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   203篇
  免费   11篇
  国内免费   9篇
林业   6篇
农学   6篇
基础科学   16篇
  35篇
综合类   58篇
农作物   1篇
水产渔业   71篇
畜牧兽医   5篇
植物保护   25篇
  2024年   2篇
  2023年   3篇
  2022年   2篇
  2021年   7篇
  2020年   8篇
  2019年   7篇
  2018年   4篇
  2017年   5篇
  2016年   6篇
  2015年   7篇
  2014年   9篇
  2013年   18篇
  2012年   15篇
  2011年   11篇
  2010年   13篇
  2009年   7篇
  2008年   9篇
  2007年   15篇
  2006年   13篇
  2005年   10篇
  2004年   5篇
  2003年   3篇
  2002年   6篇
  2001年   8篇
  2000年   9篇
  1999年   5篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
排序方式: 共有223条查询结果,搜索用时 46 毫秒
1.
The contributions presented at the EIFAC Symposium on Fisheries and Society in 2000 are reviewed. There have been considerable advances in many sectors of inland fisheries over the past decade. Nowadays the value of inland fisheries to society is generally better understood and increasingly recognized. However, it was recognized that the allocation of fishery resources and their management could still be made more effective through more extensive application of the recent approaches and techniques discussed during the Symposium and reviewed in the paper.  相似文献   
2.
The French fisheries management regime is based on public and private ownership of fishing waters associated with a complex multilevel management system. A total of 730 operational commercial inland fisheries were examined by analysis of thematic interviews and questionnaires. Commercial fishermen are beginning to understand the nature of their own activity and its relationship to the concept of sustainable management. Nevertheless, fishermen have to face two major problems: first, they are poorly represented on decision making bodies where anglers are dominant, and secondly their activities are governed by two separate ministries. Opportunities for future development may lie in decision making at the catchment level.  相似文献   
3.
本文在分析武汉远城区都市农业发展机遇与挑战并存的背景后,提出武汉都市农业产业化势在必行,并结合武汉远城区农业发展实际,提出三项对策,包括整合科技资源,实现农业科技化;推行农机作业,实现农业机械化;探索良性机制,实现农业市场化。  相似文献   
4.
依据内陆河流域不同区域在水资源条件、气候条件、经济发展水平及水资源利用途径等方面的差异性,以及时序上水资源的利用规律,提出了旨在合理利用水资源,改善生态环境的水资源优化分配方法。通过在黑河流域的实例应用,论证了该方法的有效性。  相似文献   
5.
巴丹吉林沙漠湖泊形成的机理分析   总被引:11,自引:3,他引:11  
依据实际调查资料并结合前人研究成果,在探明区域水文地质条件的基础上,系统计算分析了沙漠区及外围盆地地下水的补给与排泄,发现沙漠区地下水补给量小于排泄量2.55×108 m3/a,不能解释内陆湖泊水量长久不衰的原因;而位于沙漠区西缘的黑河金塔-鼎新盆地地下水补给量大于排泄量2.66×108 m3/a,未见盆地内地下水位大幅度上升,多余的水量不知去向;与沙漠区衔接的其它盆地地下水资源匮乏且处于补排基本平衡的状态,根本无途径和多余的水量补给沙漠区.前人研究结果证实,横贯我国西北-东西的阿尔金大断裂的东延部分及其所形成的羽翼状断层带存在地表破碎带,且地势西高东低并具有良好的导水性,而这个地表破碎带通过了金塔-鼎新盆地和巴丹吉林沙漠,正好位于沙漠内陆湖泊群附近.而湖泊群一带存在大量钙华和钙质胶结层及湖水中3He/4He的比值,均表明湖泊水经过了深部地壳层的循环,加上黑河正义峡-哨马营段河水海拔高于湖泊群的佐证,认为黑河在金塔-鼎新盆地强烈渗漏所产生的地下水顺着阿尔金断裂自西向东源源不断地补给了巴丹吉林沙漠,经过目前还不为人知的深部循环方式,地下水在湖泊群地表破碎带向上运移形成上升泉,最终成为巴丹吉林内陆沙漠湖泊群水源的补给来源.  相似文献   
6.
Israel has a temperate climate with marked differences between the northern and southern regions. Rainfall ranges between 250 and 600 mm year−1 in the former and between only 25 and 200 mm year−1 in the latter. During the last 30 years, water consumption has increased markedly in all sectors. Although a water allocation for inland aquaculture is made, in most cases it is given the lowest priority, and aquaculturists have learned to contend with difficulties, and thrive on brackish water sources not fit for human consumption or agricultural crops. Since most water sources are already fully exploited, further development of all sectors will depend on their respective capacity to use recycled city water, desalinated brackish or sea water, or recycled pond water. In this respect, inland aquaculture is handicapped by public prejudices which will not allow the use of water from the first source and farms are still not able to cope with the cost of the second. Therefore, further development of inland aquaculture will depend on the capacity of farmers to use sea water, and to recycle pond water time and again to produce more fish with less (inland) water. Various strategies have already been developed in Israel and new ones are under study. These include water harvesting in dual-purpose reservoirs, recycling of pond water from one year to another, development of intensive flow-through systems based on recycled pond water and colleagues based on biofiltration.  相似文献   
7.
通过对水安全概念的描述,分析了河西内陆区水资源的利用及其安全现状,同时针对河西内陆区的具体概况,提出了内陆区水资源安全的区域经济发展模式、生态环境建设模式、水安全的水资源利用措施和水安全保障措施。  相似文献   
8.
我们曾将发病残存的日本对虾继续养殖作为亲虾,进行夏季高温育苗,所得到的虾苗在实验室里桶养,证明在人工饲养条件下它们是可成活和生长的,本实验还提示,若能解决水质净化问题,日本对虾甚至有可能移至内陆养殖。  相似文献   
9.
Fishing is a major recreational activity in Denmark, involving both inland and coastal waters. Anglers, aged 18–67, and amateur fishermen, aged 12–67, must hold a valid fishing permit. Fees are used for stocking, river restoration and fisheries research. All proposals for stocking inland waters require stocking plans based on the carrying capacity of the aquatic habitat in question. All stocking is undertaken using hatchery-reared fish that are the offspring, either of wild fish caught in nature for subsequent stripping, or of more or less domesticated fish stocks that have lived in captivity for several generations. Stocking is also subject to genetic guidelines. This paper reviews the status of fisheries in Danish inland waters, their regulation, socio-economic aspects, stocking, aquaculture and the main problems and trends.  相似文献   
10.
中国对虾往西北内陆咸水水域移植的生产性试养研究   总被引:8,自引:1,他引:8  
王慧  田荣庆 《海洋渔业》1997,19(1):9-12
本文介绍了通过采用引进河水、压碱降盐等改良水质的技术措施,使中国对虾首次成功地移植到内陆咸水水域。经过1个月的试养,中国对虾平均体长增长3.82 cm,平均体重为1.82 g。  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