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   185篇
  免费   9篇
  国内免费   15篇
丛书文集   1篇
教育与普及   3篇
现状及发展   42篇
综合类   146篇
自然研究   17篇
  2022年   6篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2018年   4篇
  2017年   5篇
  2016年   3篇
  2015年   4篇
  2014年   5篇
  2013年   4篇
  2012年   18篇
  2011年   8篇
  2010年   7篇
  2009年   12篇
  2008年   10篇
  2007年   18篇
  2006年   15篇
  2005年   9篇
  2004年   14篇
  2003年   6篇
  2002年   5篇
  2001年   7篇
  2000年   4篇
  1999年   2篇
  1998年   3篇
  1997年   2篇
  1996年   5篇
  1994年   5篇
  1993年   4篇
  1992年   3篇
  1991年   2篇
  1990年   2篇
  1989年   4篇
  1988年   1篇
  1986年   7篇
排序方式: 共有209条查询结果,搜索用时 93 毫秒
51.
《Journal of Natural History》2012,46(33-34):2243-2256
The Indonesian island Sulawesi is well known for its fascinating fauna. Among the atyid and palaemonid freshwater shrimps described from Sulawesi are also a number of endemic species. In contrast, freshwater shrimps have never been reported from the nearby and smaller Peleng Island. Here we describe Caridina thomasi sp. nov. as a first record of an atyid freshwater shrimp from Peleng and compare it with atyids from Sulawesi and other localities. The new species is probably endemic to the island and shows some characters never described in the genus Caridina before. However, a molecular phylogeny of atyid shrimps from the Indo‐West Pacific based on mitochondrial DNA (16S) places C. thomasi within a clade of typical species of Caridina. We tentatively assign the new species to the genus Caridina and discuss the possibility of future changes in the classification of species in this genus.  相似文献   
52.
对吉林、辽宁两地23例满族个体的线粒体高可变Ⅰ区序列进行了测定,并采用APLP分析和编码区SNP分析将这些样本归属于单倍群A,B,C,D,D4,F,M,M8a和R,结合已经发表的东北地区其他人群的母系遗传数据,对蒙古族、朝鲜族、鄂温克族、鄂伦春族、达斡尔族以及汉族人群的线粒体遗传数据进行了主成分、分子差异、中介网络分析.结果表明:同一起源地区的民族之间有较近的遗传关系,同时居住在相同或相邻地区的民族之间同样表现出较近的遗传关系,表明东北各民族向外扩张时与当地居民发生了基因融合.  相似文献   
53.
利用Illumina和Pacbio测序技术对扬子鳃蛭(Ozobranchus jantseanus)线粒体基因组全序列进行测序及注释,并与NCBI数据库中蛭纲(Hirudinea)其他物种的线粒体全序列的排列方式和系统进化关系进行了比较,以确定其系统学地位.结果显示:获得的线粒体基因组序列长度为14 868 bp,蛋白编码基因存在2种起始密码子,分别为ATG和ATT;终止密码子共有4种,分别为TAA,TAG,TA和T;蛭纲10个物种的线粒体基因组全序列基因排序可分为2种类型,其差异表现在tRNAs的互换和长非编码区的长度的不同;扬子鳃蛭所属的吻蛭目(Rhynchobdellida)均为b型,绝大部分无吻蛭目(Arhynchobdellida)的排列方式为a型.基于蛭纲物种的13个蛋白编码基因(PCGs)的Neighbor-Joining(NJ)树进化分析显示,扬子鳃蛭与其他吻蛭目物种聚类.  相似文献   
54.
采用PCR技术扩增了美国红鱼线粒体DNA的细胞色素b和控制区基因片段,PCR扩增产物直接测序,分别得到1140bp和623bp的核苷酸序列。将所得序列与从Genbank中查到的美国红鱼序列进行比较,分析了序列中碱基的组成及变异情况,为美国红鱼的合理开发利用及养殖发展规划的制定提供遗传学数据,为保护中国海域生物种质资源多样性提供科学依据。  相似文献   
55.
Summary A new aryl hydrazone structure with high insecticidal activity against the Australian sheep blowfly,Lucilia cuprina, was shown to have a higher activity as an uncoupler of oxidative phosphorylation in insect compared to mammalian mitochondrial preparations. This compound possesses the requirements of other uncouplers in its measured pKa and lipid solubility. However, when compared to a closely related structure with similar physicochemical properties, its insecticidal and insect mitochondrial uncoupling activities are greater and it exhibits decreased mammalian toxicity corresponding to this differential biochemical selectivity.Acknowledgment. We thank Mr K. Rihs for preparation of the hydrazones and Prof. Dr K.H. Büchel for supply of hydrazone III.  相似文献   
56.
The mitochondrial DNA control region is amplified and sequenced from 8 genera and 10 species of gobiobotine fishes. The phylogenetic tree of Gobiobotinae and some representative species of other Cyprinid subfamilies obtained by the method of neighborhood joining, maximum likelihood and maximum parsimony with Danio rerio as an outgroup indicates that Gobiobotinae fishes are a monophyletic group which is close to Gobioninae subfamily. Gobiobotinae should be included into subfamily Gobioninae in terms of phylogenetic analysis. The research result supports that Gobiobotinae can be divided into genus Xenophysogobio and Gobiobotia. Xenophysogobio is the most primitive genera in the subfamily.  相似文献   
57.
Myeloid differentiation protein-88 (MyD88) is a crucial adaptor protein in the innate immune response. A protective role for MyD88 in normal cardiac function has been proposed in a surgical hypertrophic model. To assess the in vivo role of MyD88 in cardiac remodeling, we generated transgenic mice with cardiac-restricted expression of a dominant negative mutant of MyD88 (dnMyD88). Surprisingly, dnMyD88 transgenic mice displayed characteristic features of heart failure; including heart weight increase, cardiomyocytes enlargement, interstitial fibrosis, and re-expression of “fetal” genes. Echocardiographic examination of dnMyD88 hearts revealed dilated chamber volume and reduced cardiac contractility. DnMyD88 mice died from heart failure before they were 7 months old, as shown by Kaplan-Meier analysis. Additionally, the heart failure phenotype of dnMyD88 mice was associated with abnormal activation of the Akt/GSK-3β signaling pathway. These data provide the first evidence that normal MyD88 signaling is crucial for maintaining the physiological function of the adult heart.  相似文献   
58.
Mitochondrial association of alpha-synuclein causes oxidative stress   总被引:1,自引:1,他引:0  
α-Synuclein is a neuron-specific protein that contributes to the pathology of Parkinson’s disease via mitochondria-related mechanisms. The present study investigated possible interaction of α-synuclein with mitochondria and consequences of such interaction. Using SHSY cells overexpressing α-synuclein A53T mutant or wild-type, as well as isolated rat brain mitochondria, the present study shows that α-synuclein localizes at the mitochondrial membrane. In both SHSY cells and isolated mitochondria, interaction of α-synuclein with mitochondria causes release of cytochrome c, increase of mitochondrial calcium and nitric oxide, and oxidative modification of mitochondrial components. These findings suggest a pivotal role for mitochondria in oxidative stress and apoptosis induced by α-synuclein. Received 27 December 2007; received after revision 7 February 2008; accepted 8 February 2008  相似文献   
59.
Chronic exposure of pancreatic islets to elevated levels of palmitate leads to beta-cell dysfunction. We examined possible involvement of mitogenactivated protein kinases (MAPKs) and caspase-3 in palmitate-induced beta-cell dysfunction and tested the influence of the anti-diabetic drug rosiglitazone (ROZ). Palmitate amplified glucose-stimulated augmentation of intracellular free calcium ([Ca2+]i) and insulin secretion in incubated islets. ROZ suppressed this amplification, whereas it modestly augmented glucose-induced increase in these events. ROZ suppressed short-term palmitate-induced phosphorylation of pro-apoptotic MAPKs, i.e., SAPK/JNK and p38. Long-term islet culturing with palmitate induced inducible nitric oxide synthase (iNOS) and activated SAPK/JNK-p38. ROZ counteracted these effects. Both palmitate and cytokines activated caspase-3 in MIN6c4-cells and isolated islets. ROZ suppressed palmitate- but not cytokine-induced caspase-3 activation. Finally, after palmitate culturing, ROZ reversed the inhibitory effect on glucose-stimulated insulin release. We suggest that ROZ counteracts palmitateinduced deleterious effects on beta-cell function via suppression of iNOS, pro-apoptotic MAPKs and caspase-3 activities, as evidenced by restoration of glucose-stimulated insulin release.  相似文献   
60.
Three populations ofM. galloprovincialis from northern Greece were investigated using isozyme analysis, discriminant analysis of morphological characteristics and analysis of restriction fragments of mtDNA. For all three types of analysis significant intra- and interpopulation differentiation was found. This differentiation is very noticeable at the mtDNA genotype frequencies. Furthermore, the restriction patterns of mtDNA were different from those reported for Atlantic populations of this species.  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