全文获取类型
收费全文 | 79篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 45篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 7篇 |
物理学 | 17篇 |
无线电 | 10篇 |
出版年
2022年 | 2篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 1篇 |
2005年 | 5篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有81条查询结果,搜索用时 468 毫秒
1.
D. Minić Nada Štrbac I. Mihajlović Ž. Živković 《Journal of Thermal Analysis and Calorimetry》2005,82(2):383-388
In this paper, the results of copper-lead matte investigations are presented. Investigated copper-lead matte is intermediate
product of the lead production in TREPCA-Zvečan. In the first part of the paper characterization of starting material is presented,
consisting of: chemical composition analysis (XRQ), scanning electron microscopy (SEM) and diffractometry (XRD). Thermal properties
of investigated matte were determined using differential thermal analysis (DTA) at characteristic temperatures. Using results
of induced analysis, mechanism of matte oxidation process was determined. In the second part of the paper kinetic parameters
describing oxidative roasting of copper-lead matte are presented. For activation energy calculations, non-isothermal methods
defined by Kissinger and Ozawa were used [1, 2]. Kinetic equation describing oxidation process was determined using Sharps
method of reduced half time of reaction [3]. 相似文献
2.
The mechanism of the addition of carbonyl compounds to digermenes was investigated by examining the reaction between tetramesityldigermene and two mechanistic probes: trans-2-phenylcyclopropane carbaldehyde and trans,trans-2-methoxy-3-phenylcyclopropane carbaldehyde. In each reaction, two diastereomers of the formal [2+2] cycloadduct between the aldehyde and the digermene were obtained. These findings, together with the results of a recent theoretical study, indicate that the addition of carbonyl compounds to digermenes proceeds via a mechanism involving a zwitterionic intermediate. 相似文献
3.
A 2D model for the potential distribution in silicon film is derived for a symmetrical double gate MOSFET in weak inversion. This 2D potential distribution model is used to analytically derive an expression for the subthreshold slope and threshold voltage. A drain current model for lightly doped symmetrical DG MOSFETs is then presented by considering weak and strong inversion regions including short channel effects, series source to drain resistance and channel length modulation parameters. These derived models are compared with the simulation results of the SILVACO (Atlas) tool for different channel lengths and silicon film thicknesses. Lastly, the effect of the fixed oxide charge on the drain current model has been studied through simulation. It is observed that the obtained analytical models of symmetrical double gate MOSFETs are in good agreement with the simulated results for a channel length to silicon film thickness ratio greater than or equal to 2. 相似文献
4.
Virginie Blot Jean-François Brièr Marion Davoust Stéphanie Minière Vincent Reboul Patrick Metzner 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1171-1182
Abstract Our work on the thio-Claisen rearrangement mediated by an adjacent sulfinyl group is reviewed. The substrates could easily be prepared on a large scale from diacetone-D-glucose. The rearrangement was effected with a diastereoselectivity of 95:5, in favor of the (S,S) or the (R,R) isomer. An approach to natural bis(lactones) was investigated, using a halolactonization reaction and a second [3,3] sigmatropic shift, again mediated by the sulfinyl group. The second part deals with the catalytic enantioselective benzylidenation of aldehydes, mediated by chiral sulfur ylides. We have introduced simple C 2 symmetric thiolanes for that purpose. The procedure is very practical and enantiomeric excesses up to 96% have been reported for the model of stilbene oxide. A series of ferrocenyl sulfides with planar chirality has also been investigated, leading to unexpected diastereoselectivities and enantiomeric excesses up to 94%. 相似文献
5.
Ljubiša Balanović Dragana Živković Dragan Manasijević Duško Minić Bata Marjanović 《Journal of Thermal Analysis and Calorimetry》2013,111(2):1431-1435
The results of calorimetric study and thermal analysis of binary Al–Sn system are presented in this paper. The Oelsen calorimetry was used in thermodynamic analysis. Following thermodynamic properties were determined at 727 °C: activities, activity coefficients, partial/integral molar Gibbs excess, and mixing energies. The energetics of mixing in liquid Al–Sn alloys has been analyzed through the study of concentration fluctuation in the long-wavelength limit. Thermal analysis of selected alloys in Al–Sn system was done using differential thermal analysis. Defined characteristic phase transition temperatures were used for comparison with calculated phase diagram of investigated system. Good agreement with available literature data was obtained. Structural analysis of selected alloys was done using optic microscopy. 相似文献
6.
A new phenanthroindolizidine alkaloid, 3-O-demethyl tylophorinidine (VI), was isolated from the aerial (leaves and stem) parts of Tylophora indica and characterized using different spectral techniques. Gel chromatography and reverse phase preparative HPLC were used for sample purification. The new alkaloid, VI, was screened for anticancer activity against a panel of different cancer cell lines and it showed significant anticancer activity with IC50 value in the range of 0.89?C1.40 ??M. 相似文献
7.
8.
D. M. Minić M. Djordjević Z. Džambaski M. Šumar-Ristović R. Marković 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(13):2288-2294
The kinetics and mechanism of the structural transformation of 2-(5-ethoxycarbonylmethyl-4-oxothiazolidin-2-ylidene)-N-(2-phenylethyl)-ethanamide
in non-isothermal conditions were studied by using isoconversion as well as non-isoconversion techniques. It was shown that
the crystal, Z-form of compound, was stable in the temperature range from room temperature to melting point, when E-form of compound was formed. This process involves the breaking of crystal structure and the forming of glass material as
a new phase, which by cooling forms crystal of the E-form of compound very slowly. The dependences of kinetic parameters on fractional extent conversion were determined indicating
a very complex process which involves more than one elementary step, as can be expected for most solid state reactions. The
possible mechanism of the process was discussed according to the algorithm concerning the form of these dependences. The evaluation
of kinetics parameters and isokinetic relationships were done by combination of model fitting and model-free approach. 相似文献
9.
Mügge C Rothenburger C Beyer A Görls H Gabbiani C Casini A Michelucci E Landini I Nobili S Mini E Messori L Weigand W 《Dalton transactions (Cambridge, England : 2003)》2011,40(9):2006-2016
Twelve Pt(II) complexes with cis-PtP(2)S(2) pharmacophores (where P(2) refers to two monodentate or one bidentate phosphane ligand and S(2) is a dithiolato ligand) were prepared, characterized and evaluated as potential antiproliferative agents. The various compounds were first studied from the structural point of view; afterward, their solubility properties as well as their solution behaviour were analyzed in detail. Antiproliferative properties were specifically evaluated against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin. For comparison purposes similar studies were carried out on four parent cis-dichloro bisphosphane Pt(II)complexes. On the whole, the cis-PtP(2)S(2) compounds displayed significant antiproliferative properties while the cis-PtP(2)Cl(2) (cis-dichloro bisphosphane Pt(II)) compounds revealed quite poor biological performances. To gain further insight into the molecular mechanisms of these bisphosphane Pt(II) compounds, the reactions of selected complexes against the model protein cytochrome c were investigated by ESI-MS and their adduct formation explored. A relevant reactivity with cyt c was obtained only for cis-PtP(2)Cl(2) compounds, whereas cis-PtP(2)S(2) compounds turned out to be nearly unreactive. The obtained results are interpreted and discussed in the frame of the current knowledge of anticancer platinum compounds and their structure-activity-relationships. The observation of appreciable antiproliferative effects for the relatively inert cis-PtP(2)S(2) compounds strongly suggests that these compounds will undergo specific activation within the cellular environment. 相似文献
10.
Prathapan A Lijo Cherian O Nampoothiri SV Mini S Raghu KG 《Natural product research》2011,25(3):298-309
Saraca ashoka is a widely used medicinal herb claimed to cure many diseases. This study investigated the antiperoxidative, free radical scavenging and xanthine oxidase (XO) inhibitory potential of the ethyl acetate fraction of S. ashoka flowers (SAF) and compared it with standard compounds like gallic acid, ascorbic acid, butylated hydroxyl toluene and allopurinol. The ethyl acetate fraction of SAF exhibited free radical scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical and superoxide radical, along with hydroxyl radical scavenging activity. Lipid peroxidation inhibitory potential of SAF was studied using a linoleic acid emulsion system, which shows significant antioxidant potential. SAF also demonstrated significant XO (key enzyme linked to inflammation) inhibitory activity, which revealed its therapeutic potential as an antioxidant and XO inhibitor. HPLC profiling of the ethyl acetate fraction of SAF revealed that it contains ellagic acid as a major compound and thus the beneficial effects of this fraction may be due to the presence of this compound. 相似文献