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91.
The influence of landscape characteristics and home-range size on the quantification of landscape-genetics relationships 总被引:1,自引:1,他引:0
Tabitha A. Graves Tzeidle N. Wasserman Milton Cezar Ribeiro Erin L. Landguth Stephen F. Spear Niko Balkenhol Colleen B. Higgins Marie-Josée Fortin Samuel A. Cushman Lisette P. Waits 《Landscape Ecology》2012,27(2):253-266
A common approach used to estimate landscape resistance involves comparing correlations of ecological and genetic distances
calculated among individuals of a species. However, the location of sampled individuals may contain some degree of spatial
uncertainty due to the natural variation of animals moving through their home range or measurement error in plant or animal
locations. In this study, we evaluate the ways that spatial uncertainty, landscape characteristics, and genetic stochasticity
interact to influence the strength and variability of conclusions about landscape-genetics relationships. We used a neutral
landscape model to generate 45 landscapes composed of habitat and non-habitat, varying in percent habitat, aggregation, and
structural connectivity (patch cohesion). We created true and alternate locations for 500 individuals, calculated ecological
distances (least-cost paths), and simulated genetic distances among individuals. We compared correlations between ecological
distances for true and alternate locations. We then simulated genotypes at 15 neutral loci and investigated whether the same
influences could be detected in simple Mantel tests and while controlling for the effects of isolation-by-distance using the
partial Mantel test. Spatial uncertainty interacted with the percentage of habitat in the landscape, but led to only small
reductions in correlations. Furthermore, the strongest correlations occurred with low percent habitat, high aggregation, and
low to intermediate levels of cohesion. Overall genetic stochasticity was relatively low and was influenced by landscape characteristics. 相似文献
92.
Silvestre García de Jalón Paul J. Burgess Anil Graves Gerardo Moreno Jim McAdam Eric Pottier Sandra Novak Valerio Bondesan Rosa Mosquera-Losada Josep Crous-Durán Joao H. N. Palma Joana A. Paulo Tania S. Oliveira Eric Cirou Yousri Hannachi Anastasia Pantera Régis Wartelle Sonja Kay Nina Malignier Philippe Van Lerberghe Penka Tsonkova Jaconette Mirck Mercedes Rois Anne Grete Kongsted Claudine Thenail Boki Luske Staffan Berg Marie Gosme Andrea Vityi 《Agroforestry Systems》2018,92(4):829-848
Whilst the benefits of agroforestry are widely recognised in tropical latitudes few studies have assessed how agroforestry is perceived in temperate latitudes. This study evaluates how stakeholders and key actors including farmers, landowners, agricultural advisors, researchers and environmentalists perceive the implementation and expansion of agroforestry in Europe. Meetings were held with 30 stakeholder groups covering different agroforestry systems in 2014 in eleven EU countries (Denmark, France, Germany, Greece, Hungary, Italy, Netherlands, Portugal, Spain, Sweden and the United Kingdom). In total 344 valid responses were received to a questionnaire where stakeholders were asked to rank the positive and negative aspects of implementing agroforestry in their region. Improved biodiversity and wildlife habitats, animal health and welfare, and landscape aesthetics were seen as the main positive aspects of agroforestry. By contrast, increased labour, complexity of work, management costs and administrative burden were seen as the most important negative aspects. Overall, improving the environmental value of agriculture was seen as the main benefit of agroforestry, whilst management and socio-economic issues were seen as the greatest barriers. The great variability in the opportunities and barriers of the systems suggests enhanced adoption of agroforestry across Europe will be most likely to occur with specific initiatives for each type of system. 相似文献
93.
M. Rois-Díaz N. Lovric M. Lovric N. Ferreiro-Domínguez M. R. Mosquera-Losada M. den Herder A. Graves J. H. N. Palma J. A. Paulo A. Pisanelli J. Smith G. Moreno S. García A. Varga A. Pantera J. Mirck P. Burgess 《Agroforestry Systems》2018,92(4):811-828
Potential benefits and costs of agroforestry practices have been analysed by experts, but few studies have captured farmers’ perspectives on why agroforestry might be adopted on a European scale. This study provides answers to this question, through an analysis of 183 farmer interviews in 14 case study systems in eight European countries. The study systems included high natural and cultural value agroforestry systems, silvoarable systems, high value tree systems, and silvopasture systems, as well as systems where no agroforestry practices were occurring. A mixed method approach combining quantitative and qualitative approaches was taken throughout the interviews. Narrative thematic data analysis was performed. Data collection proceeded until no new themes emerged. Within a given case study, i.e. the different systems in different European regions, this sampling was performed both for farmers who practice agroforestry and farmers who did not. Results point to a great diversity of agroforestry practices, although many of the farmers are not aware of the term or concept of agroforestry, despite implementing the practice in their own farms. While only a few farmers mentioned eligibility for direct payments in the CAP as the main reason to remove trees from their land, to avoid the reduction of the funded area, the tradition in the family or the region, learning from others, and increasing the diversification of products play the most important role in adopting or not agroforestry systems. 相似文献
94.
The degree of similarity between rice milled in a McGill #2 laboratory mill and commercial milling processes was evaluated using eight physical, physicochemical, and end‐use properties. There was no statistical difference between the two milling systems with respect to color parameters L* and a*, final viscosity, texture, and end‐use cooking properties (α = 0.05). Overall, the kernel dimensions of length, width, and thickness were less in the McGill #2 laboratory‐milled rice than the same rice milled commercially. The incidence of bran streaks and peak viscosity values were each higher when the rice sample was milled commercially in 27, and 28, respectively, of the 29 samples by means comparison. The decrease in kernel dimensions and incidence of bran streaks were attributed to the more aggressive nature of the single‐pass, batch milling system of the McGill #2 laboratory mill as compared with multipass, continuous milling systems that are used commercially. Finally, as surface lipid content (SLC) decreased, L* increased and a*, b*, and the incidence of bran streaks decreased for both milling systems. 相似文献
95.
The oral and intravenous disposition of the anti-thyroid drug propylthiouracil (PTU) was determined in six clinically healthy cats and four cats with naturally occurring hyperthyroidism. Compared with the normal cats, the mean plasma elimination half-life of PTU was significantly (P less than 0.001) shorter in the hyperthyroid cats (77.5 +/- 5.8 minutes compared with 125.5 +/- 3.7 minutes) and the total body clearance of PTU was significantly (P less than 0.05) more rapid in the cats with hyperthyroidism (5.1 +/- 0.8 ml kg-1 min-1 compared with 2.7 +/- 0.2 ml kg-1 min-1). Following oral administration, both the bioavailability (59.7 +/- 4.9 per cent compared with 73.3 +/- 3.7 per cent) and peak plasma concentrations (14.5 +/- 1.6 micrograms ml-1 compared with 18.9 +/- 0.9 micrograms ml-1) of PTU were significantly (P less than 0.05) lower in the hyperthyroid cats than in the control cats. No difference was noted, however, between the apparent volume of distribution for PTU in the two groups of cats. Overall, results of this study indicate that the oral bioavailability of PTU is decreased and PTU disposition is accelerated in cats with hyperthyroidism. 相似文献
96.
97.
A Holstein fetus was delivered by Caesarean section at a gestational age of 441 days. The pituitary pars distalis was aplastic and the adrenal and thyroid glands were severely hypoplastic. Arrested or retarded cartilage cell maturation resulted in absence or minimal development of epiphyseal ossification centers, delayed ossification of carpal bones, and arrest of longitudinal growth of bones. The pathophysiology of prolonged gestation and of skeletal pathology is discussed. 相似文献
98.
S. B. Ekanem James W. Avault Jerry B. Graves H. Morris 《Journal of the World Aquaculture Society》1981,12(2):373-383
In laboratory studies, acute toxicity tests (96-hour) showed strong main effect on crawfish when Propanil, Ordram, and Furadan were combined; this combination was the most toxic treatment to crawfish. Furthermore, a strong interaction among the three suggests a non-additive response. Ordram alone was the least toxic pesticide. Additive effect was observed when Furadan was combined with Ordram or Propanil, but antagonism was detected in the combination of Propanil with Ordram. Concentrations higher than the recommended rate for use at normal conditions had a significant (P<0.05) lethal effect on crawfish. Soil moderated the toxicity of some pesticides and their combinations. 相似文献
99.
Donald L Evans Scott S Graves Vicki S Blazer Donald L Dawe John B Gratzek 《Comparative immunology, microbiology and infectious diseases》1984,7(2):91-100
Nonspecific cytotoxic cells (NCC) from fish (Ictalurus punctatus) were treated with different concentrations of retinolacetate and poly I:C. Both in vitro and in vivo experiments were conducted. Retinolacetate significantly increased NCC activity against chromium-51 labeled human B-cell lymphoma target cells (NC-37). Preincubation (treatment prior to adding the labeled target cells) of NCC for 4 to 8 h in 10?3 to 10?12 M concentration of retinolacetate produced significant increases in NCC activity compared to treatment during the killing assay only. Similar experiments with different concentrations of poly I:C had no NCC augmenting effects when tested by adding poly I:C either during preincubation periods or during the cytotoxicity assay. Retinolacetate probably produces positive modulation of cytotoxicity by increasing the killing effectiveness of individual NCC, rather than recruiting larger numbers of cytolytic cells. In vivo studies were also conducted by injecting catfish (i.p.) with 1 ×, 3 × and 5 × the daily recommended vitamin A dosages and determining NCC activity after 24, 48 and 72 h treatment. The 1 × dose significantly increased NCC activity at 72 h. This increase was not transient because NCC activity after 33–37 days' treatment was significantly higher than controls in the 1 ×, 2 × and 3 × groups. Intraperitoneal injections of fish with poly I:C produced no significant increases in NCC activity at 24 or 72 h post-inoculation. 相似文献
100.
Episodes of hemolysis and leukocytosis which were associated with Babesia bigemina followed each of 3 challenge exposures to influenza A viruses. It is possible that viral infection altered the immunologic host-parasite equilibrium. Acute thrombocytopenia and rouleaux formation were also observed. Death, attributed to liver flukes, occurred 168 days after the yak was transferred from high to low altitude. A 2nd yak died of foot-and-mouth disease, thus supporting the Nepali belief that yaks will not survive at the lower altitudes of Kathmandu. 相似文献