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21.
Aequationes mathematicae - We discuss Milne’s inequality and apply it to the sides of a convex quadrilateral to derive an approximation to the area of the quadrilateral via arithmetic and... 相似文献
22.
Larios C Miñones J Haro I Alsina MA Busquets MA Trillo JM 《The journal of physical chemistry. B》2006,110(46):23292-23299
The peptide corresponding to the sequence (279-298) of the Hepatitis G virus (HGV/GBV-C) E2 protein was synthesized, and surface activity measurements, pi-A compression isotherms, and penetration of E2(279-298) into phospholipid monolayers spread at the air-water interface were carried out on water and phosphate buffer subphases. The results obtained indicated that the pure E2(279-298) Langmuir monolayer exhibited a looser packing on saline-buffered than on pure water subphase and suggest that the increase in subphase ionic strength stabilizes the peptide monolayer. To better understand the topography of the monolayer, Brewster angle microscopy (BAM) images of pure peptide monolayers were obtained. Penetration of the peptide into the pure lipid monolayers of dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) and into mixtures of dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) at various initial surface pressures was investigated to determine the ability of these lipid monolayers to host the peptide. The higher penetration of peptide into phospholipids is attained when the monolayers are in the liquid expanded state, and the greater interaction is observed with DMPC. Furthermore, the penetration of the peptide dissolved in the subphase into these various lipid monolayers was investigated to understand the interactions between the peptide and the lipid at the air-water interface. The results obtained showed that the lipid acyl chain length is an important parameter to be taken into consideration in the study of peptide-lipid interactions. 相似文献
23.
24.
Célio L. Cavalcante Jr Diana C.S. Azevêdo Irla G. Souza A. Cristina M. Silva Odelsia L.S. Alsina Verôonica E. Lima Antonio S. Araujo 《Adsorption》2000,6(1):53-59
This paper presents experimental results for equilibrium and diffusion of C8 aromatics in laboratory synthesised crystals of AlPO4-11. The samples were prepared by the hydrothermal method, starting from pseudobohemite (CONDEA), 85% phosphoric acid, water and di-isopropilamine as organic template. Adsorption and diffusion data were obtained mainly by gravimetry at temperatures between 60–100°C. Saturation capacities were found in the range of 4 wt%. Equilibrium constants were estimated using virial plots yielding heats of adsorption between 10–12 Kcal/mol at low coverage. Intracrystalline diffusivities at higher temperatures (150–180°C) were also measured, using the Zero-Length-Column (ZLC) method. Diffusivities from both methods (gravimetric and ZLC) agreed reasonably well and followed a typical Arrhenius behaviour, with low activation energy (ca. 7 Kcal/mol). 相似文献
25.
Maria Jesús Sánchez-Martín José Manuel Amigo Montserrat Pujol Isabel Haro M. Asunción Alsina M. Antonia Busquets 《Analytical and bioanalytical chemistry》2009,394(4):1003-1010
The physicochemical characterization of the peptide sequence E1(145–162) corresponding to the structural protein E1 of the
hepatitis G virus was done by studying its interaction with model membranes. Small unilamellar vesicles (SUVs) of dimyristoylphosphatidylglycerol
or dimyristoylphosphatidylcholine were chosen as mimetic membranes. Peptide incorporation and location in the phospholipid
bilayer was investigated by fluorescence anisotropy with SUVs labeled with diphenylhexatriene (DPH) or trimethylammonium–DPH.
The addition of the peptide E1(145–162) showed significant changes in the anisotropy values of the probe located at the air/water
interface. These results indicate that the peptide E1(145–162) preferably interacts with the lipid surface without penetrating
inside the bilayer. A series of fluorescence experiments based on tryptophan peptide fluorescence were modeled by means of
multivariate curve resolution-alternating least squares (MCR-ALS) algorithm to further study the peptide interaction with
bilayers at different temperatures. The preliminary results obtained with MCR-ALS showed how the peptide concentration decay
is directly linked to the appearance of a new specie, which corresponds to the lipid-peptide binding. These results provide
useful information for the design of synthetic immunopeptides that can be incorporated into a liposomal system with potential
to promote a direct delivery of the membrane-incorporated immunogen to the immunocompetent cells, thus increasing the immuno
response from the host.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
26.
Alsina MA Ortiz A Polo D Comelles F Reig F 《Journal of colloid and interface science》2006,294(2):385-390
Two peptides based on the active SIKVAV sequence were synthesized and hydrophobically modified through attachment of a myristoyl residue to the amino terminal group. A comparative study was carried out on the physicochemical properties of both parent and hydrophobically modified structures. Properties studied were hydrophobicity, surface activity, spreadability on aqueous surfaces, penetration in lipid monolayers, aggregation and haemolytic activity. Results obtained indicate that myristoyl containing peptides form micelles at 10(-6) M concentration, whereas parent peptides start to aggregate at 10(-5) M. All of them are able to spread on aqueous surfaces forming stable monolayers. Concerning their haemolytic activity only one of the sequences promotes a partial lysis of erythrocytes after 30 min incubation at 37 degrees C and 10(-5) M concentration in the media. 相似文献
27.
Ippolito Antonini Francesco Claudi Gloria Cristalli Mario Grifantini Sante Martelli 《Journal of heterocyclic chemistry》1980,17(1):181-185
The course of the thermal, acid-catalysed and iodide-catalysed decomposition of 2-amino-3-(2′,2′-dimethylaziridino)-1,4-naphthoquinone (III) was investigated. Thermal and iodide-catalysed decompositions gave mainly 2,3-diamino-1,4-naphthoquinone (VI) and 2-amino-3-(2′-methylallylamino)-1,4-naphthoquinone (V) together with low amounts of 2,2-dimethyl-1,2,3,4,5,10-hexahydrobenzo[g]quinoxaline (IV) and 2-isopropyl-1H-naphthoimid-azole-4,9-dione (VII). The acid catalysed isomerization of the aziridinonaphthoquinone III with halohydric acids or with acetic acid readily gave the opening of the aziridine ring; the corresponding salts of 2-amino-3-(2′-haloisobutylamino)-1,4-naphthoquinones (VIIIa-c) and 2-amino-3-(2′-acetoxyisobutylamino)-1,4-naphthoqunone (X) were formed by cleavage of the carbon-nitrogen bond at the substituted carbon atom. Hypotheses on the mechanism of these reactions are given. 相似文献
28.
Giovanni Casini Francesco Claudi Mario Grifantini Sante Martelli 《Journal of heterocyclic chemistry》1974,11(3):377-386
The course of the hydriodic acid-catalysed and iodide-catalysed isomerization of various 2-amino-3-substituted-aziridino-1,4-naphthoquinones (I) to 1,2,3,4,5,10-hexahydrobenzo[g]-quinoxaline-5,10-diones (III) is investigated, and steric aspects of the reaction are also considered. Only in the case of the phenylaziridino derivative (Ie) does hydriodic acid afford direct cyclization to the corresponding benzoquinoxalinedione (IIIe); in all other cases the hydriodides (V) of the cleavage products (II) are obtained, and liberation of the free bases (II) results in cyclization to the corresponding benzoquinoxalinediones (III) when the aziridine ring is monosubstituted or trans disubstituted, with retention of configuration in the latter case. In contrast, the free bases (II) obtained from cis disubstituted (I) are relatively stable and cyclize with excess iodide yielding trans disubstituted (III). Correspondingly, monosubstituted and trans disubstituted I undergo iodide-catalysed isomerization to III whereas cis disubstituted I do not react. 相似文献
29.
The manual solid-phase preparation of racemic α-substituted bicyclic proline hydantoins and analogs, which can potentially contain up to four sites of structural diversity (ring size and substitution on the ring or at the ring fusion), is described. Key steps involved alkylation of aldimines of resin-bound amino acids with α,ω-dihaloalkanes and intramolecular displacement of the halide to generate α-substituted prolines and homologs. After formation of resin-bound ureas by reaction of these sterically-hindered secondary amines with isocyanates, base-catalyzed cyclization/cleavage yielded the desired hydantoin products. 相似文献
30.
Ippolito Antonini Francesco Claudi Gloria Cristalli Mario Grifantini Sante Martelli 《Journal of heterocyclic chemistry》1981,18(2):399-404
The course of the thermal decomposition of various 2-amino-3-substituted aziridino-1,4-naphthoquinones (Ia-g) was investigated. In all the cases, the thermal decomposition gave variable amounts of 2,3-diamino-1,4-naphthoquinone (II) and of substituted 1,2,3,4,5,10-hexahydrobenzo[g]quinoxaline-5,10-diones (IIIa-g) with complete stereospecificity. The decomposition of the aziridines Ib,f also gave significative amounts of 2-amino-3-allylamino-1,4-naphthoquinones (IVb,f). In the case of 2-amino-3-(2′-phenyl-3′-ethylaziridino)-1,4-naphthoquinone (Ig), the formation of trans-1-phenyl-1-butene (V), 2-(1-phenylpropyl)-1H-naphtho-imidazole-4,9-dione (VI), 2-phenyl-3-ethyl-3,4,5,10-tetrahydrobenzo[g]quinoxaline-5,10-dione (VII), 2-phenyl-3-ethyl-5,10-dihydrobenzo[g]quinoxaline-5,10-dione (VIII), and a mixture of cis- and trans-4H-2,3,5,6-tetra-hydro-2-phenyl-3-ethyl-5-iminonaphtho[1,2-b]oxazin-6-one (IX) also occurred. Hypotheses concerning the mechanism and the steric course of this reaction are given. The reaction is a general method for the stereospecific synthesis of 2,3-disubstituted 1,2,3,4,5,10-hexahydrobenzo[g]quinoxalines. 相似文献