全文获取类型
收费全文 | 1139篇 |
免费 | 24篇 |
国内免费 | 6篇 |
专业分类
化学 | 762篇 |
晶体学 | 6篇 |
力学 | 29篇 |
数学 | 180篇 |
物理学 | 192篇 |
出版年
2022年 | 28篇 |
2021年 | 27篇 |
2020年 | 29篇 |
2019年 | 19篇 |
2018年 | 25篇 |
2017年 | 16篇 |
2016年 | 33篇 |
2015年 | 25篇 |
2014年 | 50篇 |
2013年 | 90篇 |
2012年 | 71篇 |
2011年 | 84篇 |
2010年 | 45篇 |
2009年 | 58篇 |
2008年 | 70篇 |
2007年 | 51篇 |
2006年 | 58篇 |
2005年 | 58篇 |
2004年 | 43篇 |
2003年 | 38篇 |
2002年 | 33篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 21篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 17篇 |
1995年 | 7篇 |
1994年 | 15篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1962年 | 2篇 |
排序方式: 共有1169条查询结果,搜索用时 0 毫秒
141.
S. L. Bogza S. Yu. Suikov N. M. Bogdan K. I. Kobrakov 《Chemistry of Heterocyclic Compounds》2004,40(10):1300-1304
The reaction of 3-acylamino- and 3-alkoxybenzo[c]pyrilium perchlorates with hydrazine has been studied. It was discovered that the direction of the recyclization of the pyran ring depends on the type of substituent in position 3 and on the ratio of reactants. Derivatives of isoquinoline and benzo-2,3-diazepine were obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No.10, pp. 1507–1511, October, 2004. 相似文献
142.
D. Bogdan 《Zeitschrift für Physik A Hadrons and Nuclei》1967,206(1):49-65
The general expressions for the beta transition matrix elements have been obtained using the Woods-Saxon wave functions for deformed nuclei proposed byFaessler andSheline. As an application the matrix elements for the 1?(β?)0+ and 1?(β?)2+ transitions of the170Tm nucleus have been calculated. The results indicate significant differences between the Nilsson and Woods-Saxon values of the nuclear parameters. Assuming a reasonableK=0 mixture in the ground state of the170Tm nucleus and a value near the Ahrens-Feenberg estimate for the ∫ α¦ ∫ir ratio it is possible to obtain an important improvement of the theoretical values of the relevant observables and especially of theft values. 相似文献
143.
Relative stabilities (ΔGc) of ammonium-bound monomers and dimers of anomeric β-
-pentofuranosyl 1α- and 1β-azide derivates are determinate using the kinetic method by measuring relative rates of competitive collision-induced dissociations of dimeric [ANH4B]+ and trimeric [A2NH4B]+ or [ANH4B2]+ cluster ions. Comparison between calculated ammonium affinities (AAs) and relative stabilities (ΔGc) of ammonium-bound monomers shows qualitative correlations between both thermochemical quantities, but in two examples the activation barrier differences of competitive fragmentation channels cause a large disparity between both thermochemical data. Therefore, the most stable ammonium-bound monomers of the anomeric lα- and lβ-2,3,5-tri-O-benzyl-β-
-arabino-pento-furanosyl azides possess the lowest ammonium affinities and the highest relative stabilities. Two different relative stabilities measured for the same ammonium-bound homo- or hetero-dimers indicate dissimilar activated barriers of trimers transition states for dimer formations. The activated barriers of trimers depend on the relative stabilities of ammonium-bound monomer within the trimeric cluster ions. 相似文献
144.
The theoretical beta decay observables are compared with the experimental values for the 0? → 2+ and 0? → 2+ transitions. By considering a Ho166 ground state configuration infered from (d, p) reaction experiments, and using all the matrix elements, satisfactory results are obtained for the 0? → 2+ transition. For the 0? → 2+ transition an important cancellation effect has been found which determines the failure of the ξ approximation and an energy dependent spectrum shape. 相似文献
145.
Bogdan Kurtev Ekaterina Simova Maya Victorova Nikolina Berova Stefanka Christoskova 《Monatshefte für Chemie / Chemical Monthly》1981,112(5):669-673
Diphenylhalonium salts were used in stereospecific N-phenylation of racemic and optically active 3-amino-2,3-diphenyl-1-propanols leading to 3-anilino-2,3-diphenyl-1-propanols. The absolute configurations of the latter and of genetically related compounds were established.
Stereochemische Korrelation von diastereomeren 3-Amino- mit 3-Arylaminosäuren bzw. ihrer Derivate durch stereospezifische N-Phenylierung mit DiphenylhaloniumsalzenKurze Mitteilung
Zusammenfassung Durch stereospezifische N-Phenylierung mit Hilfe von Diphenylhaloniumsalzen werden racemische sowie optische aktive 3-Amino-2,3-diphenyl-1-propanole in die entsprechenden 3-Anilino-2,3-diphenyl-1-propanole übergeführt. Auf Grund dieser Umwandlung wird die absolute Konfiguration der Aminoalkohole und davon abgeleiteter Derivate ermittelt.相似文献
146.
A good agreement between theory and experiment is achieved if besides the Coriolis force effect, the centrifugal and spin-spin polarization effects are considered in the calculation of the absoluteft values for the ΔN=2 beta transitions155Eu→155Gd. An important improvement is also obtained for the first forbidden transitions if the spin-spin polarization effects are taken into account. 相似文献
147.
Bogdan Sujak 《Czechoslovak Journal of Physics》1957,7(5):627-628
148.
Bogdan Ptaszyński 《Thermochimica Acta》1980,38(3):277-283
Thermal studies have been carried out on crystalline complexes formed between antimony(III) bromide and hydrobromides of some aromatic amines in concentrated hydrobromic acid solutions. Thermal analysis curves of the compounds under study are presented. Kinetic parameters of the thermal decomposition reactions were calculated from the TG curves using the Horowitz—Metzger method. A comparison of the thermal stabilities of the complexes was made. 相似文献
149.
The mechanism of the adsorption in nanometric cylindrical pores has been studied using grand canonical Monte Carlo simulations. The results have been analyzed from the point of view of microscopic correlations. It has been shown that the correlations between the energy components and between the energy and the number of adsorbed particles provide crucial information concerning the microscopic mechanism of the formation of adsorbed layers. Typical susceptibility functions have been calculated. They give the relations between the statistical correlations and the stability of the adsorbed system in different stages of adsorption. The numerical calculations have been carried out for Kr atoms adsorbed in an MCM-41 model porous material with pores of diameter d = 4 nm. The smooth-wall model as well as the model of a wall with micropores have been discussed. 相似文献
150.
Pawluc P Marciniec B Hreczycho G Gaczewska B Itami Y 《The Journal of organic chemistry》2005,70(1):370-372
Symmetrical 1,1-bis(silyl)ethenes have been easily prepared via ruthenium complex-catalyzed silylative coupling cyclization of 1,2-bis(dimethylvinylsiloxy)ethane to give 2,2,4,4-tetramethyl-3-methylene-1,5-dioxa-2,4-disilacycloheptane with excellent selectivity and good yield, followed by its reaction with Grignard reagents. The cyclic product can also be effectively transformed into cyclic carbosiloxane, 2,2,4,4,6,6,8,8-octamethyl-3,7-dimethylene-1,5-dioxa-2,4,6,8-tetrasilacyclooctane. 相似文献