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   206篇
  免费   50篇
  国内免费   30篇
农学   1篇
  22篇
综合类   44篇
农作物   2篇
水产渔业   216篇
畜牧兽医   1篇
  2024年   3篇
  2023年   4篇
  2022年   6篇
  2021年   7篇
  2020年   22篇
  2019年   27篇
  2018年   9篇
  2017年   7篇
  2016年   14篇
  2015年   12篇
  2014年   12篇
  2013年   16篇
  2012年   11篇
  2011年   18篇
  2010年   15篇
  2009年   10篇
  2008年   20篇
  2007年   7篇
  2006年   23篇
  2005年   13篇
  2004年   8篇
  2003年   4篇
  2002年   1篇
  2001年   10篇
  2000年   5篇
  1995年   1篇
  1993年   1篇
排序方式: 共有286条查询结果,搜索用时 15 毫秒
61.
  • 1. Nubbins from 12 coral species were transplanted onto dead giant clam shells at three sites in a lagoon near Bolinao, north‐western Philippines. Transplants were attached using three types of adhesives: cyanoacrylate glue (SG), epoxy putty (EP) and marine epoxy (ME) and were monitored over five months for detachment, in situ mortality and natural self‐attachment by tissue growth.
  • 2. Corals attached with SG showed a significantly higher rate of detachment (logrank test) than those attached with either EP or ME (P<0.001 in each case). Also, those attached with EP showed a higher rate of detachment than corals attached with ME (logrank=6.46, P<0.05).
  • 3. ANOVA (P>0.05) and survival analysis (logrank=2.85, P>0.05) showed no among‐adhesives differences in in situ mortality. Among the species used, Porites cylindrica, Pavona frondifera, Heliopora coerulea and Porites rus had the highest survivorship with 82%, 80%, 76% and 73%, respectively, of nubbins alive at the end of the experiment and also displayed the highest cumulative rates of self‐attachment. Species with the lowest survival rates included Acropora muricata and four pocilloporids.
  • 4. Although there was no significant difference in the number of self‐attaching transplants among the adhesives, corals transplanted using ME and EP self‐attached earlier than those transplanted using SG (logrank=11.19, P<0.01).
  • 5. Results from this study highlight the importance of selecting the appropriate means of attaching corals to substrates and carefully considering species‐specific traits of candidate corals for transplantation.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
62.
澄海莱芜人工鱼礁集鱼效果初步评价   总被引:11,自引:2,他引:9  
2003和2007年分别对澄海莱芜人工鱼礁区进行了投礁前的本底调查和投礁后的跟踪调查。结果表明,投礁后礁区海域游泳生物的资源密度明显比投礁前高,增加了25.63倍;礁区海域各类资源种类均比投礁前丰富,总种数由投礁前的23种增加至41种,比投礁前增加了0.78倍,其中,蟹类种数增加最多,增加了1.75倍;在本底调查中没有出现的经济种类龙头鱼Harpodon nehereus和红星梭子蟹Portunus sanguinolentus在跟踪调查中已成为主要优势种;Shannon—Wienver多样性指数(H’)在礁区和对比区均比投礁前有所增加。表明鱼礁投放后,鱼礁区集鱼效果和群落结构明显改善,人工鱼礁建设取得了明显的生态效益和经济效益。  相似文献   
63.
通过2019年室内和野外附着实验,检验了牡蛎壳(新壳和旧壳)和生物膜(有生物膜和无生物膜)对牡蛎附着量的影响。室内附着实验表明,在生物膜处理下新壳上牡蛎附着量显著高于旧壳(P<0.05);而在无生物膜对照组中,新、旧壳上牡蛎附着量无显著差异(P>0.05)。野外附着实验发现,生物膜显著提升了旧壳上牡蛎附着量,但对新壳上牡蛎附着量无显著影响。通过2020年野外附着实验,检验了牡蛎壳(新壳和旧壳)和潮区(滩面以上0.6 m和1.1 m)对牡蛎和藤壶附着量的影响。牡蛎附着量在每个潮区中,15 d、45 d和70 d时新壳均显著高于旧壳(P<0.05)。藤壶附着量仅在0.6 m潮区中、15 d时新壳显著高于旧壳,而45 d和70 d时,各潮区中新、旧壳上藤壶附着量均无显著差异(P>0.05)。研究发现,总体来看新壳的附苗效果好于旧壳,这种差异涵盖了整个牡蛎繁殖、附着及补充的高峰期。因此,牡蛎礁修复中应优先选取新壳作为底物。  相似文献   
64.
GIS-assisted site selection for artificial reefs   总被引:3,自引:0,他引:3  
  相似文献   
65.
嵊泗人工鱼礁建设初期效果评价   总被引:8,自引:0,他引:8  
基于2004年渔业资源的本底调查和2005年四个季度的跟踪调查结果,对嵊泗人工鱼礁一期工程的建设效应进行了初步评估,得到如下结果:(1)投礁后,礁区渔业资源生物量的相对变化率呈现上升趋势,平均增幅达75%,到了秋季生产力达到2004年同期的4倍多,而对照区的资源量则以36%的平均幅度减小;(2)投礁前,各个多样性指数相差不多,投礁后,鱼礁区的多样性值逐渐赶上并超过对照区,平均高出25%左右;(3)投礁前后,对照区的经济种种类数维持在10种左右,而鱼礁区随着礁体的投放,经济种增加,多达25种。结果表明,鱼礁投放后,鱼礁区生产力得到了提高,群落结构也得以明显改善,人工鱼礁的经济、生态效应已有良好的初步体现。  相似文献   
66.
为了解经过不同表面处理的人工鱼礁模板的附着生物群落特征,于2014年8月对大亚湾圆洲岛已投放的鱼礁模板进行采样调查.结果表明,共采集和鉴定出附着生物39种,黑缘牡蛎(Ostrea nigromarginata)占据附着生物优势种的绝对地位;经过表面处理的混凝土模块的附着生物生物量及丰度较高,而红砖、花岗岩板和未经表面处理的钢筋混凝土模板的附着生物生物量及丰度都很低;附着生物的生物量和丰度与其群落特征的变化未表现出一致的规律性.  相似文献   
67.
采用文献查阅、海域实地调查相结合的方法,总结国内外海洋牧场的发展与现状,分析广东人工鱼 礁、增殖放流和国家级海洋牧场示范区的建设历程,海洋牧场相关产业的发展现状和存在问题。广东建有 50 座 生态型人工鱼礁区、3 个大型人工鱼礁示范区、1 个地方人工鱼礁区和 15 个国家级海洋牧场示范区,合计海域 面积 1 499.68 km2 ,建造投放礁体 200.4 万空 m3 。目前广东海洋牧场存在管理机制不完善、发展理念和认识不统一、 用海海域权责不清、建设技术标准和规范缺乏、科技化程度低、产业化开发受限等问题。基于此,提出广东海 洋牧场发展的对策:坚持生态优先,加强多部门统筹协作;创建有利于市场化运作的管理模式;突破海域权属 问题;建立广东海洋牧场建设技术标准体系;加强广东海洋牧场建设的基础和关键共性技术研究;因地制宜建 立广东海洋牧场产业化模式。了解广东海洋牧场的发展现状,借鉴国内外相关经验探究海洋牧场产业的发展对策, 可为广东海洋牧场有效管理、高效可持续开发,以及实现广东海洋牧场三产融合发展提供参考。  相似文献   
68.
A market survey and review of government statistics were carried out to establish imports and exports of marine ornamental fishes into and out of Hong Kong, and to examine the local trade in terms of volume, value and species composition. Official government import figures for marine aquarium fishes were available from 1984 to 1991 and from 1997 and 1998. When compared with net imports, export and re-export volumes over the 15-year period were small, indicating that most imports entered the local market, or were exported unrecorded. The market survey of marine aquarium shops in Hong Kong was carried out between August 1996 and January 1997. From this survey, an annual estimate of 957,563 coral reef fish was calculated for the local trade, valued at HK$57,453,780, with a mean retail price of HK$60 per fish. These figures account for an estimated 2–3% of the global value and volume of marine aquarium fish trade, according to 1992 figures and, compared with government figures, indicate that official declarations of imports are underreported by at least 2–3 fold. A total of 342 marine aquarium fish species, from 49 families, were recorded with about 60% belonging to the families Labridae, Chaetodontidae, Pomacanthidae and Pomacentridae. It was estimated that a large proportion of the trade was in juvenile fishes and almost all fish were less than 10cm in standard length. It was common to see fishes in poor condition, species hard to maintain in captivity, or those listed for conservation concern, on sale. There are no regulations for local traders of live marine fishes other than those relating to either protected species or animal welfare. Licensing of traders in marine fishes could be introduced under existing Hong Kong legislation if fishes were to be re-classified as animals. This is strongly recommended as a step towards regulating and managing the trade in Hong Kong.  相似文献   
69.
Reef fishes are significant socially, nutritionally and economically, yet biologically they are vulnerable to both over‐exploitation and degradation of their habitat. Their importance in the tropics for living conditions, human health, food security and economic development is enormous, with millions of people and hundreds of thousands of communities directly dependent, and many more indirectly so. Reef fish fisheries are also critical safety valves in times of economic or social hardship or disturbance, and are more efficient, less wasteful and support far more livelihoods per tonne produced than industrial scale fisheries. Yet, relative to other fisheries globally, those associated with coral reefs are under‐managed, under‐funded, under‐monitored, and as a consequence, poorly understood or little regarded by national governments. Even among non‐governmental organizations, which are increasingly active in tropical marine issues, there is typically little focus on reef‐associated resources, the interest being more on biodiversity per se or protection of coral reef habitat. This essay explores the background and history to this situation, examines fishery trends over the last 30 years, and charts a possible way forward given the current realities of funding, capacity, development patterns and scientific understanding of coral reef ecosystems. The luxury live reef food‐fish trade is used throughout as a case study because it exemplifies many of the problems and challenges of attaining sustainable use of coral reef‐associated resources. The thesis developed is that sustaining reef fish fisheries and conserving biodiversity can be complementary, rather than contradictory, in terms of yield from reef systems. I identify changes in perspectives needed to move forward, suggest that we must be cautious of ‘fashionable’ solutions or apparent ‘quick fixes’, and argue that fundamental decisions must be made concerning the short and long‐term values of coral reef‐associated resources, particularly fish, for food and cash and regarding alternative sources of protein. Not to address the problems will inevitably lead to growing poverty, hardship and social unrest in many areas.  相似文献   
70.
Cues from the moon influence synchrony in growth, feeding, migration, behaviour and reproduction of many reef fishes. Compared with comprehensive studies on the annual and daily activities of fish, few physiological studies have paid attention to the importance of lunar cues in reproductive activities. We review mutual and interesting relationships between fish reproduction and environmental changes induced by the moon, with particular emphasis on the reproductive activity of the rabbitfishes (Siganidae). Rabbitfish species exhibit, in nature, a definitive reproductive season, which differs among the tropical areas. During the reproductive season, synchronous spawning of rabbitfish is associated with a particular lunar phase. The lunar phase used by the respective species is similar in different regions on the earth. Histological observations revealed that gonads develop synchronously towards a peak around the spawning lunar phase, after which the gonads return to spent condition. Concomitant with gonadal development, sex steroid hormones were produced under the influence of gonadotropin (GtH). Injections of human chronic gonadotropin (hCG) to the fish that are undergoing active spermatogenesis accelerated testicular maturation. These results suggest that hormonal response in maturing the gonads in rabbitfish is under the regulation of GtH, and that pituitary secretion of GtH according to the lunar cycle accounts for the lunar rhythm in gonadal development. We speculate that the cues from the moon can be recognized by the higher parts of the hypothalamus–pituitary–gonadal axis. Possible relationships between exogenous environmental factors and the lunar‐reproductive rhythm are also discussed.  相似文献   
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