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21.
The structure of freshly prepared Al(OPh)3, its decomposition product, the hydrolyzed products and their structural evolution were investigated employing 27Al MAS NMR spectroscopy, PXRD, TGA/DTA/DSC/FTIR techniques. In the 27Al MAS NMR spectrum of the aluminium phenoxide, three signals with the chemical shift at 3.78, 21 and 45 ppm were observed.
The chemical shift at 3.78 and 45 ppm revealed the presence of four and sixfold coordinated aluminum. The signal at 21 ppm
corresponded to fivefold coordinated aluminium. When the aluminium phenoxide was directly decomposed in air at 600 °C, it
resulted in amorphous product as evidenced from the PXRD pattern. The observed signals with chemical shifts at 10.1, 42, 73.6 ppm
in the 27Al MAS NMR spectrum indicated the presence of 6, 5 and 4 coordination for the aluminium atoms suggesting disordered transitional
γ-alumina to be the product. The hydrolysis studies of Al(OPh)3 with excess of water at 70 °C yielded bohemite (γ-AlOOH). The alumina obtained after dehydration at 600 °C was X-ray amorphous.
The dehydrated product at 600 °C showed the presence of four and six coordinated aluminium atoms in the 27Al MAS NMR spectrum confirming it to be ordered γ-Al2O3. Crystalline γ-Al2O3 was obtained on further heating at 800 °C. 相似文献
22.
Mukesh Yadav Amita Lavania Radha Tomar G. B. K. S. Prasad Shalini Jain Hariom Yadav 《Applied biochemistry and biotechnology》2010,160(8):2388-2400
In present study, we investigated hypoglycemic and antihyperglycemic potential of five extracts (water, ethanol, methanol,
hexane, and chloroform) of four plants (i.e., seeds of Eugenia jambolana, fruits of Momordica charantia, leaves of Gymnema sylvestre, and seeds of Trigonella foenum graecum) alone and/or in combination with glimepiride in rats. Ethanol extract of E. jambolana, water extract of M. charantia, ethanol extract of G. sylvestre, and water extract of T. graecum exhibited highest hypoglycemic and antihyperglycemic activity (most active) in rats among all the extracts, while hexane
extracts exhibited least activities. Most active extracts were further studied to dose-dependent (200, 100, and 50 mg/kg body
weight (bw)) hypoglycemic and antihyperglycemic effects alone and in combination with glimepiride (20, 10, and 5 mg/kg bw).
The combination of most active extracts (200 mg/kg bw) and lower dose of glimepiride (5 mg/kg bw) showed safer and potent
hypoglycemic as well as antihyperglycemic activities without creating severe hypoglycemia in normal rats, while higher doses
(200 mg/kg bw of most active extracts, and 10 and 20 mg/kg bw of glimepiride) were generated lethal hypoglycemia in normal
rats. From this study, it may be concluded that the ethanol extract of E. jambolana seeds, water extract of M. charantia fruits, ethanol extract of G. sylvestre leaves, and water extract of T. graecum seeds have higher hypoglycemic and antihyperglycemic potential and may use as complementary medicine to treat the diabetic
population by significantly reducing dose of standard drugs. 相似文献
23.
S. Chowta P. K. Mohapatra S. C. Tripathi B. S. Tomar V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(2):309-314
Radiochemical results of U isotopes (234U, 235U and 238U) and their activity ratios are reported for well waters as local sources of drinking waters collected from the ten settlements
around the Semipalatinsk Nuclear Test Site (SNTS), Kazakhstan. The results show that 238U varies widely from 3.6 to 356 mBq/L (0.3–28.7 μg/L), with a factor of about 100. The 238U concentrations in some water samples from Dolon, Tailan, Sarzhal and Karaul settlements are comparable to or higher than
the World Health Organization’s restrictive proposed guideline of 15 μg (U)/L. The 234U/238U activity ratios in the measured water samples are higher than 1, and vary between 1.1 and 7.9, being mostly from 1.5 to
3. The measured 235U/238U activity ratios are around 0.046, indicating that U in these well waters is of natural origin. It is probable that the elevated
concentration of 238U found in some settlements around the SNTS is not due to the close-in fallout from nuclear explosions at the SNTS, but rather
to the intensive weathering of rocks including U there. The calculated effective doses to adults resulting from consumption
of the investigated waters are in the range 1.0–18.7 μSv/y. Those doses are lower than WHO and IAEA reference value (100 μSv/y)
for drinking water. 相似文献
24.
25.
Kar Aishwarya S. Rao Ankita Sahu Manjulata Kumar Shiny S. Tomar B. S. 《Journal of Radioanalytical and Nuclear Chemistry》2017,314(3):1667-1674
Journal of Radioanalytical and Nuclear Chemistry - Plutonium recovery is inevitable from plutonium bearing alumina crucibles generated over the years as part of carbon analysis during chemical... 相似文献
26.
The possibility of plane wave propagation in a micropolar fluid of infinite extent has been explored. The reflection and transmission of longitudinal elastic wave at a plane interface between a homogeneous micropolar fluid half-space and a micropolar solid half-space has also been investigated. It is found that there can exist four plane waves propagating with distinct phase speeds in an infinite micropolar fluid. All the four waves are found to be dispersive and attenuated. The reflection and transmission coefficients are found to be the functions of the angle of incidence, the elastic properties of the half-spaces and the frequency of the incident wave. The expressions of energy ratios have also been obtained in explicit form. Frequency equation for the Stoneley wave at micropolar solid/fluid interface has also been derived in the form of sixth-order determinantal expression, which is found in full agreement with the corresponding result of inviscid liquid/elastic solid interface. Numerical computations have been performed for a specific model. The dispersion curves and attenuation of the existed waves in micropolar fluid have been computed and depicted graphically. The variations of various amplitudes and energy ratios are also shown against the angle of incidence. Results of some earlier workers have been deduced from the present formulation. 相似文献
27.
An integral equation formulation for buoyancy-driven convection problems is developed and illustrated. Buoyancy-driven convection in a bounded cylindrical geometry with a free surface is studied for a range of aspect ratios and Nusselt numbers. The critical Rayleigh number, the nature of the cellular motion, and the heat transfer enhancement are computed using linear theory. Green's functions are used to convert the linear problem into linear Fredholm integral equations. Theorems are proved which establish the properties of the eigenvalues and eigenfunctions of the linear integral operator which appears in these equations. 相似文献
28.
Epsita?Ghanti Nobel?Tomar Prikshit?Gautam R.?NagarajanEmail author 《Journal of Sol-Gel Science and Technology》2011,57(1):12-15
Al(OPh)3 involving sterically hindered phenyl groups on ultrasonic assisted micro hydrolysis yielded a mixture of boehmite and bayerite
as deduced from the FTIR and powder X-ray diffraction pattern. In the thermogravimetric trace, the complete removal of decomposable
moieties of the hydrolyzed gel occurred around 530 °C. Calcining the gel at temperatures 600, 700, 800 and 900 °C showed crystalline
tetragonal δ-Al2O3 to be the product at 900 °C as deduced from FTIR, 27Al NMR and PXRD techniques. δ-Al2O3 showed a surface area of 135 m2/g with rectangular bar like morphology with the sizes below 50 nm in the TEM images. 相似文献
29.
The propagation of plane harmonic waves are studied in a microstretch fluid medium. It is found that five basic waves can propagate at distinct speeds in an infinite linear homogeneous isotropic microstretch fluid. Out of these five waves, one is a longitudinal micro-rotational wave, two are coupled longitudinal waves and remaining two are coupled transverse waves. The longitudinal micro-rotational wave travels independently and is not influenced by the microstretching of the medium, while the coupled longitudinal waves arise due to the presence of microstretching and coupled transverse waves arise due to the presence of micro-rotation in the medium. Speed of propagation of all the waves are found to be complex valued and dispersive at low frequency, but almost non-dispersive at high frequency. Due to complex valued speeds of propagation, all the waves are attenuating but differently. Coupled sets of longitudinal waves reduce to a longitudinal wave of micropolar fluid in the absence of microstretching. Reflection phenomena of a set of coupled longitudinal waves incident obliquely at the free surface of a microstretch fluid half-space has been investigated. Closed formulae for the reflection coefficients are presented and computed numerically for a particular medium. The real and imaginary parts of the complex speeds of all the waves and their corresponding attenuation coefficients have also been studied numerically and depicted graphically against frequency parameter. 相似文献
30.
Amalanathan M Rastogi VK Joe IH Palafox MA Tomar R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(5):1437-1444
The FT-IR and Raman spectra of 3,5-dinitrobenzoic acid (DNBA) have been recorded and analyzed. The equilibrium geometry, various bonding and harmonic vibrational wavenumbers have been calculated with the help of density functional theory (DFT) method. Most of the vibrational modes are observed in the expected range. Mulliken population analysis shows the interactions C-N-O?H-C and C-O?H-C. The most possible interaction is explained using natural bond orbital (NBO) analysis. The strengthening and polarization of the CO bond increases due to the degree of conjugation. HOMO-LUMO energy and the thermodynamic properties are also evaluated. 相似文献