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   114篇
  免费   12篇
  2017年   3篇
  2015年   2篇
  2014年   5篇
  2013年   4篇
  2012年   2篇
  2011年   2篇
  2010年   2篇
  2009年   3篇
  2008年   5篇
  2007年   1篇
  2006年   5篇
  2005年   1篇
  2004年   1篇
  2001年   2篇
  2000年   5篇
  1999年   1篇
  1998年   8篇
  1997年   3篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1992年   3篇
  1990年   2篇
  1989年   1篇
  1988年   2篇
  1986年   2篇
  1985年   3篇
  1984年   1篇
  1983年   1篇
  1982年   4篇
  1981年   1篇
  1980年   3篇
  1979年   6篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1975年   3篇
  1974年   1篇
  1973年   1篇
  1972年   4篇
  1971年   3篇
  1970年   1篇
  1969年   3篇
  1968年   4篇
  1967年   1篇
  1966年   3篇
  1965年   1篇
  1957年   1篇
  1956年   1篇
  1954年   1篇
排序方式: 共有126条查询结果,搜索用时 15 毫秒
21.
Egglaying aggregations, mate fidelity and male and female mate choice and mating behaviour of the African pyrgomorphid grasshopper Zonocerus elegans are described from the field. Several hundred males and females were individually marked at oviposition sites. Pairs remained stable over days, during egglaying and presumably also over the weeks prior to egglaying. In addition to long-term consorting with a female, males may try to obtain inseminations by “footpad”–tactics at oviposition sites. It is suggested that prolonged consorting and repeated copulations increase the female's reproductive output as well as the male's share in it. Our data and the literature indicate that males are involved not only in rival competition but also in a “battle of the sexes” which females are likely to win. The intra– and intersexual “war on two fronts” results behaviourally in elaborate mating tactics and anatomically in highly developed internal female genitalia and male copulatory organs (well known taxonomic characters). This applies not only to grasshoppers but also to other insects and arthropods.  相似文献   
22.
Amiloride does not alter NaCl avoidance in Fischer-344 rats   总被引:2,自引:2,他引:0  
Fischer-344 (F-344) rats differ from other common rat strains in that they fail to show any preference for NaCl at any concentration in two- bottle preference tests. Because 100 microM amiloride partially blocks the NaCl-evoked chorda tympani (CT) response in electrophysiological studies, we tested NaCl preference (0.068-0.273 M) in F-344 rats with and without 100 microM amiloride solution as the solvent. A third group was tested with unadulterated NaCl solutions following CT transection. Amiloride had no significant effect on the NaCl preference-aversion function, whereas CT transection significantly reduced NaCl avoidance. These results suggest that the amiloride-sensitive component of the NaCl response is not necessary for F-344 rats to display avoidance of NaCl, but the entire CT input is.   相似文献   
23.

Background  

Association testing is a powerful tool for identifying disease susceptibility genes underlying complex diseases. Technological advances have yielded a dramatic increase in the density of available genetic markers, necessitating an increase in the number of association tests required for the analysis of disease susceptibility genes. As such, multiple-tests corrections have become a critical issue. However the conventional statistical corrections on locus-specific multiple tests usually result in lower power as the number of markers increases. Alternatively, we propose here the application of the longest significant run (LSR) method to estimate a region-specific p-value to provide an index for the most likely candidate region.  相似文献   
24.

Background  

Microarray-based pooled DNA experiments that combine the merits of DNA pooling and gene chip technology constitute a pivotal advance in biotechnology. This new technique uses pooled DNA, thereby reducing costs associated with the typing of DNA from numerous individuals. Moreover, use of an oligonucleotide gene chip reduces costs related to processing various DNA segments (e.g., primers, reagents). Thus, the technique provides an overall cost-effective solution for large-scale genomic/genetic research. However, few publicly shared tools are available to systematically analyze the rapidly accumulating volume of whole-genome pooled DNA data.  相似文献   
25.

Background  

Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult.  相似文献   
26.
27.
We have previously described a developmentally regulated mRNA in maize that accumulates in mature embryos and is involved in a variety of stress responses in the plant. The sequence of the encoded 16 kDa protein (MA16) predicts that it is an RNA-binding protein, since it possesses a ribonucleoprotein consensus sequence-type RNA-binding domain (CS-RBD). To assess the predicted RNA binding property of the protein and as a starting point to characterize its function we have used ribohomopolymer-binding assays. Here we show that the MA16-encoded protein binds preferentially to uridine- and guanosine-rich RNAs. In light of these results a likely role for this protein in RNA metabolism during late embryogenesis and in the stress response is discussed.  相似文献   
28.
DNA sequence comparisons of two mitochondrial DNA genes were used to infer phylogenetic relationships among 17 Felidae species, notably 15 in the previously described pantherine lineage. The polymerase chain reaction (PCR) was used to generate sequences of 358 base pairs of the mitochondrial 12S RNA gene and 289 base pairs of the cytochrome b protein coding gene. DNA sequences were compared within and between 17 felid and five nonfelid carnivore species. Evolutionary trees were constructed using phenetic, cladistic, and maximum likelihood algorithms. The combined results suggested several phylogenetic relationships including (1) the recognition of a recently evolved monophyletic genus Panthera consisting of Panthera leo, P. pardus, P. onca, P. uncia, P. tigris, and Neofelis nebulosa; (2) the recent common ancestry of Acinonyx jubatus, the African cheetah, and Puma concolor, the American puma; and (3) two golden cat species, Profelis temmincki and Profelis aurata, are not sister species, and the latter is strongly associated with Caracal caracal. These data add to the growing database of vertebrate mtDNA sequences and, given the relatively recent divergence among the felids represented here (1-10 Myr), allow 12S and cytochrome b sequence evolution to be addressed over a time scale different from those addressed in most work on vertebrate mtDNA.   相似文献   
29.
Zusammenfassung Ei und Gelegegröße von Blennius fluviatilis Asso entsprechen denen anderer Blenniiden; dasselbe gilt für die Anheftung der Eier in einer Schicht an der Decke der Wohnhöhle des Männchens.Die Haftvorrichtung des Eies besteht aus vielen, sehr dicht stehenden Einzelfäden, die mit einer besonderen Wurzel aus der Zona radiata entspringen. Von oben gesehen bilden sie eine Haftscheibe, auf der das Ei sitzt, von der Seite gesehen umgeben sie das Ei an der Basis wie ein Wall, von unten gesehen bilden sie einen Haftring um die zentral gelegene Mikropyle. Vergleiche mit anderen Fischfamilien legen die Vermutung nahe, daß die Struktur des Haftapparates der Eier auch bei den Blenniidae ein systematisch-taxonomisch verwertbares Merkmal ist.Die Zona radiata weist bei Blennius fluviatilis zwei verschiedene Porentypen an den beiden Eipolen auf. Vermutungen über die Funktion der beschriebenen Hofporen ergeben sich aus den Beobachtungen der Embryonalentwicklung. Wahrscheinlich dienen sie der besseren Sauerstoffversorgung des Embryos, dessen Dottersack-Oberfläche dann als Atmungsorgan wirkt.  相似文献   
30.
    
Zusammenfassung Wenn Duettieren bei Vögeln der Revieranzeige und Revierabgrenzung dient, sollte man besondere Duett-Abläufe erwarten, sobald sich Paare — an der Reviergrenze oder im Revier — begegnen. Bislang sind nur wenige solcher Fälle beschrieben. Daß ein Individuum im Duett auf ein anderes als den Paarpartner Bezug nimmt, läßt sich am ehesten erkennen, wenn jedes Paar mehrere motivlich verschiedene Duette singen kann. Entgegen früheren Angaben in der Literatur fanden wir beim OrgelwürgerLaniarius aethiopicus, daß ein Duett-Duell Paar gegen Paar nicht chaotisch verlief. Ein Individuum kann seine Rufe zeitlich und motivlich sowohl auf den Partner abstimmen wie auch auf den gleichgeschlechtlichen Rivalen; Duettbeziehungen zum andersgeschlechtlichen Nachbarn kamen nicht vor, schienen sogar vermieden zu werden.Motivliche Beeinflussung zwischen konterduettierenden Paaren ist für mehrere Arten(Cisticola, Laniarius) nachgewiesen. Sie fehlt dem BartvogelTrachyphonus usambiro, der in jedem Geschlecht nur über ein Motiv verfügt, fehlt aber auch dem Drongo (Günnigmann 1973), obwohl er extrem motivreich duettiert.Solche Analysen scheinen uns vielversprechend für die Beantwortung der Frage nach der biologischen Funktion des Duettierens.
Influences from partner and rival during conter-duetting in birds
Summary Duetting as part of bird's territorial behaviour in some species shows the form of conterduetting between pairs. Such performances can be analyzed with respect of partners versus rivals influencing each other. Influences upon the individual become apparent by its choice of motiv and the timing of its calls with respect to the vocalizations of another bird.For the African tropical boubou,Laniarius aethiopicus, we show that the individual during a conter-duet in fact adresses its calls to its mate and its rival, respectively.Although careful analyses are still lacking for other species, it is apparent from literature that different species differ with respect to these inter-pair influences. A closer analysis might be helpful to get insight into the more subtile functions of duetting in birds.
  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