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11.
Bycatch in artisanal gill nets threatens the vaquita, Phocoena sinus, with extinction. In 2008 the Mexican government announced a conservation action plan for this porpoise, with three options for a protected area closed to gill net fishing. The probability of success of each of the three options was estimated with a Bayesian population model, where success was defined as an increase in vaquita abundance after 10 yr. The model was fitted to data on abundance, bycatch, and fishing effort, although data were sparse and imprecise. Under the first protected area option, the existing Refuge Area for the Protection of the Vaquita, bycatch was about 7% of population size, and probability of success was 0.08. Under the second option with a larger protected area, the probability of success was 0.35. The third option was large enough to eliminate vaquita bycatch and had a probability of success >0.99. Probability of success was reduced if elimination of vaquita bycatch was delayed or incomplete. Despite considerable efforts by the Mexican government to support vaquita conservation, abundance will probably continue to decline unless additional measures to reduce vaquita bycatch are taken, such as banning gill nets within the vaquita's range and developing effective alternative fishing gear. 相似文献
12.
Nathan J. P. Wintle Deborah A. Duffield Nélio B.
Barros Ronald D. Jones James M. Rice 《Marine Mammal Science》2011,27(4):E268-E278
Muscle samples from 105 marine mammals stranded along the Oregon and Washington coasts (2002–2009) were tested for levels of total mercury (THg) by Cold Vapor Atomic Fluorescence Spectrometry. The THg present is in the form of the highly toxic methylmercury. After normalizing tissue to 75% water weight, Steller sea lions and northern elephant seals exhibited the highest mean concentrations of THg followed by harbor seals, harbor porpoises, and California sea lions, 0.34 ± 0.278, 0.34 ± 0.485, 0.21 ± 0.216, 0.17 ± 0.169, and 0.15 ± 0.126 mg/kg normalized wet weight (ww), respectively. The mean normalized values demonstrate limited muscle methylmercury accumulation in these species in the Pacific Northwest. However, actual ww concentrations in some of the stranded carcasses may pose a risk to scavengers. Normalizing muscle mercury concentrations eliminated the variability from desiccation, and allowed for a clearer indication of the amount of mercury the animal accumulated before stranding. 相似文献
13.
Heide-Jørgensen MP Iversen M Nielsen NH Lockyer C Stern H Ribergaard MH 《Ecology and evolution》2011,1(4):579-585
The effects of climate change on marine ecosystems and in particular on marine top predators are difficult to assess due to, among other things, spatial variability, and lack of clear delineation of marine habitats. The banks of West Greenland are located in a climate sensitive area and are likely to elicit pronounced responses to oceanographic changes in the North Atlantic. The recent increase in sea temperatures on the banks of West Greenland has had cascading effects on sea ice coverage, residency of top predators, and abundance of important prey species like Atlantic cod (Gadus morhua). Here, we report on the response of one of the top predators in West Greenland; the harbour porpoise (Phocoena phocoena). The porpoises depend on locating high densities of prey species with high nutritive value and they have apparently responded to the general warming on the banks of West Greenland by longer residence times, increased consumption of Atlantic cod resulting in improved body condition in the form of larger fat deposits in blubber, compared to the situation during a cold period in the 1990s. This is one of the few examples of a measurable effect of climate change on a marine mammal population. 相似文献
14.
Understanding the population genetic structure is a prerequisite for conservation of a species. The degree of genetic variability
characteristic of the mitochondrial DNA control region has been widely exploited in studies of population genetic structure
and can be useful in identifying meaningful population subdivisions. To estimate the genetic profile of the Yangtze finless
porpoise (Neophocaena phocaenoides asiaeorientalis), an endangered freshwater population endemic to China, the complete mtDNA control region was examined in 39 individuals
belonging to seven different stocks inhabiting the middle and lower reaches of the Yangtze River. Very low genetic diversity
was found (nucleotide diversity 0.0011± 0.0002 and haplotypic diversity 0.65± 0.05). The mtDNA genetic pattern of the Yangtze
population appears to indicate a founder event in its evolutionary history and to support the marine origin for this population.
Analyses by Fst and Φst yielded statistically significant population genetic structure (Fst = 0.44, P < 0.05; Φst = 0.36, P < 0.05). These results may have significant implications for the management and conservation of the Yangtze finless porpoise
in the future. 相似文献
15.
Cetacean respiration usually happen in bouts. The most widely applied quantitative method used to analyze the structure of these bouts is the loge-survivorship analysis, based on the assumption that the respiratory intervals are distributed as negative exponentials. However, for the data collected from three captive Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis), we failed to obtain a convergent result with the application of loge-survivorship analysis. However, the two-Gaussian model, which was recently proposed to analyze the feeding behavior of cows, was successfully fitted to the data. According to the fitting results, the overall respiratory pattern of the captive Yangtze finless porpoises can be described as a dive with a mean duration of around 30–40 s, followed by two or three ventilations with a mean interval of approximately 9 s. The average intra-bout intervals during both active and inactive periods are constant at 7.7–9.9 s for all individuals. However, when shifting from active to inactive states, the adult male and female decrease their mean numbers of respirations per bout and average length of inter-bout respiratory intervals, while the estimates of both parameters increase for the juvenile female. It was pointed out that the two-Gaussian model might be more adequate for cetacean respiratory-bout structure analyses than the loge-survivorship technique. 相似文献
16.
Stephanie A. Norman Jessie Huggins Tim E. Carpenter James T. Case Dyanna M. Lambourn Jim Rice John Calambokidis Joseph K. Gaydos M. Bradley Hanson Deborah A. Duffield Sandra Dubpernell Susan Berta Matt Klope 《Marine Mammal Science》2012,28(3):E251-E266
In 2006–2007, an unusually high number of harbor porpoises (Phocoena phocoena) stranded along the Washington and Oregon coastlines. Spatiotemporal analyses were used to examine their ability to detect clusters of porpoise strandings during an unusual mortality event (UME) in the Pacific Northwest using stranding location data. Strandings were evaluated as two separate populations, outer coast and inland waters. The presence of global clustering was evaluated using the Knox spatiotemporal test, and the presence of local clusters was investigated using a spatiotemporal scan statistic (space–time permutation). There was evidence of global clustering, but no local clustering, supporting the hypothesis that strandings were due to more varied etiologies instead of localized causes. Further analyses at subregional levels, and concurrently assessing environmental factors, might reveal additional geographic distribution patterns. This article describes the spatial analytical tools applied in this study and how they can help elucidate the spatiotemporal epidemiology of other UMEs and assist in determining their causes. More than one spatial analytical technique should be used if the study objective is to detect and describe clustering in time and space and to generate hypotheses regarding causation of marine mammal disease and stranding events. 相似文献
17.
GUANG YANG LI GUO MICHAEL W. BRUFORD FUWEN WEI KAIYA ZHOU 《Biological journal of the Linnean Society. Linnean Society of London》2008,95(1):193-204
Phylogeographical patterns of intraspecific variation can provide insights into the population‐level processes responsible for speciation and yield information useful for conservation purposes. In the present study, three hundred and forty‐five base pairs of the mitochondrial DNA control region were sequenced to analyse the genetic diversity, population structure and history, and phylogeography of finless porpoises (Neophocaena phocaenoides) in Chinese and Japanese waters of the North Pacific. Nucleotide and haplotype diversities were 0.44% and 0.79 ± 0.01 for Chinese and Japanese waters, respectively, but varied significantly among populations. Analysis of molecular variance showed a high level of genetic structure between populations (ΦST = 0.61, P < 0.001; FST = 0.52, P < 0.001). Eleven of 18 haplotypes were restricted to a single population, common haplotypes were found in two to four populations, but no haplotype was found throughout Sino‐Japanese waters, suggesting multiple colonization events followed by limited gene flow. The inferred age of demographic expansion was from the end stage of the last ice age to the Holocene. No obvious phylogeographical pattern was revealed, including between saline and fresh water populations. A low level of genetic diversity for each population and high among‐population differentiation in haplotype frequency were revealed, which suggest a role for random genetic drift, recent demographic bottlenecks, and reduced or limited gene flow in these populations. Some conservation considerations, with special reference to the unique Yangtze population, are discussed. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 193–204. 相似文献
18.
J. S. Zheng X. L. Liao J. G. Tong H. J. Du M. C. Milinkovitch D. Wang 《Conservation Genetics》2008,9(4):1007-1009
The finless porpoise (Neophocaena phocaenoides) is one of the smallest cetacean species widely distributed in the shallow coastal waters of the Indo-Pacific Oceans. The
population size of the Yangtze subspecies (N. p. asiaeorientalis) has sharply decreased in the last two decades and access to objective data on its population structure and genetic diversity
would be of great assistance for their proper management. Here we report on the isolation of nine polymorphic microsatellite
using the “Fast Isolation by AFLP of Sequences Containing repeats” (FIASCO) protocol. Polymorphism was assessed using 30 porpoise individuals randomly sampled in the Yangtze River. The number
of alleles per locus varies from 2 to 9, with an average value of 5.56, whereas the ranges of observed and expected heterozygosities
were 0.300–0.633 (mean 0.496) and 0.473–0.804 (mean 0.659), respectively. 相似文献
19.
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