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51.
We show, incorporating results obtained from numerical simulations, that in the Lorentz mirror model, the density of open paths in any finite box tends to 0 as the box size tends to infinity, for any mirror probability. 相似文献
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Cenek Kolar Manfred Gerken Hans-Peter Kraemer Karsten Krohn Haryanto Linoh 《Journal of carbohydrate chemistry》2013,32(2-3):223-234
ABSTRACT The synthesis of 7-O-α-L-daunosaminyl-4-O-methyl-β-rhodomycinone (3) and the determination of its cytotoxic potency compared to that of the natural 7-O-α-L-dau-nosaminyl-β-rhodomycinone (4) are described. Starting with natural β-rhodomycinone (7), trimethylsilyl protecting groups were attached to the hydroxy groups at position 7 and 10, and the 4-OH group was subsequently methylated (MeI/Cs2CO3), thus providing the 4-O-methyl-7, 10-bis-O-trimethylsilyl-β-rhodomycinone (10). The two TMS groups were then deblocked to give 4-O-methyl-β-rhodomycinone (12). In a 3-stage synthesis 12 was converted into 4-O-methyl-10-O-trifiuoroacetyl-ß-rhodomycinone (15) to which l, 4-bis-O-p-nitrobenzoyl-3-N-trifluoroacetyl-L-daunosamine 16 was selectively linked to afford the 7-O-α-glycoside 17. The acyl protective groups are removed by treatment with 1N NaOH to give 3. 相似文献
54.
Rausa Arshinova Raymond Kraemer Jacques Navech 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):281-284
Abstract L'étude par moment dipolaire de la conformation de huit perhydro oxazaphosphorines-1,3,2 est décrite. The conformation of eight perhydro 1,3,2-oxazaphosphorines is studied by means of dipole moments. 相似文献
55.
Kraemer K. Hauke Gelbrecht Maximilian Pavithran Induja Sujith R. I. Marwan Norbert 《Nonlinear dynamics》2022,108(2):1525-1545
Nonlinear Dynamics - A novel idea for an optimal time delay state space reconstruction from uni- and multivariate time series is presented. The entire embedding process is considered as a game, in... 相似文献
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W. Von Niessen W.P. Kraemer L.S. Cederbaum 《Journal of Electron Spectroscopy and Related Phenomena》1976,8(3):179-197
The valence ionization potentials (IP's) of furan and thiophene are studied by an ab initio many-body approach which includes the effects of electron correlation and reorganization beyond the Hartree—Fock approximation. For both molecules it is found that the ordering of the IP's as obtained in the Hartree—Fock approximation is correct. The assignment made for furan agrees with the ab initio calculation of Siegbahn, but it does not agree with the ordering proposed by Derrick et al. from their experimental investigations. For thiophene both the ordering of Derrick et al. and the one of Gelius et al. is shown to be incorrect concerning the position of the 1b1(π) IP. For both molecules the first two IP's are due to the 1a2(π) and the 2b1(π) molecular orbitals. For furan four orbitals of σ-type symmetry are placed between the 2b1 and the 1b1 π-orbitals, for thiophene there is only one. Several one-electron properties are calculated in the one-particle approximation and compared with experimental and other theoretical data. The localized molecular orbitals are also discussed. 相似文献
59.
Effects of anionic surfactants on ligand-promoted dissolution of iron and aluminum hydroxides 总被引:1,自引:0,他引:1
Carrasco N Kretzschmar R Pesch ML Kraemer SM 《Journal of colloid and interface science》2008,321(2):279-287
We investigated the influence of the surfactants sodium dodecyl sulfate (SDS) and rhamnolipid (RhL) on ligand-promoted dissolution of goethite (alpha-FeOOH) and boehmite (gamma-AlOOH) at pH 6. The siderophore desferrioxamine B (DFOB), its derivate desferrioxamine D (DFOD), ethylenediaminetetraacetic acid (EDTA), and 8-hydroxyquinoline-5-sulfonic acid (HQS) were used as ligands. The rates of ligand-promoted dissolution of goethite were significantly increased in the presence of low concentrations of anionic surfactants (<80 microM SDS; <6 mg/L RhL). At higher surfactant concentrations, however, the effects of surfactants were negligible. The dissolution rates in the presence of surfactants were not correlated with adsorbed amounts of ligands. Three possible factors contributing to these observations were further investigated and discussed: (i) adsorbed surfactants may influence ligand adsorption by changes in the ligand's surface speciation, (ii) re-adsorption of Fe-DFOB or Fe-DFOD complexes may lead to an underestimation of siderophore-promoted dissolution rates at high surfactant concentrations, and (iii) co-adsorption of protons to goethite with SDS may influence the dissolution rates. However, our results show that none of these three factors can satisfactorily explain the observed effects of anionic surfactants on ligand-promoted dissolution rates of iron and aluminum hydroxides. 相似文献
60.
Koeno Gravemeijer Geeke Bruin-Muurling Jean-Marie Kraemer Irene van Stiphout 《Mathematical Thinking and Learning》2016,18(1):25-44
This article offers a reflection on the findings of three PhD studies, in the domains of, respectively, subtraction under 100, fractions, and algebra, which independently of each other showed that Dutch students' proficiency fell short of what might be expected of reform in mathematics education aiming at conceptual understanding. In all three cases, the disappointing results appeared to be caused by a deviation from the original intentions of the reform, resulting from the textbooks' focus on individual tasks. It is suggested that this “task propensity”, together with a lack of attention for more advanced conceptual mathematical goals, constitutes a general barrier for mathematics education reform. This observation transcends the realm of textbooks, since more advanced conceptual mathematical understandings are underexposed as curriculum goals. It is argued that to foster successful reform, a conscious effort is needed to counteract task propensity and promote more advanced conceptual mathematical understandings as curriculum goals. 相似文献