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931.
A modular synthetic approach was developed to access triamines with varying tether lengths from commercially available aminoalkanols. Initial N-alkylation via reductive amination with anthracene-9-carbaldehyde provided the secondary amines in good yield. Subsequent ditosylation with excess TsCl yielded the respective bis-N,O-tosylates. The tosylates were reacted with excess putrescine to give the final triamines. X-ray crystallography revealed that the polyamine tail is preferentially oriented over the shielding cone of the anthracene ring. 相似文献
932.
Karren D. Beattie Dion R. ThompsonEvelin Tiralongo David RatkowskyTom W. May Melvyn Gill 《Tetrahedron letters》2011,52(42):5448-5451
The yellow dihydroanthracenone dimer, austrocolorin B1 and the unique violet-red 1,4-anthraquinone dimer, austrocolorone B, were isolated from the Tasmanian mushroom Cortinariusvinosipes and their structures and stereochemistry were determined from spectroscopic data. Austrocolorin B1 and austrocolorone B were found to exhibit potent cytotoxic activity in vitro against the murine lymphoblast (P388D1) cell line with IC50 values in the range 10-31 μg/mL. 相似文献
933.
Juraj ernk Khalil A. Abboud 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(3):m167-m170
Partial reduction of the CuII ions in the aqueous system CuII–en–[Ni(CN)4]2? (1/1/1) (en is 1,2‐diaminoethane) yields a novel heterobimetallic mixed‐valence compound, poly[[aquabis(1,2‐diaminoethane)copper(II)] [hexa‐μ‐cyano‐tetracyanobis(1,2‐diaminoethane)tricopper(I,II)dinickel(II)] dihydrate], [Cu(C2H8N2)2(H2O)][Ni2Cu3(CN)10(C2H8N2)2]·2H2O or [Cu(en)2(H2O)][Cu(en)2Ni2Cu2(CN)10]·2H2O. The structure is formed by a negatively charged two‐dimensional array of the cyano complex [Cu(en)2Ni2Cu2(CN)10]n2n?, [Cu(en)2(H2O)]2+ complex cations and water molecules of crystallization. These last are involved in a complicated hydrogen‐bonding system. The cyano groups act as terminal, μ2‐bridging or μ3‐bridging ligands. 相似文献
934.
935.
Arthur J. Banister Iain May Jeremy M. Rawson J.Nicholas B. Smith 《Journal of organometallic chemistry》1998,550(1-2)
The ability of heterocyclic compounds to act as chelating ligands via the cleavage of a heterocyclic E–E (or E–E′) bond with concomitant formation of M–E (and M–E′) bonds is described with particular reference to the 7π heterocyclic dithiadiazolyl radicals, R
. These electron-rich ring systems form a diversity of structural bonding types in which the heterocyclic ring can formally act as a 2e−, 3e−, 5e− or 6e− donor ligand. These structural bonding modes are described through examples in which the heterocyclic ring interacts with halide anions, N atoms and particularly metal centres, forming monometallic, dimetallic and trimetallic complexes. The structural features which determine which compounds are likely to act as cyclic chelators are discussed and examples of thiadiazole, diselenadiazolyl and dithiole rings acting as cyclic chelators are given. 相似文献
936.
The ionic product of water, pK(w)=-log[H(+)][OH(-)], has been determined in aqueous solutions of sodium perchlorate over the concentration range of 1.0-8.0 M at 25 degrees C from high-precision potentiometric titrations carried out in cells with liquid junction using both glass and hydrogen electrodes. The glass electrode results are systematically lower probably as a result of interference by Na(+) ions. 相似文献
937.
Higher order discretization has not been widely successful in industrial applications to compressible flow simulation. Among several reasons for this, one may identify the lack of tailor-suited, best-practice relaxation techniques that compare favorably to highly tuned lower order methods, such as finite-volume schemes. In this paper we investigate solution algorithms in conjunction with high-order Spectral Difference discretization for the Euler equations, using such techniques as multigrid and matrix-free implicit relaxation methods. In particular we present a novel hybrid multilevel relaxation method that combines (optionally matrix-free) implicit relaxation techniques with explicit multistage smoothing using geometric multigrid. Furthermore, we discuss efficient implementation of these concepts using such tools as automatic differentiation. 相似文献
938.
Single-molecule magnets: a Mn25 complex with a record S = 51/2 spin for a molecular species 总被引:4,自引:0,他引:4
Murugesu M Habrych M Wernsdorfer W Abboud KA Christou G 《Journal of the American Chemical Society》2004,126(15):4766-4767
The reaction of MnCl2.4H2O (3 equiv), pyridine-2,6-dimethanol (pdmH2) (10 equiv), and NaN3 (10 equiv) in MeOH/MeCN (1:2 v/v) with NMe4OH (1 equiv) gave [Mn25O18(OH)2(N3)12(pdm)6(pdmH)6](Cl)2.12MeCN (1.12MeCN) in approximately 30% yield. The cation of complex 1 comprises five Mnx layers of three types in an ABCBA arrangement. Fitting of variable-temperature and -field magnetization data establishes that 1 has an S = 51/2 ground state, the largest value for a molecular species. The complex also displays hysteresis loops below 0.6 K in magnetization vs applied field sweeps, establishing it as the largest spin single-molecule magnet to date. 相似文献
939.
Xuhong Guo Jie Wang Li Li Duc‐Truc Pham Philip Clements Stephen F. Lincoln Bruce L. May Qingchuan Chen Li Zheng Robert K. Prud'homme 《Journal of Polymer Science.Polymer Physics》2010,48(16):1818-1825
A 1H NMR and rheological study of host‐guest complexation interactions between three β‐cyclodextrin and three adamantyl substituted poly(acrylate)s, and also between them and adamantan‐1‐carboxylate and native β‐cyclodextrin, respectively, is reported. A close correllation between molecular level interactions and macroscopic characteristics of polymer networks in aqueous solution exists. It is found that intra‐ and intermolecular host‐guest complexation between the host β‐cyclodextrin and guest adamantyl substituents and the length of the aliphatic tether between them and the poly(acrylate) backbone have important roles. Dominantly, steric effects and competitive intra‐ and intermolecular host‐guest complexation are found to control poly(acrylate) isomeric interstrand linkage in polymer network formation. The preparations of five new 3% randomly substituted poly(acrylate)s are reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1818–1825, 2010 相似文献
940.
Jayaraman S May EL Hillier AC 《Langmuir : the ACS journal of surfaces and colloids》2006,22(25):10322-10328
The influence of a surface potential gradient on the location and extent of electrochemical reactions was examined using a scanning electrochemical microscope. A linear potential gradient was imposed on the surface of a platinum-coated indium tin oxide electrode by applying two different potential values at the edges of the electrode. The applied potentials were used to control the location and extent of several electrochemical reactions, including the oxidation of Ru(NH3)6(2+), the oxidation of H2, and the oxidation of H2 in the presence of adsorbed CO. Scanning electrochemical mapping of these reactions was achieved by probing the feedback current associated with the oxidation products. The oxidation of Ru(NH3)6(2+) occurred at locations where the applied potential was positive of the formal potential of the Ru(NH3)6(2+/3+) redox couple. The position of this reaction on the surface could be spatially translated by manipulating the terminal potentials. The rate of hydrogen oxidation on the platinum-coated electrode varied spatially in the presence of a potential gradient and correlated with the nature of the electrode surface. High oxidation rates occurred at low potentials, with decreasing rates observed as the potential increased to values where platinum oxides formed. The extent of oxide formation versus position was confirmed with in-situ ellipsometry mapping. In the presence of adsorbed carbon monoxide, a potential gradient created a localized region of high activity for hydrogen oxidation at potentials between where carbon monoxide was adsorbed and platinum oxides formed. The position of this localized region of activity could be readily translated along the surface by changing the terminal potential values. The ability to manipulate electrochemical reactions spatially on a surface has potential application in microscale analytical devices as well as in the discovery and analysis of electrocatalytic systems. 相似文献