全文获取类型
收费全文 | 167篇 |
免费 | 5篇 |
国内免费 | 18篇 |
专业分类
化学 | 106篇 |
力学 | 14篇 |
综合类 | 1篇 |
数学 | 40篇 |
物理学 | 29篇 |
出版年
2024年 | 2篇 |
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 12篇 |
2011年 | 4篇 |
2010年 | 12篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1981年 | 1篇 |
排序方式: 共有190条查询结果,搜索用时 15 毫秒
101.
In the present work, we show that in processed sorrel, the lutein (1) can convert to 3’-epilutein (2) – 3’-stereoisomer of lutein – by epimerisation reaction, as well as to anhydrolutein I (3) and II (4) by dehydration reaction. The newly formed anhydrolutein I (3) and II (4) were detected and identified by HPLC-DAD and HPLC-MS techniques and co-chromatography with authentic samples. The compounds 1 and 2 were also isolated from cooked sorrel by column chromatography and characterized by NMR spectroscopy. 相似文献
102.
本文在对有机粘结剂的溶液理论、溶剂的选择判据、有机粘结剂和溶剂的溶解度参数等进行了简要介绍之后,重点阐述了作者根据溶解度三参数原理、溶剂相对挥发速率、线性优化数学模型和环境保护规范等编制的选择混合溶剂的电子计算机程序,并对计算结果及其应用也作了一定深度的讨论。 相似文献
103.
Pter Molnr Jzsef Deli Zoltn Matus Gyula Tth Andrea Steck Hanspeter Pfander 《Helvetica chimica acta》1999,82(11):1994-2002
Karpoxanthin (=(all-E,3S,5R,6R,3′R)-5,6-dihydro-β,β-carotene-3,5,6,3′-tetrol; 7 ), 6-epikarpoxanthin (=(all-E,3S,5R,6S,3′R)-5,6-dihydro-β,β-carotene-3,5,6,3′-tetrol; 4 ), 5-epikarpoxanthin (=(all-E,3S,5S,6R,3′-R)-5,6-dihydro-β,β-carotene-3,5,6,3′-tetrol; 11 ), cucurbitaxanthin A (=(all-E,3S,5R,6R,3′R)-3,6-epoxy-5,6-dihydro-β,β-carotene-5,3′-diol; 10 ), epicucurbitaxanthin A (=(all-E-3S,5S,6R,3′R)-3,6-epoxy-5,6-dihydro-β,β-carotene-5,3′-diol; 14 ), and the corresponding mutatoxanthin epimers 8 , 9 , 12 , and 13 were prepared in crystalline state by the acid-catalyzed hydrolysis of (3S,5R,6S,3′R)- and (3S,5S,6R,3′R)-antheraxanthin ( 5 and 6 , resp.) and characterized by their UV/VIS, CD, 1H- and 13C-NMR, and mass spectra. 相似文献
104.
Lide Gu Yuzhe Ding Yang Zhou Prof. Dr. Yao Zhang Prof. Dr. Deli Wang Prof. Dr. Juewen Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(6):e202314450
Previous aptamers for porphyrins and metalloporphyrins were all guanine-rich sequences that can fold in G-quadruplex structures. Due to stacking-based binding, these aptamers can hardly tell different porphyrins apart, and they can also bind other planar molecules, hindering their practical applications. In this work, we used the capture selection method to obtain aptamers for hemin and protoporphyrin IX (PPIX). The hemin aptamer (Hem1) features two highly conserved repeating binding loops, and it cannot form a G-quadruplex, which was supported by its Mg2+-dependent but K+-independent hemin binding and CD spectroscopy. Isothermal titration calorimetry revealed much higher enthalpy change for the new aptamer, and the best aptamer showed a Kd of 43 nM hemin. Hem1 can also enhance the peroxidase-like activity of hemin. This work demonstrates that aptamers have alternative ways to bind porphyrins allowing selective recognition of different porphyrins. 相似文献
105.
106.
Pter Molnr Jzsef Deli Gyula Tth Adrian Hberli Hanspeter Pfander 《Helvetica chimica acta》2002,85(5):1327-1339
(all‐E)‐5,6‐Diepikarpoxanthin (=(all‐E,3S,5S,6S,3′R)‐5,6‐dihydro‐β,β‐carotene‐3,5,6,3′‐tetrol; 1 ) was submitted to thermal isomerization and I2‐catalyzed photoisomerization. The structures of the main products, i.e. (9Z)‐ ( 2 ), (9′Z)‐ ( 3 ), (13Z)‐ ( 4 ), (13′Z)‐ ( 5 ), and (15Z)‐5,6‐diepikarpoxanthin ( 6 ), were determined by their UV/VIS, CD, 1H‐NMR, and mass spectra. In addition, (9Z,13′Z)‐ or (13Z,9′Z)‐ ( 7 ), (9Z,9′Z)‐ ( 8 ), and (9Z,13Z)‐ or (9′Z,13′Z)‐5,6‐diepikarpoxanthin ( 9 ) were tentatively identified as minor products of the I2‐catalyzed photoisomerization. 相似文献
107.
Xiqin Chen Canhong Wang Qingqin He Jian Feng Deli Chen Jianhe Wei Yangyang Liu 《Molecules (Basel, Switzerland)》2022,27(14)
As a valuable medicinal herb and spice, agarwood is widely used in the fields of daily chemistry, traditional medicine, religion and literary collection. It mainly contains sesquiterpenes and 2-(2-phenylethyl)chromones, which are often used to soothe the body and mind, relieve anxiety, act as an antidepressant and treat insomnia and other mental disorders, presenting a good calming effect. This paper reviews the chemical composition of the essential oils of different sources of agarwood, as well as the progress of research on the sedative and tranquilizing pharmacological activity and mechanism of action of agarwood essential oil (AEO), and then analyzes the current problems of AEO research and its application prospects in the treatment of mental diseases. 相似文献
108.
Szilvia Veszelka Mria Mszros Gerg Porkolb gnes Rusznyk Katalin Szszn Rti-Nagy Mria A. Deli Mikls Vecsernys Ildik Bcskay Judit Vradi Ferenc Fenyvesi 《Molecules (Basel, Switzerland)》2022,27(22)
The application of 2-hydroxypropyl-beta-cyclodextrin (HPBCD) in the treatment of the rare cholesterol and lipid storage disorder Niemann–Pick disease type C opened new perspectives in the development of an efficient therapy. Even if the systemic administration of HPBCD was found to be effective, its low permeability across the blood–brain barrier (BBB) limited the positive neurological effects. Nevertheless, the cellular interactions of HPBCD with brain capillary endothelial cells have not been investigated in detail. In this study, the cytotoxicity, permeability, and cellular internalization of HPBCD on primary rat and immortalized human (hCMEC/D3) brain capillary endothelial cells were investigated. HPBCD shows no cytotoxicity on endothelial cells up to 100 µM, measured by impedance kinetics. Using a fluorescent derivative of HPBCD (FITC-HPBCD) the permeability measurements reveal that on an in vitro triple co-culture BBB model, FITC-HPBCD has low permeability, 0.50 × 10−6 cm/s, while on hCMEC/D3 cell layers, the permeability is higher, 1.86 × 10−5 cm/s. FITC-HPBCD enters brain capillary endothelial cells, is detected in cytoplasmic vesicles and rarely localized in lysosomes. The cellular internalization of HPBCD at the BBB can help to develop new strategies for improved HPBCD effects after systemic administration. 相似文献
109.
110.
采用TA-Q800动态热机械分析仪(DMA)研究了聚乙烯基对苯二甲酸二(对丁氧基苯)酯(PBPCS)纤维的形变回复性能,发现PBPCS纤维具有非常好的形状记忆效应,在145℃及以上温度,形状回复速率最好,9min左右可以从400%的伸长回复到原来的尺寸,于145℃,重复实验5次,结果说明形变回复重复性好.二维X衍射(2DX-Ray)研究显示形变前后PBPCS柱状分子直径d由2.54nm变为2.42nm,表明拉伸后PBPCS螺旋状的大分子主链处于更为伸直的构象,因此分子主链产生一定的内应力,即形变回复应力.由此可见,PBPCS相对柔性的聚乙烯主链使纤维具有良好的形变回复性能,而侧基的甲壳效应使得纤维能够保持初始尺寸,即PBPCS所具有的类似弹簧的特殊螺旋状分子结构是其纤维具有形状记忆效应的内在原因. 相似文献