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   513篇
  免费   52篇
  565篇
  2024年   1篇
  2023年   8篇
  2022年   17篇
  2021年   45篇
  2020年   20篇
  2019年   25篇
  2018年   22篇
  2017年   16篇
  2016年   28篇
  2015年   41篇
  2014年   38篇
  2013年   32篇
  2012年   56篇
  2011年   39篇
  2010年   24篇
  2009年   14篇
  2008年   18篇
  2007年   16篇
  2006年   15篇
  2005年   14篇
  2004年   37篇
  2003年   16篇
  2002年   17篇
  2001年   2篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1995年   1篇
排序方式: 共有565条查询结果,搜索用时 0 毫秒
1.
In the United States, the Native American Graves Protection and Repatriation Act (NAGPRA) provides a specific framework for the disposition of Native American Ancestral remains within its purview. However, samples such as a bone fragment, tooth, or other biological tissue taken from the remains of these Ancestors have been treated by institutions and researchers as independent of the individual from whom they were removed and used in destructive research such as paleogenomic and other archaeometric analyses without consultation, consent, and collaboration from Native American communities; are not cared for in keeping with the current best practices for Indigenous Ancestors; and are not likely to be repatriated to their communities. Here, we demonstrate that any biological samples removed from Ancestors who are covered under NAGPRA must also be handled according to the stipulations defined for “human remains” within the legislation. As such, we are not proposing a change to existing legislation, but rather best practices, specific to the context of the United States and NAGPRA, relating to the use of and care for biological samples taken from Native American Ancestors.  相似文献   
2.
3.
The whole-cell phospholipid composition of the six known polymorphic species of Tetrahymena has been examined by [(3)H]acetate and [(3)H]myristic acid radiolabeling, and by gas-liquid chromatography of total phospholipid-bound fatty acids. Five of the polymorphic species contained similar phospholipid profiles following radiolabeling in that phosphatidylethanolamine (PE) was the predominant phospholipid; however, in cells of Tetrahymena patula LFF, aminoethylphosphonolipid was present in amounts nearly equal to PE. Tetrahymena patula LFF contained an unusually large percentage of sphingolipid (16.2% by [(3)H]acetate radiolabeling). Substantial differences were found in the fatty acid profiles of the polymorphic species, which included the degree of fatty acid unsaturation and relative weight percentages of odd-chain fatty acids. Tetrahymena vorax contained a low ratio of unsaturated C(18) fatty acids to saturated C(18) fatty acids as compared with all other species examined. The differentiating species generally contained a lesser percentage of monoenoic fatty acids and a lower ratio of unsaturated C(16) fatty acids to saturated C(16) fatty acids as compared with the two monomorphic species examined.  相似文献   
4.
5.
Sphagnum‐dominated peatlands comprise a globally important pool of soil carbon (C) and are vulnerable to climate change. While peat mosses of the genus Sphagnum are known to harbor diverse microbial communities that mediate C and nitrogen (N) cycling in peatlands, the effects of climate change on Sphagnum microbiome composition and functioning are largely unknown. We investigated the impacts of experimental whole‐ecosystem warming on the Sphagnum moss microbiome, focusing on N2 fixing microorganisms (diazotrophs). To characterize the microbiome response to warming, we performed next‐generation sequencing of small subunit (SSU) rRNA and nitrogenase (nifH) gene amplicons and quantified rates of N2 fixation activity in Sphagnum fallax individuals sampled from experimental enclosures over 2 years in a northern Minnesota, USA bog. The taxonomic diversity of overall microbial communities and diazotroph communities, as well as N2 fixation rates, decreased with warming (p < 0.05). Following warming, diazotrophs shifted from a mixed community of Nostocales (Cyanobacteria) and Rhizobiales (Alphaproteobacteria) to predominance of Nostocales. Microbiome community composition differed between years, with some diazotroph populations persisting while others declined in relative abundance in warmed plots in the second year. Our results demonstrate that warming substantially alters the community composition, diversity, and N2 fixation activity of peat moss microbiomes, which may ultimately impact host fitness, ecosystem productivity, and C storage potential in peatlands.  相似文献   
6.
7.
Small G-proteins are key regulatory molecules that activate the actin nucleation machinery to drive cytoskeletal rearrangements during plasma membrane remodeling. However, the ability of small G-proteins to interact with nucleation factors on internal membranes to control trafficking processes has not been well characterized. Here we investigated roles for members of the Rho, Arf, and Rab G-protein families in regulating WASP homologue associated with actin, membranes, and microtubules (WHAMM), an activator of Arp2/3 complex–mediated actin nucleation. We found that Rab1 stimulated the formation and elongation of WHAMM-associated membrane tubules in cells. Active Rab1 recruited WHAMM to dynamic tubulovesicular structures in fibroblasts, and an active prenylated version of Rab1 bound directly to an N-terminal domain of WHAMM in vitro. In contrast to other G-protein–nucleation factor interactions, Rab1 binding inhibited WHAMM-mediated actin assembly. This ability of Rab1 to regulate WHAMM and the Arp2/3 complex represents a distinct strategy for membrane remodeling in which a Rab G-protein recruits the actin nucleation machinery but dampens its activity.  相似文献   
8.
9.
Recombinant monoclonal antibodies (mAbs) have become an important category of biological therapeutics. mAbs share the same structures and biological functions as endogenous IgG molecules. One function is complement-dependent cytotoxicity (CDC) initiation by binding of C1q. Traditionally, ELISA methods have been utilized to measure C1q binding. A new robust capture method was established in this study to measure the binding affinity of C1q to antibodies by surface plasmon resonance (SPR). The utility of this method was demonstrated by determination of the difference in IgG subclass specificity of C1q binding.  相似文献   
10.
Six baleen whale species are found in the temperate western North Atlantic Ocean, with limited information existing on the distribution and movement patterns for most. There is mounting evidence of distributional shifts in many species, including marine mammals, likely because of climate‐driven changes in ocean temperature and circulation. Previous acoustic studies examined the occurrence of minke (Balaenoptera acutorostrata) and North Atlantic right whales (NARW; Eubalaena glacialis). This study assesses the acoustic presence of humpback (Megaptera novaeangliae), sei (B. borealis), fin (B. physalus), and blue whales (B. musculus) over a decade, based on daily detections of their vocalizations. Data collected from 2004 to 2014 on 281 bottom‐mounted recorders, totaling 35,033 days, were processed using automated detection software and screened for each species' presence. A published study on NARW acoustics revealed significant changes in occurrence patterns between the periods of 2004–2010 and 2011–2014; therefore, these same time periods were examined here. All four species were present from the Southeast United States to Greenland; humpback whales were also present in the Caribbean. All species occurred throughout all regions in the winter, suggesting that baleen whales are widely distributed during these months. Each of the species showed significant changes in acoustic occurrence after 2010. Similar to NARWs, sei whales had higher acoustic occurrence in mid‐Atlantic regions after 2010. Fin, blue, and sei whales were more frequently detected in the northern latitudes of the study area after 2010. Despite this general northward shift, all four species were detected less on the Scotian Shelf area after 2010, matching documented shifts in prey availability in this region. A decade of acoustic observations have shown important distributional changes over the range of baleen whales, mirroring known climatic shifts and identifying new habitats that will require further protection from anthropogenic threats like fixed fishing gear, shipping, and noise pollution.  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