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81.
Landaeta-Hernández Antonio J. Ungerfeld Rodolfo Randles Ronald Littell Ramon Rae D. Owen Chenoweth Peter J. 《Tropical animal health and production》2020,52(2):743-751
Tropical Animal Health and Production - The objective of this study was to assess aspects of the social behavior of a mixed-breed herd of beef cows as a potential source for stress and economic... 相似文献
82.
A Review of Combine Sensors for Precision Farming 总被引:9,自引:0,他引:9
To maximize economic return from agricultural production units, costs have to be minimized and benefits maximized. For grain, kernel yield and quality have to be maximized while the use of seeds, fertilizer, herbicides and fungicides have to be optimized.The best location to evaluate productivity levels, by measuring yield and quality of grain and straw, is the combine harvester. Moreover, other grain quality characteristics like density or test weight can be determined for use as an evaluation tool. In this paper, an overview is given of the past and current research toward the evaluation of currently available commercial sensors (e.g., for measuring grain yield and grain moisture content) as well as toward the development of new sensors (e.g., grain protein content and straw yield). 相似文献
83.
Jose Ramon Gonzalez-Olabarria Blas Mola-Yudego Timo Pukkala Marc Palahi 《Annals of Forest Science》2011,68(4):861-871
Introduction
This article explores the possibility of including multiple spatial scales into a mixed model for predicting the density of human-caused fire ignitions in Catalonia (North-East Spain). 相似文献84.
José?Ramon?Rodríguez-Pérez Richard?E.?Plant Jean-Jacques?Lambert David?R.?SmartEmail author 《Precision Agriculture》2011,12(6):775-794
The adoption of precision viticulture requires a detailed knowledge of variation in soil chemical, physical and profile properties.
This study evaluates the usefulness of apparent electrical conductivity (ECa) data within a GIS framework to identify variations in soil chemical and physical properties and moisture content. The work
was conducted in a vineyard located in the Carneros Region (Napa Valley, California). The soil was sampled using 44 boreholes
to quantify chemical and physical characteristics and 9 open pits to verify the borehole observations. Moisture content was
determined using time domain reflectometry (TDR). To characterize soil ECa, three campaigns were undertaken using a soil electrical conductivity meter (EM38). Linear regressions between soil ECa and soil properties were determined. Boreholes and TDR data were interpolated by kriging to characterize the spatial distribution
of soil variables. The resulting maps were compared to the results obtained using the best ECa linear regressions. Using ECa measurements, soil properties like extractable Na+ and Mg2+, clay and sand content were well estimated, while best estimates were obtained for extractable Na+ (r
2
= 0.770) and clay content (r
2
= 0.621). The best estimates for soil moisture content corresponded to moisture in the deeper soil horizons (r
2
= 0.449). The methods described above provided maps of soil properties estimated by ECa in a GIS framework, and could save time and resources during vineyard establishment and management. 相似文献
85.
Francesc Rubio-Gracia Emili García-Berthou Dani Latorre Ramon Moreno-Amich Pao Srean Yiping Luo Anna Vila-Gispert 《Ecology of Freshwater Fish》2020,29(2):230-240
Swimming performance is a key feature that mediates fitness and survival in many fish species. Using a swim tunnel respirometer, we compared prolonged swimming performance and energy use for two competing species: an endangered, endemic toothcarp (Aphanius iberus) and a worldwide invasive mosquitofish (Gambusia holbrooki). Critical (Ucrit) and optimal swimming speeds, standard and maximal metabolic rates, absolute aerobic scope, as well as the minimum cost of transport were estimated and compared between species and sexes. Body streamlining and caudal peduncle depth were also measured to explain the differences in swimming performance and efficiency. Both sexes of A. iberus presented similar swimming capacity and metabolic traits, whereas males of G. holbrooki showed higher critical swimming speeds, maximal metabolic rate and absolute aerobic scope than females. We also found marked differences between species in most of the response variables examined. Aphanius iberus showed lower swimming capacity (Ucrit mean <10 cm s−1), higher maximal metabolic rate and absolute aerobic scope than the invasive species. By contrast, G holbrooki swam faster and had lower cost of transport at a given fish mass and speed, thereby leading to a higher swimming efficiency. The observed differences in swimming efficiency were closely related to differences in morphological characteristics and therefore to drag pressures and propulsion. Our results add a mechanistic basis to the ecological understanding of these two species and suggest that although both are poor swimmers compared to many other similarly sized species, the native species likely has more restricted water flow tolerance and dispersal capacities. 相似文献
86.
Frederick W. Cubbage Robert R. Davis Diana Rodríguez Paredes Ramon Mollenhauer Yoanna Kraus Elsin Gregory E. Frey 《Journal of Sustainable Forestry》2015,34(6-7):623-650
Community-based forest management, such as Community Forest Enterprises (CFEs), has the potential to generate positive socioenvironmental and economic outcomes. We performed a detailed survey of financial and production parameters for 30 of the approximately 992 CFEs in Mexico in order to estimate costs, income, profits, and sustainability of harvest levels for forest management, harvest, and sawmilling. Fourteen of the 30 CFEs harvested more timber than they grew in 2011, suggesting issues with sustainability, but only two of these had harvest far above annual growth, and five of those were only a fraction more than annual growth. All of the 30 CFEs except one made profits in forest management and timber growing. For timber harvesting, 22 of 30 CFEs made profits, but the losses were small for the other CFEs. For the 23 CFEs with sawmills, 18 made profits and five had losses; the greatest returns for the CFEs accrued to those with sawmills for lumber production. On average, the CFEs surveyed had high costs of production relative to other countries, but the CFEs were still profitable in national lumber markets. If Mexico were to begin importing large amounts of lumber from lower cost countries, this could pose a threat to CFE profitability. 相似文献
87.
Aragon Glauca Torres Ovalle Alvaro Ramon Coelho Carmouze Jean‐pierre 《Mangroves and Salt Marshes》1999,3(2):85-93
Porewater dynamics and the formation of iron sulfides were studied in the Brazilian mangrove. Porewater samples were collected during tidal cycles using in situ equipment and physical–chemical and chemical data were obtained. The advective transport of porewater by tidal currents was found to be more effective between 0 and 5cm depth than below 15cm. The diffusive input of atmospheric oxygen during low tides resulted in oxidation of porewater dissolved sulfides. Thermodynamic considerations identified pyrite as the main iron sulfide forming at this depth, and the amorphous iron hydroxides are probably the main iron source. Below 15cm depth, irregular root distribution underground and benthic faunal bioturbation caused considerable spatial variation in a small scale (20cm). The correlation between alkalinity and total dissolved sulfide suggests that the main pathway for organic matter decomposition is sulfate reduction. Formed in the highly sulfidic diagenetic zone, the dissolved iron went through iron sulfide formation process. Crystalline iron oxides like hematite and magnetite may constitute an important iron source below 15cm, whereas pyrite is still the most probably occurring iron sulfide, according to thermodynamic considerations. 相似文献
88.
Cristina Buendia Ramon J. Batalla Sergi Sabater Antoni Palau Rafael Marc 《Land Degradation \u0026amp; Development》2016,27(3):823-838
The abandonment of traditional rural life in mountain areas has favoured the expansion of forest in the headwaters of Pyrenean rivers. In this paper, we (i) analyse hydro‐climatic trends at the annual and monthly scales in three nested sub‐catchments in a central Pyrenean basin and (ii) quantify the relative contribution of climate change and forest cover on the observed changes in runoff. Land use maps indicate an increase in the forest cover in all sub‐basins for the period 1987–2009. Non‐parametric Mann–Kendall statistic on annual and monthly hydro‐climatic data from 1965 to 2009 was used to identify trends in climate and runoff data. To assess the potential influence of the period length, trends were also examined for the 1941–2009 stretch. Upward trends were detected for temperature and potential evapotranspiration, particularly during summer and winter months. Precipitation trends and their significance depended on the length of the period considered, although overall results indicated a decrease, particularly for February and July. The effects of climate change and land cover change on annual runoff were identified by means of a change point analysis. Results indicated that a change in annual runoff took place in the 1980s, suggesting the non‐linearity in the relationship between precipitation and runoff, and thus the influence of land use factors. The influence of forest cover was confirmed by comparing observed runoff trends with those resulting from a hydro‐climatic model that does not take into account land use changes. Divergence between both trends revealed that forest cover can account for ~40% of the observed decrease in annual runoff. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
89.
Pier Paolo Gatta Luca Parma Ilaria Guarniero Luciana Mandrioli Rubina Sirri Ramon Fontanillas Alessio Bonaldo 《Aquaculture Research》2011,42(3):313-321
This study was undertaken to determine the influence of dietary protein levels on growth, feed utilization and liver histology in common sole. Four isoenergetic diets were formulated to contain four different crude protein levels: 39 (P39), 45 (P45), 51 (P51) and 57 (P57) % dry weight. Fifty animals per tank (initial weight 10.2 ± 0.4 g) were randomly distributed into twelve 500 litre square tanks (bottom surface: 5600 cm2) connected to a closed recirculation system. The diets were tested in triplicate for 84 days. At the end of the experiment, the final weight ranged from 19.6 (P39) to 25.4 g (P57). The specific growth rate showed statistical differences between groups, with the best results in the group fed diet P57 (1.07% day?1). Significant differences between groups were also recorded for the feed conversion ratio, with values of 1.31, 1.28, 1.12 and 0.94 in P39, P45, P51 and P57 respectively. Gross lipid efficiency was also significantly affected by the dietary treatment, with the highest value (42.07%) found in P57. Ammonia excretion, expressed as g 100 g?1 protein intake, was significantly lower for group P39 (2.46) than groups P51 (4.70) and P57 (4.75). Increased incidence of lipid droplets in hepatocytes was observed when the dietary protein levels increased and/or dietary lipid decreased. 相似文献
90.
Hervé Jactel Bruce C. Nicoll Manuela Branco José Ramon Gonzalez-Olabarria Wojciech Grodzki Bo Långström Francisco Moreira Sigrid Netherer Christophe Orazio Dominique Piou Helena Santos Mart Jan Schelhaas Karl Tojic Floor Vodde 《Annals of Forest Science》2009,66(7):701-701