全文获取类型
收费全文 | 4343篇 |
免费 | 398篇 |
国内免费 | 442篇 |
专业分类
林业 | 605篇 |
农学 | 277篇 |
基础科学 | 210篇 |
833篇 | |
综合类 | 1826篇 |
农作物 | 73篇 |
水产渔业 | 571篇 |
畜牧兽医 | 317篇 |
园艺 | 60篇 |
植物保护 | 411篇 |
出版年
2024年 | 27篇 |
2023年 | 133篇 |
2022年 | 161篇 |
2021年 | 182篇 |
2020年 | 233篇 |
2019年 | 239篇 |
2018年 | 155篇 |
2017年 | 210篇 |
2016年 | 215篇 |
2015年 | 200篇 |
2014年 | 260篇 |
2013年 | 275篇 |
2012年 | 345篇 |
2011年 | 314篇 |
2010年 | 263篇 |
2009年 | 275篇 |
2008年 | 214篇 |
2007年 | 269篇 |
2006年 | 217篇 |
2005年 | 181篇 |
2004年 | 159篇 |
2003年 | 119篇 |
2002年 | 112篇 |
2001年 | 77篇 |
2000年 | 69篇 |
1999年 | 49篇 |
1998年 | 43篇 |
1997年 | 24篇 |
1996年 | 20篇 |
1995年 | 24篇 |
1994年 | 27篇 |
1993年 | 13篇 |
1992年 | 11篇 |
1991年 | 19篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1984年 | 3篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有5183条查询结果,搜索用时 31 毫秒
141.
德国林业、环境保护和林业管理体制 总被引:1,自引:0,他引:1
介绍了德国:①先进的林业理论和高度发达的林业现状;②公民良好的环境保护意识和环境保护政策;③目前林业的管理体制、管理机构、管理方式以及林业政策的目标和原则。 相似文献
142.
143.
森林浴及森林浴场的开发 总被引:12,自引:2,他引:12
开展森林浴活动,既是对森林的一种新的利用途径,又能满足人们渴望“回归大自然”、休闲保健的需求。开发森林浴场具有广阔的发展前景,但必须具备一定的资源环境条件,在森林浴场的选址和项目设施建设方面,也必须综合考虑森林浴的保健、休闲旅游功能。 相似文献
144.
Tomo’omi Kumagai Koichiro Kuraji Hironori Noguchi Yuri Tanaka Katsunori Tanaka Masakazu Suzuki 《Journal of Forest Research》2001,6(4):257-264
Environmental factors, such as global solar radiation, wind speed, air temperature, humidity, and CO2 concentration, were measured above and within the canopy of a tropical rainforest in Lambir Hills National Park, Sarawak,
Malaysia. Few data concerning the environment of this forest have been reported. Intensive observations were carried out in
1998, 1999, and 2000 with the following results: (1) The fraction of global solar radiation reaching the upper layer of the
canopy varied with global solar radiation above the canopy. Even though the global solar radiation above the canopy fluctuated,
the fraction of that reaching the lower canopy and the ground was constantly approximately 5%. (2) The fraction of wind speed
reaching each layer of the canopy increased with wind speed above the canopy. Little wind was usually present at the lower
canopy. (3) The daytime air temperature at the canopy top was higher than that near the ground. The maximum difference between
the air temperature at the canopy top and that at the ground was about 5°C, and the diurnal temperature ranges at the canopy
top and those at the ground were about 8°C and about 5°C, respectively. The highest daytime water vapor pressure occurred
within the canopy and particularly near the ground. Vertical gradients of water vapor pressure during the day were steep,
probably because of high transpiration. (4) In the 1998 observation the minimum and the maximum CO2 concentrations were 360 ppm in the day and 450 ppm at night, while in the 2000 observation the minimum and the maximum CO2 concentrations were 350 ppm in the day and 540 ppm at night. The higher CO2 concentration in the daytime and the lower concentration at night observed during the 1998 observation period were probably
due to reduced photosynthesis and soil respiration caused by exceptional dry conditions during the observation period. 相似文献
145.
Smallholder perceptions of agroforestry projects in Panama 总被引:7,自引:1,他引:7
The potential effects of agroforestry systems on conservation and development have been well documented. Panama has seen a
substantial rise in the number of projects with an agroforestry component in the 1990s. There has been insufficient research
on the actual impacts of these projects on smallholders and of farmers' attitudes towards these systems. This study explores
the perceived socioeconomic and environmental impacts of five agroforestry projects in Panama. A total of 68 smallholders
were administered semi-structured interviews. In addition, 13 agroforestry experts from NGOs, government departments and research
institutes were interviewed, and their responses were compared with those of the smallholders. While the projects led to an
increase in the standard of living by providing wood products and fruit for domestic consumption, farm income levels generally
remained unchanged. This was due primarily to limited market development, the lack of marketing organizations and poor access
roads. In terms of environmental impacts, the farmers' responses suggested a slight decline in slash-and-burn agriculture,
and an increase in tree planting activities. Some environmental benefits were observed by farmers, including reduced soil
erosion, increased soil fertility, and improved quality and quantity of water sources. Nevertheless, slash-and-burn agriculture
was still the norm for the majority of farmers. Most farmers continued to harvest wood from primary and secondary growth to
meet their domestic wood requirements, rather than relying on trees planted in agroforestry projects. The main obstacles preventing
increased agroforestry adoption included insufficient agroforestry extension, inappropriate project design or management (such
as top-down management approaches, and the use of food incentives), smallholders' economic constraints, and larger policy
issues. Recommendations are proposed to improve project design and management, and to address the economic and policy constraints.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
146.
旅游解说牌示规划设计方法与技术探讨 总被引:7,自引:0,他引:7
针对目前我国旅游景区管理人员对旅游解说牌示的价值、规划方法与技术认识不深的现实,在旅游解说规划中充分体现人本主义的思想下,结合景区旅游解说资源的特性与游客特征,分析出旅游解说牌示规划与设计应包括规划阶段、设计阶段、建造阶段、评估与保持等4个阶段和组建解说队伍、清查解说资源、决定解说目标、选择牌示类型、选择牌示材料、连接对象与文本、确定牌示文本、确定牌示尺度、选择印刷方式、评估解说牌示与保持解说牌示等11个具体步骤. 相似文献
147.
论西藏的生态建设与保护对策 总被引:1,自引:0,他引:1
巴桑罗布 《中南林业调查规划》2005,24(3):10-13,24
阐述了西藏生态建设与保护事业的发展历程,分析了西藏生态建设面临的主要矛盾,提出相应的对策建议. 相似文献
149.
指出了建设项目竣工环境保护验收监测,是建设项目竣工环境保护验收的主要技术依据。以某医疗废物集中处理工程为例,分析了其工艺流程、环保设施运行情况和相应主要污染物及其排放情况、验收监测评价标准、环境管理检查、验收监测结果,提出了验收建议,以期为该行业建设项目验收工作提供参考。 相似文献
150.
刘志坚 《绿色中国(A版)》2005,(20):50-51
排污权交易是一种基于市场的环境污染间接控制制度。微观上,排污权的交易有利于企业以最小的成本费用解决排污问题和提高企业投资污染控制设施的积极性;宏观上,排污权的交易有利于降低整个社会控制环境总成本和实现资源优化配置。有赖于市场机制的排污权交易制度的实施需要一定的前提和条件。 相似文献