全文获取类型
收费全文 | 16485篇 |
免费 | 104篇 |
国内免费 | 59篇 |
专业分类
安全科学 | 260篇 |
废物处理 | 1071篇 |
环保管理 | 2209篇 |
综合类 | 1974篇 |
基础理论 | 4844篇 |
环境理论 | 3篇 |
污染及防治 | 3051篇 |
评价与监测 | 1472篇 |
社会与环境 | 1713篇 |
灾害及防治 | 51篇 |
出版年
2023年 | 30篇 |
2022年 | 43篇 |
2021年 | 54篇 |
2020年 | 59篇 |
2019年 | 74篇 |
2018年 | 1669篇 |
2017年 | 1618篇 |
2016年 | 1411篇 |
2015年 | 246篇 |
2014年 | 168篇 |
2013年 | 425篇 |
2012年 | 698篇 |
2011年 | 1722篇 |
2010年 | 1058篇 |
2009年 | 936篇 |
2008年 | 1286篇 |
2007年 | 1689篇 |
2006年 | 252篇 |
2005年 | 318篇 |
2004年 | 239篇 |
2003年 | 319篇 |
2002年 | 363篇 |
2001年 | 176篇 |
2000年 | 139篇 |
1999年 | 104篇 |
1998年 | 93篇 |
1997年 | 93篇 |
1996年 | 78篇 |
1995年 | 84篇 |
1994年 | 84篇 |
1993年 | 72篇 |
1992年 | 58篇 |
1991年 | 67篇 |
1990年 | 79篇 |
1989年 | 50篇 |
1988年 | 50篇 |
1987年 | 37篇 |
1986年 | 28篇 |
1985年 | 44篇 |
1984年 | 57篇 |
1983年 | 53篇 |
1982年 | 52篇 |
1981年 | 43篇 |
1980年 | 28篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1974年 | 20篇 |
1972年 | 21篇 |
1967年 | 23篇 |
1966年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
A Simulation of Temporal and Spatial Variations in Carbon at Landscape Level: A Case Study for Lake Abitibi Model Forest in Ontario,Canada 总被引:2,自引:0,他引:2
Xiaolu Zhou Changhui Peng Qing-Lai Dang Jiaxin Chen Sue Parton 《Mitigation and Adaptation Strategies for Global Change》2007,12(4):525-543
Using a case study of the Lake Abitibi Model Forest (LAMF), this study aims to assess the temporal and spatial variability
in carbon storage during 1990–2000, and to present a comprehensive estimation of the carbon budget for LAMF's ecosystems.
As well, it provided the information needed by local forest managers to develop ecological and carbon-based indicators and
monitor the sustainability of forest ecosystems. Temporal and spatial carbon dynamics were simulated at the landscape level
using ecosystem model TRIPLEX1.0 and Geographical Information System (GIS). The simulated net primary productivity (NPP) and
carbon storage in forest biomass and soil were compared with field data and results from other studies for Canada's boreal
forests. The results show that simulated NPP ranged from 3.26 to 3.34 tC ha−1 yr−1 in the 1990s and was consistent with the range measured during the Boreal Ecosystem-Atmosphere Studies (BOREAS) in central
Canada. Modeled NPP was also compared with the estimation from remote sensing data. The density of total above-and belowground
biomass was 125.3, 111.8, and 106.5 tC ha−1 for black spruce, trembling aspen, and jack pine in the LAMF ecosystem, respectively. The total carbon density of forested
land was estimated at 154.4 tC ha−1 with the proportion of 4:6 for total biomass and soil. The analysis of net carbon balance of ecosystem suggested that the
LAMF forest ecosystem was acting as a carbon sink with an allowable harvest in the 1990s. 相似文献
105.
本文主要研究了肯尼亚姆瓦彻湾(属于浅潮滩红树林湿地)泥沙交换的动力机制.该港湾属于半日潮,大、小潮的潮差分别为.2m和1.4m,大潮高水位的水面面积为17km2. 相似文献
106.
In angiosperms, archesporial cells in the anther primordium undergo meiosis to form haploid pollen, the sole occupants of anther sacs. Anther sacs are held together by a matrix of parenchyma cells, the connective tissue. Cells of the connective tissue are not known to differentiate. We report the differentiation of parenchyma cells in the connective tissue of two Gordonia species into pollen-like structures (described as pseudopollen), which migrate into the anther sacs before dehiscence. Pollen and pseudopollen were distinguishable by morphology and staining. Pollen were tricolpate to spherical while pseudopollen were less rigid and transparent with a ribbed surface. Both types were different in size, shape, staining and surface architecture. The ratio of the number of pseudopollen to pollen was 1:3. During ontogeny in the connective tissue, neither cell division nor tetrad formation was observed and hence pseudopollen were presumed to be diploid. Only normal pollen germinated on a germination medium. Fixed preparations in time seemed to indicate that pseudopollen migrate from the connective tissue into the anther sac. 相似文献
107.
108.
109.
Mitigation and adaptation synergy in forest sector 总被引:1,自引:1,他引:1
N. H. Ravindranath 《Mitigation and Adaptation Strategies for Global Change》2007,12(5):843-853
Mitigation and adaptation are the two main strategies to address climate change. Mitigation and adaptation have been considered
separately in the global negotiations as well as literature. There is a realization on the need to explore and promote synergy
between mitigation and adaptation while addressing climate change. In this paper, an attempt is made to explore the synergy
between mitigation and adaptation by considering forest sector, which on the one hand is projected to be adversely impacted
under the projected climate change scenarios and on the other provide opportunities to mitigate climate change. Thus, the
potential and need for incorporating adaptation strategies and practices in mitigation projects is presented with a few examples.
Firstly, there is a need to ensure that mitigation programs or projects do not increase the vulnerability of forest ecosystems
and plantations. Secondly, several adaptation practices could be incorporated into mitigation projects to reduce vulnerability.
Further, many of the mitigation projects indeed reduce vulnerability and promote adaptation, for example; forest and biodiversity
conservation, protected area management and sustainable forestry. Also, many adaptation options such as urban forestry, soil
and water conservation and drought resistant varieties also contribute to mitigation of climate change. Thus, there is need
for research and field demonstration of synergy between mitigation and adaptation, so that the cost of addressing climate
change impacts can be reduced and co-benefits increased. 相似文献
110.