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   6928篇
  免费   681篇
  国内免费   3篇
  2024年   7篇
  2023年   67篇
  2022年   132篇
  2021年   279篇
  2020年   155篇
  2019年   227篇
  2018年   183篇
  2017年   192篇
  2016年   301篇
  2015年   517篇
  2014年   564篇
  2013年   585篇
  2012年   745篇
  2011年   668篇
  2010年   382篇
  2009年   330篇
  2008年   421篇
  2007年   381篇
  2006年   321篇
  2005年   286篇
  2004年   245篇
  2003年   168篇
  2002年   146篇
  2001年   31篇
  2000年   14篇
  1999年   26篇
  1998年   13篇
  1997年   15篇
  1996年   12篇
  1995年   9篇
  1994年   6篇
  1992年   11篇
  1991年   7篇
  1990年   6篇
  1988年   10篇
  1985年   6篇
  1984年   6篇
  1983年   5篇
  1982年   6篇
  1981年   6篇
  1980年   10篇
  1979年   9篇
  1978年   6篇
  1977年   9篇
  1976年   7篇
  1974年   5篇
  1973年   8篇
  1972年   7篇
  1969年   5篇
  1912年   5篇
排序方式: 共有7612条查询结果,搜索用时 15 毫秒
991.
An important goal in foraging ecology is to determine how biotic and abiotic variables impact the foraging decisions of wild animals and how they move throughout their multidimensional landscape. However, the interaction of food quality and feeding competition on foraging decisions is largely unknown. Here we examine the importance of food quality in a patch on the foraging decisions of wild vervet monkeys (Chlorocebus pygerythrus) at Lake Nabugabo, Uganda using a multidestination platform array. The overall nutritional composition of the vervet diet was assessed and found to be low in sodium and lipids, thus we conducted a series of experimental manipulations in which the array was varied in salt and oil content. Although vervets prioritized platforms containing key nutrients (i.e., sodium and lipids) overall, we found that solitary vervets prioritized nutrient‐dense platforms more strongly than competing vervets. This finding was opposite to those in a similar experiment that manipulated food site quantity, suggesting that large, salient rewards may be worth competing over but slight differences in nutritional density may be only chosen when there are no potentially negative social consequences (i.e., aggression received). We also found that vervets chose platforms baited with oil‐only, and oil combined with salt, but not salt‐only, suggesting that energy was an important factor in food choice. Our findings demonstrate that when wild vervets detect differences in feeding patches that reflect nutritional composition, they factor these differences into their navigational and foraging decisions. In addition, our findings suggest that these nutritional differences may be considered alongside social variables, ultimately leading to the complex strategies we observed in this study.  相似文献   
992.
993.
994.
995.
This essay reveals a financial dimension to Captain John Blake and his son John Bradby Blake's involvement with China, namely, their participation in financing the Canton trade through predatory loans to Chinese Hong merchants. Widespread predatory lending in Canton led to a financial crisis during the late 1770s, which ruined several British and Chinese merchants. In an effort to recover the money they claimed was owed to them, many British traders, including John Blake, formed a lobby group in London and authorized Britain's first Ambassador to China to negotiate with the Emperor in Beijing on their behalf.  相似文献   
996.
997.
998.
To preserve biodiversity, identifying at‐risk populations and developing conservation plans to mitigate the effects of human‐induced rapid environmental change (HIREC) are essential. Changes in diet, especially for food‐limited species, can aid in detecting populations being impacted by HIREC, and characterizing the quality, abundance, and temporal and spatial consistency of newly consumed food items may provide insight concerning the likelihood of a species persisting in a changing environment. We used Wood Storks (Mycteria americana) nesting in the Florida Everglades as a model system to study the possible effects of HIREC on a food‐limited population. We compared the diets of Wood Storks in 2013 and 2014 with those reported during the 1970s before major anthropogenic activities affected the Everglades system and prey availability. Wood Storks in our study consumed more large‐bodied sunfish species (Lepomis spp.), fewer native marsh fishes, and more non‐native fish species than during the 1970s. Large sunfish and non‐native fish are relatively rare in the drying pools of Everglades marshes where storks traditionally forage, suggesting that Wood Storks may be using novel foraging habitats such as created wetlands (i.e., canals and stormwater ponds). Although created wetlands have long hydroperiods conducive to maintaining large‐bodied fishes and could provide alternative foraging habitat when prey availability is reduced in natural marshes, additional studies are needed to determine the extent to which these wetlands are used by Wood Storks and, importantly, the quality of prey items potentially available to foraging Wood Storks in created wetlands.  相似文献   
999.
1000.
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