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121.
K. Venkateswarlu F.A.Sc. S. Mariam Mariamma P. Mathew 《Proceedings Mathematical Sciences》1965,62(3):159-168
A normal co-ordinate analysis of ethylene oxide, ethylene oxide-d4 and ethylene sulphide is carried out and the potential energy constants are determined using both the most general quadratic potential function and Urey-Bradley force field. Using the potential energy constants obtained by the former method the mean amplitudes of vibration of these molecules are calculated by the secular equation method. The thermodynamic properties of these molecules are reported for the ideal gaseous state at one atmosphere pressure for eleven temperatures from 100° K. to 1000° K. 相似文献
122.
Venkateswarlu K Venisetty RK Yellu NR Keshetty S Pai MG 《Journal of chromatographic science》2007,45(8):537-539
A new simple, sensitive, and reproducible high-performance thin-layer chromatography method for the estimation of alprazolam and sertraline in combination is developed using silica gel plates with fluorescent indicators. The system is equipped with an automated sample applicator, and the detection was performed at 254 nm by using UV absorption densitometry. The mobile phase consists of carbon tetrachloride, methanol, acetone, and ammonia in the ratio 12:3:5:0.1. The retention factor values for alprazolam and sertraline are found to be 0.52 and 0.70, respectively. The limit of detection of alprazolam and sertraline in the mixture of given proportion is observed to be 0.05 microg/mL and 2.5 microg/mL and the limit of quantitation is 0.2 microg/mL and 10 microg/mL, respectively. The method has shown good linearity in the range of 0.2 microg/mL to 0.65 pg/mL for alprazolam (R2 > 0.9953) and 10 pg/mL to 32.5 microg/mL for sertraline (R2 > 0.9942). The intra- and inter-assay (n=5) variations in the linear range are less than 4% for alprazolam and 6% for sertraline. Three pharmaceutical products containing this combination are analyzed to test the applicability of the new method. The percentage of alprazolam and sertraline in the tablets studied range from 97.7% to 102.82% and 96.5% to 99.9%, respectively. 相似文献
123.
Radiolysis of ferrous ammonium sulphate (FAS) dispersed in (a) alkali nitrates [KNO3, NaNO3, Ba(NO3)2, CO(NH3)6(NO3)3] (b) alkali halides [KCl, KBr] and (c) binary mixtures of above [KNO3 + KCl, Ba(NO3)2 + BaCl2) has been extensively investigated. FAS becomes oxidized and Fe3+ formation seems to depend upon the nitrate concentration and gamma dose but is independent of halide concentration. Mossbauer studies confirm these findings and it appears that basic ferric sulphate may be formed during the oxidation process. 相似文献
124.
Dasari Ramesh Singanaboina Rajaram Peddikotla Prabhakar Udugu Ramulu Dorigondla Kumar Reddy Yenamandra Venkateswarlu 《Helvetica chimica acta》2011,94(7):1226-1233
A simple asymmetric total synthesis of stagonolide G ( 1 ) is described. Asymmetric dihydroxylation, regioselective epoxide ring opening, and vinyl Grignard reactions are involved in generating the stereogenic centers C(4) and C(8), followed by Grubbs‐II‐catalyzed ring‐closing metathesis (RCM). 相似文献
125.
Ultraviolet photolysis assisted mineralization and determination of trace levels of Cr, Cd, Cu, Sn, and Pb in isosulfan blue by ICP-MS 总被引:1,自引:0,他引:1
K. Dash G. Venkateswarlu S. Thangavel S.V. Rao S.C. Chaurasia 《Microchemical Journal》2011,98(2):312-316
Isosulfan blue dye is used in sentinel node mapping technique to evaluate breast cancer patients where determination of different trace elements is required. A UV-photolysis assisted mineralization of isosulfan blue is described here for the determination of trace elements (Cr, Cd, Cu, Sn and Pb) by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). In the present study advanced oxidation processes such as UV, UV/H2O2, and UV/H2O2/HNO3 have been assessed and compared for the degradation and mineralization of isosulfan blue dye. The extent of mineralization was determined on the basis of total organic carbon (TOC) measurement. The adopted procedure (UV/HNO3/H2O2) provided very low TOC content (0.5%), corresponding to a mineralization efficiency of > 99%. With the present procedure, the use of dynamic reaction cell (DRC) or collision cell was not required for chromium determination which suffers interference from the presence of carbon. Method detection limits were 0.0028, 0.0021, 0.016, 0.007, and 0.005 μg g? 1 for Cr, Cd, Cu, Sn and Pb respectively. The values obtained by the proposed method were cross-validated by those obtained by ETAAS analysis. The expanded uncertainties in the measurement at 95% confidence level (coverage factor 2) are in the range of 13.7–25.8%. 相似文献
126.
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
127.
D. Ramesh V. Shekhar D. Chantibabu S. Rajaram U. Ramulu Y. Venkateswarlu 《Tetrahedron letters》2012,53(10):1258-1260
The stereoselective total synthesis of bio-active pectinolide H (1) is described. Midland’s asymmetric reduction, Sharpless dihydroxylation reactions are involved in generating the stereogenic centers at C-4′, C-5 and C-1′. Other key steps in the synthesis are Sonogashira cross coupling, Z-selective Still–Gennari olefination, one-pot acetonide deprotection–lactonization, and Lindlar’s reaction. This offers a distinctive strategy for the synthesis of γ-lactones. 相似文献
128.
Tertiary Butyl Nitrite Triggered Nitration of Phenols: Solvent‐ and Structure‐Dependent Kinetic Study
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Nitration of phenols with tertiary butyl nitrite (TBN) obeyed second‐order kinetics with a first‐order dependence on [TBN] and [phenol] under acid‐free conditions. Reaction rates were significantly altered by a change in the dielectric constant and other physical properties of solvent. The rate of nitration increased with an increase in temperature (303–323 K) in different solvent media (acetonitrile, dichloroethane, CCl4, dimethyl formamide (DMF), and toluene). The rates of nitration (log k) could not fit into either Amis or Kirkwood plots [log k’ vs. (1/D) or [(D – 1)/(2D + 1)], but the trends were better explained by the basic form of multivariate linear solvent energy relationships (MLSER) suggested by the Koppel and Palm approach on the one hand and the Kamlet and Taft approach on the other hand. These observations probably substantiate that cumulative contributions of basic solvent parameters (equilibrium as well as frictional solvent effects) and solvent–solute interactions for solvation of transition state during nitration of phenols. Reaction rates accelerated with the introduction of electron‐donating groups and retarded with electron‐withdrawing groups. Accordingly, the reactivity of structurally different phenols was found to follow the following sequence: p‐OH > p‐MeO > p‐Me > H > m‐Me > p‐Cl > p‐Br > m‐Cl > p‐NO2 > m‐OH. The results are interpreted by Hammett's theory of linear free energy relationship. The reaction constant (Hammett's ρ) is a measure of the sensitivity of the reaction toward the electronic effects of the substituent. The rho (ρ) values obtained from the present experiments are fairly large negative values (ρ < 0), indicating attack of an electrophile on the aromatic ring. An increase in temperature decreases the reaction constant (ρ) values. According to Exner, ρ values for a given reaction are influenced by the temperature according to the following relation: ρ = A [1 – β/T]. Obtained “isokinetic temperature (β)” values are in the range of 225–290. These values are far below the experimental temperature range (303–323 K), indicating that the entropy factors are probably more important in controlling the reaction. This point can be seen from the negative entropy values and linearity of multiple linear regression analysis (MLRA). Furthermore, in the present study, rate constants for TBN nitration of ortho‐substituted phenols could not fit into Taft's plots of log(k/kCH3) versus σ* or, Es or combined Taft's relationship. However, Charton's MLRA of the log k with polar, resonance, steric, hydrophobicity, and molar refractivity showing a very good linear relationship was obtained. It is of interest to note that when log kexp values are correlated with log kcal a perfect linearity is obtained with a correlation coefficient of unity, indicating the consonance between experimental and calculated rate constants in the present work. 相似文献
129.
130.
Free-radical-induced DNA damage by ionizing radiation leads to a number of oxidized purines, of which 7H-8-oxoguanine (8OG) and 7H-8-oxoadenine (8OA) are predominant and known to cause an appreciable amount of cellular damage. A detailed quantum mechanical study at various levels of theory in both the gas phase and in an aqueous solution has been carried out in order to assess the tautomeric preferences of the bases. The calculated energies of various plausible tautomers suggest that at higher levels of ab initio theory with inclusion of electron correlation, the 8-keto-6-enolic form of 8-oxoguanine (8OG2) would predominate over the 6,8-diketo form (8OG1) in the gas phase whereas the 6-amino-8-keto form (8OA1) predominates over the other possible tautomers of 8-oxoadenine. Aqueous solvation, however, changes the gas-phase order for 8-oxoguanine, 8OG1 turning out to be the major tautomeric species in an aqueous medium. The estimated free energies of hydration by polarized continuum models are indicative that the mutagenically significant amounts of minor tautomeric forms of 8-oxoguanine and 8-oxoadenine exist in the aqueous phase and might be held responsible for inducing transversional as well as transitional mutations. 相似文献