全文获取类型
收费全文 | 53篇 |
免费 | 3篇 |
国内免费 | 3篇 |
专业分类
林业 | 7篇 |
农学 | 4篇 |
基础科学 | 6篇 |
10篇 | |
综合类 | 22篇 |
农作物 | 1篇 |
水产渔业 | 2篇 |
畜牧兽医 | 2篇 |
园艺 | 1篇 |
植物保护 | 4篇 |
出版年
2022年 | 3篇 |
2020年 | 2篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 4篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2005年 | 2篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有59条查询结果,搜索用时 0 毫秒
1.
生态文明建设需要科学的自然观指导.本文挖掘整理被列为国家级非物质文化遗产的景颇族创世史诗《目瑙斋瓦》中的自然观,明确了景颇族朴素自然观表征的历史脉络,分析了其中蕴含的天、地、人“三才”和谐统一的辩证思维方式,这对把握滇西景颇族维系生态平衡的民族传统,合理利用地方性知识促进民族地区生态文明建设有现实意义,也对弘扬优秀的民族民间文化有积极作用. 相似文献
2.
Fractal image coding techniques usually partition the input image into small range blocks. This artificially introduces boundaries into the image resulting in the unpleasant blocking artifacts in the decoded images especially at high compression rate. Because the effect is especially responsible for the restrictions of the block-based coders, the solutions must be sought to reduce this blockiness. Recently two possible schemes have been proposed by other researchers: One may try to use overlapping blocks in the fractal transform, and the other to employ the combined fractal wavelet approach. An alternative solution is proposed, which employs the bilinear interpolation techniques and the resolution independence of fractal coding, in the sense that an image can be decoded at higher or lower resolutions than the original. Experiments show that the proposed scheme can eliminate the blocking artifacts. 相似文献
3.
How to characterize ‘good’ and ‘greening’ in the EU Common Agricultural Policy (CAP): the case of clay soils in the Netherlands 下载免费PDF全文
The change in the Common Agricultural Policy (CAP) of the European Union from product to producer support, including requirements for ‘good agricultural and environmental conditions’ and ‘greening’, is excellent. However, these requirements are now defined in rather general terms. Questions can be raised about suitable indicators, and there is a recognized need for effective management recommendations to support farmers in achieving the required ‘good’ conditions. These recommendations are bound to be quite different for different soils in different countries. A study of Dutch clay soils was based on a storyline describing current problems and management options for improvement, which were quantified using a soil–water–crop simulation model. Indicators were defined for agricultural conditions and suggestions made for the use of the model in a predictive mode to help farmers improve their soil management. Environmental conditions were judged by current environmental guidelines for water and air. When modelling, implicit assumptions that soils are homogeneous were shown to be unrealistic for these clay soils, requiring development of innovative methods and procedures, presenting a challenge for soil research. 相似文献
4.
针对磁瓦表面裂纹缺陷图像背景不均匀、对比度低和存在纹理干扰等特点,提出了一种基于非下采样Shearlet变换(Nonsubsampled Shearlet transform,NSST)的裂纹检测方法。首先对原始图像进行多尺度、多方向NSST分解,得到一个低频子带和多个高频子带,然后利用各向异性扩散和改进的γ增强方法对高频子带进行滤波和增强;同时利用二维高斯函数对低频子带进行卷积操作来构造高斯多尺度空间,估计出图像的主要背景,并通过背景差法得到均匀的低频目标图像。最后通过重构NSST系数得到去噪和增强后的均匀目标图像,利用自适应阈值分割和区域连通法提取裂纹缺陷。实验结果表明,所提方法检测准确率达92.5%,优于基于形态学滤波方法、基于Curvelet变换方法和基于Shearlet变换方法等现有磁瓦表面裂纹检测方法。 相似文献
5.
本文采用一元二次回归分析方法,对黄河河套灌区超吨粮田不同层次的光温风分布状况进行了定量分析,求算了三因子在不同层次的最佳指标值X1及其相应的期望产量值Y_(max)。鉴于植株2/3处光温风分布综合反映了群体结构的生产潜力,故组建了2/3层次的多元非线性复合小气候效应模型。给出了亩产1250.0公斤的超吨粮理论指标。指出实现这一理论产量的关键,是广泛推广玉米催芽栽培技术。 相似文献
6.
采用免疫组织化学SABC法对短蛸 (Octopus ocellatus) 消化系统和部分器官中受体(mu opioid receptor)进行定位研究。结果表明,短蛸腕、漏斗、外套膜腹面、口球、嗉囊、胃盲囊、肠、直肠、前唾液腺、后唾液腺、肝胰脏均呈受体阴性,但食道内上皮、外膜、结缔组织和胃角质层有受体分布,外套膜背面、腕间膜的上皮或近上皮部位呈受体阳性。受体在短蛸不同部位分布密度的不同,可能与各器官的功能不同有关。 相似文献
7.
8.
Leaching of nitrogen from arable land can lead to pollution of groundwater and surface water. Various measures have been implemented in agriculture to reduce leaching, but there is still potential to do more. To find the best agricultural management regime to limit the problem, leaching from soils under different management must be measured. Different methods to estimate leaching are available, but they have not been thoroughly evaluated. This study compared (a) leaching of nitrogen from five different fertilizer treatments differing in amount and source (mineral and organic) of nitrogen and (b) two different methods for measuring leaching (tile-drained field plots and lysimeters). Nitrogen leaching from five different fertilizer treatments was studied for three years in a tile-drained field facility and for three of the treatments also for 16 months in a lysimeter facility. Leaching from organic and mineral nitrogen sources was similar in the three-year field study. Mineral nitrogen input above the economic optimum tended to give greater leaching (by 24%–43%) than nitrogen input at the expected optimum. Measurements in lysimeters and tile-drained field plots gave similar results, although leaching values tended to be slightly higher (by 18%–25%) in the tile-drained field. Overall, both facilities give reliable estimates of nitrogen leaching and are suitable for leaching studies. 相似文献
9.
10.
2004年引进了原产非洲东部中高山地区的竹亚科(Bambusoideae)锐药竹属(Oxytenanthera Mun-ro)竹种--酒竹(O.braunii Pilger ap.Engler),经过近4年的引种栽培,实地调查发现,与邻近勃氏甜龙竹(Dendrocalamus brandisii Kurz)、马来甜龙竹(D.asper (Schult.f.)Backer ex Heyne)、麻竹(D.latiflorus Munro)竹林相比较,笋横锥大象(Cyrtotrachelus buqueti Guer)、笋直锥大象(C.longimanus Fabricius)和巨红蝽(Macroceroes grandis Gray)特别喜食酒竹笋. 相似文献