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41.
Population structure and tree recruitment dynamics in the natural treeline ecotone of high mountains are strong indicators of vegetation responses to climate. Here, we examined recruitment dynamics of Abies spectabilis across the treeline ecotone (3439–3638 m asl) of Chimang Lekh of Annapurna Conservation Area in the Trans-Himalayan zone of central Nepal. Dendrochronological techniques were used to establish stand age structure by ring counts of adults, and by terminal bud scar count for seedlings and saplings. The results showed abundant seedling recruitment, higher regenerative inertia and colonization with a consistent range shift of the A. spectabilis treeline. The upward expansion of this sub-alpine treeline was found to be driven by a strong dependence of seedling recruitment and radial growth on snowmelt and precipitation as temperatures rise. The radial growth of A. spectabilis at the alpine timberline ecotone (ATE) and closed timberline forest (CTF) showed sensitivity to spring season (March–May) climate. Tree ring indices of CTF showed a strong positive correlation with spring and annual precipitation, and a significant negative correlation with spring and annual temperature, however, moisture sensitivity was less strong at ATE than CTF. 相似文献
42.
An appraisal of methods used in coral recruitment studies 总被引:3,自引:0,他引:3
C. N. Mundy 《Coral reefs (Online)》2000,19(2):124-131
A new method for attaching individual artificial settlement plates directly to the reef surface using small stainless steel
base plates is described. Recruitment of corals to settlement plates attached to the reef substratum and to steel mesh racks
is compared. The effects of differences in depth, settlement plate angle, and local topography on recruitment of corals were
also investigated. No significant difference in mean recruit density was found between settlement plates deployed using the
two attachment methods. Small differences in depth and plate angle among replicate plates explained less than 6% of the variability
in coral recruitment on replicate settlement plates. The direct-attachment method is less obtrusive, more cost and time efficient,
and settlement plates can be deployed at precise locations. Additionally, because settlement plates are deployed individually
rather than grouped on racks or frames, the direct-attachment method avoids complications associated with assumptions of independence
implicit in most statistical procedures.
Accepted: 24 November 1999 相似文献
43.
We investigated demographic responses of the common brushtail possum Trichosurus vulpecula, a medium-sized arboreal marsupial, after a prescribed fuel reduction burn on Magnetic Island, tropical north Queensland,
Australia. Possums were live-trapped every month for 14 months before the fire and 11 months after the fire in both the burnt
and unburnt areas; measurements of individuals were taken each month and demographic parameters were modelled using capture–mark–recapture
data. Significant differences between the burnt and unburnt sites were found following the fire; recruitment was lower in
the unburnt area, where population size also declined. In the burnt area, population size and recruitment displayed a tendency
to increase after the fire, while capture probability declined, suggesting that an influx of new individuals, attracted to
re-sprouting vegetation, had resulted in trap saturation. There was no detectable effect of the fire on survival, and no fire-induced
mortalities were observed. We conclude that a low-intensity, prescribed, fuel-reduction burn had no obvious negative consequences
for this possum population. 相似文献
44.
Abstract. In this study we used species inventory data collected in 1970 and 1993 from 132 plots in a 14.5ha deciduous forest to examine local extinction and colonization processes among 45 field layer species. Local colonization rate was positively related to both seed size and seed dispersal features. Local extinction rate was negatively related to seed size. Growth form (clonal vs. non-clonal) and presence of a seed bank were not found to be associated with local dynamics. Despite an overall constancy in species composition during this period, plants exhibited a considerable mobility among the 132 plots. This pattern conformed to a suggested ‘carousel model’ of species mobility in grasslands. A tentative suggestion is that this mobility acts on a comparatively broader spatio-temporal scale in deciduous forests as compared with grasslands. Additional data are presented indicating that species abundance (frequency) among field layer plants in deciduous forest communities is consistent among forest fragments, and when comparing local and regional scales. The main conclusion is that life history features of the seed dispersal/recruitment phase, particularly seed size, are causally associated with abundance patterns at least at a local scale, but possibly also on a broader regional scale. 相似文献
45.
Nuthatches (Sitta europaea: Aves) in forest fragments: demography of a patchy population 总被引:1,自引:0,他引:1
Erik Matthysen 《Oecologia》1999,119(4):501-509
Breeding density, local survival and summer recruitment of nuthatches were evaluated in a population scattered over many
small (1–30 ha) forest fragments, and compared with study plots inside larger forests. Since most young birds settle outside
the fragment in which they were born this population corresponds to the “patchy population” concept implying that patterns
in abundance may be better explained by processes at the population level than by metapopulation processes. Mean breeding
density was c. 50% lower in fragments and decreased with regional isolation (distance from larger forests) but not with local isolation
(distance to nearby fragments). Local survival of adults and established (i.e. territorial) 1st-year birds was not related
to forest size or isolation. However, fewer young birds settled in summer in the fragments compared with a large forest. This
difference probably reflects high mortality during the sensitive dispersal phase. Moreover, the observed number of recruits
and their estimated survival was insufficient to maintain the breeding population, suggesting significant net immigration
from larger forests. This “rescue effect” explains why densities are affected by regional, but not local isolation.
Received: 14 December 1998 / Accepted: 1 March 1999 相似文献
46.
Abstract. Size-structure dynamics and co-existence of the conifers Abies sachalinensis and Picea glehnii in subalpine forests in Japan, in relation to the understorey dwarf bamboo Sasa, were examined using a simulation model. This model explicitly incorporated recruitment rate, size growth rate and mortality. Recruitment and growth rates were assumed to be suppressed by the cumulative basal area of taller trees and the density of Sasa. As for the one-sided crowding effect, two types of model were examined. The total basal area of the two species suppresses the growth and recruitment rates in an additive model, while the basal area of each species has a separate effect included in a specific model. Two types of recruitment process were examined, i.e. open and closed systems; recruitment rates of open and closed systems are independent of, and proportional to, the basal area of the same species within the plot, respectively. Parameters were estimated from data of plot censuses for four years. The parameters of the specific model showed that recruitment and size growth rates were more suppressed by the same species than the other species. Recruitment of A. sachalinensis was more sensitive to suppression by Sasa compared with P. glehnii. The stationary size structure of the two species, generated from both the models with the open system, fitted well to the observed size structures across various Sasa densities. A. sachalinensis and P. glehnii dominated at lower and higher densities of Sasa, respectively. However, the closed-system simulation showed that the stable co-existence of the two species with a good fit to the observed size structure occurred only in the specific model. These results suggest that within-species interference, which is more severe than between-species interference, is important for the co-existence of the two species and that the relative dominance of the two species readily explained the differential responses to Sasa abundance. 相似文献
47.
Midori Iida Shun Watanabe Akira Shinoda Katsumi Tsukamoto 《Environmental Biology of Fishes》2008,83(3):331-341
Ecological aspects of recruitment in the amphidromous goby, Sicyopterus japonicus, were studied from larval collections made with a set net in the estuary of the Ota River, Wakayama, Japan. The abundance
patterns of the 12,766 larvae collected from 18 April to 26 August 2006 showed several peaks during the recruitment season.
Their body sizes at recruitment ranged from 23.5 to 30.0 mm standard length (mean ± SD, 26.3 ± 1.1 mm), 0.11 to 0.49 g body
weight (0.22 ± 0.05 g), and 8 to 20 condition factor (11 ± 2). The standard length of the goby larvae tended to decrease with
the season, while their body weight slightly increased and resulted in an increase in condition factor. The recruitment of
larvae occurred mainly during the daytime. Otolith growth increment analysis of 30 larvae collected by a square lift net on
30 April 2005 revealed that the oceanic larval duration after downstream migration ranged from 173 to 253 days (208 ± 22)
after hatching. A limited time of recruitment in early summer and a considerably long duration of oceanic life (about a half
year) appeared to be unique characteristics of this Sicyopterus species that lives in a temperate region in comparison to other tropical species of the genus Sicyopterus that all have year-round recruitment. 相似文献
48.
Group members present physical and physiological differences according to their age, sex or social status, which could generate
motivation differences among individuals during travel. In spite of these divergences of interest among individuals, the group
succeeds more often than not in making a collective decision about departure time and which direction to take. To reach a
consensus decision, animals should exchange information relating to characteristics of group movement through different communication
channels. The main purpose of this study is to understand the function of behaviour patterns displayed during movements of
white-faced capuchins (Cebus capucinus). We designed experiments in which we provoked collective movements involving a binary choice. During experiments, a video
camera recorded the behaviour of each capuchin, which enabled us to determine which individuals displayed a behavioural pattern
during travel and how this behaviour influenced the other group members. We found that looking backwards seemed to permit
the recruitment of group mates during collective movement. This behaviour also seemed to allow the quantification of the number
of followers, since the emitter modified its locomotion speed according to this number. In this preliminary study, we showed
that visual behaviour was used to recruit and monitor group mates during collective movements and provided information on
mechanisms involved in maintaining cohesion and coordination among group members during travel. 相似文献
49.
Thinking and managing outside the box: coalescing connectivity networks to build region-wide resilience in coral reef ecosystems 总被引:4,自引:4,他引:0
R. S. Steneck C. B. Paris S. N. Arnold M. C. Ablan-Lagman A. C. Alcala M. J. Butler L. J. McCook G. R. Russ P. F. Sale 《Coral reefs (Online)》2009,28(2):367-378
As the science of connectivity evolves, so too must the management of coral reefs. It is now clear that the spatial scale
of disturbances to coral reef ecosystems is larger and the scale of larval connectivity is smaller than previously thought.
This poses a challenge to the current focus of coral reef management, which often centers on the establishment of no-take
reserves (NTRs) that in practice are often too small, scattered, or have low stakeholder compliance. Fished species are generally
larger and more abundant in protected reserves, where their reproductive potential is often greater, yet documented demographic
benefits of these reproductive gains outside reserves are modest at best. Small reproductive populations and limited dispersal
of larvae play a role, as does the diminished receptivity to settling larvae of degraded habitats that can limit recruitment
by more than 50%. For “demographic connectivity” to contribute to the resilience of coral reefs, it must function beyond the
box of no-take reserves. Specifically, it must improve nursery habitats on or near reefs and enhance the reproductive output
of ecologically important species throughout coral reef ecosystems. Special protection of ecologically important species (e.g.,
some herbivores in the Caribbean) and size-regulated fisheries that capitalize on the benefits of NTRs and maintain critical
ecological functions are examples of measures that coalesce marine reserve effects and improve the resilience of coral reef
ecosystems. Important too is the necessity of local involvement in the management process so that social costs and benefits
are properly assessed, compliance increased and success stories accrued. 相似文献
50.
Lizardfish (family Synodontidae) are little studied despite their potentially important predatory role in epibenthic coral
reef communities. The present study documented the temporal and spatial larval supply patterns of five Caribbean lizardfish
species together with environmental variables (solar radiation, rainfall, water temperature, onshore-offshore winds, alongshore
winds and wind-induced turbulence) to examine: (1) whether species within the same family respond differently to their developmental
environment and (2) if larval supply in year-round warm waters is influenced by climatic changes. To address these questions,
late-stage larvae of Synodus foetens, Synodus intermedius, Synodus poeyi, Saurida suspicio and Saurida brasiliensis were collected in replicate light traps in three different reef habitats (back-reef, lagoon and exposed) in the San Blas
Archipelago, Panama, over 18 consecutive lunar months. Although replenishment of lizardfish occurred year-round, the temporal
and spatial supply patterns were species-specific: S. foetens, S. intermedius and S. poeyi were most abundant during the dry season while S. suspicio and S. brasiliensis were most prevalent during the wet season. When seasons were analysed separately, water temperature explained 39 and 26%
of the variance in light trap catches of S. foetens and S. intermedius, respectively, in the dry season while wind-induced turbulence accounted for 25% of the variability in S. suspicio and S. brasiliensis catches during the wet season. These findings stress the importance of analysing larval supply in conjunction with environmental
data at a high taxonomic resolution to better understand the mechanisms that drive replenishment in reef systems at low latitudes. 相似文献