全文获取类型
收费全文 | 108篇 |
免费 | 5篇 |
专业分类
化学 | 72篇 |
力学 | 5篇 |
数学 | 7篇 |
物理学 | 29篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2020年 | 2篇 |
2019年 | 6篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 11篇 |
2011年 | 7篇 |
2010年 | 6篇 |
2009年 | 1篇 |
2008年 | 7篇 |
2007年 | 5篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1995年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有113条查询结果,搜索用时 31 毫秒
81.
Polymer‐Induced Surface Modifications of Pd‐based Thin Films Leading to Improved Kinetics in Hydrogen Sensing and Energy Storage Applications
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Peter Ngene Dr. Ruud J. Westerwaal Sumit Sachdeva Dr. Wim Haije Dr. Louis C. P. M. de Smet Prof. Dr. Bernard Dam 《Angewandte Chemie (International ed. in English)》2014,53(45):12081-12085
The catalytic properties of Pd alloy thin films are enhanced by a thin sputtered PTFE coating, resulting in profound improvements in hydrogen adsorption and desorption in Pd‐based and Pd‐catalyzed hydrogen sensors and hydrogen storage materials. The remarkably enhanced catalytic performance is attributed to chemical modifications of the catalyst surface by the sputtered PTFE leading to a possible change in the binding strength of the intermediate species involved in the hydrogen sorption process. 相似文献
82.
83.
A new C-linked carbo-β-amino acid, (R)-β-Caa((r)), having a carbohydrate side chain with d-ribo configuration, was prepared from d-glucose by inverting the C-3 stereocenter to introduce constraints/interactions. From the NMR studies it was inferred that the new monomer may participate in additional electrostatic interactions, facilitating and enhancing novel folds in oligomeric peptides derived from it. The α/β-peptides, synthesized from alternating l-Ala and (R)-β-Caa((r)), have shown the presence of 14/15-helix by NMR (in CDCl(3), methanol-d(3) and CD(3)CN), CD and MD calculations. The hybrid peptides showed the presence of electrostatic interactions involving the intraresidue amide proton and the C3-OMe, which helped in the stabilization of the NH(i)···CO(i-4) H-bonds and adoption of 14/15-helix. The importance of such additional interactions has been well defined in recent times to stabilize the folding in a variety of peptidic foldamers. These observations suggest and emphasize that the side chain-backbone interactions are crucial in the stabilization of the desired folding propensity. The designed monomer thus enlarges the opportunities for the synthesis of peptides with novel conformations and expands the repertoire of the foldamers. 相似文献
84.
During in vitro selection for DNA-catalyzed lysine reactivity, we identified a deoxyribozyme that instead catalyzes nucleophilic attack of a phosphoramidate functional group at a 5'-triphosphate-RNA, forming an unusual pyrophosphoramidate (N-P(V)-O-P(V)) linkage. This finding highlights the relatively poor nucleophilicity of nitrogen using nucleic acid catalysts, indicating a major challenge for future experimental investigation. 相似文献
85.
B. Anupama M. Sunita D. Shiva Leela B. Ushaiah C. Gyana Kumari 《Journal of fluorescence》2014,24(4):1067-1076
A series of transition metal complexes of Co(II), Ni(II), Zn(II), Fe(III) and VO(IV) have been synthesized involving the Schiff base, 2,3-dimethyl-1-phenyl-4-(2-hydroxy-3-methoxy benzylideneamino)-pyrazol-5-one(L), obtained by condensation of 4-aminoantipyrine with 3-methoxy salicylaldehyde. Structural features were obtained from their FT-IR, UV–vis, NMR, ESI Mass, elemental analysis, magnetic moments, molar conductivity and thermal analysis studies. The Schiff base acts as a monovalent bidentate ligand, coordinating through the azomethine nitrogen and phenolic oxygen atom. Based on elemental and spectral studies six coordinated geometry is assigned to Co(II), Ni(II), Fe(III) and VO(IV) complexes and four coordinated geometry is assigned to Zn(II) complex. The interaction of metal complexes with Calf thymus DNA were carried out by UV–VIS titrations, fluorescence spectroscopy and viscosity measurements. The binding constants (Kb) of the complexes were determined as 5?×?105 M?1 for Co(II) complex, 1.33?×?104 M?1 for Ni(II) complex, 3.33?×?105 M?1 for Zn(II) complex, 1.25?×?105 M?1 for Fe(III) complex and 8?×?105 M?1 for VO(IV) complex. Quenching studies of the complexes indicate that these complexes strongly bind to DNA. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. The ligand and it’s metal complexes were screened for their antimicrobial activity against bacteria. The results showed the metal complexes to be biologically active, while the ligand to be inactive. 相似文献
86.
87.
The silica gel modified with (3-aminopropyl-triethoxysilane) was reacted with 5-formyl-8-hydroxyquinoline (FHOQx) to anchor 8-quinolinol ligand on the silica gel. It was characterised with cross polarisation magic angle spinning (CPMAS) NMR and diffuse reflectance infrared Fourier transformation (DRIFT) spectroscopy and used for the preconcentration of Cu(II), Pb(II), Ni(II), Fe(III), Cd(II), Zn(II) and Co(II) prior to their determination by flame atomic absorption spectrometry. The surface area of the modified silica gel has been found to be 227 m2 g−1 and the two pKa values as 3.8 and 8.0. The optimum pH ranges for quantitative sorption are 4.0–7.0, 4.5–7.0, 3.0–6.0, 5.0–8.0, 5.0–8.0, 5.0–8.0 and 4.0–7.0 for Cu, Pb, Fe, Zn, Co, Ni and Cd, respectively. All the metals can be desorbed with 2.5 mol l−1 HCl or HNO3. The sorption capacity for these metal ions is in range of 92–448.0 μmol g−1 and follows the order Cd3, NaCl, NaBr, Na2SO4 and Na3PO4, glycine, sodium citrate, EDTA, humic acid and cations Ca(II), Mg(II), Mn(II) and Cr(III) in the sorption of all the seven metal ions are reported. The preconcentration factors are 150, 250, 200, 300, 250, 300 and 200 for Cd, Co, Zn, Cu, Pb, Fe and Ni, respectively and t1/2 values <1 min except for Ni. The 95% extraction by batch method takes ≤25 min. The simultaneous enrichment and determination of all the metals are possible if the total load of the metal ions is less than sorption capacity. In river water samples all these metal ions were enriched with the present ligand anchored silica gel and determined with flame atomic absorption spectrometer (R.S.D.≤6.4%). Cobalt contents of pharmaceutical samples (vitamin tablet) were preconcentrated with the present chelating silica gel and estimated by flame AAS, with R.S.D.1.4%. The results are in the good agreement with the certified value, 1.99 μg g−1 of the tablets. Iron and copper in certified reference materials (synthetic) SLRS-4 and SLEW-3 have been enriched with the modified silica gel and estimated with R.S.D.<5%. 相似文献
88.
Mallinath B. Hadimani Raymond J. Kessler Jason A. Kautz Anjan Ghatak Anupama R. Shirali Heather O'Dell Charles M. Garner Kevin G. Pinney 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(6):o330-o332
In the crystal structure of the title compound, C32H39NO7Si, all geometric parameters fall within experimental error of expected values. The analysis of molecular‐packing plots reveals an infinite two‐dimensional linear array running parallel to the b axis, formed by one N—H?O intermolecular hydrogen‐bonding interaction. Several potential C—H?O interactions are also present. 相似文献
89.
The objective of this study was to characterize cellulose nanocrystals /TPS-based nanocomposites. Nanocrystalline cellulose was isolated from cotton linters using sonochemical method and characterized through WXRD, TEM, and FTIR. These nanocrystals were then dispersed in glycerol and sorbitol plasticized starch using a Fluko high shear homogenizer in varying proportions and films were cast. The films were characterized using WXRD, SEM, and mechanical properties. TEM images of nanocrystals revealed a diameter of 20–30 nm and length 200–300 nm. XRD results for nanocomposite films for both the plasticizers showed 2θ peaks at 14.8°, 16.7,° and 22.5°. Elastic modulus increased with addition of cellulose nanocrystals and tan δ shifted toward higher temperature for both the plasticizers. Mechanical properties improved more than 200% for both glycerol and sorbitol plasticized nanocomposites. 相似文献
90.
Lanthanides Mediated Oxidative Cross Coupling of Benzylalcohol and Various Amines to Form Corresponding Imines
下载免费PDF全文
![点击此处可从《无机化学与普通化学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Herein, a new and efficient approach towards the oxidative cross‐coupling of benzylalcohol and various aromatic amines to form corresponding imines with high degree conversion (>80 %) and chemo‐selectivity using lanthanide salts as pre‐catalysts is presented. The catalyzed oxidative cross‐coupling reaction using La(NO3)3 · 6H2O as pre‐catalyst displayed a broad substrate scope. The reaction afforded various substituted imines from the reaction of benzylalcohol with ample variety of amines in good yields. 相似文献