全文获取类型
收费全文 | 491篇 |
免费 | 50篇 |
专业分类
林业 | 40篇 |
农学 | 20篇 |
基础科学 | 2篇 |
93篇 | |
综合类 | 35篇 |
农作物 | 25篇 |
水产渔业 | 72篇 |
畜牧兽医 | 207篇 |
园艺 | 12篇 |
植物保护 | 35篇 |
出版年
2023年 | 13篇 |
2022年 | 16篇 |
2021年 | 34篇 |
2020年 | 27篇 |
2019年 | 37篇 |
2018年 | 28篇 |
2017年 | 27篇 |
2016年 | 34篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 21篇 |
2012年 | 34篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 23篇 |
2008年 | 29篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 23篇 |
2004年 | 16篇 |
2003年 | 14篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有541条查询结果,搜索用时 15 毫秒
71.
A bioenergetics model of the entire life cycle of the three‐spined stickleback,gasterosteus aculeatus 下载免费PDF全文
Charlène Leloutre Alexandre R. R. Péry Jean‐Marc Porcher Rémy Beaudouin 《Ecology of Freshwater Fish》2018,27(1):116-127
A whole life‐cycle bioenergetic model based on the dynamic energy budget (DEB) theory was proposed for the three‐spined stickleback (Gasterosteus aculeatus). To develop this model, experiments on growth and reproduction were performed: adult and juvenile growth, size at first reproduction and amount of eggs spawned by females were monitored under different feeding levels and temperatures. The DEB parameters were estimated, using Bayesian statistics, based on the data produced during these experiments and on other data found in the literature. The model fitted accurately the different data used for the calibration process and, in addition, predicted accurately the data sets used to assess its predictability. Our bioenergetic model of the whole life cycle of the three‐spined stickleback accounting for environmental variations could contribute in many ways to improved ecological assessment: supporting change of scale from individual to populations; developing new biomarkers of exposure and effect; analysing ecotoxicity tests with biology‐based models. 相似文献
72.
73.
74.
75.
José Maria Villela Pádua Kaio Olímpio Das Graças Dias Maria Marta Pastina João Cândido de Souza Valéria Aparecida Vieira Queiroz Rodrigo Veras da Costa Maria Beatriz Pereira da Silva Carlos Alexandre Gomes Ribeiro Claudia Teixeira Guimarães Salvador Alejandro Gezan Lauro José Moreira Guimarães 《Euphytica》2016,211(3):277-285
76.
77.
78.
A combination of plant oils promotes adequate growth of the freshwater catfish Rhamdia quelen (Quoy & Gaimard 1824) 下载免费PDF全文
Rodrigo Javier Vargas Alexandre Sachsida Garcia Sueli Regina Baggio Eduardo Cargnin‐Ferreira Débora Machado Fracalossi 《Aquaculture Research》2015,46(12):3046-3055
Essential fatty acids should be included in the diet to ensure adequate fish growth. Despite the great number of studies on fatty acid nutrition of fish, there are still several unknowns. The aim of the present study was to investigate fatty acid nutrition of jundiá, a Latin American freshwater catfish. Four diets were formulated containing (i) coconut oil (?C, negative control), (ii) coconut oil + high‐docosahexaenoic‐acid‐fish oil (+C, positive control) and coconut + sunflower + linseed oils at different ratios, producing either (iii) a diet rich in linoleic acid (LA) (HighLA) or 4) a diet low in LA (LowLA). All diets contained significant amounts of saturated fatty acids (at least 57.5% total fatty acids in HighLA) and monounsaturated fatty acids (at least 19.1% total fatty acids in ?C). Diets were fed to jundiá fingerlings (1.5 g) for 70 days; growth, body composition and liver histology were evaluated. The ?C diet, without essential fatty acids, promoted significantly lower fish growth, body fat accumulation and hepatic lipidosis. Fish fed HighLA and LowLA diets presented similar growth as fish fed +C diet. These findings suggest that diet formulations for jundiá catfish fingerlings can include only plant oils without negative effect on growth, survival, body composition, fish health or parameters of feed utilization (ingestion rate and protein utilization). 相似文献
79.
Paulo Sergio Pavinato Alexandre Merlin Ciro Antonio Rosolem 《Soil & Tillage Research》2009,105(1):149-155
No-tillage systems lead to physical, chemical and biological changes in soil. Soil fertility is responsive to changes in tillage as it depends on nutrient status, soil water content and biological characteristics. This work aimed to determine long term changes in phosphorus forms and availability in the profile of two tropical soils under conventional and no-till systems, and to discuss the significance of these changes on plant growth and demand for P fertilizers. Undisturbed soil cores with 20 cm in diameter were collected to a depth of 40 cm, accommodated in PVC tubes and taken to a greenhouse, where the experiment was conducted. Two soils were collected in Central Brazil, in areas under Cerrado. Both soils had been cropped for at least 10 years under conventional tillage and no-till. In the greenhouse, pots received phosphorus fertilization or not at 43.7 kg ha−1, and soybean was grown for 60 days, when soil P fractions were determined. Labile P fractions in the soil profile were not affected by management systems, and there was no accumulation of available P under no-till. A large amount of P added as fertilizer was adsorbed in soil and remained in moderately labile fractions, mainly on uppermost soil layers. Therefore, the phosphate fertilizer has promoted P accumulation on less available fractions in soil, remaining P on the soil after crop harvest. Eventually this phosphorus could migrate to more labile fractions and be available for crops grown in succession. 相似文献
80.
Danilo T. Stipp Aline F. Barry Alice F. Alfieri Elisabete Takiuchi Alexandre M. Amude Amauri A. Alfieri 《Tropical animal health and production》2009,41(7):1563-1567
Bovine coronavirus (BCoV) is one of the main causes of neonatal calf diarrhoea. Several diagnostic assays have been employed
to detect the presence of the virus in stool samples from calves. Despite this, the frequency of BCoV infection among Brazilian
and even South American cattle herds has yet to be well characterised. This study describes the occurrence of BCoV infection
among calves from dairy and beef herds in four Brazilian states. A total of 282 stool samples from 1 to 60-day-old calves
were evaluated for the presence of BCoV by a semi-nested (SN) PCR assay. The animals were from herds (n = 23) located in three geographical regions in Brazil (south, southeast, and center-west). The specific BCoV amplicon was
detected in 15.6% (44/282) of the faecal specimens examined, of which 95.4% (42/44) were from diarrhoeic and 4.6% (2/44) from
asymptomatic calves. The specificity of the SN-PCR amplicons was evaluated by restriction fragment length polymorphism (RFLP)
analysis. The results show that the BCoV is widespread, mainly among calves from 16 to 30-days-old (p = 0.0023), and verify the association between BCoV infection and clinical signs of diarrhoea (p = 0.005). These findings emphasise the importance of this virus in enteric infections of Brazilian cattle herds. 相似文献