全文获取类型
收费全文 | 511篇 |
免费 | 68篇 |
国内免费 | 64篇 |
专业分类
化学 | 329篇 |
晶体学 | 13篇 |
力学 | 31篇 |
综合类 | 10篇 |
数学 | 60篇 |
物理学 | 200篇 |
出版年
2024年 | 4篇 |
2023年 | 6篇 |
2022年 | 19篇 |
2021年 | 18篇 |
2020年 | 25篇 |
2019年 | 18篇 |
2018年 | 20篇 |
2017年 | 10篇 |
2016年 | 32篇 |
2015年 | 32篇 |
2014年 | 33篇 |
2013年 | 36篇 |
2012年 | 41篇 |
2011年 | 32篇 |
2010年 | 31篇 |
2009年 | 25篇 |
2008年 | 14篇 |
2007年 | 24篇 |
2006年 | 24篇 |
2005年 | 23篇 |
2004年 | 10篇 |
2003年 | 9篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 10篇 |
1997年 | 7篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 6篇 |
1993年 | 17篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 3篇 |
排序方式: 共有643条查询结果,搜索用时 15 毫秒
1.
Jing Zhihong Ling Baoping Yu Yang Qi Wei Zhang Shufang 《Journal of Sol-Gel Science and Technology》2015,73(1):112-117
Journal of Sol-Gel Science and Technology - A novel gas sensing material, La–Y co-doped TiO2 nanoparticles, was synthesized by sol–gel method and applied to detect organic pollutants... 相似文献
2.
3.
在pH5.3的HAc-NaAc、2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基酚(3,5-Br2-PADAP)、溴代十六烷基三甲铵(CTMAB)溶液中,用线性扫描示波极谱法可得到锑(Ⅲ)的络合物吸附波。峰电位为-0.70V(vs.SCE)。二阶导数档峰高与Sb(Ⅲ)浓度在3.3X10-8~2.5X10-6mol/L范围内呈线性关系。检出限为8.2X10-9mol/L。用多种电化学方法研究了极谱波的性质及电极反应机理。络合物组成为Sb(Ⅲ):3,5-Br2-PADAP=1∶2。加入CTMAB可消除试剂峰且提高灵敏度。试验了30多种离子对峰电流的影响,用流基棉分离干扰离子。方法已用于矿样中锑的测定。 相似文献
4.
5.
Three new alkaloids, longistylumphyllines A–C (1–3), together with the six known alkaloids deoxycalyciphylline B, deoxyisocalyciphylline B, methyl homosecodaphniphyllate, daphnicyclidin A, daphnicyclidin B, and daphnicyclidin F, were isolated from the stems and leaves of Daphniphyllum longistylum. Their structures and relative configuration were elucidated on the basis of spectroscopic data, especially 1D and 2D NMR techniques. 相似文献
6.
Zhibin Li Yan Zhang Kuiliang Li Zhenghong Zhou Zhenggen Zha Zhiyong Wang 《中国科学:化学(英文版)》2021,(12):2134-2141
A selective electrochemical oxidation was developed under mild condition.Various mono-carbonyl and multi-carbonyl com-pounds can be prepared from different arom... 相似文献
7.
Chen H Aleksandrov A Chen Y Zha S Liu M Orlando TM 《The journal of physical chemistry. B》2005,109(22):11257-11262
Polycrystalline gadolinia-doped ceria (GDC) surfaces were studied using low-energy (5-400 eV) electron stimulated desorption (ESD). H(+), O(+), and H(3)O(+) were the primary cationic desorption products with H(+) as the dominant channel. H(+), H(3)O(+), and O(+) have a 22 eV threshold followed by a yield change around 40 eV. H(+) also has an additional yield change approximately 75 eV and O(+) has an additional change approximately 150 eV. The O(+) ESD yield change approximately 150 eV may indicate bond breaking of Gd-O and the involvement of oxygen vacancies. The H(+) and H(3)O(+) threshold data collectively indicate the presence of hydroxyl groups and chemisorbed water molecules on the GDC surfaces. ESD temperature dependence measurements show that the interaction of water with GDC surface defect sites, mainly oxygen vacancies, influences the desorption of H(+), O(+), and H(3)O(+). The temperature dependence of the O(+) ESD at 400 eV incident electron energy yields a 0.21 eV activation energy. This is close to the energy needed for oxygen vacancy production next to a pair of Ce(3+) on a CeO(2) surface. These results may indicate a correlation between the O(+) ESD yield and oxygen vacancy density on GDC surfaces and a potential correlation of O(+) ESD and GDC ionic conductivity. 相似文献
8.
Kedong Xia Chunxiang Lu Yu Yang Baoping Zhang 《Journal of Sol-Gel Science and Technology》2014,69(2):266-271
The effect of vinyltriethoxysilane (VTES) addition on the pyrolytic conversion of tetraethoxysilane (TEOS) based silica gel had been studied. Thermogravimetric analysis coupled with mass spectroscopy was carried out to study the thermal decomposition behavior of precursor gels. The ceramic yield of precursor gels was decreased with the increase of the VTES content. 29Si magic angle spinning nuclear magnetic resonance indicated that the incorporation of VTES into TEOS not only changed the composition and structure of precursor gels, but also increased carbon-enriched SiO x C4?x units of silicon oxycarbide ceramics during the pyrolysis conversion. The carbon content of SiOC ceramic was almost unchanged between 1,000 and 1,500 °C. However, the O/Si ratio of the silicon oxycarbide ceramic was reduced and the free carbon content was increased with the increasing molar ratios of VTES/TEOS. Moreover, the carbothermal reduction reaction led to the free carbon content decreased with the increase of the sintering temperature. 相似文献
9.
Intermolecular H···O═C bonds induced 2D self‐assembly of thiophene based diketopyrrolopyrrole derivative 下载免费PDF全文
Yican Wu Jinxing Li Bao Zha Xinrui Miao Lei Ying Wenli Deng 《Surface and interface analysis : SIA》2017,49(8):735-739
Compounds with diketopyrrolopyrrole (DPP) and thiophene moieties have attracted considerable attention because of their promising charge transport properties. The molecular conformation and self‐assembly of 2,5‐dihexadecyl‐3,6‐di(thiophen‐2‐yl)‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione (TDPP‐C16) molecule have been investigated by scanning tunneling microscopy and density functional theory alculation. The TDPP‐C16 molecules adsorb with their optimized S‐shaped conformation and form a zipper‐like pattern on highly oriented pyrolytic graphite surface. R and S rotated structures are observed. The nanostructure is dominated by intermolecular double hydrogen bonds between C═O of the DPP units and hydrogen atom of thiophene rings in the neighboring molecules in each row. Atomic force microscopy and density functional theory calculation also display the existence of strong intermolecular hydrogen bonding. The results provide molecular evidence for the intermolecular interactions of the surface structure, which could benefit to the design of the organic semiconducting materials and understanding of underlying principle of charge transfer process. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
10.