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   169篇
  免费   0篇
  国内免费   2篇
系统科学   6篇
丛书文集   1篇
理论与方法论   9篇
现状及发展   84篇
研究方法   9篇
综合类   54篇
自然研究   8篇
  2019年   2篇
  2018年   10篇
  2017年   3篇
  2016年   6篇
  2015年   4篇
  2013年   8篇
  2012年   8篇
  2011年   6篇
  2010年   2篇
  2008年   7篇
  2007年   2篇
  2006年   3篇
  2005年   5篇
  2004年   2篇
  2003年   5篇
  2002年   5篇
  2001年   6篇
  2000年   6篇
  1999年   3篇
  1998年   2篇
  1996年   1篇
  1995年   2篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   4篇
  1988年   2篇
  1986年   2篇
  1984年   1篇
  1982年   3篇
  1981年   6篇
  1980年   2篇
  1979年   5篇
  1978年   3篇
  1977年   1篇
  1976年   5篇
  1975年   1篇
  1974年   4篇
  1973年   6篇
  1972年   5篇
  1971年   4篇
  1970年   2篇
  1969年   2篇
  1968年   2篇
  1967年   2篇
  1964年   4篇
  1963年   1篇
  1962年   1篇
  1957年   1篇
排序方式: 共有171条查询结果,搜索用时 171 毫秒
1.
Cilia beating is powered by the inner and outer dynein arms (IDAs and ODAs). These multi-subunit macrocomplexes are arranged in two rows on each outer doublet along the entire cilium length, except its distal end. To generate cilia beating, the activity of ODAs and IDAs must be strictly regulated locally by interactions with the dynein arm-associated structures within each ciliary unit and coordinated globally in time and space between doublets and along the axoneme. Here, we provide evidence of a novel ciliary complex composed of two conserved WD-repeat proteins, Fap43p and Fap44p. This complex is adjacent to another WD-repeat protein, Fap57p, and most likely the two-headed inner dynein arm, IDA I1. Loss of either protein results in altered waveform, beat stroke and reduced swimming speed. The ciliary localization of Fap43p and Fap44p is interdependent in the ciliate Tetrahymena thermophila.  相似文献   
2.
Summary Hexoprenaline potentiated the14C-aminopyrine uptake (a reliable index of H+ generation) of isolated rat gastric cells stimulated by 10–6–10–4 mol/l carbachol, and inhibited that in response to 10–4 mol/l histamine without and in the presence of propranolol. It is concluded that hexoprenaline acts as a partial agonist on parietal cell H2-receptors and that -adrenoceptor activation may functionally modualte gastric acid secretion.Acknowledgments. S. Maliski, Institute of Rheumatology, Warszawa, held a fellowship of the Alexander v. Humboldt-Foundation. The study was supported by the Deutsche Forschungsgemeinschaft. The skilful technical assistance of Mrs R. Maier and Mr R. Beer is gratefully acknowledged.  相似文献   
3.
Summary Complete removal of villous as well as upper-crypt epithelium was achieved in vivo by vibration of an intestinal segment using tetraphenylboron sodium (TPB) as a disassociation agent.Acknowledgments. The authors thank Hicol Industrieterrein De Bosschen for supplying TPB. Research was supported by MR-II 1.3.14.p.2 grant.  相似文献   
4.
Summary A correlation between the postirradiation increase of the small intestine motility and the prostaglandin-like activity in this organ during gastrointestinal syndrome was observed. Indomethacin decreased the elevated motility of intestine and reduced the prostaglandin-like activity in this syndrome.Acknowledgments. The work was supported by the Polish Academy of Sciences.  相似文献   
5.
The bat fauna of Albania, a country located in a Balkan glacial refugium and a Mediterranean biodiversity hotspot, has remained poorly studied although as many as 21 species and representatives of three species complexes had been reported before 2003. It was expected that several new species would be added to the country’s list of fauna, not only due to their occurrence in adjacent regions but to the splitting of already known taxa into sibling species and the discovery of new, cryptic species. Altogether, we recorded 32 bat species in Albania, including all of those previously reported (21) and 11 new species for the country, as a result of field work conducted in 2003–2012. Here, we report on eight bat species including Rhinolophus mehelyi, Nyctalus lasiopterus, Plecotus kolombatovici, Barbastella barbastellus, Myotis brandtii that had not been reported previously in Albania while three species (Pipistrellus pipistrellus, Plecotus austriacus, Myotis mystacinus) had been reported before changes to their taxonomy and so could be treated only as representatives of a particular species complex (i.e. sensu lato). We greatly extended the known geographic ranges of five species in the south of Europe.  相似文献   
6.
7.
Sundal AV  Shepherd A  Nienow P  Hanna E  Palmer S  Huybrechts P 《Nature》2011,469(7331):521-524
Fluctuations in surface melting are known to affect the speed of glaciers and ice sheets, but their impact on the Greenland ice sheet in a warming climate remains uncertain. Although some studies suggest that greater melting produces greater ice-sheet acceleration, others have identified a long-term decrease in Greenland's flow despite increased melting. Here we use satellite observations of ice motion recorded in a land-terminating sector of southwest Greenland to investigate the manner in which ice flow develops during years of markedly different melting. Although peak rates of ice speed-up are positively correlated with the degree of melting, mean summer flow rates are not, because glacier slowdown occurs, on average, when a critical run-off threshold of about 1.4?centimetres a day is exceeded. In contrast to the first half of summer, when flow is similar in all years, speed-up during the latter half is 62?±?16 per cent less in warmer years. Consequently, in warmer years, the period of fast ice flow is three times shorter and, overall, summer ice flow is slower. This behaviour is at odds with that expected from basal lubrication alone. Instead, it mirrors that of mountain glaciers, where melt-induced acceleration of flow ceases during years of high melting once subglacial drainage becomes efficient. A model of ice-sheet flow that captures switching between cavity and channel drainage modes is consistent with the run-off threshold, fast-flow periods, and later-summer speeds we have observed. Simulations of the Greenland ice-sheet flow under climate warming scenarios should account for the dynamic evolution of subglacial drainage; a simple model of basal lubrication alone misses key aspects of the ice sheet's response to climate warming.  相似文献   
8.
Nanoparticles (NPs) comprised of nanoengineered complexes are providing new opportunities for enabling targeted delivery of a range of therapeutics and combinations. A range of functionalities can be included within a nanoparticle complex, including surface chemistry that allows attachment of cell-specific ligands for targeted delivery, surface coatings to increase circulation times for enhanced bioavailability, specific materials on the surface or in the nanoparticle core that enable storage of a therapeutic cargo until the target site is reached, and materials sensitive to local or remote actuation cues that allow controlled delivery of therapeutics to the target cells. However, despite the potential benefits of NPs as smart drug delivery and diagnostic systems, much research is still required to evaluate potential toxicity issues related to the chemical properties of NP materials, as well as their size and shape. The need to validate each NP for safety and efficacy with each therapeutic compound or combination of therapeutics is an enormous challenge, which forces industry to focus mainly on those nanoparticle materials where data on safety and efficacy already exists, i.e., predominantly polymer NPs. However, the enhanced functionality affordable by inclusion of metallic materials as part of nanoengineered particles provides a wealth of new opportunity for innovation and new, more effective, and safer therapeutics for applications such as cancer and cardiovascular diseases, which require selective targeting of the therapeutic to maximize effectiveness while avoiding adverse effects on non-target tissues.  相似文献   
9.
The shallow-water tanaidacean fauna of the Bass Strait has been the subject of recent intensive studies. The present paper extends this work into the deeper waters of the region, describing two new species and one new genus. The new species of the genus Paradoxapseudes has a combination of three maxillule palp setae, no plumose setae on the basis of pereopod 1 nor proximal serration on the antennal peduncle. The second species represents a new genus of the family Anarthruridae, having six marginal setae on the third maxilliped palp article and spines on the merus and carpus of the anterior pereopods. The high diversity of Tanaidacea in Australian waters is discussed. In particular, we conclude that Australian coasts suffer a diversity of immigration routes, have sufficient marine longevity, and afford such a diversity of available niches to have allowed multiple colonization and subsequent allopatric speciation of Tanaidacea. http://www.zoobank.org/urn:lsid:zoobank.org:pub:EE309A5A-E06D-416F-95BD-4C8D0D2BEB97  相似文献   
10.
Summary Binding by rat thymus lymphocytes of thymosin V, labeled with colloidal gold, was studied. Under the experimental conditions employed at least 2.8% cells exhibited thymosin binding sites.This article originally appeared in Experientia 38 (5) 1982, p. 618 but was accompanied by imporperfigures. Supported by Polish Academy of SciencesThe authors thank Dr A.L. Goldstein for the gift of thymosin. Also are grateful to Dr J. Jaroszewski for helpful discussion.  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