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11.
The localization of oncogenic Src and Ras proteins to cellular plasma membranes is critical for the proliferation of specific cancers. In addition to other lipid modifications, these proteins require posttranslational palmitoylation of specific cysteine residues by the enzyme palmitoyl acyltransferase (PAT) in order to be stably anchored at plasma membranes. Hence, the identification of inhibitors of protein palmitoylation has significant potential to define a new class of antitumor agents. However, studies of protein palmitoylation have been hindered by the dynamic and reversible nature of cysteine acylation and the lack of sensitive and convenient assays of PAT activity. To facilitate the rapid identification of compounds that affect protein palmitoylation, we report the solid-phase synthesis of a fluorescent cell-permeable palmitoyl acyltransferase substrate that mimics the N-terminus of Src family proteins. Metabolic radiolabeling and epifluorescence microscopy of Jurkat lymphocytes treated with this Src-mimetic lipopeptide revealed that this compound is palmitoylated intracellularly, which confers localization at cellular plasma membranes. Addition of the palmitoylation inhibitor 2-bromopalmitic acid to substrate-treated cells blocked palmitoylation and diminished substrate-mediated plasma membrane fluorescence. Analysis of inhibition of palmitoylation by flow cytometry revealed that this fluorescent lipopeptide substrate represents a highly sensitive molecular probe of palmitoyl acyltransferase activity that enables unprecedented high-throughput assays of protein palmitoylation. 相似文献
12.
Khlobystov AN Brett MT Blake AJ Champness NR Gill PM O'Neill DP Teat SJ Wilson C Schröder M 《Journal of the American Chemical Society》2003,125(22):6753-6761
A series of structurally related binuclear metallacycles [Cd(NO(3))(2)L](2), where L is an angular exo-bidentate ligand, have been synthesized. Each metallacycle contains two coordinatively unsaturated, chiral metal centers within a single molecule, and the assembly of these metallacycles into polymeric framework structures has been studied systematically for the first time. Stereoselective homochiral association of [Cd(NO(3))(2)L](2) leads to the formation of helical coordination polymers, whereas meso type association results in nonhelical chain structures. The type of stereoselective aggregation depends on the conditions of self-assembly as well as on ligand functionality. Both helical and nonhelical polymeric complexes have been isolated for the metallacycle [Cd(NO(3))(2)(2,4'-pyacph)](2) (2,4'-pyacph = 2,4'-(4-ethynylphenyl)bipyridyl). Homochiral association results in the formation of helical [Cd(NO(3))]( infinity ) chains which link the binuclear [Cd(NO(3))(2)(2,4'-pyacph)](2) metallacycles into racemic two-dimensional sheets which contain both P and M [Cd(NO(3))]( infinity ) helices. In contrast, meso-association leads to the formation of nonhelical one-dimensional chains. It is shown that the product of homochiral association is predominately formed at room temperature and that of meso-association is generated at elevated temperatures. Thus, it may be concluded that the homochiral association appears to be energetically less favorable than the meso-association, a conclusion that has been confirmed by theoretical calculations of the crystal lattice energy. Several high-yield syntheses of bipyridyl-type ligands used for metallacyclic assembly are also reported. 相似文献
13.
Determination of pentachlorophenol by negative ion chemical ionization with membrane introduction mass spectrometry 总被引:2,自引:0,他引:2
Pentachlorophenol (PCP) was used as a model compound to explore the potential of desorption chemical ionization (DCI) in the determination of polychlorinated pesticides using membrane introduction mass spectrometry (MIMS). A direct insertion membrane probe was modified so that a chemical ionization plasma could be established at the membrane surface. Using selected ion monitoring (SIM) in a tandem triple quadrupole mass spectrometer with isobutane chemical ionization (CI), the PCP detection limit under positive chemical ionization is 20 ppb whereas negative CI gives detection limits in the low ppb range. This performance is achieved without any pre-treatment or derivatization of the sample. Negative ion CI gives a signal that is linear over a concentration range of 2-1000 ppb. Comparison of data obtained with low ppb samples of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol suggests that the sensitivity of this analytical procedure increases with increase in the number of electronegative substituents in the molecule. 相似文献
14.
The ionic Diels-Alder reaction, whereby an alpha,beta-unsaturated acetal in combination with a Lewis or Bronsted acid forms an equilibrium concentration of an activated dienophile, has been developed to provide an enantioselective synthesis of cis-decalins. Cyclohex-2-enone type chiral acetals of (2R,3R)-butane-2,3-diol have been screened against Lewis and Br?nsted acids with a variety of dienes and are efficient for the synthesis of a limited subset of cis-decalin structures. Diastereoselectivities of 73% and 82% have been found for the asymmetric ionic Diels-Alder reaction between the chiral acetal derivatives of cyclohex-2-enone (6) and 2-methylcyclohex-2-enone (18) with 2,3-dimethyl-1,3-butadiene (7). Terminal substituents on the diene partner in general render the system unreactive. However a synthetically useful cis-decalin 31, derived from the reaction of 2-methylcyclohex-2-enone and Z-3-t-butyldimethyl-silyloxypenta-1,3-diene has been prepared in enantiomerically pure form in 74% isolated yield using this asymmetric ionic Diels-Alder protocol. 相似文献
15.
Dan M.J. Doble Richard D. Kay Colin H. Benison Alexander J. Blake Xiang Lin Claire Wilson Martin Schröder 《Journal of inclusion phenomena and macrocyclic chemistry》2001,41(1-4):23-30
Reaction of tris-(2-aminoethyl)amine (tren) andthe sodium salt of an -ketocarboxylic acid, typically sodium pyruvate, affordsin the presence of a lanthanide ion aseries of complexes and aggregates includingmononuclear, cyclic tetranuclear and polymerspecies of [L1]3- ([L1]3-=N[CH2CH2N=C(CH3)COO-]3).The aggregation of these and related d-block elementcomplexes with Na+ ions leadsto the formation of polymeric materials, and thefactors influencing the formation and controlof these various aggregation states are discussed.Metal cations also template the aggregationof the fragment [Ni(L2)] ([L2]2- =CH2[CH2N = C(CH3)COO-]2)to give, in high yield, the polynuclearaggregates {[Ni(L2)]6M}x+(M = Nd, Pr, Ce, La, x = 3; M = Sr, Ba, x = 2). The structures of{[Ni(L2)]6M}x+ show aninterstitial twelve co-ordinate, icosahedralcation Mx+ encapsulated by six [Ni(L2)]fragments. In the presence ofNa+, aggregation of [Ni(L2)] fragments affords {[Ni(L2)]9Na4(H2O)(MeOH)(ClO4)}3+ thestructure of whichshows four Na+ ions templating the formation ofa distorted tricapped trigonal prismatic[Ni(L2)]9 cage. Thus, control overconstruction of various polynuclear cages viaself-assembly at octahedral junctions can beachieved using main group, transition metaland lanthanide ion templates. 相似文献
16.
17.
Blake AJ Brett MT Champness NR Khlobystov AN Long DL Wilson C Schröder M 《Chemical communications (Cambridge, England)》2001,(21):2258-2259
4,4'-Bipyridine N,N'-dioxide (L) acts as a hydrogen-bond acceptor in the compounds ([M(NO3)2(H2O)4].L2) (M = Co, Ni) to form doubly-interpenetrated framework materials with sixfold topological connectivity. 相似文献
18.
Martic G Gentner F Seveno D De Coninck J Blake TD 《Journal of colloid and interface science》2004,270(1):171-179
To model the imbibition of liquids into porous solids, use is often made of the Lucas-Washburn equation, which relates the distance of penetration of a liquid at a given time to the pore radius, the viscosity and surface tension of the liquid, and the effective contact angle between the liquid and the solid. In this paper, we extend previous large-scale molecular dynamics simulations to show how this tool can be used to study the details of liquid imbibition, including the impact of the contact angle on the dynamics of penetration and the evolution of the internal flow field. In particular, we show that the asymptotic behavior of the contact angle versus time for a completely wetting liquid is given by approximately t(-1/4). 相似文献
19.
20.
A combination of thermospray liquid chromatography-mass spectrometry (LC-MS) and LC MS MS has allowed the structural elucidation of a number of metabolites of 4-[2-(dipropylamino)ethyl]-1,3-dihydro-2H-indol-2-one (SK & F 101468) in monkey urine. By using LC-MS-MS with the third quadrupole (Q3) set up in multiple ion detection (MID) mode, a number of metabolites were subsequently detected in the human urine and plasma samples despite very low dosing regimes. This was achieved with minimal sample preparation, e.g. for the urine sample centrifugation was the only preparative step, in order to remove particulate matter, prior to analysis. The good signal-to-noise ratio obtained for the human samples, using LC MS MS with Q3 set up for MID, raised the possibility of a LC-MS-MS quantitative assay. As a result, the detection limit of this method for SK&F 101468 when dissolved in methanol was determined to be in the region of 20 pg on column. 相似文献