全文获取类型
收费全文 | 304篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 171篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 95篇 |
物理学 | 44篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2017年 | 5篇 |
2016年 | 4篇 |
2015年 | 5篇 |
2014年 | 15篇 |
2013年 | 18篇 |
2012年 | 9篇 |
2011年 | 12篇 |
2010年 | 15篇 |
2009年 | 5篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2003年 | 7篇 |
2002年 | 4篇 |
2001年 | 3篇 |
1987年 | 4篇 |
1982年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1971年 | 4篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1967年 | 3篇 |
1966年 | 7篇 |
1965年 | 6篇 |
1964年 | 3篇 |
1963年 | 5篇 |
1962年 | 5篇 |
1961年 | 7篇 |
1960年 | 8篇 |
1959年 | 4篇 |
1958年 | 4篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1947年 | 7篇 |
1946年 | 6篇 |
1945年 | 2篇 |
1944年 | 3篇 |
1943年 | 2篇 |
1942年 | 3篇 |
1941年 | 5篇 |
1940年 | 2篇 |
排序方式: 共有314条查询结果,搜索用时 15 毫秒
101.
The LRS Bianchi type-I and type-II string cosmological models are studied when the source for the energy momentum tensor is a bulk viscous stiff fluid containing one dimensional strings together with zero-mass scalar field. We have obtained the solutions of the field equations assuming a functional relationship between metric coefficients when the metric is Bianchi type-I and constant deceleration parameter in case of Bianchi type-II metric. The physical and kinematical properties of the models are discussed in each case. The effects of Viscosity on the physical and kinematical properties are also studied. 相似文献
102.
M. Gowrisankar P. Venkateswarlu K. Sivakumar S. Sivarambabu 《Journal of solution chemistry》2013,42(5):916-935
Densities, ρ, viscosities, η, and ultrasonic sound velocities u of pure methyl isobutylketone, diethylketone, cyclopentanone, cyclohexanone, 2-methyl cyclohexanone and those of their binary mixtures with N-methyl aniline were measured at 303.15 K over the entire composition range. These experimental data have been used to calculate the excess volume (V E), deviation in ultrasonic sound velocity (?u), isentropic compressibility (κ s ), intermolecular free length (L f), excess intermolecular free length ( $ L_{\text{f}}^{\text{E}} $ L f E ), acoustic impedance (Z), excess isentropic compressibility ( $ \kappa_S^{\text{E}} $ κ S E ), deviation in viscosity (?η) and excess Gibbs energy of activation of viscous flow (G *E). The viscosity data have been correlated using three equations proposed by Grunberg and Nissan, Katti and Chaudhri, and Hind et al. The excess/deviations have been fitted by Redlich–Kister equation and the results are discussed in terms of molecular interactions present in these mixtures. 相似文献
103.
R. Kishore Kumar K. Siva Kumar N. V. V. Jyothi J. Rajasekhar P. Venkateswarlu 《Journal of Analytical Chemistry》2013,68(5):403-408
An enrichment separation procedure for the atomic absorption spectrophotometric determinations of Cu(II) and Ni(II) ions in common edible fishes was established. The 2-[(2-hydroxynaphthalen-1-yl)diazenyl]-5-methylbenzene-1,3-diol (HNDMD) complexes of the analyte ions at pH 6.0 were adsorbed on the p-octylpolyethylene glycolphenylether (Triton X-100) column and then desorbed with 10 mL of acetone. Under optimized conditions, the recovery values were above 95%. The developed preconcentration methods were successfully applied to the determination of Cu(II) and Ni(II) ion concentrations in common edible fishes from the local market. The precision and accuracy of the method are very good. 相似文献
104.
Sudina Purushotham Reddy Baggu Chinnababu Yenamandra Venkateswarlu 《Helvetica chimica acta》2014,97(7):999-1003
The first concise stereoselective total synthesis of diarylheptanoid rhoiptelol C ( 1 ) was achieved from readily available vanillin. The synthesis involves Keck's asymmetric allylation, olefin cross metathesis, and Sharpless asymmetric dihydroxylation reaction as key steps. 相似文献
105.
C. Venkateswarlu Y. C. Ratnakaram M. Seshadri D. Thirupathi Naidu 《Brazilian Journal of Physics》2011,41(4-6):281-289
The optical absorption and emission spectra of two different Ho3+ doped mixed alkali chloroborate glasses have been studied in the ultraviolet-visible near-infrared regions. Various spectroscopic parameters like Racah (E1, E2, and E3), spin orbit (ξ4f), and configuration interaction (α) parameters have been calculated. From the measured spectral intensities of the various absorption bands of Ho3+ ion, the Judd–Ofelt intensity parameters (Ω2, Ω4, and Ω6) have been evaluated and covalency was studied as a function of x in the glass matrices. Using these parameters, radiative transition probabilities, radiative lifetimes, branching ratios, and integrated absorption cross-sections have been calculated and reported for certain excited states of Ho3+ ion. From the emission spectra, stimulated emission cross-sections are determined for the emission transitions, 5F4, 5S2?→?5I8, and 5F5?→?5I8 in these two mixed alkali chloroborate glasses. An attempt has been made to throw some light on the environment of Ho3+ ions in these glass systems by studying the variation in various spectroscopic parameters. 相似文献
106.
Proceedings - Mathematical Sciences - The addition of cyanoacetamide to the double bond of 7-methoxy and 7-hydroxycoumarins is very slow and it is attributed to the influence of the substituents... 相似文献
107.
108.
I. Prakash N. Nallamuthu P. Muralidharan M. Venkateswarlu Manjusri Misra Amar Mohanty N. Satyanarayana 《Journal of Sol-Gel Science and Technology》2011,58(1):24-32
In situ base catalyst assisted sol–gel process is used for the synthesis of nanocrystalline CoFe2O4 deposition on SiO2 particles. The SiO2 particles were prepared using base catalyst assisted sol–gel process and the consecutive formation and deposition of nanocrystalline
CoFe2O4 on SiO2 particles was monitored using Powder X ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermo Gravimetric
And Differential Thermal Analysis (TG/DTA), Scanning Electron Microscopy and Energy Dispersive X ray Spectroscopy (SEM–EDS)
and High Resolution Transmission Electron Microscopy (HRTEM). The crystallite size of CoFe2O4 is calculated using Scherrer’s formula and it is found to be 8 nm. The HRTEM images and selective area electron diffraction
(SAED) results confirmed the formation of nanocrystalline CoFe2O4 particles deposited over SiO2 spheres. 相似文献
109.
110.
The thermal behaviour of (NH4)3VO2F4 and Na(NH4)2VO2F4 was investigated using TG, DTA and DSC techniques. The occurrence of a first order phase transition with the onset of decomposition in both the compounds is confirmed. The temperature, energetics and hysteresis of the transition are obtained. A possible path for the thermal degradation is given for both the compounds, and the residues are identified. 相似文献