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941.
Dr. Susanne Olsson Per Martin Björemark Dr. Theonitsa Kokoli Dr. Jonas Sundberg Dr. Anders Lennartson Prof. Christine J. McKenzie Prof. Mikael Håkansson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5211-5219
Three new conglomerates incorporating bidentate sulfide ligands coordinated by RuII centers have been prepared. Total spontaneous resolution by slow crystallization gives highly enantioenriched crystal batches, which are used in enantioselective oxidation of the sulfide ligands to give chiral sulfoxide complexes with >98 % ee. All relevant stereoisomers have been characterized by single‐crystal X‐ray diffraction, CD spectroscopy, and chiral HPLC. If the ligand range can be extended to monodentate sulfides, a large‐scale and recyclable process for enantioselective oxidation of sulfides can be designed. 相似文献
942.
Ola G. Grendal Inger-Emma Nylund Dr. Anders B. Blichfeld Dr. Satoshi Tominaka Dr. Koji Ohara Prof. Sverre M. Selbach Prof. Tor Grande Prof. Mari-Ann Einarsrud 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(42):9348-9355
Controlling the shape and size of nanostructured materials has been a topic of interest in the field of material science for decades. In this work, the ferroelectric material SrxBa1−xNb2O6 (x=0.32–0.82, SBN) was prepared by hydrothermal synthesis, and the morphology is controllably changed from cube-shaped to hollow-ended structures based on a fundamental understanding of the precursor chemistry. Synchrotron X-ray total scattering and PDF analysis was used to reveal the structure of the Nb-acid precursor, showing Lindqvist-like motifs. The changing growth mechanism, from layer-by-layer growth forming cubes to hopper-growth giving hollow-ended structures, is attributed to differences in supersaturation. Transmission electron microscopy revealed an inhomogeneous composition along the length of the hollow-ended particles, which is explained by preferential formation of the high entropy composition, SBN33, at the initial stages of particle nucleation and growth. 相似文献
943.
Magnus J. Johansson Anders Bergh Krister Larsson 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(5):o312-o314
A carbohydrate‐derived optically active P‐chiral dioxophenylphospholane–borane complex, C27H32BO6P, was prepared from bis(diethylamino)phenylphosphine and methyl 2,6‐di‐O‐benzyl‐β‐d ‐galactopyranoside. The phosphinite was prepared with high diastereoselectivity and in good yield. The absolute configuration (R) at the P atom was deduced from the known configuration of the sugar moiety. Weak intermolecular interactions link the molecules into a three‐dimensional network. 相似文献
944.
Background
Development of a functional retina depends on regulated differentiation of several types of neurons and generation of a highly complex network between the different types of neurons. In addition, each type of retinal neuron includes several distinct morphological types. Very little is known about the mechanisms responsible for generating this diversity of retinal neurons, which may also display specific patterns of regional distribution. 相似文献945.
Kinetic Monte Carlo methods provide a powerful computational tool for the simulation of microscopic processes such as the diffusion of interacting particles on a surface, at a detailed atomistic level. However such algorithms are typically computationatly expensive and are restricted to fairly small spatiotemporal scales. One approach towards overcoming this problem was the development of coarse-grained Monte Carlo algorithms. In recent literature, these methods were shown to be capable of efficiently describing much larger length scales while still incorporating information on microscopic interactions and fluctuations. In this paper, a coarse-grained Langevin system of stochastic differential equations as approximations of diffusion of interacting particles is derived, based on these earlier coarse-grained models. The authors demonstrate the asymptotic equivalence of transient and long time behavior of the Langevin approximation and the underlying microscopic process, using asymptotics methods such as large deviations for interacting particles systems, and furthermore, present corresponding numerical simulations, comparing statistical quantities like mean paths, auto correlations and power spectra of the microscopic and the approximating Langevin processes. Finally, it is shown that the Langevin approximations presented here are much more computationally efficient than conventional Kinetic Monte Carlo methods, since in addition to the reduction in the number of spatial degrees of freedom in coarse-grained Monte Carlo methods, the Langevin system of stochastic differential equations allows for multiple particle moves in a single timestep. 相似文献
946.
Erik Lindgren Henrik Shahgholian Anders Edquist 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2009
We study the regularity of the two-phase membrane problem, with coefficients below the Lipschitz threshold. For the Lipschitz coefficient case one can apply a monotonicity formula to prove the C1,1-regularity of the solution and that the free boundary is, near the so-called branching points, the union of two C1-graphs. In our case, the same monotonicity formula does not apply in the same way. In the absence of a monotonicity formula, we use a specific scaling argument combined with the classification of certain global solutions to obtain C1,1-estimates. Then we exploit some stability properties with respect to the coefficients to prove that the free boundary is the union of two Reifenberg vanishing sets near so-called branching points. 相似文献
947.
In this paper, we continue our study of 2-colorings in hypergraphs (see, Henning and Yeo, 2013). A hypergraph is 2-colorable if there is a 2-coloring of the vertices with no monochromatic hyperedge. It is known (see Thomassen, 1992) that every 4-uniform 4-regular hypergraph is 2-colorable. Our main result in this paper is a strengthening of this result. For this purpose, we define a vertex in a hypergraph to be a free vertex in if we can 2-color such that every hyperedge in contains vertices of both colors (where has no color). We prove that every 4-uniform 4-regular hypergraph has a free vertex. This proves a conjecture in Henning and Yeo (2015). Our proofs use a new result on not-all-equal 3-SAT which is also proved in this paper and is of interest in its own right. 相似文献
948.
Mette Krog Jensen Ole Hassager Henrik Koblitz Rasmussen Anne Ladegaard Skov Anders Bach Henning Koldbech 《Rheologica Acta》2010,49(1):1-13
A new test fixture for the filament stretch rheometer (FSR) has been developed to measure planar elongation of soft polymeric
networks with application towards pressure-sensitive adhesives (PSAs). The concept of this new geometry is to elongate a tube-like
sample by keeping the perimeter constant. To validate this new technique, soft polymeric networks of poly(propylene oxide)
(PPO) were investigated during deformation. Particle tracking and video recording were used to detect to what extent the imposed
strain rate and the sample perimeter remained constant. It was observed that, by using an appropriate choice of initial sample
height, perimeter, and thickness, the planar stretch ratio will follow l(t) = h(t)/h0 = exp([(e)\dot] t)\lambda(t) = h(t)/h_0= \exp({\dot{\varepsilon}} t), with h(t) being the height at time t and [(e)\dot]{\dot{\varepsilon}} the imposed constant strain rate. The perimeter would decrease by a few percent only, which is found to be negligible. The
ideal planar extension in this new fixture was confirmed by finite element simulations. Analysis of the stress difference,
σ
zz
− σ
xx
, showed a network response similar to that of the classical neo-Hookean model. As the Deborah number was increased, the stress
difference deviated more from the classical prediction due to the dynamic structures in the material. A modified Lodge model
using characteristic parameters from linear viscoelastic measurements gave very good stress predictions at all Deborah numbers
used in the quasi-linear regime. 相似文献
949.
Anders Lennartson Mikael Hkansson 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(3):m69-m74
Four complexes containing the [UO2(oda)2]2− anion (oda is oxydiacetate) are reported, namely dipyridinium dioxidobis(oxydiacetato)uranate(VI), (C5H6N)2[U(C4H4O5)2O2], (I), bis(2‐methylpyridinium) dioxidobis(oxydiacetato)uranate(VI), (C8H8N)2[U(C4H4O5)2O2], (II), bis(3‐methylpyridinium) dioxidobis(oxydiacetato)uranate(VI), (C8H8N)2[U(C4H4O5)2O2], (III), and bis(4‐methylpyridinium) dioxidobis(oxydiacetato)uranate(VI), (C8H8N)2[U(C4H4O5)2O2], (IV). The anions are achiral and are located on a mirror plane in (I) and on inversion centres in (II)–(IV). The four complexes are assembled into three‐dimensional structures via N—H...O and C—H...O interactions. Compounds (III) and (IV) are isomorphous; the [UO2(oda)2]2− anions form a porous matrix which is nearly identical in the two structures, and the cations are located in channels formed in this matrix. Compounds (I) and (II) are very different from (III) and (IV): (I) forms a layered structure, while (II) forms ribbons. 相似文献
950.
Anders Hammershi Magnus Schau‐Magnussen Jesper Bendix Anne Mlgaard 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(11):m319-m322
The structures of the diastereoisomers Λ(+)578‐, (I), and Δ(−)578‐bis(ethane‐1,2‐diamine)[β‐ethyl (S)‐aspartato‐κ2N,O1]cobalt(III) bis(perchlorate) monohydrate, (II), both [Co(C6H10N2O4)(C2H8N2)2](ClO4)2·H2O, are compared. In both structures, the ester group of the amino acid side chain is engaged only in intramolecular hydrogen bonding to coordinated amine groups. This interaction is stronger in (I) and correlates with previously observed diastereoisomeric equilibrium ratios for related metal complex systems in aqueous media. The two perchlorate anions of (II) are located on twofold axes. Both perchlorates in (I) and one of the perchlorates in (II) are affected by disorder. Both structures exhibit extensive three‐dimensional hydrogen‐bonding networks. 相似文献