全文获取类型
收费全文 | 221篇 |
免费 | 19篇 |
专业分类
林业 | 9篇 |
农学 | 2篇 |
20篇 | |
综合类 | 51篇 |
农作物 | 4篇 |
水产渔业 | 13篇 |
畜牧兽医 | 126篇 |
园艺 | 1篇 |
植物保护 | 14篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2018年 | 2篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 8篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 4篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 4篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 4篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 8篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1970年 | 6篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1964年 | 2篇 |
1925年 | 1篇 |
1919年 | 1篇 |
1900年 | 1篇 |
排序方式: 共有240条查询结果,搜索用时 125 毫秒
1.
通过研究褐煤在氧化氨解反应后特性的变化及其在退化土壤造林中的应用效果,旨在探索褐煤高效利用的有效途径.结果表明:氧化氨解工艺能有效地提高褐煤的阳离子交换量、腐殖酸总量和富里酸含量,降低胡敏素含量.反应生成的氮改性褐煤,全氮含量为5.8%,且呈不同形态(铵态、酰胺态和紧密有机态氮态)的分布,能在土壤中保存较长的时间.半干旱退化土壤中的应用试验表明,在土壤中掺入氮改性褐煤(每株137 g或274 g)可使樟子松林分造林成活率提高20%~25%,而施用相应含氮量的尿素对林木成活率几乎没有作用.随着立地条件的改善和植被的恢复,施用氮改性褐煤林分的土壤碳汇、土壤微生物总量以及脱氢酶、脲酶、β-葡糖苷酶、碱性磷酸酶等的活性都有明显的提高,证实了氮改性褐煤可以作为一类生态和环保的土壤改良剂. 相似文献
2.
Nicole?WellbrockEmail author Winfried?Riek Barbara?Wolff 《European Journal of Forest Research》2005,124(4):261-271
Based on the results of the atmospheric deposition classification of the year 1989, a methodical approach should be introduced,
which—based on the modelled total deposition rates—enables us to characterise the input situation of forest monitoring plots
and to delimit load areas in Germany. In 1989, the deposition situation in nearly 1,800 forest monitoring sites (BZE/extensive
Soil Condition Inventory) in Germany could be explained by four factors (or three, excluding sea salt impact) with the help
of a factor analysis. The factor values were grouped into six deposition types with typical compounds and regional patterns.
The classified input rates of the soil inventory plots adequately represent the stress situation and deposition changes in
Germany. The application of the statistical approach on the level of Brandenburg clarifies the special local input situation.
Due to the special combination of deposed elements, the sources of emissions can be characterised as well. When the soil inventory
is repeated, a project planned for 2006, this approach can be used in order to determine homogenous areas for stratified data
evaluation. 相似文献
3.
Sabine Augustin Jan Evers Hans-Peter Dietrich Johannes Eichhorn Thomas Haussmann Regina Icke Ansgar Isenberg Wolfgang Lux Monica Musio Hans Pretzsch Winfried Riek Thomas Rötzer Bernd Schultze Andreas Schulze Jörg Schröder Walter Seidling Nicole Wellbrock Klaus von Wilpert Barbara Wolff 《European Journal of Forest Research》2005,124(4):251-260
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.
相似文献
Sabine AugustinEmail: |
4.
5.
Murilla GA Eisler MC Peregrine AS Ndung'u JM Holmes PH 《Journal of veterinary pharmacology and therapeutics》1999,22(5):301-307
Two enzyme-linked immunosorbent assays (ELISA) for the determination of homidium in serum of treated cattle have been developed and evaluated. One is a direct competition (Assay 1) and the other an indirect competition assay (Assay 2). Both assays are highly sensitive with a limit of detection of 0.1 ng homidium per mL serum. Homidium levels were measurable in serum of cattle for over 2 months following administration of a single intramuscular (i.m.) dose at 1 mg/kg bodyweight. The level of sensitivity afforded by these assays makes them potentially useful tools in the pharmacokinetic evaluation of homidium and for investigating drug resistance or causes of drug failure. Assay 2 was chosen as being most suitable for further studies. 相似文献
6.
A S Peregrine O Ogunyemi D D Whitelaw P H Holmes S K Moloo H Hirumi G M Urquhart M Murray 《Veterinary parasitology》1988,28(1-2):53-64
The duration of a single isometamidium chloride (Samorin) prophylactic treatment against Trypanosoma congolense ILNat. 3.1 and T. congolense IL 285 was examined in 24 Boran steers with regard to (1) the dose of drug, (2) the level of metacyclic challenge and (3) the influence of infection with an unrelated serodeme at the time of treatment. The cattle were repeatedly challenged at monthly intervals between 2 and 7 months following treatment, either by five infected Glossina morsitans centralis or by intradermal inoculation of 5 X 10(3) or 5 X 10(5) in vitro-derived metacyclic trypanosomes. A dose of 1 mg kg-1 afforded complete protection for 4 months and 0.5 mg kg-1 for 3 months against the two T. congolense serodemes examined, irrespective of the method or weight of challenge. In another group of cattle, which had an established infection at the time of treatment, the duration of chemoprophylaxis against an unrelated serodeme was the same as the other groups which had no previous experience of trypanosome infection. Antibodies to metacyclics did not appear in any of the cattle as long as the chemoprophylaxis was effective. An exception to this was the group challenged with 5 X 10(5) in vitro-derived metacyclic parasites, in which low antibody titres were detected. In all cases these proved to be non-protective. It was concluded that, under the experimental conditions employed, (1) there was a direct relationship between drug dosage and the duration of chemoprophylaxis, (2) the weight of metacyclic challenge did not affect the duration of chemoprophylaxis and (3) when used to treat an existing infection, isometamidium chloride exerted the same degree of chemoprophylactic activity. 相似文献
7.
8.
9.
10.