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   462篇
  免费   48篇
  2023年   5篇
  2022年   12篇
  2021年   22篇
  2020年   20篇
  2019年   26篇
  2018年   23篇
  2017年   21篇
  2016年   21篇
  2015年   26篇
  2014年   39篇
  2013年   23篇
  2012年   45篇
  2011年   50篇
  2010年   21篇
  2009年   15篇
  2008年   20篇
  2007年   15篇
  2006年   13篇
  2005年   16篇
  2004年   13篇
  2003年   7篇
  2002年   6篇
  2001年   1篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1997年   3篇
  1996年   2篇
  1994年   1篇
  1993年   1篇
  1992年   3篇
  1991年   1篇
  1990年   2篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1985年   2篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
  1979年   1篇
  1978年   2篇
  1977年   4篇
  1976年   1篇
  1974年   2篇
  1973年   1篇
  1969年   1篇
  1968年   4篇
  1957年   1篇
排序方式: 共有510条查询结果,搜索用时 31 毫秒
91.
In this study the physicochemical and transfection properties of cationic hydroxyethylcellulose/plasmid DNA (pDNA) nanoparticles were investigated and compared with the properties of DNA nanoparticles based on polyethylene imine (PEI), which is widely investigated as a gene carrier. The two types of cationic hydroxyethylcelluloses studied, polyquaternium-4 (PQ-4) and polyquaternium-10 (PQ-10), are already commonly used in cosmetic and topical drug delivery devices. Both PQ-4 and PQ-10 spontaneously interact with pDNA with the formation of nanoparticles approximately 200 nm in size. Gel electrophoresis and fluorescence dequenching experiments indicated that the interactions between pDNA and the cationic celluloses were stronger than those between pDNA and PEI. The cationic cellulose/pDNA nanoparticles transfected cells to a much lesser extent than the PEI-based pDNA nanoparticles. The low transfection property of the PQ-4/pDNA nanoparticles was attributed to their neutrally charged surface, which does not allow an optimal binding of PQ-4/pDNA nanoparticles to cellular membranes. Although the PQ-10/pDNA nanoparticles were positively charged and thus expected to be taken up by cells, they were also much less efficient in transfecting cells than were PEI/pDNA nanoparticles. Agents known to enhance the endosomal escape were not able to improve the transfection properties of PQ-10/pDNA nanoparticles, indicating that a poor endosomal escape is, most likely, not the major reason for the low transfection activity of PQ-10/pDNA nanoparticles. We hypothesized that the strong binding of pDNA to PQ-10 prohibits the release of pDNA from PQ-10 once the PQ-10/pDNA nanoparticles arrive in the cytosol of the cells. Tailoring the nature and extent of the cationic side chains on this type of cationic hydroxyethylcellulose may be promising to further enhance their DNA delivery properties.  相似文献   
92.
Lack of temperature sensation of myoelectric prosthetic hand limits the daily activities of amputees.To this end,a non-invasive temperature sensation method is proposed to train amputees to sense temperature with psychophysical sensory substitution.In this study,22 healthy participants took part besides 5 amputee participants.The duration time of the study was 31 days with five test steps according to the Leitner technique.An adjustable temperature mug and a Peltier were used to change the temperature of the water/phantom digits to induce temperature to participants.Also,to isolate the surround-ings and show colors,a Virtual Reality(VR)glass was employed.The statistical results conducted are based on the response of participants with questionnaire method.Using Chi-square tests,it is concluded that participants answer the experiment significantly correctly using the Leitner technique(P value<0.05).Also,by applying the"Repeated Measures ANOVA",it is noticed that the time of numbness felt by participants had significant(P value<0.001)difference.Participants could remember lowest and highest temperatures significantly better than other temperatures(P value<0.001);furthermore,the well-trained amputee participant practically using the prosthesis with 72.58%could identify object's temperature with only once time experimenting the color temperature.  相似文献   
93.
KS Lee  RN Kim  BH Yoon  DS Kim  SH Choi  DW Kim  SH Nam  A Kim  A Kang  KH Park  JE Jung  SH Chae  HS Park 《Bioinformation》2012,8(11):532-534
Recently, next generation sequencing (NGS) technologies have led to a revolutionary increase in sequencing speed and costefficacy. Consequently, a vast number of contigs from many recently sequenced bacterial genomes remain to be accurately mapped and annotated, requiring the development of more convenient bioinformatics programs. In this paper, we present a newly developed web-based bioinformatics program, Bacterial Genome Mapper, which is suitable for mapping and annotating contigs that have been assembled from bacterial genome sequence raw data. By constructing a multiple alignment map between target contig sequences and two reference bacterial genome sequences, this program also provides very useful comparative genomics analysis of draft bacterial genomes. AVAILABILITY: The database is available for free at http://mbgm.kribb.re.kr.  相似文献   
94.
95.
96.
Inflammation is a major mediator of CKD progression and is partly driven by altered gut microbiome and intestinal barrier disruption, events which are caused by: urea influx in the intestine resulting in dominance of urease-possessing bacteria; disruption of epithelial barrier by urea-derived ammonia leading to endotoxemia and bacterial translocation; and restriction of potassium-rich fruits and vegetables which are common sources of fermentable fiber. Restriction of these foods leads to depletion of bacteria that convert indigestible carbohydrates to short chain fatty acids which are important nutrients for colonocytes and regulatory T lymphocytes. We hypothesized that a high resistant starch diet attenuates CKD progression. Male Sprague Dawley rats were fed a chow containing 0.7% adenine for 2 weeks to induce CKD. Rats were then fed diets supplemented with amylopectin (low-fiber control) or high fermentable fiber (amylose maize resistant starch, HAM-RS2) for 3 weeks. CKD rats consuming low fiber diet exhibited reduced creatinine clearance, interstitial fibrosis, inflammation, tubular damage, activation of NFkB, upregulation of pro-inflammatory, pro-oxidant, and pro-fibrotic molecules; impaired Nrf2 activity, down-regulation of antioxidant enzymes, and disruption of colonic epithelial tight junction. The high resistant starch diet significantly attenuated these abnormalities. Thus high resistant starch diet retards CKD progression and attenuates oxidative stress and inflammation in rats. Future studies are needed to explore the impact of HAM-RS2 in CKD patients.  相似文献   
97.
Reward-seeking and relapse to drug use are two characteristics of addiction and reports have indicated the role of hippocampal structures in reward learning. To find the best ways of treatment, the understanding of the neurobiological mechanisms of reward and its involved factors is a must. For this reason, in the present study, we aimed to investigate the role of D1- and D2-like dopamine receptors and compared their activities in the CA1 region, focusing on the reinstatement induced by forced swim stress (FSS) or the combination of FSS and a subthreshold dose of morphine in extinguished morphine-CPP in rats. The rats were bilaterally implanted by two separate cannulas into the CA1 region. The animals received different doses of SCH23390 or sulpiride (0.5, 2, and 4 µg/0.5 µl vehicle/side) into the CA1 region on the reinstatement day and were tested for FSS-induced reinstatement or the combination of FSS and a subthreshold dose of morphine in separate groups. Our findings indicated that the D1- and D2-like receptor antagonists attenuated the reinstatement induced by the combination of FSS and the subthreshold dose of morphine. The behavioral results were more prominent in the groups of animals that received SCH23390 as compared to sulpiride. The data may suggest a role for the dopamine receptors in the CA1 region in relapse to drugs of abuse, which may be induced by exposure to a stressor.  相似文献   
98.
99.
BackgroundMalaria remains endemic at low levels in the south-eastern provinces of Iran bordering Afghanistan and Pakistan, with the majority of cases attributable to P. vivax. The national guidelines recommend chloroquine (CQ) as blood-stage treatment for uncomplicated P. vivax, but the large influx of imported cases enhances the risk of introducing CQ resistance (CQR).ConclusionsThe contrasting low versus high diversity in the two sub-populations (K1 and K2) infers that a combination of local transmission and cross-border malaria from higher transmission regions shape the genetic make-up of the P. vivax population in south-eastern Iran. There was no molecular evidence of CQR amongst the local or imported cases, but ongoing clinical surveillance is warranted.  相似文献   
100.
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