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   133篇
  免费   13篇
  国内免费   13篇
  2024年   1篇
  2023年   4篇
  2021年   3篇
  2020年   1篇
  2019年   9篇
  2018年   2篇
  2017年   6篇
  2016年   7篇
  2015年   6篇
  2014年   6篇
  2013年   7篇
  2012年   6篇
  2011年   6篇
  2010年   2篇
  2009年   3篇
  2008年   6篇
  2007年   5篇
  2006年   12篇
  2005年   5篇
  2004年   6篇
  2003年   3篇
  2002年   4篇
  2001年   3篇
  2000年   5篇
  1999年   6篇
  1998年   5篇
  1997年   2篇
  1996年   1篇
  1995年   4篇
  1994年   3篇
  1993年   2篇
  1990年   2篇
  1989年   2篇
  1988年   1篇
  1987年   3篇
  1986年   4篇
  1984年   1篇
  1983年   3篇
  1982年   1篇
  1979年   1篇
排序方式: 共有159条查询结果,搜索用时 27 毫秒
61.
62.
The genus Symmerista Hübner (Notodontidae, Nystaleinae) is reviewed for Costa Rica, based on 49 wild-caught specimens. Four species are newly described: Symmerista luisdiegogomezi Chacón, Symmerista inbioi Chacón, Symmerista minaei Chacón and Symmerista aura Chacón. All are from the cloud forests of the Talamanca moutain range, southern Costa Rica. Photographs of the adults, male and female genitalia, and barcodes are also provided. The species Symmerista tlotzin Schaus (1892) is removed from Symmerista and assigned to the genus Elymiotis Walker as a new combination.  相似文献   
63.
Aim To assess the relative importance of climate, biotope and soil variables as well as geographical location for the species richness of plants, butterflies, day‐active macromoths and wild bees in boreal agricultural landscapes. Location A total of 68 agricultural landscapes located in southern Finland. Methods Generalized linear mixed models were used to analyse the effects of environmental (climate, biotope and soil) and spatial (latitude and longitude) variables on species richness of four taxa in 136 study squares of 0.25 km2. Using partial regression, the variation in species richness was decomposed into the purely environmental fraction; the spatially structured environmental fraction; and the purely spatial fraction, including variables retained in cubic trend surface regression. Results Species richness of all taxa was positively correlated with temperature. Species richness of plants and butterflies was also positively correlated with the heterogeneity of landscape. The extent of low‐intensity agricultural land and forest had a positive effect, and the extent of cultivated field a negative effect on the species richness of these taxa. The effect of soil characteristics on the number of observed species was negligible for all taxa. The greatest part of the explained variation for all taxa was accounted for by the pure effect of geographical location. To a somewhat lesser extent, the species richness of plants, butterflies and bees was also related to the effects of spatially structured environmental variables, and the species richness of macromoths to the effects of environmental variables. Main conclusions Multi‐species richness of boreal agricultural landscapes at the scale of 0.25 km2 was associated with the heterogeneity of the local landscape. However, large‐scale geographical variation in species richness was also observed, which indicates the importance of climate and geographical location for the taxa studied. These results highlight the fact that, even on a landscape scale, geographical factors should be taken into account in biodiversity studies. Heterogeneous agricultural landscapes, including forest and non‐crop biotopes, should be preserved or restored to maintain biodiversity.  相似文献   
64.
天津北大港湿地自然保护区蛾类的多样性   总被引:6,自引:0,他引:6  
尤平  李后魂  王淑霞 《生态学报》2006,26(4):999-1004
湿地是一种特殊的土地资源和生态环境,具有调节水分循环、维持湿地特有动植物(尤其是作为水禽栖息地)等基本生态功能.天津北大港湿地自然保护区位于天津市东南部,是目前天津市最大的湿地自然保护区.湿地资源丰富,是亚太地区鸟类迁徙路线的一个重要环节,也是白枕鹤、丹顶鹤等濒危鸟类迁徙过程中的一个重要的停歇地.为了研究清楚北大港自然保护区灯下蛾类的种类及其动态规律,筛选出能反映湿地状况和动态的指示性昆虫,为湿地的研究和保护利用服务,于2001年6月12日到10月14日和2002年4月12日到10月30日采用灯诱法系统调查研究了天津北大港湿地自然保护区的蛾类,以微软系统的Excel列表、作图,进行蛾类群落的种-多度曲线作图及群落多样性(H′)、均匀度(J′)、物种丰富度(S)和个体数(N)的时间和空间分布.并利用蛾类群落的种-多度曲线、多样性指数、均匀度与多样性指数的关系等对其作了分析.结果表明,北大港湿地蛾类已知17科105 属 132种,以夜蛾科和草螟科的种类为多.蛾类群落种-多度关系符合生态位优先占领模型.多样性指数与均匀度不相一致(r=0.21),而与物种丰富度一致(r=0.90).这是由于北大港湿地蛾类种-多度关系表现为生态位优先占领假说的缘故.研究认为北大港湿地自然保护区的蛾类种类较少,群落不稳定,即北大港湿地蛾类赖以生存的生态环境不稳定.有待于进一步保护和改善.  相似文献   
65.
You P  Li H H 《农业工程》2006,26(4):999-1003
North Dagang Wetland Nature Reserve is situated in the southeast of Tianjin, China. It is the biggest wetland nature reserve in Tianjin. An investigation into the diversity of the moth community was carried out from June 12 to October 14, 2001, and then from April 12 to October 30, 2002. The investigation was conducted in order to identify the moth species in wetlands, study their dynamic laws, select indicator insects to indicate wetland quality, and assist in the study and protection of wetlands. A total of 132 moth species were collected, which belonged to 105 genera in 17 families. The data about insects which was collected during the survey was listed and constructed in terms of species-abundance, indices of diversity (H′), evenness (J′), specific richness (S) and individual number (N) using the Microsoft Excel Program. The status of the wetlands was also analyzed using the moth community species-abundance curve, indices of diversity, the connection between evenness and richness indices, etc. The results show that moth species in the wetlands were not rich, and the moth community was unstable. In other words, the living environment of the moths and the environmental quality of the wetlands were unstable due to the serious degeneration of the wetland environment and human activities.  相似文献   
66.
Moths and butterflies flying in search of mates risk detection by numerous aerial predators; under the cover of night, the greatest threat will often be from insectivorous bats. During such encounters, the toxic dogbane tiger moth, Cycnia tenera uses the received intensity, duration and emission pattern of the bat''s echolocation calls to determine when, and how many, defensive ultrasonic clicks to produce in return. These clicks, which constitute an acoustic startle response, act as warning signals against bats in flight. Using an integrated test of stimulus generalization and dishabituation, here we show that C. tenera is able to discriminate between the echolocation calls characteristic of a bat that has only just detected it versus those of a bat actively in pursuit of it. We also show that C. tenera habituates more profoundly to the former stimulus train (‘early attack’) than to the latter (‘late attack’), even though it was initially equally responsive to both stimuli. Matched sensory and behavioural data indicate that reduced responsiveness reflects habituation and is not merely attributable to sensory adaptation or motor fatigue. In search of mates in the face of bats, C. tenera''s ability to discriminate between attacking bats representing different levels of risk, and to habituate less so to those most dangerous, should function as an adaptive cost–benefit trade-off mechanism in nature.  相似文献   
67.
Aim An increase in multivoltinism in ectothermic animals has been proposed by several authors as a possible outcome of climate warming, especially in high latitudes. We tested this prediction with large‐scale empirical monitoring data for boreal moth communities. Location Finland, northern Europe. Methods Our data set comprised observations of multivoltine species made in the Finnish moth monitoring scheme ‘Nocturna’ trap sites during the period 1993–2006 along an exceptionally long latitudinal gradient of 1000 km. To compare recent changes in moth multivoltinism with a longer time period, we gathered older time series of moth observations from five locations. We used generalized linear mixed models (GLMMs) to detect possible temporal and geographical trends in the annual occurrence of multivoltinism. We also identified areas where the recent changes in multivoltinism have been greatest. Monthly average temperatures of spring and summer periods and annual sum of growing degree days above 5 °C (GDD5) were used as explanatory variables to distinguish the main climatic correlates of moth multivoltinism. Results We observed a clear increase in the occurrence of moth multivoltinism during the period 1993–2006. The incidence as well as the recent increase in multivoltinism were highest in southernmost Finland and decreased towards the north. We also detected a weaker, although significantly positive, trend of moth multivoltinism in southern Finland during the period 1963–92, suggesting that this increasing trend might already have begun earlier. The most important climatic correlates for the annual occurrence of moth multivoltinism were the mean summer temperature (periods May–July and June–August) and GDD5, but all the tested climatic variables showed a significant univariate relationship with the occurrence of moth multivoltinism. All climatic variables showed an increasing trend during the period 1993–2006. Main conclusions The occurrence of multivoltinism has increased in northern European moth communities during recent decades, apparently as a response to increasing temperatures during the spring and summer seasons. The increase in multivoltinism was greatest in the southernmost parts of Finland, whereas in the northern landscapes recent warming has triggered multivoltinism in only relatively few moth species.  相似文献   
68.
69.
Morphological adaptations to sphingophily and pollination by moths was studied in 5 South American Habenaria species. For H. gourlieana and H. hieronymi direct evidence of hawkmoth (Agrius cingulatus and Manduca sexta) and settling moth (Rachiplusia nu) pollination, respectively, by hemipollinaria attachment on the eyes, is presented. In two other species (H. paucofilia, H. rupicola) pollination by settling moths and eye attachment of the hemipollinaria can be inferred by indirect evidence (placement of scales and massulae on the flowers) and by flower structure. For the fifth species (H. montevidensis) pollination by small moths or mosquitoes with hemipollinaria attachment on the proboscis is postulated. A comparative study in floral features revealed clear morphological divergence between sphingophilous and phalaenophilous species. In addition to deeper spurs the former have slender, exerted, and upturned petal lobes (acting as mechanical guide to the hovering visitors), a much developed median rostellar lobe (acting as deflecting surface of the hawkmoths towards the viscidia), flexible and sinuous hemipollinarium caudicles (appropriate for frontal strikes against the stigma when hemipollinaria are brought by the hawkmoths dangling against the flower). Male efficiency was compared between 4 species with overlapping flowering time in the same area. Male efficiency factors were unexpectedly low in all species. Only in one species (H. hieronymi) each pollen donation accounted for more than one pollination. H. gourlieana is part of a more or less rich sphingophilous flora interacting with the same two long-tongued hawkmoth species. Interspecific competition for pollen placement on the pollinator's body surface is probably low on account of different pollination mechanisms.  相似文献   
70.
Pyrrolizidine alkaloids (PA) have been identified in six species of Arctiidae reared on Senecio and Crotalaria. These include senecionine, seneciphylline, integerrimine, jacobine, jacozine, jacoline, jaconine and a metabolite (C15H25NO5) from Senecio , and monocrotaline, trichodesmine and crispatine from Crotalaria.
The all-red aberration of Tyria jacobaeae (var. conyi) contained much less of the metabolite than normal examples of this species. Female Spilosoma lutea reared on the same plants of S. jacobaea contained markedly more jacobine and jacoline than die males.
Host plant relationships and secondary plant substances are discussed. It is suggested that the Arctiid moths' own deterrent secretions, directed against vertebrate predators, pre-adapts them for feeding on foliage likewise protected against large herbivores by toxic secondary plant substances such as cardenolides and pyrrolizidine alkaloids. These latter substances are more toxic to vertebrate than to insect herbivores, and their dual function of deterrent and insect aphrodisiac puts a premium on their sequestration and storage once a species has achieved the initial steps, and occupied the plant niche concerned. It is further suggested that the polyphagous habits of the Arctiidae result in a more equitable distribution of die secondary plant substances within the Mullerian complex concerned, thus providing a generalized warning message for the potential vertebrate predator.  相似文献   
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