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31.
32.
Zsuzsanna Éhen F. Giordano J. Sztatisz L. Jicsinszky Cs. Novők 《Journal of Thermal Analysis and Calorimetry》2005,80(2):419-424
Summary Thermoanalytical techniques (TG, DSC) are frequently used in the investigation of the thermal properties of cyclodextrins and their inclusion complexes. However, the above techniques do not provide information on the chemical composition of the evolved fragments upon the thermal decomposition. In this study &agr;-, &bgr;- and &ggr;-cyclodextrins and 4 methylated and 3 ethylated &bgr;-CD derivatives were investigated with a TG-MS combined thermoanalytical technique in order to get information about their fragmentation behaviour. By comparison of the TG/DTA curves, a different thermal behaviour was found for each of the native and the chemically modified cyclodextrins. Except for the water loss profiles and the solid-solid phase transformations, the thermal behaviour of the (investigated) native CDs do not show remarkable differences. However, the chemical modification of the native &bgr;-CD resulting in a new compound may change the strength of interactions between host and guest causing differences in the thermal stabilities of the derivatives. The mass spectrometry results supported the observed thermal differences and showed significant alterations in the fragmentation of ethylated and methylated compounds. The investigated natural CDs possess a very similar fragmentation profile, due to the common &agr;-D-glucopyranose building units. In the case of modified CDs characteristic signals of the substituents are present. 相似文献
33.
Jnos Csap Zsuzsanna Csap-Kiss Truman G. Martin Staffan Folestad Owe Orwar Anna Tivesten Sndor Nmethy 《Analytica chimica acta》1995,300(1-3):313-320
A method for the evaluation of the age of wool carpets and textiles was developed based on the age dependent alteration of amino acid composition of proteins. Samples of 23 wool carpets and textiles of known age, obtained from the Hungarian Museum of Industrial Arts and the Hungarian National Museum were analysed for amino acid content. Results were compared with data obtained for contemporary, untreated wool and wool carpet. The cysteic acid content of wool increases with age. The contemporary wool carpet contained 0.31 g of cysteic acid in 100 g of protein. Comparable figures were 1.87 g for a 550-year old carpet and 4.01–4.39 g for the 1600–1750 year old wool carpets. The cystine content decreased with age, the corresponding figures being 7.88, 3.12 and 1.19-0.97 g/100 g, respectively. Corresponding contents of methionine were 0.43, 0.21 and 0.20-0.00 g/ 100 g and for tyrosine 3.07, 2.11 and 0.20-0.00 g/100 g. Prediction equations were developed as linear regressions of the age of wool on cysteic acid, cystine and tyrosine contents. The 95% confidence intervals of estimates for two samples of unknown age were estimates plus or minus 30 and 38 years. 相似文献
34.
The complexes of heavy lanthanides and yttrium with 2,3-dimethoxybenzoic acid of the formula: Ln(C9h9O4)3·nH2O, where Ln=Tb(III), Dy(III), Ho(III), Er(III), Tm(III), Yb(III), Lu(III), Y(III), and n=2 for Tb(III), Dy(III), Ho(III), Y(III), n=1 for Er(III), Tm(III), n=0 for Yb(III) and Lu(III) have been synthesized and characterized by elemental analysis, ir spectroscopy, thermogravimetric
studies and x-ray diffraction measurements. The complexes have colours typical for Lnł3+ ions (Tb(III), Dy(III), Tm(III), Yb(III), Lu(III), Y(III) - white; Ho(III) - cream and Er(III) - salmon). the carboxylate
groups in these complexes are a symmetrical, bidentate, chelating ligand or tridentate chelating-bridging. they are isostructural
crystalline compounds characterized by low symmetry. On heating in air to 1273 k the 2,3-dimethoxybenzoates of heavy lanthanides
and yttrium decompose in various ways. The complexes of Tb(III), Dy(III), Ho(III), Er(III), Tm(III) and Y(III) at first dehydrate
to form anhydrous salts which next are decomposed to the oxides of the respective metals. 2,3-dimethoxybenzoates of Yb(III)
and Lu(III) are directly decomposed to oxides. When heated in nitrogen the hydrates also dehydrate in one step to form the
anhydrous complexes that next form the mixture of carbon and oxides of respective metals or their carbonates. The solubility
of the yttrium and heavy lanthanide 2,3-dimethoxybenzoates in water at 293 k is of the order of 10-2 mol dm-3.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
35.
Cs. Novák Zsuzsanna Éhen Marietta Fodor L. Jicsinszky Judit Orgoványi 《Journal of Thermal Analysis and Calorimetry》2006,84(3):693-701
Citronellol
and citronellyl acetate have been entrapped with α-, β- and γ-cyclodextrin
(CD). Evolved gas detection and TG-MS coupling was applied to prove the actual
inclusion complex formation between monoterpens and CDs. The terpene content
was determined by UV-VIS specrophotometry and RP-HPLC and the effect of storage
time on the terpene content was also investigated. The α- and γ-cyclodextrin
inclusion complexes showed higher thermal stabilities vs.
dynamic heating compared to the β-CD complexes. On the contray, the retention
of guest using β-cyclodextrin even after 10 years of storage was much
more pronounced. Experimental data other than 1:1 complex compositions are
assumed. Molecular modeling experiments also suggested multiple complex compositions. 相似文献
36.
Urinary concentrations of phenols or their metabolites have been used as biomarkers to assess the prevalence of exposure to
these compounds in the general population. Total urinary concentrations, which include both free and conjugated (glucuronide
and sulfated) forms of the compounds, are usually reported. From a toxicologic standpoint, the relative concentrations of
the free species compared with their conjugated analogs can be important because conjugation may reduce the potential biologic
activity of the phenols. In this study, we determined the percentage of glucuronide and sulfate conjugates of three phenolic
compounds, bisphenol A (BPA), 2,5-dichlorophenol (2,5-DCP), and 2-hydroxy-4-methoxybenzophenone (benzophenone-3, BP-3) in
30 urine samples collected between 2000 and 2004 from a demographically diverse group of anonymous adult volunteers. We used
a sensitive on-line solid phase extraction–isotope dilution–high performance liquid chromatography–tandem mass spectrometry
method. These three phenols were detected frequently in the urine samples tested. Only small percentages of the compounds
(9.5% for BPA, and 3% for 2,5-DCP and BP-3) were excreted in their free form. The percentage of the sulfate conjugate was
about twice that of the free compound. The glucuronide conjugate was the major metabolite, representing 69.5% (BPA), 89% (2,5-DCP),
and 84.6% (BP-3) of the total amount excreted in urine. These results are in agreement with those reported before which suggested
that BPA-glucuronide was an important BPA urinary metabolite in humans. To our knowledge, this is the first study describing
the distribution of urinary conjugates of BP-3 and 2,5-DCP in humans. 相似文献
37.
Lszl Ürgdi Lajos Kisfaludy gnes Patthy Ern Moravcsik Helga Tüds Zsuzsanna Tegyei Lszl
tvs 《Journal of heterocyclic chemistry》1989,26(1):129-132
The title compounds 4 were synthesized via the acid-catalyzed reaction of α-(acylaminooxy)carboxylic acid amides 6 with carbonyl compounds, and controlled catalytic hydrogenation of the resulting 2-benzyloxy-carbonyldihydro-2H-1,2,4-oxadiazin-5(6H)-ones 7 (R6 = PhCH2O). 相似文献
38.
The reaction of diethyl α-oxoethylphosphonate and diethyl oxobenzylphosphonate with diethyl phosphite, dimethyl phosphite, and diphenylphosphine oxide affords, depending on the substrates and conditions (nature and quantity of the amine catalyst, temperature, and solvent), the Pudovik adduct and/or the corresponding >P(O)–CH–O–P(O)< product formed by rearrangement. The nature of the substituent on the central carbon atom (a methyl or phenyl group) influences the inclination for the rearrangement. The asymmetric products (either adducts or rearranged species) with different P(O)Y functions (Y = RO or Ph) exhibit interesting NMR features. 相似文献
39.
40.
Zsuzsanna Horváth Alfréd Menyhárd Petar Doshev Markus Gahleitner József Varga Cornelia Tranninger Béla Pukánszky 《Journal of Thermal Analysis and Calorimetry》2014,118(1):235-245
The chain regularity of isotactic polypropylene (iPP) homopolymer and random copolymers was characterized by different thermal fractionation methods in this study. Different stepwise temperature programs were applied in a calorimeter (DSC), in order to develop a method which is significantly faster than stepwise isothermal segregation technique (SIST) and provides reliable information about the chain regularity of iPP. Our studies prove that self-seeding accelerates the crystallization process during annealing in SSA–DSC experiments (successive self-nucleation and annealing). Consequently, the time of isothermal steps can be shortened significantly in the SSA–DSC method. On the other hand, we found that step time should not be too short if the goal of the measurement is the determination of average chain regularity. Our results clearly indicate that both the experimental conditions and the evaluation technique influence the obtained results. A standard experimental procedure is proposed for reliably determining the average chain regularity of iPP. The length of the SSA–DSC temperature program developed in this study is much shorter compared to that of the conventional SIST measurements used recently for such experiments. The proposed SSA–DSC program makes the reliable characterization of a large number of samples on an acceptable timescale possible. 相似文献