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991.
992.
Maxime Noël Sergey Ananev Mattias Mases Xavier Devaux Juhan Lee Ivan Evdokimov Manuel Dossot Edward McRae Alexander V. Soldatov 《固体物理学:研究快报》2014,8(11):935-938
We report on a first study of single walled carbon nanotubes (SWCNTs) after application of dynamic (shock) compression. The experiments were conducted at 19 GPa and 36 GPa in a recovery assembly. For comparison, an experiment at a static pressure of 36 GPa was performed on the material from the same batch in a diamond anvil cell (DAC). After the high pressure treatment the samples were characterized by Raman spectroscopy and transmission electron microscopy (TEM). After exposure to 19 GPa of shock compression the CNT material exhibited substantial structural damage such as CNT wall disruption, opening of the tube along its axis (“unzipping”) and tube shortening (“cutting”). Dynamic compression to 36 GPa resulted in essentially complete CNT destruction whereas at least a fraction of the nanotubes was recovered after 36 GPa of static compression though severely damaged. The results of these shock wave experiments underline the prospect of using SWCNTs as reinforcing units in material WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim) 相似文献
993.
Hasan M. El Ghanem Saa’Di Abdul Jawad Yazan A. Hussain Adnan S. Abu-Surrah 《Journal of Macromolecular Science: Physics》2014,53(5):878-892
Impedance spectroscopy was utilized to investigate the dielectric properties, ac conductivity and charge transport mechanisms in propylene-alt-CO/ethylene-alt-CO (EPEC) random terpolymer filled with multi-walled carbon nanotubes (MWCNT) as a function of nanofiller content, frequency, and temperature. Equivalent resistor-capacitor (RC) circuit models were proposed to describe the impedance characteristics of the unfilled terpolymer and the nanocomposite at different temperatures. For the nanocomposites, the ac conductivity tended to be frequency independent at low frequencies. At high frequencies, the ac conductivity increased with frequency. The dc conductivity (i.e., plateau of the ac conductivity at low frequencies) at room temperature increased from 10?9 (Ω·m)?1 for the unfilled polymer to l0?3 (Ω·m)?1 for the 6 wt% MWCNT/EPEC nanocomposite. At low temperatures, the equivalent RC model for EPEC-0 and EPEC-2 was found to consist of a parallel RC circuit. However, for 6 wt% MWCNT/EPEC nanocomposite, an RC model consisting of an R/constant phase element (CPE) circuit and a resistor in series was required to describe the impedance behavior of the nanocomposite. 相似文献
994.
基于TiO_2光阳极、Pt对电极的染料敏化太阳能电池(DSSC)因其优异的光电转换特性受到了广泛的关注,然而Pt昂贵的价格制约了其发展与应用.针对这一问题,本文设计、制备了一种由相对致密且高导电的石墨膜(PC层,底层)及多孔碳纳米颗粒膜(CC层,顶层)构成的低成本、高性能三维多孔复合碳层对电极.基于该CC/PC对电极的DSSC具有优异的光伏性能:在1.5标准太阳光照射下,其填充因子高达65.28%(较Pt对电极高4.1%)、光电转换效率高达5.9%(为Pt对电极的94.2%). CC/PC对电极的优异光伏性能主要归因于其独特的三维多孔导电结构,该结构有极高的比表面积和丰富的催化反应活性位,有利于电子的快速传输及离子的快速转移,在这些因素的协同作用下,其光电转换性能大大改善. 相似文献
995.
Konstantin Iakoubovskii 《Central European Journal of Physics》2009,7(4):645-653
This paper reviews major techniques of aligning carbon nanotubes, either during the growth or by the post-growth processing.
A number of post-processing alignment techniques are discussed, which employ mechanical stretching, fracture, compression,
friction, filtration, fiber drawing, gas flow, liquid crystals, Langmuir-Blodgett technique, acoustic, magnetic and electric
fields. The suitability of those techniques to industrial applications is analyzed.
相似文献
996.
We combined scanning tunneling microscopy and density functional theory to establish the structure-functionality relationship for nanometer-sized defects on TiO2(1 1 0). Three-angstrom high topographically distinct dots are ascribed to stoichiometric TiO2 nanoclusters with low coordination numbers. The under-coordinated O atoms of the nanocluster, with surface O atoms, provide exceptionally strong binding sites for Au nanoparticles. Our atomistic model elucidates a number of characteristics salient to low temperature CO oxidation by Au nanoparticles. 相似文献
997.
Ganesh P. Sanganwar Ram B. Gupta Alexandre Ermoline James V. Scicolone Rajesh N. Dave 《Journal of nanoparticle research》2009,11(2):405-419
Due to the increased use of nanocomposites, mixing at nanoscale has become important. Current mixing techniques can be classified
into: (a) dry mixing (mechanical mixing), (b) wet mixing, and (c) simultaneous production of mixed nanoparticles (when possible).
Dry mixing is in general not effective in achieving desired mixing at nanoscale, whereas wet mixing suffers from different
disadvantages like nanomaterial of interest should be insoluble, has to wet the liquid, and involves additional steps of filtration
and drying. This paper examines the use of pressurized carbon dioxide having high density and low viscosity to replace the
liquids (e.g., n-hexane, toluene). Ultrasound is applied to the suspension of nanopowders in gaseous and supercritical carbon dioxide where
high impact collisions during sonication help mixing and the final mixture is obtained by simple depressurization. The method
is tested for binary mixture of alumina/silica, silica/titania, MWNT (multiwalled carbon nanotubes)/silica, and MWNT/titania.
The effects of sonication intensity and pressure on the degree of mixing are studied. Comparative study is also done with
liquid n-hexane as a mixing media. Quantitative characterization (e.g., mean composition standard deviation, intensity of segregation)
of mixing of alumina/silica and silica/titania is done with energy-dispersive X-ray spectroscopy, and that of MWNT/silica
and MWNT/titania is done using field-emission scanning electron microscopy and day-light illumination spectrophotometry. Results
show that mixing in carbon dioxide at higher ultrasound amplitudes is as good as in liquid n-hexane, and the final mixed product does not contain any residual media as in the case of liquid n-hexane. 相似文献
998.
Utilizing the unique features of the scanning atom probe (SAP) the binding states of the biomolecules, leucine and methionine, are investigated at atomic level. The molecules are mass analyzed by detecting a single atom and/or clustering atoms field evaporated from a specimen surface. Since the field evaporation is a static process, the evaporated clustering atoms are closely related with the binding between atoms forming the molecules. For example, many thiophene radicals are detected when polythiophene is mass analyzed by the SAP. In the present study the specimens are prepared by immersing a micro cotton ball of single walled carbon nanotubes (SWCNT) in the leucine or methionine solution. The mass spectra obtained by analyzing the cotton balls exhibit singly and doubly ionized carbon ions of SWCNT and the characteristic fragments of the molecules, CH3, CHCH3, C4H7, CHNH2 and COOH for leucine and CH3, SCH3, C2H4, C4H7, CHNH2 and COOH for methionine. 相似文献
999.
1000.
The kinetics of reaction between benzyl chloride and phenol (or substituted phenols) in the presence of sodium hydroxide have
been investigated. A differential application of the effect of substituents on the reaction rate to distinguish between a
rate-limiting oxygen or carbon attack has been attempted. Considerable scatter in the Hammett plot for the latter attack points
to an essentially O-alkylation. The rate constants correlate well with pKa values of the different phenols. The influence of salt and solvent on the reaction rate suggests this reaction to be an ion-dipole
one. 相似文献