全文获取类型
收费全文 | 226篇 |
免费 | 28篇 |
专业分类
林业 | 13篇 |
农学 | 6篇 |
47篇 | |
综合类 | 2篇 |
农作物 | 16篇 |
水产渔业 | 52篇 |
畜牧兽医 | 79篇 |
园艺 | 5篇 |
植物保护 | 34篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 22篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 23篇 |
2017年 | 12篇 |
2016年 | 18篇 |
2015年 | 10篇 |
2014年 | 13篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 3篇 |
2006年 | 6篇 |
2005年 | 5篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
排序方式: 共有254条查询结果,搜索用时 296 毫秒
101.
102.
Impact of no-tillage agricultural systems on sediment yield in two large catchments in Southern Brazil 总被引:1,自引:0,他引:1
Elizeu Jonas Didoné Jean Paolo Gomes Minella José Miguel Reichert Gustavo Henrique Merten Leandro Dalbianco Cláudia Alessandra Peixoto de Barrros Rafael Ramon 《Journal of Soils and Sediments》2014,14(7):1287-1297
Purpose
The impact of agriculture on water resources has long been a problem associated with the formation of runoff, the siltation of lakes and reservoirs, and overall depletion of water quality. In Brazil, these problems are mainly related to soil degradation by water erosion. However, studies of catchment-scale erosion are still rare particularly in grain-producing regions which have adopted conservative tillage systems for soil protection. In order to contribute to a better understanding of the impact of conservation agriculture on water resources, this study determined the runoff coefficient and sediment yield for two agricultural catchments.Materials and methods
Hydrological and sedimentological monitoring was conducted in two catchments: the Conceicao catchment is characterized by grain production in weathered soils and a gently sloping landscape, while the Guapore catchment is characterized by heterogeneous soils and topography. Both catchments have problems associated with water erosion.Results and discussion
The magnitudes of annual runoff coefficients and sediment yield were high, even if compared to similar agricultural regions, including a catchment with widespread adoption of no-tillage. The sediment yield was 140 t km?2 year?1, and the runoff coefficient was 14 % for the Conceicao catchment, while the sediment yield was 270 t km?2 year?1, and the runoff coefficient was 31 % for the Guapore catchment. The results indicate that problems such as gullies, soil compaction, runoff, floods, siltation, and water quality depletion associated with the misuse of agricultural areas in terms of soil conservation and water use are still evident and important even in regions with widespread adoption of no-tillage systems.Conclusions
The magnitudes of both runoff and sediment yield clearly indicate the need to adopt complementary practices of soil conservation measures, such as mechanical runoff control. 相似文献103.
Costa LS Telles CB Oliveira RM Nobre LT Dantas-Santos N Camara RB Costa MS Almeida-Lima J Melo-Silveira RF Albuquerque IR Leite EL Rocha HA 《Marine drugs》2011,9(4):603-614
Fucan is a term used to denominate a family of sulfated polysaccharides rich in sulfated l-fucose. Heterofucan SF-1.5v was extracted from the brown seaweed Sargassum filipendula by proteolytic digestion followed by sequential acetone precipitation. This fucan showed antiproliferative activity on Hela cells and induced apoptosis. However, SF-1.5v was not able to activate caspases. Moreover, SF-1.5v induced glycogen synthase kinase (GSK) activation, but this protein is not involved in the heterofucan SF-1.5v induced apoptosis mechanism. In addition, ERK, p38, p53, pAKT and NFκB were not affected by the presence of SF-1.5v. We determined that SF-1.5v induces apoptosis in HeLa mainly by mitochondrial release of apoptosis-inducing factor (AIF) into cytosol. In addition, SF-1.5v decreases the expression of anti-apoptotic protein Bcl-2 and increased expression of apoptogenic protein Bax. These results are significant in that they provide a mechanistic framework for further exploring the use of SF-1.5v as a novel chemotherapeutics against human cervical cancer. 相似文献
104.
Rafael Augusto Vieira Carlos Alberto Scapim Lia Mara Moterle Dauri José Tessmann Antonio Teixeira do Amaral Júnior Leandro Simões Azeredo Gonçalves 《Euphytica》2012,185(3):325-336
The combining ability and genetic parameters of maize grown in two different environments of diseases pressure were estimated
for partial resistance to northern leaf blight (Exserohilum turcium, NLB) and gray leaf spot (Cercospora spp., GLS). Nine inbred lines were crossed in a complete diallel mating scheme including reciprocals. Two experiments were
carried out to test the hybrids using randomised complete blocks design with three replications during the growing season
2008/2009. The severities of NLB and GLS were assessed under natural infestation conditions. The first experiment was the
lowest NLB and GLS pressure environment, whereas the second was the highest. Data was evaluated using individual and joint
Griffing’s diallel analyses. General and specific combining abilities were significant (P < 0.10) for NLB and GLS resistance under both pressures. Although additive and nonadditive gene effects were significant,
the additive gene effects were more important for resistance to the diseases. The lines 1 (P83), 6 (P30F) and 7 (Pst) had the most outstanding general combining ability for NLB resistance, and the line 3 (P80) was outstanding for resistance to GLS. Based on both diseases resistance and grain yield, the synthetic composites 6 × 7 × 3
and (6 × 7) × 3 were recommended for intrapopulational breeding using recurrent selection. Three promising hybrid combinations
(the 3 × 6, and 5 × 7 for resistance to NLB, and 3 × 9 for resistance to GLS) were recommended for interpopulational breeding.
Resistance levels to NLB and GLS resistance were better discriminated under HP than LP conditions; however, promising lines
were detected under both pressures. 相似文献
105.
Zucchi OL Moreira S Salvador MJ Santos LL 《Journal of agricultural and food chemistry》2005,53(20):7863-7869
Several commercial soft drinks and respective plastic bottles were analyzed for their multielement contents employing the synchrotron radiation total reflection X-ray fluorescence spectrometry technique (SRTXRF). The SRTXRF method has been developed and validated, and about 20 elements were detected in the investigated samples, including some trace elements, which can be toxic for human beings, such as Ti, Cr, Sb, As, and Pb in soft drinks and Al, Sb, As, and Pb in poly(ethylene terephthalate) (PET) containers. Statistical analysis was performed using chemometric techniques (principal component analysis and cluster analysis), and similarities were verified in the multielement contents of the samples. The results demonstrated that the SRTXRF offers a good multielemental approach for the quality control of food products. Moreover, on the basis of enrichment factors, the possibility of the trace elements in the PET container may be leached to the beverages under normal commercial situations and other results were discussed. 相似文献
106.
Canas S Leandro MC Spranger MI Belchior AP 《Journal of agricultural and food chemistry》1999,47(12):5023-5030
Oak and chestnut species have been largely used for the aging of brandies, but nowadays chestnut is rarely used. There have been no previous studies regarding the cooperage utilization of chestnut wood. This study provides, for the first time, specific information about the characterization of the northern Portuguese Castanea sativa wood and examines the influence of this wood and its heat treatment on the chemical composition of two-year-aged brandies, by the quantitative determination (HPLC) of low molecular weight phenolic compounds. The predominance of gallic acid among the analyzed extractable compounds both in chestnut wood and in the corresponding aged brandies was remarkable. The heat treatment has a very significant influence on the majority of extractable compounds analyzed. Thus, it could be responsible for the related sensorial properties of aged brandies and greatly affect their general balance. 相似文献
107.
Bernardo Melo Montes Nogueira Borges Rilner Alves Flores Hilário Júnior de Almeida Leandro Rossato Moda Renato de Mello Prado 《Journal of plant nutrition》2016,39(11):1627-1633
The correct nutrition of basil (Ocinum basilicum L.) is important to increase its production and quality; however, few papers have deal with this subject. The aim of this work was to evaluate the effects of omission of individual macronutrients on the growth and nutritional status of basil cultivated in nutritive solution. The treatments consisted of nutrient solutions with nitrogen, phosphorus, potassium, calcium, magnesium or sulfur (N, P, K, Ca, Mg, or S) omissions and a complete solution treatment. The plants were cultivated in 8 L plant pots. Plant height, number of leaves per plant, leaf area, relative chlorophyll index, net photosynthesis rate, stomatal conductance, plant dry matter, concentration levels of macronutrients in the aerial part and root system, and nutritional disorders were all evaluated. Nutrient omission was a limiting factor for plant development, substantially reducing its growth. There was also a considerable decrease in nutrient accumulation when compared to the control treatment. 相似文献
108.
Carla Amorim Neves Isabela Plazza Bittar Leandro Arévalo Prieto Luiz Antônio Franco da Silva Emmanuel Arnhold Aline Maria Vasconcelos Lima Naida Cristina Borges 《Anatomia, histologia, embryologia》2021,50(2):333-344
A longitudinal study was conducted to identify the morphological development of eyes and head of Jersey cattle at different ages. A total of 48 healthy Jersey cattle, 1 to 58 months of age, were included in the study. Ophthalmologic examinations were performed to identify healthy cattle to form the age groups: GI (1- to 11-month-old), GII (16- to 24-month-old) and GIII (25- to 58-month-old). The animals were physically restrained and examined by transcorneal ultrasound of both eyes; the axial length (AxL), corneal thickness (CO), lenticular thickness (L), depth of the anterior (AC) and vitreous (VC) chambers were evaluated. The cranial measurements obtained included the total, cranial, and nasal lengths and widths. Subsequently, the cephalic index (CI) was calculated. The AxL (GI: 2.83 cm; GII: 3.16 cm; GIII: 3.24 cm), AC (GI: 0.44 cm; GII: 0.53 cm; GIII: 0.53 cm), L (GI: 0.88 cm; GII: 1.01 cm; GIII: 1.04 cm) and VC (GI: 1.44 cm; GII: 1.55 cm; GIII: 1.59 cm) increased (p ≤ .001) according to age, but the CO (GI: 0.07 cm; GII: 0.08 cm; GIII: 0.08 cm) (p > .05) did not. The total length (GI: 30.83 cm; GII: 43.29 cm; GIII: 44.15 cm), cranial length (GI: 18.11 cm; GII: 23.82 cm; GIII: 22.69 cm), nasal length (GI: 12.72 cm; GII: 19.47 cm; GIII: 21.46 cm) and nasal width (GI: 26.22 cm; GII: 33.82 cm; GIII: 34.00 cm) increased (p < .001), and the CI (GI: 85.66 cm; GII: 78.15 cm; GIII: 77.02 cm) decreased (p < .001). The AxL correlated positively (p < .001) with the cranial length and width and negatively with the CI (p > .05). The ocular biometry of Jersey cattle correlates with their cranial measurements at different ages. With increasing age, the eyes and the head grow, establishing growth curves similar to those of other mammals. 相似文献
109.
Celina Emiko OKAMOTO-OKUBO Renata Navarro CASSU Jean Guilherme Fernandes JOAQUIM Luciane dos REIS MESQUITA Sheila Canevese RAHAL Hugo S Salvador OLIVEIRA Regina TAKAHIRA Isadora ARRUDA Leandro MAIA Fernanda da CRUZ LANDIM Stelio Pacca Loureiro LUNA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2021,83(5):881
110.
Laurance WF Albernaz AK Fearnside PM Vasconcelos HL Ferreira LV 《Science (New York, N.Y.)》2004,304(5674):1109-1111