全文获取类型
收费全文 | 171篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
化学 | 128篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 16篇 |
物理学 | 31篇 |
出版年
2022年 | 2篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 10篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 17篇 |
2012年 | 16篇 |
2011年 | 16篇 |
2010年 | 8篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 9篇 |
2005年 | 6篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1984年 | 1篇 |
排序方式: 共有183条查询结果,搜索用时 281 毫秒
1.
Pd(II)-exchanged NaY zeolite showed high activity in the Suzuki cross-coupling reactions of aryl bromides and iodides without added ligands. The DMF:water ratio, and the type and amount of base were found to be critical for the efficiency of the reaction. The catalyst is reusable after regeneration. 相似文献
2.
Hwu SJ Ulutagay-Kartin M Clayhold JA Mackay R Wardojo TA O'Connor CJ Krawiec M 《Journal of the American Chemical Society》2002,124(42):12404-12405
Two novel copper(II) arsenates Na5ACu4(AsO4)4Cl2 (A = Rb, Cs) were synthesized by conventional solid-state methods using reactive molten salt media. These compounds are isostructural and crystallize in an orthorhombic lattice (Fmmm, No. 69; Z = 8). The cell constants are a = 14.632(3) A, b = 18.872(2) A, c = 14.445(3) A, V = 3989(1) A3, for A = Rb; a = 14.638(3) A, b = 18.990(4) A, c = 14.418(3) A, V = 4008(1) A3, for A = Cs. Single-crystal structure studies reveal a new composite framework consisting of alternating covalent and ionic lattices. The covalent lattice contains highly oriented oligomeric mu-oxo [Cu4O12]16- tetrameric units with a cyclo-S8-like Cu4O4 magnetic core that resembles the building block of layered cuprates. The ionic slab consists of a novel framework of mixed alkali metal chloride lattice and rarely seen Na6O8 clusters. Similar to organic-inorganic hybrid materials, the title compounds present a new class of host-guest chemistry via salt inclusion reactions. 相似文献
3.
The effect of 60Co γ-irradiation on aqueous solutions of poly(N-vinyl-2-pyrrolidone) (PVP) in the presence of persulfate anion has been investigated. The gelation dose of PVP and persulfate containing PVP aqueous solutions has been determined. At low concentrations of persulfate (1.00–3.50%), gelation percentages exhibited a decreasing trend by increasing persulfate content in aqueous solutions of the polymer. The gelation doses of persulfate containing polymer solutions were calculated by the Charlesby–Pinner equation. It was observed that the gelation dose values were shifted to higher values by increasing persulfate concentration in solution. The ratio of the chain scission and crosslinking yields (G(s)/G(x)) was also determined. The results showed that the G(s)/G(x) ratios were smaller than one for PVP aqueous solution system, whereas those obtained for persulfate containing PVP aqueous solutions were higher than unity. The results implied that the chain scission of polymer is more effective than crosslinking in the presence of persulfate. Mechanism of the crosslinking and/or degradation and structure–property relationship of PVP and PVP/persulfate hydrogel systems were investigated by Fourier transformation infeared and thermal analysis (differential scanning calorimetry, thermal gravimetric analysis and differential thermai analysis) methods. 相似文献
4.
H. DagistanliR.H. Mutlu 《Radiation Physics and Chemistry》2012,81(3):240-241
The occupation numbers of the 3d transition metals are calculated as a function of pressure by means of the linear muffin-tin-orbital method. This data is used with the multiconfiguration Dirac-Fock (MCDF) X-ray intensity ratios (R) to estimate the variation of the intensity ratios of 3d metals with pressure. It is found that R decreases with pressure for the early 3d metals whereas it increases for the heavier 3d transition metals. 相似文献
5.
Yener Suayb Cagri Yener Tuba Mutlu Resat 《Journal of Thermal Analysis and Calorimetry》2018,134(2):1243-1252
Journal of Thermal Analysis and Calorimetry - In this paper, the current, voltage and temperature of the container of an electric current-activated/assisted sintering (ECAS) system are measured and... 相似文献
6.
Mert Mehmet Selçuk Mert Hatice Hande Sert Merve 《Journal of Thermal Analysis and Calorimetry》2019,136(4):1551-1561
Journal of Thermal Analysis and Calorimetry - Thermal energy storage systems provide efficiency in order to have better utilization of energy sources while protecting the environment. Thermal... 相似文献
7.
Selma Bal Sedat Salih Bal Abdullah Erener Hatice Nur Halipci Seyhan Akar 《Chemical Papers》2014,68(3):352-361
Four water soluble azo dyes, 4-(isopropyl)-2-[(E)-(4-chlorophenyl)diazenyl]phenol (L 1), 4-(isopropyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L2), 4-(sec-butyl)-2-[(E)-(4-chlorophenyl) diazenyl]phenol (L 3), 4-(sec-butyl)-2-[(E)-(2,4-dichlorophenyl)diazenyl]phenol (L 4), and their Cu(II) and Ni(II) complexes were synthesized and characterized using spectroscopic methods. Examination of their thermal stability revealed similar decomposition temperature of approximately 260–300°C and that they were more thermally stable than their metal complexes. Ni(II) complexes of ligands L2 and L4 were more stable than the other coordination compounds. Among the synthesized ligands, L2 and the complexes Cu(L3)2 and Ni(L4)2 showed both antimicrobial and antifungal activity. However, the other ligands and the complexes were poorly active against selected microorganisms. 相似文献
8.
9.
Mehmet Burçin Pişkin Aysel Kantürk Figen Hatice Ergüven 《Research on Chemical Intermediates》2013,39(2):569-583
In this study, the solid-state reaction mechanism and kinetics were investigated for production of anhydrous sodium metaborate (NaBO2), an industrially and technologically important boron compound. To assess the kinetics of solid-state production of NaBO2, the chemical reaction between borax (Na2B4O7) and sodium hydroxide (NaOH) was investigated by use of the thermal analysis techniques thermogravimetry (TG) and differential thermal analysis (DTA). DTA curves obtained under non-isothermal conditions at different heating rates (5, 10 and 20 °C/min), revealed five endothermic peaks corresponding to five solid-state reactions occurring at 70, 130, 295, 463, and 595 °C. The stages of the solid-state reaction used for production NaBO2 were also analyzed by XRD, which showed that at 70 and 130 °C, Na2B4O7 and NaOH particles contacted between the grains, and diffusion was initiated at the interface. However, there was not yet any observable formation of NaBO2. Formation of NaBO2 was initiated and sustained from 295 to 463 °C, and then completed at 595 °C; the product was anhydrous NaBO2. Activation energies (E a) of the solid-state reactions were calculated from the weight loss based on the Arrhenius model; it was found that in the initial stages of the solid-state reaction E a values were lower than in the last three steps. 相似文献
10.
Akgul Dogan Mercan Hatice Dalkilic Ahmet Selim 《Journal of Thermal Analysis and Calorimetry》2022,147(22):12577-12594
Journal of Thermal Analysis and Calorimetry - In this study, helically coiled tubes are used in a shell, and the effects of tube diameter, coil diameter, Reynolds number, Dean number and flow rate... 相似文献