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41.
Badri?ToppurEmail author J.?MacGregor?Smith 《Journal of Mathematical Modelling and Algorithms》2005,4(2):199-217
Given a set V of size N≥4 vertices in a metric space, how can one interconnect them with the possible use of a set S of size M vertices not in the set V, but in the same metric space, so that the cumulative cost of the inter-connections between all the vertices is a minimum? When one uses the Euclidean metric to compute these inter-connections, this is referred to as the Euclidean Steiner Minimal Tree Problem. This is an NP-hard problem. The Steiner Ratio ρ of a vertex set is the length of this Steiner Minimal Tree (SMT), divided by the length of the Minimum Spanning Tree (MST), and is a popular and tractable measure of solution quality.The ?-Sausage heuristic described in this paper employs a decomposition technique to explore the point set. The fixed vertices of the set are connected to a set of centroid vertices of Delaunay tetrahedrons. The path topology is preserved as far as possible, together with a cycle prevention rule, where junctions, and deviations from the ?-Sausage structure occur. Furthermore, repeated sweeps, with different root vertices are accommodated.The computational complexity of the heuristic is shown to be O(N2). Experimental results with thousands of vertices are presented. Comparisons with an exponential running time Branch and Bound algorithm are also shown. 相似文献
42.
A study has been conducted of the feasibility of utilizing the sulfate reducing bacteriumDesulfovibrio desulfuricans and the chemoautotrophThiobacillus denitrificans as a basis of a microbial process for the removal of sulfur dioxide from a gas with net oxidation to sulfate. In reactors-in-series,
SO2 was reduced to H2S in the first stage by D.desulfuricans. The H2S was then stripped with nitrogen and sent to a second stage where it was oxidized to sulfate by T.denitrificans. A sulfur balance demonstrated complete reduction of SO2 to H2S in the first stage and complete oxidation of H2S to sulfate in the second stage. 相似文献
43.
Oxovanadium(IV) immobilized on Fe3O4@S‐ABEN is reported as a highly efficient nanocatalyst for the oxidation of sulfides and oxidative coupling of thiols (using H2O2 as green oxidant), the products of which are obtained in high to excellent yields. The products can be separated by a simple extraction with organic solvent and the catalyst is highly efficient, especially in terms of selectivity of desired product. The catalytic system can be recycled and reused without significant loss of catalytic activity. 相似文献
44.
Diorganotin (IV) complexes SnR2X2 (R = Me, Ph; X = Cl, NCS) form a series of versatile complexes when react with bidentate substituted pyridyl ligands. The reaction of dimethyltin dichloride with 5,5′‐dimethyl‐2,2′‐bipyridine (5,5′‐Me2bpy) resulted in the formation of [SnMe2Cl2(5,5′‐Me2bpy)] ( 1 ). Moreover, the reaction of SnMe2(NSC)2 with 4,4′‐di‐tert‐butyl‐2,2′‐bipyridine (bu2bpy), 1,10‐phenanthroline (phen) and 4,7‐diphenyl‐1,10‐phenanthroline (bphen) affords the hexa‐coordinated complexes [SnMe2(NCS)2(bu2bpy)] ( 2 ), [SnMe2(NCS)2(phen)] ( 3 ) and [SnMe2(NCS)2(bphen)] ( 4 ), respectively. The resulting complexes have been characterized using elemental analysis, IR, multinuclear NMR (1H, 13C, 119Sn) and DEPT‐135° NMR spectroscopy. On the other hand, the reaction of diphenyltin dichloride with 2,2′‐biquinoline (biq) and 4,7‐phenantroline (4,7‐phen) led to the formation of polymeric complexes of [SnPh2Cl2(4,7‐phen)]n ( 5 ) and [SnPh2Cl2(biq)]n ( 6 ). The NMR spectra, however, reveal the ligand lability in solution and suggest a coordination number of 5 . The X‐ray crystal structures of complexes [SnMe2Cl2(5,5′‐Me2bpy)] ( 1 ), [SnMe2(NCS)2(bu2bpy)] ( 2 ) and [SnMe2(NCS)2(bphen)] ( 4 ) have been determined which reveal that the geometry around the tin atom is distorted octahedral with trans‐[SnMe2] configuration. Interestingly, the crystal structure of (H2biq)2[SnPh2Cl4]?2CHCl3 ( 7 ) was characterized by X‐ray crystallography from a chloroform solution of [SnPh2Cl2(biq)]n ( 6 ) indicating the formation of doubly protonated [H2biq]+ and [Ph2SnCl4]2? which are stabilized by a network of hydrogen bonds with a feature of trans‐[SnPh2]. The 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping out of the intermolecular interactions for 1 , 2 , 4 and 7 which show the presence of π‐π and hydrogen bonding interactions which are associated between donor and acceptor atoms (N, S, Cl) in the solid state. 相似文献
45.
Russian Journal of Organic Chemistry - The application of yttrium iron garnet (YIG) superparamagnetic nanoparticles as a new recyclable and highly efficient heterogeneous magnetic catalyst for... 相似文献
46.
Rashid Badri Mohammad Reza Shushizadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):533-536
Abstract A new and mild method for oxybromination of aromatic compounds with CuBr 2 and K 2 Cr 2 O 7 in HOAC is reported. 相似文献
47.
Sterling F. Alfred Zoha M. Al‐Badri Ahmad E. Madkour Karen Lienkamp Gregory N. Tew 《Journal of polymer science. Part A, Polymer chemistry》2008,46(8):2640-2648
The synthesis of three different poly(ethylene oxide) macromonomers with a norbornene and oxanorbornene end group is presented. The macromonomers were polymerized to comb‐polymers by ring‐opening metathesis polymerization (ROMP) using Grubbs' Catalyst G3 to produce water soluble polymers with polydispersities between 1.04 and 1.30 and molecular weights between 14,000 and 50,000 g/mol. Characterization by static and dynamic light scattering reveals that the comb‐polymers with norbornene backbone are molecularly disperse in aqueous solution, while the oxanorbornene‐backbone polymers form small water‐soluble aggregates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2640–2648, 2008 相似文献
48.
The hot working behavior of VCN200 medium carbon low alloy steel was analyzed by performing hot compression tests in temperature range of 850–1150 °C and at strain rates of 0.001–1 s−1. Flow curves were typical of dynamic recrystallization during hot working over temperature range of 900–1150 °C and strain rates of 0.001–1 s−1. However, at lower temperatures no indication of flow softening was observed. The constitutive analysis using the hyperbolic sine function was performed and the value of apparent activation energy for the hot deformation determined to be about 435 kJ/mol. The flow curves up to the peak were successfully modeled using a dynamic recovery model. All the factors in this model were defined in terms of the Zener–Hollomon parameter. A modified form of Avrami equation was used to estimate the fractional softening due to the dynamic recrystallization for any given strain in flow curve. Using this model, the flow curves were successfully predicted and generalized to different deformation conditions. 相似文献
49.
Diethyl (E)-α-triphenylstannyl or (Z)-α-tri-n-butylstannyl α-alkenylphosphonates are conveniently and stereoselectively prepared using a “tin-Peterson-like” reaction. Protonolysis of the carbon-tin bond of α-tributylstannyl derivatives proved to be easy and stereospecific. 相似文献
50.
Rashid Badri Maryam Gorjizadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):544-549
An efficient and convenient synthesis of 1,3,4-oxadiazoles from aromatic aldehydes, acyl hydrazide, and 1,4- bis(triphenylphosphonium)-2-butene peroxodisulfate is reported. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. 相似文献