全文获取类型
收费全文 | 280篇 |
免费 | 19篇 |
专业分类
林业 | 36篇 |
农学 | 19篇 |
基础科学 | 7篇 |
51篇 | |
综合类 | 12篇 |
农作物 | 25篇 |
水产渔业 | 18篇 |
畜牧兽医 | 91篇 |
园艺 | 10篇 |
植物保护 | 30篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 13篇 |
2018年 | 10篇 |
2017年 | 17篇 |
2016年 | 11篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 24篇 |
2011年 | 23篇 |
2010年 | 13篇 |
2009年 | 13篇 |
2008年 | 13篇 |
2007年 | 13篇 |
2006年 | 20篇 |
2005年 | 8篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1986年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有299条查询结果,搜索用时 31 毫秒
71.
Reference limits for biochemical and hematological analytes of dairy cows one week before and one week after parturition
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Gerardo F. Quiroz-Rocha Stephen J. LeBlanc Todd F. Duffield Darren Wood Ken E. Leslie Robert M. Jacobs 《The Canadian veterinary journal. La revue veterinaire canadienne》2009,50(4):383-388
Since dairy cows during the transition period have multiple endocrine and metabolic changes, it is necessary to determine the reference limits of laboratory analytes in normal transition cows. Reference limits for the weeks before and after calving were determined in dairy cows. Animals that had adverse clinical outcomes after calving and cows that were culled or had mastitis within the first 7 days after calving were excluded. All biochemical analytes (β-hydroxybutyrate, fatty acids, glucose, cholesterol, urea, calcium, and phosphorus) were statistically different between precalving and postcalving groups. The hematological analytes were not significantly different except for eosinophils. The data from precalving and postcalving cows were significantly different from reference limits in a university-associated laboratory derived from early- and mid-lactation cows. Different reference limits for precalving and postcalving dairy cows should be determined for biochemical analytes to ensure appropriate interpretation of results. 相似文献
72.
Jimenez-Sanchez G 《Science (New York, N.Y.)》2003,300(5617):295-296
Mexico is preparing to develop a genomic medicine program focused on national health problems. Modern Mexicans result from an admixture of more than 65 native Indian groups with Spaniards, leading to a unique genetic makeup and a characteristic set of disease susceptibilities. Since 1999, more than 100 experts from different fields have joined efforts with government, academia, and industry to identify priorities and goals for genomic medicine in Mexico. The plan includes establishment of an Institute of Genomic Medicine with strong intramural and extramural programs. This project is expected to ease the social and financial burden of health problems in Mexico. 相似文献
73.
Whole-tree water balance and indicators for short-term drought stress in non-bearing ‘Barnea’ olives
Alon Ben-Gal Dilia Kool Gerardo E. van Halsema Ariel Yafe Ran Erel Isaac Zipori Simon Rüger Yafit Cohen Arnon Dag 《Agricultural Water Management》2010,98(1):124-133
Drainage-weighing lysimeters allowed monitoring of water balance components of non-bearing olive (Olea europaea cv Barnea) trees over a 3-month period including short-term events of controlled but severe water stress. The objective of the study was to evaluate a variety of soil and plant-based water status and drought stress monitoring methods on the basis of tree-scale evapotranspiration (ET). As the trees entered into and recovered from water stress, meteorological data, actual ET (ETa), soil water content and changes in leaf turgor pressure were continuously monitored. Additionally, midday measurements of stem water potential, stomatal conductance, canopy temperature, and quantum yield of PSII photochemistry were conducted. Diurnal (dawn to dusk) measurements of all the above were made hourly on days of maximum stress. Shoot elongation rate was measured for periods of stress and recovery. Quantum yield of PSII photochemistry, stomatal conductance, and stem water potential all successfully indicated reductions in whole-tree water consumption beginning at moderate stress levels. These measured parameters fully recovered to the levels of non-stressed trees soon after water application was renewed. Shoot elongation was reduced 25-30% for the 10-day period during and following drought and recovered thereafter to levels of non-stressed trees. Whole-tree ETa was reduced by as much as 20% even following full recovery of the leaf level parameters, suggesting reduced canopy size and growth due to the stress period. Non-destructive, continuous (turgor pressure) and remotely sensed (canopy temperature) methods showed promising potential for monitoring effects of water stress, in spite of technological and data interpretation challenges requiring further attention. 相似文献
74.
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
75.
AbstractSpatial distributions models (SDM) are often used in invasive pest management to understand current and potential distribution. Using data on the well-studied spotted wing drosophila as a model, we compared distribution patterns of the range-limit with commonly applied correlative and mechanistic models. Correlative models risk underestimation whereas simple mechanistic models provide overestimated range predictions, although using both approaches for the spotted wing drosophila improved range-limit predictions. Model choice when dealing with pests is central to the accurate identification of invasive species limit range and consequently for the deployment of monitoring and early detection programs. 相似文献
76.
Predicting the distribution of harmful species and their natural enemies in agricultural,livestock and forestry systems: an overview 总被引:1,自引:0,他引:1
AbstractPredicting the potential distribution of harmful species to agriculture, livestock and forestry is decisive to prevent their impacts, especially when these are expanding their range due to global change. Recent advances in species distribution modelling (SDM) have made these tools widely used for biosecurity studies. We reviewed the available literature of SDM for pest, weeds, pathogen species and biological-control agents, with the aims of synthesizing and quantifying the available information, and identifying gaps in the knowledge and future perspectives. SDMs for 420 species were collected from 220 publications. Insect pests were the most frequently studied organisms. CLIMEX and MaxEnt were the most commonly used modelling tools, while pure mechanistic approaches were rarely applied. Most studies covered broad scales, and focused on predicting the distribution of invasive species and/or the effects of climate change. The challenge remains for models to include disturbance, resource availability, and biotic factors, as well as to better quantify uncertainty. This future directions will be fundamental to improve the predictive power of SDMs for productive systems in the context of a rapidly changing World. 相似文献
77.
Metabolic responses to water deficit in two Eucalyptus globulus clones with contrasting drought sensitivity 总被引:2,自引:0,他引:2
Shvaleva AL Costa E Silva F Breia E Jouve J Hausman JF Almeida MH Maroco JP Rodrigues ML Pereira JS Chaves MM 《Tree physiology》2006,26(2):239-248
We compared the metabolic responses of leaves and roots of two Eucalyptus globulus Labill. clones differing in drought sensitivity to a slowly imposed water deficit. Responses measured included changes in concentrations of soluble and insoluble sugars, proline, total protein and several antioxidant enzymes. In addition to the general decrease in growth caused by water deficit, we observed a decrease in osmotic potential when drought stress became severe. In both clones, the decrease was greater in roots than in leaves, consistent with the observed increases in concentrations of soluble sugars and proline in these organs. In roots of both clones, glutathione reductase activity increased significantly in response to water deficit, suggesting that this enzyme plays a protective role in roots during drought stress by catalyzing the catabolism of reactive oxygen species. Clone CN5 has stress avoidance mechanisms that account for its lower sensitivity to drought compared with Clone ST51. 相似文献
78.
B. Chaves S. De Neve L. M. Piulats P. Boeckx O. Van Cleemput & G. Hofman 《Soil Use and Management》2007,23(2):212-219
The potential to manipulate the N release from vegetable crop residues (cauliflower, leek) by using organic wastes was tested under field conditions on three soil textures during 2 years (silt loam, sandy loam and loamy sand). During the first year, incorporation of green waste compost and sawdust did not significantly increase microbial biomass N and did not lead to a significant N immobilization of crop residue‐N. During the second year, straw did increase microbial biomass N and showed a good N immobilization potential in all textures. The largest increase in microbial biomass N and the greatest N immobilization occurred in the loamy sand soil. The texture effect was probably because of better incorporation of the crop residues and immobilizer wastes in the loamy sand soil compared with the other textures. During spring, there was no consistent remineralization of immobilized N after the addition of malting sludge or vinasses in either year. This could be a result of the limited amount of N immobilized and available for remineralization in the first year or an unsuitable composition of the remineralizer wastes. 相似文献
79.
Juana Ortiz Rocío Ruiz de Ybá?ez Teresa Abaigar Marina Goyena Magdalena Garijo Gerardo Espeso Mar Cano 《Journal of zoo and wildlife medicine》2006,37(3):249-254
Feces from 62 captive African gazelles, including Mhorr gazelles (Gazella dama mhorr), Cuvier's gazelles (Gazella cuvieri), and Dorcas gazelles (Gazella dorcas neglecta), were examined over the course of a year to quantitate nematode egg excretion patterns. Strongyloides sp. eggs appeared only in G. dama during the rainy season. Trichostrongylidae egg excretion showed a marked seasonal variation, with very low levels during the dry and hot period, a finding that is probably attributable to hypobiosis of the predominant species (Camelostrongylus mentulatus). Eggs of the Nematodirus sp., predominantly Nematodirus spathiger, were excreted throughout the year. No seasonal pattern was observed in Trichuris sp. egg excretion. 相似文献
80.
Water-use strategies in two co-occurring Mediterranean evergreen oaks: surviving the summer drought 总被引:1,自引:0,他引:1
David TS Henriques MO Kurz-Besson C Nunes J Valente F Vaz M Pereira JS Siegwolf R Chaves MM Gazarini LC David JS 《Tree physiology》2007,27(6):793-803
In the Mediterranean evergreen oak woodlands of southern Portugal, the main tree species are Quercus ilex ssp. rotundifolia Lam. (holm oak) and Quercus suber L. (cork oak). We studied a savannah-type woodland where these species coexist, with the aim of better understanding the mechanisms of tree adaptation to seasonal drought. In both species, seasonal variations in transpiration and predawn leaf water potential showed a maximum in spring followed by a decline through the rainless summer and a recovery with autumn rainfall. Although the observed decrease in predawn leaf water potential in summer indicates soil water depletion, trees maintained transpiration rates above 0.7 mm day(-1) during the summer drought. By that time, more than 70% of the transpired water was being taken from groundwater sources. The daily fluctuations in soil water content suggest that some root uptake of groundwater was mediated through the upper soil layers by hydraulic lift. During the dry season, Q. ilex maintained higher predawn leaf water potentials, canopy conductances and transpiration rates than Q. suber. The higher water status of Q. ilex was likely associated with their deeper root systems compared with Q. suber. Whole-tree hydraulic conductance and minimum midday leaf water potential were lower in Q. ilex, indicating that Q. ilex was more tolerant to drought than Q. suber. Overall, Q. ilex seemed to have more effective drought avoidance and drought tolerance mechanisms than Q. suber. 相似文献