全文获取类型
收费全文 | 196篇 |
免费 | 11篇 |
国内免费 | 8篇 |
专业分类
化学 | 156篇 |
综合类 | 8篇 |
数学 | 2篇 |
物理学 | 49篇 |
出版年
2023年 | 5篇 |
2022年 | 35篇 |
2021年 | 13篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 11篇 |
2016年 | 4篇 |
2015年 | 10篇 |
2014年 | 2篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 3篇 |
2010年 | 6篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 2篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 5篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有215条查询结果,搜索用时 15 毫秒
161.
ZhongJunMA IsaoFUJII YutakaEBIZUKA XianLI 《中国化学快报》2004,15(1):58-60
Two novel compounds, named sphaerophyside SC and SD were isolated from the ethanolic extract of the seeds of Sphaerophysa salsula. The structures of the compounds were elucidated on the basis of the NMR data, especially the 2D NMR technique. 相似文献
162.
In this study, essential oils from Voacanga africana seeds at different extraction stages were investigated. In the chemical composition analysis, 27 compounds representing 86.69–95.03% of the total essential oils were identified and quantified. The main constituents in essential oils were terpenoids, alcohols and fatty acids accounting for 15.03–24.36%, 21.57–34.43% and 33.06–57.37%, respectively. Moreover, the analysis also revealed that essential oils from different extraction stages possessed different chemical compositions. In the antioxidant evaluation, all analysed oils showed similar antioxidant behaviours, and the concentrations of essential oils providing 50% inhibition of DPPH-scavenging activity (IC50) were about 25 mg/mL. In the antimicrobial experiments, essential oils from different extraction stages exhibited different antimicrobial activities. The antimicrobial activity of oils was affected by extraction stages. By controlling extraction stages, it is promising to obtain essential oils with desired antimicrobial activities. 相似文献
163.
A. Zielenkiewicz 《Journal of Thermal Analysis and Calorimetry》1995,45(4):811-821
The results of calorimetric studies of 5SrRNA solutions isolated from lupin seeds in the pressence of the ClO 4 ? , NO 3 ? , Br 4 ? , SO 4 2? , Cl?, COO? (maleic and fumaric acids) anions were reported. The plots of calorimetric curves, enthalpy of conformational changes of two state transitions were presented. Using the deconvolution method proposed by Freire and Biltonen the elementary transitions were distinguished and discussed. 相似文献
164.
应用Agilent GC 6890气相色谱仪(附FPD检测器)对13种残留于西兰花中的有机含磷农药(OPP′s)在4种不同极性的毛细管色谱柱(即DB-1、DB-5、DB-1701及DB-35MS)上的保留行为作了研究。结果表明:采用由DB-5及DB-1701串联组成的色谱柱单元,西兰花中13种残留OPP′s可达到有效分离和测定。 相似文献
165.
Sulforaphane is a cognate isothiocyanate of glucoraphanin, released by degradation of glucosinolate through myrosinase enzyme, when Brassica tissues are crushed or chewed. C8 analytical column and mixture of water/acetonitrile 65/35 (ν/ν) as mobile phase were used to separate sulforaphane in broccoli tissues (e.g., 7‐day‐seedling, seed, floret and leave). Confirmation of sulforaphane in crude extract of broccoli tissues was monitored using gas chromatography‐mass spectroscopy (GC‐MS). The highest amount of sulforaphane (1216 μg/g dry weight) found in 7‐day‐seedling. This method is suitable for routine screening of plant materials and proposes a low cost and robust technique for the analysis of sulforaphane. 相似文献
166.
Barbara Mazurek Magdalena Wjciak Dorota Kostrzewa Magorzata Kondracka 《Molecules (Basel, Switzerland)》2022,27(24)
Supercritical fluid extraction is a powerful analytical tool and it is willingly used by researchers for the isolation of various components from different matrices. In our study, the carbon dioxide in the supercritical state was used for the extraction of oils from blackcurrant and black cumin seeds. To determine the optimal conditions for the process (temperature, pressure and time), the method of statistical experiment planning and the Box–Behnken design was applied and the yield of the oils and the content of fatty acids (FAs) were taken into consideration. It has been found that an increase in pressure causes an increase in extraction yield (W), and an increase in temperature, both at constant pressure and time, does not significantly change the yield value. Optimal yield values were obtained for both materials under almost similar extraction parameters: 306 bar/ 43 min/ 50 °C (blackcurrant) and 282 bar/ 40 min/ 50 °C (black cumin). The influence of the above parameters (T, p, t) on the content of FAs in the extracts has a slightly different trend. The use of supercritical carbon dioxide for the extraction of blackcurrant and black cumin seeds allowed for high process yield and high-quality, rich in polyunsaturated fatty acids oils which can be used as a substrate or final product for industry. 相似文献
167.
Lupinus albus L. (lupine) is a legume whose grain/seed has gained increasing interest. Its recognized nutritional properties, namely a high content of protein, dietary fiber and its low fat content, make lupine a suitable alternative not only for animal protein, but also as a substitute for more processed and less balanced flours from a nutritional point of view, used in the preparation of bread, cakes and cookies, among others. In addition, its nutritional and bioactive compounds have potential benefits for human health in the prevention and treatment of some diseases. However, the existence of some anti-nutritional compounds and contaminants reveal some concern, requiring effective methods for their detection and eventual removal. This review intends to address the potential of lupine (L. albus) in food and human health and to balance the pros and cons. Nutritional and anti-nutritional components of L. albus seeds and possible contaminants of lupine seeds are examined. The potential health benefits of lupine (seeds), including energy metabolism, cardiovascular diseases, hypertension, glucose and insulin metabolism, bower function and anticonvulsant action, are discussed based on scientific evidence (both clinical trials and studies performed with animal models). 相似文献
168.
Venelina Popova Zhana Petkova Nadezhda Mazova Tanya Ivanova Nadezhda Petkova Magdalena Stoyanova Albena Stoyanova Sezai Ercisli Zuhal Okcu Sona Skrovankova Jiri Mlcek 《Molecules (Basel, Switzerland)》2022,27(18)
In recent years there has been an extensive search for nature-based products with functional potential. All structural parts of Physalis alkekengi (bladder cherry), including fruits, pulp, and less-explored parts, such as seeds and peel, can be considered sources of functional macro- and micronutrients, bioactive compounds, such as vitamins, minerals, polyphenols, and polyunsaturated fatty acids, and dietetic fiber. The chemical composition of all fruit structural parts (seeds, peel, and pulp) of two phenotypes of P. alkekengi were studied. The seeds were found to be a rich source of oil, yielding 14–17%, with abundant amounts of unsaturated fatty acids (over 88%) and tocopherols, or vitamin E (up to 5378 mg/kg dw; dry weight). The predominant fatty acid in the seed oils was linoleic acid, followed by oleic acid. The seeds contained most of the fruit’s protein (16–19% dw) and fiber (6–8% dw). The peel oil differed significantly from the seed oil in fatty acid and tocopherol composition. Seed cakes, the waste after oil extraction, contained arginine and aspartic acid as the main amino acids; valine, phenylalanine, threonine, and isoleucine were present in slightly higher amounts than the other essential amino acids. They were also rich in key minerals, such as K, Mg, Fe, and Zn. From the peel and pulp fractions were extracted fruit concretes, aromatic products with specific fragrance profiles, of which volatile compositions (GC-MS) were identified. The major volatiles in peel and pulp concretes were β-linalool, α-pinene, and γ-terpinene. The results from the investigation substantiated the potential of all the studied fruit structures as new sources of bioactive compounds that could be used as prospective sources in human and animal nutrition, while the aroma-active compounds in the concretes supported the plant’s potential in perfumery and cosmetics. 相似文献
169.
Kokoette Bassey Malebelo Mabowe Mmamosheledi Mothibe Bwalya A. Witika 《Molecules (Basel, Switzerland)》2022,27(18)
Moringa oleifera Lam (syn. M. ptreygosperma Gaertn.) leaves are globally acclaimed for their nutritional content and mitigation of malnutrition. In most impoverished rural communities including Limpopo, Mpumalanga and KwaZulu Natal of South Africa, powdered leaves of Moringa oleifera are applied as a nutritional supplement for readily available food such as porridge for malnourished children and even breast-feeding mothers. Widely practiced and admired is also the use of the plant seed in the do-it-yourself purification of water by rural South Africans. This study aimed at identifying the chemical and nutritional marker compounds present in South African Moringa oleifera seed oils using high resolution 1-2-dimension gas chromatography in order to give scientific validation to its uses in cosmetics and particularly in culinary practices. Results obtained from two-dimension tandem mass spectrometry chemical signature revealed over 250 compounds, five times more than those reported from one-dimension gas chromatography. Whereas previous reports from gas chromatography-mass spectrometry analysis reported oleic acid (70–78%) as the major compound from oil samples from other countries, M. oleifera seed oil from South Africa is marked by cis-13-octadeaconic acid with 78.62% and 41.9% as the predominant monounsaturated fatty acid in the hexane and dichloromethane extracts respectively. This was followed by cis-vaccenic acid, an isomer of oleic acid at 51% in the acetone extract, 9-octadecanoic acid-(z)-methyl ester at 39.18%, 21.34% and 10.06% in dichloromethane, hexane and acetone extracts respectively. However, a principal component analysis with R2 = 0.98 of the two-dimension tandem mass spectrometry cum chemometric analysis indicated n-hexadecanoic acid, oleic acid, 9-octadecanoic acid-(z)-methyl ester and cis-vaccenic acid with a probability of 0.96, 0.88, 0.80 and 0.79 respectively as the marker compounds that should be used for the quality control of moringa seed oils from South Africa. This study demonstrates that South African Moringa oleifera oils contain C-18 monounsaturated fatty acids similar to oils from Egypt (76.2%), Thailand (71.6%) and Pakistan (78.5%) just to mention but a few. These fatty acids are sunflower and olive oil type-compounds and therefore place moringa seed oil for consideration as a cooking oil amongst its other uses. 相似文献
170.
Acylglycerides present in oil seeds and meat can be transformed into volatile fatty esters using chlorotrimethylsilane (CTMS) and 1-pentanol as reagents. The volatile esters can then be analysed by GC. The method is quantitative and involves only minor sample manipulation. It often permits major recoveries of the total saponifiable lipids present in solid samples. A 40 min reaction time is enough to ensure the total conversion of saponifiable lipids to the corresponding FAPEs. 相似文献