全文获取类型
收费全文 | 941篇 |
免费 | 42篇 |
国内免费 | 563篇 |
专业分类
化学 | 1329篇 |
力学 | 2篇 |
综合类 | 1篇 |
物理学 | 214篇 |
出版年
2023年 | 191篇 |
2022年 | 91篇 |
2021年 | 99篇 |
2020年 | 119篇 |
2019年 | 63篇 |
2018年 | 78篇 |
2017年 | 67篇 |
2016年 | 65篇 |
2015年 | 64篇 |
2014年 | 60篇 |
2013年 | 49篇 |
2012年 | 55篇 |
2011年 | 66篇 |
2010年 | 56篇 |
2009年 | 63篇 |
2008年 | 67篇 |
2007年 | 51篇 |
2006年 | 46篇 |
2005年 | 36篇 |
2004年 | 26篇 |
2003年 | 19篇 |
2002年 | 15篇 |
2001年 | 22篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 13篇 |
排序方式: 共有1546条查询结果,搜索用时 93 毫秒
91.
以钛酸四丁酯为钛源,通过盐酸调制的水热法制备出了具有棒状结构的金红石相纳米TiO2,并进一步进行高温氢化处理.采用X射线衍射(XRD),透射电镜(TEM),紫外-可见-近红外漫反射(UV-Vis-NIR DRS),电子顺磁共振(EPR)和表面光伏(SPS)等测试手段对样品进行表征,以气相乙醛和液相苯酚为目标污染物考察催化剂的光催化活性.结果表明:随着高温氢化处理时间的延长,TiO2样品的可见光吸收逐渐增强,其颜色逐渐由白色转变成灰色,这主要与引入的Ti3+/氧空位缺陷有关.表面光电压谱和羟基自由基测试表明,适当时间的氢化处理有利于光生电荷的分离.在光催化氧化降解气相乙醛和液相苯酚过程中,经适当时间氢化处理的样品表现出高的可见光催化活性.并且可见光催化活性的规律与紫外光下的是一致的.这是因为氢化处理后在导带底下方引入了缺陷能级,拓展了可见光响应.过度的氢化处理会在TiO2导带下方引入较低的缺陷能级,使光生电荷的复合加剧,导致光催化活性降低. 相似文献
92.
污染物甲胺为电子给体可见光下Pt/ZnIn2S4光催化制氢 总被引:1,自引:1,他引:0
用水热法制备了ZnIn2S4固溶体,并通过XRD和UV-vis漫反射光谱进行了表征.研究了一甲胺、二甲胺和三甲胺为给电子体,在Pt/ZnIn2S4上的可见光光催化制氢及自身的降解反应.3种甲胺都能显著提高光催化分解水制氢活性,同时自身得到很好的降解.电子给体的放氢活性顺序为:TMADMAMMA.通过红外衰减全反射(ATR-IR)法检测电子给体在ZnIn2S4表面的吸附行为,吸附强度大小依次为MMADMATMA.光催化活性与分子结构和在催化剂表面的吸附行为有关.3种污染物浓度对放氢活性的影响都符合Langmuir-Hinshelwood动力学模型.讨论了可能的化学反应机理. 相似文献
93.
Nano-composite of Fe-doped anatase TiO2 nanocrystals loaded on the hollow glass microbeads was prepared by co-thermal hydrolysis deposition and calcining treatment. The adherence of TiO2 mesoporous layers to the surfaces of hollow glass microbeads prevented the aggregation of TiO2 nanoparticles and benefited to their catalytic activity. The doping of Fe ions makes the absorption edge of the TiO2 based nano-composite red-shifted into the visible region. An effective photodegradation of the methyl orange aqueous solution was achieved under visible light (λ>420 nm) irradiation, revealing the potential applicability of such nano-composite in some industry fields, such as air and water purifications. 相似文献
94.
Chongyin Yang 《Journal of solid state chemistry》2009,182(4):807-9331
Visible-light-responsive composite photocatalysts SnS2/TiO2 and SnS/TiO2 with different mass ratios were prepared by in-situ synthesis technology in solution with commercial TiO2. The junction-based materials SnSx (x=1, 2)/TiO2 were found to have high visible-light photocatalytic performance and possess much better activity than the single-phase SnSx or TiO2. The greatly enhanced photocatalytic activity of the SnSx/TiO2 composites was mainly attributed to the matching band potentials and efficient charge transfer and separation at the tight-bonding interface between SnSx and TiO2. The fact was confirmed by the comparison of photocatalytic activities of the SnS2/TiO2 samples prepared by physical mixing method and in-situ synthesis technique. 相似文献
95.
Vladimir A. Otroshchenko Nelly V. Vasilyeva 《Reaction Kinetics and Catalysis Letters》2009,97(1):151-156
An opportunity of the abiogenic formation of oligonucleotides over the surface of montmorillonite particles, preliminarily
irradiated with UV light, was found upon the adsorption of mononucleotides on this surface. A probable mechanism of such a
synthesis is suggested. 相似文献
96.
纳米复合光催化剂TiO_2-ZrO_2的制备、表征及其光催化活性 总被引:2,自引:1,他引:1
通过溶胶-凝胶技术制备了不同比例(3:1、1:1、1:3)的纳米复合光催化材料TiO2-ZrO2,采用XRD、N2吸附、SEM-EDX和TPD等测试手段对其进行了表征,探讨了比例不同的TiO2-ZrO2结构的变化规律以及这种变化对催化剂催化活性的影响.通过紫外区和可见区的光催化降解染料亚甲基蓝、罗丹明B的实验,考察了其光催化活性.实验结果表明,不同比例的纳米复合光催化材料TiO2-ZrO2的催化活性均高于单体TiO2和单体ZrO2. 相似文献
97.
Sujun Yuan Yaogang Li Qinghong Zhang Hongzhi Wang 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,348(1-3):76-81
The nanocomposites of magnesium–aluminium–carbonate–layered double hydroxides (Mg–Al–CO3–LDHs) and ZnO nanorods were prepared via a homogeneous precipitation process. The presence of ZnO nanorods made the calcined Mg–Al–CO3–LDHs, the strong adsorptive adsorbents for anions, have a photocatalytic activity. Both Mg–Al–CO3–LDHs and the nanocomposites with various ZnO/Mg–Al–CO3–LDHs mass ratios from 0.5:1 to 3:1 were characterized by X-ray diffraction, transmission electron microscope and UV–vis diffuse reflectance spectra. The nanocomposites quickly adsorbed the anionic dyes such as acid red G (ARG) without the light illumination, and the adsorbed dyes on the recovered nanocomposites were then degraded in a separated photocatalytic reactor. The adsorption ability of the nanocomposites and their photocatalytic activities for the removal of ARG were evaluated by the Fourier transform infrared spectra and UV–vis extinction spectra. The sample at 3:1 ZnO/Mg–Al–CO3–LDHs mass ratio was shown to have higher photocatalytic efficiencies. 相似文献
98.
Yanfang Shen Tianying Xiong Hao Du Huazi Jin Jianku Shang Ke Yang 《Journal of Sol-Gel Science and Technology》2009,50(1):98-102
P, N, and Mo ternary co-doped nano TiO2 photocatalysts ((P, N, Mo)-TiO2) were prepared by a single step sol–gel method, which show much enhanced photocatalytic activities over Mo-TiO2, (P, N)-TiO2, un-doped TiO2 and Degussa P25 under visible light irradiation. The degradation rate of 0.72Mo–P-TiO2 is as high as 65.3%, which is about 6.7 times of that of Degussa P25. Possible reasons for the improvement of photocatalytic
activities were analyzed. 相似文献
99.
The objective of this study was to evaluate the performance of a photocatalysis/H2O2/metal membrane hybrid system in the degradation of humic acid. A metal membrane of nominal pore size 0.5 μm was used in the
experiment for separation of TiO2 particles. Hydrogen peroxide was tested as an oxidant. The efficiency of removal of CODCr and color increased rapidly for initial hydrogen peroxide concentrations up to 50 mg L−1. The efficiency of removal of CODCr and color by 50 mg L−1 initial hydrogen peroxide concentration was approximately 95 and 98%, respectively. However, addition of hydrogen peroxide
over 50 mg L−1 inhibited the efficiency of the system. Addition of hydrogen peroxide to a UV/TiO2 system enhanced efficiency of removal of CODCr and color compared with no addition of hydrogen peroxide. This may be ascribed to capture electrons ejected from TiO2 and to the production of OH radicals. Application of the metal membrane in the UV/TiO2/H2O2 system enhanced the efficiency of removal of CODCr and color because of adsorption by the metal membrane surface and the production of OH radicals. By application of a metal
membrane with a nominal pore size of 0.5 μm, TiO2 particles were effectively separated from the treated water by metal membrane rejection. The photocatalytic metal membrane
had much less resistance than the humic acid, TiO2, and humic acid/TiO2 because of the degradation of humic acid by the photocatalytic reaction. 相似文献
100.
Rafael Libanori Tania R. Giraldi Elson Longo Edson R. Leite Caue Ribeiro 《Journal of Sol-Gel Science and Technology》2009,49(1):95-100
Commercial TiO2 nanoparticles were superficially modified through polymeric resins obtained from polymerization of citrate complexes of Y3+ and Al3+ with ethylenglycol. The materials were treated at 450 °C for 4 h to obtain modified nanoparticles, which were characterized
by HR-TEM, Zeta potential and surface area through N2 fisisorption. Rhodamine B photodegradation by visible light irradiation and in presence of those modified nanoparticles was
compared with the same process in presence of unmodified commercial TiO2 nanoparticles. It was observed, by UV–visible spectroscopy, that the catalytic photoactivity in presence of modified nanoparticles
was smaller than that observed with commercial TiO2 nanoparticles. However, the surface modifier played an important role in the photodegradation kinetic process, showing a
non-linear relation between modifier amount and photodegradation rate, presenting a maximum value at 0.8% (w/w). 相似文献