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1.
In this work, a capillary electrophoresis (CE) method using indirect UV detection (214nm) for the simultaneous determination of monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), diethylethanolamine (DEEA), monocyclohexylamine (MCHA) and dicyclohexylamine (DCHA) in water/ethanol extracts of wrapping materials containing volatile corrosion inhibitors (VCIs) was described. A running buffer consisting of 0.010 molL(-1) imidazole, 0.010 molL(-1) 2-hydroxyisobutyric acid (HIBA) and 0.010 molL(-1) 18-crown-6 ether enabled separation of the analytes in less than 7 min. A few method validation parameters were determined revealing good migration time repeatability (<0.7% RSD) and area repeatability (< 1.8% RSD). Limits of detection were in the range of 0.52-1.54 mg L(-1). Recovery values were in the range of 94.8-100.9%. The methodology was successfully applied to the analysis of three commercial products (VCI treated paper, foam and plastic). The concentration of amines in these materials varied from 0.050 to 22.3% (w/w). 相似文献
2.
The disrupting effect of three different ionic carbohydrates (xanthan, pectin and gum arabic) on the formation of tannin-protein insoluble aggregates was assessed by nephelometry using bovine serum albumin (BSA) and several procyanidin fractions previously extracted from grape seeds. The presence in solution of any of the carbohydrates studied was found to restrain the formation of insoluble protein-tannin aggregates for every procyanidin fraction used. Xanthan was the most effective carbohydrate, whereas gum arabic was the least effective. The present work has revealed that the disrupting effect of carbohydrates is quite different depending on the procyanidin structure complexity. In general, the three carbohydrates studied revealed a similar trend in that their disrupting effect on tannin-BSA aggregate formation decreased with increase of the procyanidin degree of polymerization. 相似文献
3.
Elisabete Curti Douglas de Britto Srgio Paulo Campana‐Filho 《Macromolecular bioscience》2003,3(10):571-576
N,N,N‐trimethylchitosan (TMC) was prepared by reacting purified chitosan with iodomethane, in the presence of sodium hydroxide, water and sodium iodide, at room temperature. The reaction medium was N‐methyl‐2‐pyrrolidone. Different samples of TMC were obtained by adding to the reaction medium a fixed volume (5.5 mL) of aqueous NaOH solutions at different concentrations (15, 20, 30 and 40 wt.‐%) and carrying out the reactions for 9 or 24 h. The features observed in the 1H and 13C NMR spectra of these chitosan derivatives, in respect of the chemical shift, number and relative intensity of the signals, depended strongly on the excess of NaOH and H3CI added to the reaction medium, but when the lowest excess was employed, the characteristics of the derivative were not affected by the reaction time to the same extent. The average degree of quaternization of these N‐methylated derivatives of chitosan ranged from 10.5% to 44.8%, according to the reaction conditions. Increasing the excess of NaOH, in reactions carried out for 9 h, resulted in TMC samples with progressively higher content of trimethylated sites however, the reaction yields were correspondingly lower and O‐alkylation was favored in these cases.
4.
Bruno V. M. Rodrigues Elina Heikkilä Elisabete Frollini Pedro Fardim 《Cellulose (London, England)》2014,21(3):1289-1303
Bio-based films were prepared from LiCl/DMAc solutions containing sisal cellulose esters (acetates, butyrates and hexanoates) with different degrees of substitution (DS 0.7–1.8) and solutions prepared with the cellulose esters and 20 wt% sisal cellulose. A novel approach for characterizing the surface morphology utilized field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and contact angle analysis. XPS and ToF-SIMS were a powerful combination while investigating both the ester group distribution on the surface and effects of cellulose content on the film. The surface coverage by ester aliphatic chains was estimated using XPS measurements. Fibrous structures were observed in the FE-SEM images of the cellulose and bio-based films, most likely because the sisal cellulose chains aggregated during dissolution in LiCl/DMAc. Therefore, the cellulose aggregates remained after the formation of the films and removal of the solvent. The XPS results indicated that the cellulose loading on the longer chain cellulose esters films (DS 1.8) increased the surface coverage by ester aliphatic chains (8.2 % for butyrate and 45 % for hexanoate). However, for the shortest ester chains, the surface coverage decreased (acetate, 42 %). The ToF-SIMS analyses of cellulose acetate and cellulose hexanoate films (DS 1.8) revealed that the cellulose ester groups were evenly distributed across the surface of the films. 相似文献
5.
Brunner CT Baran ET Pinho ED Reis RL Neves NM 《Colloids and surfaces. B, Biointerfaces》2011,84(2):77-507
Poly(butylene succinate) (PBSu), poly(butylene succinate-co-adipate) (PBSA) and poly(butylene terephthalate-co-adipate) (PBTA) microcapsules were prepared by the double emulsion/solvent evaporation method. The effect of polymer and poly(vinyl alcohol) (PVA) concentration on the microcapsule morphologies, drug encapsulation efficiency (EE) and drug loading (DL) of bovine serum albumin (BSA) and all-trans retinoic acid (atRA) were all investigated. As a result, the sizes of PBSu, PBSA and PBTA microcapsules were increased significantly by varying polymer concentrations from 6 to 9%. atRA was encapsulated into the microcapsules with an high level of approximately 95% EE. The highest EE and DL of BSA were observed at 1% polymer concentration in values of 60 and 37%, respectively. 4% PVA was found as the optimum concentration and resulted in 75% EE and 14% DL of BSA. The BSA release from the capsules of PBSA was the longest, with 10% release in the first day and a steady release of 17% until the end of day 28. The release of atRA from PBSu microcapsules showed a zero-order profile for 2 weeks, keeping a steady release rate during 4 weeks with a 9% cumulative release. Similarly, the PBSA microcapsules showed a prolonged and a steady release of atRA during 6 weeks with 12% release. In the case of PBTA microcapsules, after a burst release of 10% in the first day, showed a parabolic release profile of atRA during 42 days, releasing 36% of atRA. 相似文献
6.
Several 2,5-disubstituted oxazole-4-carboxylates were prepared in high yields from the methyl esters of N-acyl-β-halodehydroaminobutyric acid derivatives by treatment with a 2% solution of DBU in acetonitrile. The scope of this reaction was investigated and it was found that dehydrodipeptides having a β-bromodehydroaminobutyric acid residue gave the corresponding oxazoles in good yields. The photophysical properties of some of the oxazoles prepared were studied in four solvents of different polarity. All compounds have reasonable high fluorescence quantum yields and a moderate solvent sensitivity, which makes them good candidates to be used as fluorescent probes. One of the fluorescent oxazoles prepared was inserted after cleavage of the methyl ester into two model peptides using a conventional solution phase strategy. The photophysical properties of the labelled peptides were studied in ethanol and water and compared with those of the oxazole. The results obtained showed that the oxazole maintains a good fluorescence level and the same solvent sensitivity when linked to a peptide chain. 相似文献
7.
Martins MA Santos C Almeida MM Costa ME 《Journal of colloid and interface science》2008,318(2):210-216
Hydroxyapatite (HAP) particles with different morphologies were precipitated from homogeneous calcium/citrate/phosphate solutions at physiological temperature. Small variations of the starting solution pH in the range 7.4相似文献
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10.
Natallia Torapava Henrik Ramebäck Enzo Curti Petra Lagerkvist Christian Ekberg 《Journal of Radioanalytical and Nuclear Chemistry》2014,301(2):545-553
In this work, the kinetics of barium sulfate recrystallization has been studied in acidic 0.01 mol dm?3 sodium sulfate solution using 223Ra and 133Ba tracers at very low total radium concentration, i.e. less than 10?13 mol dm?3. It was found that the system follows the homogeneous recrystallization model and that recrystallization rates, inferred by the decrease of 223Ra and 133Ba in the aqueous solution, are fast. Therefore, even at very low concentrations, below the solubility limit, radium will be retained by barium sulfate—a mineral present in the deep underground repository. 相似文献