首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   36篇
  免费   0篇
林业   10篇
  9篇
综合类   1篇
农作物   2篇
畜牧兽医   13篇
园艺   1篇
  2019年   1篇
  2018年   1篇
  2013年   3篇
  2012年   1篇
  2011年   2篇
  2010年   2篇
  2009年   6篇
  2008年   1篇
  2007年   4篇
  2005年   1篇
  2003年   3篇
  2002年   2篇
  2001年   1篇
  1991年   1篇
  1989年   2篇
  1987年   2篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
排序方式: 共有36条查询结果,搜索用时 31 毫秒
11.
In Finland grain has during some years contained considerable amounts of mycotoxins depending on the weather conditions, harvesting and preservation methods. The most common of these mycotoxins are Fusariumtoxins: zearalenone and trichotechenes. The trichotechene group is large, but only a few of the toxins are of practical interest in that they cause health disorders to farm animals. The most common toxin of the trichotechenes is deoksinivalenol or vomitoxin (DON), which causes, especially in pigs, vomiting and reduction in feed palatability.  相似文献   
12.
In earlier experiments regarding the effects of preservative "Gasol" (containing various acids and additional compounds and intended for whole grain preservations) in recommended dosages, prevents the growth of Fusarium graminearum and reduces the amount of zearalenone when added to milled grain. It was proved in the tests carried out that the smaller dosages of "Gasol" were sufficient for the prevention of growth of the fungus and reduction in quantity of zearalenone. The degree to which the toxin was destroyed depended on the dosage of the preservation. A dosage twice as strong as that recommended in the instructions for practice destroyed all the toxin formed in the grain. A very small dosage of "Gasol" (1/8 of recommended dosage) prevented the growth of the fungus and only slightly reduced the amount of toxin only at the beginning of the test. Later, the growth of the fungus was more vigorous and significantly more toxin was present in the treated grain than in the grain which had never been treated with the preservatives, it has been proved that the preservative  相似文献   
13.
Tap‐rooted rapeseed is generally considered sensitive to soil compaction. We examined 473 Finnish rapeseed fields sown in 2007 to 2009 to both spring turnip rape Brassica rapa L. (dominant crop) and oilseed rape Brassica napus L. Roots were rated late in the growing season according to penetration capacity. Roots in each field were rated from G1 (no problems with root penetration) to G5 (failure to penetrate deeper soil layers). There were significant effects of year, crop species, soil type, special soil properties and soil cultivation methods on frequency of G1 and G4+5 roots. Restricted root penetration was a common phenomenon. Typically, fields had <30% G3 and G4+5 roots, however, some fields had >70% G4+5 roots and were cases for serious concern. Yield loss was linearly related to the incidence of G4+5 plants in 2007, but there was no relationship with the other years. Oilseed rape had a greater proportion of G4+5 roots than turnip rape and twice the proportion of G4+5 roots occurred in direct‐drilled fields than in reduced or fully tilled fields. Rapeseed yield decline may at least partly be related to poor root penetration and it is a useful indicator crop to demonstrate the degree of soil compaction and should be cultivated in fields where sufficient root penetration is possible.  相似文献   
14.
This study examined non-genetic effects and genetic parameters of body measures and subjectively scored traits in the Finnhorse trotter population. The data was based on studbook inspections from 1971 to 2004 covering observations on 6381 horses. There were five body measures – height at withers, height at croup, circumference of girth, length of body and circumference of cannon bone – and six subjectively scored traits – character, body conformation, leg stances, quality of legs, hooves and movements – included in the analyses. Multivariate mixed models were applied with year–sex and age as fixed effects and animal as a random effect. The year–sex effect had a significant influence on body measures and scored traits. Age at judging had a significant influence on all traits but height at withers and body conformation. Heritability estimates were from 0.53 to 0.78 for body measures and 0.10 to 0.19 for scored traits. Genetic correlations between body measures were highly positive, from 0.75 to 0.98, whilst genetic correlations between scored traits varied between − 0.20 and 0.51. Genetic correlations between body measures and scored traits were mainly negative, from − 0.38 to 0.09. Our results indicate that additive genetic effects are relevant determinants for body measures of Finnhorse trotters. The scored traits were of low to moderate heritability and were relevantly influenced by environmental effects.  相似文献   
15.
Many freshwater ecosystems face severe threats from anthropogenic disturbances, yet little is known about the degree to which their biotic communities have been degraded by human activities. We analysed temporal changes and persistence of bryophyte communities in 40 springs in eastern Finland by comparing field surveys conducted in 1986 and 2000. During that period, some springs had remained in a near-pristine state, while others had undergone varying degrees of disturbance from forest management, drainage, and water abstraction. Several spring bryophytes (e.g., Philonotis fontana) declined between the study years, whereas Sphagnum mosses (e.g., Sphagnum warnstorfii) increased in abundance. Species richness of spring bryophytes declined significantly from 1986 to 2000, irrespective of bryophyte group (spring vs. other bryophytes) and spring condition (severely disturbed vs. unaltered springs). Bryophyte cover also decreased dramatically from 1986 to 2000, but this effect was related to both spring condition and bryophyte type. Spring bryophytes lost much of their cover in severely altered springs, while in unaltered springs they remained relatively stable through time. No such trend was observed for other, habitat generalist bryophytes. Persistence and stability of bryophyte communities showed significant, albeit rather weak, relationships with spring condition, with communities in unaltered springs being more persistent than those in altered springs. Given the importance of springs to boreal forest and aquatic biodiversity, restoration of degraded springs is a major challenge to maintaining and conserving biodiversity of boreal landscapes.  相似文献   
16.
The decomposition of organic matter of source-separated biowaste during composting was followed during 18 months. Compost samples were fractionated into three parts: (i) hot water soluble extract (HWE) (ii) bitumen fraction and (iii) humic substances (humic acids (HA) and fulvic acids (FA)). Original compost samples and the HA and FA fractions were hydrolyzed with sulfuric acid for hexoses and pentoses. Quantitative spectrophotometric and qualitative GC/MS analyses of monosaccharides as trimethylsilyl ethers of the corresponding alditols were carried out.

During composting, the amount of HA in the organic matter of the compost increased, the amounts of HWE and bitumen decreased and the amount of the FA fraction changed only a little. Carbohydrates were found to be important constituents of biowaste composts and their HA and FA fractions. Elemental analysis (C, N and H) of compost and HA samples showed an increase in the C:H ratio and in unsaturation of compounds during composting. The decrease in the C:N ratio was marginal.

The amounts of hexoses and pentoses in original compost samples and the HA and FA fractions decreased during composting. The sugar alcohols erythritol, xylitol, L-arabitol, ribitol, L-rhamnitol, L-fucitol, D-mannitol, D-glucitol and galactitol were identified in both the HA and FA fractions. 2-Deoxy-D-erythro-pentitol was identified in one HA fraction and inositol in two FA fractions. An analysis of gas chromatographic data for relative abundances showed that, in every sample except one and in every stage of composting D-glucitol was the main sugar alcohol. In general, the relative amount of D-glucitol decreased during composting, while the relative amounts of all other sugar alcohols increased.

As chemical indicators of compost maturity, carbohydrates would appear to be a important group of compounds. Most informative as a general indicator would be the ratio of the amount of HA to the amount of organic matter in the total compost samples.

According to our studies, the carbohydrates in composts are covalently bound to the structures of FA and HA. Carbohydrate determination clearly deserves more attention in the structural elucidation of FA and HA.  相似文献   
17.
The phytoestrogen content of birdsfoot trefoil (Lotus corniculatus L.) and red clover (Trifolium pratense L.) was determined. In addition, the effects of growth stage, wilting and ensiling additives on content were studied. Birdsfoot trefoil raw material and silage contained only traces of phytoestrogens. In red clover raw material and silage, the phytoestrogen content varied from 0.8% to 1.1% of dry matter. Content was affected by growth stage of the plant and wilting. Formononetin concentration decreased as the plant matured from budding to flowering stage, and wilting from 25% to 40% of dry matter content decreased genistein and biochanin A content. The phytoestrogen content of red clover silage was 18% higher than that of raw material. Silage additives also affected the content. Silage ensiled with an additive containing Lactobacillus plantarum bacterial inoculate had higher concentrations of genistein and biochanin A than silage made with formic acid.  相似文献   
18.
Stumps are the largest coarse woody debris component in managed forests, but their role in nutrient cycling is poorly understood. We studied carbon (C) and nitrogen (N) dynamics in Scots pine (Pinus sylvestris), Norway spruce (Picea abies), and silver birch (Betula pendula) stumps, which had decomposed for 0, 5, 10, 20, 30 and 40 years after clear-cutting in southern Finland. Carbon and N were released significantly faster from birch stumps than from conifer stumps. In 40 years, conifer stumps lost 78% and birch stumps 90% of their initial C. In contrast, the amount of N in stumps increased, indicating that external N accumulated in the stumps. After 40 years of decomposition, the amount of N was 1.7 and 2.7 times higher than the initial amount in pine and spruce stumps, respectively. Nitrogen was released from birch stumps, but only after they had decomposed for 20 or more years. On average, 59% of N stored in birch stumps was released during 40 years. The results indicate that the stumps of the major tree species in Fennoscandian forests are long-term C and, especially, N pools which serve as N sinks, thus potentially diminishing N leaching into ground water and watercourses after harvesting. This suggests that the removal of stumps for bioenergy production may markedly affect the nutrient status and nutrient cycling of boreal forests.  相似文献   
19.
The availability of human time and the factors affecting its allocation play an important role in the individual choices between daily activities. It can be claimed that the allocation of time for various forest related (household or recreational) activities provides one common yardstick to examine the significance of forest uses in the everyday life of ordinary people. This paper examines the time allocation of ordinary Finns (aged 10 years or over) outside of their work or school hours to selected forest-related small-scale activities derived from household needs or recreational purposes at the turn of the millennium (1999–2000), and investigates the factors affecting the time spent on forest work performed by Finnish population outside of the labour market. It was found that about 3% of total human available time was allocated in outdoor recreation or related activities. Spatially, 22% (52 h/person/year) of total time was allocated in forest-based, 23% in water-based and the rest in mixed environment-based activities. The time spent on the consumptive nature-based recreation activities, including recreational fishing and leisure time forest work, was 43 h corresponding 19% of total time of the activities studied. The estimated time spent on forest work was higher than found in earlier studies. The amount of time used in forest work was highest among farmers, aged 60 and over, pensioners and unemployed persons. An unexpectedly large proportion of time was spend in the fuelwood production and consumption chain from forest to fireplace. The precise observations within the fixed time frame are the major advantages of the time-budget method, which however demands substantial resources for implementation.  相似文献   
20.
The aim of this study is to identify and analyse the institutionalarrangements that regulate the forest lease and related marketsof industrial timber in Russia. A theoretical framework is derivedfrom institutional economics. Institutions, their hierarchyand cohesion are surveyed at constitutional, collective-choiceand operational levels. The organization of the long-term forestlease and its contribution to the sustainable forest managementand development of forest industries are described and regionaldifferences in the organization of forestry are tested. In addition,the expected impacts of the new federal Forest Code are analysed.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号