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1.
This work presents evidence from three different valuation studieson the influence of gender in the formation of forestry-relatedvalues. Previous studies examined gender differences withoutexplicitly considering their interaction with other explanatoryvariables. Three separate studies dealing with forest-relatedgoods and services, revealed statistically significant differencesin peoples' preferences, especially between older women andolder men, and older and younger women. In these studies, althoughthere was no overall difference in preferences attributableto gender, there were significant differences related to ageand income, in combination with gender.  相似文献   
2.
  • ? Woody encroachment into grasslands is a worldwide phenomenon. In the Pyrenees, fire has been used as a management tool to transform part of the encroached land to grassland.
  • ? This study aims to compare the spatial patterns of shrub cover 4 y after 4 different fire disturbances (prescribed burning, repeated prescribed burning, wildfire in 20 year-old shrubs and wildfire in 5 year-old shrubs); and also to compare shrub cover after different fire disturbances, accounting for spatial autocorrelation. The study focuses on the shrub Cytisus balansae. Two-dimensional transects (20 × 0.5 m) were established to monitor shrub cover for 4 y after each disturbance type. Autoregressive models and Markov models were used with a Monte Carlo procedure to account for the presence of spatial autocorrelation.
  • ? Shrub cover was greater after prescribed burning than after repeated prescribed burning, and it increased with shrub age before disturbance. Differences in spatial patterns were detected in shrub patch size, with repeated prescribed fires and wildfires reducing shrub patch size by half in comparison with prescribed burning.
  • ? From the management point of view, the effects of repeated prescribed burning were similar to those of a wildfire on reducing shrub cover and shrub patch size.
  •   相似文献   
    3.
    尚德库 《林业研究》1997,8(1):54-58
    lNTRoDUCTIONTheon-sitcnon-dcstructit'cmcasurcl11cntofu.oodmoisbocontcntattTactsgrcatintcrcsts.Itpla3'simpor-tantpartsinthescicntificrcscarchsucl1asonthchcatandmasstransportproccssesint"ooddri'ing.thcim-pregnationofliquidinxt'ood.thcmoisturccontcntdistri-b…  相似文献   
    4.
    Stemphylium vesicarium, the causal agent of brown spot of pear, overwinters in the leaf residues of pear and herbaceous plants of the orchard floor. Pseudothecia of the teleomorph, Pleospora allii, are formed on these residues where they produce ascospores. New methods were tested aimed at reducing this overwintering inoculum and increasing the efficacy of control of brown spot of pear. Sanitation methods were evaluated in nine trials in Girona (Spain) and Ferrara (Italy) over a 4-year period. The sanitation methods were leaf litter removal in December to February, and application of biological control agents (commercial formulates of Trichoderma spp.) to the orchard ground cover from February to May. Fungicides were also applied to the trees during the pear-growing season, scheduled according to the BSPcast model. The different methods were tested as stand-alone applications or in combination. All methods consistently reduced the disease incidence at harvest on fruit with an efficacy between 30 to 60% for leaf litter removal and more than 60% for the combination of leaf litter removal and biological control. Efficacy of sanitation alone (leaf litter removal and biological control) in reducing the brown spot level on fruit was similar in most of the trials to the efficacy obtained when fungicides were applied alone. However, integration of sanitation methods and fungicides did not improve the efficacy of disease control over the level provided by fungicides alone.  相似文献   
    5.
    6.
    Fumigation of field soil with chloropicrin alone or followed by methyl bromide, each at 220Kg·ha?1, released 20–30 parts/106 NH+4-N which persisted for 75 days; such fumigation also doubled the amount of bicarbonate-extractable phosphate 28 days after fumigation. Soil fumigation increased both the vegetative and grain yields as well as increasing the content of N in the grain and the content of K and Cl in the tops at ear emergence. Root growth and the phosphate uptake activity of the roots were increased by soil fumigation.  相似文献   
    7.
    Runner hyphae of Gaeumannomyces graminis (Sacc.) Arx & Olivier var. tritici Walker on seminal roots of wheat seedlings were photographed and their length measured. As well, their length was estimated using the line-intercept method. The correlation of 0.904 between measured and estimated lengths of hyphae was highly significant. This line intercept method was used to estimate the density (length/unit area) of hyphae on roots of plants growing in the presence and absence of a soil suppressive to G. graminis var. tritici. Estimations were made eight times during 28 days growth at 15°C. In fumigated soil (non-suppressive) inoculated with 0.1% ground oat grain infested with G. graminis var. tritici, the density of hyphae on roots started to increase at five days compared with 15 days when soil there was a 10.8% cover of the root surface after 15 days when the hyphae had reached maximum density. Suppression to G. graminis var. tritici is normally detected by a difference in disease rating of roots at 28 days but this study has shown that suppression can be demonstrated by the difference in the density of hyphae if roots are examined between seven and 19 days.  相似文献   
    8.
    Accumulation of soil carbon is mainly controlled by the balance between litter production and litter decomposition. Usually In Mediterranean forests there are contrasting conditions in the distribution of faunal activity and the moss layer that may have different effects on litter decomposition. Decomposition and faunal activity were studied by exposing litter of contrasting quality (Pinus halepensis Mill. and Quercus ilex L.) for 3.5 yr in three Mediterranean pine forests of the eastern Iberian Peninsula. The effects of mosses on decomposition and on faunal activity were studied by exposing P. halepensis litter either on moss patches or directly on the forest floor. Faecal pellet production was used as an indication of faunal activity. Water availability or soil characteristics seem to limit faunal activities in the drier sites. Faecal pellets were not found during the first stages of decomposition and in all sites they appeared when about a 30% of the initial litter had decomposed. Under wet conditions faecal pellet production was very high and a mass balance suggested that soil faunal activity may result in a net flow of organic matter from the lower organic horizons to the surface Oi horizon. Mosses slightly increased mass loss of pine litter probably as a consequence of high potentially mineralizable nitrogen in the Oa horizon of moss patches and also, perhaps, as a consequence of the higher moisture content measured in the Oi horizon needles sampled among the mosses. In contrast, moss patches reduced faunal activity. The effect of litter quality on mass loss was not always significant, suggesting an interaction between litter quality and site conditions. During the first stages of decomposition there was N immobilisation in P. halepensis litter (poorer in N) and N release from Q. ilex litter (richer in N). In conclusion, in these forests soil microclimate and/or N availability appear to be more important controlling litter decomposition than the distribution of faunal activity.  相似文献   
    9.
    The use of 14C-labelling of plants in short-term studies has established that the major zone of release of carbon-containing materials from roots is the zone of elongation. Much of this material is in an insoluble form, comprising sloughed-off root cap cells and polysaccharide material, and remains in the immediate vicinity of the root. Electron microscopy of ultra-thin sections of the root-soil interface of wheat plants has shown that colonisation by micro-organisms of the rhizosphere is relatively sparse in the young parts of roots. In the older parts of roots, evidence was obtained that bacteria lyse the walls of the outer root cells and this is followed by dense colonisation of these moribund outer cells by bacteria.  相似文献   
    10.
    Of 33 Escherichia coli strains isolated from canine urinary tract infections, 22 were haemolytic and 27 were classified into O serogroups, the most common being O4, O6, O2 and O83. P-fimbriated strains were haemolytic and belonged mainly to serogroups O4 and O6. Twenty-nine strains possessed type-1 fimbriae but only small numbers possessed S fimbriae, type-1C fimbriae, X adhesins or the aerobactin system. It is postulated that P fimbriae and haemolysin production contribute to bacterial virulence in canine pyelonephritis and cystitis.  相似文献   
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