全文获取类型
收费全文 | 174篇 |
免费 | 8篇 |
国内免费 | 33篇 |
专业分类
化学 | 190篇 |
物理学 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 7篇 |
2018年 | 1篇 |
2017年 | 6篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 6篇 |
2013年 | 8篇 |
2012年 | 18篇 |
2011年 | 8篇 |
2010年 | 9篇 |
2009年 | 14篇 |
2008年 | 8篇 |
2007年 | 7篇 |
2006年 | 5篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有215条查询结果,搜索用时 281 毫秒
91.
《Arabian Journal of Chemistry》2022,15(10):104135
Justicia vahlii Roth. (acanthaceae) is an important medicinal food plant used in pain relief and topical inflammation. The present study aimed to evaluate phytochemical composition, toxicity, anti-inflammatory, antioxidant and enzyme inhibition potential of n-butanol extract of J. vahlii (BEJv). The extract prepared through maceration was found rich in total phenolic contents (TPC) 196.08 ± 6.01 mg of Gallic acid equivalent (mg GAE/g DE) and total flavonoid contents (TFC) 59.08 ± 1.32 mg of Rutin equivalent (mg RE/g DE). The UPLC-Q-TOF-MS analysis of BEJv showed tentative identification of 87 compounds and 19 compounds were detected in GC–MS analysis. The HPLC-PDA quantification showed the presence of 14 polyphenols amongst which kaempferol (3.45 ± 0.21 µg/ mL DE) and ferulic acid (2.31 ± 1.30 µg/ mL DE) were found in highest quantity. The acute oral toxicity study revealed the safety and biocompatibility of the extract up to 3000 mg/kg in mice. There was no effect of BEJv on human normal liver cells (HL 7702) and very low cytotoxic effect on liver cancer cells (HepG2) and breast cancer cells (MCF-7). In anti-inflammatory evaluation, the BEJv treated groups showed significant inhibition (p < 0.001) of late phase carrageenan induced paw edema at 400 mg/kg and increased the levels of oxidative stress markers; catalase, superoxide dismutase (SOD) and glutathione (GSH) while decreased the inflammatory markers; interleukin-1beta (IL-β) and tumor necrosis factor alpha (TNF-α) in paw tissue of mice. BEJv displayed highest results in Ferric reducing antioxidant power (FRAP) assay 97. 21 ± 2.34 mg TE (trolox equivalent)/g DE, and highest activity 3.32 ± 0.31 mmol ACAE (acarbose equivalent)/g D.E against α-glucosidase. Docking study showed good docking score by the tested compounds against the various clinically significant enzymes. Conclusively the current study unveiled J. vahlii as novel non-toxic source with good antioxidant-mediated anti-inflammatory potential which strongly back the traditional use of the species in pain and inflammation. 相似文献
92.
Ping-Jyun Sung Chen-Hao Pai Yin-Di Su Tsong-Long Hwang Tung-Yung Fan Jan-Jung Li 《Tetrahedron》2008,64(19):4224-4232
Four new 8-hydroxybriarane diterpenoids, including junceols A-C (1-3) and fragilide D (4), have been isolated from the gorgonian corals Junceella juncea and Junceella fragilis, respectively. The structures of briaranes 1-4 were elucidated by the interpretations of spectral data analysis. Briaranes 1-3 have displayed inhibitory effects on superoxide anion generation by human neutrophils. 相似文献
93.
Xiangling Ren Mingqian Wang Xing He Zheng Li Jing Zhang Wei Zhang Xudong Chen Hong Ren Xianwei Meng 《中国化学快报》2018,29(12):1865-1868
The Mn-doped ZnS QDs were synthesized by a facile and one-pot method and possess intrinsic superoxide dismutase-like activity. 相似文献
94.
溶剂化对修饰超氧化物歧化酶稳定性的影响 总被引:1,自引:0,他引:1
静电作用是影响生物大分子稳定性的重要因素.通过突变或化学修饰方法,引入或屏蔽掉酶的可电离残基的电行而合理改变酶分子电场,是对蛋白质进行分子设计、提高酶稳定性的一个可行方法.铜锌超氧化物歧化酶(Cu,ZnSOD)是专一清除超氧阴离子自由基O的金属酶[1],具有重要药用价 相似文献
95.
Krylov AV Beissenhirtz M Adamzig H Scheller FW Lisdat F 《Analytical and bioanalytical chemistry》2004,378(5):1327-1330
Cytochrome c was immobilized on screen-printed thick-film gold electrodes by a self-assembly approach using mixed monolayers of mercaptoundecanoic acid and mercaptoundecanol. Cyclic voltammetry revealed quasi-reversible electrochemical behavior of the covalently fixed protein with a formal potential of +10 mV vs. Ag/AgCl. Polarized at +150 mV vs. Ag/AgCl the electrode was found to be sensitive to superoxide radicals in the range 300–1200 nmol L–1. Compared with metal needle electrodes sensitivity and reproducibility could be improved and combined with the easiness of preparation. This allows the fabrication of disposable sensors for nanomolar superoxide concentrations. By changing the electrode potential the sensor can be switched from response to superoxide radicals to hydrogen peroxide—another reactive oxygen species. H2O2 sensitivity can be provided in the range 10–1000 mol L–1 which makes the electrode suitable for oxidative stress studies. 相似文献
96.
This paper illustrates the various aspects of the reactivity of the Cu(II)–Cu(I) system in biological systems, with one example of an enzymatic reaction in which Cu(II) alone is oxidizing enough to carry out the reaction (superoxide dismutase), one example in which a Cu(II)-bound peroxo intermediate is the active species (tyrosinase) and the examples of galactose oxidase and copper amine oxidases in which Cu(II) is associated with a redox active organic cofactor. In some cases, we will show some illustrations of biomimetic approaches developed in our laboratories, aimed at a better understanding of reaction mechanisms and at an original design of new catalysts with potential applications in synthetic chemistry. Some comments are given concerning the respective features of copper and iron. 相似文献
97.
Eric D. Bloch Wendy L. Queen Matthew R. Hudson Jarad A. Mason Dianne J. Xiao Leslie J. Murray Roxana Flacau Craig M. Brown Jeffrey R. Long 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(30):8747-8751
A chromium(II)‐based metal–organic framework Cr3[(Cr4Cl)3(BTT)8]2 (Cr‐BTT; BTT3−=1,3,5‐benzenetristetrazolate), featuring coordinatively unsaturated, redox‐active Cr2+ cation sites, was synthesized and investigated for potential applications in H2 storage and O2 production. Low‐pressure H2 adsorption and neutron powder diffraction experiments reveal moderately strong Cr–H2 interactions, in line with results from previously reported M‐BTT frameworks. Notably, gas adsorption measurements also reveal excellent O2/N2 selectivity with substantial O2 reversibility at room temperature, based on selective electron transfer to form CrIII superoxide moieties. Infrared spectroscopy and powder neutron diffraction experiments were used to confirm this mechanism of selective O2 binding. 相似文献
98.
HE Xiao-hong WU Min LI Shan-yu CHU Yu-zhuo CHEN Jia LIU Lan-ying 《高等学校化学研究》2005,21(5):562-565
The amino acid composition of the superoxide dismutase(SOD) from camellia pollen was measured and the tryptophan(Trp) residues were modified by using N-bromosuccinimide(NBS). The results show that there are 21 Trp residues in an SOD molecule and seven of which are located on the surface of the enzyme. By researching the fluorescence spectra of the native SOD and the modified SOD, we have found that the emission wavelength of Trp is at 335 nm and the fluorescence intensity will decrease when the enzyme is modified. The results also show that potassium iodide(KI) can significantly quench the fluorescence of the native SOD, but it has a less pronounced effect on the modified enzyme. Glycerin as a surface activation reagent can stabilize the fluorescence of the modified enzyme. 相似文献
99.
Xanthine oxidase (XOD) inhibitors and superoxide anion scavengers play an important role in the treatment of gout and the inhibition of many diseases related to superoxide anion. The respective quantitation of uric acid and superoxide anion by traditional spectroscopic methods is routine in XOD inhibitors and superoxide anion scavengers screening at laboratories worldwide. In the present study, we established an ultrahigh performance liquid chromatography and triple quadrupole mass spectrometry (UHPLC–TQ-MS) method of higher accuracy and speed that combines screening of superoxide anion scavenger and XOD inhibitor in a single analysis by adding WST-1 (2-(4-iodophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium sodium salt) to the enzymatic reaction. We applied the established method to determine the XOD inhibitory activities and superoxide scavenging activities of some herbal extracts and compounds from natural products, which could be classified into six groups based on the results of the assay. Our innovative protocol is fast, accurate and robust. Moreover, it can eliminate false positive and false negative results which may occur in the traditional spectroscopic methods. 相似文献
100.
《Analytical letters》2012,45(13):2033-2043
Abstract Cytochrome c was immobilized at didodecyldimethylammonium bromide (DDAB)‐modified powder microelectrode and presented quasi‐reversible electrochemistry. The apparent surface coverage of cytochrome c is greatly enhanced by using powder microelectrode technique, which is 1.21×10?8 mol/cm2, more than one to three orders of magnitude larger than that obtained with thiol and DNA‐modified Au electrode. The cytochrome c modified powder microelectrode was applied for the amperometric determination of superoxide generated by the reaction of hypoxanthine with xanthine oxidase (XOD) in the presence of dioxygen. The detection sensitivity of the modified powder microelectrode is 0.74 µA/cm2 µM, which is larger than that reported in previous publications. The detection limit of the modified powder microelectrode (PME) is 0.5 µM, and the linear detection range is 0.86~5.93 µM (values of the concentration are all in terms of hypoxanthine concentration in the solution). 相似文献