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171.
Moônica M. Bastos Lúcia M. U. Mayer Elza C. S. Figueira Marcio Soares Núbia Boechat Warner B. Kover 《Journal of heterocyclic chemistry》2008,45(4):969-973
This work describes the synthesis of new 3‐trifluoromethylindoles. Different isatins were trifluoromethylated using (trifluoromethyl) trimethylsilane (Me3SiCF3) as a nucleophilic agent giving new 3‐hydroxy‐3‐(trifluoromethyl)indolin‐2‐one. Different “one‐step” procedures to transform the latter compounds into the reduced indoles were attempted, but failed. For the synthesis of the new trifluoromethylindoles the corresponding 2‐oxo‐3‐(trifluoromethyl)indoles were reduced using borane/THF complex to furnish 3‐(trifluoromethyl)indolin‐3‐ol that additionally were dehydrated using thionyl chloride in pyridine to give excellent yields of the desired products. 相似文献
172.
Hop (Humulus lupulus L., Cannabaceae family) is prized for its essential oil contents, used in beer production and, more recently, in biological and pharmacological applications. In this work, a method involving headspace solid-phase microextraction and gas chromatography-mass spectrometry was developed and optimized to establish the terpenoid (monoterpenes and sesquiterpenes) metabolomic pattern of hop-essential oil derived from Saaz variety as a mean to explore this matrix as a powerful biological source for newer, more selective, biodegradable and naturally produced antimicrobial and antioxidant compounds. Different parameters affecting terpenoid metabolites extraction by headspace solid-phase microextraction were considered and optimized: type of fiber coatings, extraction temperature, extraction time, ionic strength, and sample agitation. In the optimized method, analytes were extracted for 30 min at 40°C in the sample headspace with a 50/30 μm divinylbenzene/carboxen/polydimethylsiloxane coating fiber. The methodology allowed the identification of a total of 27 terpenoid metabolites, representing 92.5% of the total Saaz hop-essential oil volatile terpenoid composition. The headspace composition was dominated by monoterpenes (56.1%, 13 compounds), sesquiterpenes (34.9%, 10), oxygenated monoterpenes (1.41%, 3), and hemiterpenes (0.04%, 1) some of which can probably contribute to the hop of Saaz variety aroma. Mass spectrometry analysis revealed that the main metabolites are the monoterpene β-myrcene (53.0 ± 1.1% of the total volatile fraction), and the cyclic sesquiterpenes, α-humulene (16.6 ± 0.8%), and β-caryophyllene (14.7 ± 0.4%), which together represent about 80% of the total volatile fraction from the hop-essential oil. These findings suggest that this matrix can be explored as a powerful biosource of terpenoid metabolites. 相似文献
173.
Aiying Rong José Rui Figueira Kathrin Klamroth 《Applied mathematics and computation》2012,218(12):6921-6933
The discounted {0-1} knapsack problem (DKP) is an extension of the classical {0-1} knapsack problem (KP) that consists of selecting a set of item groups where each group includes three items and at most one of the three items can be selected. The DKP is more challenging than the KP because four choices of items in an item group diversify the selection of the items. Consequently, it is not possible to solve the DKP based on a classical definition of a core consisting of a small number of relevant variables. This paper partitions the DKP into several easier sub-problems to achieve problem reductions by imitating the core concept of the KP to derive an alternative core for the DKP. Numerical experiments with DP-based algorithms are conducted to evaluate the effectiveness of the problem partition by solving the partitioned problem and the original problem based on different types of DKP instances. 相似文献
174.
Lidong Li Clara S. B. Gomes Cludia A. Figueira Pedro T. Gomes M. Teresa Duarte 《Acta Crystallographica. Section C, Structural Chemistry》2009,65(2):m110-m114
Two conformational polymorphs of trans‐chlorido(phenyl)bis(triphenylphosphine)nickel(II), [Ni(C6H5)Cl(C18H15P)2], (1), viz. orange needle‐shaped crystals (form I) and brown prism‐shaped crystals (form II), were obtained under different crystallization conditions from a mixture of toluene and n‐hexane, and characterized by single‐crystal X‐ray diffraction at low temperature. These two forms were compared with that published previously [Zeller, Herdtweck & Strassner (2003). Eur. J. Inorg. Chem. pp. 1802–1806], characterized at room temperature. Additionally, blue–green prisms of a 1:1 cocrystal of complex (1) with chloridobis(triphenylphosphine)nickel(I), (2), viz.trans‐chlorido(phenyl)bis(triphenylphosphine)nickel(II)–chloridobis(triphenylphosphine)nickel(I) (1/1), [Ni(C6H5)Cl(C18H15P)2]·[NiCl(C18H15P)2], (3), were obtained concomitantly with form I. In forms I and II, as well as in the cocrystal, the overall crystal packings are determined by an energetic interplay between intramolecular torsions and weak intermolecular C—H...π and C—H...Cl interactions. 相似文献
175.