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11.
Metabolic fingerprinting of Ephedra species using 1H-NMR spectroscopy and principal component analysis 总被引:4,自引:0,他引:4
Kim HK Choi YH Erkelens C Lefeber AW Verpoorte R 《Chemical & pharmaceutical bulletin》2005,53(1):105-109
The metabolomic analysis of Ephedra species was performed using 1H-NMR spectroscopy and multivariate data analysis. A broad range of metabolites could be detected by 1H-NMR spectroscopy without any chromatographic separation. The principal component analysis used to reduce the huge data set obtained from the 1H-NMR spectra of the plant extracts clearly discriminated three different Ephedra species. The major differences in Ephedra sinica, Ephedra intermedia and Ephedra distachya var. distachya were found to be due to benzoic acid analogues in the aqueous fraction and ephedrine-type alkaloids in the organic fraction. Based on this metabolomic recognition, one of nine commercial Ephedra materials evaluated was shown to be a mixture of Ephedra species. This method will be a useful tool for chemotaxonomic analysis and authentification of Ephedra species including quality control of plant materials. 相似文献
12.
UVB irradiation of normal human skin favors the development of type-2 T-cells in vivo and in primary dermal cell cultures 总被引:1,自引:0,他引:1
Di Nuzzo S Sylva-Steenland RM Koomen CW Nakagawa S van Breemen M de Rie MA Das PK Bos JD Teunissen MB 《Photochemistry and photobiology》2002,76(3):301-309
To determine the effect of UVB exposure on the balance of type-1 or type-2 T-cells in skin, we examined the expression of key markers interferon (IFN)-gamma and interleukin (IL)-4 in cryostat sections. IFN-gamma mRNA was clearly detectable in nonirradiated control skin, and IFN-gamma protein was found in 2% of the dermal CD3pos T-cells, whereas IL-4 mRNA was hardly detectable, and no IL-4 protein was found. In contrast, IL-4 mRNA expression increased upon irradiation, and IL-4 was found in 2% of the T-cells at day 2 after UVB-exposure. Concomitantly, IFN-gamma mRNA expression decreased, and IFN-gamma protein became absent. We also analyzed T-cells present in primary dermal cell cultures, which were used as an in vitro equivalent of the in vivo situation. As compared with T-cells from control skin, T-cells in dermal cell cultures from UVB-exposed skin displayed an increased IL-4 and decreased IFN-gamma expression. No such skewing occurred when the T-cells from irradiated skin were cloned in the absence of a dermal microenvironment. Except for an occasional positive T-cell, type-1-associated cell-surface markers (CCR5, CXCR3) or type-2 markers (CCR3, CD30, CRTH2) were undetectable in situ. But these markers were expressed on cultured dermal T-cells from UVB-exposed and control skin at a comparable level, but did not correlate with the IFN-gamma and IL-4 production. Altogether, UVB-induced changes of the dermal microenvironment favor the development of type-2 T-cells. 相似文献
13.
Dirksen A Kleverlaan CJ Reek JN De Cola L 《The journal of physical chemistry. A》2005,109(24):5248-5256
A photoactive supramolecular assembly that is based on the hydrogen-bonded system H1.G2, consisting of a methyl viologen-functionalized barbiturate host (H1) (1-(N-(3,5-bis[[(6-tert-butylacetylamino-2-pyridyl)amino]carbonyl])-phenylacetamide)-1'-methyl-4,4'-bipyridium) and a [Re(Br)(CO)3(barbi-bpy)] (barbi-bpy = 5-[4-(4'-methyl)-2,2'-bipyridyl]methyl-2,4,6-(1H,3H,5H)-pyrimidinetrione) complex as the guest (G2) is described. The host molecule contains a well-known electron accepting group (methyl viologen), whereas the guest system can act as an efficient electron donor in the excited state. Upon self-assembly, the resulting adduct (H1.G2) represents an interesting noncovalently linked donor-acceptor system. The H1.G2 complex has been characterized in acetonitrile-d3 using 1H NMR and diffusion-ordered NMR spectroscopy (DOSY). The photophysical properties of the components and of the assembly have been studied in dichloromethane, in which the assembly has a high binding constant (Kass > or = 2 x 10(5) M(-1)), using time-resolved fluorescence and transient absorption spectroscopy. A detailed investigation of the hydrogen-bonded complex H1.G2 revealed that, upon excitation of the rhenium compound G2, an ultrafast electron-transfer process occurs from the metal-based component to the acceptor unit. The kinetics of the forward and back electron-transfer processes have been determined. 相似文献
14.
Dovas A. Saulys Cornelis E. C. A. Hop Donald F. Gaines 《Journal of the American Society for Mass Spectrometry》1994,5(6):537-543
Metastable ion (MI) and collision-induced dissociation (CID) mass spectra have been recorded and compared for all nine C4H12Si+. isomers. The (Me)4Si+., t-BuSiH 3 +. , s-BuSiH 3 + , and (Me)2EtSiH+. isomers have unique MI and CID mass spectra. The MI mass spectra, including the kinetic energy release values, of (Me)(i-Pr)SiH 2 +. and (Me)(n-Pr)SiH 2 +. are identical, which implies isomerization. MI data also suggest that a fraction of the n-BuSiH 3 +. ions rearrange into branched (Me)2EtSiH+. ions and a fraction of the n-BuSiH 3 +. ions rearrange into branched s-BuSiH 3 +. ions. A comparison with the isomeric C5H 12 +. pentanes reveals a crucial difference: H2 loss occurs for n-BuSiH 3 +. , i-BuSiH 3 +. , s-BuSiH 3 +. , (Me)(n-Pr)SiH 2 +. , (Me)(i-Pr)SiH 2 +. , and Et2SiH 2 +. , but not for any of the C5Hi 12 +. isomers. Generation of four- or five-membered silicon containing rings is suggested for H2 loss from the C4H12Si+. silanes. 相似文献
15.
Jeroen W. Sprengers Marcel A. Duin Cornelis J. Elsevier 《Journal of organometallic chemistry》2003,679(2):149-152
A highly active and selective in situ formed platinum(N-heterocyclic carbene) catalyst for the hydrosilylation of styrene with triethylsilane is described, which unlike all other known hydrosilylation catalysts, selectively yields hydrosilylation products, but (almost) no dehydrogenative silylation products. 相似文献
16.
Cornelis M. Moorhoff 《合成通讯》2013,43(16):2925-2935
An easy, rapid method for the preparation of arsonium salts of high yield and purity, by heating an alkyl halide and triphenylarsine as a melt at about 80°C, is described. 相似文献
17.
18.
Cornelis van der Mee 《Journal of Nonlinear Mathematical Physics》2014,21(2):265-277
In this article we give sufficient conditions on the scattering data of a defocusing or focusing Zakharov-Shabat system in order that its potential is square integrable. For a dense subset of integrable as well as square integrable potentials, we show that the scattering data actually satisfy these sufficient conditions. 相似文献
19.
Pavol Kováač Noel F. Whittaker Cornelis P. J. Glaudemans 《Journal of carbohydrate chemistry》2013,32(2):243-254
When methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-β-D-galacto-pyranoside (JO is treated in purified chloroform at 55-60′ with excess of dichloromethyl methyl ether in the presence of a catalytic amount of freshly fused zinc chloride for 1 h the corresponding α-glycosyl chloride 2 can be isolated by column chromatography in 75-80% yield. Compound 2 is an important intermediate in the synthesis of oligosaccharides containing a glycosyl-3-0-galactosyl sequence. Under the described reaction conditions the conversion 1 - 2 is accompanied by a slow anomerisation of 1 to give methyl 2,4,6-tri-0-benzoyl-3-0-benzyl-α-D-galactopyranoside. Prolonged treatment of 2 with the used excess of the reagent results in complete debenzylation of the substrate and the conversion of the putative 2,4,6-tri-O-benzoyl-α-D-galactopyranosyl chloride into the corresponding 3-0-formyl and 3-0-dichloromethyl derivatives. 相似文献
20.
Abstract Methyl 6-deoxy-6-fluoro-β-d-galactopyranoside has been obtained by treatment of methyl β-d-galactopyranoside with diethyl-aminosulfur trifluoride (DAST). Improvements over the existing syntheses of methyl 2, 3-di-O-benzyl-4-deoxy-4-fluoro-β-d-galacto-pyranoside from the corresponding 6-O-substituted 4-O-arylsul-fonyl-d-gluco derivatives are described. 13C NMR spectra of a series of methyl deoxyfluoro-β-d-galactopyranosides and their per-O-acetyl derivatives have been measured. The data obtained can be used as an aid for the interpretation of 13C NMR spectra of deoxyfluoro-β-d-galactopyranose-containing oligosaccharides and related substances. 相似文献