全文获取类型
收费全文 | 6299篇 |
免费 | 675篇 |
国内免费 | 17篇 |
出版年
2021年 | 109篇 |
2020年 | 49篇 |
2019年 | 53篇 |
2018年 | 70篇 |
2016年 | 120篇 |
2015年 | 169篇 |
2014年 | 204篇 |
2013年 | 270篇 |
2012年 | 344篇 |
2011年 | 349篇 |
2010年 | 195篇 |
2009年 | 175篇 |
2008年 | 203篇 |
2007年 | 272篇 |
2006年 | 246篇 |
2005年 | 198篇 |
2004年 | 207篇 |
2003年 | 241篇 |
2002年 | 194篇 |
2001年 | 230篇 |
2000年 | 196篇 |
1999年 | 165篇 |
1998年 | 85篇 |
1997年 | 73篇 |
1996年 | 76篇 |
1995年 | 84篇 |
1994年 | 72篇 |
1993年 | 66篇 |
1992年 | 121篇 |
1991年 | 112篇 |
1990年 | 114篇 |
1989年 | 95篇 |
1988年 | 107篇 |
1987年 | 99篇 |
1986年 | 70篇 |
1985年 | 102篇 |
1984年 | 74篇 |
1983年 | 72篇 |
1982年 | 56篇 |
1980年 | 56篇 |
1979年 | 81篇 |
1978年 | 82篇 |
1977年 | 52篇 |
1976年 | 65篇 |
1975年 | 72篇 |
1974年 | 64篇 |
1973年 | 62篇 |
1972年 | 64篇 |
1971年 | 53篇 |
1969年 | 53篇 |
排序方式: 共有6991条查询结果,搜索用时 15 毫秒
941.
942.
943.
Central neural mechanisms for detecting second-order motion. 总被引:7,自引:0,他引:7
C L Baker 《Current opinion in neurobiology》1999,9(4):461-466
Single-unit neurophysiology and human psychophysics have begun to reveal distinct neural mechanisms for processing visual stimuli defined by differences in contrast or texture (second-order motion) rather than by luminance (first-order motion). This processing begins in early visual cortical areas, with subsequent extrastriate specialization, and may provide a basis for form-cue invariant analyses of image structure, such as figure-ground segregation and detection of illusory contours. 相似文献
944.
945.
946.
947.
948.
949.
The effects of olfactory stimulation on the behavior of captive ring‐tailed lemurs (Lemur catta)
下载免费PDF全文
![点击此处可从《Zoo biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ring‐tailed lemurs reside in many animal collections worldwide. Lemur welfare may be a cause of concern due to some captive individuals exhibiting stereotypic behavior. Despite these concerns, there has been little exploration of methods of environmental enrichment for ring‐tailed lemurs. Olfactory stimulation can enhance captive animal welfare by encouraging species‐typical behaviors, enhancing behavioral diversity, and decreasing stereotypic behaviors. We aimed to investigate the effects of olfactory stimulation via lavender, peppermint, coconut, and prey odor upon the behavior of eight captive ring‐tailed lemurs. We exposed the lemurs to six individual odor conditions (odor control, novel object control, lavender, peppermint, coconut, and Morio worms) and observed them for 4 hr a day for 3 days with an intervening period of 4 days between conditions. We recorded the lemurs’ behavior under each condition using instantaneous scan sampling. We found significant effects of olfactory stimulation on the ring‐tailed lemurs’ behavior in the initial analysis but these did not survive correction for multiple testing. Overall, while our findings are suggestive of a general effect of olfactory stimulation on the captive ring‐tailed lemurs they did not indicate a marked influence of olfactory condition. However, further investigation with a larger sample size and more biologically relevant odors may be beneficial to fully examine potential effects of olfactory stimulation in captive lemurs. 相似文献
950.