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991.
For efficient progress, model properties and measurement needs can adapt to oceanic events and interactions as they occur. The combination of models and data via data assimilation can also be adaptive. These adaptive concepts are discussed and exemplified within the context of comprehensive real-time ocean observing and prediction systems. Novel adaptive modeling approaches based on simplified maximum likelihood principles are developed and applied to physical and physical–biogeochemical dynamics. In the regional examples shown, they allow the joint calibration of parameter values and model structures. Adaptable components of the Error Subspace Statistical Estimation (ESSE) system are reviewed and illustrated. Results indicate that error estimates, ensemble sizes, error subspace ranks, covariance tapering parameters and stochastic error models can be calibrated by such quantitative adaptation. New adaptive sampling approaches and schemes are outlined. Illustrations suggest that these adaptive schemes can be used in real time with the potential for most efficient sampling. 相似文献
992.
G. A. Miller 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):578-584
The discovery more than twenty years ago, by the EMC Collaboration, that the deep-inelastic-scattering DIS structure functions
are influenced by the nuclear environment stunned the nuclear physics community and brought quarks and gluons into the field
with great impact. A great length of time has passed, but despite a semi-infinite number of papers on the subject, there is
no explanation that is universally accepted. Many models (related in one way or another to QCD) have been successful in reproducing
data for deep inelastic scattering on nuclear targets, but fewer have described both the DIS and nuclear Drell-Yan experiments.
Although there are some positive indications, no model has been used to predict correctly and unambiguously new independent
phenomena. We review the history and discuss the best experimental prospects for future discovery. 相似文献
993.
E. Scalas U. Garibaldi S. Donadio 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):271-272
This erratum corrects a mistake in reference [E. Scalas, U. Garibaldi, S. Donadio, Eur. Phys. J. B 53, 267 (2006)].
In that paper,
we needed an aperiodic version of the BDY game, but, in formula (1),
we incorrectly presented
a periodic transition matrix of period 2 in the special case of g = 2 agents.
Here, we present the right aperiodic version. 相似文献
994.
K. Jin Z. C. Wang Q. Zhang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(2):325-332
We study the absorption spectra of a degenerate V-type
atom, where a resonant driving field and a probe field drive
different branches of transitions and a dc field is applied to
drive the transition between two excited states. The effects of
vacuum induced coherence (VIC) on the absorption spectra are
investigated. It is demonstrated that in some special cases the
VIC can lead to the depression of absorption and narrow resonance.
The origin of these features are discussed. When the pump field
and the dc field have the same intensity, it is interesting to
find that the whole absorption spectrum comes mainly from the
absorptions induced by the interferences among different
transitions between dressed states. 相似文献
995.
H. Keskinen J. M. Mäkelä M. Aromaa J. Ristimäki T. Kanerva E. Levänen T. Mäntylä J. Keskinen 《Journal of nanoparticle research》2007,9(4):569-588
In this study, liquid flame spray (LFS) was used to produce titania, silver and silver–titania deposits of nanoparticles.
Titanium(IV)ethoxide (TEOT) and silver nitrate in ethanol solutions were used as precursors and sprayed into turbulent hydrogen–oxygen
flame. Production rates of 1.5–40 mg/min of titania were used with silver additions of 1, 2, 4, and 8 wt% compared to titania.
Nanoparticle deposits were collected by thermophoretic sampling at six different axial distances from the flame torch head:
3, 5, 10, 12, 15, and 20 cm, of which the all but the last one occurred inside the flame. The deposit samples were analysed
by TEM and SAED analysis. The powder samples of the particles were also collected by electric precipitator to XPS and specific
surface area analysis. Particle size and effective density after the flame in the aerosol were analysed with SMPS and ELPI.
The results from the previous studies i.e. controlling the particle size by setting the production rates of the particles
were seen to apply also for this binary system. Characterisation of the deposits showed that when the substrate is inserted
into the flame, in the beginning of the flame the deposit is formed by gas phase deposition whereas further down the flame
the particles are first formed in the gas phase and then deposited. The location of the transition from gas phase deposition
to gas phase nucleation prior to deposition depends on chemical/physical properties (e.g. thermodynamics and gas phase interactions)
of the precursor, precursor concentration in the flame and also flame temperature profile. Therefore, the deposit collection
distance from the burner also affected the collected particle size and degree of agglomeration. The two component deposits
were produced in two different ways: one-step method mixing both precursors in the same solute, and two-step method spraying
each precursor separately. The particle morphology differs between these two cases. In one-step method the primary (d
TEM) and agglomerate particle size (d
SMPS) decreased with the amount of silver addition, verifying the fact that when present, the silver has a clear effect on the
titania nanoparticle formation and growth. 相似文献
996.
D. Khalil A. Makhoute A. Maquet G. Rahali M. Zitane 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):287-295
The dynamics of laser-assisted elastic collisions in
helium is studied using the second-order Born approximation.
Detailed calculations of the scattering amplitudes are performed
by using the Sturmian basis expansion. Differential cross sections
for elastic scattering with the net absorption/emission of up to
two photons are calculated for collision energies of 5 eV, 10 eV,
and 20 eV. We discuss the influence of the low-energy electrons on
the differential cross section (DCS) as a function of the
scattering angle for selected choices of the laser frequency and
the number of photons exchanged between the external field and
electron-helium system. 相似文献
997.
Recently, Bauke and Mertens conjectured that the local statistics of energies in random spin systems with discrete spin space
should in most circumstances be the same as in the random energy model. We review some rigorous results confirming the validity
of this conjecture. In the context of the SK models, we analyse the limits of the validity of the conjecture for energy levels
growing with the volume of the system. In the case of the Generalised Random energy model, we give a complete analysis for
the behaviour of the local energy statistics at all energy scales. In particular, we show that, in this case, the REM conjecture
holds exactly up to energies E
N
< β
c
N, where β
c
is the critical temperature. We also explain the more complex behaviour that sets in at higher energies.
Research supported in part by the DFG in the Dutch-German Bilateral Research Group “Mathematics of Random Spatial Models from
Physics and Biology” and by the European Science Foundation in the Programme RDSES. 相似文献
998.
The Geant4 CHIPS model simulates both decay and nuclear capture of negative muons. In hadron level models the muon is captured
by a proton, p(μ,νμ)n , and the neutron transfers to the nucleus only 5MeV, which is not enough to split a nucleon from the nucleus, while the
measured spectra of emitted nucleons reach 80MeV. In CHIPS, which considers asymptotically free quark-partons, the muon can
be captured by a quark, u(μ,νμ)d , and transfers 52MeV to the nucleus. This capture mechanism fits the main part of the nucleon spectra, while the high-energy
part of the spectra is not fitted. A precise fit of the high-energy part of the nucleon spectra can be made if the muon decay
μ → dˉνμ is taken into account. 相似文献
999.
B. Dybiec L. Schimansky-Geier 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):313-320
We study the stationary probability density of a Brownian particle in a potential with a single-well subject to the purely
additive thermal and dichotomous noise sources. We find situations where bimodality of stationary densities emerges due to
presence of dichotomous noise. The solutions are constructed using stochastic dynamics (Langevin equation) or by discretization
of the corresponding Fokker-Planck equations. We find that in models with both noises being additive the potential has to
grow faster than |x| in order to obtain bimodality. For potentials ∝|x| stationary solutions are always of the double exponential
form. 相似文献
1000.
Non-Fellerian particle systems are characterized by nonlocal interactions, somewhat analogous to non-Gibbsian distributions.
They exhibit new phenomena that are unseen in standard interacting particle systems. We consider freezing transitions in one-dimensional
non-Fellerian processes which are built from the abelian sandpile additions to which in one case, spin flips are added, and
in another case, so called anti-sandpile subtractions. In the first case and as a function of the sandpile addition rate,
there is a sharp transition from a non-trivial invariant measure to the trivial invariant measure of the sandpile process.
For the combination sandpile plus anti-sandpile, there is a sharp transition from one frozen state to the other anti-state. 相似文献