全文获取类型
收费全文 | 469篇 |
免费 | 71篇 |
专业分类
林业 | 36篇 |
农学 | 33篇 |
基础科学 | 1篇 |
76篇 | |
综合类 | 12篇 |
农作物 | 30篇 |
水产渔业 | 50篇 |
畜牧兽医 | 218篇 |
园艺 | 15篇 |
植物保护 | 69篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 20篇 |
2020年 | 24篇 |
2019年 | 23篇 |
2018年 | 34篇 |
2017年 | 38篇 |
2016年 | 47篇 |
2015年 | 17篇 |
2014年 | 42篇 |
2013年 | 43篇 |
2012年 | 28篇 |
2011年 | 28篇 |
2010年 | 32篇 |
2009年 | 25篇 |
2008年 | 24篇 |
2007年 | 20篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 12篇 |
2003年 | 8篇 |
2002年 | 4篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有540条查询结果,搜索用时 31 毫秒
101.
Elorri Arevalo Henrique N. Cabral Bertrand Villeneuve Carl Possémé Mario Lepage 《Fish and Fisheries》2023,24(3):466-487
Early life stages of fish (eggs and larvae) are particularly vulnerable with mortality rates of up to 99% recorded for a large number of species. High mortality rates result from the limited swimming ability of larvae preventing them from escaping sub-optimal environmental conditions, predators or low prey density areas. In this context, estuaries are key nursery areas for larval and juvenile fish. Estuarine habitats offer environmental conditions favourable to the survival and growth of early stages, through abundant good-quality prey and protection from predators. A vast literature on larvae occurring in temperate estuaries exists, but an overall perspective is lacking. The occurrence of fish larvae in temperate estuaries depends on several factors. First, the choice of spawning time and location is primordial, as they have evolved to optimise the entry and the retention of larvae in the estuary as well as the conditions experienced by young stages. Secondly, larval growth and survival depend on key environmental factors (e.g. salinity, water temperature, freshwater inputs, turbidity and dissolved oxygen concentration). Knowledge of the larval dynamics in temperate estuaries is scarce for some topics and biased towards some species or geographical areas. The main goal of the present literature review is to synthesise existing knowledge regarding spawning timing and location and larval ecology for fish species occurring in coasts and estuaries, identifying the main patterns, consensus or conflicting hypotheses and highlighting major gaps. Research needs and future perspectives were outlined. 相似文献
102.
Three diagrammatic grading keys were designed for the assessment of the severity of late blight (caused by Phytophthora infestans ) in tomato leaves. Simplified and broad keys considered, respectively, six (3, 12, 22, 40, 60 and 77%) and eight (3, 6, 12, 22, 40, 60, 77 and 90%) levels of disease severity, whilst a modified key based on a previous proposal for potato late blight considered six levels (1, 5, 10, 16, 32 and 50%). The keys were validated by 24 evaluators who assessed digital images of tomato leaves exhibiting different areas with lesions. Evaluator errors were compared using a mixed model in which evaluators were considered as random effects and the keys and evaluations as fixed effects. The accuracy and precision of the evaluators were compared by simple linear regression between the estimated and actual values of disease severity. The repeatability of evaluators was assessed using Pearson's correlation coefficient. There was significant ( P ≤ 0·001) variability amongst the errors made by evaluators, although the precision of each of the three keys was high with a coefficient of determination (R2 ) of 0·96, 0·93 and 0·83 for the simplified, broad and modified key, respectively. Repeatability of estimations amongst the evaluators was adequate (correlation coefficients of 0·91, 0·91 and 0·90 for the three keys, respectively). The simplified and broad keys resulted in higher precision and accuracy for the estimation of severity than did the modified key. Since the simplified key considers a smaller number of disease severity levels, its use is recommended in the assessment of late blight in tomato leaves. 相似文献
103.
Julio C. Barbosa Sarah S. Barreto Alice K. Inoue-Nagata Marcelo S. Reis Ana Carolina Firmino Armando Bergamin Filho Jorge Alberto Marques Rezende 《Journal of General Plant Pathology》2009,75(6):440-443
Nicandra physaloides, a common weed in South America, was found to be infected by an isolate of Tomato severe rugose virus (ToSRV), a bipartite begomovirus. The plants developed severe yellow rugose mosaic and were collected in São Paulo State, Brazil. This isolate of ToSRV was transmitted by Bemisia tabaci B biotype from infected plants of N. physaloides to healthy plants of N. physaloides and tomato in a glasshouse. This is the first report of natural infection of N. physaloides by ToSRV in Brazil. 相似文献
104.
Bastianel M de Oliveira AC Cristofani M Filho OG Freitas-Astúa J Rodrigues V Astúa-Monge G Machado MA 《Phytopathology》2006,96(10):1092-1096
ABSTRACT The genetic inheritance of resistance to leprosis, the most important viral disease of citrus in Brazil, was characterized through the phenotypic assessment of 143 hybrids resulting from crosses between tangor 'Murcott' (Citrus sinensis x C. reticulata) and sweet orange 'Pêra' (C. sinensis), considered to be resistant and susceptible to the disease, respectively. All plants were grafted onto Rangpur lime (C. limonia) and inoculated with Citrus leprosis virus, cytoplasmic type through the infestation with viruliferous mites, Brevipalpus phoenicis. The experiments were arranged in a completely randomized block design with 10 replicates. Incidence and severity of the disease in leaves and stems as well as plant growth parameters (plant height and stem diameter) were recorded for 3 years after the infestation with the viruliferous mites. The average values of all variables were analyzed using principal component analysis, discriminant factorial analysis, estimation of the clonal repeatability coefficients, and frequency of the distributions of the average values for each measured variable. The principal component analysis resulted in the identification of at least two groups with resistance and susceptibility to leprosis, respectively. About 99% of all hybrids were correctly classified according to the discriminant factorial analysis. The broad-sense heritability coefficients for characteristics associated with incidence and severity of leprosis ranged from 0.88 to 0.96. The data suggest that the inheritance of resistance to leprosis may be controlled by only a few genes. 相似文献
105.
Effects of some lignans and neolignans on the development and excretion of Rhodnius prolixus. 总被引:2,自引:0,他引:2
The effects of six lignans and neolignans as inhibitors of ecdysis and on the water balance in fourth-instar larvae of Rhodnius prolixus were studied by oral, topical and continuous contact treatments. The main results may be summarised as follows: (i) burchellin, pinoresinol, sesamin, licarin A and nordihydroguaiaretic acid (NDGA) did not cause feeding inhibition at doses of 100 micrograms/ml blood; podophyllotoxin had no antifeedant effect but caused a high moulting inhibition and significant toxicity when applied either orally or topically; (ii) the highest ecdysis inhibitory effects were observed with pinoresinol and NDGA when applied orally at a dose of 100 micrograms/ml (58% and 50% of moulting inhibition, respectively); burchellin inhibited 30% of the moulting at this concentration; (iii) by topical treatment none of the compounds presented any influence on the moulting cycle; and (iv) podophyllotoxin and burchellin significantly reduced the excretion of the insect in 24 h; the other compounds had no effect on excretion. The implications of these findings in relation to the pertinent biological events in R. prolixus are discussed. 相似文献
106.
Jordão RS Ribeiro CP Pituco EM Okuda LH Del Fava C Stefano Ed Filho MM Mehnert DU 《Research in veterinary science》2011,91(2):311-315
Bovine Viral Diarrhea Virus (BVDV) is widespread in cattle in Brazil and research shows its large antigenic variability. Available vaccines are produced with virus strains isolated in other countries and may not be effective. In this study, inactivated vaccines containing the Brazilian BVDV-Ib IBSP11 isolate were developed and tested on 6 groups of 10 guinea pigs (Cavia porcellus). Animals in groups A and C received an aqueous vaccine (aluminum hydroxide); B and D groups received an oily vaccine (Montanide ISA50); Group E positive-control animals were given an imported commercial vaccine with BVDV-Ia Singer; Group F animals were sham vaccinated (negative control). Groups A, B and E received two doses, and Groups C and D, three, every 21 days. Twelve blood samples were taken, at 21-day intervals over 231 days, and evaluated for antibody titer through virus-neutralization (VN), using a homologous strain (IBSP11), and a heterologous strain (BVDV-Ia NADL). Most animals, 42 days following the first dose, seroconverted to both strains and, after the second dose, there was a significant increase of titers in all groups. The oily formulation induced greater response after the third administration. This increase was not observed with the aqueous vaccines, regardless of the virus used in the VN. Antibody decline was more rapid in animals that received aqueous vaccines. The results showed the importance of studying the influence of endemic strains of commercial vaccines, to improve the efficacy of BVD vaccination. Use of the endemic strain in vaccine formulation presented promising results, as well as the use of guinea pigs as a laboratory model. 相似文献
107.
Faccio-Demarco Claudia Mumbach Tatiele Oliveira-de-Freitas Vanessa Fraga e Silva-Raimondo Raquel Medeiros-Gonçalves Fernanda Nunes-Corrêa Marcio Burkert-Del Pino Francisco Augusto Mendonça-Nunes-Ribeiro Filho Henrique Cassal-Brauner Cássio 《Tropical animal health and production》2019,51(8):2193-2201
Tropical Animal Health and Production - The aim of the current study was to assess the effect that supplementation with yeast culture plus enzymatically hydrolyzed yeast (YC-EHY) during the... 相似文献
108.
dos Santos Alyce Raiana Monteiro Cabral Carla Heloísa Avelino Cabral Carlos Eduardo Avelino de Barros Lívia Vieira de Barros Jackelliny Melo Cabral Welton Batista Dias Milene Rodrigues 《Tropical animal health and production》2019,51(8):2395-2403
Tropical Animal Health and Production - This study evaluated the effect of energy and protein supplementation on the nutritional characteristics, ingestive behavior, and productive performance in... 相似文献
109.
Andressa Santanna Natel Adibe Luiz Abdalla Rafael Canonenco de Araujo Concepta McManus Tiago do Prado Paim Adibe Luiz de Abdalla Filho Patrícia Louvandini Carina Nazato 《Animal Science Journal》2019,90(10):1350-1361
The objective of this study was to evaluate the effects of using encapsulated nitrate product (ENP) replacing soybean meal in diets differing in concentrate to forage ratio on ruminal fermentation and methane production in vitro using a semi‐automatic gas production technique. Eight treatments were used in a randomized complete design with a 2 × 4 factorial arrangement: two diet (20C:80F and 80C:20F concentrate to forage ratio) and four levels of ENP addition (0%, 1.5%, 3.0%, and 4.5% of DM) replacing soybean meal. There was a diet × ENP interaction (p = 0.02) for methane production. According to ENP addition, diets with 80C:20F showed more intense reduction on methane production that 20C:80F. A negative linear effect was observed for propionate production with ENP addition in diet with 80C:20F and to the relative abundance of methanogens Archaea, in both diet. The replacement of soybean meal by ENP in levels up to 3% of DM inhibited methane production due to a reduction in the methanogens community without affecting the organic matter degradability. However, ENP at 4.5% of DM level affected fiber degradability, abundance of cellulolytic bacteria, and propionic acid production, indicating that this level of inclusion is not recommended for ruminant production. 相似文献
110.
Effects of Growth Hormone on In Situ Culture of Bovine Preantral Follicles are Dose Dependent
下载免费PDF全文
![点击此处可从《Reproduction in domestic animals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
CR Jimenez JL de Azevedo RG Silveira J Penitente‐Filho EL Carrascal‐Triana AM Zolini VR Araújo CAA Torres 《Reproduction in domestic animals》2016,51(4):575-584
The objective of this study was to evaluate different concentrations of growth hormone (GH) on the development of bovine preantral follicles cultured included in the ovarian tissue (in situ) on the rates of morphologically normal, viable, primordial and developing follicles, as well as the oocyte and follicle diameter and ultrastructural analysis. Ovarian fragments collected from cows with no cross‐breeds defined were cultured in situ for 1 and 7 days in minimal essential medium (α‐MEM+) supplemented with different concentrations of recombinant human GH (0, 10, 25, 50 ng/ml). The ovarian fragments non‐cultured (control) and cultured were processed for classic histology, mechanical isolation and electron transmission microscopy (MET). The parameters underwent anova (Tukey′s and Dunnett′s tests) and chi‐square test (χ2). After 7 days of culture, the treatment with 50 ng/ml GH showed no differences with fresh control (p > 0.05) and had greater effectiveness than in the 0, 10 and 25 ng/ml GH concentrations of the morphologically normal follicles. Regarding the primordial follicles, a reduction was observed in the 50 ng/ml GH concentration concomitant with the significant increase in developing follicles, differing from both the fresh control and the other GH concentrations tested. In addition, 50 ng/ml GH showed a larger follicle and oocyte diameter when compared to the other treatments cultured. Similar structures were ultrastructurally observed in the control group, 50 ng/ml GH. Follicles cultured in 10 ng/ml GH showed nuclear invagination, vacuoles and lesioned basal membrane. Hence, it is concluded that 50 ng/ml GH is the most effective concentration for the development of preantral follicles cultured in situ. 相似文献