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   951篇
  免费   161篇
  国内免费   59篇
林业   4篇
农学   14篇
基础科学   2篇
  68篇
综合类   194篇
农作物   2篇
水产渔业   875篇
畜牧兽医   10篇
植物保护   2篇
  2024年   6篇
  2023年   36篇
  2022年   15篇
  2021年   50篇
  2020年   68篇
  2019年   78篇
  2018年   48篇
  2017年   65篇
  2016年   44篇
  2015年   31篇
  2014年   59篇
  2013年   60篇
  2012年   56篇
  2011年   63篇
  2010年   46篇
  2009年   48篇
  2008年   41篇
  2007年   27篇
  2006年   44篇
  2005年   52篇
  2004年   44篇
  2003年   31篇
  2002年   19篇
  2001年   44篇
  2000年   32篇
  1999年   22篇
  1998年   9篇
  1997年   3篇
  1996年   5篇
  1995年   7篇
  1994年   4篇
  1993年   3篇
  1992年   8篇
  1991年   2篇
  1990年   1篇
排序方式: 共有1171条查询结果,搜索用时 15 毫秒
81.
水产院校《组织胚胎学》精品课程建设的改革与探索   总被引:1,自引:0,他引:1  
精品课程建设是深化教学改革、提高教学质量的重要举措之一。从师资队伍建设、教学环节的优化、教学方法和手段的革新、教学管理的规范等方面阐述了对水产院校《组织胚胎学》精品课程建设的改革和探索。  相似文献   
82.
金显仕  田洪林  单秀娟 《水产学报》2023,36(11):119310-1-119310-10

近海是众多渔业生物的产卵场、育幼场和索饵场,也是优良渔场,支撑着我国海洋渔业资源的世代发生量和“海上粮仓”的可持续产出。近海渔业贡献了80%~90%海洋捕捞产量,在保障水产品供给、增加渔民收入、促进沿海地区海洋经济发展等方面发挥了重要作用。新中国成立以来,以近海渔业资源为切入点,我国科研人员围绕“海洋渔业资源开发与可持续利用”的关键科技问题,系统开展了一系列渔业资源调查与评估、基础与应用基础研究、技术研发工作,取得了多项创新性成果,支撑了我国海洋渔业资源合理利用、科学养护与管理。渔业资源研究重点与渔业资源开发利用程度和渔业发展休戚相关,本文结合不同时期国家渔业发展战略,系统回顾了1950年代以来我国近海渔业资源研究4个发展阶段 (起步—发展阶段、快速发展阶段、综合研究阶段和新发展阶段)的特点、研究重点、调查装备及平台建设情况等;梳理了我国在近海渔业资源数量变动与渔场探查、渔业资源高效开发利用、渔业资源调查评估技术研发、科学规范的水生生物资源养护体系形成和海洋生态系统动力学等研究进展和代表性成果,及其对我国近海渔业发展、管理与资源养护政策调整的支撑作用;明确了未来渔业资源研究要注重多学科研究和综合性调查,深入解析渔业生态系统结构与功能的机制和机理,结合经济、社会等因素研发新的渔业资源利用与管理模式,实现“开发中保护,保护中开发”,支撑资源养护型近海捕捞业实施和渔业高质量发展。

  相似文献   
83.
王鲁民  王忠秋 《水产学报》2023,36(11):119716-1-119716-11

综合应用船舶、机械、信息、新材料等技术,从海洋中捕捞经济渔获物并综合利用,是现代海洋捕捞业的主要特征。海洋捕捞技术的发展和创新,对保障我国食物安全、保护近海生态与资源、实现渔民增收和新渔村建设、推动渔业产业结构调整和转型、维护我国海洋权益等方面具有非常重要的作用。本文通过简析海洋捕捞渔场探测、渔具渔法与高效自动化辅渔助渔技术等方面的研究进展,提出海洋捕捞技术的重点发展方向,以期为我国海洋捕捞实现节能高效、生态友好和资源可持续利用,海洋捕捞技术升级和产业高质量发展提供参考。

  相似文献   
84.
卢洁  邹磊磊 《水产学报》2024,15(3):039302-1-039302-14

区域性渔业管理组织 (RFMO)是当前国际公海渔业管理的主要机制,也是公海渔业管理研究的重点之一。西方远洋渔业发展起步早,国外学者较早开始关注RFMO,开展了大量的RFMO理论和实践研究。本文采用文献计量分析梳理了RFMO国外研究,并以知识图谱方式呈现国外研究进展与热点。定量分析结果显示,RFMO国外研究数量总体呈上升趋势;研究领域涉及渔业、环境和国际关系等自然和社会科学;美国、英国和澳大利亚等对研究的关注度较高。此外,关键词分析结果表明,国外学者比较关注RFMO视角下的渔业管理、南大洋等重要海域、气候变化、生态系统、海洋保护区、海洋法等问题,研究重点呈现出从生物资源生物学逐步转向公海生物资源管理和海洋生态系统保护等的趋势。在此基础上,本文进一步定性分析了RFMO国外研究,发现RFMO国外研究更敢于以创新性研究视角探索传统的RFMO研究话题,研究方法更趋科学性,注重研究的辩证性、整体性、比较性和连续性,研究意识也比较超前,善于发现RFMO研究的新领域。本文通过定量和定性分析RFMO研究文献,探究RFMO国外研究进展,为国内学者切实提升RFMO研究的深度和广度提供参考和思路。

  相似文献   
85.
  1. The ocean crisis is urgent and central to human wellbeing and life on Earth; past and current activities are damaging the planet's main life support system for future generations. We are witnessing an increase in ocean heat, disturbance, acidification, bio‐invasions and nutrients, and reducing oxygen levels. Several of these act like ratchets: once detrimental or negative changes have occurred, they may lock in place and may not be reversible, especially at gross ecological and ocean process scales.
  2. Each change may represent a loss to humanity of resources, ecosystem function, oxygen production and species. The longer we pursue unsuitable actions, the more we close the path to recovery and better ocean health and greater benefits for humanity in the future.
  3. We stand at a critical juncture and have identified eight priority issues that need to be addressed in unison to help avert a potential ecological disaster in the global ocean. They form a purposely ambitious agenda for global governance and are aimed at informing decision‐makers at a high level. They should also be of interest to the general public.
  4. Of all the themes, the highest priority is to rigorously address global warming and limit surface temperature rise to 1.5°C by 2100, as warming is the pre‐eminent factor driving change in the ocean. The other themes are establishing a robust and comprehensive High Seas Treaty, enforcing existing standards for Marine Protected Areas and expanding their coverage, especially in terms of high levels of protection, adopting a precautionary pause on deep‐sea mining, ending overfishing and destructive fishing practices, radically reducing marine pollution, putting in place a financing mechanism for ocean management and protection, and lastly, scaling up science/data gathering and facilitating data sharing.
  5. By implementing all eight measures in unison, as a coordinated strategy, we can build resilience to climate change, help sustain fisheries productivity, particularly for low‐income countries dependent on fisheries, protect coasts (e.g. via soft‐engineering/habitat‐based approaches), promote mitigation (e.g. carbon storage) and enable improved adaptation to rapid global change.
  相似文献   
86.
Overfishing may seriously impact fish populations and ecosystems. Marine protected areas (MPAs) are key tools for biodiversity conservation and fisheries management, yet the fisheries benefits remain debateable. Many MPAs include a fully protected area (FPA), restricting all activities, within a partially protected area (PPA) where potentially sustainable activities are permitted. An effective tool for biodiversity conservation, FPAs, can sustain local fisheries via spillover, that is the outward export of individuals from FPAs. Spillover refers to both: “ecological spillover”: outward net emigration of juveniles, subadults and/or adults from the FPA; and “fishery spillover”: the fraction of ecological spillover that directly benefits fishery yields and revenues through fishable biomass. Yet, how common is spillover remains controversial. We present a meta‐analysis of a unique global database covering 23 FPAs worldwide, using published literature and purposely collected field data, to assess the capacity of FPAs to export biomass and whether this response was mediated by specific FPA features (e.g. size, age) or species characteristics (e.g. mobility, economic value). Results show fish biomass and abundance outside FPAs was higher: (a) in locations close to FPA borders (<200 m) than further away (>200 m); (b) for species with a high commercial value; and (c) in the presence of PPA surrounding the FPA. Spillover was slightly higher in FPAs that were larger and older and for more mobile species. Based on the broadest data set compiled to date on marine species ecological spillover beyond FPAs' borders, our work highlights elements that could guide strategies to enhance local fishery management using MPAs.  相似文献   
87.
Abstract  Discarding practices from 110 fishing operations in a Mediterranean small-scale fishing fleet (Patraikos Gulf, western Greece) from August 2004 to July 2005 were analysed. On average, 1 kg of fish was discarded per fishing operation (10% of the catch). The reasons for discarding were: low commercial value (78% of discards), damage at sea before retrieval of the gear (5%), and bad handling on-board (17%). More than half of discards belonged to Spicara flexuosa (L.), Lepidopus caudatus (Euphrasen), Sardinella aurita Valenciennes and Merluccius merluccius (L.). The bulk of discards of each species were associated with a single fishing method (metier). A Generalized Linear Model (Delta-X – error-model) indicated that, when discards were present, significant differences existed in the discard ratio among different métier groups (groups comprising métiers with similar characteristics). Longlines and trammel nets with small mesh-sizes had the highest discard ratios. Discarding practices for the species Diplodus annularis (L.), S. aurita , Squilla mantis (L.), S. flexuosa and Scorpaena scrofa (L.) did not follow a consistent pattern (these species were either fully discarded or fully retained during a fishing operation). The decision seemed to be dependent on market demands rather than fish size. Significant correlation was found between discarded and catch weight, but the presence of many outliers indicated deviance from a case where discards are high when there is an abundant catch. The findings of the study imply that monitoring and management should be carried out preferably on the métier level. Discards could be reduced by technical measures, controlling effort regulations and by improving working conditions on-board fishing vessels.  相似文献   
88.
  • 1. The implications of shrinkage associated with desiccation and ethanol preservation for seahorses (genus Hippocampus) were investigated using Hippocampus guttulatus (European long‐snouted seahorse) as a model. Specifically, this research addressed the implications of preservation for taxonomy and life history studies and the application of minimum size limits (MSL) for managing seahorse trade.
  • 2. In 2004, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) listed all seahorse species on its Appendix II, and recommended a 10 cm MSL as an interim means of ensuring sustainable international trade. Inconsistencies in seahorse measurement methods and repeatability posed challenges for applying the MSL. Moreover, the shrinking effect of desiccation on body length observed in other fish was assumed to be negligible for seahorses because of their high degree of ossification.
  • 3. Changes in seahorse sizes were measured following immersion in ethanol and desiccation. H. guttulatus shrank on average by 0.1–2.3% when preserved in ethanol and 3.0–6.4% when dried, depending on the trait measured. Similar trends were observed in a sample of H. kuda (yellow seahorse). Specimen posture during drying, and measurement methods also influenced estimates of size.
  • 4. Based on the shrinkage observed, 14–44% of captured seahorses that are dried could shrink to below the recommended MSL, even if all seahorses were longer than the MSL at capture. This demonstrates that small changes in body lengths can have significant implications for trade of species managed with size limits.
  • 5. Recommendations are to (1) standardize seahorse measurement methods, (2) consider the effects of preservation and measurement technique on body lengths, and apply appropriate corrections in comparative studies and when developing fisheries management strategies, and (3) adjust size limits at the point of capture to ensure retained seahorses comply with the CITES recommended MSL.
Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
89.
对福建省淡水渔业学科发展的一点思考   总被引:1,自引:0,他引:1  
淡水渔业在福建省渔业中占据重要的地位也具有较大的空间。淡水渔业的发展必须依靠淡水渔业科技的先行发展。为此,本文首先介绍福建省淡水渔业的现状;其次,阐述了发展淡水渔业科技首先要解决的几个认识上的问题;最后提出发展我省淡水渔业对本学科提出的几点要求和未来学科发展的几个重点领域,希望本文对淡水渔业科技的发展具有借鉴意义。  相似文献   
90.
Although freshwater fish stocking is widely used by managers, quantitative assessments of stocking practices are lacking in many countries. The general objective of the present study was to determine the quantity and characteristics of fish stocking in metropolitan France. Using a survey-based approach, stocking practices for 2013 by recreational angling clubs in France were quantified, which represented the bulk of fish stocking undertaken in that year. Stocking was found to be practiced by 88.6% of angling clubs in France, representing, on average, 65% of their annual budget. Overall, 22 species were stocked, including 13 native and nine non-native species, with strong variations among species in terms of life stages and body sizes used for stocking. Using Bayesian modelling, a total biomass of 2.029 t, representing approximately 90 million fishes, was estimated to be stocked in France in 2013. In terms of biomass, the most widely stocked species were rainbow trout Oncorhynchus mykiss (Walbaum), brown trout Salmo trutta L., roach Rutilus rutilus (L.), common carp Cyprinus carpio L. and northern pike Esox lucius L. A stocking volume of approximately 60 fishes or 1.5 kg of fish biomass per angler per year seems commonplace in industrialised countries for which data are available.  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