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41.
42.
Costa AM Jimeno C Gavenonis J Carroll PJ Walsh PJ 《Journal of the American Chemical Society》2002,124(24):6929-6941
The optimization of asymmetric catalysts for enantioselective synthesis has conventionally revolved around the synthesis and screening of enantiopure ligands. In contrast, we have optimized an asymmetric reaction by modification of a series of achiral ligands. Thus, employing (S)-3,3'-diphenyl BINOL [(S)-Ph(2)-BINOL] and a series of achiral diimine and diamine activators in the asymmetric addition of alkyl groups to benzaldehyde, we have observed enantiomeric excesses between 96% (R) and 75% (S) of 1-phenyl-1-propanol. Some of the ligands examined have low-energy chiral conformations that can contribute to the chiral environment of the catalyst. These include achiral diimine ligands with meso backbones that adopt chiral conformations, achiral diimine ligands with backbones that become axially chiral on coordination to metal centers, achiral diamine ligands that form stereocenters on coordination to metal centers, and achiral diamine ligands with pendant groups that have axially chiral conformations. Additionally, we have structurally characterized (Ph(2)-BINOLate)Zn(diimine) and (Ph(2)-BINOLate)Zn(diamine) complexes and studied their solution behavior. 相似文献
43.
R. Lalrempuia Patrick J. Carroll K.A. Kreisel 《Journal of organometallic chemistry》2005,690(17):3990-3996
The reactions of [(ind)Ru(PPh3)2CN] (ind = η5-C9H7) (1) and [CpRu(PPh3)2CN] (Cp = η5-C5H5) (2) with [(η6-p-cymene)Ru(bipy)Cl]Cl (bipy = 2,2′-bipyridine) (3) in the presence of AgNO3/NH4BF4 in methanol, respectively, yielded dicationic cyano-bridged complexes of the type [(ind)(PPh3)2Ru(μ-CN)Ru(bipy)(η6-p-cymene)](BF4)2 (4) and [Cp(PPh3)2Ru(μ-CN)Ru(bipy)(η6-p-cymene)](BF4)2 (5). The reaction of [CpRu(PPh3)2CN] (2), [CpOs(PPh3)2CN] (6) and [CpRu(dppe)CN] (7) with the corresponding halide complexes and [(η6-p-cymene)RuCl2]2 formed the monocationic cyano-bridge complexes [Cp(PPh3)2Ru(μ-CN)Os(PPh3)2Cp](BF4) (8), [Cp(PPh3)2Os(μ- CN)Ru(PPh3)2Cp](BF4) (9) and [Cp(dppe)Ru(μ-CN)Os(PPh3)2Cp](BF4) (10) along with the neutral complexes [Cp(PPh3)2Ru(μ-CN)Ru (η6-p-cymene)Cl2] (11), [Cp(PPh3)2Os(μ-CN)Ru(η6-p-cymene)Cl2] (12), and [Cp(dppe) Ru(μ-CN)Ru(η6-p-cymene)Cl2] (13). These complexes were characterized by FT IR, 1H NMR, 31P{1H} NMR spectroscopy and the molecular structures of complexes 4, 8 and 11 were solved by X-ray diffraction studies. 相似文献
44.
Daewon Hong Patrick J. Carroll Larry G. Sneddon 《Journal of organometallic chemistry》2003,680(1-2):61-65
The new 11-vertex nido-diphosphaborane, 7,9-Ph2-nido-7,9-P2B9H9, has been synthesized by the reaction of Me4N+[nido-B9H12−] with PhPCl2 in the presence of NaH. A single crystal X-ray diffraction determination and DFT/GIAO/NMR methods have both established that the compound has an open cage structure containing the phosphorus atoms in non-adjacent positions on the open face. 相似文献
45.
Dioumaev VK Procopio LJ Carroll PJ Berry DH 《Journal of the American Chemical Society》2003,125(26):8043-8058
A series of octahedral ruthenium silyl hydride complexes, cis-(PMe(3))(4)Ru(SiR(3))H (SiR(3) = SiMe(3), 1a; SiMe(2)CH(2)SiMe(3), 1b; SiEt(3), 1c; SiMe(2)H, 1d), has been synthesized by the reaction of hydrosilanes with (PMe(3))(3)Ru(eta(2)-CH(2)PMe(2))H (5), cis-(PMe(3))(4)RuMe(2) (6), or (PMe(3))(4)RuH(2) (9). Reaction with 6 proceeds via an intermediate product, cis-(PMe(3))(4)Ru(SiR(3))Me (SiR(3) = SiMe(3), 7a; SiMe(2)CH(2)SiMe(3), 7b). Alternatively, 1 and 7 have been synthesized via a fast hydrosilane exchange with another cis-(PMe(3))(4)Ru(SiR(3))H or cis-(PMe(3))(4)Ru(SiR(3))Me, which occurs at a rate approaching the NMR time scale. Compounds 1a, 1b, 1d, and 7a adopt octahedral geometries in solution and the solid state with mutually cis silyl and hydride (or silyl and methyl) ligands. The longest Ru-P distance within a complex is always trans to Si, reflecting the strong trans influence of silicon. The aptitude of phosphine dissociation in these complexes has been probed in reactions of 1a, 1c, and 7a with PMe(3)-d(9) and CO. The dissociation is regioselective in the position trans to a silyl ligand (trans effect of Si), and the rate approaches the NMR time scale. A slower secondary process introduces PMe(3)-d(9) and CO in the other octahedral positions, most likely via nondissociative isomerization. The trans effect and trans influence in 7a are so strong that an equilibrium concentration of dissociated phosphine is detectable (approximately 5%) in solution of pure 7a. Compounds 1a-c also react with dihydrogen via regioselective dissociation of phosphine from the site trans to Si, but the final product, fac-(PMe(3))(3)Ru(SiR(3))H(3) (SiR(3) = SiMe(3), 4a; SiMe(2)CH(2)SiMe(3), 4b; SiEt(3), 4c), features hydrides cis to Si. Alternatively, 4a-c have been synthesized by photolysis of (PMe(3))(4)RuH(2) in the presence of a hydrosilane or by exchange of fac-(PMe(3))(3)Ru(SiR(3))H(3) with another HSiR(3). The reverse manifold - HH elimination from 4a and trapping with PMe(3) or PMe(3)-d(9) - is also regioselective (1a-d(9)() is predominantly produced with PMe(3)-d(9) trans to Si), but is very unfavorable. At 70 degrees C, a slower but irreversible SiH elimination also occurs and furnishes (PMe(3))(4)RuH(2). The structure of 4a exhibits a tetrahedral P(3)Si environment around the metal with the three hydrides adjacent to silicon and capping the P(2)Si faces. Although strong Si...HRu interactions are not indicated in the structure or by IR, the HSi distances (2.13-2.23(5) A) suggest some degree of nonclassical SiH bonding in the H(3)SiR(3) fragment. Thermolysis of 1a in C(6)D(6) at 45-55 degrees C leads to an intermolecular CD activation of C(6)D(6). Extensive H/D exchange into the hydride, SiMe(3), and PMe(3) ligands is observed, followed by much slower formation of cis-(PMe(3))(4)Ru(D)(Ph-d(5)). In an even slower intramolecular CH activation process, (PMe(3))(3)Ru(eta(2)-CH(2)PMe(2))H (5) is also produced. The structure of intermediates, mechanisms, and aptitudes for PMe(3) dissociation and addition/elimination of H-H, Si-H, C-Si, and C-H bonds in these systems are discussed with a special emphasis on the trans effect and trans influence of silicon and ramifications for SiC coupling catalysis. 相似文献
46.
Lauber WM Carroll JA Dufield DR Kiesel JR Radabaugh MR Malone JP 《Electrophoresis》2001,22(5):906-918
As proteomic technology evolves, protein staining sensitivity is constantly being improved, enabling researchers to better visualize the proteome of their system. The current challenge is to balance the limits of detection of protein visualization with those of the mass spectrometric methods. In this report, mass spectra generated from human serum or rat liver proteins stained with either colloidal Coomassie blue, Daiichi silver, SYPRO Orange, SYPRO Red, SYPRO Ruby, or SYPRO Tangerine are compared. It has been concluded that the newest generation of fluorescent protein stains, compared with traditional staining methods, are more compatible to matrix-assisted laser desorption/ionization (MALDI) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. The number of database matches obtained using each mass spectrometry method and the percent sequence coverage obtained from trypsin digested proteins stained using these six methods is provided. 相似文献
47.
[reaction: see text] The hydroxy-directed reduction of 1,2-dehydropiperidines with the "ate" complex of DIBAL-H and n-BuLi affords functionalized trans-2,6-disubstituted piperidines. This methodology was employed in the asymmetric synthesis of the quinolizidine alkaloid (-)-lasubine I. 相似文献
48.
Boyd AS Carroll JB Cooke G Garety JF Jordan BJ Mabruk S Rosair G Rotello VM 《Chemical communications (Cambridge, England)》2005,(19):2468-2470
We report the electrochemically tuneable intramolecular hydrogen bonding interactions between a covalently linked flavin-diamidopyridine unit. 相似文献
49.
Kim K Webster S Levi N Carroll DL Pinto MR Schanze KS 《Langmuir : the ACS journal of surfaces and colloids》2005,21(11):5207-5211
We describe the preparation and characterization of a photonic crystal filled with a luminescent conjugated polyelectrolyte, sulfonated poly(phenylene ethynylene). The conjugated polymer was coated onto the nanospheres by the layer-by-layer method and assembled directly into a fluorescent opal structure avoiding the defects associated with post-filling schemes. These structures exhibit strong angle-dependent luminescent properties. By using multiple layers, we further demonstrate control over the emissive bands of the opal. 相似文献
50.
W.E. Carroll D. Condon M.E. Deane F.J. Lalor 《Journal of organometallic chemistry》1978,157(4):C58-C60
Complexes of the type [(C5H5)Mo(N2Ar)(N2Ar′)(PPh3)] [PF6] have been prepared and shown to be useful starting materials for the synthesis of a variety of neutral, cationic or anionic compounds containing [cis-Mo(N2Ar)(N2Ar′)]2+ units. 相似文献