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951.
952.
Flaminio Squazzoni 《Computational & Mathematical Organization Theory》2008,14(4):266-282
This paper aims to illustrate how social sciences, sociology in particular, have theorized on societal transitions. The first
section introduces some preliminary definitions. The assumption is that a societal transition is more than a social, economic
or technological change. It is a large-scale and long-term macro process through which a given social system radically changes
its structural basis, in terms of new socio-technical practices, governance rules, social and economic institutions, cultural
frames, and patterns of social life. The second section provides an excursus on social science accounts on transitions. In
particular, the attention has been given to Norbert Elias’ famous study on the rise and fall of the court society in France,
between 17th and 18th century and to Manuel Castells’ recent analysis of the emergence of the network society. The third section
discusses problems and challenges of standard approaches and suggests some building blocks of societal transition models,
taken from complexity and social simulation literature. The concluding section suggests some way-forward measures towards
a computational social science approach to societal transitions.
相似文献
Flaminio SquazzoniEmail: URL: http://www.unibs.it/on-line/dss/Home/Personale/PersonaleDocente/articolo1758.html |
953.
Francisco Guillé n-Gonzá lez Juan Vicente Gutié rrez-Santacreu. 《Mathematics of Computation》2008,77(263):1495-1524
In this work we develop fully discrete (in time and space) numerical schemes for two-dimensional incompressible fluids with mass diffusion, also so-called Kazhikhov-Smagulov models. We propose at most -conformed finite elements (only globally continuous functions) to approximate all unknowns (velocity, pressure and density), although the limit density (solution of continuous problem) will have regularity. A backward Euler in time scheme is considered decoupling the computation of the density from the velocity and pressure.
Unconditional stability of the schemes and convergence towards the (unique) global in time weak solution of the models is proved. Since a discrete maximum principle cannot be ensured, we must use a different interpolation inequality to obtain the strong estimates for the discrete density, from the used one in the continuous case. This inequality is a discrete version of the Gagliardo-Nirenberg interpolation inequality in domains. Moreover, the discrete density is truncated in some adequate terms of the velocity-pressure problem.
954.
955.
Jeremy C. Palmer Rakesh S. Singh Renjie Chen Fausto Martelli 《Molecular physics》2016,114(18):2580-2585
ABSTRACTRecent computational studies have reported evidence of a metastable liquid–liquid phase transition (LLPT) in molecular models of water under deeply supercooled conditions. A competing hypothesis suggests, however, that non-equilibrium artefacts associated with coarsening of the stable crystal phase have been mistaken for an LLPT in these models. Such artefacts are posited to arise due to a separation of time scales in which density fluctuations in the supercooled liquid relax orders of magnitude faster than those associated with bond-orientational order. Here, we use molecular simulation to investigate the relaxation of density and bond-orientational fluctuations in three molecular models of water (ST2, TIP5P and TIP4P/2005) in the vicinity of their reported LLPT. For each model, we find that density is the slowly relaxing variable under such conditions. We also observe similar behaviour in the coarse-grained mW model of water. Our findings, therefore, challenge the key physical assumption underlying the competing hypothesis. 相似文献
956.
Sicking W Korth HG Jansen G de Groot H Sustmann R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(15):4230-4245
Non-heme iron(III) complexes of 14-membered tetraaza macrocycles have previously been found to catalytically decompose hydrogen peroxide to water and molecular oxygen, like the native enzyme catalase. Here the mechanism of this reaction is theoretically investigated by DFT calculations at the (U)B3LYP/6-31G* level, with focus on the reactivity of the possible spin states of the FeIII complexes. The computations suggest that H2O2 decomposition follows a homolytic route with intermediate formation of an iron(IV) oxo radical cation species (L.+FeIV==O) that resembles Compound I of natural iron porphyrin systems. Along the whole catalytic cycle, no significant energetic differences were found for the reaction proceeding on the doublet (S=1/2) or on the quartet (S=3/2) hypersurface, with the single exception of the rate-determining O--O bond cleavage of the first associated hydrogen peroxide molecule, for which reaction via the doublet state is preferred. The sextet (S=5/2) state of the FeIII complexes appears to be unreactive in catalase-like reactions. 相似文献
957.
The semantic collapse problem is perhaps the main difficulty associated to the very powerful mechanism for combining logics
known as fibring. In this paper we propose cryptofibred semantics as a generalization of fibred semantics, and show that it
provides a solution to the collapsing problem. In particular, given that the collapsing problem is a special case of failure
of conservativeness, we formulate and prove a sufficient condition for cryptofibring to yield a conservative extension of
the logics being combined. For illustration, we revisit the example of combining intuitionistic and classical propositional
logics.
Mathematics Subject Classification (2000): 03B22 (03B35, 03G25, 03G30) 相似文献
958.
Yves Galerne 《The European physical journal. E, Soft matter》2000,3(4):355-368
We propose complements to the Renn model of the liquid crystal TGBC* phase. We argue that the rotation angle per helislab is spontaneously in the radian range, not too small to limit the energy
cost of the twist grain boundaries between the helislabs, not too large to preserve the double twisting efficiency. Taking
the elastic interactions between the helislabs into account, we show that the structure may undergo two different lock-ins,
provided that the uncontrolled interactions at the sample surfaces are small enough. First, for appropriate values of the
elastic constants, an angular lock-in may fix the rotation angle per helislab at values exactly commensurate to π. Three characteristic
lengths of the TGBC* phase, the TGB period and the thicknesses of both the smectic blocks and of the helislabs are then commensurate to one another,
with moreover, integer ratios at the most efficient commensurabilities. The TGBC* phase could thus exist in several versions, incommensurate and commensurate, according to the steps of a restricted Devil's
staircase. A second elastic lock-in should then arise in the commensurate TGBC* phases, to set the arrays of disclination lines between the helislabs in simple rectangular lattices, arranged in a helical
manner. Being placed right behind one another, the disclination lines then coincide when observed along the TGB axis. This
could explain the typical textures with square or hexagonal grids, observed in oriented samples. The commensurability of the
TGBC* phases could be analyzed with X-ray scattering experiments in the same manner as already reported for the TGBC phase.
Received 30 November 1999 and Received in final form 5 May 2000 相似文献
959.
The freezing transition of a network model for tensionless membranes confined to two dimensions is investigated by Monte Carlo
simulations and scaling arguments. In this model, a freezing transition is induced by reducing the tether length. Translational
and bond-orientational order parameters and elastic constants are determined as a function of the tether length. A finite-size
scaling analysis is used to show that the crystal melts via successive dislocation and disclination unbinding transitions, in qualitative agreement with the predictions of the Kosterlitz-Thouless-Halperin-Nelson-Young
theory. The hexatic phase is found to be stable over only a very small interval of tether lengths.
Received 4 June 1999 and Revised in final form 1 September 1999 相似文献
960.
P. Pawłowski B. Borderie G. Auger Ch.O. Bacri N. Bellaize F. Bocage R. Bougault R. Brou P. Buchet J.L. Charvet A. Chbihi J. Colin D. Cussol R. Dayras A. Demeyer D. Doré D. Durand J.D. Frankland E. Galichet E. Genouin-Duhamel E. Gerlic D. Guinet P. Lautesse J.L. Laville J.F. Lecolley R. Legrain N. Le Neindre O. Lopez M. Louvel A.M. Maskay L. Nalpas A.D. Nguyen M. Pârlog J. Péter E. Plagnol M.F. Rivet E. Rosato F. Saint-Laurent S. Salou J.C. Steckmeyer M. Stern G. Tăbăcaru B. Tamain L. Tassan-Got O. Tirel E. Vient C. Volant J.P. Wieleczko 《The European Physical Journal A - Hadrons and Nuclei》2000,9(3):371-383
The prompt component at intermediate velocity of light charged particles is investigated. An improved coalescence model coupled
to the intra-nuclear cascade code ISABEL is used to obtain light complex particle energy spectra and multiplicities as a function
of impact parameter. The results are compared with experimental data from the 36Ar + 58Ni experiment at 95 MeV/nucleon, performed with the INDRA 4π detection system. The calculated prompt component is found to
rather well reproduce proton spectra. For complex light charged particles the calculated components well populate the high
energy part of spectra. Prompt emission can therefore explain the large transverse energies experimentally observed at mid-rapidity.
Received: 27 July 2000 / Accepted: 20 November 2000 相似文献