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   79篇
  免费   0篇
林业   6篇
农学   4篇
基础科学   1篇
  43篇
综合类   3篇
农作物   2篇
畜牧兽医   3篇
园艺   5篇
植物保护   12篇
  2023年   1篇
  2022年   2篇
  2021年   3篇
  2020年   1篇
  2018年   3篇
  2017年   2篇
  2016年   2篇
  2015年   1篇
  2014年   2篇
  2013年   10篇
  2012年   3篇
  2011年   1篇
  2010年   2篇
  2009年   4篇
  2008年   1篇
  2007年   3篇
  2006年   3篇
  2005年   5篇
  2004年   2篇
  2003年   2篇
  2002年   7篇
  2001年   1篇
  1998年   1篇
  1997年   2篇
  1996年   5篇
  1995年   1篇
  1993年   3篇
  1992年   2篇
  1991年   1篇
  1990年   1篇
  1987年   1篇
  1983年   1篇
排序方式: 共有79条查询结果,搜索用时 31 毫秒
1.
In the 1970s unexpected forest damages, called “new type of forest damage” or “forest decline”, were observed in Germany and other European countries. The Federal Republic of Germany and the German Federal States implemented a forest monitoring system in the early 1980s, in order to monitor and assess the forest condition. Due to the growing public awareness of possible adverse effects of air pollution on forests, in 1985 the ICP Forests was launched under the convention on long-range transboundary air pollution (CLRTAP) of the United Nations Economic Commission for Europe (UN-ECE). The German experience in forest monitoring was a base for the implementation of the European monitoring system. In 2001 the interdisciplinary case study “concept and feasibility study for the integrated evaluation of environmental monitoring data in forests”, funded by the German Federal Ministry of Education and Research, concentrated on in-depths evaluations of the German data of forest monitoring. The objectives of the study were: (a) a reliable assessment of the vitality and functioning of forest ecosystems, (b) the identification and quantification of factors influencing forest vitality, and (c) the clarification of cause-effect-relationships leading to leaf/needle loss. For these purposes additional data from external sources were acquired: climate and deposition, for selected level I plots tree growth data, as well as data on groundwater quality. The results show that in particular time series analysis (crown condition, tree growth, and tree ring analysis), in combination with climate and deposition are valuable and informative, as well as integrated evaluation of soil, tree nutrition and crown condition data. Methods to combine information from the extensive and the intensive monitoring, and to transfer process information to the large scale should be elaborated in future.
Sabine AugustinEmail:
  相似文献   
2.
Mixed modelling for QTL × environment interaction analysis   总被引:2,自引:0,他引:2  
Phenotypic data for quantitative trait loci (QTL) mapping studies are typically generated at multiple environments in order to broaden the inference space. Many aspects of the usually complex design call for a mixed modelling approach taking into account various sources of variation, e.g., incomplete blocks, a spatial error structure, genetic correlations due to the pedigree, and random environmental effects, including QTL × E interaction. Perhaps the most important source of random variation is the genetic correlation across environment, which arises when the same set of lines is tested in each environment. This correlation is likely to be positive, and ignoring it will lead to an increased rate of false positives. In this paper, we present a mixed modelling framework for QTL mapping based on complex data from multiple environments. Our main focus is on an appropriate modelling for the non-QTL part. The methodology will be illustrated using a barley data set from a BC2F2:5 advanced backcross trial. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   
3.
Summary There is an increasing number of stability parameters for genotypes grown in different environments. It is therefore useful to study the statistical relations between these parameters. One approach is the calculation of rank correlations between different stability parameters in empirical data sets. In the data analysed there are high rank correlations between ecovalence Wi, deviation mean square s2 di, the nonparametric measures Si (1), Si (2), and two new measures Ri and Li as well as between environmental variance S2 xi and regression coefficient bi. The results suggest that Si (1), Si (2), Li, and Ri can be used as alternatives to Wi and the stability variance 2 i. This may be worthwhile, if certain statistical assumptions do not hold, particularly if significance testing is needed.  相似文献   
4.
Although hardly any polyunsaturated fatty acids (PUFAs) are present in the endproduct, the ingredients used for the production of beer contain a high concentration of PUFAs, such as linolic and linolenic acid. These compounds are readily oxidized, resulting in the formation of lipid-derived products that reduce the taste and quality of beer enormously. During mashing relatively high amounts of PUFAs are exposed to atmospheric oxygen at a relatively high temperature. This makes mashing a critical step in the brewing process with regard to the formation of lipid-derived off-taste products. F1 phytoprostane (PPF1) changes in antioxidant capacity and monohydroxy fatty acids (OH-FAs) were used as markers for the detection of oxidative damage to fatty acids during mashing. The pattern of OH-FA formation indicates that enzymatic oxidation of PUFAs is more important than nonenzymatic oxidation during the mashing process. Nevertheless, substantial nonenzymatic radical formation is evident from the increase of specific OH-FAs and PPF1s. It was found that a low oxygen tension reduces oxidative damage and gives a high antioxidant capacity of the mashing mixture. This indicates that mashing should be done under low oxygen pressure.  相似文献   
5.
Conception soil maps for urban areas The demand for soil maps increased strongly during the last years. This concerns urban soils, too. Conception soil maps constructed from a lot of basic informations (basic maps and point data) are the alternative to traditional soil mapping, which is expensive in time and money for urban areas. Further informations are to evaluate maps from these conception soil maps. Using graphic information-systems is advantageous for construction and evaluation.  相似文献   
6.
7.
The timing of the dispersal of anatomically modern humans (AMH) out of Africa is a fundamental question in human evolutionary studies. Existing data suggest a rapid coastal exodus via the Indian Ocean rim around 60,000 years ago. We present evidence from Jebel Faya, United Arab Emirates, demonstrating human presence in eastern Arabia during the last interglacial. The tool kit found at Jebel Faya has affinities to the late Middle Stone Age in northeast Africa, indicating that technological innovation was not necessary to facilitate migration into Arabia. Instead, we propose that low eustatic sea level and increased rainfall during the transition between marine isotope stages 6 and 5 allowed humans to populate Arabia. This evidence implies that AMH may have been present in South Asia before the Toba eruption.  相似文献   
8.
Introducing autumn-sown legumes into Central European farming systems could be beneficial for addressing two challenges for European agriculture, i.e., the substantial deficit of protein sources for livestock and expected changes in agroclimatic conditions. Therefore, a two-year field experiment was conucted under Pannonian climate conditions in eastern Austria to assess nitrogen (N) yield and N fixation of several winter faba bean varieties from different European countries as compared to a spring faba bean. Winter wheat was used as a reference crop for estimating atmospheric N fixation. Winter faba beans were susceptible to frost damage especially in the harder of the two winters. Winter faba bean varieties could not achieve a higher grain yield and a higher grain N yield than the spring faba bean but had a higher grain N concentration (except for one variety). Grain yield and grain N yield of faba beans were severely impaired by drought in one year (with a mean of varieties of 8.3 g N m?2, winter wheat: 6.4 g N m?2); in the other year, grain N yield of faba beans considerably surpassed that of winter wheat (with a mean of varieties of 21.5 g N m?2, winter wheat: 8.8 g N m?2). After harvest, faba beans left higher nitrate residues in the soil, especially in the subsoil, and higher amounts of N in above-ground residues compared to winter wheat. Faba beans showed high N fixation under optimum conditions (with a mean of varieties of 21.9 g N m?2) whereas drought considerably impaired N fixation (with a mean of varieties of 6.3 g N m?2; with no differences between autumn- and spring-sown faba beans). In conclusion, growing winter faba bean varieties in eastern Austria did not result in higher grain yield, grain N yield, and N fixation compared to growing a spring faba bean.  相似文献   
9.
This study describes the experience with hypofractionated radiation therapy of squamous cell carcinoma and melanoma in dogs and cats. A total dose of 32-48 Gray (Gy) was delivered once a week in 8 Gy fractions. 34 animals in which a complete surgical excision was impossible were treated. There was no tumor detectable macroscopically in 14 patients at the beginning of radiation therapy. In 20 animals the median volume of the tumor was 9.9 cm3. The median survival times and the local tumor control of squamous cell carcinoma of the oral and nasal cavities and of the body are comparable to results which were reached with a Monday-Wednesday-Friday scheme. For the treatment of Melanoma the hypofractionated radiation therapy is first choice. There are no significant side effects. Late side effects did not occur. 88% of the owners are satisfied with this kind of treatment and would choose it again.  相似文献   
10.
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