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51.
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
52.
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
53.
54.
J. Großfeld M. Tobia L. Zanchi L. Cini E. R. Bolton K. A. Williams R. Marcille A. Boutaric M. Roy D. P. Grettie R. C. Newton H. P. Kaufmann Ruth Okey Mary E. Turner T. Tusting Cocking G. Middleton J. K. Chowdhury und S. M. Das-Gupta 《Fresenius' Journal of Analytical Chemistry》1933,91(3-4):131-138
Ohne Zusammenfassung 相似文献
55.
J. Michael Robinson Masood Ahmed Nicky J. Alaniz Timothy R. Boyles Chris D. Brasher Kimberly A. Floyd Preston L. Holland Laura D. Maruffo Terry L. Mcmahan Stan Middleton Kevin D. O'Hara Marcia J. Pack Brandon D. Reynolds Romelia R. Rodriquez Dennis E. Sawyer Elena Sharp Sharai L. Simpson Clint L. Vanlandingham Rebecca S. Velasquez Brian M. Welch C. David Wright 《Journal of heterocyclic chemistry》1998,35(1):65-69
Alternative complimentary syntheses of penta-substituted pyridine rings with full regiochemical control of substituents were studied as a method for the synthesis of Streptonigrin ( 1 ). Various α-substituted acetophenones 2 were reacted with enones 3 in acetic acid/ammonium acetate and air to afford penta-substituted pyridines 4 . α-Substituents that could provide a source of exocyclic nitrogen at position 3 of these Steptonigrin ring-C models proved to be the limiting factor. However, an inverse “3+2+1” cyclocondensation of α-cyanochalcone 5c with 2-furyl ethyl ketone ( 6b ) afforded the desired model 6-(2-furyl)-5-methyl2,4-diphenyl-3-pyridinecarbonitrile ( 4g ) in 75% yield. 相似文献
56.
H. T. Fortune R. Middleton M. E. Cobern G. E. Moore S. Mordechai R. V. Kollarits 《Physics letters. [Part B]》1977,70(4):408-410
The 14C(t, p)16C reaction locates five new states in 16C, at excitation energies of 3120 ± 15, 3983 ± 10, 4136 ± 10 and 6109 ± 15 keV, in addition to the g.s. and 1.76 MeV states. The 3.02 and 3.98 MeV states appear to be the second 0+ and 2+ 2p-2h states, respectively. The 4.14 MeV state has Jπ = 4+ and the 6.11 MeV state has Jπ = 2+, 3−, or 4+. 相似文献
57.
Lambert TN Boon JM Smith BD Pérez-Payán MN Davis AP 《Journal of the American Chemical Society》2002,124(19):5276-5277
Cholate esters with phenylurea groups at the 7alpha- and 12alpha-positions are highly effective promoters of phosphatidylcholine translocation across vesicle and cell membranes. The urea groups are essential for strong binding of the highly polar phosphate portion of the phosphocholine headgroup and apparently cannot be replaced by simple amide, alcohol, or amine moieties. NMR and UV studies show that these synthetic translocases have very weak affinity for phosphatidylethanolamine and phosphatidylserine. 相似文献
58.
Sophie Lau David A. Middleton 《Angewandte Chemie (International ed. in English)》2020,59(41):18126-18130
The biological function of high‐density lipoprotein (HDL) nanoparticles, the so‐called good cholesterol that is associated with a low risk of heart disease, depends on their composition, morphology, and size. The morphology of HDL particles composed of apolipoproteins, lipids and cholesterol is routinely visualised by transmission electron microscopy (TEM), but higher‐resolution tools are needed to observe more subtle structural differences between particles of different composition. Here, reconstituted HDL formulations are oriented on glass substrates and solid‐state 31P NMR spectroscopy is shown to be highly sensitive to the surface curvature of the lipid headgroups. The spectra report potentially functionally important differences in the morphology of different HDL preparations that are not detected by TEM. This method provides new morphological insights into HDL comprising a naturally occurring apolipoprotein A‐I mutant, which may be linked to its atheroprotective properties, and holds promise as a future research tool in the clinical analysis of plasma HDL. 相似文献
59.
Levels of 40Ca below Ex = 10 MeV have been populated with the 32S(12C,α) reaction at an incident energy of 30 MeV. States which are thought to be based on 4p-4h and 8p-8h K = 0 configurations were more strongly populated than other low-lying states. 相似文献
60.
The broad 8.8 MeV 2+ state of 20Ne is seen to be populated with appreciable strength [(2J + 1)S = 0.21] in the reaction 19F(τ, d)20Ne, even though this strength would be zero in the simplest model. A model previously used to explain the mixing of 0+ states is found to work surprisingly well for the 2+ states. 相似文献