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   239篇
  免费   36篇
  国内免费   15篇
林业   1篇
农学   2篇
基础科学   2篇
  4篇
综合类   33篇
水产渔业   242篇
畜牧兽医   6篇
  2023年   1篇
  2022年   3篇
  2021年   3篇
  2020年   8篇
  2019年   4篇
  2018年   4篇
  2017年   12篇
  2016年   9篇
  2015年   6篇
  2014年   7篇
  2013年   29篇
  2012年   14篇
  2011年   10篇
  2010年   12篇
  2009年   9篇
  2008年   11篇
  2007年   11篇
  2006年   13篇
  2005年   13篇
  2004年   6篇
  2003年   13篇
  2002年   10篇
  2001年   4篇
  2000年   12篇
  1999年   5篇
  1998年   6篇
  1997年   12篇
  1996年   8篇
  1995年   9篇
  1994年   9篇
  1993年   4篇
  1992年   4篇
  1991年   1篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
排序方式: 共有290条查询结果,搜索用时 15 毫秒
1.
The objective of this study was to evaluate different hatchery systems used for the larviculture of the Macrobrachium carcinus based on survival, larval development and production of post-larvae. The experimental culture was carried out in three phases designated as Phase I (Zoea VI to VIII – ZVI – VIII), Phase II (Zoea VIII to X – ZVIII – X), and Phase III (Zoea X to PL – ZX – PL), with densities of 30, 27.5 and 25 larvae / L, respectively. The M. carcinus larvae (ZVI) were reared in four culture systems, two being open (Greenwater – GW and Clearwater – CW) and two being closed (Biofloc – BFT and Bio-filter – RAS), distributed in twelve 10 L plastic containers, filled with 20 ppt brackish water, equipped with constant aeration, and water circulated by air lift and heated with thermostat (∼30 °C). The GW treatment was maintained with Chlorophyceae algae in the density of 3–5 × 105 cells/mL. In the CW, the water was previously filtered through a 5 μm mesh screen, sterilized with 10 ppm active chlorine and, dechlorinated with vitamin C and subjected to aeration for 24 h. The BFT received water rich in bioflocs that was matured prior to the experiment and used molasses as a source of organic carbon. In the RAS, the culture water circulated through an external “Dry-Wet” biological filter. The feeding was carried out ad libitum four times daily, alternating a wet diet formula with a commercial diet, which was supplemented with newly hatched Artemia nauplii at a rate of 40–50 per larvae/day. Temperature, dissolved oxygen and pH were monitored daily and the salinity two times per week. Total ammonia, nitrite, nitrate, orthophosphate, alkalinity, total suspended solids, chlorophyll-a, COD and BOD were also analyzed. The best water quality (P < 0.05) was obtained in the RAS, with 0.49 (±0.38), 0.23 (±0.22), and 9.0 (±1.5) mg/L of TAN, NO2-N and NO3-N, respectively. In the GW, the nitrogen species showed high fluctuations and higher concentrations at 2.32 (±1.68), 3.53 (±3.53) and 18.2 (±12.9) mg / L of TAN, NO2-N and NO3-N, respectively. Considering the three phases (ZVI – PL), the overall survival was 0.03, 1.97, 2.23 and 17.32 % for the BFT, CW, GW and RAS, respectively. When considering the phases separately, the survival in Phase I (ZVI – VIII) was highest in the GW system at 58.7 % while the RAS was the highest in Phases II (ZVIII – X) and III (ZX – PL) at 70.6 % and 60.3 %, respectively. The BFT showed 8.4 (±3.5) PL/L, which was higher (P < 0.05) than that obtained in the RAS (2.8 ± 1.2 PL/L) and the GW (1.3 ± 1.1 PL/L) and similar to that obtained in the CW (5.6 ± 2.0 PL/L). Thus, the larviculture for the M. carcinus may be optimized by adopting a multiphase management strategy, which the intermediate larval stages (ZVI – IX) are reared in the GW system and the final stages (ZX – PL) are reared in the BFT system.  相似文献   
2.
We determined the effect of four concentrations of dietary crude protein, 30.7, 37.2, 41.8 and 46.8% on growth rate, survival and body composition of the juvenile cauque river prawn (Macrobrachium americanum). The prawns were hatched in the laboratory from the spawn of one wild ovigerous female. Prawns consuming 37.2% crude protein reached a final weight of 0.58 g (feed conversion ratio of 2.15), which was significantly better than the other treatments. Survival was 100% in all treatments. Protein content in the diets had no significant effect on whole body proximate composition and amino acid profile. Juveniles consuming the 37.2% crude protein diet grew faster than those fed the other diets. Specific growth rate was adjusted to the two‐slope broken‐line regression analysis model to estimate the optimal protein requirement. In conclusion, these results demonstrated that the 37.2% protein level diet is optimal for juvenile cauque river prawn M. americanum in the experimental conditions of this study.  相似文献   
3.
The aim of this study was to compare two rearing systems for freshwater prawn Macrobrachium rosenbergii: one with use of a recirculating aquaculture system with biofilters (RAS) and another with use of microbial flocs (F). Thirty postlarvae of freshwater prawn with an initial average weight of 0.13 ± 0.05 g were randomly stocked in six experimental units with 0.20 m² and volume of 50 L. The experiment lasted thirty days. Dissolved oxygen, temperature and pH were monitored daily; ammonia concentration was determined three times per week; nitrite concentration, alkalinity and hardness were measured weekly. For the formation of microbial floc, molasses was used to keep the ammonia concentrations within safe levels for prawn farming. The variables of water quality remained within the suitable range for the production of the species, except for ammonia concentrations at the F treatment, which exceeded the safe levels. At the end of the experiment, the following parameters were evaluated: survival, specific growth rate, weight gain and feed conversion rate. Differences were found only in feed conversion rate with better values on RAS treatment. The microorganisms present in the RAS and F treatment were also evaluated. The densities of rotifers, amoebas and total bacteria were higher at the F treatment although the same organisms were found at the RAS treatment. The results of this study showed the possibility of rearing M. rosenbergii in biofloc system technology.  相似文献   
4.
Estuaries act as nurseries for many penaeid prawns, but these habitats are highly susceptible to salinity decline through flooding. The rate of salinity decline and duration of exposure to non‐optimal salinity may affect survival and subsequent recruitment of prawns to the fishery. This study aimed to determine the effect of salinity fluctuations observed in local estuaries during flood events using a novel dilution approach. Mortality of juvenile Melicertus plebejus (Hess) was assessed after 24 hr exposure to 24 rates of salinity decline ranging from 0.01% to 20% per hr. After the salinity decline, prawns were held at the final salinities for five days before again assessing mortality as well as aerobic metabolic rate and prawn water content. Salinity decline from 36 to ~0.8 led to 50% mortality, but continued exposure to low salinity for five days increased mortality at this salinity to 99% and shifted the 50% mortality point to salinity ~5. Aerobic metabolic rate and water content data suggested the cause of mortality due to exposure to salinities < 5 was osmoregulatory failure. Rapid salinity declines over 24 hr and sustained low salinity due to flooding could compromise the survival of juvenile prawns, potentially reducing recruitment to the fishery.  相似文献   
5.
In this study, the phenotypic and pathogenic properties in freshwater host were characterized in 14 strains of halophilic Vibrio harveyi isolated from infected marine black tiger shrimp, Penaeus monodon. The lysogenic phenotype was assayed via prophage excision and mitomycin C induction. The bacteria were grouped into two types, corresponding to lysogenic and non‐lysogenic strains. The pathogenicity was determined via direct injection of bacterial cultures into post‐larval juvenile giant freshwater prawns, Macrobrachium rosenbergii De Man. All of the infected prawns showed similar symptoms and inflamed hepatopancreas. The V. harveyi isolates derived from the first‐injected infected prawns were re‐isolated and re‐injected into healthy giant freshwater prawns, in which they retained similar infectivity. Both lysogenic and non‐lysogenic Vibrio spp. showed identical virulence associated with 100% mortality within one day post‐injection. TEM micrographs showed hepatopancreatic nuclear deformation and lipid breakdown caused by lysogenic γ‐hemolytic VL19 and non‐lysogenic β‐hemolytic V33. However, the V33 strain was associated with severely disrupted mitochondria. None of the V. harveyi strains was able to produce a biofilm. Together, our findings indicate that the lysogenic and non‐lysogenic halophilic V. harveyi isolated from marine shrimps may use different virulence factors that are responsible for their pathogenicity in freshwater prawns.  相似文献   
6.
The production performances of giant freshwater prawn Macrobrachium rosenbergii and Nile tilapia Oreochromis niloticus in C/N‐controlled periphyton‐based polyculture systems were evaluated in triplicate. Three different management practices were compared: the traditional practice without addition of periphyton substrates and carbohydrate (Control), addition of maize flour to maintain a carbon: nitrogen rate of 20:1 (treatment CN) and addition of both maize flour and periphyton substrates (treatment CN+P). This experiment used a pre‐optimized stocking density of tilapia and freshwater prawn by Asaduzzaman et al. Aquaculture [286 (2009) 72]. All ponds were stocked with prawn (3 m2) and monosex Nile tilapia (1 m?2). Bamboo side shoots were posted vertically into the pond bottoms as periphyton substrate covering an additional area of 171 m2 for periphyton development. A locally formulated and prepared feed containing 17% crude protein with C/N ratio close to 15:1 was applied twice daily in all ponds considering the body weight of freshwater prawn only. Water quality parameters, except total alkalinity did not vary significantly (> 0.05) among treatments. Both, organic matter and total heterotrophic bacterial loads (THB) in the sediment were significantly (P < 0.05) higher in treatment CN+P followed by treatment CN and control. Periphyton biomass in terms of dry matter and chlorophyll a values constantly decreased during the culture period. Substrates contributed 66% and 102% higher net yield of freshwater prawn than CN and control treatment respectively.  相似文献   
7.
采用微波消解-火焰原子吸收光谱法(flame atomic absorption spectrometry,FAAS)测定虾肉中钙(ca)元素的质量分数,对微波消解前处理的条件进行了研究。试验结果显示,最佳的微波消解体系为取样量0.500g,以硝酸(HNO,)作为消解溶剂,用量5.0mL,最适微波消解程序为多步消解程序D,包含3个步骤:1)功率400W,比例100%,升温5min,消解温度120℃,保持5min;2)功率800W,比例100%,升温5min,消解温度150℃,保持10min;3)功率800W,比例100%,升温10min,消解温度180℃,保持10min。样品消解液在常温或冷藏条件下保存48h之内的稳定性良好。经微波消解前处理后虾肉样品中”(ca)的相对标准偏差(relative standard deviation,RSD)为5.284%,加标回收率为91%-98%。微波消解-FAAS测定虾肉中的w(Ca)具有样品处理时间短、试剂用量少、结果准确和安全性高等优点。  相似文献   
8.
The giant freshwater prawn Macrobrachium rosenbergii was first introduced into mainland China by the Chinese Academy of Agricultural Sciences from Japan in 1976. It was cultured at the Guangdong Province Fishery Institute (now as Pearl River Fishery Institute, Chinese Academy of Fishery Sciences). Following these early efforts, giant freshwater prawn culture has gradually spread to northern and inland areas. At this time (2011), China has become the largest producer of giant freshwater prawn in the world. Due to a preference of cooking with fresh aquatic products, Chinese retail markets have developed which have special live‐holding counters. From small rural shops to urban supermarkets and specialty restaurants, live seafoods are commonly available whereby customers pick out the products they wish to purchase and consume. Giant freshwater prawns are produced in over 35 countries throughout the world. They are usually sold either fresh, on‐ice, or frozen. What makes the Chinese prawn industry unique is its focus on a live transportation and marketing model. As a result, numerous innovative live‐transport technologies have been developed which have been key to the success of this expanding domestic industry. In this article, we would like to give a general overview of the giant freshwater prawn industry, its status in China, and the special role live‐transportation has for expanding production of giant freshwater prawns.  相似文献   
9.
Giant river prawn (Macrobrachium rosenbergii) farming plays an important role in the economy of Bangladesh. Presently, it is cultured in around 50 000 ha area with total annual production of 23 240 t. Traditional extensive prawn farming has been expanding over the last three decades through the introduction and adoption of improved culture systems, such as culture of prawn‐carps, prawn‐shrimp‐fish and prawn‐fish‐rice as concurrent and rotational systems. Efforts for the development of improved techniques on broodstock management, seed production and rearing and grow‐out of prawn have been made over the last decade. The outcomes are low‐cost feed for broodstock, production of post‐larvae in net cages (hapa), all‐male prawn culture, periphyton based prawn‐tilapia culture, C/N based prawn culture, organic prawn farming, prawn‐mola culture and prawn‐carp‐mola polyculture. Despite the development of culture technologies, a number of challenges for sustainable development of prawn farming need to be overcome to realize the potentials of this promising sector. Good aquaculture practises at all levels and application of measures for quality control and food safety would ensure sustainable development of prawn farming in Bangladesh.  相似文献   
10.
Chemical compositions and thermal properties of cultured freshwater prawn meat (FPM) were studied. FPM contained 83.2% protein (dry basis), 62.7% of which was myofibrillar protein. Pepsin-soluble collagen (PSC) and insoluble collagen (ISC) contents were 0.63 and 0.32%, respectively. Both collagens were similar to type V collagen from porcine placenta. Glutamic acid/glutamine, arginine, aspartic acid/?asparagine, and lysine were abundant amino acids in FPM. Glycine, proline, hydroxyproline, and aspartic acid/?asparagine were predominant in both collagens. FPM exhibited thermal transition temperatures (Tmax) of 48.3 and 64.7°C, whereas Tmax of PSC and ISC were 43.0 and 46.0°C, respectively. Textural changes in FPM during post-mortem storage on ice are plausibly dependent upon its compositional and thermal properties.  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