全文获取类型
| 收费全文 | 197篇 |
| 免费 | 2篇 |
专业分类
| 化学 | 173篇 |
| 数学 | 15篇 |
| 物理学 | 11篇 |
出版年
| 2023年 | 1篇 |
| 2022年 | 7篇 |
| 2021年 | 7篇 |
| 2020年 | 4篇 |
| 2019年 | 3篇 |
| 2018年 | 7篇 |
| 2017年 | 9篇 |
| 2016年 | 5篇 |
| 2015年 | 15篇 |
| 2014年 | 13篇 |
| 2013年 | 21篇 |
| 2012年 | 14篇 |
| 2011年 | 13篇 |
| 2010年 | 7篇 |
| 2009年 | 10篇 |
| 2008年 | 15篇 |
| 2007年 | 11篇 |
| 2006年 | 11篇 |
| 2005年 | 8篇 |
| 2004年 | 2篇 |
| 2003年 | 5篇 |
| 2002年 | 3篇 |
| 2001年 | 1篇 |
| 2000年 | 2篇 |
| 1999年 | 1篇 |
| 1997年 | 1篇 |
| 1993年 | 1篇 |
| 1986年 | 1篇 |
| 1974年 | 1篇 |
排序方式： 共有199条查询结果，搜索用时 0 毫秒
21.
Hunt DW Boivin WA Fairley LA Jovanovic MM King DE Salmon RA Utting OB 《Photochemistry and photobiology》2006,82(5):1292-1300
The proinflammatory cytokine interleukin-20 (IL-20) may exert the majority of its activity in the skin. We examined the effect of various treatments including several forms of phototherapy on IL-20 expression using cultured normal human epithelial keratinocytes (NHEK). Broadband UVB light, recombinant (r) IL-1 and rIL-8 increased, while hydrocortisone reduced, NHEK supernatant IL-20 levels. Elevation of NHEK IL-20 mRNA and maximal supernatant IL-20 levels occurred with a UVB light dose (40 mJ cm(-2)) that reduced cell viability by approximately 50%. While this UVB light dose also elevated supernatant IL-1 alpha and IL-8 levels, antibody neutralization studies indicated that neither of these cytokines was directly responsible for this increase in IL-20 expression. However, the elevation in IL-20 levels was fully inhibited by the p38 mitogen-activated protein kinase (MAPK) inhibitor SB-203580, suggesting involvement of this stress signaling pathway in this UVB light response. Photodynamic therapy (PDT) with the photosensitizer lemuteporfin, UVA light, cisplatin, lipopolysaccharide (LPS), tumor necrosis factor-alpha (TNF-alpha) or recombinant interferon-gamma (rIFN-gamma) either had little effect or decreased NHEK supernatant IL-20 levels. Reduced IL-20 levels paralleled the cytotoxic actions of PDT, UVA light or cisplatin and the antiproliferative effect of rIFN-gamma. Neither rIL-20 supplementation nor anti-IL-20 antibody treatments affected cell viability indicating that soluble IL-20 did not affect the short-term survival of UVB light-irradiated NHEK. Stimulation of IL-20 expression in keratinocytes by UVB light suggests that this cytokine might participate in skin responses to this ever-present environmental factor and potentially has a role in UV light-associated dermatoses. 相似文献
22.
Miroslava Malenovska Marco Litschauer Marie-Alexandra Neouze Ulrich Schubert Anna Peled Jean-Paul Lellouche 《Journal of organometallic chemistry》2009,694(7-8):1076-1080
Non-agglomerated hybrid particles of 200 nm diameter with an outer metal oxide shell were prepared by reacting the COOH groups of poly((S)-N-dicarbazolyl-lysine)-covered silica particles with metal alkoxides, such as titanium, zirconium and aluminum alkoxides, followed by sol–gel processing. With tetraethoxysilane (Si(OEt)4), the silica particle core was growing rather than forming an external metal oxide shell, as observed for the other tested metal alkoxides. 相似文献
23.
Gordana &#x;iri&#x;‐Marjanovi&#x; Miroslava Trchov Jaroslav Stejskal 《Journal of Raman spectroscopy : JRS》2008,39(10):1375-1387
The structural changes of aniline oligomers and polyaniline, associated with oxidation of aniline with ammonium peroxydisulfate in aqueous solutions without any added acid, were studied. The reaction was quenched at various times and the films deposited on silicon windows have been studied in detail by Raman spectroscopy, at excitation wavelengths 633 and 514 nm. The presence of substituted phenazine structural units, in addition to ordinary benzenoid, quinonoid, and semiquinonoid structures, has been proved by the appearance of characteristic Raman bands at 1645–1630, 1420–1400, 1380–1365, ∼575, and ∼415 cm−1. The remarkable differences of the Raman spectra of oligoanilines, precipitated in the first phase of oxidative polymerization, and polyaniline nanotubes and nanorods, formed in the second stage of reaction, are discussed. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
24.
Václav M. Bierhanzl Miroslava Bursová Martin Ston Radomír Ĉabala Gabriela Seydlová 《Chemical Papers》2016,70(10):1309-1315
A rapid and selective GC-MS method was optimised for the simultaneous analysis of fatty acids, phosphoethanolamine, phosphoglycerol and phosphoserine, which comprise the polar headgroups of phospholipids. Enzymatic hydrolysis was used for sample preparation to selectively release fatty acids and prevent cleavage of the phosphoester bonds of the polar headgroups. A two-step consecutive derivatisation of the fatty acids and polar headgroups was applied to enable the simultaneous analysis of the selected analytes. The method was tested on samples of cell membrane phospholipids of Bacillus subtilis, a microbe with a broad spectrum of fatty acids. This approach can accelerate and simplify biotechnological research and quality control. The experimental conditions were optimised using a chemometric approach denoted as experimental design. 相似文献
25.
26.
Veronika Valkov Hana úranov Nenad L. Vukovic Milena Vukic Maciej Kluz Miroslava Ka
niov 《Molecules (Basel, Switzerland)》2022,27(10)
The possibilities of the practical utilization of essential oils (EOs) from various plant species in the food industry have attracted the attention of the scientific community. Following our previous studies, the antifungal activities of three further commercial EOs, Melaleuca armillaris subsp. armillaris (rosalina; REO), Melaleuca quinquenervia (niaouli; NEO), and Abies alba (fir; FEO), were evaluated in the present research in respect to their chemical profiles, over four different concentrations, 62.5 μL/L, 125 μL/L, 250 μL/L, and 500 μL/L. The findings revealed that the major compounds of REO, NEO, and FEO were linalool (47.5%), 1,8-cineole (40.8%), and α-pinene (25.2%), respectively. In vitro antifungal determinations showed that the inhibition zones of a Penicillium spp. mycelial growth ranged from no inhibitory effectiveness (00.00 ± 00.00 mm) to 16.00 ± 1.00 mm, indicating a very strong antifungal activity which was detected against P. citrinum after the highest REO concentration exposure. Furthermore, the in situ antifungal efficacy of all EOs investigated was shown to be dose-dependent. In this sense, we have found that the highest concentration (500 µL/L) of REO, NEO, and FEO significantly reduced (p < 0.05) the growth of all Penicillium strains inoculated on the bread, carrot, and potato models. These results indicate that the investigated EOs may be promising innovative agents in order to extend the shelf life of different types of food products, such as bread, carrot and potato. 相似文献
27.
Marek Kovr Alica Navrtilov Renata Kollthov Anna Trakovick Miroslava Pogajov 《Molecules (Basel, Switzerland)》2022,27(13)
Acrylamide (AA), is a chemical with multiple industrial applications, however, it can be found in foods that are rich in carbohydrates. Due to its genotoxic and cytotoxic effects, AA has been classified as a potential carcinogen. With the use of spectrophotometry, ICP-OES, fluorescence spectroscopy, and microscopy cell growth, metabolic activity, apoptosis, ROS production, MDA formation, CAT and SOD activity, ionome balance, and chromosome segregation were determined in Schizosaccharomyces pombe. AA caused growth and metabolic activity retardation, enhanced ROS and MDA production, and modulated antioxidant enzyme activity. This led to damage to the cell homeostasis due to ionome balance disruption. Moreover, AA-induced oxidative stress caused alterations in the cell cycle regulation resulting in chromosome segregation errors, as 4.07% of cells displayed sister chromatid non-disjunction during mitosis. Ascorbic acid (AsA, Vitamin C), a strong natural antioxidant, was used to alleviate the negative impact of AA. Cell pre-treatment with AsA significantly improved AA impaired growth, and antioxidant capacity, and supported ionome balance maintenance mainly due to the promotion of calcium uptake. Chromosome missegregation was reduced to 1.79% (44% improvement) by AsA pre-incubation. Results of our multiapproach analyses suggest that AA-induced oxidative stress is the major cause of alteration to cell homeostasis and cell cycle regulation. 相似文献
28.
Milena D. Vukic Ana D. Obradovic Nenad L. Vukovic Miroslava Ka
niov Predrag M. Djurdjevic Gorica T. Djelic Milos M. Matic 《Molecules (Basel, Switzerland)》2022,27(18)
It is well known that abiotic components can affect biosynthetic pathways in the production of certain volatile compounds. The aim of this study was to compare the chemical composition of essential oils obtained from Orlaya grandiflora (L.) Hoffm. collected from two localities in Serbia (continental climate, OG1) and Montenegro (Mediterranean climate, OG2) and to assess their antitumor potential on the human colon cancer HCT-116 and breast cancer MDA-MB-231 cell lines. EOs obtained by hydrodistillation were analyzed using GC-MS and GC-FID methods. The results indicate considerable differences in the chemical compositions of the two samples. Although in both samples the main class of volatiles observed was sesquiterpenes (47.5% for OG1 and 70.1% for OG2), the OG1 sample was characterized by a high amount of monoterpene hydrocarbons (29.3%), and sesquiterpene germacrene D (29.5%) as the most abundant compound. On the other hand, the OG2 sample contained a high quantity of oxygenated sesquiterpenes (20.6%), and β-elemene (22.7%) was the major constituent. The possible antitumor mechanisms of these EOs in the HCT-116 and MDA-MB-231 cell lines were examined by means of cell viability, apoptosis, redox potential, and migratory capacity. The antiviability potential appeared to be dose dependent, since the results showed that both EOs decreased the viability of the tested cells. Stronger antitumor effects were shown in MDA-MB-231 cells after short-term treatment, especially at the highest applied concentration, where the percentage of viability was reduced by over 40%. All tested concentrations of EOs exhibited proapoptotic activity and elevated activity of caspase-3 in a dose- and time-dependent manner. The results also showed decreased concentrations of superoxide anion radical in the treated cells, which indicates their significant antioxidative role. Long-term treatments showed mild recovery effects on cell viability in both cell lines, probably caused by the balancing of redox homeostasis. Elevated levels of nitrites indicate high levels of nitric oxide (NO) production and suggest its higher bioavailability due to the antioxidative environment. The tested EOs also induced a drop in migratory capacity, especially after short-time treatments. Taken together, these results suggest considerable antitumor activity of both EOs, which could have potential therapeutic applications. 相似文献
29.
Andrea Fülöpová Peter Magdolen Miroslava Károlyiová Ivica Sigmundová Pavol Zahradník 《Journal of heterocyclic chemistry》2013,50(3):563-567
A six‐step synthesis of the unsymmetrical trimethylbenzotristhiazole has been developed. Starting from 2‐methylbenzothiazole following nitration, reduction, acetylation, thionation, and twofold cyclization, the desired trimethylbenzotristhiazole was obtained in good yield. Its condensation with donor‐substituted benzaldehydes presents the way to new octupolar chromophores. The attempt to synthesize such benzotristhiazole from dinitroaniline failed; this procedure afforded a new benzimidazole derivative. 相似文献
30.
Bober Patrycja Stejskal Jaroslav Trchov&#; Miroslava Proke&#; Jan 《Journal of Solid State Electrochemistry》2011,15(11):2361-2368
The oxidation of aniline with silver nitrate in 1 mol L−1 acetic acid at 20 °C yielded a composite of two conducting components, polyaniline and silver; the acceleration with 1 mol% of p-phenylenediamine is needed for efficient synthesis. The yield and molecular weight increased when aniline was copolymerized with 10 mol% p-phenylenediamine. Such product displayed metallic conductivity below 180 K and semiconductor type above this temperature. As the result, the conductivity was the same at 100 and 300 K. The oxidation of p-phenylenediamine alone with silver nitrate also produced a conducting composite having the conductivity of 1,750 S cm−1 despite the assumed nonconductivity of poly(p-phenylenediamine). The present study demonstrates that all oxidations proceeded also in frozen reaction mixtures at −24 °C, i.e., in the solid state. In most cases, molecular weights of polymer component increased, the conductivity of composites with silver improved, to 2,990 S cm−1 for poly(p-phenylenediamine)–silver, and remained high after deprotonation with 1 mol L−1 ammonium hydroxide.
相似文献