首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   23篇
  免费   7篇
综合类   4篇
水产渔业   21篇
畜牧兽医   5篇
  2021年   1篇
  2020年   1篇
  2018年   3篇
  2016年   1篇
  2015年   2篇
  2014年   1篇
  2013年   1篇
  2012年   1篇
  2011年   2篇
  2010年   1篇
  2009年   1篇
  2008年   3篇
  2007年   1篇
  2006年   2篇
  2005年   2篇
  2004年   2篇
  2001年   1篇
  2000年   2篇
  1982年   1篇
  1972年   1篇
排序方式: 共有30条查询结果,搜索用时 15 毫秒
1.
A 25-year-old Quarterhorse mare was euthanized for a variety of medical reasons. At necropsy, 7 liver flukes, identified as Fascioloides magna, were recovered from the liver. This is the first report of F. magna in a horse.  相似文献   
2.
We report major element composition ratios for regions of the asteroid 433 Eros imaged during two solar flares and quiet sun conditions during the period of May to July 2000. Low aluminum abundances for all regions argue against global differentiation of Eros. Magnesium/silicon, aluminum/silicon, calcium/silicon, and iron/silicon ratios are best interpreted as a relatively primitive, chondritic composition. Marked depletions in sulfur and possible aluminum and calcium depletions, relative to ordinary chondrites, may represent signatures of limited partial melting or impact volatilization.  相似文献   
3.
4.
A 6-month-old female alpaca was presented for stranguria. Based on the history, physical examination findings, and radiographic studies, the alpaca was diagnosed with bladder outlet obstruction, secondary to pelvic displacement of the bladder, a condition previously unreported in camelids. Cystopexy was performed and the alpaca recovered unremarkably.  相似文献   
5.
We evaluate the current status of the global marine fisheries using the frameworks of conflict, food security and vulnerability. Existing trends suggest that there is likely to be greater food insecurity and fisheries conflicts due to issues such as: declining fishery resources; a North–South divide in investment; changing consumption patterns; increasing reliance on fishery resources for coastal communities; and inescapable poverty traps creating by low net resource productivity and few alternatives. Consequently, managing fisheries from a food security perspective will become increasingly necessary, and we therefore briefly review fisheries from the perspective of food security and evaluate it using a vulnerability framework. Specifically, we describe three key components of vulnerability (exposure, sensitivity and adaptive capacity) for selected fisheries. This is followed by proposals to build the adaptive capacity of fisheries and recommendations to avoid future conflicts. Adaptive capacity attributes include assets, social flexibility and organization attributes, and learning. We present some key ways to build these aspects of the fishery to reduce the many potential environmental and social threats that increase the vulnerability of fisheries. Recommendations include fewer subsidies, reduced capital investment, precautionary management to minimize risks of ecosystem collapse, conservation of remaining resources, diversified portfolios of production and markets, and greater equity in contracts and distribution. Further, we recommend a contextual diagnostic and environmental justice framework to assess a range of options for fishery governance.  相似文献   
6.
Uricotelism and low evaporative water loss in a South American frog   总被引:3,自引:0,他引:3  
A South American anuran (Phyllomedusa sauvagii) produced large amounts of semisolid urate when it was maintained on a diet of insects. Rates of evaporative water loss in Phyllomedusa sauvagii were only about 5 to 10 percent of those other anurans tested and were similar to those of lizards of comparable size.  相似文献   
7.
The status of fisheries requires establishing and evaluating benchmarks derived from unfished ecosystems. Habitats, environmental conditions, properties of the fish communities and management systems could potentially influence the variability surrounding benchmarks. Consequently, eighteen variables including habitat, number of species, life histories, thermal and productivity environments were tested for influences on reef fish biomass in 62 reefs within old high compliance closures along the east African coastline. Biomass and weighted life history characteristics were classified and described for total, fishable, target and non‐target groups. Benchmark biomass fell within a 95% confidence interval of ~1,030–1,250 kg/ha and equally distributed among target and non‐target groups. While some relationships were statistically significant, most were weak, poorly sampled (ocean exposed reefs), had uncertain relationships with biomass (number of species), or the explained variation was bounded within the above confidence intervals (habitat and environment). Therefore, a regional unfished biomass benchmark (B0) of 1,150 and 560 kg/ha is recommended for total and target biomasses, respectively. Weighted life history metrics indicate that the target had slower life histories than the non‐target fish communities. Consequently, they will be fished unsustainably if yield recommendations are derived from the total, resilient or non‐target fish life history metrics. The intrinsic rates of increase (r) and target categorization of biomass were the most influential metrics in estimating yields.  相似文献   
8.
  • 1. Justifying the designation of protected areas often depends on the ability to select areas in good ecological conditions, with high taxonomic richness, and unique habitats or species assemblage characteristics.
  • 2. The ecology of scleractinian coral and prosobranch snails were examined along the Masoala Peninsula of north‐eastern Madagascar using rapid assessment methods to evaluate the correspondence between unique invertebrate faunal characteristics and park designation.
  • 3. The reefs along this peninsula are in good ecological condition and have a coral and snail fauna similar to most of the western Indian Ocean, with no indications of local endemism in these groups. There was no relationship between the taxonomic richness of snails and corals. Corals were better at distinguishing locations based on taxonomic richness while snails were better based on unique faunal characteristics.
  • 4. Corals had the highest taxonomic richness on the extreme windward north and south and the lowest richness on the leeward side of the peninsula. The leeward side did, however, have an unusual habitat of corals growing on granite rock with a unique coral and snail fauna. A northern and southern assemblage characterized snail fauna on the windward side of the peninsula.
  • 5. The composite findings indicate that the currently designated park areas cover two of the three areas that have either high diversity or unique faunas.
Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
9.
10.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号