全文获取类型
收费全文 | 258篇 |
免费 | 4篇 |
专业分类
化学 | 166篇 |
晶体学 | 2篇 |
力学 | 5篇 |
数学 | 63篇 |
物理学 | 26篇 |
出版年
2023年 | 2篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 6篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 7篇 |
2014年 | 18篇 |
2013年 | 35篇 |
2012年 | 15篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 20篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 6篇 |
2005年 | 9篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1941年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1901年 | 1篇 |
排序方式: 共有262条查询结果,搜索用时 15 毫秒
11.
Cristina Bucur Romana Cerc Korošec Mihaela Badea Larisa Calu Mariana Carmen Chifiriuc Nicoleta Grecu Nicolae Stanică Dana Marinescu Rodica Olar 《Journal of Thermal Analysis and Calorimetry》2013,113(3):1287-1295
Novel complexes of type M2LCl4·nH2O (M: Ni, n = 4; M: Cu, n = 2.5 and M: Zn, n = 1.5; L: ligand resulted from 1,3-phenylenediamine, 3,6-diazaoctane-1,8-diamine, and formaldehyde one-pot condensation) were synthesized and characterized. The ligand was also isolated and characterized. The complexes features have been assigned from microanalytical, electrospray ionization tandem mass spectrometry, IR, UV–vis, 1H NMR, and EPR spectra as well as magnetic data at room temperature. Simultaneous thermogravimetric/dynamic scanning calorimetry/evolved gas analysis measurements were performed to evidence the nature of the gaseous products formed in each step. Processes as water elimination, fragmentation, and oxidative degradation of the organic ligand as well as chloride elimination were observed during the thermal decomposition. The final product of decomposition was metal(II) oxide except for copper complex where CuCl remained also in the oxide network. The complexes exhibited an improved antibacterial activity in comparison with the ligand concerning both planktonic as well as biofilm-embedded cells. 相似文献
12.
Adrian Cǎpritǎ Gheorghe Ilia Rodica Cǎpritǎ 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1)
Abstract A method for the synthesis of esters of 2-(dimethylsulfonium)ethylphos-phonic acid and the results of some trials showing the plant growth regulating activity of these compounds are presented. For the synthesis of the mentioned compounds, dimethyl sulphide is reacted with 2-chloroethylphosphonic acid esters; these esters are obtained through the complex[1] of AlCl3, PCl3 and 1,2-dichloroethan (1). Using the optimum reaction conditions, very good yields were obtained (96–99%). This complex is reacted with different alcohols to give 2-chloroethylphosphonic acid esters (2) (R?Me, Et, Pr, i-Pr, Bu, i-Bu, Pe). Using the optimum reaction conditions, in the case of methanol the maximum obtained yield was 50%. In the case of the other alcohols, the obtained yields were between 76 and 83%. An exception is i-propanol. whose ester was obtained with low yields and the reaction parameters modification have little influence on the yield. The reaction of the esters with dimethyl sulphide gives, in good yields (between 69 and 79%). esters of 2-(dimethylsulfonium)ethylphosphonic acid (3). substances with plant growth regulating activity. 相似文献
13.
Conformational transformations of the tetraenic nystatin chromophore under the influence of solvents and UV irradiation have been studied by absorption, fluorescence and wide-line NMR spectroscopy. 相似文献
14.
Calu Larisa Badea Mihaela Čelan Korošin Nataša Chifiriuc Mariana Carmen Bleotu Coralia Stanică Nicolae Silvestro Luigi Maurer Martin Olar Rodica 《Journal of Thermal Analysis and Calorimetry》2018,134(3):1839-1850
Journal of Thermal Analysis and Calorimetry - A novel series of complexes ML(ClO4)·nH2O (M: Co, Ni, Cu, Zn; HL: 2-[(E)-(1H-1,2,4-triazol-3-ylimino)methyl]phenol) have been synthesized and... 相似文献
15.
Rodica Zvoianu Cristina R. Dias M. Farinha Portela 《Reaction Kinetics and Catalysis Letters》2001,72(2):201-208
The acid-base properties of a series of SiO2-supported NiMoO4 catalysts were investigated by temperature-programmed desorption of NH3 and CO2. Results show that supported catalysts with ca. one monolayer of the active phase are less acidic than the unsupported stoichiometric NiMoO4. 相似文献
16.
Two proofs are given, one combinatorial, the other by character theory, for the identity, ∏λa1! a2! … an! = ∏λ1a12a2 … nan, where λ ranges over all partitions λ = (1a12a2 … nan) of n. The two demonstrations yield a simple proof of the known formula, det2T(n) = [∏λ1a12a2 … nan]2, where T(n) is the matrix formed by the character table of Sn. Finally a sufficient condition is given so that the permanent of T(n) is zero. 相似文献
17.
Closed kernel systems of the coalition matrix turn out to correspond to cones of games on which the core correspondence is
additive and on which the related barycentric solution is additive, stable and continuous. Different perfect cones corresponding
to closed kernel systems are described.
Received: December 2001/Revised: July 2002
RID="*"
ID="*" This note contains the new results, which were presented by the first author in an invited lecture at the XIV Italian
Meeting on Game Theory and Applications in Ischia, July 2001. The lecture was dedicated to Irinel Dragan on the occasion of
his seventieth birthday. 相似文献
18.
Mihaela?BadeaEmail author Rodica?Olar Valentina?Uivarosi Dana?Marinescu Victoria?Aldea 《Journal of Thermal Analysis and Calorimetry》2012,107(1):279-285
Two new complexes with formula VOL2·nH2O ((1) L: 4′,5,7-trihydroxyflavone-7-rhamnoglucoside (naringin), n = 8; (2) L: 3′,4′,7-tris[O-(2-hydroxyethyl)]rutin (troxerutin), n = 0) were synthesised and characterised. The IR and UV–Vis spectral data indicate that these flavones act as bidentate chelating
ligands and generate VO(II) complexes with a square-pyramidal stereochemistry. The thermal analysis (TG, DTA) elucidated the
composition and also the number and nature of the water molecules. The thermal behavior indicates also a strong interaction
between oxovanadium (IV) and these oxygen donor ligands. 相似文献
19.
Bros Ildiko Soran Maria-Loredana Briciu Rodica Domnica Cobzac Simona Codruta 《平面色谱法杂志一现代薄层色谱法》2009,22(1):25-28
JPC – Journal of Planar Chromatography – Modern TLC - A study of quantitative analysis of some flavonoids in Satureja hortensis L. extracts is presented. The HPTLC analyses were... 相似文献
20.
Cristina R. Dias Rodica Zãvoianu M. Farinha Portela 《Reaction Kinetics and Catalysis Letters》2002,77(2):317-324
The acid-base properties of several NiMoO4 catalysts supported on two silicas and prepared by different methods have been studied by temperature-programmed desorption of NH3. The catalytic behavior in the oxidative dehydrogenation of isobutane for two NiMoO4 catalysts with different acid-base properties are compared. 相似文献