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71.
Rough crack fronts in a sheet of paper, obtained during a creep experiment, do not follow true scaling laws. Local roughness exponents are estimated using the first order cumulant, a quantity recently introduced in the turbulence literature [J. Delour, J. F. Muzy, and A. Arneodo, Eur. Phys. J. B 23, 243 (2001)10.1007/s100510170074]. Using a large data set (102 fronts), we find a significant difference in local roughness between the slow (subcritical) and the fast growth regime. 相似文献
72.
Bispropargyl sulfones equipped with aromatic rings of dissimilar nature were synthesized. Under basic conditions, these sulfones isomerized to the bisallenic sulfones, creating a competitive scenario between two alternate Garratt-Braverman (GB) cyclization pathways. The observed product distribution ruled out the involvement of any ionic intermediate and supported the diradical mechanism with greater involvement of the electron-rich aromatic ring via the more nucleophilic radical. DFT-based calculations supported the diradical mechanism along with the observed selectivity. 相似文献
73.
A new three-dimensional magnesium formate polymorph, namely, γ-[Mg(3)(O(2)CH)(6)] has been synthesized via in situ formate anion generation method. γ-Mg-formate crystallizes in space group Pbcn, and structural determination by X-ray single crystal diffraction reveals a three-dimensional network of Mg(2+) linked by formate anions. All formate anions possess similar binding mode to the metal center with one oxygen of a particular formate anion binds to one metal center (μ(1) oxygen) and other oxygen binds to two metal centers (μ(2) oxygen). N(2) adsorption studies indicate that the framework displays permanent porosity. The specific surface area of γ-Mg-formate (BET, 120 m(2) gm(-1)) is lower than the α- polymorph (BET, 150 m(2) gm(-1)). However, the initial hydrogen uptake of γ-Mg-formate reached almost 1.0 wt % when the adsorbate pressure approached 760 Torr at 77 K. This is higher than the hydrogen uptake of α-Mg-formate (0.6 wt %). γ-Mg-formate, shows a moderate affinity and capacity for CO(2) (3.4 ? kinetic diameter) at 298 K. The CO(2) uptake at 760 Torr is 2.01 mmol gm(-1) (47.0 cc gm(-1)). Although this CO(2) uptake is somewhat modest, it compares well with the CO(2) uptake of several Mg-MOFs and ZIFs reported in the literature. 相似文献
74.
Babita Mallick Adithya Lakhsmanna Siva Umapathy 《Journal of Raman spectroscopy : JRS》2011,42(10):1883-1890
In this paper, we report on the concept and the design principle of ultrafast Raman loss spectroscopy (URLS) as a structure‐elucidating tool. URLS is an analogue of stimulated Raman scattering (SRS) but more sensitive than SRS with better signal‐to‐noise ratio. It involves the interaction of two laser sources, namely, a picosecond (ps) Raman pump pulse and a white‐light (WL) continuum, with a sample, leading to the generation of loss signals on the higher energy (blue) side with respect to the wavelength of the Raman pump unlike the gain signal observed on the lower energy (red) side in SRS. These loss signals are at least 1.5 times more intense than the SRS signals. An experimental study providing an insight into the origin of this extra intensity in URLS as compared to SRS is reported. Furthermore, the very requirement of the experimental protocol for the signal detection to be on the higher energy side by design eliminates the interference from fluorescence, which appears on the red side. Unlike CARS, URLS signals are not precluded by the non‐resonant background and, being a self‐phase‐matched process, URLS is experimentally easier. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
75.
A new easy-to-synthesize chemosensor, 3,3'-bis(indolyl)-4-chlorophenylmethane (hereafter S), was designed, synthesized and employed as a selective optical chemosensor for fluoride ions.(1)H NMR and density functional studies on the system have been carried out to determine the nature of the interaction between S and X(-) (X = inorganic anions) responsible for the significant fluoride-induced changes in the absorption properties of S. The experimental results reveal that abstraction of an acidic proton of S by the fluoride ion, leading to the formation of anionic species, is responsible for the spectral changes. These changes allow signaling for the fluoride ion to detect and estimate the concentration of fluoride ion present even at the submicromolar level, accurate up to 2 μM. Calculations of the transition energies of S, S(-), and S···F(-) (hydrogen bonded complex) show that only S(-) is responsible for the long-wavelength absorption band in the presence of F(-). 相似文献
76.
This paper is aimed at estimating unknown parameters in a rectangular fin satisfying a predefined temperature. The differential transformation along with simplex method is used. The study has been done for different initial guess, random errors and measurement points. It is observed that, there is unique value of the convection-conduction parameter, but different conductivity and radiative parameters exist which will be useful in adjusting the parameters amongst various alternatives. 相似文献
77.
Biswajit Mallick Ramesh Chandra Behera Simanchal Panigrahi Tanmaya Badapanda Biswanath Parija Banita Behera Manas Panigrahi Madhumita Sarangi 《Indian Journal of Physics》2009,83(4):525-529
Electron microscopy is an important characterization technique for the study of textile fibre as it gives more information
on fabric wear, nature of fibre fracture, chemical degradation, abrasion, fatigue and many others. Electron Probe Micro Analyzer
(EPMA) micrographs of virgin and some neutron-irradiated samples (graphite coated) are discussed. The filament diameter, D, of virgin PET fibre obtained from EPMA study was 12.5 μn. The surface topography of single filament distinctly reveals the
core and sheath parts of the filament. The core diameter of the virgin fibre was estimated to be 1.43 μm. The fibre irradiated
at fluence 1 × 1012 n/cm2 shows radiation induced sphere like polymer balls or spherulites of diameter 2.27 μm in the expanded core region. Due to
irradiation, the sheath area crosslinks with expanded core region, which may be responsible for increase of strength and hardness
of the polymer materials. Moreover, the micrograph at 3000 X magnifications clearly shows that there is no preferred orientation
of the polymer in any direction confirming the isotropic nature of the sample.
相似文献
78.
Mott-Hubbard anti-ferromagnetic insulator, NiO shows p-type semiconducting behaviour due to vacancy at Ni2+ site in its bunsenite structure. We report the modification of structural and magnetic order in NiO on Fe doping. NiO samples
at different Fe concentrations in the range 0 to 5 at.% have been prepared by chemical co-precipitation and post thermal decomposition
method. Both structural and magnetic characterization reveal that with increasing Fe doping concentration, NiO evolves as
a magnetically inhomogeneous state out of the parent homogeneous antiferromagnetic state. In addition, structural inhomogeneity
was also observed with Fe precipitating to γ-Fe2O3 phase, the signature of which could be clearly seen for Fe content beyond 2 at.%. At lower Fe content however, some amount
of Fe occupies lattice and interstitial sites in the NiO matrix and drive the latter to acquire ferromagnetic ordering, which
was evident from a clear hysteresis loop at 300 K.
相似文献
79.
Chandana Rath Sonal Singh P. Mallick D. Pandey N. P. Lalla N. C. Mishra 《Indian Journal of Physics》2009,83(4):415-421
Ferromagentic semiconductors have been actively pursued because of their potential as spin polarized carrier sources and easy
integration into semiconductor technology. One such material, ZnO has been shown to be a potential Diluted Magnetic Semiconductor
(DMS). The appearance of ferromagnetism, however, is found to be sensitive to the processing conditions. We report synthesis
of ZnO nanoparticles of size ∼20 nm by a simple co-precipitation technique using metal nitrates and NaOH as precipitant. The
particles are self-organised and reveal single crystalline behaviour in electron diffraction pattern. Incorporation of Co
in ZnO matrix leads not only to the reduction in crystallite size but also to the modification of the structure. At 5% Co,
the particles are highly textured. The particles also aggregate and the aggregated mass have nearly rectangular shape as seen
through TEM. Increasing Co to 10%, results into further reduction of particle size and the particles self organize in a line,
which looks like nanofibers. This alignment of particles increases by increasing the Co content further. This type of growth
of nanofibers above Co ≥ 10% is well correlated with the anisotropic peak broadening observed in the XRD spectra. In addition,
Co substitute Zn site up to 20% without showing any extra phase in XRD spectra as compared to 7 to 10% in case of bulk. Transport
and magnetic studies indicate that conductivity increases with increasing Co content, but carrier mediated ferromagnetism
is absent down to 10 K.
相似文献
80.
P. Mallick S. Majumder D.C. Agarwal D.K. Avasthi N.C. Mishra 《Applied Surface Science》2009,256(2):521-523
NiO nanoparticle thin films grown on Si substrates were irradiated by 107 MeV Ag8+ ions. The films were characterized by glancing angle X-ray diffraction and atomic force microscopy. Ag ion irradiation was found to influence the shape and size of the nanoparticles. The pristine NiO film consisted of uniform size (∼100 nm along major axis and ∼55 nm along minor axis) elliptical particles, which changed to also of uniform size (∼63 nm) circular shape particles on irradiation at a fluence of 3 × 1013 ions cm−2. Comparison of XRD line width analysis and AFM data revealed that the particles in the pristine films are single crystalline, which turn to polycrystalline on irradiation with 107 MeV Ag ions. 相似文献