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71.
Petr Kozlik Katarina Molnarova Tomas Jecmen Tomas Krizek Zuzana Bosakova 《Molecules (Basel, Switzerland)》2022,27(12)
Analysis of protein glycosylation is challenging due to micro- and macro-heterogeneity of the attached glycans. Hydrophilic interaction liquid chromatography (HILIC) is a mode of choice for separation of intact glycopeptides, which are inadequately resolved by reversed phase chromatography. In this work, we propose an easy-to-use model to predict retention time windows of glycopeptides in HILIC. We constructed this model based on the parameters derived from chromatographic separation of six differently glycosylated peptides obtained from tryptic digests of three plasma proteins: haptoglobin, hemopexin, and sex hormone-binding globulin. We calculated relative retention times of different glycoforms attached to the same peptide to the bi-antennary form and showed that the character of the peptide moiety did not significantly change the relative retention time differences between the glycoforms. To challenge the model, we assessed chromatographic behavior of fetuin glycopeptides experimentally, and their retention times all fell within the calculated retention time windows, which suggests that the retention time window prediction model in HILIC is sufficiently accurate. Relative retention time windows provide complementary information to mass spectrometric data, and we consider them useful for reliable determination of protein glycosylation in a site-specific manner. 相似文献
72.
Zintl Clusters as Wet‐Chemical Precursors for Germanium Nanomorphologies with Tunable Composition 下载免费PDF全文
Manuel M. Bentlohner Dr. Markus Waibel Patrick Zeller Dr. Kuhu Sarkar Prof. Dr. Peter Müller‐Buschbaum Priv.‐Doz. Dr. Dina Fattakhova‐Rohlfing Prof. Dr. Thomas F. Fässler 《Angewandte Chemie (International ed. in English)》2016,55(7):2441-2445
[Ge9]4? Zintl clusters are used as soluble germanium source for a bottom–up fabrication of Ge nanomorphologies such as inverse opal structures with tunable composition. The method is based on the assembly and oxidation of [Ge9]4? clusters in a template mold using SiCl4, GeCl4, and PCl3 leading to Si and P‐containing Ge phases as shown by X‐ray diffraction, Raman spectroscopy, and energy‐dispersive X‐ray analysis. [Ge9]4? clusters are retained using ethylenediamine (en) as a transfer medium to a mold after removal of the solvent if water is thoroughly excluded, but are oxidized to amorphous Ge in presence of water traces. 1H NMR spectroscopy reveals the oxidative deprotonation of en by [Ge9]4?. Subsequent annealing leads to crystalline Ge. As an example for wet‐chemical synthesis of complex Ge nanomorphologies, we describe the fabrication of undoped and P‐doped inverse opal‐structured Ge films with a rather low oxygen contents. The morphology of the films with regular volume porosity is characterized by SEM, TEM, and grazing incidence small‐angle X‐ray scattering. 相似文献
73.
Enis S. Džunuzović Jasna V. Džunuzović Aleksandar D. Marinković Milena T. Marinović-Cincović Katarina B. Jeremić Jovan M. Nedeljković 《European Polymer Journal》2012,48(8):1385-1393
Nanocomposites based on poly(methyl methacrylate) (PMMA) and TiO2 nanoparticles were synthesized by in situ radical polymerization of MMA in solution. The surface of TiO2 nanoparticles was modified with four gallic acid esters (octyl, decyl, lauryl and cetyl gallate). The content of gallates present on the surface of TiO2 was calculated from the TGA results. The influence of length of hydrophobic tail of amphiphilic alkyl gallates on dispersability of surface modified TiO2 nanoparticles in PMMA matrix, the molecular weight and glass transition temperature of PMMA, as well as the thermal stability of the prepared PMMA/TiO2 nanocomposites in nitrogen and air was investigated. The influence of content of TiO2 nanoparticles on the properties of these nanocomposites was also examined. The formation of a charge transfer complex between the surface Ti atoms and the gallates was confirmed by FTIR and UV spectroscopy. TEM micrographs of the PMMA/TiO2 nanocomposites revealed that degree of TiO2 aggregation can be significantly lowered by increasing the length of aliphatic part of the used gallates. The molecular weight of PMMA slightly decreases with the increase of TiO2 content, indicating that used TiO2 nanoparticles act as radical scavengers during the polymerization of MMA. The presence of surface modified TiO2 nanoparticles do not have an influence on the mobility of PMMA chain segments leading to the same values of glass transition temperature for all investigated samples. Thermal and thermo-oxidative stability of the PMMA matrix are improved by introducing TiO2 nanoparticles modified with gallates. 相似文献
74.
75.
Dragica M. Minić Maja T. Šumar-Ristović Đenana U. Miodragović Katarina K. Anđelković Dejan Poleti 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1167-1176
The kinetics of multi-step thermal degradation of Co(II) complex with N-benzyloxycarbonyl glycinato ligand [Co(N-Boc-gly)2(H2O)4]·2H2O, in non-isothermal conditions was studied using isoconversional and non-isoconversional methods. The degradation of complex
occurs in three well-separated steps involving the loss of water molecules in first step followed by two degradation steps
of dehydrated complex. The dependence of Arrhenius parameters on conversion degree showed that all observed steps of thermal
degradation are very complex, involving more than one elementary step, as can be expected for most solid-state heterogeneous
reactions with solid reactants and solid and gaseous products. It was shown that step 1, corresponding to the dehydration,
involves a series of competitive dehydration steps of differently bound water molecules complicated by diffusion. Second step
involves two parallel reactions related to the loss of two identical C6H5CH2O– ligand fragments complicated by the presence of products in gaseous state. Further degradation in step 3 corresponds to
complex process with a change in the limiting stage, in this case from the kinetic to the diffusion regime, connected with
the presence of gaseous products diffusing through the solid product. 相似文献
76.
77.
Bojan Markovic Sote Vladimirov Olivera Cudina Vladimir Savic Katarina Karljikovic-Rajic 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):930-935
A novel topical corticosteroid FA-21-PhP, 2-phenoxypropionate ester of fluocinolone acetonide, has been synthesized in order to investigate the possibility of decreasing systemic side effects. In this study model system for in vitro solvolytic reaction of FA-21-PhP has been analyzed in ethanol/water (90:10, v/v) with excess of sodium hydrogen carbonate. The selected conditions have been used as in vitro model for activation of corticosteroid C-21 ester prodrug. The second-order derivative spectrophotometric method (DS) using zero-crossing technique was developed for monitoring ternary mixture of solvolysis. Fluocinolone acetonide (FA) as a solvolyte was determined in the mixture in the concentration range 0.062–0.312 mM using amplitude 2D274.96. Experimentally determined LOD value was 0.0295 mM. The accuracy of proposed DS method was confirmed with HPLC referent method. Peak area of parent ester FA-21-PhP was used for solvolysis monitoring to ensure the initial stage of changes. Linear relationship in HPLC assay for parent ester was obtained in the concentration range 0.054–0.54 mM, with experimentally determined LOD value of 0.0041 mM. Investigated solvolytic reaction in the presence of excess of NaHCO3 proceeded via a pseudo-first-order kinetic with significant correlation coefficients 0.9891 and 0.9997 for DS and HPLC, respectively. The values of solvolysis rate constant calculated according to DS and HPLC methods are in good accordance 0.038 and 0.043 h?1, respectively. 相似文献
78.
Otevrel J Mandelova Z Pesko M Guo J Kralova K Sersen F Vejsova M Kalinowski DS Kovacevic Z Coffey A Csollei J Richardson DR Jampilek J 《Molecules (Basel, Switzerland)》2010,15(11):8122-8142
In this study, a series of twelve ring-substituted salicylanilides and carbamoylphenylcarbamates were prepared and characterized. The compounds were analyzed using RP-HPLC to determine lipophilicity. They were tested for their activity related to the inhibition of photosynthetic electron transport (PET) in spinach (Spinacia oleracea L.) chloroplasts. Moreover, their site of action in the photosynthetic apparatus was determined. Primary in vitro screening of the synthesized compounds was also performed against mycobacterial, bacterial and fungal strains. Several compounds showed biological activity comparable with or higher than the standards 3-(3,4-dichlorophenyl)-1,1-dimethylurea, isoniazid, penicillin G, ciprofloxacin or fluconazole. The most active compounds showed minimal anti-proliferative activity against human cells in culture, indicating they would have low cytotoxicity. For all compounds, the relationships between lipophilicity and the chemical structure are discussed. 相似文献
79.
Letica J Marković S Zirojević J Nikolić K Agbaba D 《Journal of AOAC International》2010,93(4):1121-1128
An RP-HPLC method for simultaneous separation and quantification of pantoprazole and its five main impurities in pharmaceutical formulations was developed and validated. The separation was accomplished on a Zorbax Eclipse XDB C18 column (5 microm particle size, 150 x 4.6 mm id) using a gradient with mobile phase A [buffer-acetonitrile (70 + 30, v/v)], and mobile phase B [buffer-acetonitrile (30 + 70, v/v)]. The buffer was 0.01 M ammonium acetate solution with addition of 1 mL triethylamine/L of the solution, adjusted to pH 4.5 with orthophosphoric acid. The eluent flow rate was 1 mL/min, the temperature of the column was 30 degrees C, and the eluate was monitored at 290 nm. Linearity (r = 0.999), recovery (97.6-105.8%), RSD (0.55-1.90%), and LOQ (0.099-1.48 microg/mL) were evaluated and found to be satisfactory. The proposed method can be used for simultaneous identification and quantification of the analyzed compounds in pharmaceutical formulations. 相似文献
80.
Dolezal M Palek L Vinsova J Buchta V Jampilek J Kralova K 《Molecules (Basel, Switzerland)》2006,11(4):242-256
Condensation of the corresponding chlorides of some substituted pyrazine-2-carboxylic acids (pyrazine-2-carboxylic acid, 6-chloropyrazine-2-carboxylic acid, 5-tert-butylpyrazine-2-carboxylic acid or 5-tert-butyl-6-chloropyrazine-2-carboxylic acid) with various ring-substituted aminothiazoles or anilines yielded a series of amides. The syntheses, analytical and spectroscopic data of thirty newly prepared compounds are presented. Structure-activity relationships between the chemical structures and the anti-mycobacterial, antifungal and photosynthesis-inhibiting activity of the evaluated compounds are discussed. 3,5-Bromo-4-hydroxyphenyl derivatives of substituted pyrazinecarboxylic acid, 16-18, have shown the highest activity against Mycobacterium tuberculosis H(37)Rv (54-72% inhibition). The highest antifungal effect against Trichophyton mentagrophytes, the most susceptible fungal strain tested, was found for 5-tert-butyl-6-chloro-N-(4-methyl-1,3-thiazol-2-yl)pyrazine-2-carboxamide (8, MIC =31.25 micromol x mL(-1)). The most active inhibitors of oxygen evolution rate in spinach Molecules 2006, 11,243 chloroplasts were the compounds 5-tert-butyl-6-chloro-N-(5-bromo-2-hydroxyphenyl)- pyrazine-2-carboxamide (27, IC(50) = 41.9 micromol x L(-1)) and 5-tert-butyl-6-chloro-N-(1,3- thiazol-2-yl)-pyrazine-2-carboxamide (4, IC50 = 49.5 micromol x L(-1)). 相似文献