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   55篇
  国内免费   1篇
  完全免费   6篇
  2022年   1篇
  2019年   1篇
  2017年   4篇
  2016年   1篇
  2013年   1篇
  2012年   2篇
  2011年   5篇
  2010年   2篇
  2009年   8篇
  2008年   4篇
  2007年   4篇
  2006年   5篇
  2004年   1篇
  2003年   3篇
  2002年   1篇
  2001年   2篇
  2000年   1篇
  1999年   1篇
  1998年   2篇
  1997年   2篇
  1996年   5篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1979年   2篇
排序方式: 共有62条查询结果,搜索用时 84 毫秒
1.
The interspawning interval of female sand gobies, Pomatoschistusminutus, a batch-spawning fish with paternal care, was significantlyshorter when the fish were fed daily than when they were fedevery fourth day. The incubation time of males was not affectedby feeding, nor was the interbrood interval Males have an equalor higher potential reproductive rate than females. As femalesreproduce more slowly when food is scarce than when it is abundant,and males do not, the difference between the sexes in potentialreproductive rate increases when there is food shortage. Becauseof this difference, both male bias in operational sex ratioand intensity in male-male competition for mates are predictedto increase as food availability decreases. Furthermore, a tradeoffbetween current and future reproduction is demonstrated to operateonly when resources are limited, because the correlation betweenegg number of the first and second clutch was positive amonghigh-food females but negative among low-food females. The numberof eggs per female clutch did, however, not differ between treatmentsin first or second dutch. I conclude that operational sex ratioand sexual selection are expected to vary within and betweensand goby populations in accordance with prey availability  相似文献
2.
微小花蝽对温室白粉虱的捕食作用   总被引:3,自引:0,他引:3  
研究微小花蝽Orius minutus(L.)对温室白粉虱Trialeurodes vaporariorum(Westwood)的捕食作用。结果表明,微小花蝽成虫对温室白粉虱各虫态的功能反应呈HollingⅡ型。微小花蝽成虫对温室白粉虱卵、1龄和2龄混合若虫及其3龄若虫的理论最大捕食量分别为123,74和52头/d。微小花蝽成虫对温室白粉虱卵的捕食效应随捕食者个体间干扰作用的增加而下降,符合Hassel-Varley方程,捕食作用率(E)随着微小花蝽数(P)增加而呈幂指数下降,模拟模型E=0.1021P-0.3189,干扰系数为0.3189。在15~40℃的温度范围内,随着温度的升高微小花蝽成虫对温室白粉虱卵的寻找效率提高,最高达1.1990,处置时间缩短,最低达到0.0035d。  相似文献
3.
Abundances and interactions among biological control insects and their effects on target invasive plants were monitored within the flower heads and roots of diffuse knapweed, Centaurea diffusa, and in spotted knapweed, Centaurea stoebe, along the Colorado Front Range. Flower weevils, (Larinus species) and root-feeders (Cyphocleonus achates and Sphenoptera jugoslavica) were released on knapweed that already supported biological control gall flies (Urophora species). At a single monitoring site, seed production by C. diffusa declined from 4400 seeds m−2 in 1997 to zero seeds m−2 on the monitoring sites in 2006, while the flowering stem density of C. diffusa declined from a peak of almost 30 stems m−2 in 2000 to zero stems m−2 in 2006. The average abundance of Urophora and Larinus in flower heads fluctuated independently during the 2001–2006 interval, while the relative abundance of C. achates and S. jugoslavica in roots exhibited a weak inverse relationship that appeared driven by climate effects. The relative abundance of insects on a population of C. stoebe was monitored for five years as Larinus species and C. achates became established on spotted knapweed that already supported Urophora species. Spotted knapweed seed production on our monitoring site declined from 4600 seeds m−2 in 2003 to zero seeds m−2 in 2006. Unlike C. diffusa, substantial numbers of rosettes of C. stoebe remained present. Larinus consumed almost all Urophora encountered in C. diffusa, and consumed about 40% of the Urophora in co-infested flower heads of C. stoebe (ca. 10–15% of the total Urophora population). No negative correlations between the relative densities of flower head and root-feeding insects were observed. The effects of these insects on target plants have produced results consistent with the ‘cumulative stress hypothesis’ for biological control of Centaurea species.  相似文献
4.
小鼩鼱(食虫目:鼩鼱科)辽宁省新纪录   总被引:2,自引:2,他引:0       下载免费PDF全文
孙悦欣 《动物学杂志》2010,45(4):171-172
在整理采自辽宁省新宾县鼩鼱属(Sorex)标本时,发现小鼩鼱(S.inutus Linnaeus,1766)为辽宁省新纪录.主要特征为上颌第二单尖齿小于第一、三单尖齿,第五单尖齿小,约为第四单尖齿的2/3高.下颌门齿向前延伸共长,其上切缘有3个深缺刻,犬齿小,是下前臼齿2/3高.  相似文献
5.
小花蝽对牛角花齿蓟马的捕食作用   总被引:2,自引:1,他引:1       下载免费PDF全文
在室内研究了小花蝽(Orius minutus)成虫对牛角花齿蓟马(Odontothrips loti)3~4龄若虫的捕食作用和种内干扰作用.结果表明,小花蝽对牛角花齿蓟马的捕食功能反应均符合HollingⅡ型方程,在玻璃试管中,捕食量(Na)符合Na=1.0113N/(1+0.04149N),在培养皿中为Na=0.6777N/(1+0.03395N),在笼罩花盆中为Na=0.6417 N/(1+0.03934 N).小花蝽的捕食作用有较强的种内干扰反应,捕食率与个体相互干扰的关系符合Hassell模型.在相同空间条件下,小花蝽的捕食量与猎物密度呈正相关,寻找效应与猎物密度呈负相关;随着空间增大,小花蝽对牛角花齿蓟马若虫的瞬间攻击率(a′)和最大捕食量(Na)均下降,处置时间(Th)则延长,但其功能反应类型不变,仍为HollingⅡ型.  相似文献
6.
Energetic constraints on mating performance in the sand goby   总被引:2,自引:0,他引:2  
Lindstrom  Kai 《Behavioral ecology》1998,9(3):297-300
I tested the effect of food addition on reproductive successin male sand gobies, Pomatoschistus minutus, by comparing food-supplementedmales with unfed, control males. The sand goby is a small marinefish with paternal egg care. The males were breeding in artificialnest sites in otherwise natural conditions in the field. I quantifiedenergy reserves by extracting nonpolar lipids. The food supplementimproved the fat reserves of the fed males as compared to unfedmales. Fed males spent more time at the nest, whereas unfedmales spent a much smaller proportion of their time at the nest.As a consequence, fed males mated sooner than unfed males andtended to get more eggs. In the unfed group, mating speed wascorrelated to body length so that bigger males mated sooner.The results suggest that the reproductive success of breedingsand goby males is constrained by the availability of energybut that this constraint is most severe for small males andless severe for bigger males. Energy availability through itseffect on condition will affect the investment in reproductiveeffort.  相似文献
7.
A PCR-based fingerprinting technique based on amplified fragment length polymorphisms (AFLP) is used to screen symbiotic fungi of the fungus-growing ant Cyphomyrmex minutus for genetic differences. AFLP fingerprints reveal several fungal ‘types’ that (a) represent distinct clones propagated vegetatively by the ant, or (b) correspond to free-living fungi that may be acquired by the ant. Fungal types identified by AFLP fingerprints correspond to vegetative-compatibility groups established previously, suggesting that vegetative compatibility can be used as a crude indicator of genetic differences between fungi of C. minutus.  相似文献
8.
9.
团扇蕨孢子发生和发育的显微观察   总被引:1,自引:0,他引:1  
利用光学显微镜对膜蕨科(Hymenophyllaceae)团扇蕨(Gonocormus minutus(Blume) Bosch)孢子的发生和发育进行了观察。研究结果表明:团扇蕨孢子为多边圆形,三裂缝不明显,外壁表面光滑,周壁薄,紧贴外壁表面,由周壁形成乳头状或颗粒状纹饰。在外壁形成后期,孢子表面和囊腔中出现大量小球;在周壁形成时期,孢子表面和周围出现较多小球体;小球和小球体参与孢子壁的形成。团扇蕨绒毡层为混合型,内层为周原质团绒毡层;外层为腺质型绒毡层。本文为膜蕨科系统演化和发育生物学研究提供依据。  相似文献
10.
Aim The Pleistocene glaciations were the most significant historical event during the evolutionary life span of most extant species. However, little is known about the consequences of these climate changes for the distribution and demography of marine animals of the north‐eastern Atlantic. The present study focuses on the phylogeographic and demographic patterns of the sand goby, Pomatoschistus minutus (Teleostei: Gobiidae), a small marine demersal fish. Location North‐eastern Atlantic, Mediterranean, Irish, North and Baltic seas. Methods Analysis was carried out by sequencing the mtDNA cytochrome b gene of sand gobies from 12 localities throughout the species’ range, and using this information in combination with published data of allozyme markers and mtDNA control region sequences. Several phylogenetic methods and a network analysis were used to explore the phylogeographic pattern. The historical demography of P. minutus was studied through a mismatch analysis and a Bayesian skyline plot. Results Reciprocal monophyly was found between a Mediterranean Sea (MS) clade and an Atlantic Ocean (AO) clade, both with a Middle Pleistocene origin. The AO Clade contains two evolutionary significant units (ESUs): the Iberian Peninsula (IB) Group and the North Atlantic (NA) Group. These two groups diverged during Middle Pleistocene glacial cycles. For the NA Group there is evidence for geographic sorting of the ancestral haplotypes with recent radiations in the Baltic Sea, Irish Sea, North Sea and Bay of Biscay. The demographic histories of the Mediterranean Clade and the two Atlantic ESUs were influenced mainly by expansions dated as occurring during the Middle Pleistocene glaciations and post‐Eem, respectively. Main conclusions The pre‐LGM (Last Glacial Maximum) subdivision signals were not erased for P. minutus during the LGM. Middle Pleistocene glaciations yielded isolated and differently evolving sets of populations. In contrast to the case for most other taxa, only the northern Atlantic group contributed to the post‐glacial recolonization. The historical demography of Mediterranean sand gobies was influenced mainly by Middle Pleistocene glaciations, in contrast to that of the Atlantic populations, which was shaped by Late Pleistocene expansions.  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