全文获取类型
收费全文 | 349篇 |
免费 | 22篇 |
国内免费 | 8篇 |
专业分类
379篇 |
出版年
2023年 | 11篇 |
2022年 | 12篇 |
2021年 | 15篇 |
2020年 | 15篇 |
2019年 | 31篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 37篇 |
2012年 | 20篇 |
2011年 | 15篇 |
2010年 | 8篇 |
2009年 | 5篇 |
2008年 | 11篇 |
2007年 | 19篇 |
2006年 | 11篇 |
2005年 | 6篇 |
2004年 | 11篇 |
2003年 | 12篇 |
2002年 | 7篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
排序方式: 共有379条查询结果,搜索用时 15 毫秒
11.
12.
Manuele Gori Sara Maria Giannitelli Andrea Zancla Pamela Mozetic Marcella Trombetta Nicol Merendino Alberto Rainer 《Biotechnology and bioengineering》2021,118(1):142-152
Organs‐on‐chip (OoCs) are catching on as a promising and valuable alternative to animal models, in line with the 3Rs initiative. OoCs enable the creation of three‐dimensional (3D) tissue microenvironments with physiological and pathological relevance at unparalleled precision and complexity, offering new opportunities to model human diseases and to test the potential therapeutic effect of drugs, while overcoming the limited predictive accuracy of conventional 2D culture systems. Here, we present a liver‐on‐a‐chip model to investigate the effects of two naturally occurring polyphenols, namely quercetin and hydroxytyrosol, on nonalcoholic fatty liver disease (NAFLD) using a high‐content analysis readout methodology. NAFLD is currently the most common form of chronic liver disease; however, its complex pathogenesis is still far from being elucidated, and no definitive treatment has been established so far. In our experiments, we observed that both polyphenols seem to restrain the progression of the free fatty acid‐induced hepatocellular steatosis, showing a cytoprotective effect due to their antioxidant and lipid‐lowering properties. In conclusion, the findings of the present work could guide novel strategies to contrast the onset and progression of NAFLD. 相似文献
13.
R. Tognetti A. Morales-Sillero R. D'Andria J. E. Fernández A. Lavini L. Sebastiani 《Plant biosystems》2013,147(1):138-148
Abstract The response of mature olive (Olea europaea L.) trees to both regulated deficit irrigation and fertigation was studied for some consecutive years in sub-humid (Italy) and semi-arid conditions (Spain). All cultivars tested in these experiments were preferentially for table olive consumption (pickling and double-aptitude). Data from these long-term studies on field-grown, mature trees are summarized for assessing common effects of water and nutrient supply on plant behaviour and fruit yield. Seasonal yield variations were observed, and showed that the effect of irrigation treatments was somewhat more gradual in the “on” than in the “off” year. Differences amongst cultivars were always marked. Dry matter accumulation in pulp and pit was positively affected by progressively increasing the amount of water supplied to plants, regardless of years and cultivars. The ratio between pulp and pit fresh weight was negatively affected by irrigation, while fruit size was positively influenced by the gradual increase of irrigation water. Average nitrogen levels in leaves were generally above the deficiency threshold at both experimental plantations. Crop yield was not consistently increased by addition of soil nutrients. The effect of fertigation treatments was relatively uninfluential on oil accumulation in fruits. However, polyphenols in oil samples decreased progressively as the addition of nutrients increased. Critical aspects and strategic decisions in modern olive growing are the selection of cultivar, the supply of water, the option of fertilization, together with other orchard management practices. In this paper we outline various aspects of long-term studies in experimental olive plantations with the aim of highlighting inter-regulatory processes, involving plant growth and crop yield, which must be taken into account when planning future field research and modelling exercises. 相似文献
14.
Prakash Maran Jeganathan Sivakumar Venkatachalam Thirugnanasambandham Karichappan Sridar Ramasamy 《Preparative biochemistry & biotechnology》2013,43(1):56-67
The objective of the present study is to find out the optimum extraction conditions for extraction of polyphenols from red grapes using Box–Behnken design. Red grapes polyphenols were extracted using acid–ethanol solvent at various extraction temperature (40–60°C), extraction time (20–100 min) and different solid–liquid ratio (1:5–1:15 g:ml). The effect (main and interactive) of extraction conditions on total anthocyanin, phenolic and flavonoid content were studied using Box–Behnken design (three factors at three levels). The results showed that the contribution of the quadratic model was significant for all the responses. Second-order mathematical regression models were developed and were found to fit well with observed data. Derringer's desirability function methodology was performed to find out the optimal conditions based on both individual and combinations of all responses (extraction temperature: 57°C, time: 61 min, and solid–liquid ratio: 1:8.7 g:ml) were established. At this optimal condition, the anthocyanin yield, total phenolic and flavonoid content were 73.92 mg/100 g, 221.4 mg GAE/100 g, and 79.08 mg CE/100 g, respectively. A desirability value of 0.902 was achieved at this point. 相似文献
15.
AbstractThis study aimed to evaluate the effects of tea extracts on oral biofilm colonization depending on steeping temperature. S. mutans and S. sobrinus were cultured and treated with green or black tea extracts prepared under different steeping conditions. Biofilm formation, glucosyltransferase (GTF) levels, bacterial growth, and acidogenicity were evaluated. Biofilms were also assessed by gas chromatography-mass spectrometry and confocal laser scanning microscopy. All extracts with hot steeping showed higher inhibitory effects on biofilm formation and cell viability and lower GTF levels compared with those with cold steeping (p?<?0.05). Hot steeping significantly reduced bacterial growth (p?<?0.05) and maintained the pH. Catechins were only identified from hot steeping extracts. Within the limits of this study, extracts with cold steeping showed lower inhibitory effects on oral biofilms. The different effects between steeping extracts may be attributed to the difference in catechins released from tea extracts under the different steep conditions. 相似文献
16.
Fadwa Chaabane Aline Pinon Alain Simon Kamel Ghedira Leila Chekir-Ghedira 《Cell biochemistry and function》2013,31(6):460-467
In this study, we have investigated inhibitory capacity of ethyl acetate, total oligomer flavonoid (TOF), aqueous extracts and beta amyrin acetate, a triterpene isolated from ethyl acetate extract obtained from leaves of Daphne gnidium, on mouse melanoma (B16-F0 and B16-F10 cells) proliferation. Influence of these products on percentage cell distribution in cycle phases and melanogenesis was also studied. Cell viability was determined using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and flow cytometry was used to analyse effects of tested compounds on progression through the cell cycle. In addition, amounts of melanin and tyrosinase were measured spectrophotometrically at 475 nm. Ethyl acetate, TOF and aqueous extracts exhibited significant anti-proliferative activity after incubation with the two types of tumour skin cells B16-F0 and B16-F10. Furthermore, cell cycle analysis revealed that cells treated with ethyl acetate and TOF extracts were arrested predominantly in G2-M phase. Ethyl acetate extract has also the ability to enhance melanogenesis and tyrosinase activity of B16-F0 melanoma cells. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
17.
18.
Masaaki Kuwahara Takashi Tachiki Tatsurokuro Tochikura Koichi Ogata 《Bioscience, biotechnology, and biochemistry》2013,77(5):745-754
Distribution of NAD phosphorylating reactions, phosphorylation through NAD kinase and phosphotransferase, was investigated. NAD kinase activity was distributed rather widely in bacteria, whereas phosphotransferase activity with p-NPP and NAD was limited to a few genera. Proteus mirabilis showed strong activity of phosphotransferase besides NAD kinase activity.Partial purification of the phosphotransferase was attempted. The enzyme preparation possessed phosphatase activity as well as phosphotransferase activity. Phosphorylation of NAD proceeded maximally under the conditions below pH 4.0. Cu2+ showed stimulating effect on the activity. Besides p-NPP and phenylphosphate, various nucleotides, especially 2′ (or 3′) isomers, served as excellent phosphoryl donors, and various kinds of nucleosides and nucleotides were phosphorylated to form nucleoside monophosphates and nucleoside diphosphates. 相似文献
19.
Masao Fujimoto Akira Kuninaka Hiroshi Yoshino 《Bioscience, biotechnology, and biochemistry》2013,77(7):1111-1119
Nuclease P1 from Penicillium citrinum was found to be produced in a form of complex with malonogalactan (a galactan, 1, 5-β-galactofuranoside polymer esterfied with malonic acid at position 3) in the culture on wheat bran. Neither nuclease P1-malonogalactan complex nor malonogalactan was produced in a liquid medium. Nuclease P1-malonogalactan complexes, P1-MG I, II, and III were purified from an aqueous extract of the culture on wheat bran. The most anionic complex, P1-MG III, was composed of the protein, carbohydrate and malonic acid in the ratio of 1: 2.6: 0.5 (w/w). The complex was not dissociated by purification procedures including fractionations with acetone and ammonium sulfate, gel filtration and DEAE-cellulose chromatography. A malonogalactan-specific carboxylesterase was found in culture of the same mold on wheat bran. Nuclease P1-malonogalactan was demalonylated by the esterase to yield nuclease P1-galactan. The binding of nuclease P1 to galactan was rather loose so that nuclease P1-galactan complex was partially dissociated by DEAE-cellulose chromatography. Attempt to reconstitute the complex from nuclease P1 and malonogalactan upon mixing was unsuccessful. Exogenously supplemented nuclease P1 did not associate with malonogalactan in the growing culture on wheat bran, either.Several extracellular enzymes such as RNase, β-galactosidase and protease were also found in a form of complex with malonogalactan in the culture on wheat bran. 相似文献
20.
Yanping Zhou Zhongliang Jiang Haiying Lu Zhuyu Xu Rongsheng Tong Jianyou Shi Guiqing Jia 《化学与生物多样性》2019,16(11)
The Keap1‐Nrf2/ARE signaling pathway is an important defense system against exogenous and endogenous oxidative stress injury. The dysregulation of the signaling pathway is associated with many diseases, such as cancer, diabetes, and respiratory diseases. Over the years, a wide range of natural products has provided sufficient resources for the discovery of potential therapeutic drugs. Among them, polyphenols possess Nrf2 activation, not only inhibit the production of ROS, inhibit Keap1‐Nrf2 protein–protein interaction, but also degrade Keap1 and regulate the Nrf2 related pathway. In fact, with the continuous improvement of natural polyphenols separation and purification technology and further studies on the Keap1‐Nrf2 molecular mechanism, more and more natural polyphenols monomer components of Nrf2 activators have been gradually discovered. In this view, we summarize the research status of natural polyphenols that have been found with apparent Nrf2 activation and their action modes. On the whole, this review may guide the design of novel Keap1‐Nrf2 activator. 相似文献