全文获取类型
收费全文 | 5926篇 |
免费 | 596篇 |
国内免费 | 242篇 |
专业分类
6764篇 |
出版年
2024年 | 12篇 |
2023年 | 72篇 |
2022年 | 93篇 |
2021年 | 143篇 |
2020年 | 195篇 |
2019年 | 199篇 |
2018年 | 209篇 |
2017年 | 172篇 |
2016年 | 215篇 |
2015年 | 248篇 |
2014年 | 266篇 |
2013年 | 282篇 |
2012年 | 196篇 |
2011年 | 231篇 |
2010年 | 230篇 |
2009年 | 331篇 |
2008年 | 360篇 |
2007年 | 351篇 |
2006年 | 262篇 |
2005年 | 283篇 |
2004年 | 244篇 |
2003年 | 215篇 |
2002年 | 200篇 |
2001年 | 173篇 |
2000年 | 190篇 |
1999年 | 163篇 |
1998年 | 150篇 |
1997年 | 116篇 |
1996年 | 124篇 |
1995年 | 99篇 |
1994年 | 110篇 |
1993年 | 81篇 |
1992年 | 76篇 |
1991年 | 66篇 |
1990年 | 64篇 |
1989年 | 61篇 |
1988年 | 56篇 |
1987年 | 40篇 |
1986年 | 34篇 |
1985年 | 34篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有6764条查询结果,搜索用时 15 毫秒
1.
H. DELATTE S. A. JULIANO D. FONTENILLE S. QUILICI 《Medical and veterinary entomology》2013,27(4):387-397
Two invasive, container‐breeding mosquito species, Aedes aegypti (Stegomyia aegypti) and Aedes albopictus (Stegomyia albopicta) (Diptera: Culicidae), have different distribution patterns on Reunion Island. Aedes albopictus occurs in all areas and Ae. aegypti colonizes only some restricted areas already occupied by Ae. albopictus. This study investigates the abiotic and biotic ecological mechanisms that determine the distribution of Aedes species on Reunion Island. Life history traits (duration of immature stages, survivorship, fecundity, estimated finite rate of increase) in Ae. aegypti and Ae. albopictus were compared at different temperatures. These fitness measures were characterized in both species in response to competitive interactions among larvae. Aedes aegypti was drastically affected by temperature, performing well only at around 25 °C, at which it achieved its highest survivorship and greatest estimated rate of increase. The narrow distribution of this species in the field on Reunion Island may thus relate to its poor ability to cope with unfavourable temperatures. Aedes aegypti was also more negatively affected by high population densities and to some extent by interactions with Ae. albopictus, particularly in the context of limited food supplies. Aedes albopictus exhibited better population performance across a range of environmental conditions. Its ecological plasticity and its superior competitive ability relative to its congener may further enhance its invasion success on Reunion Island. 相似文献
2.
M. T. van Wijk§¶ M. Williams L. Gough† S. E. Hobbie‡ G. R. Shaver§ 《Journal of Ecology》2003,91(4):664-676
3.
The cost of interspecific competition in two gerbil species 总被引:5,自引:1,他引:4
4.
1. Simple mechanical models (random walks and the 'gas model') were used to investigate the movement patterns and intergroup encounter rates of a high- and low-density subpopulation of Grey-Cheeked Mangabeys ( Cercocebus albigena johnstoni, Lydeker) at two sites in the Kibale Forest, Western Uganda.
2. Random walk simulations showed that the presence of conspecific groups could act as 'social barriers' which constrained group movements, and promoted high levels of site attachment to a specific home range area.
3. Encounter rate models showed that in the low-density subpopulation (Kanyawara), intergroup encounters occurred no more frequently than expected if groups were moving randomly and independently of each other. This was in contrast to previous analyses which suggested that Grey-Cheeked Mangabeys employed a social spacing mechanism (mediated by male loud calls) in order to reduce the frequency of encounter to below chance levels.
4. Encounters in the high-density subpopulation (Ngogo) were found to occur less frequently than expected at short range (within 100 m). This was suggested to be due to the operation of a territorial mate defence strategy by males at this site. 相似文献
2. Random walk simulations showed that the presence of conspecific groups could act as 'social barriers' which constrained group movements, and promoted high levels of site attachment to a specific home range area.
3. Encounter rate models showed that in the low-density subpopulation (Kanyawara), intergroup encounters occurred no more frequently than expected if groups were moving randomly and independently of each other. This was in contrast to previous analyses which suggested that Grey-Cheeked Mangabeys employed a social spacing mechanism (mediated by male loud calls) in order to reduce the frequency of encounter to below chance levels.
4. Encounters in the high-density subpopulation (Ngogo) were found to occur less frequently than expected at short range (within 100 m). This was suggested to be due to the operation of a territorial mate defence strategy by males at this site. 相似文献
5.
DONALD R. STRONG Jr 《Ecological Entomology》1982,7(2):217-220
Abstract. 1. Adults of rolled-leaf hispine beetles (Chrysomelidae, Coleoptera) spend their lives in the scrolls formed by immature leaves of Heliconia (Heli-coniaceae, Monocotyledonae) in Tropical America. As many as eight hispine species can intermingle in the host scrolls at a single site. Scrolls of single host species are invariably occupied by adults of more than one hispine species, and as many as five species can simultaneously occupy one scroll.
2. I made virgin scrolls, which had never contained any insects, by growing leaves under the cover of plastic bags.
3. Thirty-seven combinations of single hispine and Heliconia species were experimentally created in the virgin scrolls, at two sites and in two seasons, in Costa Rica. Combinations included all abundant host species at the sites.
4. All beetles left all leaves of the twenty-eight unnatural beetle—host combinations, within 24 h. On the other hand, none of the nine natural combinations was completely abandoned within the experimental period.
5. Thus, host specificity is not broader in the absence of similar hispine species that might be competitors, and interspecies competition does not affect this obvious aspect of resource utilization for these phytophagous insects. 相似文献
2. I made virgin scrolls, which had never contained any insects, by growing leaves under the cover of plastic bags.
3. Thirty-seven combinations of single hispine and Heliconia species were experimentally created in the virgin scrolls, at two sites and in two seasons, in Costa Rica. Combinations included all abundant host species at the sites.
4. All beetles left all leaves of the twenty-eight unnatural beetle—host combinations, within 24 h. On the other hand, none of the nine natural combinations was completely abandoned within the experimental period.
5. Thus, host specificity is not broader in the absence of similar hispine species that might be competitors, and interspecies competition does not affect this obvious aspect of resource utilization for these phytophagous insects. 相似文献
6.
7.
8.
9.
1. Larval success was compared when one, two, or three egg clutches were laid in kumquat fruits (≈ 10 ml in volume) either successively on the same day or at the rate of one clutch per day. 2. Increased clutch density was associated with a significant decrease in larval survival rate and non‐significant decreases in larval growth rate and pupal mass. 3. Larval and pupal parameters showed significantly larger variance when clutches were laid on successive days than on the same day, suggesting a competitive advantage for older larvae over younger larvae. 4. The results suggest that, in small fruit, reduced fitness due to larval competition may act against possible fitness benefits due to social facilitation among adult females, hence reducing the likelihood of non‐linear population dynamics caused by processes such as the Allee effect. 相似文献
10.