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411.
Vandana Tripathi Lagy T Baby PV Madhusudhana Rao SK Hui R Singh JJ Das P Sugathan N Madhavan AK Sinha 《Pramana》1999,53(3):535-539
The ground state and excited state transfer yields for the 2-neutron pickup channel in the 28Si+68Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the
measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled
channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from
the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV. 相似文献
412.
Bivash R Behera Subinit Roy P Basu M K Sharan S Jena M Satpathy SK Datta L Satpathy ML Chatterjee 《Pramana》1999,53(3):563-566
Time of flight and energy of fission fragments were measured using pulsed beam. Fission fragment mass and energy integrated
angular distributions were extracted. Fission fragment anisotropy was explained in the framework of saddle point model. 相似文献
413.
414.
T Madhusoodhanan Samit Mandal MP Sathyavathiamma Ramani NG Puttaswamy TS Mudhole A Mandal DK Avasthi R Shyam SK Datta 《Pramana》1999,53(3):541-544
The inclusive and exclusive measurements were carried out for 7Li projectile breakup on 27Al target at 48 MeV. In the inclusive data we have observed a broad peak around the beam velocity for alphas and tritons.
The exclusive data for alpha-triton coincidences show good agreement with the post-form DWBA theory of breakup reactions. 相似文献
415.
Measurement of elastic and quasielastic reaction cross sections were done in 16O + 118Sn system at two different energies above the barrier. Attempts are being made to understand the results in the framework
of coupled reaction channel model. 相似文献
416.
In the present paper we have investigated the self-focusing behaviour of radially symmetrical rippled Gaussian laser beam
propagating in a plasma. Considering the nonlinearity to arise from relativistic phenomena and following the approach of Akhmanov
et al, which is based on the WKB and paraxial-ray approximation, the self-focusing behaviour has been investigated in some detail.
The effect of the position and width of the ripple on the self-focusing of laser beam has been studied for arbitrary large
magnitude of nonlinearity. Results indicate that the medium behaves as an oscillatory wave-guide. The self-focusing is found
to depend on the position parameter of ripple as well as on the beam width. Values of critical power has been calculated for
different values of the position parameter of ripple. Effects of axially and radially inhomogeneous plasma on self-focusing
behaviour have been investigated and presented here. 相似文献
417.
R.A. Ritchie H.G. Miller F.C. Khanna 《The European Physical Journal A - Hadrons and Nuclei》2001,10(1):97-100
Based on recent studies of the temperature dependence of the energy and specific heat of liquid nuclear matter, a phase transition
is suggested at a temperature ∼ 0.85 MeV. We apply the Landau-Ginzburg theory to this transition and determine the behaviour
of the energy and specific heat close to the critical temperature in the condensed phase.
Received: 29 July 2000 / Accepted: 20 October 2000 相似文献
418.
Theoretical studies on the stability and electronic structure of small carbon clusters assuming chain, ring, bowl, and fullerene structures have been carried out using a linear combination of atomic orbitals molecular orbital approach within a density functional formalism. Our studies on clusters containing between 12 and 60 atoms indicate three regimes for the growth and formation of carbon clusters. In clusters containing less than 20 atoms, the most stable geometry is the ring arrangements. Between 20 and 28 atoms, clusters with very different geometry have comparable energies. For clusters with larger than 30 atoms, the fullerene structures are the most stable structures. An analysis of the electronic structure shows a distinct correlation between the geometry and the nature of electronic states. 相似文献
419.
A representation theory for Lie groups is developed taking the Hilbert space, say
, of the w*-algebra standard representation as the representation space. In this context the states describing physical systems are amplitude wave functions but closely connected with the notion of the density matrix. Then, based on symmetry properties, a general physical interpretation for the dual variables of thermal theories, in particular the thermofield dynamics (TFD) formalism, is introduced. The kinematic symmetries, Galilei and Poincaré, are studied and (density) amplitude matrix equations are derived for both of these cases. In the same context of group theory, the notion of phase space in quantum theory is analysed. Thus, in the non-relativistic situation, the concept of density amplitude is introduced, and as an example, a spin-half system is algebraically studied; Wigner function representations for the amplitude density matrices are derived and the connection of TFD and the usual Wigner-function methods are analysed. For the Poincaré symmetries the relativistic density matrix equations are studied for the scalar and spinorial fields. The relativistic phase space is built following the lines of the non-relativistic case. So, for the scalar field, the kinetic theory is introduced via the Klein–Gordon density-matrix equation, and a derivation of the Jüttiner distribution is presented as an example, thus making it possible to compare with the standard approaches. The analysis of the phase space for the Dirac field is carried out in connection with the dual spinor structure induced by the Dirac-field density-matrix equation, with the physical content relying on the symmetry groups. Gauge invariance is considered and, as a basic result, it is shown that the Heinz density operator (which has been used to develope a gauge covariant kinetic theory) is a particular solution for the (Klein–Gordon and Dirac) density-matrix equation. 相似文献
420.
M. Chekerker A. F. Santos Faqir C. Khanna M. Ladrem 《International Journal of Theoretical Physics》2017,56(9):2838-2847
Parity violation implies that physics laws are not invariant under spatial coordinate reversal. Electron-positron scattering is a process that displays parity violation. Using the Thermo Field Dynamics formalism this scattering at finite temperature is analyzed. The transition amplitude is calculated as a function of temperature. The parity violation at very high temperatures tend to go to zero. 相似文献