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151.
Study of a serie of isocoumarins by 13C and 17O NMR spectrometry and AM1 method is reported. These methods gave valuable informations on electronic effect and the structure of isocoumarins. 相似文献
152.
Samples of Bi4Ca x V2? x O11?(3 x /2)?δ in the composition range 0.07 ≤ x ≤ 0.30 were prepared by conventional solid state reactions. The stability of different phases as a function of composition was analysed by X-ray powder diffraction, FT-IR spectra, differential thermal analysis and AC impedance spectroscopy. For the compositions x ≤ 0.10, monoclinic α-phase structure is retained at room temperature. For x = 0.13, orthorhombic β-phase is observed, whereas for x ≥ 0.17, high O2?conducting tetragonal γ-phase is stabilised. However, the highest ionic conductivity σ300°C = 3.27 × 10?4 S cm?1 was observed for x = 0.17. This higher value of conductivity of the substituted compound as compared to the parent compound can be attributed to the increased oxygen ion vacancies generated as a result of cation doping. AC impedance spectroscopy reveals the fact that this ionic conductivity is mainly due to the grain contribution. 相似文献
153.
Samples of bismuth lead vanadium oxide (BIPBVOX) (Bi2V1–xPbxO5.5–x/2) singly substituted system in the composition range 0.05 ≤ x ≤ 0.20 were prepared by sol–gel synthesis route. Structural investigations were carried out by using a combination of differential thermal analysis (DTA) and powder X-ray diffraction (PXRD) technique. Energy dispersive X-ray spectroscopy analysis (EDXA) of doped samples was carried out to predict the sample purity and doping concentration. Transitions, α?β, β?γ and γ′?γ were detected by XRD, DTA and variation in the Arrhenius plots of conductivity. The ionic conductivity was measured by AC impedance spectroscopy. The solid solutions with composition x ≤ 0.07 undergo α?β phase transition, at 329 °C and β?γ phase transition at 419 °C. The highly conducting γ′-phase was effectively stabilized at room temperature for compositions with x ≥ 0.17 whose thermal stability increases with Pb content. At 300 °C, the highest value of conductivity 6.234 × 10?5 S cm?1 was obtained for composition x = 0.15 and at 600 °C the highest value of conductivity 0.65 S cm?1 is observed for x = 0.17. AC impedance plots reveal that the conductivity is mainly due to the grain contribution to oxide ion conductivity. 相似文献
154.
13C and 17O NMR chemical shifts for a series of isobenzopyrylium salts are reported. The oxygen signal range from 300 to 270 ppm as a double bonded carboxylic oxygen, From the 17O and 13C data valuable informations on the conjugative and substituent effects of isobenzopyrylium salts were obtained. 相似文献
155.
Saba Hemmati Alireza Sedrpoushan Nazanin Soudalizadeh Kaveh Khosravi Malak Hekmati 《应用有机金属化学》2019,33(10)
A green palladium (Pd)‐based catalyst supported on Rosa canina fruit extract‐modified graphene oxide [Pd nanoparticles (NPs)/reduced graphene oxide (RGO)‐Rosa canina] hybrid materials has been used as a recoverable and heterogeneous nanocatalyst for cyanating aryl halides using K4[Fe (CN)6] as the resource of cyanide. The nitriles were achieved in good to high yield, and the catalyst can be recovered and reused for up to seven cycles with no remarkable decrease in its catalytic activity. 相似文献
156.
Akbar Ali Muhammad Khalid Saba Abid Javed Iqbal Muhammad Nawaz Tahir Abdul Rauf Raza Julio Zukerman-Schpector Marcio Weber Paixão 《应用有机金属化学》2020,34(3):e5399
The pyridine-based halogenated hydrazone derivatives (E)-N′-benzylidene-2-[(6″-chloroazin-2″-yl)oxy]acetohydrazide ( 6a ), (E)-N′-(3′-chlorobenzylidene)-2-[(6″-chloroazin-2″-yl)oxy]acetohydrazide ( 6b ) and (E)-N′-(3′-bromobenzylidene)-2-[(6″-chloroazin-2″-yl)oxy]acetohydrazide ( 6c ) have been obtained using 6-chloro-2-hydroxypyridine. The structure of the products ( 6a – c ) has been verified using X-ray crystallography and spectroscopic approaches. A single-crystal X-ray diffraction (SC-XRD) investigation showed that the structures are stabilized by intermolecular attractive forces. Additionally, density functional theory (DFT) has been adopted to explore the structural properties, vibrational spectra, noncovalent interactions and frontier molecular orbitals using the B3LYP/6-311 + G(d,p) level. The nonlinear optical properties of the title compounds were calculated using the CAM-B3LYP/6-311 + G(d,p) level. Frequency analysis confirmed the stability of the molecules, and an excellent correlation was observed between the DFT- and SC-XRD-based structural parameters. The SC-XRD analysis confirmed that the dimers of 6a , 6b and 6c are linked by hydrogen-bonding interactions. Natural bond orbital (NBO) analysis also reconfirmed the strength of intermolecular hydrogen-bonding and hyperconjugative interactions. NBO investigation was also utilized to analyze the atomic charges. Moreover, Fourier transform infrared and natural population analyses endorsed that there are significant N&bond;H⋅⋅⋅O&dbond;C hydrogen-bonding linkages in dimeric structures of the compounds. The hydrogen-bonding network and different sorts of hyperconjugative interactions are the main reasons for the stability of the products in the solid state. The highest occupied and lowest unoccupied molecular orbital energies and first-order nonlinear optical properties of these molecules are reported. The quantum chemical parameters were derived using frontier molecular orbital energies. 相似文献
157.
Muhammad Usman Kiran Saba Adnan Jahangir Muhammad Kamran Nazeer Muhammad 《Acta Mechanica Solida Sinica》2018,(3)
The effect of electromechanical fields, i.e., polarization fields, on the efficiency droop of GaN-based light-emitting diodes is presented using both experimental and numerical analyses.The role of incorporating such polarization charge density in device performance is numerically investigated and further compared with the experimental results of internal quantum efficiency of three different devices in consideration. 相似文献
158.
Andrew E. Noble Saba Karimeddiny Alan Hastings Jonathan Machta 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(1):7
We extend the theory of quasipotentials in dynamical systems by calculating, within a broad class of period-doubling maps, an exact potential for the critical fluctuations of pitchfork bifurcations in the weak noise limit. These far-from-equilibrium fluctuations are described by finite-size mean field theory, placing their static properties in the same universality class as the Ising model on a complete graph. We demonstrate that the effective system size of noisy period-doubling bifurcations exhibits universal scaling behavior along period-doubling routes to chaos. 相似文献
159.
Taniya Manzoor Saba Niaz Altaf Hussain Pandith 《International journal of quantum chemistry》2019,119(18):e25979
We report the theoretical modeling of various azo-bridged coumarin-purpurin systems. The effect of varying the donor (coumarin) part of this D-π-D-π-A system was analyzed in terms of opto-electronic and photovoltaic parameters such as HOMO, LUMO, HOMO-LUMO energy gap, λmax, light harvesting efficiency, charge injection efficiency, open voltage, reorganization energy by employing density functional theory as incorporated in Gaussian 03 set of codes. The dye-TiO2 adsorbed systems were also studied using the same level of theory. It was found that just by varying the donor, although of same nature, there is a marked effect on the efficiency parameters of the dye sensitized solar cells based on such dyes. Also, the dye molecules were found to be good sensitizers for TiO2 semiconductors. 相似文献
160.
Atukuri Dorababu Ravindra R. Kamble Saba Kauser J. Shaikh Shilpa M. Somagond Praveen K. Bayannavar Shrinivas D. Joshi 《Journal of heterocyclic chemistry》2019,56(9):2430-2441
3‐Arylsydnones are reported to possess striking pharmaceutical potency. α‐Aminoketone, a biologically active structural unit, is built at the fourth (electrophilic) position of sydnone and further derivatized with secondary amine and tetrazoles. The α‐aminoketone derivatives of sydnones coupled with secondary amines 4a – n were docked on enoyl acyl carrier protein (ACP) reductase from Mycobacterium tuberculosis, which revealed that compounds 4b , 4f , and 4i showed efficient C score values with different binding modes and hydrogen bonding. Further, these compounds were screened for antimycobacterial activity; among them, compound 4f displayed sensitivity at 6.25 μg/mL compared with the standard drug (Streptomycin) against M. tuberculosis (H37RV strain). In addition to this, α‐aminoketone derivatives of sydnones coupled with tetrazoles 8a – h were evaluated for antifungal activity. In the antifungal activity, compound 8b has exhibited potent activity at 6.25 μg/mL against Candida albicans and compound 8g at 0.4 μg/mL against Aspergillus fumigatus. The antifungal activities are comparatively better than standard antifungal agent Fluconazole at these drug concentrations. Alongside characterization of the final compounds by Fourier transform infrared, mass, 1H NMR, and 13C NMR spectral analyses, compounds 8b and 8g were confirmed by X‐ray crystallographic studies. 相似文献