全文获取类型
收费全文 | 847篇 |
免费 | 160篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 19篇 |
综合类 | 35篇 |
化学工业 | 279篇 |
金属工艺 | 127篇 |
机械仪表 | 23篇 |
建筑科学 | 1篇 |
矿业工程 | 5篇 |
能源动力 | 74篇 |
轻工业 | 16篇 |
石油天然气 | 3篇 |
武器工业 | 4篇 |
无线电 | 129篇 |
一般工业技术 | 308篇 |
冶金工业 | 25篇 |
原子能技术 | 4篇 |
自动化技术 | 18篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 38篇 |
2021年 | 61篇 |
2020年 | 49篇 |
2019年 | 68篇 |
2018年 | 56篇 |
2017年 | 59篇 |
2016年 | 48篇 |
2015年 | 44篇 |
2014年 | 65篇 |
2013年 | 64篇 |
2012年 | 63篇 |
2011年 | 64篇 |
2010年 | 39篇 |
2009年 | 66篇 |
2008年 | 54篇 |
2007年 | 40篇 |
2006年 | 40篇 |
2005年 | 27篇 |
2004年 | 24篇 |
2003年 | 24篇 |
2002年 | 19篇 |
2001年 | 10篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1991年 | 1篇 |
排序方式: 共有1070条查询结果,搜索用时 46 毫秒
81.
The Y2O3 : EU^3 + hollow spheres were synthesized using the template-mediated method. XRD patterns indicated that the broadened diffraction peaks resulted from nanocrystals in Y2O3 : EU^3 + shells of hollow spheres. XPS spectra showed that the Y2O3 : EU^3 + shells were linked with silica cores by a Si-O-Y chemical bond. SEM and TEM observations showed that the size of the SiO2/Y2O3 : EU^3 + core-shell particle was about 100 nm, and the thickness of the Y2O3 : EU^3 + hollow sphere was less than 5 nm. The photoluminescence spectra of the SIO2/Y2O3 : EU^3 + core-shell materials and Y2O3 : EU^3 + hollow spheres had red luminescent properties, and the broadened emission peaks came from nanocrystals composed of the Y2O3 : EU^3 + shell. 相似文献
82.
J. Zhong G. Saraf H. Chen Y. Lu Hock M. Ng T. Siegrist A. Parekh D. Lee E. A. Armour 《Journal of Electronic Materials》2007,36(6):654-658
ZnO nanotips are grown on epitaxial GaN/c-sapphire templates by metalorganic chemical vapor deposition. X-ray diffraction
(XRD) studies indicate that the epitaxial relationship between ZnO nanotips and the GaN layer is (0002)ZnO||(0002)GaN and
(101̄0)ZnO||(101̄0)GaN. Temperature-dependent photoluminescence (PL) spectra have been measured. Sharp free exciton and donor-bound
exciton peaks are observed at 4.4 K with photon energies of 3.380 eV, 3.369 eV, and 3.364 eV, confirming high optical quality
of ZnO nanotips. Free exciton emission dominates at temperatures above 50 K. The thermal dissociation of these bound excitons
forms free excitons and neutral donors. The thermal activation energies of the bound excitons at 3.369 eV and 3.364 eV are
11 meV and 16 meV, respectively. Temperature-dependent free A exciton peak emission is fitted to the Varshni’s equation to
study the variation of energy bandgap versus temperature. 相似文献
83.
Nanostructural ZnO is a good candidate for field emission (FE) because of its high aspect ratio, controllable electrical conductivity,
and good thermal and chemical stability. In order to improve the FE performance, ZnO nanopins, gallium-doped nanofibers, periodic
nanorod arrays, and aligned nanotubes were designed and fabricated by a vapor-phase transport method using ZnO + C and ZnO + C + Ga2O3 powder mixtures, electrochemical deposition, and hydrothermal decomposition, respectively. The FE behaviors including threshold
of electric field, emission current density, field enhancement factor, and stability are reviewed in this paper based on our
previous works. Some strategies to improve the performance of the nanostructural ZnO field emitters are demonstrated. 相似文献
84.
In this article, we report a facile precursor pyrolysis method to prepare porous spinel-type cobalt manganese oxides (Co x Mn3-x O4) with controllable morphologies and crystalline structures. The capping agent in the reaction was found to be crucial on the formation of the porous spinel cobalt manganese oxides from cubic Co2MnO4 nanorods to tetragonal Co2Mn4 microspheres and tetragonal Co2Mn4 cubes, respectively. All of the prepared spinel materials exhibit brilliant oxygen reduction reaction (ORR) electrocatalysis along with high stability. In particular, the cubic Co2MnO4 nanorods show the best performance with an onset potential of 0.9 V and a half-wave potential of 0.72 V which are very close to the commercial Pt/C. Meanwhile, the cubic Co2MnO4 nanorods present superior stability with negligible degradation of their electrocatalytic activity after a continuous operation time of 10,000 seconds, which is much better than the commercial Pt/C electrocatalyst. 相似文献
85.
The reoxidability of vanadyl pyrophosphate is studied by thermal analysis and by temporal analysis of product (TAP). The samples
differ by surface area, oxidation state of vanadium, crystallite size, and degree of crystallinity. The morphology ranges
from platy to prismatic and the microstructure from mosaic crystals exhibiting {100} faces to bulky crystals. The reactivity
of these samples during oxidation as well as their catalytic reactivity studied in flow reactor is accounted for by the microstructure.
The highest reoxidation capability and the best catalytic properties in oxidation of n-butane to maleic anhydride are obtained with mosaic crystals.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
86.
A functional biopolymer - polydopamine (Pdop) layer was easily modified on the surface of indium tin oxide substrates by spontaneous oxidative polymerization in a dopamine solution. The Pdop layer functions as a novel and promising protector for electrochemical growth of flowerlike gold nanostructures (AuNFs). Electrochemical investigations and SEM results demonstrate that Pdop coating is favored to rapid gold nucleation. The application of AuNFs in surface-enhanced Raman scattering is investigated by using rhodamine 6G as probe molecule. Its detection limit reaches as low as 10−12 M. Pdop coating as a functional platform to prepare AuNFs is promising for potential applications in sensitive optical chemical sensors. 相似文献
87.
Recent progress in electrospun nanofibers and their applications in heavy metal wastewater treatment
Xizi Xu He Lv Mingxin Zhang Menglong Wang Yangjian Zhou Yanan Liu Deng-Guang Yu 《Frontiers of Chemical Science and Engineering》2023,17(3):249
Novel adsorbents with a simple preparation process and large capacity for removing highly toxic and nondegradable heavy metals from water have drawn the attention of researchers. Electrospun nanofiber membranes usually have the advantages of large specific surface areas and high porosity and allowing flexible control and easy functionalization. These membranes show remarkable application potential in the field of heavy metal wastewater treatment. In this paper, the electrospinning technologies, process types, and the structures and types of nanofibers that can be prepared are reviewed, and the relationships among process, structure and properties are discussed. On one hand, based on the different components of electrospun nanofibers, the use of organic, inorganic and organic−inorganic nanofiber membrane adsorbents in heavy metal wastewater treatment are introduced, and their advantages and future development are summarized and prospected. On the other hand, based on the microstructure and overall structure of the nanofiber membrane, the recent progresses of electrospun functional membranes for heavy metal removal are reviewed, and the advantages of different structures for applications are concluded. Overall, this study lays the foundation for future research aiming to provide more novel structured adsorbents. 相似文献
88.
The fabrication of a new type of one-dimensional Au-Ag porous nanotube (NPT) structure was presented based on a facile combination of nanocrystal growth and surface modification. Ag nanowires with various diameters were firstly served as the chemical plating templates via a polyol-process. Then, one-dimensional (1D) Au-Ag porous nanostructures with tailored structural features could be prepared by controlling the individual steps involved in this process, such as nanowire growth, surface modification, thermal diffusion, and dealloying. Structural characterizations reveal these Au-Ag porous nanotubes, non-porous nanotubes and porous nanowires possess novel nano-architectures with multimodal open porosity and excellent structural continuity and integrity, which make them particularly desirable as novel 1D nanocarriers for biomedical, drug delivery and sensing applications. 相似文献
89.
Brian J. Watson Boualem Hammouda Robert M. Briber Steven W. Hutcheson 《应用聚合物科学杂志》2013,127(4):2620-2627
Organic liquids have been used in pretreatments to improve the digestibility of lignocellulosic biomass, ultimately reducing the amount of enzyme required to digest the material to its constituent sugars. To understand the influence of these solvents on cellulose nanostructure, phosphoric acid was used to solubilize cellulose (PAS cellulose) followed by washing of the PAS cellulose with organic liquids previously demonstrated to aid pretreatment. PAS cellulose washed using methanol, ethanol, and ethylene glycol had gel‐like properties with disrupted nanostructures. PAS cellulose washed with acetone, 2‐propanol, and water yielded an opaque white precipitate. Small‐angle neutron scattering indicated the formation of loosely bundled rods of cellulose in the gel‐like material. Fourier transform infrared resonance of solvent‐washed, flash‐dried PAS cellulose suggested an increase in interchain hydrogen bonds in the gel‐like precipitates relative to the more obvious precipitates formed in other solvents. The optimal wash liquid was determined to be 40% by volume ethanol in water to induce a highly digestible, gel‐like material. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
90.
E. Sani L. Mercatelli S. Barison C. Pagura F. Agresti L. Colla P. Sansoni 《Solar Energy Materials & Solar Cells》2011,95(11):2994-3000
The optical characterization is reported of a new fluid consisting of single-wall carbon nanohorns and ethylene glycol for solar energy applications. Carbon nanohorns play a significant role in enhancing sunlight absorption with respect to the pure base fluid. The obtained results are compared with those obtained for fluids suspending more conventional carbon forms, i.e. carbon-black particles. We found that nanohorn spectral features are far more favorable than those of amorphous carbon for the specific application. This result shows that carbon nanohorn-based nanofluids can be useful for increasing the efficiency and compactness of thermal solar devices, reducing both environmental impact and costs. 相似文献