全文获取类型
收费全文 | 3248篇 |
免费 | 225篇 |
国内免费 | 1篇 |
专业分类
林业 | 259篇 |
农学 | 161篇 |
基础科学 | 17篇 |
789篇 | |
综合类 | 189篇 |
农作物 | 205篇 |
水产渔业 | 456篇 |
畜牧兽医 | 1107篇 |
园艺 | 75篇 |
植物保护 | 216篇 |
出版年
2024年 | 3篇 |
2023年 | 42篇 |
2022年 | 73篇 |
2021年 | 142篇 |
2020年 | 136篇 |
2019年 | 160篇 |
2018年 | 155篇 |
2017年 | 144篇 |
2016年 | 131篇 |
2015年 | 97篇 |
2014年 | 158篇 |
2013年 | 189篇 |
2012年 | 244篇 |
2011年 | 273篇 |
2010年 | 146篇 |
2009年 | 160篇 |
2008年 | 192篇 |
2007年 | 174篇 |
2006年 | 166篇 |
2005年 | 148篇 |
2004年 | 127篇 |
2003年 | 141篇 |
2002年 | 97篇 |
2001年 | 23篇 |
2000年 | 21篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 11篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 5篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1986年 | 2篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1971年 | 3篇 |
1968年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有3474条查询结果,搜索用时 537 毫秒
861.
Carlos Andre Amaringo Cortegano Aline Marculino de Alcntara Allana Feitoza da Silva Cludia Maiza Fernandes Epifnio Sunique Po Cordeiro Bentes Vanessa Jorge dos Santos Jesuí Vergílio Visentainer Ligia Uribe Gonalves 《Aquaculture Research》2019,50(4):1291-1299
The need for a sustainable aquaculture is increasing the use of plant ingredients in replacement to fishmeal and fish oil in diets for tambaqui Colossoma macropomum, which is leading to not detectable levels of docosahexaenoic acid (DHA) in its flesh. We evaluated the effect of a finishing plant diet supplemented with 5% of microalgae meal from Schizochytrium sp. (MD) on tambaqui growth, on proximal composition and fatty acid content of its flesh, comparing it to a non‐supplemented diet. One hundred and sixty‐two fish (489.67 g) were distributed into six tanks (2,000 L) and fed the experimental diets for a 90‐day period. Three fish per tank were euthanized for analyses every 15 days. The MD did not affect the growth and proximal composition of fish flesh. The MD increased the DHA content (from 14.81 to 38.60 mg/g of lipids) and the n‐3:n‐6 ratio (from 0.16 to 0.51) in the flesh of fish, beginning on the 15th day and reaching the highest DHA content on the 71st day (39.81 mg/g of lipids). We recommend C. macropomum to be fed with a finishing diet supplemented with microalgae meal for 71 days before slaughter to improve the DHA content and n‐3:n‐6 ratio in the flesh. 相似文献
862.
Leonardo Lara de Carvalho Eduardo Godoy Aires de Souza Roberto Campos Villaça 《Aquaculture Research》2017,48(2):481-493
The seaweed Kappaphycus alvarezii (Doty) Doty ex P. C. Silva, a red algal species, is the main global source of Kappa carrageenan. The introduction of such exotic species in regions outside their original locale can change the community structure of the areas into which they are introduced. The possible influence of seaweed farming on the rocky reef fish assemblage was assessed in Paraty, Brazil. The reef fish assemblage in the seaweed farming area was compared before and after the commencement of farming with two undisturbed control areas. Among the ten species ranked as the most frequently occurring in each area, eight were the same. The fish community structure close to the seaweed farming area did not change from that of the control areas, over the months of the study. Neither the fish diversity and richness indices, nor the total average abundance among areas was significantly altered. The average abundance of the different trophic groups varied over time in both the farm and control areas, revealing similar patterns. These results suggest that K. alvarezii can be cultivated up to at least 50 m from a rocky coast without altering the fish community structure of the surrounding waters. 相似文献
863.
Digestive enzymatic activity and growth performance on tropical gar (Atractosteus tropicus) larvae fed Artemia nauplii (LF), frozen adult Artemia (AB), an artificial diet (AF) with 46% protein and 16% lipids and a starvation group (SG) from first feeding (5?days after hatching-5 DAH) to 34 DAH were studied. All larvae under starvation (SG) died at 15 DAH. By the end of the experimental period, morphological variables (total length, wet weight and specific growth rate) were significant in larvae fed AF compared to LF and AB. All enzymes studied in the experiment were present since the start of exogenous feeding (including pepsin) and the enzymatic activity varied with the diets. Low levels of enzymatic activity were observed until the 29 DAH; however, after this moment, there was a significant increase (eightfold), particularly for the AF treatment. In vitro protein digestibility tests performed with enzymatic extracts showed that artificial diets with 52% protein and 14% lipids were better digested by larvae before 30 DAH, while diets with 45% protein and 11% lipids were better digested after this age. Taking into account the better growth performance, higher enzymatic activity and better protein digestibility obtained, artificial diets can be used since the start of exogenous feeding on tropical gar larvae, as in other lepisosteids. 相似文献
864.
Carrying capacity and potential environmental impact of fish farming in the cascade reservoirs of the Paranapanema River,Brazil
下载免费PDF全文
![点击此处可从《Aquaculture Research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Roberto Montanhini Neto Helder Rafael Nocko Antonio Ostrensky 《Aquaculture Research》2017,48(7):3433-3449
The objective of this study was to simulate changes in water quality standards caused by the installation of aquaculture parks for caged fish farming in the eight large artificial reservoirs in the Paranapanema River according to the different scenarios of technical and legal limitations: (i) occupancy of 1% of the total surface of the reservoirs and (ii) occupancy according to the environmental carrying capacity. For water quality modelling, these two scenarios were simulated to determine the trophic state index (TSI) of each reservoir. Based on the total area of all reservoirs in the first scenario, the fish farm facilities would occupy 18.3 km2 and have an annual fish production of an estimated 513 thousand MT. However, because of limitations in the carrying capacity, the annual production in the second scenario would be 98 thousand MT and the fish farm facilities would occupy 3.5 km2. Simulating the TSI for the first scenario, approximately 75% of the total area of all reservoirs was estimated to change from oligo or mesotrophic conditions to eutrophic, supereutrophic and hypereutrophic conditions, and four reservoirs may become completely eutrophic (Canoas 2, Canoas 1, Taquaruçu and Rosana). For the second scenario, however, eutrophic areas accounted for less than 30% of the total, although the Taquaruçu and Rosana reservoirs were still at risk of total eutrophication. These results indicate as well‐intentioned legislation can have unintended environmental consequences in dynamic social–ecological aquaculture systems as in the case of large reservoirs in the Paranapanema River. 相似文献
865.
José Carlos Hernández Sabrina Clemente Carlos Sangil Alberto Brito 《水产资源保护:海洋与淡水生态系统》2008,18(7):1091-1108
- 1. The aim was to determine the status of subtidal rocky benthic assemblages in three marine protected areas (MPAs) of the Canary Islands: (1) La Graciosa; (2) Mar de Las Calmas; (3) La Palma. Sea urchin (Diadema aff. antillarum) populations and non‐crustose macroalgal cover were surveyed, and used as an indicator of conservation status in the three MPAs as well as in a highly fished area (HFA‐Tenerife Island).
- 2. Comparing characteristics between each MPA and the HFA, and considering issues of management and design, it was concluded that the three MPAs each have a different conservation status. ‘Mar de Las Calmas’ marine reserve was found to have the most desirable conservation status, followed by ‘La Palma’ marine reserve based on sea urchin populations and non‐crustose macroalgae assemblages.
- 3. Conversely, ‘La Graciosa’ had the highest density of D. aff. antillarum and the lowest cover of non‐crustose macroalgae out of the three MPAs. Values were comparable to those at the HFA, which shows ‘La Graciosa’ to have the undesired conservation status.
- 4. Different spatial distribution patterns of non‐crustose macroalgal as well as different algal composition cover were observed between the three MPAs and the HFA. These differences were principally attributed to the intensity of grazing activity of the key herbivore D. aff. antillarum. It is suggested that the different study areas correspond to different phase shifts that imply differing resilience of systems that should be taken into a count in future conservation strategies.
866.
Julia Pinedo-Gil Ana Tomás-Vidal Daniel Rico Brijesh Tiwari Carlos Álvarez García Miguel Jover-Cerdá 《Journal Of Aquatic Food Product Technology》2019,28(5):495-504
Barley concentrations ranging from 0% to 32% were incorporated into rainbow trout (Oncorhynchus mykiss) diets. The effect of barley concentration on lipid peroxidation and antioxidant activity of fish fillets were analyzed. Results showed that the inclusion of barley in rainbow trout diets had an inhibitory effect on lipid oxidation, probably associated with certain bioactive compounds in barley that could interact with scavenging and reducing metabolites involved in lipid oxidation. Concentrations up to 8% of barley produced fish fillets with high antioxidant activity and higher levels of alpha-tocopherol. 相似文献
867.
Gonzalo Rodríguez Rodríguez Roberto Bande Sebastián Villasante 《Aquaculture Economics & Management (Blackwell Science)》2013,17(4):380-397
Interactions between fisheries and aquaculture have become a major issue that is still insufficiently studied. Therefore, the objective of this article is to test whether the cultured and wild gilthead sea bream in the Spanish seafood markets are integrated. By using the Johansen methodology, cointegration of the price series of farmed and wild gilthead sea bream was tested. In contrast to previous studies, our econometric results show that wild and the farmed gilthead sea bream form two heterogeneous products in the Spanish market. These new results question the generalization currently accepted by the scientific literature that farmed and wild fish are substitutes when they belong to the same species. The binomial product-market, along with some specific features of the Spanish market, such as the negative perceptions of aquaculture by some significant groups of consumers, appeared to have a great explanatory power for justifying these different results. 相似文献
868.
This paper examined the toxins naturally produced by marine dinoflagellates and their effects on increases in β-amyloid plaques along with tau protein hyperphosphorylation, both major drivers of Alzheimer’s disease (AD). This approach is in line with the demand for certain natural compounds, namely those produced by marine invertebrates that have the potential to be used in the treatment of AD. Current advances in AD treatment are discussed as well as the main factors that potentially affect the puzzling global AD pattern. This study focused on yessotoxins (YTXs), gymnodimine (GYM), spirolides (SPXs), and gambierol, all toxins that have been shown to reduce β-amyloid plaques and tau hyperphosphorylation, thus preventing the neuronal or synaptic dysfunction that ultimately causes the cell death associated with AD (or other neurodegenerative diseases). Another group of toxins described, okadaic acid (OA) and its derivatives, inhibit protein phosphatase activity, which facilitates the presence of phosphorylated tau proteins. A few studies have used OA to trigger AD in zebrafish, providing an opportunity to test in vivo the effectiveness of new drugs in treating or attenuating AD. Constraints on the production of marine toxins for use in these tests have been considered. Different lines of research are anticipated regarding the action of the two groups of toxins. 相似文献
869.
Rosario Martínez Ronald Santos Maite Mascaró Lenin Canseco Claudia Caamal‐Monsreal Carlos Rosas 《Aquaculture Research》2012,43(8):1119-1126
In the present study, digestive dynamics, measured through the changes in the in situ pH along the digestive tract, was evaluated along with the glycogen concentration in the digestive gland (DG) and the proteolytic enzyme activity of the gastric juice (GJ) (both acid and alkaline proteases) to obtain useful information that will allow for the understanding of the DG's function and the role that it plays as an extracellular digestive enzyme source and for energy storage, providing new information on the digestive physiology of Octopus maya. The results showed that pH along the digestive tract changed according to the postprandial time following the food transit. At the beginning, the pH on crop (St) was 5, changing to 6 when the food arrived. Similar changes were observed on the caecum (Ce) and DG. Glycogen from DG is used as a source of energy during digestion and recovered 8 h after feeding. Maximum activities of digestive gland GJ enzymes were observed 6 h after feeding, indicating that chyme enzymes are still active when they arrive at the DG's lumen. The presence of food in the digestive tract modifies the pH, which, in combination with GJ, favours the activity of the released enzymes of O. maya. 相似文献
870.
Mellon JE Zelaya CA Dowd MK Beltz SB Klich MA 《Journal of agricultural and food chemistry》2012,60(10):2740-2745
Racemic gossypol and its related derivatives gossypolone and apogossypolone demonstrated significant growth inhibition against a diverse collection of filamentous fungi that included Aspergillus flavus, Aspergillus parasiticus, Aspergillus alliaceus, Aspergillus fumigatus, Fusarium graminearum, Fusarium moniliforme, Penicillium chrysogenum, Penicillium corylophilum, and Stachybotrys atra. The compounds were tested in a Czapek agar medium at a concentration of 100 μg/mL. Racemic gossypol and apogossypolone inhibited growth by up to 95%, whereas gossypolone effected 100% growth inhibition in all fungal isolates tested except A. flavus. Growth inhibition was variable during the observed time period for all tested fungi capable of growth in these treatment conditions. Gossypolone demonstrated significant aflatoxin biosynthesis inhibition in A. flavus AF13 (B(1), 76% inhibition). Apogossypolone was the most potent aflatoxin inhibitor, showing greater than 90% inhibition against A. flavus and greater than 65% inhibition against A. parasiticus (B(1), 67%; G(1), 68%). Gossypol was an ineffectual inhibitor of aflatoxin biosynthesis in both A. flavus and A. parasiticus. Both gossypol and apogossypolone demonstrated significant inhibition of ochratoxin A production (47%; 91%, respectively) in cultures of A. alliaceus. 相似文献