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   100篇
  免费   5篇
  105篇
  2023年   1篇
  2022年   5篇
  2021年   5篇
  2020年   1篇
  2019年   3篇
  2018年   1篇
  2017年   2篇
  2016年   5篇
  2015年   4篇
  2014年   7篇
  2013年   7篇
  2012年   7篇
  2011年   4篇
  2010年   4篇
  2009年   3篇
  2008年   4篇
  2007年   6篇
  2006年   4篇
  2005年   3篇
  2004年   2篇
  1997年   1篇
  1995年   1篇
  1992年   4篇
  1991年   3篇
  1990年   2篇
  1989年   2篇
  1988年   4篇
  1987年   1篇
  1984年   1篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   1篇
  1974年   1篇
  1968年   1篇
排序方式: 共有105条查询结果,搜索用时 15 毫秒
11.
12.
ABSTRACT

Cyclodehydrogenation of the ethylidene derivative of (5-methyl-1,2,4-triazino[5,6-b]indol-3-yl)hydrazine (1) gave the angular isomer, 1,10-dimethyl-1,2,4-triazolo[3′,4′:3,4][1,2,4]triazino[5,6-b]indole (4). The linear isomer, 3,10-dimethyl-1,2,4-triazolo[4′,3′:2,3][1,2,4]triazino[5,6-b]indole (7) could be prepared regioselectively by the cyclodehydration of the acetyl derivative of 1. The cyclodehydrogenation was extended to the monosaccharide derivatives of 1. The role of the N-methyl group on the site of annellation has been discussed.  相似文献   
13.
14.
Polydrusus (s. str.) akreanus sp. n. is a new record of Curculionidae found in Iraqi Kurdistan. The new species is described, illustrated and compared with Polydrusus (s. str.) kadleci Borovec & Germann, 2013 known from Turkey and Iran, which is morphologically similar to the new species.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:9FDC3C5B-6854-4DEF-BDF6-EE6809F82DEE  相似文献   

15.
Alkylation of 2-methylthiopyrimidin-4(1H)-one (1a) and its 5(6)-alkyl derivatives 1bd as well as theophylline (7) with 2,2-bis(bromomethyl)-1,3-diacetoxypropane (2) under microwave irradia-tion gave the corresponding acyclonucleosides 1-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]-2-methyl-thio pyrmidin-4(1H)-ones 3ad and 7-[(3-acetoxy-2-acetoxymethyl-2-bromomethyl)prop-1-yl]theophylline (8), which upon further irradiation gave the double-headed acyclonucleosides 1,1 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis[(2-(methylthio)-pyrimidin-4(1H)-ones] 4ac, and 7,7 ′-[(2,2-diacetoxymethyl)-1,3-propylidene]-bis(theophylline) (9). The deacetylated derivatives were obtained by the action of sodium methoxide. The activity of deacetylated nucleosides against Hepatitis B virus was evaluated. Compound 5b showed moderate inhibition activity against HBV with mild cytotoxicity.  相似文献   
16.
In a preliminary paper [Decker et al. (1986) Biochem. Biophys. Res. Commun. 136, 1162] we have shown that the antimineralocorticoid spironolactone (SPL) preferentially inactivates dexamethasone (DEX) inducible rat hepatic cytochrome P450p isozymes in a suicidal manner. These findings are now confirmed, and the kinetic characteristics of such a process are detailed. In an effort to elucidate the mechanism of SPL-mediated inactivation of cytochrome P450, we have examined the metabolism of SPL in vitro. Incubation of [14C]SPL and NADPH with liver microsomes prepared from DEX-pretreated rats results in the formation of several polar metabolites separable by HPLC with UV detection. This process is found to be dependent on NADPH, O2, SPL, and enzyme concentration, as well as temperature. Furthermore, metabolite formation was significantly attenuated by P450 inhibitors CO and n-octylamine. Mass spectral analysis (thermospray LC/MS, FAB/MS, and FAB/MS/MS) of the two most prominent polar metabolites indicated that these compounds had molecular weights that corresponded to the sulfinic and sulfonic acid derivatives of deacetyl-SPL (SPL-SH). These findings document the formation of previously unreported polar metabolites of SPL by rat liver microsomes enriched in cytochrome P450p and implicate a role for this isozyme in the oxidation of the thiol moiety of deacetyl-SPL. The detection of such metabolites also implicates a catalytic trajectory that includes the thiyl radical and/or sulfenic acid species as a plausible protagonist in drug-mediated inactivation of cytochrome P450p.  相似文献   
17.
Selective alkylation of dyphylline (1) with (2-acetoxyethoxy)methyl bromide (2a) or 4-acetoxybutyl bromide (2b) afforded 3'-O-[(acetoxyethoxy)methyl]dyphylline (3a) and 3'-O-(4-acetoxybutyl)-dyphylline (3b), respectively. A trans esterification process rather than alkylation of the dihydroxy-propyl side chain in 1 had taken place during the reaction with 2-p-toluoyloxy)ethyl chloride (5) to afford the respective 3'-toluoyloxy derivative 7 and not the anticipated 3'-O-[(p-toluoyloxy)ethyl]-dyphylline (6). Deacylation of 3a,b and 7 afforded 4a,b and 1, respectively. Viral screening of selected compounds against HBV has been investigated.  相似文献   
18.
19.
An alternative method to other technologies to clean up the soil, air and water pollution by heavy metals is phytoremediation. Therefore, a pot culture experiment was conducted at the College of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran, in 2014 to determine the potential absorption of cadmium by Portulaca oleracea (Common purslane), Solanum nigrum (Black nightshade), Abutilon theophrasti (Velvetleaf) and Taraxacum officinale (Dandelion). The type of experiment was completely randomized design with factorial arrangement and four replications. The soil in pot was treated with different rates of CdCl2.H2O (0 (control), 10, 20, 40, 60, and 80 mg Cd/kg soil) and the plants were sown. With increasing concentration levels, fresh weight and dry weight of shoots and roots of all plant species were reduced. The reduction severity was ranked according the following order, P. oleracea > A. theophrasti > S. nigrum > T. officinale. Bioconcentration factor (BCF), Translocation factor (TF) and Translocation efficiency (TE%) was ranked according the following order, T. officinale > S. nigrum > A. theophrasti > P. oleracea. The results of this study revealed that T. officinale and S. nigrum are effective species to phytoremediate Cd-contaminated soil.  相似文献   
20.
CTL clones were developed from tumor infiltrating lymphocytes (TIL) from the ascites of a patient with ovarian carcinoma by coculture of TIL with autologous tumor cells and subsequent cloning in the presence of autologous tumor cells. These CTL clones expressed preferential cytolytic activity against autologous tumor cells but not against allogeneic ovarian tumor cells and the NK-sensitive cell line K562. The cytolytic activity of these CTL against autologous tumors was inhibited by anti-TCR (WT31 mAb), anti-HLA class I, and anti-CD3 mAb but not by the NK function antibody Leu 11b. Cloning of the autologous tumor cells in vitro revealed that the CTL clones of the ovarian TIL expressed differential abilities to lyse autologous tumor cell clones. The specificity analysis of these autologous tumor specific CTL suggested that they recognize several antigenic determinants present on the ovarian tumor cells. Our results indicate the presence of at least three antigenic epitopes on the tumor cells (designated OVA-1A, OVA-1B, and OVA-1C), one of which (OVA-1C) is unstable. These determinants are present either simultaneously or separately, and six types of ovarian clones can be distinguished on the basis of their expression. These results indicate that CTL of the TIL detect intratumor antigenic heterogeneity. The novel heterogeneity identified within the ovarian tumor cells in this report may be of significance for understanding cellular immunity in ovarian cancer and developing adoptive specific immunotherapeutic approaches in ovarian cancer.  相似文献   
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