全文获取类型
收费全文 | 15823篇 |
免费 | 1034篇 |
国内免费 | 2056篇 |
专业分类
安全科学 | 2359篇 |
废物处理 | 171篇 |
环保管理 | 2301篇 |
综合类 | 8162篇 |
基础理论 | 1730篇 |
环境理论 | 11篇 |
污染及防治 | 885篇 |
评价与监测 | 829篇 |
社会与环境 | 1455篇 |
灾害及防治 | 1010篇 |
出版年
2024年 | 37篇 |
2023年 | 155篇 |
2022年 | 317篇 |
2021年 | 435篇 |
2020年 | 417篇 |
2019年 | 361篇 |
2018年 | 325篇 |
2017年 | 450篇 |
2016年 | 542篇 |
2015年 | 590篇 |
2014年 | 634篇 |
2013年 | 811篇 |
2012年 | 1039篇 |
2011年 | 1183篇 |
2010年 | 863篇 |
2009年 | 863篇 |
2008年 | 707篇 |
2007年 | 1085篇 |
2006年 | 1099篇 |
2005年 | 885篇 |
2004年 | 743篇 |
2003年 | 844篇 |
2002年 | 676篇 |
2001年 | 573篇 |
2000年 | 526篇 |
1999年 | 516篇 |
1998年 | 388篇 |
1997年 | 306篇 |
1996年 | 253篇 |
1995年 | 233篇 |
1994年 | 233篇 |
1993年 | 196篇 |
1992年 | 155篇 |
1991年 | 115篇 |
1990年 | 80篇 |
1989年 | 47篇 |
1988年 | 42篇 |
1987年 | 20篇 |
1986年 | 19篇 |
1985年 | 29篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 11篇 |
1977年 | 11篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1971年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
861.
Most studies of social polygyny in birds have examined male provisioning on the basis of the number of feeding visits. This
may be misleading if males compensate for infrequent visits by bringing larger prey at each visit. We investigated nestling
provisioning in the socially polygynous great reed warbler, Acrocephalus arundinaceus, in south Central Sweden in 1996–1997. We collected data on rate of feeding visits, prey size and the amount of biomass delivered
by males and females. Males had lower rates of feeding visits and provided smaller prey to nestlings in secondary than in
monogamous and primary nests. Secondary females had higher rates of feeding visits and brought larger prey than monogamous
and primary females. These results confirm that secondary females face a potential cost of polygyny through a lower rate of
male feeding, and that this cost was reinforced by the significantly lower male provisioning rate (biomass h–1) at secondary nests. Secondary females compensated for the lack of male assistance by increasing their rate of feeding and
bringing larger prey. As a result, offspring in nests of secondary females received as much food as did those in nests of
primary females. Prey load size increased with the parent’s proportion of feeding visits, suggesting that parents use different
feeding strategies depending on their amount of responsibility for nestling provisioning. We suggest that parents which take
the main responsibility for nestling feeding have to forage further away from the nest, and based on optimal-foraging theory,
they should then on average bring larger prey to their nest.
Received: 4 April 1999 / Received in revised form: 12 October 1999 / Accepted: 23 October 1999 相似文献
862.
战略环境评价系统及工作程序 总被引:26,自引:0,他引:26
介绍了战略环境评价系统组成的五个要素 ,即评价者、评价对象、评价目的、评价标准和评价方法 ,分析了其相互关系及各要素与战略环境评价系统的关系 ,并提出了战略环境评价工作程序。 相似文献
863.
成都市城市环境与经济协调发展分析 总被引:17,自引:2,他引:15
从城市环境与经济发展的协调度方面分析了成都市1990-1997年间协调度的变化趋势,评估了成都市城市环境与经济协调发展的类型,得出了成都市属于总体协调发展类环境滞后型的结论。 相似文献
864.
文章论述了家庭生活水的氡浓度水平、生活用水对室内氡的贡献、水的使用过程中室内氡行为以及含氡水的使用与辐射照射剂量的关系等问题。指出家庭生活水的氡浓度高时,是室内氡的一个不可忽视的来源。对氡浓度特别高的家庭用水,建议先用活性炭等进行吸附后再使用。 相似文献
865.
866.
867.
868.
869.
870.
The machair sand dune systems of the Outer Hebrides of Scotland are a unique habitat, which is rare within both a global and
European context. Unusually, the machair habitat also represents an agricultural resource that is very important to the Hebridean
people, having been subject to both grazing and cultivation throughout the historical period. Following designation as an
Environmentally Sensitive Area (ESA) in 1988, the machairs of South Uist have been studied with the aim of understanding the
links between agricultural practice and their plant community and ecosystem dynamics. This research focused primarily on the
effects of cultivation practices and their role in maintaining plant species richness and community and ecosystem stability.
Within two carefully selected areas, the successional plant communities of machair at different stages of recovery following
ploughing and cultivation of cereals and potato patches or ‘lazy beds’ were identified at both a macro- and micro-level. Investigations
of the vegetation recovery processes on turves taken from newly ploughed land indicated that the initial stages of recolonization
are characterized primarily by rapid vegetative reproduction and growth, although re-vegetation by seeds is also an important
factor. The implications of these findings for the long-term management of machair plant communities are discussed and in
particular the need to maintain old cultivation practices such as shallow ploughing. The need for more detailed research into
both seed banks and seed rain and into processes of vegetative reproduction is stressed.
Nomenclature: Clapham et al. (1981) and Stace (1991, 1997) for vascular plants; Hubbard (1984) for grasses; Pankhurst & Mullin (1991) for
the regional flora; Dobson (1992) for lichens; Watson (1981) for mosses and liverworts. 相似文献