全文获取类型
收费全文 | 378篇 |
免费 | 23篇 |
国内免费 | 259篇 |
专业分类
化学 | 589篇 |
力学 | 1篇 |
数学 | 1篇 |
物理学 | 69篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 5篇 |
2020年 | 26篇 |
2019年 | 16篇 |
2018年 | 12篇 |
2017年 | 2篇 |
2016年 | 18篇 |
2015年 | 20篇 |
2014年 | 28篇 |
2013年 | 24篇 |
2012年 | 37篇 |
2011年 | 45篇 |
2010年 | 47篇 |
2009年 | 19篇 |
2008年 | 42篇 |
2007年 | 44篇 |
2006年 | 43篇 |
2005年 | 33篇 |
2004年 | 30篇 |
2003年 | 23篇 |
2002年 | 15篇 |
2001年 | 16篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1962年 | 3篇 |
排序方式: 共有660条查询结果,搜索用时 15 毫秒
1.
Yongfeng Wang 《Surface science》2006,600(3):729-734
Scanning tunneling microscopy (STM) was used to study the surface structures of dry-prepared and di-chloroethane-treated HOPG samples. Both triangular and honeycomb structures were simultaneously observed with the same tip at room temperature around a strand (grain boundary) on the HOPG surface. This observation did not support the tip effect in STM imaging explanation for HOPG in literature. A general layer-sliding model was utilized to explain the experimental results: sliding of the HOPG topmost layer was used to explain the origins of the triangular and honeycomb structures, and molecule intercalation into inter-layer spacing between the first and second layers of HOPG induced inhomogeneous deformation of the HOPG topmost layer that accordingly generated the Moiré patterns of the HOPG sample in di-chloroethane. 相似文献
2.
Dr. Feifan Wang Jie Tian Dr. Mengzhu Li Dr. Weizhen Li Dr. Lifang Chen Xiaozhi Liu Dr. Jian Li Aidaer Muhetaer Prof. Dr. Qi Li Prof. Dr. Yuan Wang Prof. Dr. Lin Gu Prof. Dr. Ding Ma Prof. Dr. Dongsheng Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(21):8280-8286
Fully utilizing solar energy for catalysis requires the integration of conversion mechanisms and therefore delicate design of catalyst structures and active species. Herein, a MOF crystal engineering method was developed to controllably synthesize a copper–ceria catalyst with well-dispersed photoactive Cu-[O]-Ce species. Using the preferential oxidation of CO as a model reaction, the catalyst showed remarkably efficient and stable photoactivated catalysis, which found practical application in feed gas treatment for fuel cell gas supply. The coexistence of photochemistry and thermochemistry effects contributes to the high efficiency. Our results demonstrate a catalyst design approach with atomic or molecular precision and a combinatorial photoactivation strategy for solar energy conversion. 相似文献
3.
4.
5.
设计合成了具有荧光基团的新型硝酮类自由基捕获探针并对其结构进行了表征.自由基捕获实验结果表明,该探针能实现对超氧阴离子自由基与碳中心自由基的捕获.此外,该自由基捕获探针反应产物的荧光强度与被捕获自由基浓度之间存在相关性,有望建立依据荧光强度分析被捕获自由基浓度的新方法. 相似文献
6.
石墨烯表界面化学修饰及其功能调控 总被引:1,自引:0,他引:1
石墨烯属于碳纳米材料家族中的一员,是一种单层的二维原子晶体,具有高硬度、高导热性、高载流子迁移率等诸多优良特性,被认为是新一代电子学器件的重要基础材料.近年来我们课题组利用石墨烯的这些优良特性在其表界面化学修饰及其功能调控方面开展了一系列研究工作.我们对石墨烯表界面进行了共价或非共价化学修饰,在一定程度上打开了石墨烯的带隙,并发展了具有传感功能的石墨烯器件.我们还制备了基于石墨烯的纳米电极,发展了新一代分子电子器件的普适性制备方法,实现了单分子器件的功能化.展望未来,以石墨烯为代表的碳基纳米材料将继续在纳电子器件研究领域发挥重要作用. 相似文献
7.
Reactivity of Oxygen Radical Anions Bound to Scandia Nanoparticles in the Gas Phase: CH Bond Activation
下载免费PDF全文

Li‐Hua Tian Jing‐Heng Meng Dr. Xiao‐Nan Wu Dr. Yan‐Xia Zhao Dr. Xun‐Lei Ding Prof. Dr. Sheng‐Gui He Dr. Tong‐Mei Ma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(4):1167-1175
The activation of C?H bonds in alkanes is currently a hot research topic in chemistry. The atomic oxygen radical anion (O?.) is an important species in C?H activation. The mechanistic details of C?H activation by O?. radicals can be well understood by studying the reactions between O?. containing transition metal oxide clusters and alkanes. Here the reactivity of scandium oxide cluster anions toward n‐butane was studied by using a high‐resolution time‐of‐flight mass spectrometer coupled with a fast flow reactor. Hydrogen atom abstraction (HAA) from n‐butane by (Sc2O3)NO? (N=1–18) clusters was observed. The reactivity of (Sc2O3)NO? (N=1–18) clusters is significantly sizedependent and the highest reactivity was observed for N=4 (Sc8O13?) and 12 (Sc24O37?). Larger (Sc2O3)NO? clusters generally have higher reactivity than the smaller ones. Density functional theory calculations were performed to interpret the reactivity of (Sc2O3)NO? (N=1–5) clusters, which were found to contain the O?. radicals as the active sites. The local charge environment around the O?. radicals was demonstrated to control the experimentally observed size‐dependent reactivity. This work is among the first to report HAA reactivity of cluster anions with dimensions up to nanosize toward alkane molecules. The anionic O?. containing scandium oxide clusters are found to be more reactive than the corresponding cationic ones in the C?H bond activation. 相似文献
8.
Zi‐Yu Li Zhen Yuan Dr. Yan‐Xia Zhao Prof. Dr. Sheng‐Gui He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(14):4163-4169
Metal carbide species have been proposed as a new type of chemical entity to activate methane in both gas‐phase and condensed‐phase studies. Herein, methane activation by the diatomic cation MoC+ is presented. MoC+ ions have been prepared and mass‐selected by a quadrupole mass filter and then allowed to interact with methane in a hexapole reaction cell. The reactant and product ions have been detected by a reflectron time‐of‐flight mass spectrometer. Bare metal Mo+ and MoC2H2+ ions have been observed as products, suggesting the occurrence of ethylene elimination and dehydrogenation reactions. The branching ratio of the C2H4 elimination channel is much larger than that of the dehydrogenation channel. Density functional theory calculations have been performed to explore in detail the mechanism of the reaction of MoC+ with CH4. The computed results indicate that the ethylene elimination process involves the occurrence of spin conversions in the C?C coupling (doublet→quartet) and hydrogen atom transfer (quartet→sextet) steps. The carbon atom in MoC+ plays a key role in methane activation because it becomes sp3 hybridized in the initial stages of the ethylene elimination reaction, which leads to much lower energy barriers and more stable intermediates. This study provides insights into the C?H bond activation and C?C coupling involved in methane transformation over molybdenum carbide‐based catalysts. 相似文献
9.
Experimental and theoretical study of the reactions between vanadium oxide cluster cations and water
Vanadium oxide cluster cations V(x)O(y)(+) (x = 2-6) are prepared by laser ablation and are reacted with D(2)O in a fast flow reactor under room temperature conditions. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Observation of the products (V(2)O(5))(1-3)D(+) indicates the deuterium atom abstraction reaction (V(2)O(5))(1-3)(+) + D(2)O → (V(2)O(5))(1-3)D(+) + OD. In addition, significant association products (V(2)O(5))(1-3)D(2)O(+) are also observed in the experiments. Density functional theory calculations are performed to study the reaction mechanisms of V(4)O(10)(+) with H(2)O. The calculated results are in agreement with the experimental observations and indicate that H(2)O is dissociatively rather than molecularly adsorbed in V(4)O(10)H(2)O(+) complex. 相似文献
10.