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81.
Ming LC Sharma SK Jayaraman AJ Kobayashi Y Suzuki E Endo S Prakapenka V Yang D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(10):2418-2422
Both X-ray diffraction and Raman spectroscopy measurement were carried out on the same powder sample of CuGeO(3)(III) in a diamond anvil cell to high pressures at room temperature. The phase transformation of (III)-(IV) phase was observed at about 7GPa with both methods and the results were also in accord with previous powder diffraction and Raman measurements, respectively. However, the powder diffraction data were strikingly different from those reported in a recent single-crystal study on the phase (III). It is, therefore, evident that the phase transformations in CuGeO(3)(III) would be as complicated as those in CuGeO(3)(I) and that the monoclinic phase obtained from single-crystal phase (III) at approximately 7GPa is not the phase (IV) previously observed but rather a new phase (IVa) in CuGeO(3). 相似文献
82.
Sonja Fuchs Arumugam Jayaraman Ivo Krummenacher Laura Haley Marta Batovanovi Maximilian Fest Krzysztof Radacki Holger Helten Holger Braunschweig 《Chemical science》2022,13(10):2932
We report that the outcome of the tin–boron exchange reaction of a mixed thiophene-benzo-fused stannole with aryldibromoboranes is associated with the steric bulk of the aryl substituent of the borane reagent, leading to either boroles or large diboracycles as products. NMR spectroscopic studies indicate that the two products can reversibly interconvert in solution, and mechanistic density functional theory (DFT) calculations reveal boroles to be intermediates in the formation of the diboracyclic products. The addition of Lewis bases to the diboracycles leads to the corresponding borole adducts, demonstrating that they react as “masked” boroles. Additionally, the reaction of the title compounds with a series of organic azides affords complex heteropropellanes, formally 2 : 1 borole-azide adducts, that deviate from the usual BN aromatic compounds formed via nitrogen atom insertion into the boroles.Diboramacrocycles are a new form of borole dimers, participating in various addition reactions as “masked” boroles. The reaction of a less crowded diboramacrocycle with organic azides affords unprecedented complex heteropropellanes. 相似文献
83.
We describe a simulation method to design surfaces for recognizing specific monomer sequences in copolymers. We fix the monomer sequence statistics of the AB copolymers on a surface containing two types of sites and allow the simulation to iterate towards an optimal surface pattern that can recognize and selectively adsorb the sequence in the copolymer. During the simulation the surface pattern is designed by switching identities of two randomly picked sites. For copolymers with less blocky sequences the designed surfaces recognize the correct sequence well when the segment-surface interactions dominate over the intersegment interactions. For copolymers with more blocky sequences recognition is good when the segment-surface interactions are only slightly stronger than the intersegment interactions. 相似文献
84.
Juan G. Andrade Jayaraman Chandrasekhar Paul Von Ragu Schleyer 《Journal of computational chemistry》1981,2(2):207-211
Molecular orbital calculations on the C4H2 potential energy surface indicate singlet trialene (1) not only to be thermodynamically unstable, but also to have negligible barriers to interconversion to diacetylene. 相似文献
85.
K.H. Bray Mahavir jain K.S. Jayaraman G. LobiancoG.A. Moss W.T.H. Van OersD.O. Wells 《Nuclear Physics A》1972
The elastic and inelastic scattering of protons from 6Li has been studied at incident energies of 25.9, 29.9, 35.0, 40.1 and 45.4 MeV. The 2.18 MeV (3+, T = 0) first excited state of 6Li was found to be strongly excited, but the 3.56 MeV (0+, T = 1) second excited state was quite weakly excited. Angular distributions for excitation of the 2.18 MeV level were measured at all five energies, while angular distributions for excitation of the 3.56 MeV level were extracted only at 25.9 and 45.4 MeV. To test the applicability of the optical model for the scattering of protons from such a light nucleus the elastic scattering angular distributions have been analyzed using the eleven-parameter search code SEEK. Available polarization angular distributions were included in the analysis. Reasonable fits to the data have been obtained with an average geometry potential. Theoretical estimates of the real part of the optical potential and the inelastic scattering differential cross sections have been made using the microscopic model for proton-nucleus scattering. Both phenomenological and realistic forces have been considered and the necessary nuclear transition densities have been extracted from experimental elastic and inelastic electron scattering data. An estimate of a possible spin-spin term in the optical potential has also been made. 相似文献
86.
1,2-Hydride shift barriers in classical carbenium ions increase with decreasing ring size; this can be attributed to the increased strain of the H bridged structures in the small rings. 相似文献
87.
Sm4Bi3 has the anti-Th3P4 (cubic) structure with three Sm2+ ions and one Sm3+ ion. The compound undergoes a first-order, isostructural transition at about 26 kbar. The resistance abruptly decreases by a factor of three and the volume by about 10%. The Sm2+ ions undergo a change towards the 3+ state in the transition and the material goes from semimetallic to a metallic state. The behavior of the resistance anomaly suggests termination of the phase boundary at a critical point. 相似文献
88.
We report the existence of a volume collapsed strongly mixed valent state at pressures above 65 K bars in the prototype “concentrated Kondo” system CeAl2 and discuss the relevant energy scales and general phase diagram of CeAl2. To our knowledge this is the first demonstrated example of what should be a large class of systems exhibiting the full diversity of ground states of an Anderson lattice. 相似文献
89.
90.
The unsteady dispersion of a solute, when the fluid is driven through a curved channel with absorbing walls by an imposed
pulsatile pressure gradient, is studied using the method of moments. The study examines the effect of oscillatory Reynolds
number, amplitude/frequency of the pressure pulsation and boundary absorption on the longitudinal dispersion. The methodology
involves a set of unsteady integral moment equations obtained by applying the Aris-Barton method of moments on the convective-diffusion
equation for a curved channel. Central moments are obtained from the moment equations which are solved by a finite-difference
implicit scheme. The effect of curvature and boundary absorption on the effective dispersion coefficient from the initial
to the stationary stage of the oscillatory flow is studied. Amplitude of the effective dispersion coefficient is found to
increase with curvature and decrease with frequency of the pressure pulsation. For large Peclet number and Schmidt number,
the amplitude of the dispersion coefficient can be 1.6 times that in a straight channel at large times. Also, for large times,
the amplitude of the dispersion coefficient is twice the amplitude of the dispersion coefficient as α, the frequency parameter
changes from 0.5 to 1.0. The axial distributions of mean concentration are determined from the first four central moments
by using the Hermite polynomial representation. The effect of curvature is to delay the stationary state and also the approach
to normality of the concentration distribution. The study has importance in understanding the spreading of pollutants in tidal
basins and natural current fields. 相似文献