全文获取类型
收费全文 | 152篇 |
免费 | 2篇 |
专业分类
化学 | 70篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 8篇 |
物理学 | 72篇 |
出版年
2022年 | 2篇 |
2021年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 4篇 |
2014年 | 1篇 |
2013年 | 11篇 |
2012年 | 2篇 |
2011年 | 9篇 |
2010年 | 3篇 |
2009年 | 3篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 10篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 30篇 |
2001年 | 8篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有154条查询结果,搜索用时 15 毫秒
1.
M. Faucher D. Garcia E. Antic-Fidancev M. Lemaitre-Blaise 《Journal of Physics and Chemistry of Solids》1989,50(12)
Some structural and spectroscopic features of rare earth orthoaluminates are examined.The trigonal→ orthorhombic transition is studied in a series of NdxSm1−xAlO3 compounds. The evolution of the crystal structure is followed by X-ray analysis and optical absorption. The free ion and crystal field parameters of Nd3+ (4f3 configuration) are determined in LuAlO3:Nd3+.The anomaly of the calculated splitting of the
levels is slight, but well characterized in NdAlO3. The spin correlated crystal field and orbitally correlated crystal field models are tested as well as an empirical correction which was proposed earlier. 相似文献
2.
Emily S. Tepe Ellen S. Deutsch MD Quiana Sampson Stephen Lawless James S. Reilly Robert Thayer Sataloff 《Journal of voice》2002,16(2):244-250
The objective of this study was to determine the incidence of vocal problems in young choir singers and to correlate vocal problems with demographic and behavioral information. A questionnaire addressing vocal habits and hygiene was offered to 571 young choir singers, up to 25 years of age, who sing at least weekly; 129 (22.6%) responded. More than one-half of the respondents had experienced vocal difficulty, particularly older adolescents. Detrimental behaviors and circumstances surveyed were not reflective of the incidence of vocal difficulty, except for morning hoarseness, chronic fatigue, insomnia, and female gender after puberty. Voice care professionals should be aware that self-reported voice difficulties are common among young choral singers, especially postpubescent girls, and children with symptoms consistent with reflux (morning hoarseness) and emotional stress (insomnia). Laryngologists should communicate with choral conductors and singing teachers to enhance early identification and treatment of children with voice complaints, and to develop choral educational strategies that help decrease their incidence. 相似文献
3.
4.
5.
Using the results obtained from an MO SCF ab initio calculation on P2H4 in four different conformations, the 1J(PP) NMR coupling constants have been calculated. The 1J(PP) values are highly dependent upon the rotational angle φ (?238.0 Hz in the eclipsed conformation, 10.9 Hz in the staggered one). The shape of the theoretical 1J(PP) plot seems to be in good agreement with experimentally measured 1J(PP) values. 相似文献
6.
The solvolysis in acid solution of allylic halides and acetates of methylenecyclopropanes and cyclopropylmethanes does not lead to ring opening when there is an ethoxycarbonyl substituent on the ring methylene. Only the cyclopropenyl derivative is obtained. A study of the electronic structure and the geometry of the possible allylic cation intermediate has been carried out using the MNDO method. In addition, the influence of the substituents on the ring opening of this cation has beeen examined. It appears that the ring opening is disfavoured upon substitution of an alkyl group by alkoxymethyl on the ring methylene group. 相似文献
7.
Jean -François Labarre Marcel Graffeuil Jean -Paul Faucher Maurice Pasdeloup Jean -Pierre Laurent 《Theoretical chemistry accounts》1968,11(5):423-433
Résumé Une utilisation conjointe des méthodes L.C.A.O.-C.U.V. et d'itération tournante permet d'atteindre des structures électroniques ( + ) cohérentes avec l'U.V.(et donc le gradient de population électronique de liaison qui conditionne l'aromaticité) de huit borazines et boroxines, substitués ou non, de symètrie D
3h
. L'échelle d'aromaticité obtenue permet de rendre compte des propriétés magnétiques (RMN, RQ, effet Faraday, diamagnétisme) de ce type de molécules. On parvient en particulier aux deux conclusions essentielles suivantes: les borazines sont nettement plus aromatiques que les boroxines isologues et la greffe de groupements méthyles ou d'atomes de chlore, qu'elle se fasse sur le bore ou sur l'azote, confère toujours au dérivé substitué une aromaticité au moins égale à celle du borazine lui-même.
Recherche effectuée dans le cadre de la R.C.P. n du C.N.R.S. 相似文献
A simple method to calculate the - and -electron structure of borazines and of substituted boroxines of symmetry D3h: A theoretical estimation of the relative aromaticity of those molecules
( + ) electronic structures calculations are performed for eight D 3h borazines and boroxines, using in concert previously published U.V.-consistent H.M.O.-L.C.A.O. and bond by bond iteration methods. An estimation of bond electronic populations gradients is so obtained, allowing to set up a new aromaticity scale for such molecules. The main results are the following: Borazines are much more aromatic than isologous boroxines and B-or N-graft of alkyl groups or chlorine atoms never decreases (and generally increases) aromaticity.
Zusammenfassung Es wird für acht Borazol- und Boroxolverbindungen mit D 3h -Symmetrie unter Verwendung einer am UV-Spektrum geeichten iterativen HMO-LCAO-Theorie die - und -Elektronenstruktur bestimmt. Hiermit kann eine Abschätzung des Gradienten der Bindungselektronendichten gewonnen werden, aus der eine Einteilung der Moleküle nach ihrem aromatischen Charakter hervorgeht. Es ergibt sich, daß die Borazole aromatischer sind als die isoelektronischen Boroxole und daß eine Substitution der H-Atome am Bor oder Stickstoff durch Chlor oder Methylgruppen die Aromatizität fast immer erhöht, jedenfalls aber nie erniedrigt.
Recherche effectuée dans le cadre de la R.C.P. n du C.N.R.S. 相似文献
8.
Tran H Joubert P Bonamy L Lavorel B Renard V Chaussard F Faucher O Sinardet B 《The Journal of chemical physics》2005,122(19):194317
With the aim of temperature diagnostic, femtosecond time-resolved CARS (coherent anti-Stokes Raman spectroscopy) is applied to probe H2 in H2-N2 mixtures. In a first part, a Lorentzian profile is used to model the femtosecond CARS response. A difference between the experimental broadening and the expected one is observed in the collision regime. The observed broadening increases strongly in an inhomogeneous way with respect to the perturber concentration. This is of considerable importance for temperature measurements. In a second part, we show that in the collision regime, this inhomogeneous broadening is due to the speed dependence of the collisional parameters and the memory effects of the radiator speed. A new modelization of the time-resolved CARS response taking into account the speed memory effects is presented and applied to the temperature diagnostic in H2-N2 mixtures. The numerical results are in good agreement with experiments. 相似文献
9.
10.
Chloroacetaldehyde reacts with viral M13mp18 single and double stranded DNA to form the highly fluorescent adducts, etheno-AMP and etheno-CMP. Absorbance and fluorescence spectroscopy can be used to monitor and characterize these reactions. Both single and double stranded DNA showed increases in the absorbance following reaction with the aldehyde. The fluorescence also increased in these two groups and continued to rise with increasing time of incubation until a point of saturation was reached. The fluorescence of the double stranded moiety was considerably enhanced following reaction with the aldehyde while that of the single stranded population was not, making this method appropriate for the separation of small quantities of the two populations of DNA. 相似文献