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961.
Chris S. Duvall 《Landscape Ecology》2008,23(6):699-716
Customary land-use practices create distinctive cultural landscapes, including landscapes where abandoned settlements host
vegetation that attracts wild animals. Understanding how landscape patterns relate to land-use history can help clarify the
ecological effects of particular land uses. This study examines relationships between chimpanzee habitat selection and Maninka
settlement practice, to determine how settlement history has affected chimpanzee habitat in Mali’s Bafing Biosphere Reserve,
where conservation practitioners assume that the characteristic settlement pattern reflects a process of settlement expansion
into undisturbed habitat. Three types of data are reported: (1) ethnographic interviews on settlement history and practice;
(2) systematic sampling of chimpanzee habitat use; and (3) ground-based mapping of settlement sites, surface water, and fruit-tree
patches. These data show that the Maninka have a shifting settlement system, meaning that most sites are occupied for only
relatively brief periods; and that some abandoned settlement sites host fruit-tree patches that are seasonally important chimpanzee
habitat. Two main conclusions are: (1) settlement expansion has not occurred; instead, historic settlement has created habitat
that is both attractive and available to chimpanzees. Anthropogenic habitat does not appear to be vital for chimpanzee survival,
but it spatially and temporally supplements natural habitats. (2) Conservation policies meant to reduce the presumed threat
of settlement expansion may have initiated an unintended, long-term threat of habitat loss for chimpanzees. While settlement
practices may be a component of short-term threats to chimpanzees, such as hunting, when addressing these threats conservation
practitioners should consider long-term settlement processes to avoid creating new threats. 相似文献
962.
Wind farms are positioned in open landscapes and may cause loss of wildlife habitat due to disturbance, fragmentation, and
infrastructure development. Especially flocking geese, swans, ducks and waders are regarded as vulnerable to wind farm development.
We compared past and current displacement effects of two onshore wind farms and a line of land-based turbines on spring-staging
pink-footed geese (Anser brachyrhynchus) to see if there was evidence of habituation. In one wind farm area, geese previously (1998) (Larsen and Madsen 2000) kept a distance of c. 200 m (the distance at which 50% of peak densities is reached) and they did not go between the turbines;
today (2008) they keep a distance of c. 100 m, but do still not enter the wind farm area. In another wind farm, where foraging
geese previously (2000) kept a distance of more than 100 m and did not enter the wind farm, they now (2008) forage between
the wind turbines and keep a distance of c. 40 m to turbines. In 1998, geese kept a distance of 125 m to a line of turbines,
compared to 50 m now. We conclude that geese have behaviorally adapted to changing landscapes created by wind farms. The difference
in avoidance between the sites may be due to the sizes of the turbines which in this study were small in both rotor-swept
area and in height compared to more recent “industry standard” of 2.5 and 3.0 MW turbines. The study points to the need for
longer term studies to properly assess the impact of wind farms on wildlife, including consequent increased risks from inclement
weather events of feeding, rafting, and migrating waterfowl. 相似文献
963.
Invasions resulting in the transformation of one ecosystem to another are an increasingly widespread phenomenon. While it
is clear that these conversions, particularly between grassland and shrubland systems, have severe consequences, it is often
less clear which factors are associated with these conversions. We resampled plots from the 1930s (Weislander VTMs) to test
whether two widely assumed factors, changes in fire frequency and nitrogen deposition, are associated with the conversion
of coastal sage scrublands to exotic grasslands in southern California. Over the 76-year period, coastal sage scrub cover
declined by 49%, being replaced predominantly by exotic grassland species. Grassland encroachment was positively correlated
with increased fire frequency and, in areas with low fire frequencies, air pollution (percent fossil carbon as indicated by
∂14C, likely correlated with nitrogen deposition). We conclude that increases in fire frequency and air pollution over the last
several decades in southern California may have facilitated the conversion of coastal sage shrubland to exotic grassland systems. 相似文献
964.
Seagrasses, which form critical subtidal habitats for marine organisms worldwide, are fragmented via natural processes but are increasingly being fragmented and degraded by boating, fishing, and coastal development. We constructed an individual-based model to test how habitat fragmentation and loss influenced predator–prey interactions and cohort size for a group of settling juvenile blue crabs (Callinectes sapidus Rathbun) in seagrass landscapes. Using results from field studies suggesting that strong top-down processes influence the relationship between cannibalistic blue crab populations and seagrass landscape structure, we constructed a model in which prey (juvenile blue crabs) are eaten by mesopredators (larger blue crabs) which in turn are eaten by top-level predators (e.g., large fishes). In our model, we varied the following parameters within four increasingly fragmented seagrass landscapes to test for their relative effects on cohort size: juvenile blue crab (prey) predator avoidance response, hunting ability of mesopredators and predators, the presence of a top-level predator, and prey settlement routines. Generally, prey cohort size was maximized in the presence of top-level predators and when mesopredators and predators exhibited random searching behavior vs. directed hunting. Cohort size for stationary (tethered) prey was maximized in fragmented landscapes, which corresponds to results from field experiments, whereas mobile prey able to detect and avoid predators had higher survival in continuous landscapes. Prey settlement patterns had relatively small influences on cohort size. We conclude that the effects of seagrass fragmentation and loss on organisms such as blue crabs will depend heavily on behaviors of prey and predatory organisms and how these behaviors change with landscape structure. 相似文献
965.
966.
The objective of this paper is to identify land-cover types where fire incidence is higher (preferred) or lower (avoided)
than expected from a random null model. Fire selectivity may be characterized by the number of fires expected in a given land-cover
class and by the mean surface area each fire will burn. These two components of fire pattern are usually independent of each
other. For instance, fire number is usually connected with socioeconomic causes whereas fire size is largely controlled by
fuel continuity. Therefore, on the basis of available fire history data for Sardinia (Italy) for the period 2000–2004 we analyzed
fire selectivity of given land-cover classes keeping both variables separate from each other. The results obtained from analysis
of 13,377 fires show that for most land-cover classes fire behaves selectively, with marked preference (or avoidance) in terms
of both fire number and fire size. Fire number is higher than expected by chance alone in urban and agricultural areas. In
contrast, in forests, grasslands, and shrublands, fire number is lower than expected. In grasslands and shrublands mean fire
size is significantly larger than expected from a random null model whereas in urban areas, permanent crops, and heterogeneous
agricultural areas there is significant resistance to fire spread. Finally, as concerns mean fire size, in our study area
forests and arable land burn in proportion to their availability without any significant tendency toward fire preference or
avoidance. The results obtained in this study contribute to fire risk assessment on the landscape scale, indicating that risk
of wildfire is closely related to land cover. 相似文献
967.
The urban region: natural systems in our place,our nourishment,our home range,our future 总被引:1,自引:1,他引:0
Richard T. T. Forman 《Landscape Ecology》2008,23(3):251-253
968.
A significant challenge facing forestry today is managing private forests sustainably in the face of continued ownership fragmentation
(i.e., parcelization). Cross-boundary coordination––where forest practices are coordinated across multiple properties––has
been proposed as a mechanism by which landscape-level ecological and economic benefits may be accrued in privately-owned landscapes,
but few tests of the concept exist. Using a case study approach, we quantify the extent to which ownership-centric forest
management is constrained by economies of scale and misses opportunities to achieve ecological objectives in three landscapes
in Wisconsin, USA. Methods are based on existing forest management plans and include spatial analysis of patch distributions
and shapes, simulation of forest practices, and calculation of net present value over a 20-year horizon. Our results indicate
substantial opportunity for cross-boundary coordination: between 62% and 88% of the managed properties within our study landscapes
were adjacent to other properties with forest management plans. At a patch scale, coordination can result in ecological benefits
that can be accrued into the future (e.g., maintenance of large patches and natural ecosystem boundaries). Because these landscapes
are already highly parcelized, however, coordination offers little opportunity to impact the overall landscape-scale structure.
Greater economies of scale can also be gained by coordinating forest practices, including increases in the size (16–99%) and
volume of timber sales (16–94%), and a modest economic advantage (3–6%). As first steps, investment in data infrastructure
and professional training are required to support cross-boundary multi-ownership forest management. More broadly is the need
to shift from policies and practices that are largely ownership-centric to those that include and better incorporate landscape-centric
perspectives. 相似文献
969.
Relationships of dead wood patterns with biophysical characteristics and ownership according to scale in Coastal Oregon,USA 总被引:1,自引:0,他引:1
Dead wood patterns and dynamics vary with biophysical factors, disturbance history, ownership, and management practices; the
relative importance of these factors is poorly understood, especially at landscape to regional scales. This study examined
current dead wood amounts in the Coastal Province of Oregon, USA, at multiple spatial scales. Objectives were to: (1) describe
current regional amounts of several characteristics of dead wood; (2) compare dead wood amounts across ownerships; (3) determine
the relative importance, according to spatial scale, of biophysical and ownership characteristics, to regional dead wood abundance.
Dead wood plot data were evaluated with respect to explanatory variables at four spatial scales of resolution: plots, subwatersheds,
watersheds and subbasins. The relationships of dead wood characteristics with biophysical attributes and ownership were diverse
and scale-specific. Region-wide dead wood abundance and types varied among ownerships, with public lands typically having
higher amounts of dead wood and more large dead wood than private lands. Regression analysis of total dead wood volume indicated
that ownership was important at the subbasin scale. Growing season moisture stress was important at plot, subwatershed, and
watershed scales. Topography was important at the two coarser scales. Multivariate analysis of dead wood gradients showed
that ownership was important at all scales, topography at the subbasin scale, historical vegetation at watershed and subbasin
scales, and current vegetation at plot and subwatershed scales. Management for dead wood and related biodiversity at watershed
to landscape scales should consider the distinct dynamics of snags and logs, the importance of historical effects, and the
relevance of ownership patterns. 相似文献
970.
Responses of species to landscape modifications are generally documented through their distribution at a given time along
an intensity gradient of land transformation. By focusing on patterns, we are limited to infer ecological processes occurring
within a system and its response to environmental disturbances which can further change over time. Using diachronic datasets
at the scale of France, we analyzed the spatial responses of the black-billed magpie, which has recently colonized cities,
to landscape urbanization. This study applied recently developed statistical approaches incorporating detection uncertainty
of the magpie, based on the capture-recapture statistical framework. We tested whether, and how, extinction and colonization
mechanisms influenced variations of magpie occupancy from 2001 to 2005. In addition, we assessed the importance of the recent
urbanization of the French countryside in determining population dynamics. Overall, our analysis proved that the proportion
of urban areas and recent urbanization in France led to an increase in the probability of magpie occupancy. Unexpectedly,
the species is concomitantly disappearing from the countryside, leading to a rapid change in the distribution of the species.
This study stressed the importance of incorporating detection uncertainty in inference process about spatial dynamics. Overall,
we show how useful it is to account for the dynamic evolution of the landscape in ecological studies. 相似文献