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131.
The polarization current due to a magnetic island rotating in a tokamak plasma is believed to play a central role in the initial evolution of the neoclassical tearing mode. Monte Carlo delta f simulations are performed which also cover a parameter range that is not amenable to analytic treatment but is relevant to experiments. It is shown that the polarization current can change sign when the island rotation frequency is of the order of the ion parallel streaming around the island. Moreover, the current is reduced when the island width is of the order of the ion banana width. Finally, the transition to the enhanced high-collisionality regime is shown to occur for collision frequencies higher than those typical of today's experiments. 相似文献
132.
Andrei CM Walmsley JC Brinks HW Holmestad R Blanchard D Hauback BC Botton GA 《The journal of physical chemistry. B》2005,109(10):4350-4356
The microstructure of LiAlD(4) with TiCl(3).1/3(AlCl(3)) and VCl(3) additives has been studied during different steps of the decomposition process using electron energy loss spectroscopy and energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope. Energy filtered transmission electron microscopy was used to show elemental distributions in the samples. The spatial distribution of the additives and the main elements within the alanate particles was examined with a resolution of a few nanometers. The analysis of the electron energy loss spectra reveals the chemical state of Al, O, and the additives. Ti and V do not appear to mix chemically with Al to a significant degree. V was found in high concentration in just a few particles, while Ti is more uniformly distributed. All the samples showed evidence of oxidation despite procedures being adopted to avoid exposing the material to air. The additives are oxidized in all the samples, and Al(2)O(3) forms a thin layer at the surface of the particles. This paper gives a comparison between samples at different stages of the decomposition process using different additives. 相似文献
133.
Serafini M Corazzi G Poli F Piccin A Tomassini L Foddai S 《Natural product research》2005,19(6):547-550
We studied the occurrence of phenylpropanoid glycosides (PhG) in five species of the genus Orobanche L., collected in the Latium region of Italy. The presence of orobanchoside and verbascoside in all four species confirms that these PhGs are taxonomic markers of the genus. The results suggest that O. gracilis form. citrina could be a diverse entity. 相似文献
134.
Bianco A Guiso M Nicoletti M Foddai S Piccin A Serafini M Ballero M Poli F 《Natural product research》2005,19(6):615-617
The phytochemical analysis of iridoidic fraction of the aerial parts of Vinca sardoa and Vinca difformis, gave the identification of loganic acid in V. difformis as unique iridoid glucoside, while loganin is also present in V. sardoa. The two taxa highly differ in alkaloids, so the chemotaxonomic classification in two different species is supported. 相似文献
135.
A new solution of the Einstein-Yang-Mills system with axial symmetry and cosmological constant is given here. This new metric, which in the absence of matter becomes the de Sitter universe, is the natural generalization of both a recent result of Perry for stellar (asymptotically flat) black holes and a well-knwn family of solutions of the Einstein-Maxwell system with nonvanishing cosmological constant given some time ago by Carter. Calculations have been carried out making extensive use of the coordinates found by Plebanski. 相似文献
136.
137.
Bock C Paquet C Couillard M Botton GA MacDougall BR 《Journal of the American Chemical Society》2004,126(25):8028-8037
A rapid synthesis method for the preparation of PtRu colloids and their subsequent deposition on high surface area carbons is presented. The reaction mechanism is shown to involve the oxidation of the solvent, ethylene glycol, to mainly glycolic acid or, depending on the pH, its anion, glycolate, while the Pt(+IV) and Ru(+III) precursor salts are reduced. Glycolate acts as a stabilizer for the PtRu colloids and the glycolate concentration, and hence the size of the resulting noble metal colloids is controlled via the pH of the synthesis solution. Carbon-supported PtRu catalysts of controlled size can be prepared within the range of 0.7-4 nm. Slow scan X-ray diffraction and high-resolution transmission electron microscopy show the PtRu catalysts to be crystalline. The Ru is partly dissolved in the face-centered cubic Pt lattice, but the catalysts also consist of a separate, hexagonal Ru phase. The PtRu catalysts appear to be of the same composition independent of the catalyst size in the range of 1.2-4 nm. Particular PtRu catalysts prepared in this work display enhanced activities for the CH(3)OH electro-oxidation reaction when compared to two commercial catalysts. 相似文献
138.
G. de Angelis T. Martinez A. Gadea N. Marginean E. Farnea E. Maglione S. Lenzi W. Gelletly C.A. Ur D.R. Napoli Th. Kroell S. Lunardi B. Rubio M. Axiotis D. Bazzacco A.M. Bizzeti Sona P.G. Bizzeti P. Bednarczyk A. Bracco F. Brandolini F. Camera D. Curien M. De Poli O. Dorvaux J. Eberth H. Grawe R. Menegazzo G. Nardelli J. Nyberg P. Pavan B. Quintana C. Rossi Alvarez P. Spolaore T. Steinhart I. Stefanescu O. Thelen R. Venturelli 《The European Physical Journal A - Hadrons and Nuclei》2001,12(1):51-55
Gamma ray transitions de-exciting states in the N = Z nucleus 70Br have been identified for the first time using the GASP and EUROBALL arrays coupled with ancillary detectors. The level
scheme of 70Br has been established by means of particle-gated γ-γ and γ-γ-γ coincidences. The Coulomb energy differences between isobaric
analogue states in 70Br and 70Se show a deviation from the expected behaviour which could be related to dripline effects.
Received: 18 July 2001 / Accepted: 25 September 2001 相似文献
139.
Hui Wang Lorenzo Vendrame Dr. Christophe Fliedel Dr. Si Chen Dr. Florence Gayet Dr. Franck D'Agosto Dr. Muriel Lansalot Dr. Eric Manoury Prof. Rinaldo Poli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5205-5214
Unimolecular amphiphilic nanoreactors with a poly(4-vinyl-N-methylpyridinium iodide) (P4VPMe+I−) polycationic outer shell and two different architectures (core-cross-linked micelles, CCM, and nanogels, NG), with narrow size distributions around 130–150 nm in diameter, were synthesized by RAFT polymerization from an R0-4VPMe+I−140-b-S50-SC(S)SPr macroRAFT agent by either chain extension with a long (300 monomer units) hydrophobic polystyrene-based block followed by cross-linking with diethylene glycol dimethacrylate (DEGDMA) for the CCM particles, or by simultaneous chain extension and cross-linking for the NG particles. A core-anchored triphenylphosphine (TPP) ligand functionality was introduced by using 4-diphenylphosphinostyrene (DPPS) as a comonomer (5–20 % mol mol−1) in the chain extension (for CCM) or chain extension/cross-linking (for NG) step. The products were directly obtained as stable colloidal dispersions in water (latexes). After loading with [RhCl(COD)]2 to yield [RhCl(COD)(TPP@CCM)] or [RhCl(COD)(TPP@NG)], respectively, the polymers were used as polymeric nanoreactors in Rh-catalyzed aqueous biphasic hydrogenation of the model substrates styrene and 1-octene, either neat (for styrene) or in an organic solvent (toluene or 1-nonanol). All hydrogenations were rapid (TOF up to 300 h−1) at 25 °C and 20 bar of H2 pressure, the biphasic mixture rapidly decanted at the end of the reaction (<2 min), the Rh loss was negligible (<0.1 ppm in the recovered organic phase), and the catalyst phase could be recycled 10 times without significant loss of catalytic activity. 相似文献
140.