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排序方式: 共有214条查询结果,搜索用时 15 毫秒
91.
Partial Least Squares (PLS) is a wide class of regression methods aiming at modelling relationships between sets of observed variables by means of latent variables. Specifically, PLS2 was developed to correlate two blocks of data, the X‐block representing the independent or explanatory variables and the Y‐block representing the dependent or response variables. Lately, OPLS was introduced to further reduce model complexity by removing Y‐orthogonal sources of variation from X in the latent space, thus improving data interpretation through the generated predictive latent variables. Nevertheless, relationships between PLS2 and OPLS in case of multiple Y‐response have not yet been fully explored. With this perspective and taking inspiration from some basic mathematical properties of PLS2, we here present a novel and general approach consisting in a post‐transformation of PLS2 (ptPLS2), which results in a decomposition of the latent space into orthogonal and predictive components, while preserving the same goodness of fit and predictive ability of PLS2. Additionally, we discuss the application of ptPLS2 approach to two metabolomic data sets extracted from earlier published studies and its advantages in model interpretation as compared with the ‘standard’ PLS approach. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
92.
Simultaneous determination of aromatic amino acids in human blood plasma by capillary electrophoresis with UV‐absorption detection 下载免费PDF全文
Mauro Forteschi Salvatore Sotgia Stefano Assaretti Dionigia Arru Debora Cambedda Elisabetta Sotgiu Angelo Zinellu Ciriaco Carru 《Journal of separation science》2015,38(10):1794-1799
Phenylalanine, tyrosine, and tryptophan, also known as aromatic amino acids, are involved in many physiological and pathophysiological conditions and are indicative of the liver and kidney function. In this work, we describe a simple and accurate method for their simultaneous quantification, in a single capillary electrophoresis run. This method requires minimal sample manipulation, no derivatization procedures, and methyl tryptophan as internal standard. The human blood plasma sample was precipitated using sulfosalicylic acid and the supernatant was used for the analysis. All the analytes were baseline resolved within 16 min and detected at 200 nm using Tris phosphate 80 mmol/L at pH 1.4 as the background electrolyte. The proposed method showed good linearity (r = 0.998) and repeatability (intra‐assay RSD < 2.78%, interassay RSD < 5.4%) for all the analytes. The limit of quantification was 13 μmol/L for phenylalanine and 5 μmol/L for tyrosine and tryptophan. The method suitability was tested measuring aromatic amino acids level in 20 chronic kidney disease patients at basal level and after simvastatin/ezetimibe treatment. 相似文献
93.
Dr. Nicholas C. Nelson Dr. Linxiao Chen Dr. Debora Meira Dr. Libor Kovarik Dr. János Szanyi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(40):17810-17816
The application of single-atom catalysts (SACs) to high-temperature hydrogenation requires materials that thermodynamically favor metal atom isolation over cluster formation. We demonstrate that Pd can be predominantly dispersed as isolated atoms onto TiO2 during the reverse water–gas shift (rWGS) reaction at 400 °C. Achieving atomic dispersion requires an artificial increase of the absolute TiO2 surface area by an order of magnitude and can be accomplished by physically mixing a precatalyst (Pd/TiO2) with neat TiO2 prior to the rWGS reaction. The in situ dispersion of Pd was reflected through a continuous increase of rWGS activity over 92 h and supported by kinetic analysis, infrared and X-ray absorption spectroscopies and scanning transmission electron microscopy. The thermodynamic stability of Pd under high-temperature rWGS conditions is associated with Pd-Ti coordination, which manifests upon O-vacancy formation, and the artificial increase in TiO2 surface area. 相似文献
94.
Sergio Rojas-Buzo Benjamin Bohigues Christian W. Lopes Dbora M. Meira Mercedes Boronat Manuel Moliner Avelino Corma 《Chemical science》2021,12(29):10106
The Lewis/Brønsted catalytic properties of the Metal–Organic Framework (MOF) nodes can be tuned by simply controlling the solvent employed in the synthetic procedure. In this work, we demonstrate that Hf-MOF-808 can be prepared from a material with a higher amount of Brønsted acid sites, via modulated hydrothermal synthesis, to a material with a higher proportion of unsaturated Hf Lewis acid sites, via modulated solvothermal synthesis. The Lewis/Brønsted acid properties of the resultant metallic clusters have been studied by different characterization techniques, including XAS, FTIR and NMR spectroscopies, combined with a DFT study. The different nature of the Hf-MOF-808 materials allows their application as selective catalysts in different target reactions requiring Lewis, Brønsted or Lewis–Brønsted acid pairs.The Brønsted/Lewis acid properties of Hf-MOF-808 can be tuned by simply controlling the solvent employed in its synthesis, with direct catalytic implications on the activity and selectivity of organic reactions sensitive to the active site nature. 相似文献
95.
Given a sequence {An} of matrices An of increasing dimension dn with dk>dq for k>q, k,q∈N, we recently introduced the concept of approximating class of sequences (a.c.s.) in order to define a basic approximation theory for matrix sequences. We have shown that such a notion is stable under inversion, linear combinations, and product, whenever natural and mild conditions are satisfied. In this note we focus our attention on the Hermitian case and we show that is an a.c.s. for {f(An)}, if is an a.c.s. for {An}, {An} is sparsely unbounded, and f is a suitable continuous function defined on R. We also discuss the potential impact and future developments of such a result. 相似文献
96.
Rottava I Cortina PF Martello E Cansian RL Toniazzo G Antunes OA Oestreicher EG Treichel H de Oliveira D 《Applied biochemistry and biotechnology》2011,164(4):514-523
The main objective of this work is to present the optimization of the biotransformation of R-(+)-limonene and (−)-β-pinene aiming at the production of α-terpineol by strains of fungal and yeasts previously isolated
by our research group using the methodology of experimental design. New optimized experimental data on α-terpineol production
by the biotransformation of R-(+)-limonene and (−)-β-pinene using newly isolated microorganisms are reported in this work. Conversion of about 1,700 mg/L
was achieved when R-(+)-limonene was used as substrate and the newly isolated strain 05.01.35 as microorganism at the central point of the experimental
design, corresponding to a substrate concentration of 1.75%, mass of inoculum of 2 g, and substrate to ethanol volume ratio
of 1:1. The same experimental condition led to higher conversions when (−)-β-pinene was used as substrates and the strains
coded as 04.05.08 and 01.04.03 as microorganism. Here, conversions of about 770 mg/L were achieved. 相似文献
97.
Meira M Quintella CM Tanajura Ados S da Silva HR Fernando JD da Costa Neto PR Pepe IM Santos MA Nascimento LL 《Talanta》2011,85(1):430-434
Oxidation stability is an important quality parameter for biodiesel. In general, the methods used to evaluate the oxidation stability of oils and biodiesels are time-consuming. This work reports the use of spectrofluorimetry, a fast analytical technique, associated with multivariate data analysis as a powerful analytical tool to prediction of the oxidation stability. The prediction of the oxidation stability showed a good agreement with the results obtained by the EN14112 reference method Rancimat. The models presented high correlation (0.99276 and 0.97951) between real and predicted values. The R2 values of 0.98557 and 0.95943 indicated the accuracy of the models to predict the oxidation stability of soy oil and soy biodiesel, respectively. The residual distribution does not follow a trend with respect to the predicted variables indicating the good quality of the fits. 相似文献
98.
99.
Meiry E. Alvarenga Ana Karoline S. M. Valdo Leandro Ribeiro Jos Antonio Do Nascimento Neto Debora P. De Araujo Cleiton Moreira Da Silva ngelo De Ftima Felipe T. Martins 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(6):667-677
We report here for the first time a cocrystal of the so‐called neutral calix[4]tube, which is two tail‐to‐tail‐arranged and partially deprotonated tetrakis(carboxymethoxy)calix[4]arenes, including three sodium ions, with 2‐(thiophen‐2‐yl)‐1,3‐benzothiazole, namely trisodium bis(carboxymethoxy)bis(carboxylatomethoxy)calix[4]arene tris(carboxymethoxy)(carboxylatomethoxy)calix[4]arene–2‐(thiophen‐2‐yl)‐1,3‐benzothiazole–dimethyl sulfoxide–water (1/1/2/2), 3Na+·C36H30O122?·C36H31O12?·C11H7NS2·2C2H6OS·2H2O, which provides a new approach into the host–guest chemistry of inclusion complexes. Three packing polymorphs of the same benzothiazole with high Z′ (one with Z′ = 8 and two with Z′ = 4) were also discovered in the course of our desired cocrystallization. The inspection of these polymorphs and a previously known polymorph with Z′ = 2 revealed that Z′ increases as the strength of intermolecular contacts decreases. Also, these results expand the frontier of invoking calixarenes as a host for nonsolvent small molecules, besides providing knowledge on the rare formation of high‐Z′ packing polymorphs of simple molecules, such as the target benzothiazole. 相似文献
100.
Debora Santonocito Carmelo Puglia Cristina Torrisi Alessandro Giuffrida Valentina Greco Francesco Castelli Maria Grazia Sarpietro 《Molecules (Basel, Switzerland)》2021,26(16)
Glycyrrhetic acid (GA) and stearyl glycyrrhetinate (SG) are two interesting compounds from Glycyrrhiza glabra, showing numerous biological properties widely applied in the pharmaceutical and cosmetic fields. Despite these appreciable benefits, their potential therapeutic properties are strongly compromised due to unfavourable physical-chemical features. The strategy exploited in the present work was to develop solid lipid nanoparticles (SLNs) as carrier systems for GA and SG delivery. Both formulations loaded with GA and SG (GA-SLNs and SG-SLNs, respectively) were prepared by the high shear homogenization coupled to ultrasound (HSH-US) method, and we obtained good technological parameters. DSC was used to evaluate their thermotropic behaviour and ability to act as carriers for GA and SG. The study was conducted by means of a biomembrane model (multilamellar vesicles; MLVs) that simulated the interaction of the carriers with the cellular membrane. Unloaded and loaded SLNs were incubated with the biomembranes, and their interactions were evaluated over time through variations in their calorimetric curves. The results of these studies indicated that GA and SG interact differently with MLVs and SLNs; the interactions of SG-SLNs and GA-SLNs with the biomembrane model showed different variations of the MLVs calorimetric curve and suggest the potential use of SLNs as delivery systems for GA. 相似文献