全文获取类型
收费全文 | 515篇 |
免费 | 64篇 |
国内免费 | 52篇 |
专业分类
化学 | 415篇 |
晶体学 | 2篇 |
力学 | 15篇 |
综合类 | 6篇 |
数学 | 54篇 |
物理学 | 139篇 |
出版年
2024年 | 2篇 |
2023年 | 22篇 |
2022年 | 48篇 |
2021年 | 53篇 |
2020年 | 60篇 |
2019年 | 49篇 |
2018年 | 35篇 |
2017年 | 33篇 |
2016年 | 37篇 |
2015年 | 27篇 |
2014年 | 21篇 |
2013年 | 28篇 |
2012年 | 24篇 |
2011年 | 22篇 |
2010年 | 10篇 |
2009年 | 15篇 |
2008年 | 10篇 |
2007年 | 13篇 |
2006年 | 14篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 15篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有631条查询结果,搜索用时 15 毫秒
131.
Head–Tail Asymmetry as the Determining Factor in the Formation of Polymer Cubosomes or Hexasomes in a Rod–Coil Amphiphilic Block Copolymer
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Xiaolin Lyu Anqi Xiao Wei Zhang Pingping Hou Kehua Gu Zhehao Tang Hongbing Pan Fan Wu Prof. Zhihao Shen Prof. Xing‐He Fan 《Angewandte Chemie (International ed. in English)》2018,57(32):10132-10136
The self‐assembly of a rod–coil amphiphilic block copolymer (ABCP) led to Im m and Pn m polymer cubosomes and p6mm polymer hexasomes. This is the first time that these structures are observed in a rod–coil system. By varying the hydrophobic chain length, the initial concentration of the polymer solution, or the solubility parameter of the mixed solvent, head–tail asymmetry is adjusted to control the formation of polymer cubosomes or hexasomes. The formation mechanism of the polymer cubosomes was also studied. This research opens up a new way for further study of the bicontinuous and inverse phases in different ABCP systems. 相似文献
132.
Wenyuan Li Bo Guan Mingliang Liu Bo Wei Xingbo Zhu Zhihong Wang Zhe Lü 《Journal of Solid State Electrochemistry》2018,22(6):1735-1743
The efficiency of impregnation methods for making Cu-based solid oxide fuel cells (SOFCs) is qualitatively characterized for the first time through a conformal coating model. It is found that the low-efficiency results from the uneven distribution of Cu instead of the small loading. Most of the Cu deposits form isolated islands, e.g., in a 20.4 vol.% Cu-loaded anode, 81% Cu is isolated from each other. In order to address the limited impregnation efficiency, two different procedures are adopted to fabricate the practical Cu/CeO2 anodes, namely, simultaneous and sequential impregnation procedures. It is found that CeO2 works as a solid dispersant, improving the Cu distribution drastically. Compared to the Cu-only anode, more than a threefold improvement of impregnation efficiency is achieved by both methods. The anode made by the sequential impregnation yields the best performance in CH4 at 700 °C, 170 mW cm?2, which represents an 18% enhancement over that of the simultaneous impregnation, or 340% over the Cu-only anode. These findings demonstrate that it is of importance to optimize the Cu impregnation to yield a highly active anode, and the sequential impregnation method is a promising procedure to break the efficiency-limiting factor and produce a high-performance anode with minimized fabrication effort. 相似文献
133.
Yonglin He Hailiang Liao Shanzhi Lyu Xiao-Qi Xu Zhengke Li Iain McCulloch Wan Yue Yapei Wang 《Chemical science》2021,12(14):5177
Great attention is being increasingly paid to photothermal conversion in the near-infrared (NIR)-II window (1000–1350 nm), where deeper tissue penetration is favored. To date, only a limited number of organic photothermal polymers and relevant theory have been exploited to direct the molecular design of polymers with highly efficient photothermal conversion, specifically in the NIR-II window. This work proposes a fused backbone structure locked via an intramolecular hydrogen bonding interaction and double bond, which favors molecular planarity and rigidity in the ground state and molecular flexibility in the excited state. Following this proposal, a particular class of NIR-II photothermal polymers are prepared. Their remarkable photothermal conversion efficiency is in good agreement with our strategy of coupling polymeric rigidity and flexibility, which accounts for the improved light absorption on going from the ground state to the excited state and nonradiative emission on going from the excited state to the ground state. It is envisioned that such a concept of coupling polymeric rigidity and flexibility will offer great inspiration for developing NIR-II photothermal polymers with the use of other chromophores.Low bandgap and large deformation generally conflict each other. This work couples molecular rigidity and flexibility by intramolecular hydrogen bonds and double bonds to achieve NIR-II light absorption and reinforced internal conversion at the same time. 相似文献
134.
柱前衍生反相高效液相色谱法测定七种中药补养药中氨基酸 总被引:2,自引:0,他引:2
首次分离并测定了七神中药补养药中氨基酸,为其补益作用提供了科学依据.并建立了中药补养药的FMOC-氨基酸色谱测定方法。以FMOC-Cl(9-芴基甲氧基羰酰氯)为柱前衍生试剂,用反相高教液相色谱法测定氨基酸是国内报道甚少的新方法。该法衍生操作简单,衍生反应迅速.衍生物稳定,方法的灵敏度高、分辨率好,整个分析过程简捷,耗用时间短,优于用氨基酸分析仪分析氨基酸。常用的OPA(邻苯二甲醛)柱前衍生法不能直接测定二级胺类的氨基酸,该法则可直接测定一级及二级胺类的氨基酸.同时,该法受样品基质干扰少,从而为衍生物样品的氨基酸分析开辟了广阔前景。本文用该法测定了七种氨基酸,获得了较满意结果,并认为该法对中草药及重要天然植物资源的研究是一个简捷,准确且极其实用的新方法。 相似文献
135.
136.
Hyunseok Shim Hong-Kun Lyu Bunyod Allabergenov Yuriy Garbovskiy Anatoliy Glushchenko 《Liquid crystals》2016,43(10):1390-1396
Through the ferroelectric nanoparticles of BaTiO3 (BTO) doping, the response time for the frequency modulation of the polymer-dispersed liquid crystal (PDLC) was improved. The BTO-doped PDLC cells were prepared by polymerisation induced phase separation (PIPS) process using UV light. The capacitance of the PDLC composites was measured with an impedance analyzer in the frequency range of 100 Hz–1 MHz at 1 V. The dynamic signal for the response time of the PDLC devices was monitored through a digital oscilloscope. The electro-optical properties of the PDLC were found to strongly depend on the doped BTO concentration. The BTO doping caused a large increase in the capacitance. The dielectric constants were drastically decreased in the samples with rather low BTO doping ratio at a high frequency. No outstanding difference in the rising time of the LC was observed in the BTO-doped PDLC device, but the falling time was significantly decreased from 0.334 to 0.094 s. The present results imply that the nanoparticle-doping technology could improve the electro-optical performance of the PDLC requiring fast response and frequency modulation, such as optical modulators and PDLC-hybrid electroluminescence device for flexible electronic devices. 相似文献
137.
Hui Qin Yuanyuan Miao Ke Zhang Jian Xu Haopeng Sun Wenyuan Liu Feng Feng Wei Qu 《Tetrahedron》2018,74(47):6809-6814
A practical convenient conversion of oxindoles into the corresponding spirocyclopropyl oxindoles is achieved efficiently using bromoethylsulfonium salt, which is easily prepared on a large scale and is stable crystalline. This reaction of bromoethylsulfonium salt with different substituted unprotected oxindoles proceeded under mild condition and provided moderate yields. 相似文献
138.
139.
140.
Sheng Xianxian Xu Zhiqiang Liu Yulong Wang Peng Dong Jiaqi Lu Zhanpeng Shan Ali Lyu Shuguang 《Research on Chemical Intermediates》2022,48(4):1645-1663
Research on Chemical Intermediates - In this study, the removal performance and degradation mechanisms of fluoranthene (FLT) in sodium percarbonate (SPC) activated by Fe(II) system were... 相似文献