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排序方式: 共有167条查询结果,搜索用时 15 毫秒
71.
S. Parthiban H. Anandalakshmi S. Senthilkumar V. Karthikeyan S. C. Mojumdar 《Journal of Thermal Analysis and Calorimetry》2012,108(3):881-885
We have prepared pure and divalent vanadyl ion-doped magnesium rubidium sulfate hexahydrate crystals by using slow evaporation solution growth technique. It is interesting to observe that Vo(II) doping influences the physical properties of MRSH. Presence of Vo(II) ions in the doped specimen was confirmed by energy dispersive spectroscopy and electron paramagnetic resonance spectroscopy. FTIR studies reveal that the doping of vanadium ion has not altered the basic structure of MRSH. Scanning electron microscope studies of doped sample reveals that structure defect centers are formed in the crystals. Gradual decomposition patterns were observed for pure and doped specimens in thermogravimetry and differential thermogravimetry. The grown crystals were also characterized by powder X-ray diffraction. The second harmonic generation efficiency tested using Kurtz powder technique is not influenced by the added dopant. 相似文献
72.
The efect of Dzyaloshinskii–Moriya(D-M) interaction on the bistable nano-scale soliton switching ofers the possiblity of developing a new innovative approach for data storage technology. The dynamics of Heisenberg ferromagnetic spin system is expressed in terms of generalized inhomogeneous higher order nonlinear Schro¨dinger(NLS) equation. The bistable soliton switching in the ferromagnetic medium is established by solving the associated coupled evolution equations for amplitude and velocity of the soliton using the fourth order Runge–Kutta method numerically. 相似文献
73.
E.J. Ngamga D.V. Senthilkumar J. Kurths 《The European physical journal. Special topics》2010,191(1):15-27
We show that dynamics between order and chaos, namely strange nonchaotic dynamics can be efficiently studied by means of recurrence
properties. Different transitions to this dynamics in coupled R?ssler oscillators are revealed by some measures of complexity
based on the recurrence time, which is the time needed for a system to recur to a former visited neighborhood. Furthermore,
regions of the parameter space where the system is in non-phase, imperfect-phase or phase synchronization are depicted by
means of recurrence based indices such as the generalized autocorrelation function and the correlation of probability of recurrence. 相似文献
74.
Ashokkumar B Senthilkumar SR Gunasekaran P 《Applied biochemistry and biotechnology》2004,118(1-3):89-96
Aspergillus niger NRRL330 produces extracellular β-fructofuranosidase (Ffase), and its production is subject to repression by hexoses in the
medium. After ultraviolet mutagenization and selection, seven derepressed mutants resistant to 2-deoxyglucose (2-DG) were
isolated on Czapek’s minimal medium containing glycerol. One of the mutants, designated DGRA-1, produced higher levels of
Ffase. A considerable difference occurred in the mutants with reference to hexokinase and intracellular acid phosphatase activities.
The hexokinase activity of the mutant DGRA-1 (0.69 U/mg) was 1.8-fold higher than the wild type (0.38U/mg). Intracellular
acid phosphatase activity of the mutant DGRA-1 (0.83 U/g of mycelia) was twofold higher than that of the wild type (0.42U/g
of mycelia), suggesting that phosphorylation and dephosphorylation steps could attribute to the 2-DG resistance of A. niger. However, additional mutations could account for the increased production of Ffase in the mutant DGRA-1. 相似文献
75.
Dr. Guillermo Valdomir Dr. Soundararasu Senthilkumar Dr. Dhandapany Ganapathy Dr. Yun Zhang Prof. Dr. Lutz F. Tietze 《化学:亚洲杂志》2018,13(15):1888-1891
A one pot borylation/Suzuki–Miyaura reaction of the 4‐bromochromanone lactones 21 and 23 , respectively, followed by cleavage of the methyl ether moieties gave the homodimeric chromanone lactones 10 and 11 . Reaction of a 1:1 mixture of 21 and 23 under otherwise identical conditions gave a 1:1:2‐mixture of the two homodimers 10 and 11 and the heterodimer 12 . This is the first example of the preparation of a heterodimeric chromanone lactone. For the enantioselective synthesis of the starting material, phenol 17 was transformed into the chromane 18 using a Wacker‐type cyclisation with 99 % ee and 80 % yield. 相似文献
76.
Aldosterone Glucuronide,an Important Biomarker: Synthesis and Structure Elucidation of Novel Isomers
Dr. Somraj Guha Dr. Soundararasu Senthilkumar Dr. Edgar Voß Prof. Dr. Lutz F. Tietze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15733-15737
Aldosterone 1 is a mineralocorticoid, it has great influence on the blood pressure and its glucuronide is an important marker for the detection of several diseases. Here, we describe the chemical synthesis of different aldosterone-18- and 20-glucuronides. Reaction of trimethylsilyl 2,3,4-tri- acetyl-1-β-glucuronic acid methyl ester 5 b and aldosterone diacetate 11 in the presence of TMSOTf gave the 18-α-glucuronide 9 a . The 18-β-glucuronide 15 b and the 20-β-glucuronide 16 b could be obtained by reaction of methyl 2,3,4-tri-O-isobutyryl-1α-glucuronate trichloroacetimidate 14 and aldosterone 21-acetate 8 in the presence of TMSOTf or BF3⋅OEt2. Finally, reaction of aldosterone 21-acetate 8 and methyl 2,3,4-triacetyl-1α-glucuronate trichloroacetimidate 19 in the presence of TMSOTf gave the corresponding methyl 18-β-triacetylglucuronate 9 b , which was transformed into the desired aldosterone-18-β-glucuronide 3 by two enzyma- tic transformations. 相似文献
77.
Prins P Senthilkumar K Grozema FC Jonkheijm P Schenning AP Meijer EW Siebbeles LD 《The journal of physical chemistry. B》2005,109(39):18267-18274
We have studied the mobility of charge carriers along self-organizing pi-stacks of hydrogen-bonded phenylene vinylene oligomers in solution, by time-resolved microwave conductivity measurements. The value deduced for the mobility along the stacks is 3 x 10(-3) and 9 x 10(-3) cm2/(V s) for holes and electrons, respectively. Additionally, we have calculated the mobility along the pi-stacks using a hopping model based on parameters from density functional theory. The mobility values obtained from these calculations are in good agreement with the experimental values if it is assumed that there are relatively large twist angles between neighboring molecules in the stack. It is shown that a significantly higher mobility can be attained if the twist angle between neighboring oligomers is reduced. 相似文献
78.
Single crystals of novel semiorganic material, potassium diboro-oxalate (PDO) have been grown from aqueous solution by slow evaporation technique. The lattice parameters for the grown crystals were determined by the single crystal X-ray diffraction analysis and the crystallinity of the grown crystal was confirmed by powder X-ray diffraction analysis. The presence of functional groups was estimated qualitatively by using Fourier transform infrared (FTIR) analysis. The optical absorption spectrum shows that the UV cut-off wavelength for the grown crystal is at 240 nm and the band gap was calculated. The thermal stability of the grown crystal was studied by using TG/DTA analysis. The second harmonic generation and the phase-matchable tests were performed by Kurtz powder technique. The crystal perfection was analyzed by SEM photographs. 相似文献
79.
Enhancing Capacity Performance by Utilizing the Redox Chemistry of the Electrolyte in a Dual‐Electrolyte Sodium‐Ion Battery 下载免费PDF全文
Dr. Sirugaloor Thangavel Senthilkumar Hyuntae Bae Jinhyup Han Prof. Youngsik Kim 《Angewandte Chemie (International ed. in English)》2018,57(19):5335-5339
A strategy is described to increase charge storage in a dual electrolyte Na‐ion battery (DESIB) by combining the redox chemistry of the electrolyte with a Na+ ion de‐insertion/insertion cathode. Conventional electrolytes do not contribute to charge storage in battery systems, but redox‐active electrolytes augment this property via charge transfer reactions at the electrode–electrolyte interface. The capacity of the cathode combined with that provided by the electrolyte redox reaction thus increases overall charge storage. An aqueous sodium hexacyanoferrate (Na4Fe(CN)6) solution is employed as the redox‐active electrolyte (Na‐FC) and sodium nickel Prussian blue (Nax‐NiBP) as the Na+ ion insertion/de‐insertion cathode. The capacity of DESIB with Na‐FC electrolyte is twice that of a battery using a conventional (Na2SO4) electrolyte. The use of redox‐active electrolytes in batteries of any kind is an efficient and scalable approach to develop advanced high‐energy‐density storage systems. 相似文献
80.
Champaka Gurudevaru Mohan Gopalakrishnan Kabali Senthilkumar Hridya Hemachandran Ramamoorthy Siva Thothadri Srinivasan Devadasan Velmurugan Swaminathan Shanmugan Nallasamy Palanisami 《应用有机金属化学》2018,32(2)
Mononuclear and dinuclear copper(II) complexes with thiophenecarboxylic acid, [Cu(3‐TCA)2(2,2′‐bpy)] ( 1 ), [Cu(3‐Me‐2‐TCA)2(H2O)(2,2′‐bpy)] ( 2 ), [Cu(5‐Me‐2‐TCA)2(H2O)(2,2′‐bpy)] ( 3 ) and [Cu2(2,5‐TDCA)(DMF)2(H2O)2(2,2′‐bpy)2](ClO4)2 ( 4 ) (where 3‐TCA = 3‐thiophenecarboxylic acid; 3‐Me‐2‐TCA = 3‐methyl‐2‐thiophenecarboxylic acid; 5‐Me‐2‐TCA = 5‐methyl‐2‐thiophenecarboxylic acid; 2,5‐TDCA = thiophene‐2,5‐dicarboxylic acid; 2,2′‐bpy = 2,2′‐bipyridyl; DMF = N,N‐dimethylformamide), were synthesized. Compounds 1 – 4 were extensively characterized using both analytical and spectroscopic methods. Additionally, the solid‐state structures of 1 and 4 were unambiguously established from single‐crystal X‐ray diffraction studies. The hexacoordinated Cu(II) centre in 1 (CuO4N2) is a distorted octahedral geometry whereas the pentacoodinated 4 (CuO3N2) has distorted square pyramidal geometry. Compounds 1 and 4 exhibit intermolecular hydrogen bonding which leads to the formation of two‐ and three‐dimensional supramolecular architectures, respectively. Spectrophotometric and computational investigations suggest that these compounds bind with DNA in minor groove binding such that Kb = 4.9 × 105 M?1 and Ksv = 3.4 × 105 M?1, and binding score of ?5.26 kcal mol?1. The binding affinity of these complexes to calf thymus DNA is in the order 2 > 3 > 4 > 1 . Methyl‐substituted thiophene ring increases the DNA binding affinity whereas unsubstituted thiophene ring DNA binding rate is reduced. The methyl group on the thiophene ring would sterically hinder π–π stacking of the ring with DNA base pairs, and subsequently they are involved in hydrophobic interaction with the DNA surface rather than partial intercalative interaction. Compounds 1 – 4 show pronounced activity against B16 mouse melanoma skin cancer cell lines as measured by MTT assay yielding IC50 values in the micromolar concentration range. The compounds could prove to be efficient anti‐cancer agents, since at a concentration as low as 2.1 μg ml?1 they exerted a significant cytotoxic effect in cancer cells whereas cell viability was not affected in normal cells. 相似文献