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941.
Simple syntheses of diverse bicyclo[3.3.1]nonanes and related compounds as the minimal substructure of bioactive natural products via Michael, aldol, and alkylation reactions from diketones are described herein. The structures of the synthesized compounds were determined by infrared spectroscopy, NMR (1H and 13C), and electrospray ionization–high-resolution mass spectrometry. We also show the in vitro antimicrobial activity against Gram-positive and Gram-negative bacteria. The qualitative analysis has revealed that the new synthesized compounds 5, 6, 9, and 11 present antibacterial properties. 相似文献
942.
943.
Nathan A. Mara Justin Crapps Thomas A. Wynn Kester D. Clarke Antonia Antoniou Patricia O. Dickerson 《哲学杂志》2013,93(21):2749-2758
Abstract We report on the strength of Al–Al interfaces and the effects of chemical segregation and interfacial void formation on bond strength using microcantilever bend testing. Interfaces are synthesised via hot isostatic pressing. Microcantilevers of several nominal dimensions were fabricated via focused ion beam and deformed in a nanoindenter. We find increased cantilever strength as a function of decreasing sample size, with a linear dependence of the yield strength on the inverse square root of the length scale characteristic to the cantilever cross-section. The presence of pores and chemical segregation decreases the yield strength of the material by 17% and the accommodated strain energy by 10–15% for strain values in the 6–12% range. 相似文献
944.
945.
Each year an estimated 5 to 10 million tons of oil are discharged into the oceans of the world. Eighty percent of this spilled oil remains in the environment, directly poisoning marine life and indirectly threatening the rest of the plant and animal environment. 相似文献
946.
947.
948.
Meta M. Bloksma Sarah Rogers Ulrich S. Schubert Richard Hoogenboom 《Journal of polymer science. Part A, Polymer chemistry》2011,49(13):2790-2801
The synthesis and microwave‐assisted polymerization of a series of chiral 2‐oxazolines with varying alkyl pendant groups, namely R‐2‐ethyl‐4‐ethyl‐2‐oxazoline (R‐EtEtOx), R‐2‐butyl‐4‐ethyl‐2‐oxazoline (R‐BuEtOx), R‐2‐octyl‐4‐ethyl‐2‐oxazoline, 2‐nonyl‐4‐ethyl‐2‐oxazoline, and R‐2‐undecyl‐4‐ethyl‐2‐oxazoline (R‐UndeEtOx), are reported. A kinetic investigation of the polymerization of R‐EtEtOx revealed a living polymerization mechanism. The poly(2‐oxazoline)s containing an ethyl, butyl, and octyl pendant group form similar chiral structures according to circular dichroism measurements. When the pendant group is further elongated, the chiral structure becomes more flexible in trifluoroethanol and the thermal response in hexafluoroisopropanol (HFIP) significantly changes. The short‐range structure of poly‐R‐BuEtOx dissolved in HFIP is thermoresponsive in a complex way, due to HFIP hydrogen bonding to the polymeric amide groups, whereas the long‐range structure determined from small angle neutron scattering is insensitive to temperature demonstrating that only the local secondary structure changes with temperature. In addition, the chiral structure of poly‐R‐UndeEtOx depends on the polarity of the solvent. The short‐range structure becomes more flexible in polar solvents, most likely due to interactions with the amide groups disturbing the secondary structure. In contrast, the long‐range structural transition from an ellipsoid in the apolar n‐hexane to a rod structure in the polar n‐butanol is ascribed to better solvation of the long aliphatic side chains. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
949.
Florian Schlütter Georges M. Pavlov Jean‐François Gohy Andreas Winter Andreas Wild Martin D. Hager Stephanie Hoeppener Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2011,49(6):1396-1408
A series of RuII heterodinuclear complexes of ABA ‐type with electron‐deficient bis‐terpyridines as building blocks was synthesized by (R‐tpy)RuIIICl3 complexation. These compounds were characterized by NMR spectroscopy, MALDI‐TOF, ESI‐TOF mass spectrometry, and elemental analysis. The results were compared with a coil‐rod‐coil RuII metallo‐supramolecular copolymer, which was synthesized by bis‐complex formation between a hydrophilic ω‐terpyridine poly(ethylene glycol) RuII mono‐complex and a hydrophobic bis‐terpyridine‐functionalized rigid core. This amphiphilic RuII triblock copolymer showed self‐assembly to clusters and micelles in aqueous solution, which was studied by transmission electron microscopy and dynamic light scattering. Applying velocity sedimentation experiments the number of amphiphilic RuII ABA triblock copolymer molecules within the micelles could be estimated. Finally, the photophysical properties of the RuII supramolecular assemblies were investigated by UV–vis spectroscopy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
950.