全文获取类型
收费全文 | 218篇 |
免费 | 7篇 |
专业分类
化学 | 142篇 |
晶体学 | 9篇 |
力学 | 6篇 |
数学 | 1篇 |
物理学 | 67篇 |
出版年
2022年 | 11篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 10篇 |
2009年 | 10篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 15 毫秒
41.
Hydroarylation of bicyclic alkenes has been developed using a low‐valent ReI‐catalyzed, directing group‐assisted C?H bond activation strategy. The addition of sodium acetate significantly improves the reaction efficiency; moreover, bicyclic alkenes such as 7‐oxa and aza benzonorbornadienes worked efficiently under this reaction condition. Preliminary mechanistic studies suggest that, after the alkene insertion, the rhenacycle preferentially undergoes protonolysis rather than reductive elimination. 相似文献
42.
Snehalatha M Sekar N Jayakumar VS Joe IH 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(1):82-90
Fourier transform infrared (FTIR) spectrum of a well-known food dye sunset yellow FCF (E110) has been recorded and analysed. Assignments of the vibrational spectrum has been facilitated by density functional theory (DFT) calculations. The results of the optimized molecular structure obtained on the basis of B3LYP with 6-31G(d) along with the 'LANL2DZ' basis sets give clear evidence for the intramolecular charge transfer (ICT) and strong hydrogen bonding enhancing the optical nonlinearity of the molecule. The first hyperpolarizability of the acidic monoazo dye 'E110' is computed. Azo stretching frequencies have been lowered due to conjugation and pi-electron delocalization. Hydroxyl vibrations with intramolecular H-bonding are analyzed, supported by the computed results. The natural bond orbitals (NBO) analysis confirms this strong hydrogen bond between the hydrogen of the hydroxyl group and nitrogen of the azo group of the molecule. Assignments of benzene and naphthalene ring vibrations are found to agree well with the theoretical wave numbers. 相似文献
43.
44.
45.
A. Abdul Ajees K. Sekar S. Parthasarathy K. Balakrishna 《Crystal Research and Technology》2000,35(9):1117-1123
The crystal structure of the title compound has been determined from X‐ray diffraction. The compound crystallizes from benzene in the orthorhombic system, space group P212121, with unit cell parameters: a = 8.485(2), b = 9.816(2), c = 22.597(4) Å, Z = 4, V = 1881.9(7) Å3. The structure was determined by direct methods and refined to a final R‐factor of 0.04. Six membered rings B and E are planar. Ring A and ring C are in slightly distorted sofa conformation. Ring D is in envelope conformation. The structure is stabilised by weak intermolecular C‐H...O hydrogen bonds. 相似文献
46.
R. Krishna D. Velmurugan M. Shanmugasundaram R. Raghunathan K. Sekar S. Shanmuga Sundara Raj H.‐K. Fun 《Crystal Research and Technology》2002,37(1):135-141
The crystal structure of the title compound “1′,2′,3′,4′‐tetrahydro‐1,3‐diphenyl‐4‐chlorospiro[2‐pyrazoline‐5,2‐napthalen] 1′one” has been determined. The structure consists of a pyrazoline ring, three aromatic rings and a tetralone moiety. All the aromatic rings are planar while the cyclohexonone ring of the tetralone moiety is in the distorted sofa conformation. The molecular packing is stabilized by C‐H…O and C‐H…π type inter molecular interactions. 相似文献
47.
Norman Scholz Amol Jadhav Milind Shreykar Thomas Behnke Nithiya Nirmalananthan Ute Resch-Genger Nagaiyan Sekar 《Journal of fluorescence》2017,27(6):1949-1956
A comprehensive systematic study of absorption and fluorescence properties in solvents of varying viscosity and polarity of three novel and red-emitting coumarin-rhodamine hybrid derivatives with differences in the rigidity of their substituents is presented. This includes ethanol-polyethylene glycol, toluene-polyethylene glycol, and toluene-paraffin mixtures. Moreover, protonation-induced effects on the spectroscopic properties are studied. A viscosity-induced emission enhancement was observed for all coumarin-rhodamine hybrid derivatives. MCR2 bearing a julolidine donor showed the expected low sensitivity to viscosity whereas MCR3 with its freely rotatable diphenylamino substituent revealed a particularly pronounced sensitivity to this parameter. Moreover, MCR2 shows an enhancement in emission in the open, i.e., protonated form in conjunction with a largely Stokes shift fluorescence in the deep red spectral region. This enables the application of these dyes as viscosity sensors and as far red emitting pH-sensitive probes. 相似文献
48.
Blend based polymer electrolytes composed of poly (methyl methacrylate) (PMMA), poly(vinylalcohol) (PVA) and LiClO4 are prepared using solvent casting technique. The polymer films are characterized by XRD and FTIR studies to determine the
molecular environment for the conducting ions. These polymer films have been investigated in terms of ionic conductivity using
the results of impedance studies. The influence of the blend composition on the electrochemical behaviour is also discussed.
The highest room temperature conductivity obtained for the film consisting of PMMA, PVA, LiClO4 and DMP is 0.06×10−3 S/cm at 303 K. The PMMA-PVA blend based polymer electrolytes look very desirable and promising for lithium battery applications. 相似文献
49.
Nagarajan Shobana Pandurangan Prakash Antony V. Samrot P. J. Jane Cypriyana Purohit Kajal Mahendran Sathiyasree Subramanian Saigeetha T. Stalin Dhas D. Alex Anand Gokul Shankar Sabesan Bala Sundaram Muthuvenkatachalam Basanta Kumar Mohanty Sridevi Visvanathan 《Molecules (Basel, Switzerland)》2022,27(12)
Plant gums are bio-organic substances that are derived from the barks of trees. They are biodegradable and non-adverse complex polysaccharides that have been gaining usage in recent years due to a number of advantages they contribute to various applications. In this study, gum was collected from Moringa oleifera and Azadirachta indica trees, then dried and powdered. Characterizations of gum polysaccharides were performed using TLC, GC-MS, NMR, etc., and sugar molecules such as glucose and xylose were found to be present. Effects of the gums on Abelmoschus esculentus growth were observed through root growth, shoot growth, and biomass content. The exposure of the seeds to the plant gums led to bio stimulation in the growth of the plants. Poor quality soil was exposed to the gum polysaccharide, where the polysaccharide was found to improve soil quality, which was observed through soil analysis and SEM analysis of soil porosity and structure. Furthermore, the plant gums were also found to have bio-pesticidal activity against mealybugs, which showed certain interstitial damage evident through histopathological analysis. 相似文献
50.
Ratanamala S. Darole Denzil Britto Christopher Leslee Anagh Mukherjee Rajesh G. Gonnade Sekar Karuppannan Beeran Senthilkumar 《应用有机金属化学》2020,34(10):e5867
The synthesis of a novel, and highly selective Fe3+ ion sensor based on anthrone-spirolactam and its quinoline hybrid ligand is reported. The designed ligand displayed selective detection of Fe3+ ions with enhanced fluorescence emission. The complexation of Fe3+ ion led to a red shift of 32 nm from 420 nm to 452 nm, and a several fold increase in intensity with fluorescent green emission. The complexation (detection) of Fe3+ ions with ligand resulted in chelation enhanced fluorescence and intramolecular charge transfer through the inhibition of C=N isomerization. This hybrid sensor shows high sensitivity and selectivity, spontaneous response, and works on a wide pH range a minimum detection limit of 6.83 × 10−8 M. Importantly, the sensor works through the fluorescence turn-on mechanism that overcomes the paramagnetic effect of Fe3+ ions. The binding mechanism between the ligand and the Fe3+ ions was established from the Job's plot method, optical studies, Fourier transfor infrared spectroscopy, NMR titration, fluorescence life-time studies, and density functional theory optimization. The sensor displayed excellent results in the quantification of Fe3+ ions from real water samples. Furthermore, due to its biocompatibility nature, fluorescent spotting of Fe3+ ions in live cells revealed its bioimaging applications. 相似文献