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21.
Reactions of [ZnAl2(OPri)8] [A] with acetoxime in different molar ratios in refluxing anhydrous benzene, yield complexes of the type [ZnAl2(OPri)8?n{(CH3)2CNO}n] {where, n = 1–4}. All the complexes are transparent viscous/foamy solids. They were characterized by elemental analyses, FT-IR and NMR (1H, 13C {1H}) spectral studies. 27Al NMR spectrum of [ZnAl2(OPri)4{(CH3)2CNO}4] [4] in CDCl3 suggests presence of four coordination around both the aluminum atoms. IR spectra suggest that the oximato ligands bind the aluminum atoms in a side on manner in all the complexes. The ESI-mass spectrum of the representative derivative [4] suggests its monomeric nature while the thermo-gravimetric curve shows its low thermal stability. Sol–gel transformations of the precursors (A), (1), and (4) yielded nano-sized ZnAl2O4 samples (a), (b) and (c) at ~500 °C, respectively. The XRD patterns of (a), (b) and (c) indicate formation of cubic phase nano-sized zinc aluminate in all the samples. Surface morphologies of these samples were investigated by SEM images. IR spectra as well as EDX analyses indicate formation of pure zinc aluminate in all the cases. TEM image of sample (c) shows spherical (~5–8 nm) morphology. 相似文献
22.
Archana Chaudhary Nikita Sharma Meena Nagar Shaikh M. Mobin Pradeep Mathur Rakesh Bohra 《Journal of Sol-Gel Science and Technology》2014,70(3):464-472
Modification of [VO(OPri)3] with oximes in different molar ratios, yielded new class of vanadia precursors, [VO{OPri}3?n{L}n] {where, n = 1–3 and LH = C9H16C=NOH (1–3) and (CH3)2C=NOH (4–6)}.All the products are yellow in colour. (1) and (2) are liquid/viscous liquid, while others are solids. Molecular weight measurements of all these derivatives and the ESI-mass spectral studies of (1), (2), (3) and (5) indicate their monomeric nature. 1H and 13C{1H} NMR spectra suggest that the oximato moieties are monodentate in solution which was further confirmed by the 51V NMR signals, appeared in the region expected for tetra-coordinated oxo-vanadium atoms. On ageing, a disproportionation reaction occurs in (1) and some crystals appeared. Single crystal X-ray diffraction analyses of the crystals obtained from (1) as well as from (3) were found to be the same and indicate the presence of side-on {dihapto η 2-(N, O)} binding modes of the oximato ligands, leading to the formation of seven coordination environment around the vanadium atom. Thermogravimetric curve of (1) exhibits multi-step decomposition with the formation of V2O5 as the final product at ~850 °C. Sol–gel transformation of (3) yielded (a) VO2 sintered at 300 °C and (b) V2O5 at 600 °C. Similarly, sol–gel transformations of (1) and (2) yielded V2O5 (c) and (d) at 600 °C, respectively. Formation of monoclinic phase in (a) and orthorhombic phase in (b), (c) and (d) were confirmed by powder XRD patterns. 相似文献
23.
Archana Chaudhary Ram Gopal Meena Nagar Rakesh Bohra 《Journal of Sol-Gel Science and Technology》2014,69(1):102-106
Some oxime modified complexes of the type [Zr{OPri}4?n{L}n] {where, n = 1–4 and LH=(CH3)2C=NOH (1–4) and C9H16C=NOH (5–8)} have been synthesized by the reaction of [Zr(OPri)4·PriOH] with oximes, in anhydrous refluxing benzene. These synthesized complexes were characterized by elemental analyses, molecular weight measurements, ESI-mass, FT-IR and NMR (1H and 13C{1H}) spectral studies. The ESI-mass spectral studies indicate dimeric nature for [Zr{OPri}2{ONC(CH3)2}2] (2), [Zr{OPri}3{ONC10H16}] (5) and [Zr{OPri}{ONC10H16}3] (7) and monomeric nature for [Zr{ONC10H16}4] (8). Oximato ligands appear to bind the zirconium in side on manner in all the complexes. Thermogravimetric curves of (2) and (8) exhibit multi-step decomposition with the formation of ZrO2, under nitrogen atmosphere. Sol–gel transformations of precursors (5), (6), (7) and (8) in organic medium, yielded nano-sized tetragonal phase of zirconia samples (a), (b), (c) and (d), respectively, on sintering at ~600 °C. All these samples were characterized by Powder XRD patterns and EDX analyses. Surface morphologies of these samples were investigated by SEM images. 相似文献
24.
A simple and efficient three-component procedure has been developed for the synthesis of a series of spiro-isoxazolo[5,4-b]pyridines/quinolines by one-pot condensation of isatins, 3-methylisoxazol-5-amine and enolizable cyclic carbonyl compounds. The protocol has been accomplished under solvent-free conditions by grinding the components at room temperature in presence of catalytic CH3COOH. The described process offers environmentally benign reaction conditions for the synthesis of pharmacologically important spirooxindole fused heterocycles with the advantages ofoperational simplicity, short reaction time and good to excellent yields of isolated pure product. 相似文献
25.
Fast ion conducting solid electrolytes are becoming increasingly important owing to their application in solid state ionic devices. The present work deals with the silver ion conducting x AgI – (1–x)Ag2Cr2O7 electrolyte system. These electrolytes have been characterised by X-ray diffraction, electrical conductivity, electronic conductivity and thermoelectric power techniques. A high ionic conductivity of the order of 10−3 S/cm has been observed for the composition mol% 80 AgI–20 Ag2Cr2O7, at room temperature. The electronic conductivity of this electrolyte is three orders of magnitude lower than the ionic conductivity. 相似文献
26.
B. Nalini S. Selvasekarapandian J. Jayashree K. Hariharan 《Crystal Research and Technology》1994,29(3):439-442
The Conductivity of AgI–CuI system has been studied. Two molar ratios of the system Ag1–xCuxI with x = 0.05 and 0.15 have been taken. The transition temperatures are observed with conductivity measurements. 相似文献
27.
Hariharan P Myers MR Robinson RA Maruvada SH Sliwa J Banerjee RK 《The Journal of the Acoustical Society of America》2008,123(3):1706-1719
A new approach for characterizing high intensity focused ultrasound (HIFU) transducers is presented. The technique is based upon the acoustic streaming field generated by absorption of the HIFU beam in a liquid medium. The streaming field is quantified using digital particle image velocimetry, and a numerical algorithm is employed to compute the acoustic intensity field giving rise to the observed streaming field. The method as presented here is applicable to moderate intensity regimes, above the intensities which may be damaging to conventional hydrophones, but below the levels where nonlinear propagation effects are appreciable. Intensity fields and acoustic powers predicted using the streaming method were found to agree within 10% with measurements obtained using hydrophones and radiation force balances. Besides acoustic intensity fields, the streaming technique may be used to determine other important HIFU parameters, such as beam tilt angle or absorption of the propagation medium. 相似文献
28.
Post-sintering annealing effect on the diffuse phase transition in (Pb1−xBax)(Yb0.5Ta0.5)O3 ceramics
Dibyaranjan Rout K. Hariharan V.R.K. Murthy 《Journal of Physics and Chemistry of Solids》2005,66(5):809-816
The effect of post sintering annealing on the dielectric response of (Pb1−xBax)(Yb0.5Ta0.5)O3 ceramics in the diffuse phase transition range (x=0.2) has been investigated. The samples are prepared by conventional solid-state reaction method. The samples are sintered at 1300 °C for 2 h and annealed at different temperatures (800, 900 and 1000 °C) for 8 h and at 800 °C for different time durations (8, 12 and 24 h). A significant change in the dielectric response has been observed in all the samples. The dielectric constant increases remarkably and the dielectric loss tangent decreases. The dielectric peaks of the annealed samples are observed to be more diffused with noticeable frequency dispersion compared to the as sintered sample. 相似文献
29.
Neeraj Sharma Meena Kumari Reena Sharma 《Journal of Thermal Analysis and Calorimetry》2012,107(1):225-229
The thermal decomposition behavior of oxovanadium(IV)hydroxamate complexes of composition [VO(acac)(C6H5C(O)NHO)] (I), [VO(C6H5C(O)NHO)2] (II), [VO(acac)(4-ClC6H4C(O)NHO)] (III), [VO(4-ClC6H4C(O)NHO)2] (IV) (where acac = (CH3COCHCOCH3
–) synthesized from the reactions of VO(acac)2 with equi- and bimolar amounts of potassium benzohydroxamate and potassium 4-chlorobenzohydroxamate in THF + MeOH solvent
medium has been studied by TG and DTA techniques. TG curves indicated that complexes I, II, and IV undergo decomposition in
single step to yield VO2 as the final residue, while complex III decomposes in two steps to yield VO(acac) as the likely intermediate and VO2 as the ultimate product of decomposition. The formation of VO2 has been authenticated by IR and XRD studies. From the initial decomposition temperatures, the order of thermal stability
for the complexes has been inferred as IV > I > III > II. 相似文献
30.
Nanocrystalline tungsten oxides (WO3−δ) are currently receiving a lot of attention because of their interesting electrical, magnetic, optical and mechanical properties. In this report, we present the synthesis of PEG assisted tungsten oxide (WO3) nanoparticles by simple household microwave irradiation (2.45 GHz) method. The samples were characterized using powder X-ray diffraction (XRD), thermal analysis (TG/DTA), transmission electron microscopy (TEM), UV-visible diffusion reflectance spectroscopy (UV-VIS-DRS), cyclic voltammetry and electrochemical impedance spectroscopy. Powder XRD results revealed that both the samples prepared with and without surfactant crystallize in the orthorhombic structure corresponding to WO3·H2O phase. Subsequent annealing under identical conditions (600 °C/air/6 h) led to significantly different products i.e. monoclinic W17O47 from surfactant free sample and orthorhombic WO3 from PEG assisted sample. Blue emission was observed through UV-VIS-DRS with blue shift and the band gap energy was estimated as 2.7 and 3.28 eV for PEG assisted as prepared (WO3·H2O) and annealed samples (WO3) respectively. Electrochemical measurements have been performed on all the samples deposited on the surface of glassy carbon (GC) electrode which showed high sensitivity and good selectivity for PEG assisted sample (WO3·H2O) for the direct detection of l-dopa. 相似文献