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131.
132.
Effects of artificial ultraviolet-B radiation on growth and fatty acid composition of duckweed (Lemna minor) 总被引:1,自引:0,他引:1
D. L. W. YOUNG M. D. WIEGAND N. L. LOADMAN S. A. COLLINS A. J. BALLEVONA J. D. HUEBNER 《Freshwater Biology》2006,51(11):2029-2040
1. Duckweed (Lemna minor), collected either in summer or early fall was exposed under laboratory conditions to control (photosynthetically active and UV‐A radiation) or experimental (control plus UV‐B radiation) conditions. 2. Growth and survival were determined by counting the number of green, and brown/white fronds following 1–5 or 11 days of irradiation. Growth of duckweed was impaired by exposure to UV‐B radiation in the fall experiment but not in the summer. 3. Fatty acid compositions were analysed following 5 or 11 days of irradiation and a recovery period of 0, 5, 29 or 40 h. Concentrations of the major fatty acids, palmitic, linoleic (LA) and α‐linolenic (ALA) acids were similar in the summer and fall duckweed collections, but the summer samples had higher concentrations of the desaturation products of LA and ALA. 4. UV‐B exposure had small, but significant, and contrasting effects on duckweed fatty acid concentrations. In the summer experiment, duckweed exposed to UV‐B had slightly lower concentrations of major fatty acids than control duckweed, while the reverse was true in the fall experiments. 5. These minor effects of UV‐B on concentrations of LA and ALA would be unlikely to have a major impact on the supply of these essential fatty acids from duckweed to freshwater food webs. 相似文献
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ABSTRACT Accurately estimating large mammal populations is a difficult challenge because species of interest often occupy vast areas and exhibit low and heterogeneous visibility. Population estimation techniques using aerial surveys and statistical design and analysis methods provide a means for meeting this challenge, yet they have only rarely been validated because wild populations of known size suitable for field tests are rare. Our study presents field validations of a photographic aerial mark-recapture technique that takes advantage of the recognizable natural markings on free-roaming feral horses (Equus caballus) to accurately identify individual animals and groups of animals sighted on multiple occasions. The 3 small populations of feral horses (<400 animals each) in the western United States used in the study were all closely monitored on a weekly basis by local researchers, thus providing test populations of known size. We were able to accurately estimate these population sizes with aerial surveys, despite rugged terrain and dense vegetation that created substantial heterogeneity of sighting probability among horse groups. Our best estimates at the 3 sites were within −6.7%, 2.6%, and −8.6% of known truth (-4.2% mean error, 6.0% mean absolute error). In contrast, we found undercount bias as large as 32% before any statistical corrections. The necessary corrections varied both temporally and spatially, in response to previous sighting history (behavioral response), and by the number of horses in a group. Despite modeling some of the differences in horse-group visibility with sighting covariates, we found substantial residual unmodeled heterogeneity that contributed to underestimation of the true population by as much as 22.7% when we used models that did not fully account for these unmeasured sources. We also found that the cost of the accurate and validated methods presented here is comparable to that of raw count (so called, census) methods commonly employed across feral horse ranges in 10 western states. We believe this technique can assist managers in accurately estimating many feral horse populations and could be applied to other species with sufficiently diverse and distinguishable visible markings. 相似文献
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RANDY W. DEYOUNG ANGELINE ZAMORANO BRIAN T. MESENBRINK TYLER A. CAMPBELL BRUCE R. LELAND GUY M. MOORE RODNEY L. HONEYCUTT J. JEFFREY ROOT 《The Journal of wildlife management》2009,73(8):1292-1299
ABSTRACT In west-central Texas, USA, abatement efforts for the gray fox (Urocyon cinereoargenteus) rabies epizootic illustrate the difficulties inherent in large-scale management of wildlife disease. The rabies epizootic has been managed through a cooperative oral rabies vaccination program (ORV) since 1996. Millions of edible baits containing a rabies vaccine have been distributed annually in a 16-km to 24-km zone around the perimeter of the epizootic, which encompasses a geographic area >4 × 105 km2. The ORV program successfully halted expansion of the epizootic into metropolitan areas but has not achieved the ultimate goal of eradication. Rabies activity in gray fox continues to occur periodically outside the ORV zone, preventing ORV zone contraction and dissipation of the epizootic. We employed a landscape-genetic approach to assess gray fox population structure and dispersal in the affected area, with the aim of assisting rabies management efforts. No unique genetic clusters or population boundaries were detected. Instead, foxes were weakly structured over the entire region in an isolation by distance pattern. Local subpopulations appeared to be genetically non-independent over distances >30 km, implying that long-distance movements or dispersal may have been common in the region. We concluded that gray foxes in west-central Texas have a high potential for long-distance rabies virus trafficking. Thus, a 16-km to 24-km ORV zone may be too narrow to contain the fox rabies epizootic. Continued expansion of the ORV zone, although costly, may be critical to the long-term goal of eliminating the Texas fox rabies virus variant from the United States. 相似文献
137.
BRUCE A. BYERS 《Biological journal of the Linnean Society. Linnean Society of London》1990,40(1):3-10
Littorina saxatilis Olivi (1792), the rough winkle, is highly polymorphic in shell colour. Shell colour frequencies were studied at six locations in south-western Wales, U.K., each at a geological contact between red sandstone and grey limestone or volcanic rock. At each site shell colour frequencies were determined in samples from the contact zone and on red or grey rock on either side. Highly significant associations were found between shell colour frequencies and substrate colour. Grey shells were always more common on grey rock than on red rock, and brown shells were usually more common on red than on grey rock, suggesting selection for cryptic colouration. Shell colour frequency differences were also found between replicate samples taken only 5 m apart from the same kind of rock, and between samples from the same kind of rock at the six study sites. These latter differences suggest that selection for camouflage is not the only factor involved in maintaining shell colour polymorphism in this species. 相似文献
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RICHARD J. GORNALL BRUCE A. BOHM 《Botanical journal of the Linnean Society. Linnean Society of London》1985,90(1):1-71
An evaluation of the limits and infra-generic taxonomy of the genus Boykinia and its allies is presented. In the past, Boykinia has been split into the following segregate genera: Boykinia and Telesonix (from North America) and Neoboykinia and Peltoboykinia (from Japan). The situation is complicated by other closely related genera, the limits of which also need clarification. Narrowly defined, they comprise Suksdorfia, Hemieva, Bolandra, Sullivantia and Jepsonia (all from North America) and Hieronymusia (from South America). This monograph draws on a variety of sources for information, including a morphological comparison of all taxa, using a wide range of both living and herbarium material, and observations on leaf anatomy, trichomes, pollen grains and seeds; reference is also made to our previously published work on flavonoids, chromosome numbers and breeding relationships. General ecological observations were made during field work in western North America. The results of these investigations confirm that the genera form a closely related group. Much of the evidence combines to suggest the following conclusions. Boykinia includes nine species in three sections: section Boykinia (B. aconitifolia , B. intermedia , B. lycoctonifolia , B. major , B. occidentalis and B. rotundifolia) , section Renifolium (B. ruhardsonii) and section Telesonix (B. jamesii and B. heucheriformis). Peltoboykinia (P. tellimoides and P. watanabei ) is recognized as a distinct genus allied to both Saxifraga and Boykinia. Suksdorfia , expanded to include Hemieva and Hieronymusia , has three species: S. violacea, S. alchemilloides and S. ranunculifolia. Bolandra is very closely related to Suksdorfia but is retained as a separate genus containing two species, B. californica and B, oregana. Sullivantia and Jepsonia are accepted as genera related to, but distinct from, Boykinia. 相似文献
139.
We describe a mechanistic individual-based model of how globalmacroclimatic constraints affect the energy budgets of ectothermicanimals. The model uses macroclimatic and biophysical charactersof the habitat and organism and tenets of heat transfer theoryto calculate hourly temperature availabilities over a year.Data on the temperature dependence of activity rate, metabolism,food consumption and food processing capacity are used to estimatethe net rate of resource assimilation which is then integratedover time. We detail and explore the significance of assumptionsused in these calculations. We present a new test of this model in which we show that thepredicted energy budget sizes for 11 populations of the lizardSceloporus undulalus are in close agreement with observed resultsfrom previous field studies. This demonstrates that model testsare feasible and the results are reasonable. Further, sincethe model represents an upper bound to the size of the energybudget, observed residual deviations form explicit predictionsabout the effects of environmental constraints on the bioenergeticsof the study lizards within each site that may be tested byfuture field and laboratory studies. Three major new improvements to our modeling are discussed.We present a means to estimate microclimate thermal heterogeneitymore realistically and include its effects on field rates ofindividual activity and food consumption. Second, we describean improved model of digestive function involving batch processingof consumed food. Third, we show how optimality methods (specificallythe methods of stochastic dynamic programming) may be includedto model the fitness consequences of energy allocation decisionssubject to food consumption and processing constraints whichare predicted from the microclimate and physiological modeling Individual-based models that incorporate macroclimatic constraintson individual resource acquisition, assimilation and allocationcan provide insights into theoretical investigations about theevolution of life histories in variable environments as wellas provide explicit predictions about individual, populationand community level responses to global climate change. 相似文献
140.