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991.
Two new water-soluble [IrI(2)(AcO)(bis-NHC)] complexes (NHC=N-heterocyclic carbene) incorporating a sulfonate functionality have been synthesized. The two complexes have been tested in the reduction of CO(2) with H(2) and iPrOH, and their activity has been compared with similar species without the sulfonate moiety. In both reactions, the complex with the two abnormally bound NHCs shows the best catalytic efficiencies, due to the higher σ-electron-donor character of the ligand. Remarkably, the activities obtained for the reduction of CO(2) under the transfer hydrogenation conditions are the best reported to date in terms of TON value (max. TON=2700). The two new complexes have also shown very good activity in the selective deuteration of arylamines, a process that is known to proceed through a chelate assisted N-directed process. 相似文献
992.
993.
Ruano JL Alvarado C Díaz-Tendero S Alemán J 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(14):4030-4037
The use of β-ketosulfoxides as nucleophiles in reactions with α,β-unsaturated aldehydes catalyzed by proline derivatives allows complete control of configuration at the two chiral centers that are created during 1,4-addition reactions. The sulfinyl group can be used to create additional chiral centers in the resulting compounds and then removed while preserving the chirality of the carbon joined to the sulfur. The catalyst and the sulfinyl group are mainly responsible for the configurational control of the carbon atoms acting as electrophile and nucleophile, respectively, which allows the preparation of the four possible diastereoisomers in optically pure form. Theoretical calculations of the possible chiral nucleophilic species bearing diastereotopic faces allow us to postulate, for the first time, that enolates, instead of enols, are the active reagents in these reactions. 相似文献
994.
Daniel Leite da Silva Eder do Couto Tavares Leila de Souza Conegero ?ngelo de F??tima Ronaldo Aloise Pilli Sergio Antonio Fernandes 《Journal of inclusion phenomena and macrocyclic chemistry》2011,69(1-2):149-155
Accidental or intentional drug toxicity in humans and animals is a major concern and the search for detoxificant agents is a challenge. Pyrrolizidine-producing forages are a threat not only to livestock, but also to humans as a consequence of food contamination. Supramolecular systems are promising as detoxificant agents by decreasing the bioavailability of toxic compounds in biological environment. Cyclodextrin and calix[n]arenes are well known hosts for a variety of molecules and/or ions. Surprisingly, only few studies describe the potential of calix[n]arenes as host for toxic molecules. This study focused on the use of NMR techniques as tools for the investigation of the interactions between p-sulfonic acid calix[6]arene and retronecine, a toxic pyrrolizidine alkaloid. 相似文献
995.
Stephanie M. Taylor Dr. Sergio Sanz Dr. Ruaraidh D. McIntosh Dr. Christine M. Beavers Dr. Simon J. Teat Prof. Euan K. Brechin Dr. Scott J. Dalgarno 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(50):16014-16022
p‐tert‐Butylcalix[4]arene is a bowl‐shaped molecule capable of forming a range of polynuclear metal clusters under different experimental conditions. p‐tert‐Butylcalix[8]arene (TBC[8]) is a significantly more flexible analogue that has previously been shown to form mono‐ and binuclear lanthanide (Ln) metal complexes. The latter (cluster) motif is commonly observed and involves the calixarene adopting a near double‐cone conformation, features of which suggested that it may be exploited as a type of assembly node in the formation of larger polynuclear lanthanide clusters. Variation in the experimental conditions employed for this system provides access to Ln1, Ln2, Ln4, Ln5, Ln6, Ln7 and Ln8 complexes, with all polymetallic clusters containing the common binuclear lanthanide fragment. Closer inspection of the structures of the polymetallic clusters reveals that all but one (Ln8) are in fact based on metal octahedra or the building blocks of octahedra, with the identity and size of the final product dependent upon the basicity of the solution and the deprotonation level of the TBC[8] ligand. This demonstrates both the versatility of the ligand towards incorporation of additional metal centres, and the associated implications for tailoring the magnetic properties of the resulting assemblies in which lanthanide centres may be interchanged. 相似文献
996.
Sergio Enrique Moya Jagoba Jon Iturri Ramos Irantzu Llarena 《Macromolecular rapid communications》2012,33(12):1022-1035
This feature article deals with the self assembly and physical chemistry of polyelectrolytes: multilayers and brushes. The article highlights the interesting behavior of polyelectrolytes in nanoscale assemblies, giving more insight into the complexity of the formation of the assemblies. The water content of multilayers and brushes is studied during the assembly and in different ionic strengths. Similarities are found in the behavior of the brushes and multilayers with ionic strength, with regard to changes in the thickness and the water content. An invariance of the zeta potential with ionic strength is also observed for both systems, which can be explained as a result of conformational changes of the polymer chains. Finally, the combination of brushes and multilayers for surface modification is presented. 相似文献
997.
André L. Bogado Rose M. Carlos Cristina Daólio Antonio G. Ferreira Miguel G. Neumann Frank Rominger Sergio P. Machado Juliana P. da Silva Márcio P. de Araujo Alzir A. Batista 《Journal of organometallic chemistry》2012,696(26):4184-4190
The mixed ruthenium(II) complexes trans-[RuCl2(PPh3)2(bipy)] (1), trans-[RuCl2(PPh3)2(Me2bipy)](2), cis-[RuCl2(dcype)(bipy)](3), cis-[RuCl2(dcype)(Me2bipy)](4) (PPh3 = triphenylphosphine, dcype = 1,2-bis(dicyclohexylphosphino)ethane, bipy = 2,2′-bipyridine, Me2bipy = 4,4′-dimethyl-2,2′-bipyridine) were used as precursors to synthesize the associated vinylidene complexes. The complexes [RuCl(CCHPh)(PPh3)2(bipy)]PF6 (5), [RuCl(CCHPh)(PPh3)2(Me2bipy)]PF6 (6), [RuCl(CCHPh)(dcype)(bipy)]PF6 (7), [RuCl(CCHPh)(dcype)(bipy)]PF6 (8) were characterized and their spectral, electrochemical, photochemical and photophysical properties were examined. The emission assigned to the π–π1 excited state from the vinylidene ligand is irradiation wavelength (340, 400, 430 nm) and solvent (CH2Cl2, CH3CN, EtOH/MeOH) dependent. The cyclic voltammograms of (6) and (7) show a reversible metal oxidation peak and two successive ligand reductions in the +1.5-(?0.64) V range. The reduction of the vinylidene leads to the formation of the acetylide complex, but due the hydrogen abstraction the process is irreversible. The studies described here suggest that for practical applications such as functional materials, nonlinear optics, building blocks and supramolecular photochemistry. 相似文献
998.
Li XG Dall'Angelo S Schweiger LF Zanda M O'Hagan D 《Chemical communications (Cambridge, England)》2012,48(43):5247-5249
[(18)F]-5-Fluoro-5-deoxyribose ([(18)F]-FDR) conjugates much more rapidly than [(18)F]-FDG under mild reaction conditions to peptides and offers new prospects for mild and rapid bioconjugation for fluorine-18 labelling in PET imaging. 相似文献
999.
A Maggio S Rosselli M Bruno V Spadaro FM Raimondo F Senatore 《Molecules (Basel, Switzerland)》2012,17(9):10232-10241
The use of essential oils as chemotaxonomic markers could be useful for the classification of Artemisia species and to caracterize biodiversity in the different populations. An analysis of the chemical composition of four essential oils from Italian populations of Artemisia alba Turra (collected in Sicily, Marche and Abruzzo) was investigated. In this paper an in depth study of the significant differences observed in the composition of these oils is reported. 相似文献
1000.
S Rosselli M Bruno FM Raimondo V Spadaro M Varol AT Koparal A Maggio 《Molecules (Basel, Switzerland)》2012,17(7):8186-8195
A phytochemical analysis of the dichloromethane extract from the flowers of a subspecies of Tanacetum vulgare growing in Sicily was carried out. Five known sesquiterpene lactones with the eudesmane skeleton have been isolated and the cytotoxic activity of these compounds was tested in vitro on A549 (human lung carcinoma epithelial-like) and V79379A (Chinese hamster lung fibroblast-like) cells using the tetrazolium salt reduction (MTT) assay. All of tested compounds induced high time- and concentration-dependent cytotoxic effects. 相似文献