全文获取类型
收费全文 | 197篇 |
免费 | 6篇 |
国内免费 | 6篇 |
专业分类
化学 | 138篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 40篇 |
物理学 | 22篇 |
出版年
2022年 | 11篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 8篇 |
2012年 | 13篇 |
2011年 | 12篇 |
2010年 | 14篇 |
2009年 | 9篇 |
2008年 | 3篇 |
2007年 | 8篇 |
2006年 | 12篇 |
2005年 | 7篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1959年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有209条查询结果,搜索用时 0 毫秒
1.
Kesheng Feng Farah Mahdavi-Anary Richard E. Partch Yuzhuo Li 《Photochemistry and photobiology》1995,62(5):813-817
Abstract— Photochemical reactions of 6-azidocoumarin and 7-azido-4-methylcoumarin in the presence of secondary amines have been investigated for their potential applications in photoaffinity labeling. It was found that the singlet nitrene generated from 6-azidocoumarin isomerized to a dehydroazepine intermediate that reacted with an amine to yield two isomeric adducts. Photolysis of 7-azido-4-meth-ylcoumarin, in contrast, gave a triplet nitrene that abstracted hydrogen atoms from secondary amine molecules to form 7-amino-4-methylcoumarin as the major product. The difference in the intersystem crossing rate between the two compounds originates from the azido position relative to the carbonyl group. Because of its ability to form a covalent linkage with a nucleophile, 6-azidocoumarin is deemed to have a greater potential as a photoaffinity label than 7-azido-4-methylcoumarin. 相似文献
2.
3.
I. S. El-Yamani M. Y. Farah E. N. Abd El-Messieh 《Journal of Radioanalytical and Nuclear Chemistry》1978,45(1):147-153
The distribution of Be between aqueous HCl solutions and organic phases of di-(2-ethyl hexyl)-phosphoric acid, has been described. The dependence of extraction on aqueous acidity, metal and extractant concentration as also on the diluent type, was thoroughly examined. The possible mechanism of extraction has been discussed in the light of results obtained. 相似文献
4.
Farah Diab Hawraa Zbeeb Francesca Baldini Piero Portincasa Mohamad Khalil Laura Vergani 《Molecules (Basel, Switzerland)》2022,27(15)
Numerous plants, plant extracts, and plant-derived compounds are being explored for their beneficial effects against overweight and liver diseases. Obesity is associated with the increased prevalence of non-alcoholic fatty liver disease (NAFLD), becoming the most common liver disease in Western countries. Obesity and NAFLD are closely associated with many other metabolic alternations such as insulin resistance, diabetes mellitus, and cardiovascular diseases. Many herbs of the Lamiaceae family are widely employed as food and spices in the Mediterranean area, but also in folk medicine, and their use for the management of metabolic disorders is well documented. Hereby, we summarized the scientific results of the medicinal and nutraceutical potential of plants from the Lamiaceae family for prevention and mitigation of overweight and fatty liver. The evidence indicates that Lamiaceae plants may be a cost-effective source of nutraceuticals and/or phytochemicals to be used in the management of metabolic-related conditions such as obesity and NAFLD. PubMed, Google Scholar, Scopus, and SciFinder were accessed to collect data on traditional medicinal plants, compounds derived from plants, their reported anti-obesity mechanisms, and therapeutic targets. 相似文献
5.
Malik Abdul Rub Dileep Kumar Naved Azum Farah Khan Abdullah M. Asiri 《Journal of solution chemistry》2014,43(5):930-949
In the present paper, the micellization of an amphiphilic drug, promazine hydrochloride, and gemini surfactants (16-s-16) with s = 4–6 and the monomeric hexadecyltrimethylammonium bromide (CTAB) counterparts has been examined conductometrically in the pure and mixed states in aqueous solutions at different compositions and temperatures (298.15–308.15 K). Dicationic gemini surfactants provide much better environment for the micellization behavior than the corresponding monocationic counterpart CTAB. The critical micelle concentration (cmc) values are lower than the cmc for ideal mixing, cmc id, suggesting attractive interactions between the two components in mixed micelles. The micellar mole fractions of surfactants, evaluated by different models, show greater contributions of surfactants in mixed micelles and increase with increasing concentrations of these surfactants. The negative values of β suggest synergism in the mixtures, which is highly beneficial as it reduces the total amount of surfactants required in a particular application, leading to reductions of cost and environmental impact. Activity coefficients (f 1 and f 2) are always less than unity showing nonideality in the systems. The data have been also used for evaluation of thermodynamic parameters. 相似文献
6.
7.
Shady Farah Oren Aviv Natalia Laout Stanislav Ratner Nurit Beyth Abraham J. Domb 《先进技术聚合物》2014,25(6):689-692
Silica particles functionalized with quaternary ammonium groups were prepared by interpenetrating polyethylenimine (PEI) into silica particles and crosslinking with diiodopentane, followed by octyliodide alkylation and methyliodide quaternarization (S‐QA‐PEI). The synthesized S‐QA‐PEI particles were identified with a slight particle size increase of 2–3 µm. Different ratios of PEI:silica particles were prepared and analyzed. While silica particles are negatively charged, ?16.7 ± 5.11 mV, the prepared S‐QA‐PEI particles are positively charged, +50–60 mV. These particles were embedded in poly(ethylene vinyl acetate) and poly(ethylene methacrylic acid) coatings which exhibited strong antibacterial activity. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
Siti Farah Nadiah Rusli Siti Mariam Daud Mimi Hani Abu Bakar Kee Shyuan Loh Mohd Shahbudin Masdar 《Molecules (Basel, Switzerland)》2022,27(3)
The biocathode in a microbial fuel cell (MFC) system is a promising and a cheap alternative method to improve cathode reaction performance. This study aims to identify the effect of the electrode combination between non-chemical modified stainless steel (SS) and graphite fibre brush (GFB) for constructing bio-electrodes in an MFC. In this study, the MFC had two chambers, separated by a cation exchange membrane, and underwent a total of four different treatments with different electrode arrangements (anodeǁcathode)—SSǁSS (control), GFBǁSS, GFBǁGFB and SSǁGFB. Both electrodes were heat-treated to improve surface oxidation. On the 20th day of the operation, the GFBǁGFB arrangement generated the highest power density, up to 3.03 W/m3 (177 A/m3), followed by the SSǁGFB (0.0106 W/m3, 0.412 A/m3), the GFBǁSS (0.0283 W/m3, 17.1 A/m3), and the SSǁSS arrangements (0.0069 W/m−3, 1.64 A/m3). The GFBǁGFB had the lowest internal resistance (0.2 kΩ), corresponding to the highest power output. The other electrode arrangements, SSǁGFB, GFBǁSS, and SSǁSS, showed very high internal resistance (82 kΩ, 2.1 kΩ and 18 kΩ, respectively) due to the low proton and electron movement activity in the MFC systems. The results show that GFB materials can be used as anode and cathode in a fully biotic MFC system. 相似文献
9.
Farah Noun John Manioudakis Rafik Naccache 《Particle & Particle Systems Characterization》2020,37(8):2000119
Carbon dots possess versatile optical properties that have prompted their investigation in applications including photocatalysis, photovoltaics, imaging, and drug delivery, among others. However, the preparation of these nanodots is accompanied by the formation of fluorophores and intermediates, which can be difficult to separate. In the absence of thorough purification protocols, the reported optical properties are often heterogeneous, which hinders understanding of their physicochemical and optical properties and concrete application development. Here, two hydrophilic carbon dot systems starting with citric acid and diethylenetriamine are prepared. The impact of purification, including dialysis, ultrafiltration, and organic washes, on the properties of the dots is demonstrated. It is shown that monitoring the purification endpoint using near-infrared, fluorescence, and absorbance spectroscopies is possible. Moreover, it is demonstrated that fluorescence quantum yields can be a reliable tool to determine the purification endpoint. This work shows that even carbon dots derived from the same chemical precursors can have different purification profiles and purification requirements. However, the developed approach can be used to determine the proper purification procedure and endpoint for any carbon dot system regardless of the starting materials. Finally, it is envisioned that this work can be easily extended toward the purification of other hydrophilic nanomaterials. 相似文献
10.
Farah Naz Bibimaryam Mousavi Zhixiong Luo Christia Jabbour Philippe M. Heynderickx Somboon Chaemchuen Francis Verpoort 《应用有机金属化学》2019,33(5)
A series of spray dried zeolitic imidazolate frameworks (ZIFs = ZIF‐8, ZIF‐67, and Zn/Co‐ZIF) are used as a catalyst for the bulk ring‐opening polymerization of δ‐valerolactone without any co‐catalyst to generate polyvalerolactone. Interestingly, using the same catalyst under the same reaction conditions could manipulate the structure of the product polymer, and thus its physical properties. Thus, using a dried substrate leads to the formation of the cyclic polymer while a linear polymer was formed on using the commercially available substrate. An activated monomer mechanism has been suggested where the propagating zinc alkoxide undergoes an intramolecular transesterification to release cyclic or linear polyvalerolactone. The ROP of δ‐VL without drying shows that the polymeric zwitterions have little tendency to cyclize in the presence of moisture. At 140 °C, ZIF‐8 shows a superior catalytic activity resulting in the production of cyclic polyvalerolactone having a high molecular weight as compared to ZIF‐67 or Zn/Co‐ZIF due to the presence of highly active sites. The catalyst could be recycled and reused without any significant loss of catalytic activity. 相似文献