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191.
S.?I.?AndronenkoEmail authorView authors OrcID profile A.?A.?Rodionov S.?K.?Misra 《Applied magnetic resonance》2018,49(4):335-344
Polymer-derived SiCN ceramics, annealed (also referred to as pyrolyzed) at 1000, 1100, and 1285 °C, and doped with Fe(III) acetylacetonate, are investigated by electron paramagnetic resonance (EPR) from 4 to 120 K at X-band (9.425 GHz). In addition, the SiCN ceramic, annealed at 1100 °C, was studied by EPR at 300 K at W-band (93.96 GHz). There was observed a significant increase in EPR linewidth due to dangling bonds (g = 2.001) below 20 K at X-band. The low-field X-band FMR line (g ≈ 12) indicated the presence of ferromagnetic Fe5Si3 crystallites. There were found two EPR lines due to carbon-related dangling bonds: (1) those present as defects on the surface of the free-carbon phase (as sp2 carbon-related dangling bonds with g = 2.0011) and (2) those present within the bulk of carbon phase (as sp3 carbon-related dangling bonds with g = 2.0033). On the other hand, the intense low-field EPR signal observed at X-band was not observed at W-band. As well, there was observed splitting of the single broad EPR signal observed at g = 2.05 at X-band into two signals at W-band at g = 1.99 and g = 2.06, due to two different Fe-containing superparamagnetic nanocrystallites. Two new EPR signals, not observed at X-band, were observed at W-band, namely at g = 2.28 and g = 3.00, which are also due to g∥ of these superparamagnetic nanocrystallites. 相似文献
192.
Debolina Misra Tarun Kumar Kundu 《The European Physical Journal B - Condensed Matter and Complex Systems》2017,90(7):135
A density functional theory + Hubbard U (DFT+U) method is implemented to investigate the catalytic activity of lanthanum nickelate (LaNiO3) for oxygen reduction reaction. Comparison of the surface energies of different LaNiO3 surfaces shows that {001} surface has the lowest surface energy and hence maximum stability. Two possible terminations of the {001} surface namely LaO and NiO2 are considered to carry out all our DFT calculations. Calculation of bond lengths of the atoms near the surface and adsorption energies for the reaction intermediates revealed that LaO terminated {001} surface is unstable for the process of OOH adsorption and hence not preferred for the oxygen reduction reaction. However, NiO2 terminated {001} surface shows excellent catalytic activity for adsorption of all the reaction intermediates and hence is a favourable surface for reactions to occur. Superiority of the NiO2 terminated {001} surface as catalyst over the LaO terminated one, is also confirmed from the total and partial density of states of the surfaces in presence of the adsorbates, which also shows that the desorption rate of the reaction intermediates is low in case of LaO terminated {001} surface compared to the NiO2 terminated one. 相似文献
193.
Granular materials are typically characterized by complex structure and composition. Continuum modeling, therefore, remains the mainstay for describing properties of these material systems. In this paper, we extend the granular micromechanics approach by considering enhanced kinematic analysis. In this analysis, a decomposition of the relative movements of interacting grain pairs into parts arising from macro-scale strain as well as micro-scale strain measures is introduced. The decomposition is then used to formulate grain-scale deformation energy functions and derive inter-granular constitutive laws. The macro-scale deformation energy density is defined as a summation of micro-scale deformation energy defined for each interacting grain pair. As a result, a micromorphic continuum model for elasticity of granular media is derived and applied to investigate the wave propagation behavior. Dispersion graphs for different cases and different ratios between the microscopic stiffness parameters have been presented. It is seen that the model has the capability to present band gaps over a large range of wave numbers. 相似文献
194.
Ambrish Kumar Srivastava Neeraj Misra 《International journal of quantum chemistry》2016,116(7):524-528
LiOH is one of the strong bases among neutral molecules. What about hydroxides of small Lin (n = 2 ? 5) clusters? The addition of a single atom to a cluster sometimes has dramatic effects on its reactivity. This fact motivated us to perform an ab initio MP2/6‐311++G(d, p) investigation on LinOH species (n = 1 ? 5). These LinOH species are stabilized by both ionic as well as covalent interactions, and are found to be stable against elimination of LiOH and OH. We have determined their gas and aqueous phase basicity by considering hypothetical protonation reactions. The calculated proton affinities of LinOH (n ≥ 2) suggest their reduced basicity as compared to LiOH by 50–100 kJ/mol. The NBO charges and the highest occupied molecular orbitals also reveal the electride and alkalide characteristics of Li2OH and Li3OH, respectively. © 2016 Wiley Periodicals, Inc. 相似文献
195.
The dielectric relaxation mechanism in five heterocyclic compounds in dilute solutions using microwave technique is reported.
Measurements have been made at different temperatures in order to calculate dipole moments and free energies of activation
for the process of dipole orientation and viscous flow. It has been observed that the relaxation time is very closely related
with the molecular parameters, such as size, shape and nature of the solute molecule. 相似文献
196.
E. G. Fu Y. Q. Wang G. F. Zou J. Xiong M. J. Zhuo Q. M. Wei J. K. Baldwin Q. X. Jia L. Shao A. Misra M. Nastasi 《Applied Physics A: Materials Science & Processing》2012,108(1):121-126
We studied the effect of irradiation on small angle grain boundaries in mosaic structured Cu thin films. The films showed a decrease in mosaic spread via a narrowing of the full width at half maximum in XRD rocking curves and a smaller minimum yield of RBS channeling after irradiation. These data indicate the irradiation decreased the misorientation angles between mosaic blocks separated by small angle grain boundaries. Mechanisms involving interactions between grain boundary dislocations and irradiation induced defects are discussed. 相似文献
197.
Mohammad Shahid Syed S. Razi Priyanka Srivastava Rashid Ali Biswajit Maiti Arvind Misra 《Tetrahedron》2012,68(44):9076-9084
A new simple organic scaffold based on acenaphthene 4 was designed and synthesized. The chromogenic and fluorogenic properties of 4 toward different metal ions and anions were investigated in H2O/MeCN (8:2, v/v) solution. The probe 4 in the presence of Cu2+ exhibited strong static excimer emission at 507 nm along with a decrease in monomer emission at ~400 nm ratiometrically, attributed to a complexation through aldimine and amide groups of 4. Additionally, 4 upon interaction with different anions illustrated significant fluorescence enhancement with cyanide. However, interaction of complex, 4-Cu2+ with CN? revealed fluorescence quenching attributed to formation of stable [Cu(CN)x]1?x species in the medium. A naked-eye sensitive fluorescent green color of solution was changed to blue. The mechanism of interaction between 4 and Cu2+ and sensing of cyanide through Cu2+ displacement approach was confirmed by the change in optical behaviors and 1H NMR and ESI-MS spectral data analysis. 相似文献
198.
Bappa Acherjee Arunanshu S. Kuar Souren Mitra Dipten Misra 《Optics & Laser Technology》2012,44(5):1281-1289
In this research, a systematic investigation on laser transmission contour welding process is carried out using finite element analysis (FEA) and design of experiments (DoE) techniques. First of all, a three-dimensional thermal model is developed to simulate the laser transmission contour welding process with a moving heat source. The commercial finite element code ANSYS® multi-physics is used to obtain the numerical results by implementing a volumetric Gaussian heat source, and combined convection–radiation boundary conditions. Design of experiments together with regression analysis is then employed to plan the experiments and to develop mathematical models based on simulation results. Four key process parameters, namely power, welding speed, beam diameter, and carbon black content in absorbing polymer, are considered as independent variables, while maximum temperature at weld interface, weld width, and weld depths in transparent and absorbing polymers are considered as dependent variables. Sensitivity analysis is performed to determine how different values of an independent variable affect a particular dependent variable. 相似文献
199.
Rampal PandeyMahendra Yadav Mohammad ShahidArvind Misra Daya Shankar Pandey 《Tetrahedron letters》2012,53(28):3550-3555
Three fluorescent quinazolines thiophen-2-yl-5,6-dihydrobenzo-[4,5]imidazo[1,2-c]quinazoline (1), pyridin-3-yl-5,6-dihydrobenzo-[4,5]imidazo-[1,2-c]quinazoline (2) and phenyl-5,5′,6,6′-dihydrobenzo-[4,4′,5,5′]imidazo-[1.1′,2-c,2′-c]quinazoline (3) have been synthesized. Structures of 1 and 3 have been authenticated crystallographically. Quinazolines 1-3 exhibit highly selective ‘on-off’ switching for Hg2+ ions. The fluorescence intensity displayed a linear relationship with respect to Hg2+ concentration (0.1-1.0 μM; R2 = 0.99) with detection limit of 2.0 × 10−7 M. 相似文献
200.
The paper describes a new method for the calculation of the Sommerfeld screening parameter σ1. It requires neither the knowledge of the energy separations of spin doublet levels nor is it based on the application of
the Hertz law. The only data required for the calculation are the experimental energy values of the level concerned for the
series of elements belonging to the same subshell in which the element in the question is situated. As an illustration the
values of σ1 are calculated for the L
1, L
2 and L
3 levels for elements belonging to the 4f subshell and these are found to be in excellent agreement with those published earlier by Gokhale and Misra. The method brings
out the constancy of σ1 (L
2
L
3)−σ1(L
1) in a natural way and may thus be regarded as providing theoretical explanation of the Hertz law. 相似文献