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81.
Frank H. Stillinger 《Journal of statistical physics》1976,15(5):407-421
Classical lattice gases consisting of structureless particles (with spin) have been quantized by introducing a kinetic energy operator that produces nearest-neighbor hops. Systematic quantum corrections for the partition function and the particle distribution functions appear naturally as power series inX =
2/2ml
2 (
–1 =k
B
T,m is the mass,l is a distance related to lattice spacing). These corrections require knowledge of certain particle displacement probabilities in the corresponding classical lattice gases. Leading-order corrections have been derived in forms that should facilitate their use in computer simulation studies of lattice gases by the standard Monte Carlo method. 相似文献
82.
The repulsive ground electronic state X2Σ+ of HeH is strongly coupled to the Rydberg states at small interatomic distances. Such large couplings also occur between
some of the Rydberg states. HeH+ ions that capture an electron in a Rydberg state end up in separated He and H atoms by indirect predissociation. This paper
presents a study of potential functions and pertinent matrix elements involving the lowest electronic states: the 2Σ+ states, X, A, C, and D, and the 2Π states B and E. Individual transition rates as well as total radiative and non-radiative lifetimes have been computed for
the lowest vibrational and rotational levels.
Received: 22 June 1998 / Accepted: 21 August 1998 / Published online: 12 October 1998 相似文献
83.
Sheela Kirpekar Hans Jørgen Aagaard Jensen Jens Oddershede 《Theoretical chemistry accounts》1997,95(1-2):35-47
Summary Using the quadratic response function at theab initio SCF level of approximation we have calculated the relativistic corrections from the spin-orbit Hamiltonian,H
SO, to the indirect nuclear spin-spin coupling constants of XH4 (X = C, Si, Ge, and Sn). We find that the spin-orbit contributions toJ
X-H are small, amounting only to about 1% forJ
Sn-H. For the geminal H-H coupling constants the relativistic corrections are numerically smaller than forJ
X-H, but in some cases relatively larger compared to the actual magnitude ofJ
H-H. We also investigate the use of an effective one-electron spin-orbit Hamiltonian rather than the fullH
SO in the calculation of these corrections. 相似文献
84.
For the potentialV(x)=V
0 tan2
x, the corrections to the lowest orderjwkb (Bohr-Sommerfeld) energy quantization rule are non-zero. These higher order corrections are explicitly computed using the
formalism of Dunham. The resultingjwkb series for the energy eigenvalues is summable, and yields the exact bound state spectrum. 相似文献
85.
86.
J. Ku?era V. Havránek I. Krausová 《Journal of Radioanalytical and Nuclear Chemistry》2009,281(1):123-129
A new set of reference air filters was prepared for proficiency testing of laboratories involved in air pollution studies
organized by the International Atomic Energy Agency (IAEA). The set consists of one filter loaded with airborne particulate
matter (APM) and one blank filter. Target values and their standard deviations were established using instrumental neutron
activation analysis (INAA) and proton induced X-ray emission (PIXE) with proven accuracy. Rutherford backscattering (RBS)
was used to help in deriving the necessary corrections in PIXE. Losses of individual elements from APM due to the wet deposition
procedure were evaluated. 相似文献
87.
The vertical excitation energies for a comprehensive test set of about 150 singlet excited states of 28 medium-sized organic molecules computed using two variants of the completely renormalised (CR) equation-of-motion (EOM) coupled-cluster (CC) method with singles, doubles, and non-iterative triples, abbreviated as δ-CR-EOMCCSD(T), and the analogous two variants of the newer, left-eigenstate δ-CR-EOMCC(2,3) approach are benchmarked against the previously published CASPT2, CC3, and EOMCCSDT-3 results, as well as the suggested theoretical best estimate (TBE) values. The δ-CR-EOMCC approaches are also used to identify and characterise about 50 additional excited states, including several states having substantial two-electron excitation components, which have not been found in the previous work and which can be used in future benchmark studies. It is demonstrated that the non-iterative triples corrections to the EOMCCSD excitation energies defining the relatively inexpensive, single-reference, black-box δ-CR-EOMCC approaches provide significant improvements in the EOMCCSD data, while closely matching the results of the iterative and considerably more expensive CC3 and EOMCCSDT-3 calculations and their CASPT2 and TBE counterparts. It is also shown that the δ-CR-EOMCC methods, especially δ-CR-EOMCC(2,3), are capable of bringing the results of the CC3 and EOMCCSDT-3 calculations to a closer agreement with the CASPT2 and TBE data, demonstrating the utility of the cost-effective δ-CR-EOMCC methods in applications involving molecular electronic spectra. We show that there may exist a relationship between the magnitude of the triples corrections defining δ-CR-EOMCC approaches and the reduced excitation level diagnostic resulting from EOMCCSD. 相似文献
88.
The variational method with mutilconfiguration interaction wave function is used to obtain the energies, fine structures, and hyperfine structures of high‐lying core‐excited quartet states 1s2lnl' 4Po(m) (m = 1–5) and 1s2pnp 4P(m) (m = 1–5) in Li‐like N4+ and F6+ ions, including the mass polarization and relativistic corrections. Restricted variational method is carried out to extrapolate a better energy. The oscillator strengths, lifetime, wavelengths, fine structure, and hyperfine structure for this system are also investigated to compare with other theoretical and experimental data in the literature. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
89.
Dirk H.J. Poot Wouter Pintjens Marleen Verhoye Annemie Van Der Linden Jan Sijbers 《Magnetic resonance imaging》2010
Echo planar imaging (EPI) is an ultrafast magnetic resonance imaging (MRI) technique that allows one to acquire a 2D image in about 100 ms. Unfortunately, the standard EPI images suffer from substantial geometric distortions, mainly originating from susceptibility differences in adjacent tissues. To reduce EPI distortions, correction methods based on a field map, which is a map of the off-resonance frequencies, have been developed. In this work, a nonlinear least squares estimator is used to optimize the estimation of the field map of the B0 field. The model of the EPI and reference data includes parameters for the phase evolution, the complex magnitude, the relaxation of the MRI signal and the EPI-specific phase difference between odd and even echoes, and from these parameters, additional corrections might be computed. The reference data required to estimate the field map can be acquired with a modified EPI-sequence. The proposed method is tested on simulated as well as experimental data and proves to be significantly more robust against noise, compared to the previously suggested method. 相似文献
90.
Landau theory used for studying hot rotating nuclei usually uses zero temperature Strutinsky smoothed total energy for the
temperature dependent shell corrections. This is replaced in this work by the temperature dependent Strutinsky smoothed free
energy. Our results show that this replacement has only marginal effect for temperatures greater than 1 MeV but plays significant
role at lower temperatures. 相似文献