全文获取类型
收费全文 | 442篇 |
免费 | 57篇 |
国内免费 | 70篇 |
专业分类
林业 | 30篇 |
农学 | 27篇 |
基础科学 | 46篇 |
74篇 | |
综合类 | 139篇 |
农作物 | 5篇 |
水产渔业 | 229篇 |
畜牧兽医 | 10篇 |
园艺 | 1篇 |
植物保护 | 8篇 |
出版年
2024年 | 3篇 |
2023年 | 17篇 |
2022年 | 17篇 |
2021年 | 23篇 |
2020年 | 21篇 |
2019年 | 24篇 |
2018年 | 29篇 |
2017年 | 17篇 |
2016年 | 16篇 |
2015年 | 24篇 |
2014年 | 32篇 |
2013年 | 26篇 |
2012年 | 39篇 |
2011年 | 42篇 |
2010年 | 32篇 |
2009年 | 40篇 |
2008年 | 26篇 |
2007年 | 15篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 22篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1991年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
排序方式: 共有569条查询结果,搜索用时 265 毫秒
21.
Friedrich Ladich 《Fish and Fisheries》2022,23(1):227-238
Predation is a major ecological constraint shaping behaviour and communication in animals. Several fish species are known to modify their foraging, agonistic and reproductive behaviour in the presence of predators. However, close to nothing is known about how predators affect sound production in fishes. This paper reviews how vocal fish increase their chance of survival by modifying intraspecific acoustic communication and by producing sounds directed towards predators. Field studies showed that toadfish, drums and squirrelfish reduced the number and loudness of calls when dolphin sounds were played back. These studies lack behavioural observations, leaving the question open how individual fish respond to predation threat. Croaking gouramis (Trichopsis vittata, Osphronemidae) reduced acoustic and visual signalling during dyadic contests and refrained from escalated behaviour when detecting a predator in an adjacent tank. This indicates that gouramis increase their vigilance by reducing agonistic behaviour. Vocal fish have been observed to emit sounds when predators approach or when being caught. However, none of the predators (or even conspecifics nearby) responded to these calls. Therefore, the term “predator-related” sound has been introduced in this paper to avoid implying unproven functions (alarm, startling, warning, distress and disturbance). Interestingly, the readiness of numerous taxa (e.g. catfishes) to vocalize when hand-held or netted was frequently exploited to investigate sound production in fish in relation to weight, sex, sonic organs, temperature or phylogeny. Increasing levels of noise in aquatic habitats call for more research on predator–prey interactions because of potential negative effects on detection of sounds produced by predators or prey. 相似文献
22.
Yuuki Kawabata Junichi Okuyama Hiromichi Mitamura Kimio Asami Kenzo Yoseda Nobuaki Arai 《Fisheries Science》2007,73(5):1147-1154
ABSTRACT: Post-release movement and diel activity patterns of hatchery-reared and wild black-spot tuskfish were examined using ultrasonic telemetry. Five hatchery-reared and four wild fish were released in the sandy bottom of Urasoko Bay, Ishigaki Island, Okinawa, Japan, and monitored using automated monitoring receivers from November 2005 to February 2006. Both hatchery-reared and wild fish tended to stay near the release site for over two weeks, before leaving the release site. Both hatchery-reared and wild tuskfish showed diurnal rhythm intermittently; signals were recorded more frequently in the daytime and less frequently in the nighttime, suggesting that the fish of both origins were active during the day and inactive during the night. These findings indicate that the one-year-old hatchery-reared tuskfish have some consistent behavioral characteristics with those of the wild. 相似文献
23.
渔业资源管理目标定量确定的探讨 总被引:1,自引:0,他引:1
本文主要探讨渔业资源管理目标定量确定(包括渔业种类及其可捕规格和产量的确定)过程中常用的数学方法,并指出各种方法的应用范围。 相似文献
24.
25.
深水抗风浪网箱监测系统研制方案的探讨 总被引:5,自引:3,他引:5
探讨一种声学监测方案,用高频、窄脉冲和分裂波束技术,实时监测养殖鱼的进食、生长情况,随时评估网箱内总量的增长情况,并且从水产行业的成本可承受性的实际出发,将成本控制在用户可接受的水平上。 相似文献
26.
27.
闽东北外海底层流刺网作业渔获的银头鱼群体由1~6龄11个世代构成,以2、3和4龄占优势;体长优势组为210~270mm,体重优势组为200~400g,体长与体重的关系W=2.1120×10~(-5)×L~(2.9964)r=0.9970。初次性成熟年龄为2~3龄,最小性成熟个体体长为190mm,在4~8月均有产卵活动;按von Bertalanffy方程拟合生长参数:L_(∝)=436.21mm,W_(∝)=1715.05g,k=0.2357,t_0=-0.9542,体重生长拐点年龄为3.702龄。 相似文献
28.
29.
枸杞岛海藻场夏、秋季的渔业资源变化 总被引:16,自引:0,他引:16
基于2005年夏、秋两季对枸杞岛海藻场渔业资源的调查数据,对海藻场内外渔业资源的组成、优势种变化、主要资源种类生物学特征以及多样性和相似性进行了研究。结果表明,枸杞岛海藻场内的渔业生物组成的季节变化比藻场外明显,但岩礁性鱼类除外;藻场内优势种夏季多于秋季,而藻场外两季相同,褐菖鲉在夏、秋季的藻场内皆为优势种;各种类生物学特征也存在着明显的季节差异,夏季的性比差别大,秋季接近平衡,平均年龄秋季大于夏季,平均摄食强度夏季高于秋季;多样性值在夏、秋两季海藻场外皆大于海藻场内。藻场内外,夏季的多样性指数都大于秋季;同一季节藻场内外的相似性很低,不同季节,藻场内的相似性同样很低。通过现场调查及生物学实验,夏季海藻场作为幼小鱼类的索饵场所的生态功能得到了确认。 相似文献
30.
The size of harvests temporarily decreases following stock-recovery programs for overexploited resources. The process of stock recovery is quite uncertain, because of unknown life-history parameters, changes in environmental conditions, and human impact. To project future stock recovery, we considered a size-structured matrix model of a stock-recovery program, in which the minimum body size in the first harvest is increased. We applied some common concepts, including yield per recruitment, spawning per recruitment, and reproductive value, to a size-structured matrix model that incorporated economic discounting. The size-structured model predicted the following characteristics in stock-recovery processes: several years must pass for the harvest to increase, and the time-lag between the inception of the management program and the increase in the catch is caused by intergenerational momentum in demography. We also investigated the effects on the recovery process of temporal environmental fluctuations. We applied our model to a stock-recovery program of the corbiculid Seta clam (Corbicula sandai) in Lake Biwa, Japan. 相似文献