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排序方式: 共有121条查询结果,搜索用时 687 毫秒
61.
Aakash D. Nidhankar Goudappagouda Divya S. Mohana Kumari Shailendra Kumar Chaubey Rashmi Nayak Rajesh G. Gonnade G. V. Pavan Kumar Retheesh Krishnan Sukumaran Santhosh Babu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):13179-13185
Room-temperature phosphorescence of metal and heavy atom-free organic molecules has emerged as an area of great potential in recent years. A rational design played a critical role in controlling the molecular ordering to impart efficient intersystem crossing and stabilize the triplet state to achieve room-temperature ultralong phosphorescence. However, in most cases, the strategies to strengthen phosphorescence efficiency have resulted in a reduced lifetime, and the available nearly degenerate singlet-triplet energy levels impart a natural competition between delayed fluorescence and phosphorescence, with the former one having the advantage. Herein, an organic helical assembly supports the exhibition of an ultralong phosphorescence lifetime. In contrary to other molecules, 3,6-phenylmethanone functionalized 9-hexylcarbazole exhibits a remarkable improvement in phosphorescence lifetime (>4.1 s) and quantum yield (11 %) owing to an efficient molecular packing in the crystal state. A right-handed helical molecular array act as a trap and exhibits triplet exciton migration to support the exceptionally longer phosphorescence lifetime. 相似文献
62.
Abstract The effect of sodium benzoate (SB) and sodium 4-(phenylamino)benzenesulfonate (SPABS) on the corrosion behavior of low carbon
steel has been investigated using gravimetric method in the temperature range of 30–80 °C, velocity range of 1.44–2.02 m s−1 and concentration range of 6.94 × 10−4 to 4.16 × 10−3 mol dm−3 SB and 3.69 × 10−4 to 2.06 × 10−3 mol dm−3 SPABS. Optimization of temperature, fluid velocity, and inhibitors concentration has been made. The obtained results indicate
that the inhibition efficiency (w
IE %) at 1.56 m s−1 is not in excess of 81.5% at 4.16 × 10−3 mol dm−3 SB and 84.4% at 2.06 × 10−3 mol dm−3 SPABS. The inhibitive performance of these compounds showed an improvement with increasing concentration up to critical values
of SB and SPABS; beyond these concentrations no further effectiveness is observed. These inhibitors retard the anodic dissolution
of low carbon steel by protective layer bonding on the metal surface. The adsorption of SB and SPABS on the low carbon steel
surface was found to obey the Freundlich isotherm model. The FT-IR spectroscopy was used to analyze the surface adsorbed film.
Graphical abstract Low carbon steel corrosion in presence of sodium benzoate and sodium 4-(phenylamino)benzenesulfonate has been investigated.
The adsorption mechanism obeyed Freundlich isotherm model. FT-IR was used to analyze the adsorbed film
相似文献
63.
Jerry P. Jasinski Ray J. Butcher H. S. Yathirajan B. Narayana L. Mallesha K. N. Mohana 《Journal of chemical crystallography》2009,39(6):453-457
Abstract The title compound, C9H8O4, (I), crystallizes in the monoclinic space group P 21/c with unit cell parameters a = 7.3380(5) ?, b = 9.3790(7) ?, c = 12.3172(9) ?, β = 90.687(7)°, Z = 4. The molecule consists of a benzene ring fused to a 1,4 dioxane ring in a half-chair conformation with a carboxylic acid
group bonded at the dioxane 2-position. The carboxylic acid group forms a classic O–H···O hydrogen bonded dimer with an O···O
distance of 2.6292(12) ? in a R22 (8) graph-set motif which links the molecules into pairs around inversion centers in a supramolecular assembly in the unit
cell. The dihedral angle between the mean planes of the R22 (8) graph-set motif’s of two adjacent dimers in the unit cell is 75.7(5)°. The mean plane of an R22 (8) graph-set motif makes an angle of 88.4(5)° with the mean plane of the benzene ring in the same dimer and 13.1(2)° or
13.4(7)° with the mean plane of a benzene ring from an adjacent dimer. Additional weak Cg π-ring intermolecular interactions significantly influence the bond distances, bond angles and torsion angles of the dioxane
ring and attached carboxyl group. Comparison to a MOPAC AM1computational calculation provides support to these observations.
Graphical Abstract The association of carboxylic acid dimers in the supramolecular assembly of (R)-1,4-benzodioxane 2-carboxylic acid is investigated
by examination of its crystal structure. Its geometric and packing parameters are described and compared to a MOPAC AM1 computational
calculation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
64.
Jerry P. Jasinski Ray J. Butcher L. Mallesha K. N. Mohana H. S. Yathirajan B. Narayana 《Journal of chemical crystallography》2009,39(6):433-437
Abstract The title compound, C13H16O6N3F, features a central furan ring containing four carbon atom chiral centers with a 4-amino-5-fluoro-2-oxopyrimidine group,
two acetyl groups and a methyl group bonded at the 2,3,4,5 positions, each in an absolute R configuration (2R,3R,4R,5R). It
crystallizes in the monoclinic space group C2 with unit cell parameters a = 14.5341(3), b = 7.26230(10), c = 16.2197(3) ?, β = 116.607(2)°, Z = 4. An extensive array of intra and intermolecular hydrogen bond interactions dominate crystal packing in the unit cell
highlighted by a relatively rare three-center proton-bifurcated donor N–H···(O,F) hydrogen bond interaction in cooperation
with a second, (C,N)–H···O bifurcated acceptor three-center hydrogen bond in a supportive fashion. Additional weak Cg π-ring
intermolecular interactions between a fluorine atom and the 4-amino-5-fluoro-2-oxopyrimidine ring in concert with multiple
donor and acceptor hydrogen bonds significantly influence the bond distances, bond angles and torsion angles of the deoxy-5-fluorocytidine
group. Comparison to a MOPAC computational calculation provides support to these observations.
Index Abstract Crystal structure of (2R,3R,4R,5R)-2-(4-amino-5-fluoro-2-oxopyrimidin-1(2H)-yl)-5-methyl-tetrahydrofuran-3,4-diyl diacetate
with dual N–H···(O,F) proton donor bifurcated and (C,N)–H···O bifurcated acceptor three-center hydrogen bond configurations
is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
65.
Dr. Veera Mohana Rao Kakita Mamata V Joshi Prof. Ramakrishna V Hosur 《Chemphyschem》2019,20(12):1559-1566
A novel G-SERF-PSYCHE-TOCSY (gradient encoded selective refocusing in pure shift yielded by chirp excitation version of total correlation spectroscopy) NMR pulse scheme has been proposed, which produces TOCSY chemical shift correlations, on one hand, and scalar coupling values for the spins scalarly coupled to irradiated resonances, by showing them as doublets along the indirect dimension, on the other. Therefore, recording such an experiment, for a group of spins with overlapping chemical shifts, in organic molecules can adequately provide scalar coupling information in a G-SERF manner along the indirect dimensions, and they can be assigned to particular spin pairs. Such COSY chemical shift correlations (which appear as doublets for the scalarly coupled spins) can be readily discriminated from the TOCSY peaks (which do not show such splitting) in the G-SERF-PSYCHE-TOCSY spectrum. 相似文献
66.
The first and the second moments of the multiplicity distribution of prompt gamma rays in spontaneous ternary fission of252Cf have been measured by the multiple coincidence technique. While both these moments were found to be nearly independent
of the energy of the light charged particle accompanying the fission fragments, the width of the multiplicity distribution
was larger than that in the case of normal binary fission by about 20%. 相似文献
67.
Water Molecules in Hydrotalcite‐like Layered Double Hydroxides: Interplay between the Hydration of the Anions and the Metal Hydroxide Layer 下载免费PDF全文
Layered double hydroxides comprise positively charged metal hydroxide layers and intercalated anions. These materials are obtained from aqueous medium both in nature and in the laboratory. Consequently the layered double hydroxides include a considerable amount of water. The presented study was designed to determine the proportion of water associated with the hydration sphere of the anion as opposed to that of the metal hydroxide slab. Among the two differently bound water species observed in all layered double hydroxides, the weakly bound water is associated with the metal hydroxide layer and is lost at 100 °C, whereas the strongly bound water is in the hydration sphere of the anion and is lost at higher temperatures (100 °C ≤ T ≤ 250 °C). This is in contrast to the better known cationic clays, wherein all the intercalated water is generally found to be in the hydration sphere of the cations. Further the water molecules in layered double hydroxides also bond to each other, leading to the incorporation of water in excess of what is predicted by the Miyata formula (Miyata, 1975) based on crystal chemical considerations. The excess water is one of the reasons for the poor crystallinity of layered hydroxides. 相似文献
68.
G. Siva Mohan Reddy T. Narasimhaswamy K. Mohana Raju 《International Journal of Polymer Analysis and Characterization》2015,20(1):10-28
In the present study, the synthesis and characterization of a methacrylic-based side chain liquid crystalline monomer and its polymer were investigated with the aid of both 1-D and 2-D nuclear magnetic resonance (NMR) techniques. The mesophase characteristics of the monomer and polymer were determined by hot-stage optical polarized microscopy (HOPM). The nematic and smectic phases were observed for the monomer and polymer. Furthermore, 13C spin-lattice relaxation time measurements were performed on the above systems in order to monitor molecular dynamics. The present study provides an opportunity to carry out a systematic comparison of the evolution of structural as well as dynamical changes of the monomer and the polymer. 相似文献
69.
A. V. Ratna Prasad K. Balakotesara Rao K. Mohana Rao K. Ramanaiah S. P. Kumar Gudapati 《International Journal of Polymer Analysis and Characterization》2015,20(6):541-556
Natural fiber-reinforced nanocomposites were prepared by incorporating wild cane grass fiber and organically modified montmorillonite (MMT) nanoclay into polyester resin. The composites were formulated up to a maximum volume of fiber of approximately 40% and their mechanical properties were investigated. The mean tensile strength and tensile modulus of nanoclay-filled wild cane grass fiber composites are 6.3% and 18.3% greater than those of wild cane grass fiber composites, respectively, without addition of nanoclay at maximum percentage volume of fiber. The mean flexural strength of nanocomposites at maximum percentage volume of fiber was increased to a maximum of 221 Mpa and flexural modulus to 4.2 Gpa. The mean impact strength of nanoclay-filled wild cane grass fiber composites was increased to 376.7 J/m at maximum percentage volume of fiber. The weight loss of nanoclay-filled wild cane grass fiber/polyester composites was 30% and 22% less than that of composites without nanoclay at maximum percentage volume of fiber. The results indicated that the use of nanoclay showed significant improvement in all the mechanical properties of wild cane grass fiber-reinforced composites. 相似文献
70.
Caffeic Acid Inhibits Chronic UVB‐Induced Cellular Proliferation Through JAK‐STAT3 Signaling in Mouse Skin 下载免费PDF全文