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51.
Regioselectivity and stereoselectivity of nucleophilic addition to glycal and imino‐glycal vinyl epoxides and their carba analogs: a rationalization based on HSAB theory and MEP 下载免费PDF全文
52.
A Combined Experimental and Theoretical Study on the Formation of Ag Filaments on β‐Ag2MoO4 Induced by Electron Irradiation 下载免费PDF全文
Juan Andrés Mateus M. Ferrer Lourdes Gracia Armando Beltran Valeria M. Longo Guilherme H. Cruvinel Ricardo L. Tranquilin Elson Longo 《Particle & Particle Systems Characterization》2015,32(6):646-651
A combined experimental and theoretical study is presented to understand the novel observed nucleation and early evolution of Ag filaments on β‐Ag2MoO4 crystals, driven by an accelerated electron beam from an electronic microscope under high vacuum. The growth process, chemical composition, and the element distribution in these filaments are analyzed in depth at the nanoscale level using field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) with energy‐dispersive spectroscopy (EDS) characterization. To complement experimental results, chemical stability, structural and electronic aspects have been studied systematically using first‐principles electronic structure theory within a quantum theory of atoms in molecules (QTAIM) framework. The Ag nucleation and formation on β‐Ag2MoO4 are a result of structural and electronic changes of the AgO4 tetrahedral cluster as a constituent building block of β‐Ag2MoO4, consistent with Ag metallic formation. The formation of Ag filament transforms the β‐Ag2MoO4 semiconductor from n‐ to p‐type concomitant with the appearance of Ag defects. 相似文献
53.
Valeria Mantella Michal Strach Kilian Frank James R. Pankhurst Dragos Stoian Chethana Gadiyar Bert Nickel Raffaella Buonsanti 《Angewandte Chemie (International ed. in English)》2020,59(28):11627-11633
The classical nucleation theory (CNT) is the most common theoretical framework used to explain particle formation. However, nucleation is a complex process with reaction pathways which are often not covered by the CNT. Herein, we study the formation mechanism of copper nanospheres using in situ X‐ray absorption and scattering measurements. We reveal that their nucleation involves coordination polymer lamellae as pre‐nucleation structures occupying a local minimum in the reaction energy landscape. Having learned this, we achieved a superior monodispersity for Cu nanospheres of different sizes. This report exemplifies the importance of developing a more realistic picture of the mechanism involved in the formation of inorganic nanoparticles to develop a rational approach to their synthesis. 相似文献
54.
55.
Roberta Sanna Davide Sanna Valeria Alzari Daniele Nuvoli Sergio Scognamillo Massimo Piccinini Massimo Lazzari Emilia Gioffredi Giulio Malucelli Alberto Mariani 《Journal of polymer science. Part A, Polymer chemistry》2012,50(19):4110-4118
Thermoresponsive poly(N‐vinylcaprolactam) nanocomposite hydrogels containing graphene were successfully prepared by frontal polymerization. High concentration of graphene (5.0 mg/mL) was obtained by direct graphite sonication in the self‐same liquid monomer, thus avoiding any chemical manipulation and obtaining “real” graphene as nanofiller instead of one of its more or less oxidized derivative, which is what generally reported in published reports. Furthermore, the corresponding nanocomposites were obtained without using any solvent to be eventually removed. The materials were fully characterized by RAMAN, SEM, and TEM, and their swelling behavior and rheological properties were investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
56.
Carmen FestaSimona De Marino Valentina SepeMaria Valeria D’Auria Giuseppe BifulcoRosa Andrés Maria Carmen TerencioMiguel Payá Cécile DebitusAngela Zampella 《Tetrahedron》2011,67(40):7780-7786
Two new cyclopeptides, perthamides E and F were isolated from the polar extracts of the sponge Theonella swinhoei. The new structures, featuring an unprecedented β-amino acid unit (AHMOA), were determined by interpretation of NMR and MS data. The absolute configuration of the AHMOA residue was proposed on the basis of quantum chemical calculation of NMR chemical shifts. Perthamides were proved to inhibit TNF-α and IL-8 release in primary human keratinocytes cells and therefore could represent potentially leads for the treatment of psoriasis. 相似文献
57.
The cyclic chloronium or bromonium carboxylate obtained by addition of Cl+ or Br+ to acrylate anion is shown by PCM/B3LYP/6-31+G* calculations to be not an intermediate but a transition structure for interconversion of equivalent halomethyl oxiranones. 相似文献
58.
59.
Rafael O. Ruggiero 《Bulletin of the Brazilian Mathematical Society》1994,25(2):139-172
LetM be a compact Riemannian manifold with no conjugate points such that its geodesic flow is expansive. Then we show that the universal Riemannian covering ofM is a hyperbolic geodesic space according to the definition of M. Gromov. This allows us to extend a series of relevant geometric and topological properties of negatively curved manifolds toM and in particular, geometric group theory applies to the fundamental group ofM. 相似文献
60.
L?da Fontoura Costa G.?TraviesoEmail author C. A.?Ruggiero 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,44(1):119-128
This article investigates the functional properties of complex
networks used as grid computing systems. Complex networks following
the Erdös-Rényi model and other models with a preferential
attachment rule (with and without growth) or priority to the
connection of isolated nodes are studied. Regular networks are also
considered for comparison. The processing load of the parallel
program executed on the grid is assigned to the nodes on demand, and
the efficiency of the overall computation is quantified in terms of
the parallel speedup. It is found that networks with preferential
attachment allow lower computing efficiency than networks with
uniform link attachment. At the same time, considering only node
clusters of the same size, preferential attachment networks display
better efficiencies. The regular networks, on the other hand,
display a poor efficiency, due to their implied larger internode
distances. A correlation is observed between the topological
properties of the network, specially average cluster size, and their
respective computing efficiency. 相似文献