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991.
Advances in organic synthesis using polymer-supported reagents and scavengers under microwave irradiation 总被引:1,自引:0,他引:1
Bhattacharyya S 《Molecular diversity》2005,9(4):253-257
Summary Microwave-assisted and polymer-supported organic syntheses have emerged independently as versatile tools for rapid generation
of organic molecules. Chemists are increasingly looking for a combination of both techniques for efficient organic synthesis.
This review covers the recent literature on organic synthesis using microwave heating in conjunction with polymer-supported
reagents and scavengers. 相似文献
992.
Toshinobu?YogoEmail author Reimon?Fukuzawa Wataru?Sakamoto Shin-ichi?Hirano 《Journal of nanoparticle research》2005,7(6):633-640
Nanocrystalline BaTiO3 particles modified with polarizable ligands were synthesized through hydrolysis of modified metal–organics below 100°C. BaTiO3 precursor was synthesized from barium metal, titanium isopropoxide and polarizable ligands in a mixture of ethanol and 2-ethoxyethanol.
The modified Ba–Ti complex alkoxide was hydrolyzed yielding BaTiO3 particles modified with organics. The crystallinty of nanometer-sized particles was dependent upon the hydrolysis conditions,
and increased with increasing water amount and time. The nanocrystalline particles were identified to be BaTiO3 by X-ray diffraction (XRD) and electron diffraction. A fluid consisting of modified BaTiO3 particles and silicone oil revealed a typical electrorheological (ER) behavior on applying DC field. The ER behavior was
found to depend upon the kind of ligand. 4-Fluorobenzyloxy modifier revealed the highest yield stress in the ER measurement
among 4-substitued benzyloxy ligands examined. 相似文献
993.
B.?Mosconi P.?RicciEmail author E.?Truhl?k 《The European Physical Journal A - Hadrons and Nuclei》2005,25(2):283-291
The structure of the weak axial pion exchange current is discussed in various models. It is shown how the interplay of the chiral invariance and the double-counting problem restricts uniquely the form of the pion potential term, to the case when the nuclear dynamics is described by the Schrödinger equation with static nucleon-nucleon potential. 相似文献
994.
I.?Giller A.?Ocherashvili T.?Ebertsh?user M.?A.?Moinester S.?SchererEmail author 《The European Physical Journal A - Hadrons and Nuclei》2005,25(2):229-240
We discuss the reaction π-e- → π-e-π0 with the purpose of obtaining information on the γπ → ππ anomalous amplitude
3π. We compare a full calculation at
(p6) in chiral perturbation theory and various phenomenological predictions with the existing data of Amendolia et al. By integrating our theory results using Monte Carlo techniques, we obtain σ = 2.05 nb at
(p6) and σ = 2.17 nb after including the dominant electromagnetic correction. Both results are in good agreement with the experimental cross-section of σ = (2.11±0.47) nb. On the basis of the ChPT results one would extract from the experimental cross-section as amplitudes
3π(0)extr = (9.9±1.1) GeV-3 and
3π(0)extr = (9.6±1.1) GeV-3, respectively, which have to be compared with the low-energy theorem
3π = e/(4π2Fπ3) = 9.72GeV-3. We emphasize the need for new data to allow for a comparison of experimental and theoretical distributions and to obtain
3π with smaller uncertainty. 相似文献
995.
G. F.J.?A?a?osEmail author F.?Baldovin C.?Tsallis 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(3):409-417
We perform a throughout numerical study of the average
sensitivity to initial conditions and entropy production for
two symplectically coupled standard maps focusing on the
control-parameter region close to regularity.
Although the system is ultimately strongly chaotic (positive
Lyapunov exponents), it first stays lengthily in
weak-chaotic regions (zero Lyapunov exponents).
We argue that the nonextensive
generalization of the classical formalism is an adequate
tool in order to get nontrivial information about the first stage of this crossover
phenomenon.
Within this context we analyze the relation
between the power-law sensitivity to initial conditions and the
entropy production. 相似文献
996.
Wangyu?HuEmail author Shifang?Xiao Jianyu?Yang Zhi?Zhang 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(4):547-554
Molecular dynamics calculations have been performed to study the melting
evolution, atomic diffusion and vibrational behavior of bcc metal vanadium
nanoparticles with the number of atoms ranging from 537 to 28475 (diameters
around 2–9 nm). The interactions between atoms are described using an
analytic embedded-atom method. The obtained results reveal that the melting
temperatures of nanoparticles are inversely proportional to the reciprocal
of the nanoparticle size, and are in good agreement with the predictions of
the thermodynamic liquid-drop model. The melting process can be described as
occurring in two stages, firstly the stepwise premelting of the surface
layer with a thickness of 2–3 times the perfect lattice constant, and then
the abrupt overall melting of the whole cluster. The heats of fusion of
nanoparticles are also inversely proportional to the reciprocal of the
nanoparticle size. The diffusion is mainly localized to the surface layer at
low temperatures and increases with the reduction of nanoparticle size, with
the temperature being held constant. The radial mean square vibration
amplitude (RMSVA) is developed to study the anharmonic effect on surface
shells. 相似文献
997.
D. K.?SunkoEmail author S.?Bari?i? 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,46(2):269-279
We study the effect of antiferromagnetic (AF) correlations in the three-band
Emery model, with respect to the experimental situation in weakly underdoped
and optimally doped BSCCO. In the vicinity of the vH singularity of the
conduction band there appears a central peak in the middle of a pseudogap,
which is in an antiadiabatic regime, insensitive to the time scale of the
mechanism responsible for the pseudogap. We find a quantum low-temperature
regime corresponding to experiment, in which the pseudogap is created by
zero-point motion of the magnons, as opposed to the usual semiclassical
derivation, where it is due to a divergence of the magnon occupation number.
Detailed analysis of the spectral functions along the (π,0)–(π,π)
line show significant agreement with experiment, both qualitative and, in the
principal scales, quantitative. The observed slight approaching-then-receding
of both the wide and narrow peaks with respect to the Fermi energy is also
reproduced. We conclude that optimally doped BSCCO has a well-developed
pseudogap of the order of 1000 K. This is only masked by the narrow
antiadiabatic peak, which provides a small energy scale, unrelated to the AF
scale, and primarily controlled by the position of the chemical potential. 相似文献
998.
R.?Avalos-Zu?iga F.?PlunianEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,47(1):127-135
To study the onset of a stationary dynamo in the presence of inner or outer walls of various electromagnetic properties, we propose a simple 1D-model in which the flow is replaced by an alpha effect. The equation of dispersion of the problem is derived analytically. It is solved numerically for
walls of different thicknesses and of electric conductivity and magnetic permeability different from those of the fluid in motion. We also consider walls in the limit of infinite conductivity or permeability. 相似文献
999.
Ch.?Binek P.?Borisov Xi?Chen A.?Hochstrat S.?Sahoo W.?KleemannEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(2):197-201
Perpendicular exchange bias (PEB) involving perpendicular
magnetic anisotropy (PMA) in both the antiferromagnetic (AF) pinning and the
ferromagnetic (FM) sensor layer is expected to become important in future
perpendicular recording and sensing devices. Further, because of the reduced
spin dimensionality, PEB promises to be easier understandable than the
conventional planar exchange bias (EB). In addition to its first realization
using the Ising-type AF compounds FeF2 and FeCl2 we have tested
control strategies of EB being alternative to the conventional magnetic and
thermal ones. Indeed, specific symmetry properties of the pinning layer have
been shown to enable mechanical (viz. piezomagnetic via FeF2) and electric
control (viz. magneto-electric via Cr2O3) of EB, respectively.
Electric control promises to become relevant for TMR devices in MRAM
technology. 相似文献
1000.
J.?DubowikEmail author F.?Stobiecki I.?Go?ciańska Y. P.?Lee A.?Paetzold K.?R?ll 《The European Physical Journal B - Condensed Matter and Complex Systems》2005,45(2):283-288
The temperature dependencies of the ferromagnetic
resonance (FMR) linewidth and the resonance field-shift have been
investigated for NiO/NiFe exchange-biased bilayers from 78 K to 450 K. A broad maximum in the linewidth of 500 Oe, solely due to the
exchange-bias, is observed at ≈150 K when the magnetic
field is applied along the film plane. When the magnetic field is
applied perpendicular to the film plane, the maximum in the
linewidth is less pronounced and amounts to 100 Oe at the same
temperature. Such a behavior of the FMR linewidth is accompanied
with a monotonic increase in the negative resonance field-shift
with decreasing temperature. Our results are compared with the
previous experimental FMR and Brillouin light scattering data for
various ferromagnetic/antiferromagnetic (FM/AF) structures, and
suggest that spin dynamics (spin-wave damping and anomalous
resonance field-shift) in the FM/AF structures can be described in
a consistent way by a single mechanism of the so-called
slow-relaxation. 相似文献