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41.
Ball LJ Dickie AP Mair FS Middleton DA Pritchard RG 《Chemical communications (Cambridge, England)》2003,(6):744-745
Analysis of crystals of the lithium complex of the tripodal ligand formed upon addition of adamantanone to a 1,5 diazapentadienyllithium complex reveals a long C-C bond which ruptures upon dissolution in non-co-ordinating solvents. 相似文献
42.
The fluorinated anti-psychotic drug trifluoperazine (TFP) has been shown to be a K(+)-competitive inhibitor of gastric H(+)/K(+)-ATPase, a membrane-embedded therapeutic target for peptic ulcer disease. This paper describes how variable contact time (19)F cross-polarization magic angle spinning (VCT-CP/MAS) NMR has been used to probe the inhibitory interactions between TFP and H(+)/K(+)-ATPase in native gastric membranes. The (19)F CP/MAS spectra for TFP in H(+)/K(+)-ATPase enriched (GI) gastric membranes and in control membranes containing less than 5 nmol of the protein indicated that the drug associates with the membranes independently of the presence of H(+)/K(+)-ATPase. The (19)F peak intensities in the VCT-CP/MAS experiment confirmed that TFP undergoes slow dissociation (k(off) < 100 s(-1)) from binding sites in GI membranes, and more rapid dissociation (k(off) < 100 s(-1)) from control membranes. The spectra showed that up to 40% of bound TFP was displaced from GI membranes by 100 mM K(+) and by the K(+)-competitive inhibitor TMPIP, but TFP was not displaced from the control membranes. Hence the spectra of TFP in GI membranes represent the drug bound to the K(+)-competitive inhibitory site of H(+)/K(+)-ATPase and to other non-specific sites. The affinity of TFP for the K(+)-competitive site (K(D) = 4 mM) was determined from a binding curve of (19)F peak intensity versus TFP concentration after correction for non-specific binding. The K(D) was much higher than the IC(50) for ATPase inhibition (8 microM), which suggests that the substantial non-specific binding of TFP to the membranes contributes to ATPase inhibition. This novel approach to probing ligand binding can be applied to a wide range of membrane-embedded pharmaceutical targets, such as G-protein coupled receptors and ion channels, regardless of the size of the protein or strength of binding. 相似文献
43.
Burdzinski GT Middleton CT Gustafson TL Platz MS 《Journal of the American Chemical Society》2006,128(46):14804-14805
Photolysis of phenyl and o-biphenylyl azide (at 270 nm) releases vibrationally excited singlet nitrene which isomerizes to the corresponding hot 1,2-didehydroazepine at a rate competitive with thermal relaxation. Using ultrafast vibrational spectroscopy we observe the formation of vibrationally excited 1,2-4,6-azacycloheptatetraene (1,2-didehydroazepine) in picoseconds following photolysis of phenyl azide in chloroform and o-biphenylyl azide in acetonitrile at ambient temperature. 相似文献
44.
A growth-chamber experiment was conducted to evaluate whether ethylenenediurea (EDU), a chemical shown to be protective against ozone pollution, could ameliorate foliar damage induced by ultraviolet-B (UV-B) radiation exposure in 'Roanoke' soybean (Glycine max L.), a UV-B-sensitive cultivar, and whether these effects could be discriminated using fluorescence (F) observations. The experiment had four treatment groups: control; biologically effective UV-B (18 kJ m(-2) day(-1)); EDU (500 micromol mol(-1)); and both UV-B and EDU (UV/EDU). Measurements included photosynthetic pigments, F image system (FIS) images of adaxial surfaces in four spectral regions (blue, green, red and far-red) and F emission spectra of the pigment extracts produced at two excitation wavelengths, 280 nm (280EX) and 380 nm (380EX). Several F ratios from 280EX, 380EX and the FIS images successfully separated the low UV vs high EDU group responses based on means alone, with intermediate values for controls and the combined UV/EDU groups. A UV-B/blue emission ratio, F315/F420 (280EX), was correlated with chlorophyll content (microg cm(-2))(R = 0.88, P < 0.001), as was a ratio of emissions at two UV-A wavelengths: F330/F385 (280EX) (R = 0.87). These two 280EX ratios were also linearly correlated with emission ratios produced by 380EX, such as the far-red/green ratio, F730/F525 (380EX) (R = 0.92, P < 0.001), and clearly distinguished the UV-B and EDU groups separately, and which bracketed the similar intermediate responses of the UV/EDU and control groups. The FIS images additionally captured the following anatomical spatial patterns across the leaf surfaces: (1) emissions of UV-B-irradiated leaves were more uniform but lower in intensity than those of other groups; and (2) emissions of EDU-treated leaves exhibited the greatest variation in spatial patterns because veins had elevated blue F and leaf edges had enhanced red and far-red F. This experiment supports the hypothesis that EDU substantially ameliorated UV-B damage to foliage, a result that relied on the combined use of FIS images and emission spectra. 相似文献
45.
Mark D. Middleton 《Tetrahedron letters》2005,46(23):4039-4043
A practical synthesis of 2-substituted 1,3-cyclohexadienes by the cross enyne metathesis between alkynes and 1,5-hexadiene is reported. The isolation of the 1,3-cyclohexadienes has been hampered by the formation of an inseparable triene by-product. The use of a second consecutive cross alkene metathesis to give water-soluble products allowed removal of this by-product. Using this one-pot procedure, a synthesis of cyclohexadienes from simple starting materials was developed. The procedure was used in a three-step synthesis of a functionalized tetrahydroquinoline using Pd(II)-catalyzed chloroacetoxylation (Bäckvall reaction) for cyclohexadiene functionalization. 相似文献
46.
A concise synthesis of novel homochiral aromatic amino acid surrogates comprising a tetrahydroindazole or a benzisoxazole system was developed via the acylation of a cyclic 1,3-diketone by the side-chain carboxyl functionality of either Boc-Asp-OtBu or Boc-Glu-OtBu followed by regioselective condensation with hydrazine, N-benzylhydrazine and hydroxylamine. The tetrahydroindazole nucleus was also constructed by the condensation of Boc-Asp-OtBu with the enamine, 1-pyrrolidino-1-cyclohexene followed by acid-hydrolytic treatment and reaction with hydrazines. Further functional group transformations gave Nα-Fmoc-protected derivatives as useful building blocks for solid-phase peptide assembly. 相似文献
47.
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49.
Patching SG Middleton DA Henderson PJ Herbert RB 《Organic & biomolecular chemistry》2003,1(12):2057-2062
The synthesis of [2'-(13)C, 1,3-(15)N2]uridine 11 was achieved as follows. An epimeric mixture of D-[1-(13)C]ribose 3 and D-[1-(13)C]arabinose 4 was obtained in excellent yield by condensation of K13CN with D-erythrose 2 using a modification of the Kiliani-Fischer synthesis. Efficient separation of the two aldose epimers was pivotally achieved by a novel ion-exchange (Sm3+) chromatography method. D-[2-(13)C]Ribose 5 was obtained from D-[1-(13)C]arabinose 4 using a Ni(II) diamine complex (nickel chloride plus TEMED). Combination of these procedures in a general cycling manner can lead to the very efficient preparation of specifically labelled 13C-monosaccharides of particular chirality. 15N-labelling was introduced in the preparation of [2'-(13)C, 1,3-(15)N2]uridine 11 via [15N2]urea. Cross polarisation magic angle spinning (CP-MAS) solid-state NMR experiments using rotational echo double resonance (REDOR) were carried out on crystals of the labelled uridine to show that the inter-atomic distance between C-2' and N-1 is closely similar to that calculated from X-ray crystallographic data. The REDOR method will be used now to determine the conformation of bound substrates in the bacterial nucleoside transporters NupC and NupG. 相似文献
50.
A variety of functionalised β-iodoacetals have been prepared, and their elimination reaction to give ketene acetals conducted under mild conditions. 相似文献