de l'éthane. La décomposition des constantes de couplage en éléments de symétrie est employée pour la comparaison des résultats théoriques et expérimentaux.
Numerical calculations of spin-spin coupling constants with exact LCAO SCF MO functions
Complete calculations of nuclear spin-spin coupling constants J HH, J XH and J XX (X = C, N, P) have been carried out for some organic molecules the exact LCAO SCF MO functions of which are known. The results obtained using atomic basis sets with different orbital exponents are discussed in the case of methane and ethane. Theoretical values are compared to experimental data in terms of components arising from the symmetry analysis of actual coupling constants.
Zusammenfassung VollstÄndige Berechnungen der Spin-Spin-Kopplungskonstanten J HH, J XH und J XX (X = C, N, P) werden für einige organische Moleküle durchgeführt, deren genaue LCAO-SCF-MO-Funktionen bekannt sind. Der Einflu\ der effektiven Kernladungszahlen der Basisfunktionen wurde im Falle von Methan und Äthan untersucht. Die theoretischen und experimentellen Werte werden nach ihrer Zerlegung in Symmetriekomponenten miteinander verglichen.相似文献