全文获取类型
收费全文 | 235篇 |
免费 | 7篇 |
国内免费 | 82篇 |
专业分类
化学 | 253篇 |
晶体学 | 1篇 |
力学 | 3篇 |
物理学 | 67篇 |
出版年
2024年 | 1篇 |
2023年 | 18篇 |
2022年 | 16篇 |
2021年 | 25篇 |
2020年 | 29篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 22篇 |
2016年 | 16篇 |
2015年 | 12篇 |
2014年 | 15篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 19篇 |
2010年 | 10篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 4篇 |
1994年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有324条查询结果,搜索用时 359 毫秒
81.
In this paper, the effective method for nitrogen-doped TiO2−xNx photocatalyst coated on hollow glass microbeads is described, which uses titanium tetraisopropoxide [Ti(iso-OC3H7)4] as the raw materials and gaseous ammonia as a heat treatment atmosphere. The effects of heat treatment temperature and time on the photocatalytic activity of TiO2−xNx/beads are studied. The photocatalyst is characterized by the UV-vis diffuse reflection spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis and scanning electron microscopy (SEM). The results show that when the TiO2−xNx/beads is heated at 650 °C for 5 h, the photocatalytic activity of the TiO2−xNx/beads is the best. Compared with TiO2, the photoabsorption wavelength range of nitrogen-doped TiO2−xNx red shifts of about 60 nm, and the photoabsorption intensity increases as well. The photocatalytic activity of the TiO2−xNx/beads is higher than that of the TiO2/beads under visible light irradiation. The presence of nitrogen neither influences on the transformation of anatase to rutile, nor creates new crystal phases. When the TiO2−xNx/beads is heated at 650 °C for 5 h, the amount of nitrogen-doped is 0.53 wt.% in the TiO2−xNx. As the density of TiO2−xNx/beads prepared is lower than 1.0 g/cm3, it may float on water surface and use broader sunlight spectrum directly. 相似文献
82.
光沉积法合成纳米金属Pd负载的MCM-TiO2及其光催化性质研究 总被引:9,自引:0,他引:9
用光沉积方法由PdCl42-和Ti修饰的MCM-41合成了纳米钯团簇Pd/MCM-TiO2,用XPS,N2吸脱附等温线,UV-Vis和Raman光谱对其结构进行了表征.将该团簇用于苯酚的光降解和Cr(Ⅵ)还原为Cr(Ⅲ)的反应中,表现出较高的光催化活性. 相似文献
83.
《中国化学快报》2020,31(12):3065-3072
As a highly strained small molecule, [1.1.1]propellane has been widely used in various synthetic transformations owing to the exceptional reactivity of the central bond between the two bridgehead carbons. Utilizing strain-release approaches, the rapid development of strategies for the construction of bicyclo[1.1.1]pentane (BCP) and cyclobutane derivatives using [1.1.1]propellane as the starting material has been witnessed in the past few years. In this review, we highlight the most recent advances in this field. Accordingly, the reactivity of [1.1.1]propellane can be divided into three pathways, including radical, anionic and transition metal-catalyzed pathways under appropriate conditions. 相似文献
84.
Abstract Although sol-gel method is an easy procedure to form a thin film, it's extremely difficult to coat on the surface of small size particles, fibers, and fiber ceramics, because concentration occurs by capillary phenomena and causes peeling or breakage of film. In order to solve this problem, we use supercritical CO2 rapid expansion from supercritical solution (RESS), nano-sized particles of TiO2 with high intensity can be sprayed out of a nozzle, then collected on the surface of substrates, but can be absorbed into fibers or porous materials, being not interfered by viscosity of a solution. TiO2 sol made by hydrolysis process is set in a pressure cell and mixed together with super-critical CO2. Controlling the pressure and the temperature, we could obtain TiO2 sol and super critical fluid mixture, and then discharge to the substrate. At this point, Titania sol viscosity is so low that a surface wettability of the substrate becomes negligible. By the use of the characteristics of the supercritical fluid, without constraint condition of viscosity or capillarity, this sol can penetrate into the interstices of the substance's structure. Thus, clearing obstruction of capillary phenomena, supercritical fluid coating method shows its capability to penetrate deep into inside of entangled fiber of the three-dimensional structure so as considered to be a heat resistant filter with 95% porosity. 相似文献
85.
Hai MingHengchao Zhang Zheng MaHui Huang Suoyuan LianYing Wei Yang Liu Zhenhui Kang 《Applied Surface Science》2012,258(8):3846-3853
Carbon-TiO2 nanohybrids (CTs, 5-10 nm TiO2 nanocrystals evenly dispersed on carbon film) have been successfully prepared via a mild, one-step hydrothermal approach. The interactions and electronic structures of carbon and TiO2 nanoparticles and the enhanced visible photocatalytic mechanism were investigated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy and cyclic voltammetry in detail. Meanwhile, it was demonstrated that the as-obtained CTs had a large BET specific surface area of 304.6 m2/g and showed excellent photocatalytic abilities towards organic (Rhodamine B, benzene) and inorganic pollutant (K2Cr2O7) degradation in visible light. This work provided a new approach for the high performance catalyst design towards new energy sources and environmental issues. 相似文献
86.
Nanosized tungsten disulfide (WS2) sensitized titanium dioxide (TiO2) was successfully prepared via a simple yet facile hydrothermal process. The nanocomposite exhibited a wide and intensive absorption in the visible light region of 400–700 nm, and may have a potential application as a visible photocatalyst. In addition, the sensitization mechanism of the nano-WS2 was proposed to elaborate the wide visible light absorption of the WS2/TiO2 nanocomposites. 相似文献
87.
In this work, highly photocatalytically active Ho2O3-SiO2 nanocomposites have been designed and applied for decomposition of methylene blue pollutant. Ho2O3-SiO2 nanocomposites have been produced by new, quick and facile sonochemical process with the aid of tetramethylethylenediamine as a novel basic agent for the first time. The effect of the kind of basic agent, ultrasonic time and dosage of Ho source on the grain size, photocatalytic behavior and shape of the Ho2O3-SiO2 nanocomposites have been evaluated for optimization the production condition. FESEM, EDX, FT-IR, DRS, XRD and TEM have been applied to characterize the as-produced Ho2O3-SiO2 nanocomposites. Use of the as-produced Ho2O3-SiO2 nanocomposites as photocatalyst via destruction of methylene blue pollutant under UV illumination has been compared. It was observed that SiO2 has notable impact on catalytic activity of holmium oxide photocatalyst for destruction. Introducing of SiO2 to holmium oxide can enhance destruction efficiency of holmium oxide to methylene blue pollutant under ultraviolet light. 相似文献
88.
A nanocomposite UV‐visible light‐responsive multiwalled carbon nanotube (MWCNT)/titanium dioxide (TiO2) nanophotocatalyst was successfully synthesized by a modified sol‐gel method using titanium isopro... 相似文献
89.
Fast Photodegradation of Malachite Green using Nano-ZnO on Ceramic MgAl Carbonate Layered Double Hydroxides Support 下载免费PDF全文
The nanopowders of Mg-Al carbonate layered double hydroxides (MgAl-LDH) were prepared via coprecipitation process. ZnO nanoparticles were homogeneously coated on the ceramic MgAl-LDH surface. After calcination at 500 ℃ for 4 h, X-ray diffraction and scanning electron microscopy were employed to investigate the crystal structure and morphology, respectively. It was demonstrated that ZnO nanoparticles were successfully prepared on ceramic MgAl-LDH support. The obtained nano-ZnO photocatalyst showed a high pho-tocatalytic degradation of malachite green. The enhanced photocatalytic property can be attributed to both high photocatalytic activity of ZnO and good adsorption behavior of ceramic MgAl-LDH, in which the aky structure of MgAl-LDH plays an important role. 相似文献
90.
Jun Beom Park Nam-Jung Kim Yong-Jin Kim Sang-Hyup Lee Gyu-Chul Yi 《Current Applied Physics》2014,14(11):1437-1442
We report the growth of high-areal-density GaN nanowires on large-size graphene films using a nickel (Ni) catalyst-assisted vapor-liquid-solid (VLS) method. Before the nanowire growth, the graphene films were prepared on copper foils using hot-wall chemical vapor deposition and transferred onto SiO2/Si substrates. Then, for catalyst-assisted VLS growth, Ni catalyst layers with thickness of a few nanometers were deposited on the graphene-coated substrates using a thermal evaporator. We investigated the effect of the Ni catalyst thickness on the formation of GaN nanowires. Furthermore, the structural and optical characteristics of GaN nanowires were investigated using X-ray diffraction, transmission electron microscopy, and photoluminescence spectroscopy. The GaN nanowires grown on graphene films were transferred onto polymer substrates using a simple lift-off method for applications as flexible photocatalysts. Photocatalysis activities of the GaN nanowires prepared on the flexible polymer substrates were investigated under bending conditions. 相似文献