全文获取类型
收费全文 | 191篇 |
免费 | 25篇 |
专业分类
化学 | 114篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 68篇 |
物理学 | 28篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 9篇 |
2017年 | 6篇 |
2016年 | 24篇 |
2015年 | 14篇 |
2014年 | 13篇 |
2013年 | 21篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 22篇 |
2009年 | 14篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有216条查询结果,搜索用时 15 毫秒
51.
Tibor Béres Marek Zatloukal Jiří Voller Percy Niemann Marie Christin Gahsche Petr Tarkowski Ondřej Novák Jan Hanuš Miroslav Strnad Karel Doležal 《Analytical and bioanalytical chemistry》2010,398(5):2071-2080
We describe here a new reversed-phase high-performance liquid chromatography with mass spectrometry detection method for quantifying
intact cytokinin nucleotides in human K-562 leukemia cells. Tandem mass spectrometry was used to identify the intracellular
metabolites (cytokinin monophosphorylated, diphosphorylated, and triphosphorylated nucleotides) in riboside-treated cells.
For the protein precipitation and sample preparation, a trichloroacetic acid extraction method is used. Samples are then back-extracted
with diethyl ether, lyophilized, reconstituted, and injected into the LC system. Analytes were quantified in negative selected
ion monitoring mode using a single quadrupole mass spectrometer. The method was validated in terms of retention time stabilities,
limits of detection, linearity, recovery, and analytical accuracy. The developed method was linear in the range of 1–1,000 pmol
for all studied compounds. The limits of detection for the analytes vary from 0.2 to 0.6 pmol. 相似文献
52.
Lukáš Chytil Josef Cvačka Věra Marešová Branislav Štrauch Jiří Widimský Jr Martin Štícha Ondřej Slanař 《Journal of mass spectrometry : JMS》2010,45(10):1179-1185
Rilmenidine is an alpha 2 adrenoreceptor agonist used in the treatment of mild and moderate hypertension. In this study, a fast and accurate liquid chromatographic method with tandem mass spectrometric detection has been validated in order to assure quantification of rilmenidine in human serum. The fragmentation pathway of protonated rilmenidine was studied using high‐resolution mass spectrometry (HRMS). This study compared selectivity, linearity, accuracy, precision, extraction efficiency, matrix effect and sensitivity using common liquid–liquid extraction (LLE) and solid‐phase extraction (SPE) procedures. The limit of quantitation for both extraction techniques was 0.1 ng/ml. Several differences between the LLE and SPE have been observed in terms of linearity, accuracy, precision and matrix effect. Additionally, the advantages of SPE included less manual work load and increased recovery of rilmenidine in human serum to approximately 80% (LLE, 57%). The developed method involving SPE was found to be accurate (relative error (RE) < 5%), reproducible (relative standard deviation, RSD < 7%), robust and suitable for quantitative analysis of rilmenidine in serum samples obtained from patients under antihypertensive treatment. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
53.
Tereza-Markéta Durd'áková Zdeněk Hrdlička Martin Král Peter M. Budd Wayne J. Harrison Karel Friess Ondřej Vopička 《Journal of polymer science. Part A, Polymer chemistry》2024,62(9):1781-1788
Glassy polymers stiffen or soften when exposed to volatile compounds, depending on the specific combination of polymer compound and the specimen history. Relevant to the long-term applicability of the separation membranes, three common membrane glassy polymers are studied in this work. Freshly prepared and 2-years aged films from cellulose triacetate (CTA), poly[1-(trimethylsilyl)-1-propyne] (PTMSP), and the archetypal polymer of intrinsic microporosity (PIM-1) were tested using isothermal Dynamic Mechanical Analysis (DMA) at varied vapor activity. Vapors of organic compounds, in which the polymers do and do not dissolve in the liquid phase (solvents and nonsolvents), were studied at 40 °C, namely: dichloromethane (DCM, solvent), p-xylene (solvent for PTMSP and PIM-1), and methanol (nonsolvent). Functional groups of the mer units sensitive to the dissolution were identified using Raman spectroscopy. All aged films were stiffer than the freshly prepared ones. Stiffening prevailed for most freshly prepared film-vapor pairs at low vapor saturations (activity < ≈0.4), except CTA and PIM-1 in nonsolvent methanol vapors. Softening prevailed for the aged films and higher vapor saturations (activity > ≈0.6). Vapors of the solvents and nonsolvents did not show the expectable prevalence of softening and stiffening, respectively. Physical aging influenced the stiffening and softening of polymer glasses expectably. 相似文献
54.
Ondřej F. K. Kalenda 《Israel Journal of Mathematics》2007,162(1):157-181
We study the notion of (I)-generating introduced by V. Fonf and J. Lindendstrauss and a related notion of (I)-envelope. As
a consequence of our results we get an easy proof of the James characterization of weak* compactness in Banach spaces with
weak angelic dual unit ball and an easy proof of the James characterization of reflexivity within a large class of spaces.
We also show by an example that the general James theorem cannot be proved by this method.
The work is a part of the research project MSM 0021620839 financed by MSMT and partly supported by the research grant GA ČR
201/06/0018. 相似文献
55.
Jiří Bajer Jan Peřina Ondřej Haderka Adam Miranowicz 《Czechoslovak Journal of Physics》2000,50(6):717-726
Sub-Poissonian light in the third-harmonic generation process is studied numerically and analytically. Special regime exhibiting
the time-stable maximum sub-Poissonian behaviour with the Fano factorF ≈ 0.81 is found and analyzed. Theoretical prediction of the Fano factor and explanation of the extraordinary time stability
of the sub-Poissonian behaviour are given using the semiclassical method of classical trajectories. 相似文献
56.
57.
The suitability of the Guggenheim–Anderson–De Boer (GAB) model for the parameterization of gas sorption isotherms and their dependences on temperature is explored. The GAB model implies that molecules adsorb on inner surfaces of the polymer in multilayers, which contrasts with the assumptions of the classical Dual Mode Sorption (DMS) model which implies the simultaneous occurrence of Henry‐like dissolution and Langmuir's case I adsorption. The GAB model shows similar efficacy of the parameterization of the gas sorption isotherms in polymers as the DMS model. The isosteric heat of adsorption shows clear dependence on relative surface coverage for carbon dioxide sorption in cellulose acetate, polyethylene terephthalate, and the first polymer of intrinsic microporosity (PIM‐1), thus allowing for the occurrence of adsorption multilayers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1490–1495 相似文献
58.
Hanuš Seiner Ondřej Glatz Michal Landa 《International Journal of Solids and Structures》2011,48(13):2005-2014
A detailed morphology of the twinned-to-detwinned interface in microstructure of 2H-martensite phase of the Cu–Al–Ni shape memory alloy is observed by optical methods (optical microscopy, white-light interferometry). Based on these observations, a finite element model of the transition layer is constructed and applied to calculate the elastic stress distribution inside the observed microstructure. The results show that the real micromorphology does not correspond to the minimum of the sum of the elastic and surface energy, and that the maxima of the stress field necessary for the existence of this morphology are comparable to the elasticity limits of the 2H-martensite. 相似文献
59.
Ondřej Kaman Tereza Dědourková Jakub Koktan Jarmila Kuličková Miroslav Maryško Pavel Veverka Radim Havelek Karel Královec Karolína Turnovcová Pavla Jendelová Adam Schröfel Ladislav Svoboda 《Journal of nanoparticle research》2016,18(4):100
Magnetic oxide nanoparticles provide a fascinating tool for biological research and medicine, serving as contrast agents, magnetic carriers, and core materials of theranostic systems. Although the applications rely mostly on iron oxides, more complex oxides such as perovskite manganites may provide a much better magnetic performance. To assess the risk of their potential use, in vitro toxicity of manganite nanoparticles was thoroughly analysed and compared with another prospective system of Mn–Zn ferrite nanoparticles. Magnetic nanoparticles of La0.63Sr0.37MnO3 manganite were prepared by two distinct methods, namely the molten salt synthesis and the traditional sol–gel route, whereas nanoparticles of Mn0.61Zn0.42Fe1.97O4 ferrite, selected as a comparative material, were synthesized by a new procedure under hydrothermal conditions. Magnetic cores were coated with silica and, moreover, several samples of manganite nanoparticles with different thicknesses of silica shell were prepared. The size-fractionated and purified products were analysed using transmission electron microscopy, dynamic light scattering, measurement of the zeta-potential dependence on pH, IR spectroscopy, and SQUID magnetometry. The silica-coated products with accurately determined concentration by atomic absorption spectroscopy were subjected to a robust evaluation of their cytotoxicity by four different methods, including detailed analysis of the concentration dependence of toxicity, analysis of apoptosis, and experiments on three different cell lines. The results, comparing two manganese-containing systems, clearly indicated superior properties of the Mn–Zn ferrite, whose silica-coated nanoparticles show very limited toxic effects and thus constitute a promising material for bioapplications. 相似文献
60.
Inside Back Cover: Cross‐Aldol Reaction of Isatin with Acetone Catalyzed by Leucinol: A Mechanistic Investigation (Chem. Eur. J. 34/2015) 下载免费PDF全文