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991.
Temperature-modulated DSC (TMDSC) measurements at reasonably high frequencies allow for the determination of base-line heat
capacity. In this particular case vitrification and devitrification of the rigid amorphous fraction (RAF) can be directly
observed. 0.01 Hz seems to be a reasonably high frequency for bisphenol-A polycarbonate (PC). The RAF of PC is established
during isothermal crystallization. Devitrification of the RAF seems to be related to the lowest endotherm. For PC the melting
of small crystals between the lamellae is expected to yield the lowest endotherm.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
992.
Karger-Kocsis J. Moskala E. J. Shang P. P. 《Journal of Thermal Analysis and Calorimetry》2001,63(3):671-678
The toughness of amorphous copolyester sheets was assessed by the essential work of fracture (EWF) concept. While the yielding-related
work of fracture terms did not change significantly, the necking-related parameters strongly decreased with decreasing entanglement
density of the copolyesters having different amounts of cyclohexylenedimethylene (CHDM) units in their backbones. Furthermore, copolyesters with high CHDM content and thus less entanglement density showed full recovery of the necked region beyond the glass transition temperature,
i.e. the ‘plastic’ zone in the related specimens formed by cold drawing and not by true plastic deformation. By contrast,
the copolyester with negligible amount of CHDM did not show this shape recovery. Modulated differential scanning calorimetry (MDSC) revealed that the necking in the latter
system was accompanied by strain-induced crystallization. The superior work hardening in the necking stage of the respective
poly(ethylene terephthalate) (PET) specimens can thus be ascribed to stretching of the entanglement network with superimposed crystallization.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
993.
先后选用1至3片非晶Fe46.3Co0.03Ni46.5Si3.75V0.92B2.5合金薄带作样品,插入13层密绕直螺线管内,分别在高静水压容器内和其他四种不同环境中测量它们的磁化曲线、磁导率曲线和起始磁化曲线,再次研究了初级线圈采用多层直螺线管对铁镍合金样品的误差。(1)实验结果表明:既存在样品材料被磁化而形成的退磁场H',也存在漏磁通引起周围铁器磁化而形成的退磁场H'。(2)为了缩小H'的影响,只用1片非晶合金薄带作样品时,H'的影响变得严重,导致μm和μi出现惊人的误差:Δμm/μm=50%,Δμi/μi=104%。(3)为了综合兼顾这两种影响,采用3片非晶合金薄带作样品时,虽然H'的影响增大一点,但是H'的影响被更多地削弱,所以环境磁化引起的误差反而减小:Δμm/μm=29%,Δμi/μi=15.5%。 相似文献
994.
M. Laridjani A.J. Epstein 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(4):585-597
Polyanilines belong to a family of electronic polymers. Due to a wide range of variable parameters in the synthesis of polyanalines,
a variety of samples with different physical properties can be achieved. Different investigators have identified the degree
of crystallinity for different varieties of polyanilines. They have classified them into two classes of emeraldine forms.
In these structural investigations, the traditional “concept of the two phase system” was used for differentiating the crystalline
phase. Recently, it has been shown that washing the emeraldine base (EB) by NMP or THF will establish two different X-ray
patterns. The X-ray pattern of the sample washed with THF shows a limited number of Bragg lines superimposed on the broad
diffuse halos. Other patterns only indicated broad diffuse halos. These experimental facts do not advocate the “two phase
system model”, especially with scarce Bragg reflections. We have set-up an elegant prototype for X-ray diffractometry which
allows us to obtain a high resolution X-ray pattern from polymers with coherent intrinsic backgrounds. Formally, this coherent background was excluded for polymer structural identification. Nevertheless, we have introduced a new method of separating
the reflected lines from a coherent background. The interference functions F(K) of the coherent background were obtained applying this novel technique. The advantage of our method of separation is verified
by comparing the background of F(K) with the F(K) of the sample washed with NMP. Fourier inversion is used to identify the short range order of the atoms responsible for
the diffuse scattering. This result enabled us to choose a standard state of disorder in polymers. This standard state of
randomness can be considered as the edge of disorder. By defining this reference state of randomness, it can be seen that the atomic arrangements of long and fast changing structural
chains correspond best to the random array model rather than the two phase system model. The novel experiment and analysis
technique presented here offer a possibility of application of structural studies to many common polymers, all of which have
the characteristic of the diffuse halo underlying the diffraction lines.
Received: 7 May 1997 / Revised: 2 July 1998 / Accepted: 25 September 1998 相似文献
995.
M. Leadbeater R.A. Römer M. Schreiber 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(4):643-652
We present calculations of the localisation length, , for two interacting particles (TIP) in a one-dimensional random potential, presenting its dependence on disorder, interaction
strength U and system size. is computed by a decimation method from the decay of the Green function along the diagonal of finite samples. Infinite sample
size estimates are obtained by finite-size scaling. For U=0 we reproduce approximately the well-known dependence of the one-particle localisation length on disorder while for finite
U, we find that with varying between and . We test the validity of various other proposed fit functions and also study the problem of TIP in two different random potentials
corresponding to interacting electron-hole pairs. As a check of our method and data, we also reproduce well-known results
for the two-dimensional Anderson model without interaction.
Received 19 June 1998 and Received in final form 29 October 1998 相似文献
996.
Y. Galerne P. Hubert 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,8(2):245-249
The active oxygen gas arising from a plasma reactor is used to realize progressive chemical modifications onto silane coatings
that could be particularly interesting as alignment layers for liquid crystal display applications. Depending on the oxygen
density grafted onto the substrate, these alignment layers provide different zenithal anchoring angles, or pretilt angles,
with anchoring transitions, for polar and non-polar nematic liquid crystals as 5CB and MBBA, respectively. The anchoring transitions
are found to be smoother with the polar nematics. Such a behavior is discussed in terms of the differential wetting model
by adding a cosine term to the interaction energy between the nematic and the substrate. A local justification is proposed
for this symmetry breaking term.
Received: 18 May 1998 相似文献
997.
C. Lautz T.M. Fischer 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,7(2):263-269
Brewster angle microscopy (BAM) measurements of the low temperature region of the phase diagram of eicosanoic acid monolayers
at an acidic subphase are performed. The existence of a new chiral I phase intervening between the L2 and L
2
' phase recently discovered by Durbin et al. [M.K. Durbin, A. Malik, A.G. Richter, R. Ghastkadvi, T. Gog, P. Dutta, J. Chem. Phys. 106, 8216 (1997)] using grazing incidence X-ray diffraction (GIXD) is confirmed. Chiral symmetry breaking within the monolayers
creates characteristic boundaries separating domains of opposite handedness. These disclination lines are associated with
a jump in the tilt azimuth of the director, while the underlying hexatic orientation is continuous across the boundary. The
disclination lines are observed with the Brewster angle microscope and analyzed as a function of surface pressure. The jump
in tilt azimuth is determined. Agreement with an extended Landau theory proposed by Durbin is achieved.
Received: 26 January 1998 / Revised: 3 August 1998 / Accepted: 7 August 1998 相似文献
998.
999.
K.M. Frahm 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(2):371-378
The localization length L2 of two interacting particles in a one-dimensional disordered system is studied for very large system sizes by an efficient
and accurate variant of the Green function method. The numerical results (at the band center) can be well described by the
functional form L
2
=L
1
[0.5+c(U) L
1
] where L1 is the one-particle localization length and the coefficient depends on the strength U of the on-site Hubbard interaction. The Breit-Wigner width or equivalently the (inverse) life time of non-interacting pair
states is analytically calculated for small disorder and taking into account the energy dependence of the one-particle localization
length. This provides a consistent theoretical explanation of the numerically found U-dependence of c(U).
Received 16 September 1998 相似文献
1000.
A.W.C. Lau P. Pincus 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(1):175-180
We consider the electrostatic interaction between two rigid membranes, with different surface charge densities of opposite
sign, across an aqueous solution without added salt. Exact solutions to the nonlinear Poisson-Boltzmann equation are obtained
and their physical meaning discussed. We also calculate the electrostatic contribution to the free energy and discuss the
renormalization of the area per head group of the charged lipids arising from the Coulomb interaction.
Received 13 October 1998 相似文献