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181.
P. Srinivasa Rao 《Journal of Non》2011,357(21):3585-3591
The variation in physical, structural and electrical properties has been studied as a function of Bi2O3 content in 20ZnF2-(10 + x) Bi2O3-(70-x) P2O5, 0 ≤ x ≤ 10 mol% glasses, which were prepared by melt quenching technique and characterized by differential thermal analysis (DTA). Colorless samples, which have no absorption peaks, are obtained for 10 and 12 mol% of Bi2O3 and the glasses are slowly becoming brownish from 15 to 20 mol% of Bi2O3 which exhibit two absorption peaks at ~ 370 nm, ~ 450 nm correspond to Bi° transitions 4S3/2 → 2P3/2 and 4S3/2 → 2P1/2 respectively. The decrease in 3P1 → 1S0 transition of Bi3+ photo luminescence emission for 18 and 20 mol% of Bi2O3 and increase in optical absorption area shows the reduction of Bi3+ to Bi°. From FTIR studies it is observed that an addition of Bi2O3 decreases the P―O―P covalent bond by forming P―O―Bi bonds due to high polarizing nature of Bi3+ ions. Dielectric parameters like ε', tan δ and a.c. conductivity σac are found to increase and activation energy for a.c. conduction is found to decrease with the increase in the concentration of Bi2O3. Density of defect energy states is found to increase for higher concentration of Bi2O3 and is discussed according to quantum mechanical tunneling (QMT) model. 相似文献
182.
N. Srinivasa RaoL. Srinivasa Rao Ch. Srinivasa RaoB.V. Raghavaiah V. Ravi KumarM.G. Brik N. Veeraiah 《Physica B: Condensed Matter》2012,407(4):581-588
The glasses of the composition (40−x) PbO-15Bi2O3-45As2O3-xCoO, with 0≤x≤0.6 mol% in the steps of 0.1 were synthesized. The dielectric properties viz., dielectric constant, loss and ac conductivity over moderately larger ranges of frequency and temperature were investigated. The results were analyzed with the aid of the data on optical absorption and IR spectra. The analysis indicated that there is an increase in the insulating strength of the glasses with increase in the concentration of CoO up to 0.4 mol%. 相似文献
183.
A. Srinivasa Rao B. Rupa Venkateswara Rao J.V. Shanmukha Kumar J.L. Rao 《Physica B: Condensed Matter》2009,404(20):3717-3721
Nd3+ doped fluorine containing zinc-aluminophosphate glasses have been prepared with alkali and alkaline earth content to understand the effect of network modifiers on radiative process. The physical and optical properties of these glasses have been evaluated. The Judd-Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Ω2, Ω4 and Ω6 for each glass. Using these parameters, transition probability (A), total transition probability (AT), branching ratios (βR) radiative life times (τR) and integrated cross-section (σa) for the stimulated emission have been theoretically calculated for certain excited Nd3+ fluorescent levels. From the obtained results the conclusion is made about the possibility of using these glasses as laser material. 相似文献
184.
Srinivasa R. Pullela Jingyi Shen Manuel Marquez Zhengdong Cheng 《Journal of Polymer Science.Polymer Physics》2009,47(9):847-854
Environment‐sensitive poly(N‐isopropylacrylamide) (PNIPAM) microgel particles with covalently bonded ruthenium(4‐vinyl‐4′‐methyl‐2,2′‐bipyridine) bis (2,2′‐bipyridine) [Ru(vmbipy)(bipy)2] display periodic size changes when placed in Belousov‐Zhabotinsky (BZ) reaction substrates. The temperature dependency of the induction time and oscillatory frequency of the BZ reaction in this polymer‐immobilized catalyst system were compared to the bulk BZ reaction with the catalyst in the solution phase. Prolonged induction times are observed for the immobilized catalyst, compared with free catalyst, while little difference is observed on the oscillation frequency. The Arrhenius frequency factor calculated using the induction time for the immobilized catalyst BZ reaction is about seven times smaller than that for the free catalyst Ru(bipy) case. On the other hand, the Arrhenius frequency factors calculated using the oscillatory frequency are almost the same, showing similar reaction kinetics during the BZ oscillations. The tunability of the induction time using a polymer matrix, as we observed here, while maintaining similar oscillatory behavior, should provide a new dimension to control the self‐assembling of BZ active particles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 847–854, 2009 相似文献
185.
Vibrational Spectra of Distorted Structure Molecules by Using Lie Algebraic Techniques: an Application to Copper and Magnesium Octaethyl Porphyrin 下载免费PDF全文
Srinivasa Rao Karumuri 《中国物理快报》2010,27(10):80-83
Using a U (2) algebraic model the fundamental stretching vibrations of copper octaethyl porphyrin and magnesium octaethyl porphyrin are calculated for 24 vibrational bands. The locality parameter ξ confirms the highly local behavior of the stretching modes of these porphyrin molecules. The model Hamiltonian so constructed appears to describe the vibrational energy levels accurately. 相似文献
186.
Chaganti Srinivasa Reddy Prabir Kumar Patra Chapal Kumar Das 《Macromolecular Symposia》2009,277(1):119-129
A comparative study of the structural, thermal, mechanical and thermomechanical properties of ethylene-octene copolymer 1 1 Ethylene-octene copolymer is produced using Dow's INSITETM ™ constrained geometry catalyst and process technology. ENGAGE the trade name of this copolymer. (mPE) 2 2 This copolymer will be represented as mPE . nanocomposites synthesized with pure nanosilica (NS) and nanosilica-functionalized with diglycidyl ether of bisphenol-A (ENS) has been reported. These nanocomposites were prepared using “melt mixing” method at a constant loading level of 2.5 wt. %. The effects of pure nanosilica (NS) and epoxy resin-functionalized-nanosilica (ENS) on the above mentioned properties of ethylene-octene copolymer were analyzed by wide-angle-x-ray diffractometer (WAXD), transmission electron microscope (TEM), thermo gravimetric analyzer (TGA), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM). TEM studies have shown a better dispersion of nanoparticles in case of ethylene-octene copolymer-epoxy resin-functionalized-nanosilica nanocomposite (mPE-ENS) than that of ethylene-octene copolymer-nanosilica nanocomposite (mPE-NS). The tensile tests show that organic modification of nanosilica particles brings up an appreciable increase in yield strength, ultimate tensile strength and elongation at break of the polymer. DMA studies have shown an increase in the storage modulus and glass transition temperature for mPE-ENS with respect to mPE-NS. Further, the TGA results have shown a higher thermal stability for mPE-ENS in comparison to mPE-NS. 相似文献
187.
Core–shell CdS/ZnS nanoparticles in arachidic acid film were prepared through a novel Langmuir–Blodgett (LB) approach. Post-deposition treatment of the precursor LB multilayers of cadmium arachidate with H2S gas followed by intercalation of Zn2+ ions and further sulfidation result in the formation of CdS/ZnS nanoparticles in the LB film. The formation of these nanoparticles and resulting changes in layered structures were studied by FTIR and X-ray reflection measurements. The optical properties were studied using UV–vis absorption and photoluminescence spectroscopy. A red-shift in the absorption spectrum and enhancement of CdS excitonic emission together with reduction of surface states emission suggest that after the intercalation step, a thin layer of ZnS surrounds the CdS nanoparticles, thus forming a core–shell structure. Subsequent to the second sulfidation, a further red-shift in absorption suggests the formation of a thicker ZnS coating on CdS. Electron diffraction of CdS nanoparticles coated with thicker ZnS showed the diffraction patterns of only ZnS, as expected for core–shell structures. 相似文献
188.
R Srinivasa Chakrawarthy 《Pramana》1999,53(3):407-407
In the present talk I will discuss some ‘rare’ aspects of the E2 band structures and the novel features concerning the dipole bands in this mass region. Reliable and accurate lifetimes have been measured using coincidence recoil distance method. The results of 129,130Ba will be discussed. In contrast to the predictions of the tilted axis cranking model, the dipole bands in Sb-Xe-Ba nuclei can be nicely described as high-K prolate bands. New data from multi-detector arrays has established extended bands structure, their decay to low lying states have been established and the angular correlation supports the predominant, ΔI=1 character. Finally the sensitive measures, i.e. B(M1) rates of the tilted axis model are compared with the high-K formula based on 1-dim cranking model. 相似文献
189.
190.
Benzimidazole‐based silver(I)–N‐heterocyclic carbene complexes as anti‐bacterials: synthesis,crystal structures and nucleic acids interaction studies 下载免费PDF全文
Patrick O. Asekunowo Rosenani A. Haque Mohd. R. Razali Srinivasa Budagumpi 《应用有机金属化学》2015,29(3):126-137
A series of new benzimidazolium salts as N‐heterocyclic carbene (NHC) precursors has been synthesized. Reactions of these salts with Ag2O with varying metal‐to‐salt ratio facilitate the formation of a series of new binuclear and mononuclear Ag(I)–NHC complexes. All compounds were characterized using physicochemical and spectroscopic techniques. Single‐crystal X‐ray diffraction study reveals a binuclear structure for one of the complexes and a mononuclear one for two others. These complexes exist as cationic Ag(I)–NHC complexes with the chelation of carbene carbons to the silver centre in an almost linear manner. The compounds were screened for their anti‐bacterial activities against Staphylococcus aureus (ATCC 12600) as a Gram‐positive bacterium and Escherichia coli (ATCC 25922) as a Gram‐negative bacterium. The results show that both bacteria appear markedly inhibited. Furthermore, the results suggest the possibility of steric variation as a modulation of the anti‐bacterial activities. The nuclease activities of the compounds were assessed using gel electrophoresis and the results indicate that these complexes can cleave or degrade DNA and RNA via a non‐oxidative mechanism. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献