全文获取类型
收费全文 | 342篇 |
免费 | 23篇 |
国内免费 | 10篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 4篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 18篇 |
2013年 | 37篇 |
2012年 | 12篇 |
2011年 | 10篇 |
2010年 | 13篇 |
2009年 | 21篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 15篇 |
2005年 | 17篇 |
2004年 | 14篇 |
2003年 | 10篇 |
2002年 | 13篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 9篇 |
1993年 | 3篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有375条查询结果,搜索用时 437 毫秒
61.
Pouncing spider, flying mosquito: blood acquisition increases predation risk in mosquitoes 总被引:2,自引:1,他引:1
Female mosquitoes dramatically increase their mass when bloodfeeding on their hosts. Such an increase could impact mosquitomortality risk by reducing escape speed and/or agility. We usedtwo laboratory-based experiments to test this notion. In thefirst, we allowed mature female Anopheles gambiae mosquitoesto feed from 0 to 4 min and then attacked those females withan artificial predator. We videotaped subsequent escape responseof each mosquito. Analysis of those responses clearly demonstratedan inverse relationship between increased mass and escape speed.In the second experiment, we exposed both blood-engorged andunfed A.gambiae females to single zebra spiders (Salticus scenicus)in small plexiglass cages. Here, we focused on mosquito escapesfrom searching and pouncing spiders. We found that engorgedmosquitoes were three times less likely to escape searchingspiders compared to unfed conspecifics. Thus we conclude thatblood feeding has substantial state-dependent risk both at thehost (experiment 1) and after feeding (experiment 2). Such riskcan be extended to a broad range of taxa. 相似文献
62.
Abstract In the dry eucalypt forests of north‐eastern New South Wales, Australia, cattle grazing occurs at low intensities and is accompanied by frequent low‐intensity burning. This study investigated the combined effects of this management practice on the ground‐dwelling and arboreal (low vegetation) spider assemblages. Spiders were sampled at 49 sites representing a range of grazing intensities, using pitfall trapping, litter extraction and sweep sampling. A total of 237 spider morphospecies from 37 families were collected using this composite sampling strategy. The abundance, richness, composition and structure of spider assemblages in grazed and ungrazed forest sites were compared and related to a range of environmental variables. Spider assemblages responded to a range of environmental factors at the landscape, habitat and microhabitat scales. Forest type, spatial relationships and habitat variability at the site scale were more important in determining spider assemblages than localized low‐intensity grazing and burning. However, it is possible that a threshold intensity of grazing may exist, above which spiders respond to grazing and burning. Although low‐intensity grazing and burning may not affect spider assemblages below a threshold stocking rate, that stocking rate has yet to be established. 相似文献
63.
The biodiversity research expedition TAN0204 with RS Tangaroa to the Ross Sea in 2004 yielded a new collection of 2,687 specimens of pycnogonids. As much as 25 different species encompassing
14 genera and eight families were identified and their records are discussed herein. The collection is archived in the Marine
Invertebrate Collection of the New Zealand National Institute of Water and Atmospheric Research (NIWA). The majority (69%)
of specimens are from the Nymphon australe group (Nymphonidae), although species richness and abundance varied among the stations sampled. The collection includes several
specimens from polymerous taxa; Pentanymphon antarcticum (Nymphonidae), Decolopoda australis (Colossendeidae) and Pentapycnon bouvieri (Pycnogonidae). All species were classified based on morphological characters, and DNA sequences (from the 18S, 12S, 16S
and COI regions) for 21 of the representative morphotypes are given. The DNA sequences confirmed the species-level distinctiveness
of these morphotypes. No species new to science were identified, although further detailed morphometric and/or molecular analyses
may reveal cryptic or sibling species, especially in species such as the highly abundant Nymphon australe group.
An erratum to this article can be found at 相似文献
64.
In some animal groups males may be several times smaller than females. One of the hypotheses proposed to explain the evolution of this extreme sexual size dimorphism (SSD) is the differential mortality model (DMM), which is based on the assumption that when males are the searching sex, higher male mortality relaxes male–male contest competition, leading to the adaptive evolution of early‐maturing, small males that are favoured by viability selection. Evidence for the main prediction of this model, i.e. that there is a negative relationship between differential mortality and SSD, has remained elusive. Using sex differences in pitfall trap catches – a proxy of sex differences in mobility and mortality – across 40 spider species, and using the evolutionary comparative method, we found significant negative relationships between differential mortality and SSD for three size traits. Thus, the DMM can still explain part of the observed variance in SSD. 相似文献
65.
66.
蜘蛛对茶园害虫控制作用的研究 总被引:4,自引:1,他引:4
1981年以来,湖南省兰岭茶园开展了大面积以保护茶园蜘蛛为主的茶园害虫综合防治技术研究。近10年来未打化学农药,4年未施化学肥料。试验结果表明,这些措施不但使以蜘蛛为主的茶虫天敌的种类增多、种群数量上升,而且使茶园内主要害虫的种群数量逐年下降;茶叶内不含任何农药残毒,产品达到国家AA级绿色食品要求;经济效益得到成倍增加。 相似文献
67.
本文报道了蜘蛛目巨蟹蛛科异足蛛属1中国新记录种:奥氏异足蛛Heteropoda onoi Jager,2008。该标本采自中国海南岛,标本保存于湖北大学生命科学学院动物行为与进化中心。 相似文献
68.
Charlène Puzin Boris Leroy Julien Pétillon 《Biological journal of the Linnean Society. Linnean Society of London》2014,113(1):85-96
Discriminating closely related species can become a taxonomical challenge if a clear morphological diagnosis is lacking. Two subspecies have been recognized in Pardosa agrestis (Westring, 1861); however, their validity is still debated. To resolve this dilemma, quantitative and qualitative traits were measured for 30 females and 30 males per site from ten localities throughout Western Europe (11 measurements on each individual) and compared between subspecies. Mean annual temperature and geographical coordinates from all sites were also included in the statistical models in order to test for variations in size over the distribution range of each subspecies. We found significant differences in body size and size of copulatory organs as well as accurate criteria of discrimination between P. a. agrestis and P. a. purbeckensis F.O.P. Cambridge, 1895, suggesting that these taxa are two valid morphological species, occurring sympatrically. We also showed that temperatures did not directly influence the size of individuals, but that one species had smaller individuals at higher latitudes (following the converse Bergmann's rule), and that both species had larger individuals in centrally sampled populations (fitting to the centre hypothesis). © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 85–96. 相似文献
69.
J. M. Schneider M. E. Herberstein F. C. De Crespigny S. Ramamurthy M. A. Elgar 《Journal of evolutionary biology》2000,13(6):939-946
Sexual selection, through female choice and/or male–male competition, has influenced the nature and direction of sexual size dimorphism in numerous species. However, few studies have examined the influence of sperm competition on size dimorphism. The orb‐web spider Nephila edulis has a polygamous mating system and extreme size dimorphism. Additionally, the frequency distribution of male body size is extremely skewed with most males being small and few large. The duration of copulation, male size and sexual cannibalism have been identified as the significant factors determining patterns of sperm precedence in spiders. In double mating trials, females were assigned to three treatments: either they mated once with both males or the first or the second male was allowed to mate twice. Paternity was strongly associated with the duration of copulation, independent of mating order. Males that were allowed to mate twice not only doubled the duration of copulation but also their paternity. Small males had a clear mating advantage, they copulated longer than large males and fertilized more eggs. Males of different sizes used different tactics to mate. Large males were more likely to mate through a hole they cut into the web, whereas small males approached the female directly. Furthermore, small males usually mated at their first attempt but large males required several attempts before mating took place. There was no obvious female reaction towards males of different sizes. 相似文献
70.
The impact of dimethoate on the spatial distribution of beneficial arthropods in winter wheat 总被引:3,自引:0,他引:3
The within‐field spatial distribution of beneficial arthropods was assessed using two‐dimensional grids of pitfall traps and suction sampling across two winter wheat fields of 4 and 16 ha, before and after an application of dimethoate. An unsprayed 6 m wide buffer zone was left around half the edge of the larger field. Arthropod numbers fluctuated to varying extents prior to spraying. Two species of Carabidae (Pterostichus madidus and P. melanarius), Linyphiidae, Lycosidae and Aphidius spp. (Braconidae) all showed their greatest reduction after spraying. For five carabid taxa, Tachyporus spp. (Staphylinidae) and Collembola the decline in numbers following spraying was no greater than any reduction found during the pre‐spraying period. Within field spatial distributions of three arthropod groups were analysed using SADIE. P. madidus, present in patches across the centre of both fields prior to spraying, was removed by dimethoate and by 34 days after spraying had recovered most at the field edges. Linyphiidae were evenly distributed across both fields prior to spraying. Their numbers were reduced considerably by dimethoate and they did not recover to pre‐spray levels. However, where recovery occurred this was across the centre of both fields indicating their potential to reinvade whole fields. Aphidius species were also evenly distributed across both fields prior to spraying, but did not recover after spraying. Some, but not all arthropods survived within the unsprayed buffer zone and there was some indication that reinvasion of the mid‐field was more extensive where this was present. The importance of field margins with respect to insecticide treatments is discussed. 相似文献