全文获取类型
收费全文 | 857篇 |
免费 | 3篇 |
国内免费 | 3篇 |
专业分类
安全科学 | 16篇 |
废物处理 | 16篇 |
环保管理 | 134篇 |
综合类 | 269篇 |
基础理论 | 149篇 |
污染及防治 | 200篇 |
评价与监测 | 47篇 |
社会与环境 | 25篇 |
灾害及防治 | 7篇 |
出版年
2020年 | 7篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 20篇 |
2013年 | 68篇 |
2012年 | 23篇 |
2011年 | 31篇 |
2010年 | 23篇 |
2009年 | 22篇 |
2008年 | 33篇 |
2007年 | 35篇 |
2006年 | 19篇 |
2005年 | 21篇 |
2004年 | 35篇 |
2003年 | 19篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 13篇 |
1999年 | 18篇 |
1998年 | 8篇 |
1997年 | 12篇 |
1996年 | 17篇 |
1995年 | 12篇 |
1994年 | 25篇 |
1993年 | 7篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1988年 | 6篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1968年 | 6篇 |
1965年 | 6篇 |
1964年 | 9篇 |
1963年 | 6篇 |
1962年 | 6篇 |
1961年 | 6篇 |
1960年 | 8篇 |
1959年 | 11篇 |
1957年 | 7篇 |
1956年 | 11篇 |
1954年 | 9篇 |
1939年 | 6篇 |
1924年 | 6篇 |
排序方式: 共有863条查询结果,搜索用时 15 毫秒
821.
822.
823.
Paula C. Díaz Christoph Grüter Walter M. Farina 《Behavioral ecology and sociobiology》2007,61(10):1589-1597
Floral scents are important information cues used to organize foraging-related tasks in honeybees. The waggle dance, apart
from encoding spatial information about food sources, might facilitate the transfer of olfactory information by increasing
the dissipation of volatiles brought back by successful foragers. By assuming that food scents are more intensive on specific
body parts of returning foragers, i.e., the posterior legs of pollen foragers and mouthparts of nectar foragers, we quantified
the interactions between hive mates and foragers during dances advertising different types of food sources. For natural sources,
a higher proportion of hive mates contacted the hind legs of pollen dancers (where the pollen loads were located) with their
heads compared to non-pollen dancers. On the other hand, the proportion of head-to-head contacts was higher for non-pollen
foragers during the waggle runs. When the food scent was manipulated, dancers collecting scented sugar solution had a higher
proportion of head-to-head contacts and a lower proportion around their hind legs compared to dancers collecting unscented
solution. The presence of food odors did not affect in-hive behaviors of dancers, but it increased the number of trophallaxes
in-between waggle runs (i.e., during circle phases). These results suggest that the honeybee dance facilitates the olfactory
information transfer between incoming foragers and hive mates, and we propose that excitatory displays in other social insect
species serve the same purpose. While recent empirical and theoretical findings suggested that the colony level foraging benefits
of the spatial information encoded in the waggle dance vary seasonally and with habitats, the role of the dance as a compound
signal not only indicating the presence of a profitable resource but also amplifying the information transfer regarding floral
odors may be important under any ecological circumstances. 相似文献
824.
825.
826.
Alate trapping studies of a monogyne population of the fire ant Solenopsis geminata indicate that two sizes of gynes are produced. Macrogynes, which participate in late spring and summer mating flights, are larger, fattier, and more than twice as heavy as microgynes, which participate in fall mating flights. Three patterns of gyne production were observed in 51 colonies studied: 35 produced macrogynes only, 9 produced microgynes only, and 7 produced both morphs, contributing to both summer and fall mating flights. Behavioral evidence and rearing studies suggest that macrogynes found new colonies independently, whereas microgynes achieve colony queen status by infiltrating or being adopted by established colonies. Of the total number of female alates collected from the trapped colonies, 56% were microgynes. However, because of their smaller size and lower fat content, microgynes made up only one-third of the caloric investment in female alates. By measuring the thorax lengths of queens from mature colonies, we determined that at least 56% were macrogynes and 35% or more were microgynes. These results indicate that as a reproductive strategy, colony investment in microgyne production may have at least as high a payoff as investment in macrogyne production.This is publication #24 of the Fire Ant Research Team 相似文献
827.
828.
Gary D. Lynne J. Walter Milon Michael E. Wilson 《Journal of the American Water Resources Association》1990,26(4):669-676
ABSTRACT: Scarcity combined with differences in values, beliefs, and attitudes can lead to behavior differences and conflicts over water. This paper develops an index for measuring potential conflict using survey information about water attitudes and beliefs of individuals in three groups in a Florida case study. The index helps in assessing the current capability of the institution to reduce conflict. The results suggest that the current institution is effective, but changes may help to streamline the consumptive-use permitting process, to improve educational programs, and to seek improved institutional arrangements to reduce future conflict over economic uses of water. 相似文献
829.
830.