全文获取类型
收费全文 | 10497篇 |
免费 | 663篇 |
国内免费 | 505篇 |
专业分类
林业 | 2676篇 |
农学 | 510篇 |
基础科学 | 572篇 |
1128篇 | |
综合类 | 4159篇 |
农作物 | 578篇 |
水产渔业 | 320篇 |
畜牧兽医 | 740篇 |
园艺 | 148篇 |
植物保护 | 834篇 |
出版年
2024年 | 49篇 |
2023年 | 207篇 |
2022年 | 293篇 |
2021年 | 380篇 |
2020年 | 305篇 |
2019年 | 391篇 |
2018年 | 183篇 |
2017年 | 282篇 |
2016年 | 366篇 |
2015年 | 362篇 |
2014年 | 549篇 |
2013年 | 589篇 |
2012年 | 806篇 |
2011年 | 766篇 |
2010年 | 640篇 |
2009年 | 635篇 |
2008年 | 622篇 |
2007年 | 621篇 |
2006年 | 553篇 |
2005年 | 485篇 |
2004年 | 376篇 |
2003年 | 359篇 |
2002年 | 309篇 |
2001年 | 245篇 |
2000年 | 225篇 |
1999年 | 205篇 |
1998年 | 152篇 |
1997年 | 124篇 |
1996年 | 102篇 |
1995年 | 79篇 |
1994年 | 76篇 |
1993年 | 58篇 |
1992年 | 65篇 |
1991年 | 59篇 |
1990年 | 45篇 |
1989年 | 34篇 |
1988年 | 31篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1980年 | 3篇 |
1962年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
1.
2.
3.
在农业生产中由于化学农药的长期不合理使用,导致"3R"问题持续存在和人类赖以生存的环境日益恶化,生物防治产品及技术在有害生物综合治理中的作用越发重要。天敌昆虫的生长发育及存活期往往很短,探索其储存技术是天敌昆虫规模化生产中的关键性环节。低温贮藏可以延长天敌昆虫的寿命,进而可以为生物防治提供充足、稳定的天敌产品。因此,天敌昆虫低温贮藏一直是生物防治领域研究的热点。本文围绕天敌昆虫低温贮藏这一环节,就低温诱导天敌昆虫滞育虫态、冷驯化对昆虫低温贮藏效果的影响、低温贮藏对天敌昆虫适合度(寿命、羽化率、性比、个体尺寸大小、飞行扩散能力等)的影响等方面进行综述,以期为天敌昆虫产品的规模化生产及应用技术提供参考。 相似文献
4.
Soil protection for a sustainable future: options for a soil monitoring network for Ireland
下载免费PDF全文
![点击此处可从《Soil Use and Management》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The increased recognition of the importance of soil is reflected in the UN Post‐2015 Development Agenda with sustainable development goals that directly and indirectly relate to soil quality and protection. Despite a lack of legally binding legislation for soil protection, the European Commission remains committed to the objective of soil protection. However, the achievement of a legally binding framework for soil protection relies on the implementation of a soil monitoring network (SMN) that can detect changes to soil quality over time. As beneficiaries do not pay for the provision of soil information, the options for soil monitoring are limited. The use of existing data sets should be considered first. Using Ireland as an example, this research explored the opportunities for a SMN for Ireland considering three existing national data sets. The options for a SMN are considered in terms of their spatial and stratified distribution, the parameters to be measured and an economic analysis of the options proposed. This research finds that for Ireland, either a 10 or a 16 km2 grid interval stratified by land use and drainage class offers the best potential in relation to the spatial distribution of existing data sets to reflect local data at a national level. With existing data, the stratified SIS data using the 16 km2 grid offers the best value for money, with baseline costs for analysis, excluding field costs, of between €706 481 and €2.8 million. Acknowledging the impossibility of measuring all parameters with ideal frequency, this study proposes a two‐tier system for optimized monitoring frequency. Parameters must anticipate future policy requirements. Finally, the implementation of a SMN must be accompanied by standardized methods, defined thresholds and action mandates to maintain soil quality within allowable limits. 相似文献
5.
社会林业与五指山的自然保护 总被引:1,自引:0,他引:1
五指山自然保护区是世界上现存地势最高的原始热带雨林之一,是我省目前面积最大的自然保护区,也是海南三大河流的发源地。但由于保护区横跨琼中、通什、保亭三县、市,紧邻保护区还生存着众多贫困的黎、苗族村民。因此,保护区与周边社区的联系是十分紧密的,社区的发展也直接影响到五指山热带天然林的保护。海南省林业局中德海南热带林保护和恢复项目在社会林业与五指山森林的保护上做出了有益的尝试,就在全省来说,也是首次对社会林业与森林保护上进行的探索。五指山地区社会林业的研究,对保护海南热带雨林也有着积极的意义。特对社会林业与五指山的森林保护进行了阐述、分析和设想。 相似文献
6.
在查清天津市园林主要花灌木刺吸口器害虫桃粉蚜、绣线菊蚜、棉蚜和山楂红蜘蛛发生消长规律的基础上 ,确定了防治适期和结合点 ,筛选出 10 %吡虫啉、绿灵、蚧螨灵、 1. 8%齐螨素和花保5种低、无毒药剂 ,防效均达到 90 %以上。查出天敌 13种 ,并对优势种作了取食量调查 相似文献
7.
LIJing LIRui ZHENGFen-li 《水土保持研究》2004,11(4):174-176
Erosion and transport of soil has worldwide implications for agriculture, landscape stability, climate, natural hazards, and clean, renewable resources of water and air. Assured access to clean water and a healthy and safe environment requires an ethic of conservation and protection. The minimum scale in which these principles apply successfully is basin wide. These are the fundamental concerns of the Sino-US Centers for Soil and Water Conservation and Environmental Protection. 相似文献
8.
9.
Antiserum to a partially purified neuraminidase fromPasteurella multocida, type A:3, was adsorbed with protease-digestedP. multocida type 3 lipopolysaccharide (LPS) to remove LPS immunoreactivity. The LPS-adsorbed antineuraminidase caused a 77% reduction in the neuraminidase activity of homologousP. multocida in anin vitro enzyme neutralization test. All 14 mice passively immunized with the adsorbed antineuraminidase were protected against challenge infection with homologousP. multocida in a mouse protection test. Ten out of 14 mice in one group that received antisera containing antibodies to both neuraminidase and LPS were protected. In contrast, only 1 out of 14 mice that were immunized with pre-immune serum survived the challenge. These results suggest that antiserum toP. multocida neuraminidase was, at least partly, responsible for the protection observed in this study. Neuraminidase may be one of the immunogenic protective proteins present in aqueous extracts ofPasteurella multocida. 相似文献
10.