全文获取类型
收费全文 | 477篇 |
免费 | 35篇 |
国内免费 | 66篇 |
专业分类
578篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 12篇 |
2021年 | 13篇 |
2020年 | 19篇 |
2019年 | 25篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 28篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 11篇 |
2011年 | 29篇 |
2010年 | 22篇 |
2009年 | 25篇 |
2008年 | 23篇 |
2007年 | 32篇 |
2006年 | 20篇 |
2005年 | 19篇 |
2004年 | 20篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 13篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有578条查询结果,搜索用时 15 毫秒
81.
We review winner-loser models, the currently popular explanation for the occurrence of linear dominance hierarchies, via a
three-part approach. (1) We isolate the two most significant components of the mathematical formulation of three of the most
widely-cited models and rigorously evaluate the components’ predictions against data collected on hierarchy formation in groups
of hens. (2) We evaluate the experimental support in the literature for the basic assumptions contained in winner-loser models.
(3) We apply new techniques to the hen data to uncover several behavioral dynamics of hierarchy formation not previously described.
The mathematical formulations of these models do not show satisfactory agreement with the hen data, and key model assumptions
have either little or no conclusive support from experimental findings in the literature. In agreement with the latest experimental
results concerning social cognition, the new behavioral dynamics of hierarchy formation discovered in the hen data suggest
that members of groups are intensely aware both of their own interactions as well as interactions occurring among other members of their group. We suggest that
more adequate models of hierarchy formation should be based upon behavioral dynamics that reflect more sophisticated levels
of social cognition. 相似文献
82.
Shifts in climate regime have provoked substantial trophic‐ and species‐dependent changes within ecosystems. With growing concerns of present global warming, we examined potential lake ecosystem responses, natural hierarchy responses (i.e. immediate responses at lower system levels as opposed to delayed responses at higher system levels), and possible shifts among abiotic (physics, nutrients) and biotic (phytoplankton, zooplankton) system components. Specifically, we analyzed decadal data collected from Müggelsee, a lake in Berlin, Germany, for climate‐induced abiotic and biotic changes, their timing and type, and classified them as abrupt permanent, gradual permanent, abrupt temporary, or monotonic. We further categorized variable changes as a function of system hierarchy, including lake physics (ice, temperature, stratification), nutrients (phosphorus, nitrogen, silicate), plankton, and levels of integration (i.e. species, taxonomic groups, and total plankton). Contrary to current theory, data suggest abrupt responses did not occur in a hierarchy‐dependent manner, nor was a clear pattern observed among functional system‐based categories. Abrupt permanent changes were the most prominent response pattern observed, suggesting they may be driven by large‐scale climatic oscillations and by surpassed thresholds, as noted in previous case studies. Gradual changes coincided with affected abiotic parameters spanning an expansive time range; for example, climatic effects in spring preceded changes in nutrient limitation. Variables displaying no long‐term changes pointed to compensation processes caused by, e.g., simultaneously acting forces of warming trends and climate‐independent changes in trophic state. Nevertheless, the complexity of response patterns at the single system level manifested clear chronological regime shifts in abiotic and biotic parameters in spring and, to a lesser extent, in summer. With regard to projected global warming, the majority of currently unaffected system levels may face impending thermal thresholds, achievement of which would result in an accelerated shift in ecosystem state. 相似文献
83.
Tracey Hunter-Doniger 《Arts Education Policy Review》2017,118(2):83-92
This article argues that the eugenics movement has had three major influences on education in the United States, and reveals how these influences have had an impact on visual arts education in particular. The first influence began with a debate between John Dewey and David Snedden that resulted in a two-tiered tracking system that separated college bound and vocational students. The second is the influence of eugenics on the establishment of the hierarchical framework for the public school curriculum. The third influence of eugenics discussed in this article is its impact on standardized testing. These influences have justified American imperialism in schools, and have led to the marginalization of visual arts education in the United States. 相似文献
84.
非人灵长类雌性等级的研究方法 总被引:1,自引:0,他引:1
在非人灵长类动物等级研究中, 有关判定与描述优势等级方法的选择至关重要。早期对旧大陆灵长类的等级研究主要关注雄性, 对雌性涉猎较少。目前主要应用攻击-屈服、取食、携婴、相互理毛等行为标准来研究灵长类的雌性等级, 也发现不同的物种往往有不同的雌性等级模式。依据社群结构的完整性将其分为线性等级与非线性等级, 并采用不同的方式进行描述。本文通过查阅文献资料, 对雌性等级的研究内容、判定标准以及描述方式进行论述, 以便抛砖引玉提高非人灵长类雌性等级的研究水平。 相似文献
85.
86.
87.
88.
89.
90.
Hannah Gautrey Fergus Nicol Alan A. Sneddon Judith Hall John Hesketh 《Biochimica et Biophysica Acta (BBA)/General Subjects》2011