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   161篇
  免费   7篇
  国内免费   13篇
  181篇
  2023年   3篇
  2022年   2篇
  2021年   9篇
  2020年   8篇
  2019年   4篇
  2018年   4篇
  2017年   6篇
  2016年   10篇
  2015年   3篇
  2014年   8篇
  2013年   9篇
  2012年   8篇
  2011年   7篇
  2010年   6篇
  2009年   4篇
  2008年   2篇
  2007年   4篇
  2006年   6篇
  2005年   5篇
  2004年   8篇
  2003年   3篇
  2002年   13篇
  2001年   11篇
  2000年   7篇
  1999年   7篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   3篇
  1994年   4篇
  1991年   1篇
  1990年   3篇
  1989年   2篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1968年   1篇
排序方式: 共有181条查询结果,搜索用时 15 毫秒
1.
This study aimed to investigate the protective effects of arbutin (ARB) against brain injury induced in rats with potassium bromate (KBrO3). The rats were divided into four groups as Group 1: Control (0.9% NaCl ml/kg/day p.), Group 2: KBrO3 (100 mg/kg (gavage), Group 3: ARB (50 mg/kg/day p.), and Group 4: KBrO3 + ARB (100 mg/kg (gavage) + 50 mg/kg/day p.). At the end of the fifth day of the study, the rats in all groups were killed, and their brain tissues were collected. In the collected brain tissues, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) levels were measured, and routine histopathological examinations were made. The MDA levels in the group that was exposed to KBrO3 were significantly higher than those in the control group (p ˂ 0.001). In comparison to the KBrO3 group, the MDA levels in the KBrO3 + ARB group were significantly lower (p ˂ 0.001). It was observed that SOD and CAT enzyme activity levels were significantly lower in the KBrO3 group compared to the control group (p ˂ 0.001), while these levels were significantly higher in the KBrO3 + ARB group than in the KBrO3 group (p ˂ 0.001). Additionally, the group that was subjected to KBrO3 toxicity, as well as ARB administration, had much lower levels of histopathologic signs than the group that was subjected to KBrO3 toxicity only. Consequently, it was found that KBrO3 exposure led to injury in the brain tissues of the rats, and using ARB was effective in preventing this injury.  相似文献   
2.
The modulation of cisPlatin cytotoxicity by interleukin-1 (IL-1α) was studied in cultures of SCC-7 tumor cells with and without tumor macrophages to examine potential mechanisms for the synergistic antitumor activity of cisPlatin and IL-1α in SCC-7 solid tumors. Neither IL-1α nor tumor macrophages affected the survival of clonogenic tumor cells and IL-1α had no direct effect on tumor cell growthin vitro. Macrophages had no direct effect on cisPlatin sensitivity (IC90=6.0 μM), but, the addition of IL-1α (500–2000U/ml) to co-cultures of cisPlatin pretreated tumor cells and resident tumor macrophages increased cell killing (IC90=3.1 μM). Similar responses were seen in primary cultures treated with cisPlatin before IL-1α. The modulation of cisPlatin cytotoxicity by IL-1α exhibited a biphasic dose response that paralleled the IL-1α dose dependent release of H2O2by resident tumor macrophages. Further, IL-1α modification of cisPlatin cytotoxicity was prompt and inhibited by catalase. CisPlatin and exogenous H2O2 (50 μM) produced more than additive SCC-7 clonogenic cell kill and hydroxyl radicals played an important role in the response. Interleukin-1 modulation of cisPlatin cytotoxicity was schedule dependent. IL-1α treatment for 24 hrs, before cisPlatin, produced drug resistance (IC90=11.1 μM). Our study shows that IL-1α can stimulate tumor macrophages to release pro-oxidants that modify cellular chemosensitivity in a schedule and dose dependent fashion. Our findings may also provide a mechanistic explanation for the synergistic antitumor activity of cisPlatin and IL-1αin vivo.  相似文献   
3.
高粱细胞质雄性不育系3197A(3A)在常温条件下是不育的(Figs.11&2),经热激(45℃)诱导不同程度地恢复了育性(Figs.13&4),为研究其不育机理提供了线索。热激2h后,3A中即可产生一类线粒体热激蛋白(HSPs)。其中,分子量为70kD的HSP70含量最高,也最为稳定。不过,3A中HSPs的稳定性弱于保持系3197B(3B)(Fig.2,Panels1~4)。放线菌素D抑制HSPs的合成,而氯霉素无此作用(Fig.2,Panels5&6),表明:HSPs是由核基因编码、在细胞质中合成、再跨膜转运到线粒体中的。3A幼穗经热激后,线粒体的总蛋白量猛增了2.7倍(Fig.3),达到3B的水平,育性亦变为可育的。Fig.4表明:HSP70反义链cDNA(R1)能进入到3B花药细胞中,并与靶RNA(HSC70mRNA)结合,而对照、正义链cDNA(D)链无此反应。由此、再增加一个通用保守序列的反义链cDNA(R2)、共两个探针(R1、R2),可以检测到:3A在常温下没有能力合成HSC70mRNA(Fig.5),而在热激条件下,转变为有能力(Fig.6)。启示:3A在热激条件下由不育转变为可育  相似文献   
4.
里氏木霉LW1固态发酵纤维素酶条件的研究   总被引:3,自引:0,他引:3  
采用里氏木霉LW 1(Trichoderma.Reesei)固体发酵生产纤维素酶,研究了秸杆粉和麦麸用量、料水比、起始pH值、发酵温度和发酵时间对该菌株产纤维素酶活力的影响。试验结果表明,里氏木霉LW 1的适宜发酵条件为:在秸秆∶麦麸=1∶1,料水比为1∶2的前提条件下,培养温度28℃,发酵周期为72h,起始pH5.5时产酶活力最高。浸出液中FPA酶活为119.417u/g干物质,CMC酶活为452.433u/g干物质。  相似文献   
5.
正交试验法研究决明子提取工艺   总被引:7,自引:0,他引:7  
采用正交试验法优选出了决明子中蒽醌衍生物的最佳提取工艺条件为:50%乙醇水为浸提剂;固液比1:5,提取温度70℃,提取时间2h。总蒽醌衍生物的产率为0.83%。如果采用醋酸酸化预处理工艺,可使蒽醌衍生物(抗癌、抗菌有效部位)的产率增加0.19%。通过溶剂萃取和沉淀分离得到两大有效部位:脂溶性部位(蒽醌衍性物)和水溶性部位(蒽醌甙类)。  相似文献   
6.
A novel, sensitive and rapid CL method coupled with high‐performance liquid chromatography separation for the determination of carbamazepine is described. The method was based on the fact that carbamazepine could significantly enhance the chemiluminescence of the reaction of cerium sulfate and tris(2,2‐bipyridyl) ruthenium(II) in the presence of acid. The chromatographic separation was performed on a Kromasil® (Sigma‐Aldrich) TM RP‐C18 column (id: 150 mm × 4.6 mm, particle size: 5 µm, pore size: 100 Å) with a mobile phase consisting of methanol–water‐glacial acetic acid (70:29:1, v/v/v) at a flowrate of 1.0 mL/min, the total analysis time was within 650 s. Under optimal conditions, CL intensity was linear for carbamazepine in the range 2.0 × 10?8 ~ 4.0 × 10?5 g/mL, with a detection limit of 6.0 × 10?9 g/mL (S/N = 3) and the relative standard detection was 2.5% for 2.0 × 10?6 g/mL (n = 11). This method was successfully applied to the analysis of carbamazepine in human urine and serum samples. The possible mechanism of the CL reaction is also discussed briefly. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
7.
8.
Carrion-feeding flies use odours emanating from the decomposing corpse as cues for oviposition and are described as generalists because the larvae feed on the corpses of diverse species. Whereas several features of the corpse may influence the oviposition choices of these flies, it is not known whether there is a preference for a particular species of corpse. We provided carrion flies with ovipositional (and feeding) choices in a field experiment, in which various odour sources were presented simultaneously. We found novel evidence of broadly consistent choices of carrion by flies from four families. Traps baited with decaying fish flesh captured the greatest number of individuals, whereas traps baited with decaying pig liver typically attracted the least. We also asked whether individuals captured in the various baits vary in antennal size, perhaps reflecting different capacities for odour detection. There was a trend for individuals of Lucilia sericata Meigen (Diptera: Calliphoridae) and the platystomatid collected from the traps baited with pig liver to have significantly larger antennae, whereas individuals of Muscina stabulans (Fallen) (Diptera: Muscidae) captured in traps baited with marine fish flesh had relatively longer antennae for their body size. Our data reveal a more nuanced pattern of oviposition behaviour in these generalist carrion flies, which may reflect differences in their preference of carrion with different nutrients, and in their capacity to detect particular odours.  相似文献   
9.
Pathological cardiac hypertrophy is the most important risk factor for developing chronic heart failure. Therefore, the discovery of novel agents for treating pathological cardiac hypertrophy remains urgent. In the present study, we examined the therapeutic effect and mechanism of periplocymarin (PM)‐mediated protection against pathological cardiac hypertrophy using angiotensinII (AngII)‐stimulated cardiac hypertrophy in H9c2 cells and transverse aortic constriction (TAC)‐induced cardiac hypertrophy in mice. In vitro, PM treatment significantly reduced the surface area of H9c2 cells and expressions of hypertrophy‐related proteins. Meanwhile, PM markedly down‐regulated AngII‐induced translocation of p‐STAT3 into the nuclei and enhanced the phosphorylation levels of JAK2 and STAT3 proteins. The STAT3 specific inhibitor S3I‐201 or siRNA‐mediated depleted expression could alleviate AngII‐induced cardiac hypertrophy in H9c2 cells following PM treatment; however, PM failed to reduce the expressions of hypertrophy‐related proteins and phosphorylated STAT3 in STAT3‐overexpressing cells, indicating that PM protected against AngII‐induced cardiac hypertrophy by modulating STAT3 signalling. In vivo, PM reversed TAC‐induced cardiac hypertrophy, as determined by down‐regulating ratios of heart weight to body weight (HW/BW), heart weight to tibial length (HW/TL) and expressions of hypertrophy‐related proteins accompanied by the inhibition of the JAK2/STAT3 pathway. These results revealed that PM could effectively protect the cardiac structure and function in experimental models of pathological cardiac hypertrophy by inhibiting the JAK2/STAT3 signalling pathway. PM is expected to be a potential lead compound of the novel agents for treating pathological cardiac hypertrophy.  相似文献   
10.
When working on an ongoing genome sequencing and assembly project, it is rather inconvenient when gene identifiers change from one build of the assembly to the next. The gene labelling system described here, UniqTag, addresses this common challenge. UniqTag assigns a unique identifier to each gene that is a representative k-mer, a string of length k, selected from the sequence of that gene. Unlike serial numbers, these identifiers are stable between different assemblies and annotations of the same data without requiring that previous annotations be lifted over by sequence alignment. We assign UniqTag identifiers to ten builds of the Ensembl human genome spanning eight years to demonstrate this stability. The implementation of UniqTag in Ruby and an R package are available at https://github.com/sjackman/uniqtag sjackman/uniqtag. The R package is also available from CRAN: install.packages ("uniqtag"). Supplementary material and code to reproduce it is available at https://github.com/sjackman/uniqtag-paper.  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