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31.
Interpreting the conductive atomic force microscopy measured inhomogeneous nanoscale surface electrical properties of Al‐doped ZnO films 下载免费PDF全文
In this work, conductive atomic force microscopy is used to study the inhomogeneous surface electrical conductivity of Al‐doped ZnO thin films at a nanoscale dimension. To this end, Al‐doped ZnO films were deposited onto the soda lime glass substrates at substrate temperature (Ts) varying from 303 to 673 K in radio frequency magnetron sputtering. The obtained local surface electrical conductivity values are found to be influenced by their bulk electrical resistivity, surface topography and tip geometry. Further, the average (local) surface conductivity from the film surface is found to increase with increasing Ts from 303 to 623 K, beyond which they decrease until 673 K. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
32.
Ph. Barbeau J. F. Gerard B. Magny J. P. Pascault G. Vigier 《Journal of Polymer Science.Polymer Physics》1999,37(9):919-937
In this paper, we investigate the final morphology of photocured polyurethane acrylates based on polypropylene oxide by means of Transmission Electron Microscopy (TEM), Small Angle X‐ray Scattering (SAXS), and dynamic mechanical measurements. Two interrelated structural features on two different size scales can occur in these systems. TEM analysis demonstrates the presence of inhomogeneities on the length scale of 10–200 manometers, mostly constituted by clusters of small hard units (diacrylated diisocyanate) connected by polyacrylate chains. The bimodal shape of the dynamic mechanical relaxation spectra corroborates this two‐phase structure. Besides, a suborganization of the reacted diisocyanate hard segments inside the polyurethane acrylate matrix is revealed by SAXS measurements, depending on the nature of the hydroxylacrylate used for the synthesis of the precursor. Finally, UV‐exposure time is found to induce modifications on the viscoelastic properties of the final network, even at high double‐bond conversion: this effect can be due to a postreaction and to an increase of the crosslinking density inside the hard segments domains. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 919–937, 1999 相似文献
33.
Kai Zhang Chun-guang Ban Ye Yuan Li Huang Yang Gan 《Surface and interface analysis : SIA》2022,54(8):837-846
Characterization of the geometrical and structural characteristics of oxidized Cu area in high resolution is crucial for tracking the change in morphology, exploring interactions between graphene layers and Cu substrates and revealing the mechanism for the orientation-dependent oxidation of Cu. Here, we reported experimental results on nanoscale imaging of natural oxidation of the polycrystalline Cu substrate coated by partial-coverage chemical vapor deposition (CVD)-grown graphene stored in dryer under ambient conditions for up to 10 months. Scanning electron microscope (SEM), together with atomic force microscope (AFM), Raman, and X-ray photoelectron spectroscopy (XPS), was used for systematically studying the morphological and compositional changes at nanoscale during oxidation. The appearance of oxidized Cu substrates could be unambiguously distinguished from the unoxidized regions based on their distinctly different morphologies in SEM images, and the underlying mechanism was discussed in detail. By analyzing a millimeter-seized polycrystalline Cu substrate, we found that the oxidation of polycrystalline Cu substrate depends sensitively on both orientation of graphene layers and Cu substrates. Furthermore, the time-dependent oxidation evolution of Cu substrate was also established, and the oxidation rate was readily determined. The findings reported here will have important implications for developing protection coatings for Cu. 相似文献
34.
Nimmy R. Mammoottil James F. Reuther Dumindika A. Siriwardane Oleg V. Kulikov Bruce M. Novak 《Journal of polymer science. Part A, Polymer chemistry》2017,55(18):2915-2934
Described herein is a comprehensive survey on the most recent advancements in polycarbodiimide synthetic methodologies, structure determination, property design, and self-assembly. In particular, the 15N-isotopic enrichment of polycarbodiimides is detailed along with the use of 15N NMR to identify the regioregularity and mechanism of chiroptical switching in polycarbodiimides. Furthermore, the new Ni(II) mediated “living” polymerization is explained along with its utilization in the incorporation of polycarbodiimides into block copolymers, graft copolymers, and star polymers. Finally, we review the recent discoveries focusing on the highly tunable self-assembly behaviors of polycarbodiimide homopolymers and copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2915–2934 相似文献
35.
天然有机质(NOM)对纳米铁基材料去除污染物过程中的影响作用机理仍存争议.本工作选取腐殖酸(HA)作为NOM的代表物,研究了HA对生物炭负载纳米镍铁(BC@Ni/Fe)降解十溴联苯醚(BDE209)的动力学影响,结果表明HA对BC@Ni/Fe降解BDE209产生抑制作用,且随着HA浓度的升高,抑制作用越显著.通过HA与BC@Ni/Fe相互作用实验发现,HA能够快速地被BC@Ni/Fe吸附;通过HA对BC@Ni/Fe的Zeta电位和沉降影响实验发现,随着HA浓度的升高可有效提高BC@Ni/Fe的稳定性以及表面电荷,这表明HA不是通过影响BC@Ni/Fe颗粒的性能对BC@Ni/Fe去除BDE209产生抑制作用的.BC@Ni/Fe的腐蚀能力随着HA浓度的升高而降低,这与HA对BC@Ni/Fe去除BDE209反应活性影响成正相关关系.HA中具有电子传递作用的典型醌类化合物2-羟基-1,4-萘醌(Lawsone)和蒽醌-2,6-磺酸钠(AQDS),在反应过程中并没有起到电子传递作用促进反应进行,反而对BC@Ni/Fe去除BDE209起抑制作用.结合BDE209和HA之间的竞争吸附实验发现,HA抑制BC@Ni/Fe反应活性的主导原因是HA优先于BDE209被BC@Ni/Fe吸附,HA包覆于BC@Ni/Fe颗粒表面占据了活性位点,阻碍BC@Ni/Fe与H2O的接触,减少了Fe0的腐蚀,从而抑制了BC@Ni/Fe对BDE209的降解. 相似文献
36.
大量研究表明,纳米零价铁(nanoscale Zero-Valent Iron,nZVI)对水中重金属,尤其是金、银等稀贵金属,有良好的分离富集作用.利用纳米零价铁反应器证明了nZVI可从废水中分离低浓度的银离子(Ag+),并生成高含量的“银矿石”.此外,也证明了反应区氧化还原电位能够反映nZVI与Ag+的反应速率和分离效率.利用X射线衍射仪、X射线光电子能谱和高分辨透射电子显微镜等手段对反应产物进行表征,证实了Ag+可被nZVI还原为单质银,并以纳米颗粒的形式(<10 nm)沉积在nZVI表面.与其他材料(常见吸附/还原材料)相比,nZVI具有效率高,受pH影响小的优点.研究结果表明,nZVI是一种能够高效富集痕量银资源并产生高价值纳米银的材料. 相似文献
37.
G. B. Parravicini A. Stella M. C. Ungureanu P. G. Merli A. Migliori P. Cheyssac R. Kofman 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):219-222
Both theoretical and experimental works give evidence that
gallium exhibits solid phases labelled , , , besides the
stable phase strongly dependent both on the size and the
confinement conditions. An experimental technique was used based
on capacitance and conductance measurements
vs. temperature in the
audiofrequency range. This technique is particularly sensitive
to the conditions of the investigated particle surface that
plays a fundamental role in the melting and more generally in
the phase transition processes. In particular the strict
relation between the derivative of the capacitance with respect
to the temperature, dC/dT, and the entropy of the system is
considered. In gallium nanoparticles 20 nm in radius, only the
phase is shown to occur. Further the transition to liquid phase
was detected. The melting process was found to start about 65 K
below the full melting temperature value. In the case of
particles 10 nm in radius, where different metastable phases may
occur, the capacitance vs.
temperature curve was found to display abrupt changes of the
slope. The singularities are associated to a well defined
transition temperature. 相似文献
38.
P. Billaud J.-R. Huntzinger E. Cottancin J. Lermé M. Pellarin L. Arnaud M. Broyer N. Del Fatti F. Vallée 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):271-274
The extinction spectrum of single silver nanoparticles
with size ranging from 20 to 80 nm is investigated with the spatial
modulation spectroscopy technique using either a tunable laser or a white
lamp as the broadband source. Results are in good agreement with the
prediction of the Mie theory, permitting to extract the nanoparticle size
from the measured absolute value of the optical extinction cross-section. In
contrast, the deduced refractive index of the nanoparticle environment and
the reduction of the electron mean free path show a large dependence on the
precise value of the bulk silver dielectric function. 相似文献
39.
C. Benjamin T. Jonckheere A. Zazunov T. Martin 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(3):279-289
We consider a model for a single molecule with a large frozen spin
sandwiched in between two BCS superconductors at equilibrium, and
show that this system has a π junction behavior at low
temperature. The π shift can be reversed by varying the other
parameters of the system, e.g., temperature or the position of the
quantum dot level, implying a controllable π junction with
novel application as a Josephson current switch. We show that the mechanism
leading to the π shift can be explained simply in terms of the contributions
of the Andreev bound states and of the continuum of states above the superconducting gap.
The free energy for certain configuration of parameters shows a
bistable nature, which is a necessary pre-condition for
achievement of a qubit. 相似文献
40.
H. Jensen J. Kröger N. Néel R. Berndt 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):465-469
Clusters on surfaces have been investigated with low-temperature scanning tunnelling microscopy and spectroscopy. Constant
current spectra acquired on Ag oligomers and one-dimensional chains on a Ag(111) reveal a
single resonance peak whose energy shifts towards the Fermi level with increasing cluster size. Next, controlled and reproducible
contact between a STM tip and a C60 molecule adsorbed on Cu(100) is reported. The
transition from tunnelling to contact is discussed in terms of local heating of the tip-molecule junction. 相似文献