首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   80篇
  免费   4篇
  84篇
  2022年   1篇
  2019年   2篇
  2018年   2篇
  2016年   3篇
  2015年   2篇
  2014年   2篇
  2013年   9篇
  2012年   9篇
  2011年   2篇
  2010年   4篇
  2009年   3篇
  2008年   5篇
  2007年   4篇
  2006年   5篇
  2005年   4篇
  2004年   2篇
  2003年   5篇
  2002年   5篇
  2001年   3篇
  2000年   1篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
  1994年   2篇
  1993年   1篇
  1991年   2篇
  1972年   1篇
排序方式: 共有84条查询结果,搜索用时 15 毫秒
11.
In this work, four nonionic surfactants based on sorbitan monolaurate (Span 20) were synthesized by introducing ethylene oxide gas (n?=?20, 40, 60, 80 ethylene oxide units) into Span 20 to give four new surfactants with different hydrophilic-lipophilic balance (HLB), namely, E(20), E(40), E(60), and E(80). The structures of the prepared nonionic surfactants were elucidated using Fourier-transform infrared (FT-IR) and (1)H-nuclear magnetic resonance (NMR) spectroscopy. The surface-tension measurements were recorded. The effects of the prepared nonionic surfactants on the simultaneous saccharification and fermentation (SSF) of microwave/alkali-pretreated rice straw to produce ethanol were investigated. From the obtained data, it was found that the addition of the nonionic surfactants at 2.5?g/L had a positive effect on SSF. The maximum ethanol yield (76 and 55%) was obtained after 72?hr for rice straw using Kluyveromyces marxianus and Saccharomyces cerevisiae, respectively. Also, it was found that the ethanol yield increases with increasing HLB of the prepared nonionic surfactants by increasing ethylene oxide units. The adsorption of nonionic surfactants on lignocelluloses is proposed to be due to hydrophobic and hydrogen bonding interactions between nonionic surfactants and the lignin part in the lignocelulose. It can be concluded that additions of surface-active compounds, such as nonionic surfactants, increase enzymatic conversion of rice straw for bioethanol purposes.  相似文献   
12.
Many theories of reflexology use ancient concepts which do not coincide with the modern medical terminology of anatomy, physiology and biophysics. This substantially reduces the trust of physicians in reflexology methods. During this research, several mathematical models for the interaction of the internal and biological active points of meridian structures have been proposed. The analysis of these models allows the specification of a list of heart diseases for which reflex diagnostics and reflex therapy methods are most effective and also allows increasing the effectiveness of these procedures. It is shown that good results for the prediction and early diagnosis of diseases from the reaction energy of biologically active points (acupuncture points) are obtained using fuzzy logic decision making.  相似文献   
13.
The reaction of the bis(triflates) 1,2-bis[2-(trifluoromethylsulfonyloxy)ethyl]benzene (1), 1,2-bis[3-(trifluoromethylsulfonyloxy)propyl]benzene (3) and 1,2-bis{2-[2-(trifluoromethylsulfonyloxy)ethyl]phenyl}ethane (6), respectively, with the carbonyl metalates [M(CO)4]2- (M=Os (a), Ru (b), Fe (c)) results in the formation of the osmaorthocyclophanes 2a, 4a, 7a and 8a, the ruthenacylophane 2b and the ferracyclophanes 2c and 7c, respectively. Carbon monoxide insertion into the Fe-Cσ bonds of the ferracycles 2c and 7c, respectively, affords the ketones 3-oxo[5]orthocyclophane (9) and 3-oxo[5.2]orthocyclophane (11). The structure of 2a was investigated by an X-ray structural analysis. 2a crystallizes in the monoclinic space group P21/n with Z=4.  相似文献   
14.
Transmission electron microscopy (TEM) is extremely useful for visualizing microglial, oligodendrocytic, astrocytic, and neuronal subcellular compartments (dendrite, dendritic spine, axon, axon terminal, perikaryon), as well as their intracellular organelles and cytoskeleton, in the central nervous system at high spatial resolution. Combined with TEM, pre-embedding immunocytochemistry allows the discrimination of cellular elements with few distinctive features and identification criteria (e.g., microglial perikarya and processes, when using an antibody against the microglia-specific marker Iba1 (ionized calcium binding adaptor molecule 1; as presented here)), identifying the neurotransmitter contents of cellular elements (e.g., serotonergic) and their ultrastructural localization of soluble or membrane-bound proteins (e.g., 5 HT1A and EphA4 receptors). Here, we describe a protocol for transcardiac perfusion of mice with acrolein fixative, removal and sectioning of the brain, as well as immunoperoxidase-diaminobenzidine (DAB) staining, resin embedding, and ultrathin sectioning of the brain sections. Upon completion of these procedures, the immunostained material is ready for examination with TEM. When rigorously performed, this technique provides an excellent compromise between optimal ultrastructural preservation and immunocytochemical detection.Download video file.(101M, mp4)  相似文献   
15.
16.
Pathogens isolated from fish appear to possess considerable antimicrobial resistance and represent a problem for the economy and public health. Natural antimicrobial substitutes to traditional antibiotics represent an essential tool in the fight against antibiotic resistance. Nanotechnology has shown considerable potential in different research fields, and the antimicrobial properties of silver nanoparticles are known. Silver has been used for medical purposes since ancient times because of its bactericidal properties, and the highly reactive surfaces of silver nanoparticles (AgNPs) indicate that they might have a function in antimicrobial applications. This work aimed to study the antimicrobial properties of biologically produced AgNPs from Origanum vulgare leaves compared to chemically produced AgNPs. Both types were characterized by UV–vis spectrophotometry, TEM, and dynamic light scattering and tested against three bacterial strains (Streptococcus agalactiae, and Aeromonas hydrophila, both isolated from Nile tilapia and Vibrio alginolyticus, isolated from sea bass) and three fungal strains (Aspergillus flavus, Fusarium moniliforme, and Candida albicans, all isolated from Nile tilapia). Disk diffusion test and evaluation of ultrastructure changes of tested microorganisms treated with AgNPs by transmission electron microscopy were performed. Moreover, the hemolytic properties of AgNPs were studied on chicken and goat red blood cells. The results obtained declare that the green biological production of silver nanoparticles is safer and more effective than the chemical one; moreover, AgNPs have interesting dose-dependent antimicrobial properties, with better results for biologically produced ones; their effectiveness against tested bacterial and fungal strains opens the way to their use to limit fish diseases, increase economy and improve human health.  相似文献   
17.
Objectives: Obesity is often associated with negative consequences, including hyperlipidemia and insulin resistance. Weight gain during pregnancy is also associated with major lipid alterations. Fat storage is enhanced in early pregnancy. At late gestation, hyperlipidemia becomes a major manifestation. The acylation‐stimulating protein (ASP) is a potent lipogenic adipocytokine that correlates with postprandial triglyceride (TG) clearance in vivo and has been linked to hyperlipidemic disorders. The role of ASP during a normal pregnancy is unknown. The objective of this study was to investigate plasma ASP levels in correlation with the lipid profile during late gestation. Research Methods and Procedures: Seventy healthy women at late gestation and 60 non‐pregnant controls of similar age and prepregnancy BMI were included in a cross‐sectional study. Fasting plasma ASP levels and the lipid profile of all of the women were measured. Results: ASP levels were markedly elevated in the pregnant women (66%, p < 0.001). ASP levels correlated strongly with the elevated levels of TGs (r = 0.608, p < 0.000), apolipoprotein B (0.519, p < 0.000), and low‐density lipoprotein‐cholesterol (r = 0.405, p < 0.000). Multivariate analysis adjusting for BMI and age showed that changes in ASP levels at late gestation were best predicted by TG and apoB levels, accounting for 53.8% of plasma ASP variation. For the controls, ASP strongly correlated with BMI, which was the only significant predictor of ASP levels. Discussion: Gestational hormone alterations during pregnancy may affect ASP function as a lipogenic factor. Increased plasma ASP levels at late gestation and their strong correlation with parameters reflecting very low‐density lipoprotein accumulation are suggestive of ASP resistance, which may further contribute to the hyperlipidemic state, shifting energy in the form of TGs to the rapidly growing fetus.  相似文献   
18.
Cancer cells isolated from two patients with malignant non-Hodgkin B-cell lymphomas that became resistant to chemotherapy during clinical treatment were made ?fourfold resistant in culture to anticancer drugs, that is cisplatin, etoposide, methotrexate and bortezomib. Because most resistant lines showed significantly increased expression of the anti-oxidative enzyme glutathione peroxidase 1 (GPx1), GPx1 was investigated as a target for inhibitor development. Virtual screening of a library of diverse structures by docking them to the active site of the X-ray crystal structure of bovine GPx1 uncovered compounds that might block the enzyme. An enzyme assay confirmed an acylhydrazone heterocycle (3) with GPx inhibitory activity. Combinations of 3 with the anticancer drugs listed above led to reversal of resistance in the lymphoma cell lines.  相似文献   
19.
20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号