全文获取类型
收费全文 | 765449篇 |
免费 | 87225篇 |
国内免费 | 504篇 |
出版年
2018年 | 6624篇 |
2016年 | 9185篇 |
2015年 | 12055篇 |
2014年 | 14292篇 |
2013年 | 20884篇 |
2012年 | 23178篇 |
2011年 | 23392篇 |
2010年 | 15973篇 |
2009年 | 14791篇 |
2008年 | 20806篇 |
2007年 | 21498篇 |
2006年 | 20169篇 |
2005年 | 19599篇 |
2004年 | 19256篇 |
2003年 | 18744篇 |
2002年 | 18021篇 |
2001年 | 35491篇 |
2000年 | 35450篇 |
1999年 | 28113篇 |
1998年 | 9487篇 |
1997年 | 10119篇 |
1996年 | 9523篇 |
1995年 | 8824篇 |
1994年 | 8652篇 |
1993年 | 8642篇 |
1992年 | 22971篇 |
1991年 | 22193篇 |
1990年 | 21468篇 |
1989年 | 21025篇 |
1988年 | 19469篇 |
1987年 | 18445篇 |
1986年 | 17281篇 |
1985年 | 17194篇 |
1984年 | 14262篇 |
1983年 | 12280篇 |
1982年 | 9399篇 |
1981年 | 8687篇 |
1980年 | 8098篇 |
1979年 | 13826篇 |
1978年 | 10707篇 |
1977年 | 10049篇 |
1976年 | 9243篇 |
1975年 | 10117篇 |
1974年 | 11079篇 |
1973年 | 10783篇 |
1972年 | 9972篇 |
1971年 | 9041篇 |
1970年 | 7826篇 |
1969年 | 7605篇 |
1968年 | 7019篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
961.
962.
963.
964.
965.
Ho WW Fernandes CC Alves-Gomes JA Smith GT 《Ethology : formerly Zeitschrift fur Tierpsychologie》2010,116(11):1050-1064
The South American weakly-electric knifefish (Apteronotidae) produce highly diverse and readily quantifiable electrocommunication signals. The electric organ discharge frequency (EODf), and EOD modulations (chirps and gradual frequency rises (GFRs)), vary dramatically across sexes and species, presenting an ideal opportunity to examine the proximate and ultimate bases of sexually dimorphic behavior. We complemented previous studies on the sexual dimorphism of apteronotid communication signals by investigating electric signal features and their hormonal correlates in Apteronotus bonapartii, a species which exhibits strong sexual dimorphism in snout morphology. Electrocommunication signals were evoked and recorded using a playback paradigm, and were analyzed for signal features including EOD frequency and the structure of EOD modulations. To investigate the androgenic correlates of sexually dimorphic EOD signals, we measured plasma concentrations of testosterone and 11-ketotestosterone. A. bonapartii responded robustly to stimulus playbacks. EODf was sexually monomorphic, and males and females produced chirps with similar durations and amounts of frequency modulation. However, males were more likely than females to produce chirps with multiple frequency peaks. Sexual dimorphism in apteronotid electrocommunication signals appears to be highly evolutionarily labile. Extensive interspecific variation in the magnitude and direction of sex differences in EODf and in different aspects of chirp structure suggest that chirp signals may be an important locus of evolutionary change within the clade. The weakly-electric fish represent a rich source of data for understanding the selective pressures that shape, and the neuroendocrine mechanisms that underlie, diversity in the sexual dimorphism of behavior. 相似文献
966.
967.
Nimra Khan Dylan Pelletier Thomas S. McAlear Nathalie Croteau Simon Veyron Andrew N. Bayne Corbin Black Muneyoshi Ichikawa Ahmad Abdelzaher Zaki Khalifa Sami Chaaban Igor Kurinov Gary Brouhard Susanne Bechstedt Khanh Huy Bui Jean-François Trempe 《Structure (London, England : 1993)》2021,29(6):572-586.e6
- Download : Download high-res image (220KB)
- Download : Download full-size image
968.
969.
Summary Responses of lentil in unsterile soils at low, medium and high levels of plant available soil P toGlomus fasciculatum inoculation were evaluated. It was observed that growth, dry matter accumulation, nodulation, and nitrogen fixation were considerably improved in VAM inoculated plants over uninoculated control at low and medium levels of plant available soil P. 相似文献
970.