全文获取类型
收费全文 | 718篇 |
免费 | 159篇 |
国内免费 | 88篇 |
专业分类
化学 | 353篇 |
晶体学 | 57篇 |
力学 | 16篇 |
综合类 | 4篇 |
数学 | 7篇 |
物理学 | 528篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 32篇 |
2016年 | 35篇 |
2015年 | 33篇 |
2014年 | 43篇 |
2013年 | 72篇 |
2012年 | 50篇 |
2011年 | 56篇 |
2010年 | 53篇 |
2009年 | 43篇 |
2008年 | 33篇 |
2007年 | 47篇 |
2006年 | 54篇 |
2005年 | 37篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 21篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 40篇 |
1998年 | 9篇 |
1997年 | 19篇 |
1996年 | 10篇 |
1995年 | 14篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 2篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有965条查询结果,搜索用时 984 毫秒
961.
Atomic layer deposition (ALD) is now a widely implemented thin film growing method. It is currently used in industrial fabrication processes of microelectronics and luminescent display technologies. Since compact and conformal films can be grown with perfect control of the thickness, ALD is envisioned in numerous other applications fields such as energy, sensing, biomaterials, and photonics. Although few reports can be found on its application to corrosion protection, it has been shown that the qualities of ALD can be highly beneficial to this field. After a brief review of the principle of ALD and the effect of the main parameters on the properties of the films, this report attempts to show the interest of this technique to mitigate corrosion. Various examples of successful uses of ALD to protect metallic and non-metallic surfaces in different fields are reviewed. 相似文献
962.
Dr. Ploychanok Iadrat Anittha Prasertsab Dr. Mutjalin Limlamthong Prof. Jungkyu Choi Dr. Heon E. Park Prof. Chularat Wattanakit Prof. Alex C. K. Yip 《ChemCatChem》2024,16(6):e202301208
Various commercial zeolites, including FER, MOR, ZSM-5, BEA, and FAU frameworks, were treated with NH4F aqueous solutions to study the effects of fluoride etching on different zeolite frameworks. NH4F-treated small-medium pore FER, MOR, and ZSM-5 samples showed much higher mesoporosities than the untreated ones without alteration of the structural compositions and acidic properties. On the other hand, the 12-membered ring zeolites BEA and FAU showed severe dissolution of the framework aluminosilicate structure after NH4F etching due to the high accessibility of fluoride species into the framework structures. The effect of NH4F concentration on the fluoride treatment of H-ZSM-5 zeolite was specifically studied. From the results, we observed that structural etching with 20 wt % NH4F was optimal for fabricating open-pore H-ZSM-5 zeolite and resulted in a high mesoporosity with comparable relative crystallinity and acidity with respect to the untreated H-ZSM-5. The catalytic activities of the open-pore H-ZSM-5 were evaluated with acid-catalyzed methanol and bioethanol conversions. Remarkably, the hierarchical open-pore H-ZSM-5 zeolite fabricated via fluoride etching exhibited an enhanced catalytic performance in bioethanol conversion with >85 % conversion over 34 h TOS and a higher catalytic stability in methanol conversion than the parent H-ZSM-5 (~50 % of bioethanol conversion at 34 h TOS). 相似文献
963.
Zhong De‐Gao Teng Bing Dong Sheng‐Ming Wang Qing‐Guo Zhao Yan‐Shuai Huang Wan‐Xia Yu Tao 《Crystal Research and Technology》2009,44(5):500-504
Solubility curves of KDP (KH2PO4) in solutions with different pH values were measured. It was found that the solubility of KDP crystal increased with the reduction pH value of solution. Transparent KDP crystal was grown from solution with 1.5 pH by point seed. Chemical etching experiments revealed that pyramid sector of the crystal displayed more growth defects. Growth defects, such as growth striation and inclusion, were analyzed by white‐beam synchrotron radiation X‐ray topography. The reasons for the formation of these growth defects were discussed. Transmittance spectra test of both prismatic sector and pyramidal sector was performed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
964.
Lei Tan Dr. Nianming Jiao Xinrui Bai Dr. Hongyan Wang Prof. Jun Wang Prof. Hui Wang Prof. Xiangping Zhang 《欧洲无机化学杂志》2023,26(24):e202300314
Zeolites are widely used in petrochemical processes and refineries due to their well-ordered microporous network and large surface area. However, the diffusion of reactants and products is hampered by the narrow microporous channels, causing limitations. To overcome this challenge, modifying the pore structure is crucial, and the chemical etching technique is a powerful tool that introduces mesopores and macropores, consequently enhancing mass transfer and accessibility. Diverse chemical etching methods have been invented, including exposure to both acids (organic/inorganic acids), alkali (organic/inorganic alkali), and neutral etchants (e. g., ammonium fluoride). This review summarizes and assesses the chemical etching methods and their relevance to catalytic cracking reactions, methanol to hydrocarbons (MTH), and biomass conversion. The potential of zeolites with modified pore structures has motivated researchers to develop novel methods to tackle the practical challenges associated with their applications. 相似文献
965.
Airton Natanael Coelho Dias Carlos Alberto Tello Saenz Carlos Jos Leopoldo Constantino Cleber Jos Soares Felipe Ponciano Novaes Ana Maria Osrio Araya Balan 《Journal of Raman spectroscopy : JRS》2009,40(1):101-106
The zircon mineral is widely studied in geochronology. In the case of the fission track method (FTM), the age is determined by the density of fission tracks at the zircon surface, which can be observed with an optical microscope after an appropriate chemical treatment (etching). The etching must be isotropic at the zircon grain surface to be used in the FTM, which leads those zircon grains whose etching is anisotropic to be discarded. The only reason for this discarding is the nonuniform morphology of the surface grain seen by optical microscopy, that is, no further physicochemical analysis is performed. In this work, combining micro‐Raman and scanning electron microscopy (SEM) to study the etching anisotropy, it was shown that zircon grains that present at least one area at the surface where the density of fission track is uniform can be used in the FTM. The micro‐Raman showed characteristic spectra of the standard zircon sample either from the areas where there are tracks or from where there are not. The only difference found was in the Raman bandwidths, which were broader for the areas with higher density of fission tracks. This suggests simply a decrease in the relative percentage of the crystalline/amorphous phases at these areas. The SEM/energy dispersive spectrometry (EDX) showed that there were no significant differences in the principal chemical composition at the areas with and without fission tracks. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献