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1.
Methods of assessing extinction risk in marine fishes 总被引:1,自引:0,他引:1
Nicholas K Dulvy Jim R Ellis Nicholas B Goodwin Alastair Grant John D Reynolds & Simon Jennings 《Fish and Fisheries》2004,5(3):255-276
The decline and disappearance of species from large parts of their former geographical range has become an important issue in fisheries ecology. There is a need to identify which species are at risk of extinction. The available approaches have been subject to considerable debate – particularly when applied to commercially exploited species. Here we have compiled methods that have been used or may be used for assessing threat status of marine organisms. We organize the methods according to the availability of data on the natural history, ecology and population biology of species. There are three general approaches to inferring or assessing extinction risk: (i) correlative approaches based on knowledge of life histories and ecology; (ii) time‐series approaches that examine changes in abundance; and (iii) demographic approaches based on age‐ or stage‐based schedules of vital rates and fisheries reference points. Many methods are well suited to species that are highly catchable and/or have relatively low productivity, but theory is less well developed for assessing extinction risk in species exhibiting narrow geographical distributions or ecological specialization. There is considerable variation in both definitions of extinction risk and the precision and defensibility of the available risk assessment methods, so we suggest a two‐tiered approach for defining and assessing extinction risk. First, simple methods requiring a few easily estimated parameters are used to triage or rapidly assess large numbers of populations and species to identify potentially vulnerable populations or species. Second, the populations and species identified as vulnerable by this process can then be subject to more detailed and rigorous population analysis explicitly considering sources of error and uncertainty. 相似文献
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概述了毛刺科及毛刺属(Trichodorus Cobb, 1913),拟毛刺属(Paratrichodorus Siddiqi, 1974),单毛刺属(Monotrichodorus Andrassy, 1976)和异毛刺属(Allotrichodorus Rodriguez-M, Sher &; Siddiqi, 1978)鉴别特征,列出迄今已描述的94种1亚种和1裸名种的名录。 相似文献
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日本肯定列表制度对我国出口食用菌的影响和对策 总被引:5,自引:0,他引:5
分析了日本肯定列表制度、我国出口食用菌的现状和问题以及肯定列表制度对我国出口食用菌的影响.提出了加强农残监控、强化原料基地管理、严格卫生注册登记管理、加强农资销售市场管理、加强食用菌农药使用的研究与指导、完善标准体系6个方面的应对措施。 相似文献
5.
Joe A TobiasNathalie Seddon 《Biological conservation》2002,108(2):199-212
The subdesert mesite, a terrestrial non-passerine bird endemic to the Mikea Forest of southwest Madagascar, is currently classified as globally threatened (category: Vulnerable). However, accurate assessment of threat in accordance with the IUCN Red List criteria (A, B and C) requires data on effective population size, area of habitat occupied and rate of decline, none of which is available for this species. Here we present the first empirical estimates of its population size using five complementary methods, three incorporating data on territory size and two using data gathered during call-playback surveys conducted throughout its entire global range. Estimates vary from 98,000 to 152,000 individuals, with the most reliable possibly being that generated by distance sampling (115,000). This figure is more than an order of magnitude greater than the only published estimate of <10,000 individuals. By analysing data on forest cover change, we estimate the population of the subdesert mesite to have declined by, at most, 10% in three generations. Although the rate of deforestation in 1994-1999 is double that calculated for 1962-1994, it is deemed unlikely that the population will decline by 20% over the next three generations. As such the species fails to meet criterion A. Although the subdesert mesite's range and area of occupancy are small, they are not fragmented and do not comprise fewer than 10 locations. Consequently, this species does not meet criterion B. Further, the species fails to meet criterion C, for which a maximum of 10,000 mature adults is required. According to IUCN (2000 Red List of Threatened Species) this species should therefore be downlisted in status. We discuss why it still warrants conservation attention and suggest the need for modifications to the criteria thresholds in relation to basic information about the ecology and taxonomic distinctness of species. 相似文献
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John P. Simaika 《Biological conservation》2009,142(3):638-651
The Red List can be used a gauging tool by conservationists to assess which species require focused conservation attention. Mapping the relative distributions of species, and identification of centers of richness, endemism and threat are a first step towards site-oriented conservation action. We use here a specially developed biodiversity index, based on three weighted sub-components assigned to each species: geographical distribution, Red List status, and sensitivity to habitat change. We test this approach using what is called here the Dragonfly Biotic Index (DBI) to prioritize sites for conservation action, with special emphasis on species occurrence in three global hotspots in southern Africa. Using a selected set of the 23 top prioritized sites, we compare the DBI’s performance to that of a rarity-complementarity algorithm. As with several other taxa, local endemism levels are highest in the Cape Floristic Region (CFR), while richness is highest in the north east, particularly in the stream systems of the Maputaland-Pondoland-Albany (MPA) hotspot. Red Listed Odonata species are also concentrated in the CFR, while richness is highest in the MPA hotspot. Site prioritization using the DBI reveals that CFR sites protect Red Listed taxa rather well, despite the fact that catchments are only partially protected. The DBI demonstrates high levels of redundancy in representing Red Listed species, in other words, the same species are represented in several catchments. The value in the DBI thus lies in maximizing redundancy (i.e. representation) of globally Red Listed species. The rarity-complementarity algorithm represents all species, but without greater emphasis on the rare and threatened (i.e. Red Listed) species. We conclude that the DBI is of great value in selecting biodiversity hotspots, while the algorithm is useful for selecting complementarity hotspots. We identify protection gaps and thus recommend continued searches in centers of endemism and existing reserves, as well as gap areas. These searches will hone Red List assessments and identify priority sites, as well as monitor already-identified sites for changes in quality of habitat. 相似文献
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赵国志 《农业工程技术:农产品加工》2006,(2):20-25
对在2006年5月29日起实施的日本《肯定列表制度》的内容,制定过程和原则方法做了简明解说.对了解食品标准内容与制定程序和方法有一定的参考作用. 相似文献