全文获取类型
收费全文 | 428篇 |
免费 | 40篇 |
国内免费 | 4篇 |
专业分类
农学 | 3篇 |
基础科学 | 10篇 |
8篇 | |
综合类 | 124篇 |
农作物 | 1篇 |
水产渔业 | 308篇 |
畜牧兽医 | 17篇 |
园艺 | 1篇 |
出版年
2024年 | 5篇 |
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 18篇 |
2018年 | 18篇 |
2017年 | 29篇 |
2016年 | 23篇 |
2015年 | 24篇 |
2014年 | 19篇 |
2013年 | 38篇 |
2012年 | 18篇 |
2011年 | 17篇 |
2010年 | 19篇 |
2009年 | 36篇 |
2008年 | 33篇 |
2007年 | 18篇 |
2006年 | 29篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
排序方式: 共有472条查询结果,搜索用时 31 毫秒
51.
52.
为了研究水产养殖池塘底泥中抗生素残留对氮赋存形态及氮转化功能微生物的影响。选取养殖环境中常见的恩诺沙星(ENR)为目标污染物,设置0、1.0、2.0、5.0 mg/kg 4 个梯度开展模拟试验。结果显示:底泥中NH+4-N和NO-3-N含量随试验开展呈下降趋势,添加ENR后,底泥中NO-2-N含量增加 7.55%~15.30%;底泥氮转化相关基因中,anammox相对丰度最高,占比60.0%~78.4%。厌氧氨氧化是底泥中氮转化的主要途径,底泥中NH+4-N含量与anammox丰度呈极度负相关;底泥中低含量ENR(1.0 mg/kg)会促进nxrA基因的生长或繁殖,但含量超过2.0 mg/kg时对反硝化基因nirK有明显抑制作用。 相似文献
53.
Aquaponics is generally regarded as a sustainable practice, but its environmental burdens were not yet deeply investigated. In this study, Life Cycle Assessment (LCA) was used to assess the environmental impacts of two hypothetical coupled aquaponics systems (CAPS): Raft System (RAFT) and Media-Filled Beds System (MFBS). Rainbow trout (Oncorhynchus mykiss) and lettuce (Lactuca sativa) were considered as cultivated species in both systems. The Simapro© software V.8.0 was used for calculation. The comparison between the two virtual systems indicated the floating technique as the less impacting one. Even though energy consumption appears to be higher in the floating system, LCA results were markedly influenced by the extensive use of inert materials in MFSB. In both systems, contribution analyses underlined that the main environmental impacts are related to infrastructures, electricity and fish feed. The LCA analyses carried out in this study highlights that the choice of less impacting materials, and the optimization of management practices, should be taken as priorities in order to reduce environmental impacts of this activity. 相似文献
54.
The mesophilic anaerobic co-digestion (AcD) performances of waste activated sludge (WAS) and aquaculture sludge (AS) were studied. Mixtures of different compositions (0, 30, 50, 70 and 100 % of AS on the volume basis) were used as AcD substrates and tested via biochemical methane potential assay. The results showed that CH4 production increased with AS/WAS ratio increment, and AS alone used as the substrate showed the maximum CH4 yield, which was 8% higher than that achieved using WAS alone as the substrate. The CH4 yield values were well fitted with the modified Gompertz model. The maximum methane potential (P0) and maximum methane production rate (R0) increased from 66.8 mL CH4/g VSfed to 70.9 mL CH4/g VSfed and from 4.40 mL CH4/g VSfed·d to 5.59 mL CH4/g VSfed·d, respectively, as the AS/WAS ratio increased from 0% to 100 %. In addition, lower levels of free ammonia and non-biodegradable organic matter contributed to the CH4 production increasing with AS/WAS ratio increased. 相似文献
55.
Tuna farming off Port Lincoln, Australia, involves catching wild 2–4-year-old southern bluefin tuna in summer and then fattening for periods of 2–8 months. As fresh product is not available year-round, the feasibility of maintaining tuna for longer periods was trialled, including over a summer season, when temperatures may exceed 24 °C. As the rates of growth and reproduction in ectoparasites of fishes are usually most rapid during warm temperatures, parasite epizootics at this time may adversely affect the health of tuna. We collected epidemiological data on burdens of metazoans on the gills of tuna from the time of stocking in April 2005 through to final harvest in August 2006 (N = 220). We document an epizootic of the copepod Pseudocycnus appendiculatus, characterised by a significant increase in both prevalence and mean intensity in the first winter, followed by a decline in these parameters over the next 12 months. This epizootic pattern appears to be independent of seasonal changes in temperature. For two other species, a second copepod (Euryphorus brachypterus) and a polyopisthocotylean flatworm (Hexostoma thynni), there were no clearly discernible trends in infections. As the high water temperatures over the summer period did not lead to increased infections of any species of gill parasites, we conclude that they do not threaten the feasibility of farming of Thunnus maccoyii. 相似文献
56.
水产养殖专业英语是为了适应社会经济发展而为学生开设的一门考查课,其目的是让学生掌握一种获取更多资料和信息的语言工具.然而,我国至今没有一本适合普通高职院校学生的专业英语教材.根据自身教学实践,本文从教学内容选择及教学手段改革两方面进行了细致深入的阐述,希望对我国水产养殖专业英语或其他学科专业英语的课程教学改革有所启发. 相似文献
57.
本研究由浅海网箱区富营养沉积物经多步富集和筛选获得高效复合生态净化菌群,对浅海养殖区的有机物、氨氮和亚硝酸氮有明显去除效果.研究了不同条件对复合菌液去除养殖水体中氨氮、亚硝酸氮和有机物能力的影响,并确定了最佳净化条件.结果表明,复合菌添加量、葡萄糖添加量,处理时间、温度、pH和盐度对复合菌的去除效果均有影响,实验条件确定为复合菌的添加量为3%、处理时间为4 d、温度为30±2 ℃、pH值为8.1±0.2、葡萄糖添加量为2 g/L和盐度为(30±10) g/L 时,去除效果达到最佳,此时氨氮、亚硝酸氮和溶解有机物的去除率可分别达到79.1%、85.2%和88.7%. 相似文献
58.
José Dias-Neto Gustavo Moraes Ramos Valladão Pedro Henrique De Oliveira Viadanna 《Journal Of Applied Aquaculture》2017,29(1):33-45
During the masculinization of Nile tilapia, Oreochromis niloticus, the effect of a homeopathic complex (containing Chamomilla, Quina, and sulphur) was evaluated based on survival, performance, gills and liver integrity, and parasitism. Group fed with basal diet + 17 alpha-methyltestosterone (control) showed low survival (40.02%), while the group that additionally received homeopathy and the group that received sucrose (vehicle) showed 73.7% and 87.7% survival, respectively. The growth performance of the group that received homeopathic and the control group was significantly higher than that of the group that received only sucrose. Still, fish that received the homeopathic complex showed higher branchial and hepatic integrity as compared to the other groups. The homeopathic complex contributes to a greater survival of fish in addition to maintaining satisfactory growth. Furthermore, homeopathy contributes to the improvement in gill and liver integrity of the Nile tilapia larvae. 相似文献
59.
F Leprieur S Brosse E García-Berthou T Oberdorff J D Olden & C R Townsend 《Fish and Fisheries》2009,10(1):88-97
The introduction of non‐indigenous plants, animals and pathogens is a pressing global environmental challenge. Although not all introduced species become established and the fraction of those that do often have little appreciable effect on their new ecosystems, many others exert significant ecological, evolutionary and economic impacts. Stimulating further debate, Gozlan [Fish and Fisheries (2008) Vol. 9, pp. 106–115] argued that the majority of intentional freshwater fish introductions associated with aquaculture (fish species providing societal benefits) have not been reported as having an ecological impact. We find little to argue with his suggestion that low risk of ecological impact coupled with high market value encourages further introductions. But do we have an adequate understanding of the ecological risks associated with fish introductions to support such decisions? Indeed, resource managers and decision makers require some scientific knowledge to support their management actions; without this information, a precautionary approach is the only sensible course of action. The precautionary approach implies that the lack of scientific certainty is reason enough for postponing intentional introduction of non‐native species to avoid potentially serious or irreversible harm to the environment. Here, we suggest that we actually know very little about ecological impacts associated with fish introductions and that it would be therefore wholly inappropriate to equate a lack of data with a conclusion of ‘no impact’. We discuss four major challenges for enhancing the assessment of risks posed by non‐native freshwater fishes in the face of scientific uncertainty and highlight research opportunities and some alternative approaches for confronting these challenges in the future. 相似文献
60.
流沙湾是中国海水珍珠“南珠”的主产区和广东省重要的贝类养殖区。为评估湾内养殖活动的环境效应,于2015~2016年对流沙湾海区进行了夏(8月)、秋(11月)、冬(2月)、春(5月) 4个季节的浮游植物和海水理化因子调查。共检出浮游植物171种,包括硅藻门43属122种、甲藻门 10属44种、蓝藻门2属2种、金藻门2属2种和裸藻门1属1种。流沙湾内湾浮游植物细胞丰度为(0.05~79.04)×104个/L,夏季>春季>秋季>冬季,且夏季丰度远大于其他三季,内湾和外湾差异不显著。春季须状角毛藻(Chaetoceros crinitus)、红海束毛藻(Trichodesmium erythraeum)和明壁圆筛藻(Coscinodiscus debilis)为主要优势种,夏季优势种主要为中肋骨条藻(Skeletonema costatum),秋季优势种主要为拟弯角毛藻(Chaetoceros pseudocurvisetus)、奇异棍形藻(Bacillaria paradoxa)、洛氏角毛藻(Chaetoceros lorenzianus),冬季主要优势种为威氏圆筛藻(Coscinodisus wailesii)、柔弱根管藻(Rhizosolenia delicatula)、岛脆杆藻(Fragilaria islandica)。其中,奇异棍形藻为春、秋、冬季的优势种,红海束毛藻为春、夏、秋季的优势种。冗余分析表明,流沙湾浮游植物优势种在春季与水温和氨氮密切相关,夏季受透明度显著影响,而在秋、冬季受亚硝酸氮含量影响显著。流沙湾不同养殖区的浮游植物多态性和丰度有明显季节差异。与2012年相比,流沙湾外湾的养殖覆盖率提高了近50%,内湾的珍珠贝养殖减少了近90%,养殖品种、规模和分布格局都发生了明显变化,目前流沙湾的浮游植物群落特征正是对其变化的一种响应。夏季鱼类网箱养殖提高了水域营养盐水平并降低了浮游植物多样性。大规模的扇贝养殖则导致了扇贝养殖区浮游植物丰度的降低。 相似文献