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   53篇
  免费   0篇
系统科学   2篇
现状及发展   12篇
研究方法   9篇
综合类   29篇
自然研究   1篇
  2020年   1篇
  2016年   2篇
  2011年   1篇
  2010年   1篇
  2008年   2篇
  2007年   3篇
  2006年   1篇
  2005年   3篇
  2004年   6篇
  2003年   2篇
  2002年   4篇
  2001年   4篇
  2000年   4篇
  1999年   1篇
  1990年   1篇
  1986年   1篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1976年   2篇
  1975年   3篇
  1974年   1篇
  1973年   1篇
  1970年   1篇
  1969年   2篇
  1966年   2篇
排序方式: 共有53条查询结果,搜索用时 31 毫秒
11.
Zusammenfassung Die Isolierung der im Pansen vorkommenden Bakteriophagen wird erstmals beschrieben. Bakteriophagen, dieStreptococcus bovis und PansenSerratiae spp. angreifen, wurden aus vielen Pansen-Proben isoliert und eingehend untersucht;Bacteroides ruminicola Phage wurde dabei nicht aufgefunden.  相似文献   
12.
Planarians and memory   总被引:1,自引:0,他引:1  
A L Jacobson  C Fried  S D Horowitz 《Nature》1966,209(5023):599-601
  相似文献   
13.
Variation in FTO contributes to childhood obesity and severe adult obesity   总被引:18,自引:0,他引:18  
We identified a set of SNPs in the first intron of the FTO (fat mass and obesity associated) gene on chromosome 16q12.2 that is consistently strongly associated with early-onset and severe obesity in both adults and children of European ancestry with an experiment-wise P value of 1.67 x 10(-26) in 2,900 affected individuals and 5,100 controls. The at-risk haplotype yields a proportion of attributable risk of 22% for common obesity. We conclude that FTO contributes to human obesity and hence may be a target for subsequent functional analyses.  相似文献   
14.

In this article we discuss how an interdisciplinary research team partnered with a variety of stakeholders concerned with and/or affected by the impacts of climate change in the Red River Delta of Vietnam. The research, undertaken from 2016 to 2018, drew upon a wide range of methods to investigate systemically these impacts – with a view to the research inputting into the development of (more) sustainable ways of living. The research solicited various accounts of the experience of climate change in the community, set up learning processes in community meetings, and created an interface with government officials positioned at commune, district, provincial, and national levels. The intention was to offer support towards developing a learning process (broadly defined as including learnings/systemic inquiry across organizational levels of the society) to pursue options for sustainable living. The article offers our post-facto reflections which render more explicit (to ourselves and for the benefit of audiences) how the research team, with Hoang as lead researcher, facilitated the inquiry process towards developing a synthesis which underscored the assets for resilience to climate change and supported interventions to strengthen such (defined) assets.

  相似文献   
15.
Summary (–)--Fenchol, a compound occurring in plants but not heretofore reported to occur in an animal product, was isolated from volatiles released by adult male Mediterranean fruit flies,Ceratitis capitata Wiedemann, with the male's previously identified sex pheromones. It neither attracts females nor synergizes the pheromones, and its function remains unknown.The editors do not hold themselves responsible for the opinions expressed in the authors' brief reports. — Les auteurs sont seuls responsables des opinions exprimées dans ces brèves communications. — Für die Kurzmitteilungen ist ausschliesslich der Autor verantwortlich.—Per le brevi comunicazioni è responsabile solo l'autore. — . — Solo los autores son responsables de las opiniones expresadas en estas communicationes breves.Mention of a proprietary product in this paper does not constitute a recommendation or an endorsement of the product by the US Department of Agriculture.Acknowledgments. We thank C. Harding for assistance with extractions and fractionations, R.M. Waters for spectral analyses, M.S. Fujimoto and H. Higa for collecting the volatiles and conducting laboratory and cage bioassays, and T. Urago and S. Nakagawa for conducting the field tests.  相似文献   
16.
Regulation of cell movement is mediated by stretch-activated calcium channels.   总被引:10,自引:0,他引:10  
J Lee  A Ishihara  G Oxford  B Johnson  K Jacobson 《Nature》1999,400(6742):382-386
Intracellular calcium regulates many of the molecular processes that are essential for cell movement. It is required for the production of actomyosin-based contractile forces, the regulation of the structure and dynamics of the actin cytoskeletons, and the formation and disassembly of cell-substratum adhesions. Calcium also serves as a second messenger in many biochemical signal-transduction pathways. However, despite the pivotal role of calcium in motile processes, it is not clear how calcium regulates overall cell movement. Here we show that transient increases in intracellular calcium, [Ca2+]i, during the locomotion of fish epithelial keratocytes, occur more frequently in cells that become temporarily 'stuck' to the substratum or when subjected to mechanical stretching. We find that calcium transients arise from the activation of stretch-activated calcium channels, which triggers an influx of extracellular calcium. In addition, the subsequent increase in [Ca2+]i is involved in detachment of the rear cell margin. Thus, we have defined a mechanism by which cells can detect and transduce mechanical forces into biochemical signals that can modulate locomotion.  相似文献   
17.
Each giant planet of the Solar System has two main types of moons. 'Regular' moons are typically larger satellites with prograde, nearly circular orbits in the equatorial plane of their host planets at distances of several to tens of planetary radii. The 'irregular' satellites (which are typically smaller) have larger orbits with significant eccentricities and inclinations. Despite these common features, Neptune's irregular satellite system, hitherto thought to consist of Triton and Nereid, has appeared unusual. Triton is as large as Pluto and is postulated to have been captured from heliocentric orbit; it traces a circular but retrograde orbit at 14 planetary radii from Neptune. Nereid, which exhibits one of the largest satellite eccentricities, is believed to have been scattered from a regular satellite orbit to its present orbit during Triton's capture. Here we report the discovery of five irregular moons of Neptune, two with prograde and three with retrograde orbits. These exceedingly faint (apparent red magnitude m(R) = 24.2-25.4) moons, with diameters of 30 to 50 km, were presumably captured by Neptune.  相似文献   
18.
Amrani N  Ganesan R  Kervestin S  Mangus DA  Ghosh S  Jacobson A 《Nature》2004,432(7013):112-118
Nonsense-mediated messenger RNA decay (NMD) is triggered by premature translation termination, but the features distinguishing premature from normal termination are unknown. One model for NMD suggests that decay-inducing factors bound to mRNAs during early processing events are routinely removed by elongating ribosomes but remain associated with mRNAs when termination is premature, triggering rapid turnover. Recent experiments challenge this notion and suggest a model that posits that mRNA decay is activated by the intrinsically aberrant nature of premature termination. Here we use a primer extension inhibition (toeprinting) assay to delineate ribosome positioning and find that premature translation termination in yeast extracts is indeed aberrant. Ribosomes encountering premature UAA or UGA codons in the CAN1 mRNA fail to release and, instead, migrate to upstream AUGs. This anomaly depends on prior nonsense codon recognition and is eliminated in extracts derived from cells lacking the principal NMD factor, Upf1p, or by flanking the nonsense codon with a normal 3'-untranslated region (UTR). Tethered poly(A)-binding protein (Pab1p), used as a mimic of a normal 3'-UTR, recruits the termination factor Sup35p (eRF3) and stabilizes nonsense-containing mRNAs. These findings indicate that efficient termination and mRNA stability are dependent on a properly configured 3'-UTR.  相似文献   
19.
S Jacobson  H Shida  D E McFarlin  A S Fauci  S Koenig 《Nature》1990,348(6298):245-248
The human T-lymphotropic virus type I (HTLV-I), the first human retrovirus to be characterized, is associated with adult T-cell leukaemia and a chronic progressive disease of the central nervous system termed tropical spastic paraparesis, or HTLV-I-associated myelopathy. Only 1% of individuals infected with HTLV-I develop clinical disease however. The various manifestations of an HTLV-I infection may be related to differences in the genetic backgrounds of individuals, infection with variant strains of HTLV-I, differences in viral tropism or host immune response to the virus. Whereas the humoral response to HTLV-I is well characterized, little is known about the human cellular immune response, such as the production of cytotoxic T lymphocytes. Here we report the presence of high levels of circulating HTLV-I-specific cytotoxic T lymphocytes in patients with HTLV-I associated neurological disease but not in HTLV-I seropositive individuals without neurological involvement. These cytotoxic T lymphocytes are CD8+, HLA class I- restricted and predominantly recognize the HTLV-I gene products encoded in the regulatory region pX. These findings suggest that HTLV-I-specific cytotoxic T lymphocytes may contribute to the pathogenesis of associated neurological disorders associated with HTLV-I.  相似文献   
20.
Brown WM  Cronk L  Grochow K  Jacobson A  Liu CK  Popović Z  Trivers R 《Nature》2005,438(7071):1148-1150
Dance is believed to be important in the courtship of a variety of species, including humans, but nothing is known about what dance reveals about the underlying phenotypic--or genotypic--quality of the dancer. One measure of quality in evolutionary studies is the degree of bodily symmetry (fluctuating asymmetry, FA), because it measures developmental stability. Does dance quality reveal FA to the observer and is the effect stronger for male dancers than female? To answer these questions, we chose a population that has been measured twice for FA since 1996 (ref. 9) in a society (Jamaican) in which dancing is important in the lives of both sexes. Motion-capture cameras created controlled stimuli (in the form of videos) that isolated dance movements from all other aspects of visual appearance (including FA), and the same population evaluated these videos for dancing ability. Here we report that there are strong positive associations between symmetry and dancing ability, and these associations were stronger in men than in women. In addition, women rate dances by symmetrical men relatively more positively than do men, and more-symmetrical men value symmetry in women dancers more than do less-symmetrical men. In summary, dance in Jamaica seems to show evidence of sexual selection and to reveal important information about the dancer.  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