全文获取类型
收费全文 | 14500篇 |
免费 | 232篇 |
国内免费 | 1942篇 |
专业分类
安全科学 | 331篇 |
废物处理 | 1094篇 |
环保管理 | 1548篇 |
综合类 | 3779篇 |
基础理论 | 3837篇 |
环境理论 | 2篇 |
污染及防治 | 3636篇 |
评价与监测 | 1178篇 |
社会与环境 | 1059篇 |
灾害及防治 | 210篇 |
出版年
2024年 | 3篇 |
2023年 | 88篇 |
2022年 | 251篇 |
2021年 | 216篇 |
2020年 | 158篇 |
2019年 | 128篇 |
2018年 | 1611篇 |
2017年 | 1579篇 |
2016年 | 1432篇 |
2015年 | 454篇 |
2014年 | 373篇 |
2013年 | 535篇 |
2012年 | 883篇 |
2011年 | 1752篇 |
2010年 | 1019篇 |
2009年 | 923篇 |
2008年 | 1238篇 |
2007年 | 1522篇 |
2006年 | 271篇 |
2005年 | 221篇 |
2004年 | 171篇 |
2003年 | 229篇 |
2002年 | 281篇 |
2001年 | 139篇 |
2000年 | 157篇 |
1999年 | 169篇 |
1998年 | 145篇 |
1997年 | 125篇 |
1996年 | 118篇 |
1995年 | 126篇 |
1994年 | 90篇 |
1993年 | 82篇 |
1992年 | 53篇 |
1991年 | 36篇 |
1990年 | 18篇 |
1989年 | 8篇 |
1988年 | 15篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 9篇 |
1981年 | 3篇 |
1973年 | 1篇 |
1935年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
本研究对兰州市不同污染区(石油化工为主、燃煤、商业及农村)在不同季节时的大气飘尘,作了对比采样.飘尘样品用溶剂抽提法提取后,用化学萃取法分离为五个有机物馏分.用毛细色谱-质谱-计算机联用系统进行了定性分析,并用毛细管色谱法进行了部分定量分析.用Ames试验(用TA1537、TA98和TA100三株菌.加与不加S-1)对其致突变活性进行了研究.并对有机致突变物在不同污染区、不同季节的变化规律及其来源进行了初步探讨. 相似文献
72.
73.
主成份分析法在大气环境质量综合评价中的应用 总被引:16,自引:1,他引:16
介绍了主成份分析法评价大气环境质量的基本原理,并对某市的大气环境质量进行了综合评价。最后,与其它方法的评价结果进行了对比分析,进一步证实了主成份分析法的科学性、合理性。 相似文献
74.
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
75.
Given the key role of biogenic volatile organic compounds(VOCs) to tropospheric chemistry and regional air quality, it is important to generate accurateVOCs emission inventories. However, only a less fraction of plant species, in temperate grassland of Inner Mongolia, has been characterized by quantitative measurements. A taxonomic methodology, which assigns VOCs measurements to unmeasured species, is an applicable and inexpensive alternation for extensive VOCs emission survey, although data are needed for additional plant families and genera to further validate the taxonomic approach in grassland vegetation. In this experiment, VOCs emission rates of 178 plant species were measured with a portable photoionization detector( PID). The results showed the most of genera and some families have consistent feature of their VOCs emission, especially for isoprene, and provide the basic premise of taxonomic methodology to develop VOCs emission inventories for temperate grassland. Then, the taxonomic methodology was introduced into assigning emission rate to other 96 species, which no measured emission rates available here. A systematical emission inventory of temperate grassland vegetation in Inner Mongolia was provided and further evidence that taxonomy relationship can serve as a useful guide for generalizing the emissions behavior of many, but not all, plant families and genera to grassland vegetation. 相似文献
76.
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
77.
在雾稳定的条件下,研究了雾滴穿过SO_2烟羽沉降到地面的过程中吸收、析解以及酸化等过程。结果表明,雾对烟羽中SO_2的清除具有某些奇特的现象。即仅在离源较远的区域才表现出有限的清除作用:而在近源区,主要以析解为主,使源附近地面SO_2浓度增加,高架源成了低架源。雾滴在地面附近的这种析解作用,是造成雾天污染物浓度高的重要原因之一。 相似文献
78.
79.
80.