全文获取类型
| 收费全文 | 3505篇 |
| 免费 | 294篇 |
| 国内免费 | 4篇 |
专业分类
| 林业 | 976篇 |
| 农学 | 64篇 |
| 基础科学 | 24篇 |
| 243篇 | |
| 综合类 | 1607篇 |
| 农作物 | 34篇 |
| 水产渔业 | 4篇 |
| 畜牧兽医 | 44篇 |
| 园艺 | 767篇 |
| 植物保护 | 40篇 |
出版年
| 2025年 | 10篇 |
| 2024年 | 34篇 |
| 2023年 | 156篇 |
| 2022年 | 200篇 |
| 2021年 | 42篇 |
| 2020年 | 64篇 |
| 2019年 | 72篇 |
| 2018年 | 109篇 |
| 2017年 | 141篇 |
| 2016年 | 163篇 |
| 2015年 | 92篇 |
| 2014年 | 225篇 |
| 2013年 | 222篇 |
| 2012年 | 298篇 |
| 2011年 | 312篇 |
| 2010年 | 313篇 |
| 2009年 | 287篇 |
| 2008年 | 247篇 |
| 2007年 | 275篇 |
| 2006年 | 175篇 |
| 2005年 | 89篇 |
| 2004年 | 76篇 |
| 2003年 | 58篇 |
| 2002年 | 42篇 |
| 2001年 | 23篇 |
| 2000年 | 23篇 |
| 1999年 | 13篇 |
| 1998年 | 10篇 |
| 1997年 | 7篇 |
| 1996年 | 6篇 |
| 1995年 | 5篇 |
| 1994年 | 6篇 |
| 1993年 | 2篇 |
| 1992年 | 1篇 |
| 1989年 | 1篇 |
| 1988年 | 2篇 |
| 1987年 | 2篇 |
排序方式： 共有3803条查询结果，搜索用时 19 毫秒
61.
Esther S Rubin Walter M Boyce Chris J StermerSteven G Torres 《Biological conservation》2002,104(2):251-263
To further understand the impact of urban development on wildlife populations, we examined habitat use and selection by female bighorn sheep Ovis canadensis in two endangered subpopulations near a metropolitan area in southern California. One subpopulation, which had previously been found to have low reproductive success, selected urban environments while the other did not use urban areas. In the subpopulation that used urban areas, females had smaller core activity areas and selected lower elevations and gentler slopes. These females used urban sources of water but a clear relationship between levels of urban use and periods of increased water need was not evident. Diet quality was higher among females that selected urban areas, and this increase was correlated with the level of urban use. Thus, optimal foraging behavior may have contributed to the selection of urban areas. Urban use was lowest during peak months of parturition, suggesting that reproductive strategies may also have influenced temporal patterns of urban use. Although urban areas provided bighorn sheep with forage and water resources, the use of these areas may have substantial costs. For example, females using urban areas had internal parasites that were not found elsewhere in the Peninsular Ranges. 相似文献
62.
To reduce soil destruction by urban sprawl, land use planning has to promote the use of soils within cities. As soil functions are now protected by law in Germany, urban soil quality has to be evaluated before soil management. We studied contributions from elemental carbon (EC) and soil organic matter (SOM) quality in topsoil horizons at seven sites in Stuttgart, Germany, differing in impurities by technogenic substrates. The most disturbed site was found at a disused railway area while high-density areas, public parks and garden areas showed varying degrees of disturbance by anthropogenic activities. For most soils, compounds derived from plant litter dominated organic matter (OM) quality characterized by nuclear magnetic resonance (NMR) spectroscopy. Although high contents of EC (up to 70% of soil organic carbon) were indicated by thermal oxidation, this was not confirmed by aromatic C intensities in NMR spectra. Only for the highly aromatic railway soil were results for elemental carbon by thermal oxidation and NMR similar. As other technogenic substrates beside EC like plastics may also contribute in the long-term to OM in urban soils, new analytical techniques are therefore required. This knowledge will promote the evaluation of urban soil properties and their sustainable use. 相似文献
63.
A field survey assessed the restorative effects of visiting an urban forest and a city park in Zurich, Switzerland. Respondents rated their headaches, level of stress, and how balanced they felt both prior to visiting the outdoor location and at the time of being interviewed. Suffering from headaches and stress decreased significantly, and feeling well-balanced increased significantly. The recovery ratio for stress was 87%, and the reduction in headaches was 52%, in terms of the possible improvements on five-point rating scales. With respect to feeling well-balanced, the observed changes amounted to 40% of the possible enhancement. Positive effects increased with length of visit, and individuals practising sports (e.g., jogging, biking, playing ball) showed significantly higher improvements than those engaged in less strenuous activities (e.g., taking a walk or relaxing). These findings support previous research on how exercise in green spaces promotes well-being and recovery from stress. 相似文献
64.
As the impact of green space shrinkage in urban centers becomes obvious, local and regional authorities must adopt environmental planning policies that can help create new green areas to ensure a good quality of life for citizens, along with the rehabilitation of the natural environment. One approach is the promotion of green infrastructure on buildings, including multi-dwelling apartment buildings. In order to effectively promote green infrastructure on buildings, it is essential to comprehend public attitudes toward green infrastructure, so that suitable and effective strategies can be implemented by policy makers. In this study, eight hundred respondents were asked to provide their views on green infrastructure on buildings, on construction that should take place on blocks of apartments in order to accommodate green infrastructure and on the related benefits that may arise from creating green spaces on buildings. A structured questionnaire and stratified sampling were used for the interviews, which were conducted with apartment owners in two regional units of Athens. The results showed that most citizens are willing to proceed with the installation of a green roof, trellis or vertical garden, in order to improve the aesthetics and functionality of the building they live in. Most of the respondents are not familiar with the energy savings that may occur from the installation of a green roof, vertical trellis or garden and wish for a subsidy from the state in order to implement green building solutions. To conclude, the participants in our study are not environmentally aware, since they are not interested in energy conservation but only about the aesthetics of their building; furthermore, they expect to receive financial support from the state in order to make any changes to their home. 相似文献
65.
66.
干劲天 《北京农业职业学院学报》2001,15(4):37-38
都市农业是在城郊农业内部产生和发展起来的。都市农业与城郊农业在其生长地域、功能、以及产业布局等十个方面存在重要的内在联系和转变接点。 相似文献
67.
68.
结合对广州白云山风景名胜区规划和建设的调研和观察结果,从布局、功能、配套设施、生态结构4个方面加以分析,试图总结并归纳城市风景类风景名胜区规划建设的特点和内在规律,为相关风景区规划与建设提供参考。 相似文献
69.
亲水河为无锡市太湖岸线一条景观河道,水质较差.通过探讨生物绳、重建生物群落联合修复技术对城市河道的修复效果对其进行了为期半年多的生态修复效果研究.结果表明,上述工程措施能够有效去除水体中的有机物、总氮、总磷等污染物,增加水体透明度. 相似文献
70.