全文获取类型
收费全文 | 905篇 |
免费 | 101篇 |
专业分类
林业 | 42篇 |
农学 | 31篇 |
基础科学 | 3篇 |
131篇 | |
综合类 | 49篇 |
农作物 | 43篇 |
水产渔业 | 113篇 |
畜牧兽医 | 511篇 |
园艺 | 10篇 |
植物保护 | 73篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 26篇 |
2021年 | 36篇 |
2020年 | 54篇 |
2019年 | 52篇 |
2018年 | 53篇 |
2017年 | 54篇 |
2016年 | 53篇 |
2015年 | 30篇 |
2014年 | 48篇 |
2013年 | 58篇 |
2012年 | 53篇 |
2011年 | 62篇 |
2010年 | 43篇 |
2009年 | 44篇 |
2008年 | 43篇 |
2007年 | 41篇 |
2006年 | 22篇 |
2005年 | 21篇 |
2004年 | 23篇 |
2003年 | 25篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 18篇 |
1999年 | 13篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1971年 | 3篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1006条查询结果,搜索用时 15 毫秒
271.
de Castro AM Cortez A Heinemann MB Brandão PE Richtzenhain LJ 《Research in veterinary science》2008,85(1):197-200
Porcine circovirus 2 (PCV-2) is associated with a broad range of syndromes. In this study, eight pig tissue samples from two Brazilian states were analyzed using six PCR primer pairs amplifying a 1705-bp fragment of the PCV-2 genome. The NJ distance-based method was used for the phylogenetic analysis with the eight field strains herein, 15 GenBank sequences and using PCV-1 as an out-group. This yielded two major clusters (A and B) for this viral species, with the Brazilian strains segregating with European and Asian sequences. Nucleotide identity was 99.7 to 100% among the sequences. This information can be used in further studies of pathogenesis related to PCV-2 in Brazil. 相似文献
272.
273.
Amanda Mara Teles Leticia Prince Pereira Pontes Sulayne Janayna Araújo Guimares Ana Luiza Butarelli Gabriel Xavier Silva Flavia Raquel Fernandes do Nascimento Geusa Felipa de Barros Bezerra Carla Junqueira Moragas-Tellis Rui Miguel Gil da Costa Marcos Antonio Custdio Neto da Silva Fernando Almeida-Souza Ktia da Silva Calabrese Ana Paula Silva Azevedo-Santos Maria do Desterro Soares Brando Nascimento 《Marine drugs》2020,18(11)
Background: This study addresses the antitumoral properties of Penicillium purpurogenum isolated from a polluted lagoon in Northeastern Brazil. Methods: Ethyl Acetate Extracellular Extract (EAE) was used. The metabolites were studied using direct infusion mass spectrometry. The solid Ehrlich tumor model was used for antitumor activity. Female Swiss mice were divided into groups (n = 10/group) as follows: The negative control (CTL−), treated with a phosphate buffered solution; the positive control (CTL+), treated with cyclophosphamide (25 mg/kg); extract treatments at doses of 4, 20, and 100 mg/kg; animals without tumors or treatments (Sham); and animals without tumors treated with an intermediate dose (EAE20). All treatments were performed intraperitoneally, daily, for 15 days. Subsequently, the animals were euthanized, and the tumor, lymphoid organs, and serum were used for immunological, histological, and biochemical parameter evaluations. Results: The extract was rich in meroterpenoids. All doses significantly reduced tumor size, and the 20 and 100 mg/kg doses reduced tumor-associated inflammation and tumor necrosis. The extract also reduced the cellular infiltration of lymphoid organs and circulating TNF-α levels. The extract did not induce weight loss or renal and hepatic toxic changes. Conclusions: These results indicate that P. purpurogenum exhibits immunomodulatory and antitumor properties in vivo. Thus, fungal fermentation is a valid biotechnological approach to the production of antitumor agents. 相似文献
274.
根据目前拖网渔船在节能方面的需要,采用导管螺旋桨以改善渔船的推进性能,并对导管螺旋桨的设计和具体应用的优的缺点作初步的探讨。 相似文献
275.
M D Gomes Da Silva H J Chaves Das Neves 《Journal of agricultural and food chemistry》1999,47(11):4568-4573
The aroma compositions of Fragaria ananassa varieties are assessed by purge-and-trap high-resolution gas chromatography. Gas chromatography/mass spectrometry and gas chromatography/Fourier transform infrared spectroscopy allow the identification of 93 components from which 21 are for the first time described as constituents of strawberry aroma. Despite the complexity of the aroma, sensory properties are assigned to 40 components as perceived by three independent testers by application of a sniffing technique to the chromatographic effluent. The data are used for comparative sensory characterization of strawberry varieties by means of principal component analysis. 相似文献
276.
277.
Larissa Strictar Pereira Jos Antnio Demtrio Almir Manoel Cunico Joo Diro Latini Luiz Carlos Gomes Angelo Antonio Agostinho 《Aquaculture Research》2019,50(10):2896-2906
The influence of cage aquaculture on the attraction and aggregation of wild fish was evaluated with an experimental tilapia farming structure. The structure was installed in the Corvo River, Rosana Reservoir, Paranapanema River basin, for 140 days. Samples were taken before and after farming began. Gillnets on the surface and near the bottom at different distances from the cages (0, 100 and 400 m) were used for fish sampling. The effects of the food supply at two protein levels were also analysed: Phase 1 = 32% PB and Phase 2 = 28% PB. Changes in species richness and abundance were observed, with the number of individuals and the fish biomass increasing significantly just after the farming began. Some species, such as Iheringichthys labrosus, presented increased abundance near the cages, while others, such as Plagioscion squamosissimus, were more abundant far from the cages. Auchenipterus osteomystax was the most abundant species during the experiment, especially when the protein content of the pellets was higher. It was demonstrated that farming tilapia in cages profoundly altered the abundance and composition of the wild ichthyofauna, suggesting the need to propose effective regulations for such activities, including fisheries restrictions in farmed areas or even the prohibition of cage farming. 相似文献
278.
Bruno dos Santos Sosa Evandro Bilha Moro Riccio Luan Marques Gomes Matheus dos Santos Cardoso Leonardo Machado Cardoso Wilson Rogrio Boscolo Jos Dilson Silva de Oliveira Altevir Signor Fbio Bittencourt 《Aquaculture Research》2020,51(7):2758-2765
The objective of this study was to evaluate the inclusion of increasing levels of a commercial mix of essential oils (EOs) from cashew (Anacardium occidentale) and castor bean (Ricinus communis) as an additive in diets for Nile tilapia. Thus, 240 juveniles with an initial weight of 35.06 ± 1.02 g were distributed in a completely randomized design (four treatments and six replicates) in 24 cylindrical‐tapered tanks; the fish were fed for 60 days, four times a day, diets containing increasing levels of EO (0.10, 0.15 and 0.20%) and a control diet (without the additive). After the experimental period, the animals were desensitized, and an aliquot of blood was collected for the biochemical analysis; they were subsequently euthanized for the evaluation of productive performance and fillet chemical composition. No significant differences (p > .05) were observed in the analyses of productive performance, fillet chemical composition, and triglycerides, VLDL, total proteins, urea and glucose. However, significant differences (p < .05) were observed in the analyses of total cholesterol, HDL and LDL. Inclusion above 0.15 of the additive showed an improvement in the levels of lipoprotein carriers, increasing HDL levels and decreasing LDL values, without interfering with the fish productive performance. 相似文献
279.
Adriano Carvalho Costa Hortência Aparecida Botelho Richardson Cesar da Silva Gomes Sergio Augusto de Sousa Campos Rafael Vilhena Reis Neto Marcio Balestre Fernanda Dotti do Prado Diogo Teruo Hashimoto Diego Galetti Martins Fbio Porto‐Foresti Mrio Lima Rilke Tadeu Fonseca de Freitas 《Aquaculture Research》2019,50(3):717-724
This work was carried out to predict the combining abilities, both general and specific, for performance traits and bodily yields of Serrasalmidae. Ninety‐six 30‐day‐old juveniles were purchased from two commercial fish farms, 12 of each of the following eight genetic groups: pacu, pirapitinga, tambaqui, tambacu, tambatinga, patinga, paqui and piraqui. Six fish from each genetic group were grown in 500‐L fibreglass tanks (two tanks per genetic group) until they were 495 days old. At the end of the growth period fish were weighed, subjected to morphometric analysis and processed to obtain their bodily yields. Two nuclear markers and one mitochondrial marker were used to confirm the identity of the animals. Combining abilities were obtained using the method proposed by Griffing in 1956 (Australian Journal of Biological Science, 4, 463–493) adapted to a mixed models analysis, environmental effects were estimated by the empirical best linear unbiased estimator method and genetic effects (general and specific combining abilities) were estimated with the empirical best linear unbiased predictor. Predictions of the combining abilities of advanced hybrids were obtained by the mixed models mixture method with normal distributions. Tambaqui showed higher general and specific combining abilities than the other groups for most of the variables, making it the most important genetic group. General combining ability makes a greater contribution to phenotypic variance than specific combining ability for most variables, indicating a predominance of genes with an additive effect in the control of evaluated traits. 相似文献
280.