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Landscape Ecology - Pollinator declines and functional homogenization of farmland insect communities have been reported. Mass-flowering crops (MFC) can support pollinators by providing floral... 相似文献
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In the marine environment, pelagic dispersal is important for determining the distribution and abundance of populations, as well as providing connections among populations. Estimates of larval dispersal from spawning grounds are important to determining temporal and spatial patterns in recruitment that may have significant influences on the dynamics of the population. We present a case study of the dispersal of Centropristis striata (black sea bass) larvae on the southeast U.S. continental shelf. We use a coupled larval behavior – 3D circulation model to compare the effects of the timing and location of spawning against that of larval vertical migration on larval dispersal. Using the results of field data on larval vertical distributions, we compare the dispersal of virtual 'larvae' which have ontogenetic changes in vertical behavior with that of particles fixed near the surface and near the bottom. Larvae were released at potential spawning sites four times throughout the spawning season (February through May) for 3 yr (2002–04) and tracked for the assumed larval duration (from 27 to 37 days including the egg stage). Results indicate that adult behavior, in the form of spawning time and location, may be more important than larval vertical behavior in determining larval dispersal on the inner- and mid- continental shelves of this region. 相似文献
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The leaf area index (LAI) of boreal forest can be estimated using reflected radiation recorded by satellite sensors. Measurements of visible and near infrared radiation are commonly used in the normalized difference vegetation index (NDVI) to estimate LAI. However, research, mainly in tropical forest, has demonstrated that LAI is related more closely to radiation of middle infrared wavelengths than of visible wavelengths. This paper derives a vegetation index, VI3, based on radiation from vegetation recorded at near and middle infrared wavelengths. For a boreal forest canopy, the relationship between VI3 and LAI was observed to be much stronger than that between NDVI and LAI. In addition, the LAI estimated using VI3 accounted for about 76% of the variation in field estimates of LAI, compared with about 46% when using the NDVI. We conclude that information provided by middle infrared radiation should be considered when estimating the leaf area index of boreal forest. 相似文献
4.
Influences of mean advection and simple behavior on the distribution of cod and haddock early life stages on Georges Bank 总被引:2,自引:0,他引:2
FRANCISCO E. WERNER FRED H. PAGE DANIEL R. LYNCH JOHN W. LODER R. GREGORY LOUGH R. IAN PERRY DAVID A. GREENBERG MICHAEL M. SINCLAIR 《Fisheries Oceanography》1993,2(2):43-64
Results of a modeling study designed to explore the influences of physical advection and certain biological mechanisms on the distribution of cod (Gadus morhua) and haddock (Melarwgrammus aeglefinus) early life stages on Georges Bank are described. Using a late-winter/early-spring 3-D circulation field driven by the M2 tidal current, mean wind stress and Scotian Shelf inflow, we examine the distribution of cod and haddock larvae spawned on the Northeast Peak of the Bank. The sensitivity to a March-April baroclinic field is also explored. Results indicate that larvae remaining in the surface Ekman layer are generally advected off-bank. However, downwelling associated with Ekman layer convergence near the shelf break provides a mechanism for larvae to exit from the off-bank surface drift. Larvae below the surface layer are transported south-westward along the southern flank of Georges Bank and are retained on the Bank if their position immediately upstream of the Great South Channel is shoalward of (roughly) the 70 m isobath. Within the Great South Channel region and between the 50 and 70 m isobaths, retention can depend on the phase of the tide. Spawning shoalward of the 50 m isobath on the Northeast Peak greatly increases the chances of retention. These results apply to passive larvae and to those with specified vertical distributions and migration based on observations. Directional on-bank swimming at rates of 0.5 to 1 body length per second would substantially enhance shoalward displacement, resulting in larval distributions during the first 2 months that are consistent with field observations. 相似文献
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Houston DM Moore AE Favrin MG Hoff B 《The Canadian veterinary journal. La revue veterinaire canadienne》2004,45(3):225-230
The purpose of this study was to report on the age, sex, breed, and mineral composition of 16 647 canine bladder uroliths submitted to the Canadian Veterinary Urolith Centre between February 1998 and April 2003. Each urolith submission was accompanied by a questionnaire. Of the submissions, approximately 43.8% were struvite and 41.5% oxalate. Struvite uroliths were most common in female dogs. Mixed breed dogs predominated, followed by the shih tzu, bichon frise, miniature schnauzer, Lhasa apso, and Yorkshire terrier. Oxalate uroliths were most common in males and in the miniature schnauzer, bichon frise, Lhasa apso, shih tzu, and Yorkshire terrier. Urate uroliths were most common in male Dalmations. Other urolith types, including cystine, xanthine, silica, and calcium phosphate, were less commonly reported. A review of risk factors for the various uroliths is presented, along with some recommendations for treatment and prevention. 相似文献
7.
Houston DM Rinkardt NE Hilton J 《Veterinary therapeutics : research in applied veterinary medicine》2004,5(3):187-201
Clinical signs of struvite urolithiasis resolved in an average of 19 days in cats fed either a canned or dry urine-acidifying, magnesium-restricted diet, and stones completely dissolved in 31 of 39 cats in an average of 30 days. Stones were surgically removed from five cats, and analysis revealed that these stones were not composed of struvite. The results of this study strongly suggest that the diet will dissolve naturally occurring feline struvite bladder uroliths. 相似文献
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Context
Recent research suggests that novel geodiversity data on landforms, hydrology and surface materials can improve biodiversity models at the landscape scale by quantifying abiotic variability more effectively than commonly used measures of spatial heterogeneity. However, few studies consider whether these variables can account for, and improve our understanding of, species’ distributions.Objectives
Assess the role of geodiversity components as macro-scale controls of plant species’ distributions in a montane landscape.Methods
We used an innovative approach to quantifying a landscape, creating an ecologically meaningful geodiversity dataset that accounted for hydrology, morphometry (landforms derived from geomorphometric techniques), and soil parent material (data from expert sources). We compared models with geodiversity to those just using topographic metrics (e.g. slope and elevation) and climate data. Species distribution models (SDMs) were produced for ‘rare’ (N?=?76) and ‘common’ (N?=?505) plant species at 1 km2 resolution for the Cairngorms National Park, Scotland.Results
The addition of automatically produced landform geodiversity data and hydrological features to a basic SDM (climate, elevation, and slope) resulted in a significant improvement in model fit across all common species’ distribution models. Adding further geodiversity data on surface materials resulted in a less consistent statistical improvement, but added considerable conceptual value to many individual rare and common SDMs.Conclusions
The geodiversity data used here helped us capture the abiotic environment’s heterogeneity and allowed for explicit links between the geophysical landscape and species’ ecology. It is encouraging that relatively simple and easily produced geodiversity data have the potential to improve SDMs. Our findings have important implications for applied conservation and support the need to consider geodiversity in management.10.
Doreen M. Houston Andrew E.P. Moore 《The Canadian veterinary journal. La revue veterinaire canadienne》2009,50(12):1263-1268
This study reports on trends in canine and feline urolithiasis in Canada during the past 10 years. Age, sex, breed of animals and mineral composition from 40 637 canine and 11 353 feline bladder uroliths submitted to the Canadian Veterinary Urolith Centre between 1998 and 2008 were recorded. Struvite and calcium oxalate uroliths comprised > 85% of all uroliths submitted. In dogs, the number of struvite submissions has declined and the number of calcium oxalate submissions has increased. Struvite uroliths were most common in female dogs and calcium oxalate uroliths in male dogs. The shih tzu, miniature schnauzer, bichon frisé, lhasa apso, and Yorkshire terrier were the breeds most commonly affected for both struvite and calcium oxalate uroliths. Urate uroliths were most common in male dalmatians. In cats, struvite submissions declined and calcium oxalate submissions remained constant. Struvite and calcium oxalate uroliths were common in domestic, Himalayan, Persian, and Siamese cats. Urate uroliths were over-represented in Egyptian maus. 相似文献