全文获取类型
收费全文 | 619篇 |
免费 | 37篇 |
专业分类
林业 | 56篇 |
农学 | 32篇 |
基础科学 | 9篇 |
132篇 | |
综合类 | 15篇 |
农作物 | 39篇 |
水产渔业 | 89篇 |
畜牧兽医 | 224篇 |
园艺 | 11篇 |
植物保护 | 49篇 |
出版年
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 33篇 |
2020年 | 42篇 |
2019年 | 44篇 |
2018年 | 30篇 |
2017年 | 39篇 |
2016年 | 39篇 |
2015年 | 16篇 |
2014年 | 33篇 |
2013年 | 41篇 |
2012年 | 51篇 |
2011年 | 64篇 |
2010年 | 26篇 |
2009年 | 17篇 |
2008年 | 21篇 |
2007年 | 26篇 |
2006年 | 19篇 |
2005年 | 19篇 |
2004年 | 17篇 |
2003年 | 7篇 |
2002年 | 15篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1980年 | 1篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有656条查询结果,搜索用时 250 毫秒
651.
Juliano Uczay Eduardo Kelm Battisti Rafael Lazzari Marcos Luiz Pessatti Thamara Luisa Staudt Schneider Luiza Beatriz Hermes Nilce Coelho Peixoto Thiago El Hadi Perez Fabregat 《Aquaculture Research》2019,50(5):1438-1447
One of the current challenges of global fish farming is developing plant‐based proteins as a feasible substitute for fishmeal in the formulation of aquafeeds. Substitution levels of fishmeal with hydrolyzed soybean meal (HSM) in diets for silver catfish (Rhamdia quelen) were evaluated for growth, protein metabolism and antioxidant activity. The experiment was carried out in a recirculation system of 20 tanks of 250 L. A total of 300 silver catfish juveniles were used to compose five treatments and four replicates per treatment. Levels of soybean hydrolysate (0%, 5%, 10%, 15% and 20%) were tested in diets (39% protein and 3,500 Kcal) for 60 days. Silver catfish growth was higher at all inclusion levels of HSM when compared to the control diet. No change was shown for body protein deposition. The production of nitrogenous compounds in the liver and muscle was also unaffected by any of the diets. The diet containing 20% HSM promoted an increase in the amounts of non‐protein thiols in the gills and brain. The HSM substitution levels of up to 20% of fishmeal in the diet increases growth and contributes to silver catfish antioxidant activity. 相似文献
652.
Leonardo Luiz Calado Luiz Antônio Carlos Bertollo Gideão Wagner Werneck Felix da Costa Wagner Franco Molina 《Aquaculture Research》2013,44(5):829-835
Fish of the family Gerreidae, mainly species of the genera Diapterus and Eugerres, have high potential for cultivation, because of their saline tolerance. A detailed cytogenetic analysis of Diapterus auratus, Diapterus rhombeus and Eugerres brasilianus was conducted using conventional staining, C‐banding, Ag‐NOR, AT/GC‐specific fluorochrome staining and mapping of ribosomal sequences with 5S and 18S rDNA probes. All the species exhibited symmetrical karyotype, 2n = 48 acrocentric chromosomes. Ag‐NORs and 18S rDNA are present in the interstitial position on pair 1 (genus Diapterus) and pair 6 in Eugerres brasilianus. The 5S rDNA sites, located in the interstitial position (pair 11), are conserved in the three species. Heterochromatic regions are similar in the Diapterus species, showing a pattern of reduced and centromeric bands, differing from E. brasilianus, where, in addition to these, more prominent interstitial bands were observed. GC‐rich regions are located at ribosomal sites. Karyotypic comparison between Diapterus and Eugerres reveals similarity in chromosomal macrostructure, differing in C‐positive heterochromatin distribution and position of 18S sites, indicating the occurrence of structural microrearrangements. Although complementary analyses are needed, the similarities observed for these and other species suggest the possibility of breaking postzygotic barriers and their potential use, through induced interspecific or intergeneric hybridizations. 相似文献
653.
Wilson M Furuya Luiz E Pezzato Margarida M Barros A C Pezzato Valéria R B Furuya & Edma C Miranda 《Aquaculture Research》2004,35(12):1110-1116
This study was undertaken in a closed system with Nile tilapia (Oreochromis niloticus) to examine the effects of total replacement of fish meal (FM) by soybean meal. Nile tilapia fingerlings with an average weight of 5.34±0.08 g were hand‐fed one of the five isoenergetic (≈13.5 MJ digestible energy kg?1) and isoproteic (≈31% of digestible protein) experimental diets to satiation, six times a day during 85 days in eight replicate fibreglass tanks (six fish per tank). The control diet containing FM was substituted by soybean meal, with and without essential amino acids (lysine, methionine and threonine) or dicalcium phosphate supplementation. The supplemental amino acids were added at levels to simulate the reference amino acid profile of Nile tilapia carcass protein, based on the ideal protein concept. The results showed that soybean meal diet supplemented only with dicalcium phosphate was inferior to the control diet with FM and soybean meal diets supplemented with dicalcium phosphate and essential amino acids. Multiple essential amino acids and dicalcium phosphate incorporation in soybean meal diets was associated with performance, whole‐body composition and carcass yield equal to that of the fish fed with the control diet containing FM. These data suggest that a diet with all plant protein source, supplemented with essential amino acids, based on tissue amino acid profile, can totally replace FM in a diet for Nile tilapia, without adverse effects on the growth performance, carcass yield and composition. 相似文献
654.
Auren Benk Soso Leonardo José Gil Barcellos Maria José Ranzani‐Paiva Luiz Carlos Kreutz Rosmari Mezzalira Quevedo Marina Lima Leonardo Bolognesida Silva Filipe Ritter Alexandra Calliari Bedin Jovani Antônio Finco 《Journal of the World Aquaculture Society》2008,39(6):835-841
Abstract.— A stressful environment induces cortisol that might affect fish breeding and reproduction. In the present work, which aimed to mimic aquacultural conditions of the jundia (Rhamdia quelen) hatcheries in southern South America, females were submitted to normal or stressful handling and the effects of cortisol on serum levels of 17β‐estradiol (E2) and testosterone (T) were determined. In addition, the effect of stress on reproductive parameters such as eggs and swim‐up fry production was also measured. Eight females from a group submitted to stressful handling (SH) conditions and eight females from a group with normal handling (NH) conditions were captured for blood sampling at D 0 and at D 1, 10, 20, 30, and 40 of the experiment. A typical cortisol response was observed in the SH females group in that they presented higher cortisol level in contrast to the NH female group, in all days sampled, except at D 0. In the 10th and 20th d, the E2 levels were lower in SH females, but cortisol levels were higher, suggesting an effect of cortisol on E2 production and/or release. Stressful handling appeared to affect both the number and the quality of the gametes because a lower number of oocytes was stripped from SH females, and from SH fertilized eggs, a lower number of viable swim‐up fry was obtained to be transferred to earthen larviculture ponds. Taken together, the results indicated that stressful handling of broodstock impairs R. quelen reproduction. 相似文献
655.
de Souza Farias Jos Williano Orella Jonathan Said Tejeda dos Santos Batista Edgar Cordeiro Rafael Cruz Passos Adriana Rodrigues Silva Luiz Cludio Costa 《Genetic Resources and Crop Evolution》2022,69(3):1365-1374
Genetic Resources and Crop Evolution - Physalis angulata L. is an American species with edible fruits that stands out for having high nutritional and pharmaceutical value. The species is found in... 相似文献
656.
Igor Christo Miyahira Maria Cristina Dreher Mansur Luiz Eduardo Macedo de Lacerda Isabela Cristina Brito Gonçalves Glauco Gil Sant'Anna Sonia Barbosa dos Santos 《水产资源保护:海洋与淡水生态系统》2023,33(1):102-114
- Bivalves are important components of freshwater ecosystems; however, they are also one of the most threatened animal groups, especially members of the order Unionida. The main threats to freshwater bivalves are habitat modification and invasive species. Protected areas are a common way to minimize impacts and preserve native species, but they are rarely designated with a focus on freshwater invertebrates.
- The main goal of this article was to describe the distribution of freshwater bivalves in the state of Rio de Janeiro, and the relationship between these species and bioclimatic areas, land use and protected areas.
- Five native and two invasive bivalve species have been reported in Rio de Janeiro. They occur mainly in bioclimatic areas related to the Paraíba do Sul River and Campista Lowlands. The few records of bivalves inside protected areas are in areas of sustainable use that offer a lower level of protection, and frequently in sympatry with invasive bivalves.
- Thus, the established protected areas in Rio de Janeiro are not adequately effective for freshwater bivalve conservation, and some species remain under threat even within them. Freshwater bivalves thus remain largely unprotected in the state.
- The development of new protected areas and management plans should consider other faunal groups that are usually ignored, such as freshwater bivalves, to achieve more inclusive and effective protection.