全文获取类型
收费全文 | 585篇 |
免费 | 61篇 |
专业分类
林业 | 66篇 |
农学 | 12篇 |
124篇 | |
综合类 | 20篇 |
农作物 | 35篇 |
水产渔业 | 86篇 |
畜牧兽医 | 235篇 |
园艺 | 11篇 |
植物保护 | 57篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 25篇 |
2020年 | 28篇 |
2019年 | 32篇 |
2018年 | 37篇 |
2017年 | 39篇 |
2016年 | 35篇 |
2015年 | 24篇 |
2014年 | 27篇 |
2013年 | 44篇 |
2012年 | 38篇 |
2011年 | 49篇 |
2010年 | 21篇 |
2009年 | 32篇 |
2008年 | 25篇 |
2007年 | 28篇 |
2006年 | 21篇 |
2005年 | 12篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 10篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 4篇 |
1983年 | 1篇 |
1974年 | 2篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有646条查询结果,搜索用时 15 毫秒
601.
Lúcia Fernandes Margarida Rocheta Jorge Cordeiro Sandra Pereira Sophie Gerber Maria M. Oliveira Maria M. Ribeiro 《Annals of Forest Science》2008,65(7):706-706
602.
Coffee (Coffea canephora var robusta) is grown in Southwestern Togo under shade of native Albizia adianthifolia as a low input cropping system. However, there is no information on carbon and nutrient cycling in these shaded coffee systems.
Hence, a study was conducted in a mature coffee plantation in Southwestern Togo to determine carbon and nutrient stocks in
shaded versus open-grown coffee systems. Biomass of Albizia trees was predicted by allometry, whereas biomass of coffee bushes was estimated through destructive sampling. Above- and
belowground biomass estimates were respectively, 140 Mg ha−1 and 32 Mg ha−1 in the coffee–Albizia association, and 29.7 Mg ha−1 and 18.7 Mg ha−1 in the open-grown system. Albizia trees contributed 87% of total aboveground biomass and 55% of total root biomass in the shaded coffee system. Individual
coffee bushes consistently had higher biomass in the open-grown than in the shaded coffee system. Total C stock was 81 Mg ha−1 in the shaded coffee system and only 22.9 Mg ha−1 for coffee grown in the open. Apart from P and Mg, considerable amounts of major nutrients were stored in the shade tree
biomass in non-easily recyclable fractions. Plant tissues in the shaded coffee system had higher N concentration, suggesting
possible N fixation. Given the potential for competition between the shade trees and coffee for nutrients, particularly in
low soil fertility conditions, it is suggested that the shade trees be periodically pruned in order to increase organic matter
addition and nutrient return to the soil.
An erratum to this article can be found at 相似文献
603.
Fabiano A. PETTER Tamara S. FERREIRA Adilson P. SINHORIN Larissa B. LIMA Fernandes A. ALMEIDA Leandro P. PACHECO Alexandre F. SILVA 《土壤圈》2019,29(6):801-809
The herbicide diuron is widely used in agricultural areas in Brazil, whereas it has high potential for subsurface water contamination due to its physicochemical characteristics. Recent studies have demonstrated the potential of biochar as a sorbent and possible pesticide leaching mitigation. The objective of this study was to investigate the long-term effect of biochar application on the kinetics of sorption and desorption of diuron in a Cerrado Haplic Plinthosol. Samples were collected in an experiment conducted in the field in a randomized block design consisting of the combination of two levels of fertilizer application (0 and 300 kg ha-1 of 5-25-15 formula of NPK fertilizers) and three doses of biochar (0, 16, and 32 Mg ha-1). The Freundlich isotherm accurately described the sorption of diuron in all treatments. Biochar application increased the sorption and reduced the desorption of diuron. This effect was attributed to the contribution of biochar to total organic carbon (C) and C in the humin fraction and to the increase in the reactivity of the humic acid and humin fractions, which was significantly highly correlated with the sorption coefficient (Kf). A positive correlation between the partition coefficient of organic C and Kf confirmed the importance of the soil organic compartment for the sorption of diuron. The higher diuron sorption and lower diuron desorption capacities of sandy soils after biochar application could reduce the potential risk of diuron leaching and contamination of subsurface water. 相似文献
604.
Ángela Taboada Reyes Tárrega Leonor Calvo Elena Marcos José Antonio Marcos José María Salgado 《European Journal of Forest Research》2010,129(1):31-45
The aim of this study was to evaluate the influence of forest structure (mainly resulting from human uses) and forest type (the identity of the dominant tree species) on biodiversity. We determined the diversity of two taxonomical groups: the understory vegetation and the edaphic carabid beetle fauna. We selected eight types of forest ecosystems (five replicates or stands per forest type): pine (Pinus sylvestris) plantations of three age classes (10, 40 and 80 years since reforestation), an old-growth relict natural pine forest, and four types of oak (Quercus pyrenaica) stands: mature forests with livestock grazing and firewood extraction, mature forests where uses have been abandoned, “dehesa” ecosystems and shrubby oak ecosystems. The results obtained by a global PCA analysis indicated that both tree size and dominant species influenced the ordination of the 40 forest stands. In general, carabids were more sensitive to changes in forest heterogeneity and responded more clearly to the analysed structural variables than the understory vegetation, although the species richness of both groups was significantly correlated and higher in case of oak forests. Pine forest ecosystems were characterised by the lowest species richness for both taxonomical groups, the lowest plant diversity and by the lowest coefficients of variation and, consequently, low structural heterogeneity. As a result, it was very difficult to discriminate the effects of the spatial heterogeneity and the dominant tree species on biodiversity. 相似文献
605.
Fasting heat production of Saanen and Anglo Nubian goats measured using open‐circuit facemask respirometry 下载免费PDF全文
M. H. M. da R. Fernandes A. R. C. Lima A. K. Almeida T. H. Borghi I. A. M. de A. Teixeira K. T. de Resende 《Journal of animal physiology and animal nutrition》2017,101(1):15-21
This study aimed to establish the heat production (HP) of Saanen and Anglo Nubian goats at absorptive (feeding) and at post‐absorptive (fasting) statuses to determine the adequate period of fasting required for the measurement of basal metabolism. Gas exchange was recorded via open‐circuit facemask respirometry. Six non‐lactating and non‐pregnant goats of each breed, Saanen (49.2 ± 3.2 kg of body weight, BW) and Anglo Nubian (64.0 ± 3.0 kg BW), were placed in individual pens with ad libitum access to the same total mixed ration. After a 3‐day feeding period, the animals were subjected to fasting (no feed), and the gas exchange measurement was performed for 30 min at 0, 12, 20, 36, 44, 60 and 68 h after fasting. The daily HP of the Saanen and Anglo Nubian goats averaged 557.4 ± 38.7 and 357.1 ± 35.3 kJ/kg0.75 BW day respectively. During fasting, the methane production decreased exponentially in both breeds, and the critical time when methane production was statistically equal to zero was at 31 h of fasting for the Saanen goats and at 40 h for the Anglo Nubian goats. The daily HP and respiratory exchange rate during fasting decreased up to 60 h. Taken together, our results suggest that the ideal period to measure fasting heat production (FHP) for goats fed at maintenance levels should be between 40 h and 60 h of fasting. Consequently, the daily FHP, after 60 h of fasting, of Saanen and Anglo Nubian goats was 183.3 ± 16.3 and 211.1 ± 11.5 kJ/kg0.75 BW day respectively. The results presented herein are relevant for future studies of energy metabolism in goats. 相似文献
606.
Alexandre Fernandes Perazzo Sansão de Paula Homem Neto Ossival Lolato Ribeiro Edson Mauro Santos Gleidson Giordano Pinto de Carvalho Juliana Silva de Oliveira Higor Fábio Carvalho Bezerra Fleming Sena Campos José Esler de Freitas Junior 《Tropical animal health and production》2017,49(4):717-724
This study aimed to evaluate the effect of diets with ammoniated buffel grass hay on the ingestive behavior of feedlot lambs. Thirty-two sheep of no defined breed with an average body weight of 17.7?±?1.8 kg were used. A completely randomized design with four treatments (0, 18, 36, and 54 g/kg dry matter (DM) basis) and eight repetitions was used. Ingestive behavior, rumination, and idle time were similar (P?>?0.05) among the diets containing ammoniated buffel grass hay, with mean values of 294.5, 554.44, and 594.25 min per day, respectively. Regarding the chews, all of the variables resulted in similar behavior (P?>?0.05). The quadratic effect (P?<?0.05) observed for daily intake can be explained based on the amount of DM and neutral detergent fiber (NDF) per meal per rumination. There was no effect of urea levels from the ammoniation (P?>?0.05) on the efficiency of DM and NDF consumption. However, the rumination efficiency of DM and NDF showed a quadratic effect (P?<?0.05). Thus, the use of ammoniated buffel grass hay with urea in lamb diet affects the ingestive behavior by increasing the rumination efficiency, increased intake, and feed utilization. 相似文献
607.
608.
Vinícius Fernandes Canassa Edson Luiz Lopes Baldin José Paulo Franco Bentivenha Luiz Eduardo da Rocha Pannuti André Luiz Lourenção 《国际虫害防治杂志》2017,63(2):112-118
Soybeans are of great importance in the world agricultural landscape, and their productive potential is significantly reduced by attacks from insect pests. Factors such as the expansion of national agricultural regions, together with no-tillage management and “off-season” maize cultivation, have favored the increase of secondary species such as Dichelops melacanthus (Dallas) (Hemiptera: Pentatomidae), intensifying the damage caused by the soybean stink bug complex. The use of resistant genotypes may be a valuable strategy as an alternative to the excessive use of chemical control in crops. This study evaluated the attractiveness and feeding preferences of the green-belly stink bug in 17 soybean genotypes in different maturity groups (early, semiearly, and late) to characterize the expression of antixenosis resistance. To this end, free-choice tests of attractiveness and food preference were performed under laboratory conditions. The early genotypes PI 171451 and D 75-10169, the semiearly genotypes IAC 78-2318, “IAC 100”, IAC 74-2832, PI 227687, and “IAC 24” and the late genotypes PI 274454, PI 274453, and L 1-1-01 expressed significant levels of antixenosis against adult D. melacanthus. These results will be useful for soybean breeding programs focusing on the stink bug resistance complex. 相似文献
609.
Termiticidal lectins from Myracrodruon urundeuva (Anacardiaceae) cause midgut damage when ingested by Nasutitermes corniger (Isoptera: Termitidae) workers 下载免费PDF全文
610.
BACKGROUND: In Brazil, dengue vector control is hampered by the resistance of Aedes aegypti L. populations to organophosphates (OPs). Insect growth regulators (IGRs) are a promising alternative, as their mechanisms of action are different from those of conventional insecticides. The authors analysed the effect of the IGR triflumuron, a chitin synthesis inhibitor, on the Ae. aegypti insecticide-susceptible strain Rockefeller, as well as on field populations both susceptible (TemS) and resistant (TemR) to the OP temephos. RESULTS: Triflumuron arrested development and inhibited adult emergence of the Rockefeller strain in a dose-dependent way (EI(50) and EI(90) of 0.8 and 1.8 microg L(-1) respectively). A direct relationship between triflumuron concentration and the precocity of its effects was evident. TemS and TemR temephos resistance ratios (RR(90)) were 4.5 and 13.8, triflumuron RR(90) being 1.0 and 1.3 respectively. CONCLUSION: The IGR triflumuron exhibited a dose-dependent effect against the reference Ae. aegypti Rockefeller strain. It was also effective against two field populations, regardless of their OP resistance status. The present results are discussed in the context of utilization of chitin synthesis inhibitors as potential alternatives in the control of Ae. aegypti in Brazil. 相似文献