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991.
Pang Ruicao Zhang Yanli Li Chenghua Gao Juncheng 《Radiation Physics and Chemistry》1993,42(4-6):857-858
In order to implement the “Law of metrology of the People's Republic of China” for guaranteeing the product quality of radiation processing, safeguarding State's interest and people's health, promoting the progress of radiation processing techniques, SBTS and SCST have jointly issued “the Provisional Regulation of Metrological Supervision and Management for Radiation Processing”, according to present situation of ionizing radiation measurement in radiation precessing plants. This is an administrative rule, which provides the regulation of radiation measurement licence for radiation precessing plants. SBTS has decided to establish the State Office of Technical Examination for Measurement Licence of Radiation Processing, which is attached to the National Institute of Metrology (NIM). Its main tasks include establishment of examination plans for radiation processing licence, organization of technical examination and other works related to the measurement regulation and performance of measurement supervision and regulation inradiation processing fields. 相似文献
992.
993.
Peter Hänggi Peter Jung Christine Zerbe Frank Moss 《Journal of statistical physics》1993,70(1-2):25-47
The phenomenon of stochastic resonance is studied in the presence of colored noise. Several sources of colored noise are introduced and the consequences for the asymptotic time-periodic probability and the (phase-averaged) power spectrum are discussed. Based on space-time symmetry considerations, selection rules for the occurrence of-spikes in the power spectrum are derived. The effect of colored noise on the amplification of small periodic signals is studied in terms of effective, time-periodic Fokker-Planck equations: In overdamped systems driven by colored noise, we find that SR is suppressed with increasing noise color. In contrast, for colored noise induced by inertia (as well as for asymmetric dichotomic noise), one obtains an enhancement of SR. This latter result is obtained by studying the Kramers equation perturbed by a small periodic force. 相似文献
994.
Stochastic resonance in surface catalytic oxidation of carbon monoxide induced by colored noise 总被引:1,自引:0,他引:1
GONG Yubing HOU Zhonghuai & XIN Houwen . Department of Chemical Physics University of Science Technology of China Hefei China . Department of Physics Yantai Teachers University Yantai China 《中国科学B辑(英文版)》2004,47(2):106-112
Noise is generally considered as a disadvanta-geous factor, which would smear weak signals, there-fore, people always try to reduce its influence. How-ever, recent studies show that, for a nonlinear system, under certain circumstances, noise can enhance sys-tem抯 response to a signal. At specific noise intensity, the response of a system to a weak signal may reach its maximum, which is called 搒tochastic resonance?(SR). The concept of SR was originally put forward by Benzi and his collaborat… 相似文献
995.
996.
J. Piilo E. Lundh K.-A. Suominen 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,40(2):211-222
We have developed Monte Carlo wave function simulation schemes to study
cold collisions between magnesium atoms in a strong red-detuned laser field.
In order to address the strong-field problem, we extend the Monte Carlo wave function framework to include the partial wave
structure of the three-dimensional system. The average heating rate due to radiative collisions is calculated with two different
simulation schemes which are described in detail.
We show that the results of the two methods
agree and give estimates for the radiative collision heating rate for 24Mg atoms in a magneto-optical trap based on the 1S0–1P1 atomic laser cooling transition. 相似文献
997.
In this work we analyze the stochastic dynamics of the Kauffman model evolving under the influence of noise. By considering the average crossing time between two distinct trajectories, we show that different Kauffman models exhibit a similar kind of behavior, even when the structure of their basins of attraction is quite different. This can be considered as a robust property of these models. We present numerical results for the full range of noise level and obtain approximate analytic expressions for the above crossing time as a function of the noise in the limit cases of small and large noise levels. 相似文献
998.
G. Debnath Frank Moss F. Marchesoni Th. Leiber H. Risken 《Journal of statistical physics》1989,54(5-6):1381-1382
A qualitative change in the topology of the joint probability densityP(,x), which occurs for strongly colored noise in multistable systems, has recently been observed first by analog simulation (F. Moss and F. Marchesoni,Phys. Lett. A
131:322 (1988)) and confirmed by matrix continued fraction methods (Th. Leiber and H. Riskin, unpublished), and by analytic theory (P. Hänggi, P. Jung, and F. Marchesoni,J. Stat. Phys., this issue). Systems studied were of the classx=–U(x)/x+(t,), whereU(x) is a multistable potential and (t, ) is a colored, Gaussian noise of intensityD, for which =0, and (t) (s)=(D/)exp(–t–s/). When the noise correlation time is smaller than some critical value 0, which depends onD, the two-dimensional densityP(,x) has the usual topology [P. Jung and H. Risken,Z. Phys. B
61:367 (1985); F. Moss and P. V. E. McClintock,Z. Phys. B
61:381 (1985)]: a pair of local maxima ofP(,x), which correspond to a pair of adjacent local minima ofU(x), are connected by a single saddle point which lies on thex axis. When >0, however,the single saddle disappears and is replaced by a pair of off-axis saddles. A depression, or hole, which is bounded by the saddles and the local maxima thus appears. The most probable trajectory connecting the two potential wells therefore does not pass through the origin for >0, but instead must detour around the local barrier. This observation implies that successful mean-first-passage-time theories of strongly colored noise driven systems must necessarily be two dimensional (Hänggiet al.). We have observed these holes for several potentialsU(x): (1)a soft, bistable potential by analog simulation (Moss and Marchesoni); (2) a periodic potential [Th. Leiber, F. Marchesoni, and H. Risken,Phys. Rev. Lett.
59:1381 (1987)] by matrix continued fractions; (3) the usual hard, bistable potential,U(x)=–ax
2/2+bx
4/4, by analog simulations only; and (4) a random potential for which the forcingf(x)=–U(x)/x is an approximate Gaussian with nonzero correlation length, i.e., colored spatiotemporal noise, by analog simulation. There is a critical curve 0(D) in the versusD plane which divides the two topological behaviors. For a fixed value ofD, this curve is shifted toward larger values of 0 for progressively weaker barriers between the wells. Therefore, strong barriers favor the observation of this topological transformation at smaller values of . Recently, an analytic expression for the critical curve, valid asymptotically in the small-D limit, has been obtained (Hänggiet al.).This paper will appear in a forthcoming issue of theJournal of Statistical Physics. 相似文献
999.
L.I. Salminen M.J. Alava K.J. Niskanen 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,37(3):369-374
A differential cluster variation method (DCVM) is proposed for analysis of spinoidal decomposition in alloys. In this method, lattice symmetry operations in the presence of an infinitesimal composition gradient are utilized to deduce the connection equations for the correlation functions and to reduce the number of independent variables in the cluster variation analysis. Application of the method is made to calculate the gradient energy coefficient in the Cahn-Hilliard free energy function and the fastest growing wavelength for spinodal decomposition in Al-Li alloys. It is shown that the gradient coefficient of congruently ordered Al-Li alloys is much larger than that of the disordered system. In such an alloy system, the calculated fastest growing wavelength is approximately 10 nm, which is an order of magnitude larger than the experimentally observed domain size. This may provide a theoretical explanation why spinodal decomposition after a congruent ordering is dominated by the antiphase boundaries.Received: 17 November 2003, Published online: 2 April 2004PACS:
64.75. + g Solubility, segregation, and mixing; phase separation - 81.30.-t Phase diagrams and microstructures developed by solidification and solid-solid phase transformations - 05.70.Ln Nonequilibrium and irreversible thermodynamics 相似文献
1000.