全文获取类型
收费全文 | 152篇 |
免费 | 4篇 |
国内免费 | 30篇 |
专业分类
186篇 |
出版年
2020年 | 5篇 |
2018年 | 3篇 |
2017年 | 10篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 5篇 |
2009年 | 9篇 |
2008年 | 18篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 5篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1978年 | 6篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 2篇 |
排序方式: 共有186条查询结果,搜索用时 15 毫秒
81.
Teiji Sota 《Population Ecology》1985,27(1):171-184
- Effects of the amount of food consumed on reproduction of the carabid beetle, Carabus yaconinus B., were studied in the laboratory by rearing beetles at different food levels, and the feeding and oviposition rates in the field were estimated on the basis of the relationships between the amount of food consumed, body weight and egg production obtained in the experiment.
- The maximum amount of food consumed was 150 mg of minced beef per day. The number of eggs laid per day and the mean body weight increased with an increase in the amount of food consumed. High mortality occurred only when the beetles consumed less than 25 mg of minced beef per day.
- The ratio of current body weight to the minimum one just before death by starvation, W/Wmin, was used for the estimation of the rates of food consumption and egg production. The relationships between mean W/Wmin ratio, the amount of food consumed and the number of eggs laid per day were clarified.
- The relationships between ovary states (ovary weight and the number of mature eggs in the ovary) and W/Wmin ratio were examined for the females caught in the field. Females with higher values of W/Wmin ratio had more mature eggs.
- The amount of food consumed by females in the field during the reproductive period was estimated to be 50–70% of the maximum value attained in the experiment and the estimated rate of oviposition was 45–59% of the maximum rate attained in the experiment.
82.
Community dynamics in local habitats are affected by landscape characteristics such as the area and connectivity of surrounding
habitats at a functional spatial scale where the community responds to landscape structure. However, the functional spatial
scale at which community composition is affected by landscape structure has never been explored. We assessed the functional
spatial scales of composition change in birds and in three types of arthropod communities (canopy, forest-floor and flying
ones) with regard to landscape heterogeneity resulting from a large typhoon in a temperate forest of Japan. We examined the
effects of tree-fall disturbance on the communities at various spatial scales, with special attention to compositional evenness.
The spatial scale of the best-fitting model, which was selected from models fitted to the disturbance area at stepwise spatial
scales, was interpreted as the community-specific functional spatial scale. The composition of all communities studied was
all significantly dependent on gap area. The functional spatial scale was highest in birds (370 m in radius), intermediate
in flying arthropods (90 m) and lowest in canopy and forest-floor arthropods (10 m). This result may reflect typical dispersal
ability and the spatial range of resource use in the community. Compositional changes in each community were consistent with
theory regarding traits and responses of component taxa, although the enhancement of evenness was observed only in the arthropod
communities. These results imply that management and reserve selection based on functional spatial scales can be effective
in the conservation of biodiversity and ecosystem services at the community level. 相似文献
83.
Luke A. Parry David A. Legg Mark D. Sutton 《Lethaia: An International Journal of Palaeontology and Stratigraphy》2017,50(2):222-226
A megacheiran arthropod, Enalikter aphson, was recently described by Siveter et al. (2014) from the mid‐Silurian (late Wenlock) of Herefordshire. Previously, megacheirans had only been recognized from the Cambrian. Struck et al. (2015) considered the body plan of Enalikter to be incompatible with this affinity, arguing that many of the arthropod features were either not present or misinterpreted. Instead, they compared Enalikter to polychaete annelids, identifying characters from numerous polychaete lineages which they considered to be present in Enalikter. A reply to this critique by Siveter et al. (2015) reaffirmed arthropod affinities for Enalikter by presenting additional evidence for key arthropod features, such as arthropodized appendages. Here, we augment Siveter et al. by critically addressing the putative annelid characters of Enalikter presented by Struck et al. and additionally explore the morphological and phylogenetic implications of their hypothesis. We conclude that similarities between Enalikter and polychaetes are superficial and that character combinations proposed by Struck et al. are not present in any annelid, living or extinct. This taxon highlights the importance of using a phylogenetic framework for interpreting fossils that present unusual morphologies, such that proposed shared characters are hypotheses of homology rather than merely phenotypic similarities. Crucially, we argue that autapomorphic characters of subgroups of large taxa (like families or classes within phyla) should not be used to diagnose problematic fossils. 相似文献
84.
描述3块新的标本,分别是节肢动物Pisinnocaris sp.,Tanglangia longicaudata Luo et Hu,1999和Pygmaclypeatus daziensis Zhang,Han et Shu,2000。新的标本进一步增进我们对其形态结构特征的了解。通过与相关属种的比较,简要讨论其系统位置问题。 相似文献
85.
86.
How fast do marine invertebrates burrow? 总被引:2,自引:1,他引:1
Murray K. Gingras S. George Pemberton Shahin Dashtgard Lynn Dafoe 《Palaeogeography, Palaeoclimatology, Palaeoecology》2008,270(3-4):280
The burrowing of bivalves, arthropods, and echinoderms collected from tidal flats and shallow subtidal sediments of the Ogeechee estuary, Georgia, U.S.A was analyzed using time-elapse, X-ray analysis of thin-walled aquaria. The rate of sediment intrusion was determined for each animal. Burrowing rates ranged between 0.01 and 0.15 cm3/h for suspension-feeding animals. Deposit-feeding animals moved between 1 and 10 cm3 of sand per hour, approximately 10 to 100 times more sediment than the suspension feeders moved over similar times.Neoichnological experiments show that ten filter-feeding individuals could take as long as 115 yr to churn a 1 m2 plot of sediment, by indexing the measured burrowing rates to realistic animal population densities. Ten such mobile deposit feeders as irregular echinoderms could bioturbate the same sediment in just 42 days. Under the maximum population densities modeled, the animals could bioturbate the sediment plot in 61 min. Given the reported results, qualitative interpretation of the rock record is possible: highly burrowed examples of the Skolithos Ichnofacies reflect high population densities and at least seasonal time spans. Highly burrowed examples of the Cruziana Ichnofacies may represent moderate population densities and short time spans. 相似文献
87.
Yves Hingrat Frédéric Ysnel Michel Saint Jalme Joseph Le Cuziat Pierre-Marie Béranger Frédéric Lacroix 《Biodiversity and Conservation》2007,16(3):597-620
In Morocco we tested the consistency between an a priori habitat classification based on topography, hydrology, vegetation structure and composition, and an a posteriori classification based on arthropod assemblages, in a plain supporting wild endangered Houbara Bustards. According to vegetation
structure, we defined seven a priori habitats that differed significantly in perennial cover and height. A multivariate multiple regression analysis showed a
significant relationship between arthropod assemblages and vegetation structure. Canonical Analyses of Principal Coordinates,
conducted simultaneously on direct searches of arthropods and trapping data, showed significant differences between assemblages
in both cases, and produced two similar constrained ordinations of six a posteriori habitats: esparto grass (Stipa tenacissima), temporarily flooded areas, fields, “reg” with short perennials, “reg” with tall perennials and wadis. The two sampling
methods reflected a dominance of ants and beetles. Arthropod biomasses increased significantly in spring and then decreased
significantly in summer for beetles, and in autumn for ants. No strong differences appeared between habitats within seasons,
especially in spring, indicating a uniform distribution of food resources during the Houbara breeding season. The “reg” with
short perennials had the highest ant biomass in summer. This “reg” and fields also supported the highest arthropod biomass
in autumn. Variation in arthropod biomass was a pertinent factor that should be integrated into Houbara habitat selection
studies. The definition of habitat availability based on easily identifiable landscape units, combined with empirical tests
on arthropod communities provided an accurate classification for habitat selection studies and conservation planning. 相似文献
88.
管理水平对葡萄园节肢动物群落特征参数及目标害虫、天敌种群数量的影响 总被引:4,自引:2,他引:4
对管理精细和管理粗放的两种葡萄园进行全株调查和地面扫网调查,分析其节肢动物群落结构特征参数差异及目标害虫葡萄跳叶甲和两种天敌草间小黑蛛、肖蛸蛛种群数量的差异.结果表明,两种葡萄园节肢动物群落之间在个体数量、优势集中性指数、均匀度指数和多样性指数上差异不显著;物种数和丰富度指数差异显著(P<0.05);葡萄树上节肢动物物种数差异不显著,地面植被上物种数差异显著(P<0.05);两种葡萄园之间树上和地面节肢动物个体数量、目标害虫葡萄跳叶甲种群数量、主要天敌草间小黑蛛和肖蛸蛛种群数量差异均不显著. 相似文献
89.
The nature and origin of the arthropod labrum is a matter much under dispute. We show here that in Tribolium castaneum (Herbst, 1797) the labrum develops from two individual primordia, termed labral buds. Expression of the genes decapentaplegic (dpp) and wingless (wg) in these buds is identical to the buds of the metameric appendages (e.g. thoracic legs), except that the patterns are reversed. We propose that this reversal is the result of the rotation of the labral buds through an angle of approximately 180°. We also for the first time study dpp and wg expression in the fully developed labrum of older embryonic stages. Here, gene expression patterns show that the labrum proper is formed by fusion of the labral buds along their dorsal sides, while their ventral sides are facing outward forming the lateral sides of the fused labrum. Furthermore, we show that there are very similar patterns in another arthropod species, the spider Cupiennius salei (Keyserling, 1877), although in this species the labrum develops as a single structure and not from two separate primordia. However, in C. salei the expression of engrailed is also reversed in addition to the reversal of dpp and wg expression: engrailed is expressed in the anterior half of the labrum, and not in the posterior half like in the remaining appendages. Our results suggest that the arthropod labrum is derived evolutionarily from paired limb-bud-like primordia by rotation and fusion, and that this process is recapitulated ontogenetically to a different extent in different arthropod species. 相似文献
90.
桃园节肢动物群落的多样性、均匀度和相对稳定性季节动态 总被引:10,自引:0,他引:10
对桃园节肢动物群落进行了系统调查,并对数据进行了数学分析.结果表明,群落与植食动物亚群落的多样性指数相关系数为0.9480,两者极显著相关;群落与捕食动物亚群落的多样性指数相关系数为0.7855,两者极显著相关;两个亚群落的多样性均与群落多样性有关,两个亚群落多样性指数间相关系数为0.6741,两者显著相关;群落多样性指数与群落均匀度指数问相关系数为0.7870,两者极显著相关;群落多样性指数与两个亚群落均匀度指数之间均不相关.群落多样性指数(H’),与捕食性动物个体数(Sd)和植食性动物个体数(Sz)之比值(Sd/Sz)相关系数为0.8112,两者极显著相关;与群落物种数(Sz)和个体数(Si)之比值(Sz/Si)相关系数为0.9188,两者极显著相关;与捕食动物类群(科)数(Spl)和植食动物类群(科)数(Szl)之比值(Spl/Szl)不相关。 相似文献