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71.
Nuopponen M Willför S Jääskeläinen AS Vuorinen T 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(13):2963-2968
Hydrophilic extracts of Scots pine (Pinus sylvestris) heartwood and sapwood and a solid Scots pine knotwood sample were studied by UV resonance Raman spectroscopy (UVRRS). In addition, UVRR spectra of two hydrophilic model compounds (pinosylvin and chrysin) were analysed. UV Raman spectra were collected using 244 and 257 nm excitation wavelengths. The chemical composition of the acetone:water (95:5 v/v) extracts were also determined by gas chromatography. The aromatic and oleophilic structures of pinosylvin and chrysin showed three intense resonance enhanced bands in the spectral region of 1649-1548 cm(-1). Pinosylvin showed also a relatively intense band in the aromatic substitution region at 996 cm(-1). The spectra of the heartwood acetone:water extract showed many bands typical of pinosylvin. In addition, the extract included bands distinctive for resin and fatty acids. The sapwood acetone:water extract showed bands due to oleophilic structures at 1655-1650 cm(-1). The extract probably also contained oligomeric lignans because the UVRR spectra were in parts similar to that of guaiacyl lignin. The characteristic band of pinosylvin (996 cm(-1)) was detected in the UVRR spectrum of the resin rich knotwood. In addition, several other bands typical for wood resin were observed, which indicated that the wood resin in the knotwood was resonance enhanced even more than lignin. 相似文献
72.
73.
The Ramanujan Journal - We shall consider a result of Fel’dman, where a sharp Baker-type lower bound is obtained for linear forms in the values of some E-functions. Fel’dman’s... 相似文献
74.
Attachment of Poly(l‐lactide) Nanoparticles to Plasma‐Treated Non‐Woven Polymer Fabrics Using Inkjet Printing
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75.
Karri Saarnio Kimmo Teinilä Minna Aurela Hilkka Timonen Risto Hillamo 《Analytical and bioanalytical chemistry》2010,398(5):2253-2264
Biomass burning has a strong influence on the atmospheric aerosol composition through particulate organic, inorganic, and soot emissions. When biomass burns, cellulose and hemicelluloses degrade, producing monosaccharide anhydrides (MAs) such as levoglucosan, mannosan, and galactosan. Therefore, these compounds have been commonly used as tracers for biomass burning. In this study, a fast water-based method was developed for the routine analysis of MAs, based on high-performance anion-exchange chromatography with electrospray ionization mass spectrometry detection. This method combines simple sample preparation, fast separation, and the advantages of the selective detection with MS. Analysis run was optimized to the maximum separation of levoglucosan, mannosan, and galactosan with 15-min analysis. The validation results indicated that the method showed good applicability for determination of MA isomer concentrations in ambient samples. The limit of detection was 100 pg for levoglucosan and 50 pg for mannosan and galactosan. Wide determination ranges enabled the analysis of samples of different concentration levels. The method showed good precision, both for standard solutions (3.9–5.9% RSD) and for fine particle samples (4.3–8.5% RSD). Co-elution of internal standard (carbon-13-labeled levoglucosan) and sugar alcohols with levoglucosan decreased the sensitivity of levoglucosan determination. The method was used to determine the MA concentrations in ambient fine particle samples from urban background (Helsinki) and rural background (Hyytiälä) in Finland. The average levoglucosan, mannosan, and galactosan concentrations were 77, 8.8, and 4.2 ng?m?3 in Helsinki (winter 2008–2009) and 17, 2.3, and 1.4 ng?m?3 in Hyytiälä (spring 2007), respectively. The interrelation of the three MA isomers was fairly constant in the ambient fine particle samples. 相似文献
76.
A monotonicity-type result for functions \(f\ : \ \mathbb {N}_a\rightarrow \mathbb {R}\) satisfying the sequential fractional difference inequality for \(t\in \mathbb {N}_{2+a-\mu -\nu }\), where \(0<\mu <1\), \(0<\nu <1\), and \(1<\mu +\nu <2\), is proved, subject to the restriction that We demonstrate that this result is sharp in the sense that the restriction \(\mu <2(1-\nu )\) cannot be improved.
相似文献
$$\begin{aligned} \Delta _{1+a-\mu }^{\nu }\Delta _{a}^{\mu }f(t)\ge 0, \end{aligned}$$
$$\begin{aligned} \mu <2(1-\nu ). \end{aligned}$$
77.
Vaca A Teixidor F Kivekäs R Sillanpää R Viñas C 《Dalton transactions (Cambridge, England : 2003)》2006,(41):4884-4885
Tetraiodo-ortho-carborane based X-ray contrast agents can be readily prepared in a high yield, fast, clean, regioselective fashion by a solvent-free reaction of ortho-carboranes with iodine in sealed tubes. 相似文献
78.
Ohne Zusammenfassung 相似文献
79.
Hakkarainen M 《Journal of chromatography. A》2003,1010(1):9-16
A solid-phase microextraction (SPME) method was developed to quantitatively determine the amount of 6-hydroxyhexanoic acid in aqueous solutions. The SPME method in combination with GC-MS was then applied to identify and quantify the low-molecular-mass compounds migrating from a new poly(vinyl chloride) (PVC) material, PVC/polycaprolactone-polycarbonate (PCL-PC) during ageing in water. It was shown that only a small amount of 6-hydroxyhexanoic acid, the final hydrolysis product of PCL-PC, migrated from the blend during ageing at 37 and 70 degrees C. If, however, the temperature was raised to 100 degrees C rapid hydrolysis of PCL-PC resulted. In addition to 6-hydroxyhexanoic acid, 6-hydroxyhexanoic acid dimer, caprolactone, different carboxylic acids, acetophenone and phenol were identified. SPME-GC-MS was also applied to monitor the low-molecular-mass compounds migrating from the PVC/PCL-PC blend during thermo-oxidation. 相似文献
80.
Phenylpropanoid glycosides from Rhodiola rosea 总被引:2,自引:0,他引:2
Rhodiola rosea L. (Golden Root) has been used for a long time as an adaptogen in Chinese traditional medicine and is reported to have many pharmacological properties. Along its known secondary metabolites tyrosol (1), salidroside (rhodioloside) (2), rosin (3), rosarin (4), rosavin (5), sachaliside 1 (6) and 4-methoxy-cinnamyl-O-beta-D-glucopyranoside (7), four compounds were isolated from aqueous methanol extract of the plant and identified as cinnamyl-(6'-O-beta-xylopyranosyl)-O-beta-glucopyranoside (8), 4-methoxy-cinnamyl-(6'-O-alpha-arabinopyranosyl)-O-beta-glucopyranoside (9), picein (10) and benzyl-O-beta-glucopyranoside (11) by UV, MS and NMR methods. Compounds 8 and 9 are new natural compounds whereas compounds 10 and 11 were isolated first time from R. rosea. Also the compounds 6 and 7 are isolated earlier only from the callus cultures of the plant but not from the differentiated plant. 相似文献