全文获取类型
收费全文 | 33612篇 |
免费 | 437篇 |
国内免费 | 302篇 |
专业分类
安全科学 | 1201篇 |
废物处理 | 1586篇 |
环保管理 | 4964篇 |
综合类 | 4906篇 |
基础理论 | 8781篇 |
环境理论 | 15篇 |
污染及防治 | 8108篇 |
评价与监测 | 2366篇 |
社会与环境 | 2194篇 |
灾害及防治 | 230篇 |
出版年
2023年 | 174篇 |
2022年 | 303篇 |
2021年 | 364篇 |
2020年 | 240篇 |
2019年 | 292篇 |
2018年 | 541篇 |
2017年 | 567篇 |
2016年 | 853篇 |
2015年 | 631篇 |
2014年 | 981篇 |
2013年 | 2782篇 |
2012年 | 1179篇 |
2011年 | 1570篇 |
2010年 | 1269篇 |
2009年 | 1332篇 |
2008年 | 1609篇 |
2007年 | 1536篇 |
2006年 | 1384篇 |
2005年 | 1228篇 |
2004年 | 1167篇 |
2003年 | 1102篇 |
2002年 | 1047篇 |
2001年 | 1161篇 |
2000年 | 845篇 |
1999年 | 538篇 |
1998年 | 422篇 |
1997年 | 428篇 |
1996年 | 452篇 |
1995年 | 524篇 |
1994年 | 456篇 |
1993年 | 396篇 |
1992年 | 423篇 |
1991年 | 387篇 |
1990年 | 358篇 |
1989年 | 353篇 |
1988年 | 321篇 |
1987年 | 277篇 |
1986年 | 281篇 |
1985年 | 281篇 |
1984年 | 305篇 |
1983年 | 293篇 |
1982年 | 316篇 |
1981年 | 259篇 |
1980年 | 196篇 |
1979年 | 194篇 |
1978年 | 189篇 |
1977年 | 147篇 |
1975年 | 143篇 |
1973年 | 168篇 |
1972年 | 148篇 |
排序方式: 共有10000条查询结果,搜索用时 372 毫秒
311.
A. Raman 《Die Naturwissenschaften》1967,54(21):560-560
312.
David L.Findlay 《Ambio-人类环境杂志》2003,32(3):190-195
人们普遍推测控制SO2排放可以促进加拿大、美国和欧洲的酸化淡水湖泊的恢复.本文研究了1998~2000年间靠近安大略省基拉尼公园的22个湖泊(pH值范围4.5~7.7)的浮游生物群落变化,将结果与安大略省西北的实验湖泊区(ELA)人工酸化(pH值从6.7降至4.5)又恢复(pH升至6.0)的南302号湖的数据进行了对比,以评价酸化后的恢复效果.根据历史记录,基拉尼地区数个湖泊的pH值由先前酸化的5.0~5.5反弹到6.0.浮游生物量与pH不相关,但其物种的丰富度与pH值间呈显著相关.将所得到的物种多样性数据与历史数据加以组合,可观察到其中6个湖泊中的恢复轨迹.相关分析表明:pH值得到提高后,其中几个湖泊的浮游生物群落开始向中性环境中的典型群落转化. 相似文献
313.
314.
315.
The importance of selenium as an essential trace element has progressively emerged during the last years due to the analysis of selenium deficiency diseases and to the identification and characterization of a number of selenoenzymes. Selenium is incorporated in the catalytic site of the enzymes as an integral selenocysteine residue. The pathway of selenocysteine biosynthesis and incorporation has been elucidated recently for Escherichia coli. This article presents an overview on these subjects and describes the mechanisms which confer selenocysteine specificity in the framework of protein biosynthesis. In addition, some considerations concerning the phylogeny of selenocysteine incorporation are presented and a model for the evolution of the selenocysteine pathway is proposed. 相似文献
316.
The Science of Nature - 相似文献
317.
Land use as a mitigation strategy for the water-quality impacts of global warming: a scenario analysis on two watersheds in the Ohio River Basin 总被引:4,自引:0,他引:4
This study uses an integrative approach to study the water-quality impacts of future global climate and land-use changes. In this study, changing land-use types was used as a mitigation strategy to reduce the adverse impacts of global climate change on water resources. The climate scenarios were based on projections made by the Intergovernmental Panel on Climate Change (IPCC) and the United Kingdom Hadley Centre's climate model (HadCM2). The Thornthwaite water-balance model was coupled with a land-use model (L-THIA) to investigate the hydrologic effects of future climate and land-use changes in the Ohio River Basin. The land-use model is based on the Soil Conservation Service's curve-number method. It uses the curve number, an index of land use and soil type, to calculate runoff volume and depth. The ArcView programming language, Avenue, was used to integrate the two models into a geographic information system (GIS). An output of the water-balance model, daily precipitation values adjusted for potential evapotranspiration, served as one of the inputs into the land-use model. Two watersheds were used in the present study: one containing the city of Cincinnati on the main stem of the Ohio River, and one containing the city of Columbus on a tributary of the Ohio River. These cities represent two major metropolitan areas in the Ohio River Basin with different land uses experiencing different rates of population growth. The projected hypothetical land-use changes were based on linear extrapolations of current population data. Results of the analyses indicate that conversion from agricultural land use to low-density residential land use may decrease the amount of surface runoff. The land-use practices which generate the least amount of runoff are forest, low-density residential, and agriculture; whereas high-density residential and commercial land-use types produce the highest runoff. The hydrologic soil type present was also an important factor in determining the amount of runoff and non-point-source pollution. A runoff-depth matrix and total nitrogen matrix were created for Cincinnati and Columbus to describe possible land-use mitigation measures in response to global climate change. The differences in Cincinnati and Columbus were due to differences in geographic location, air temperature, and total runoff. The results of this study may be useful to planners and policy makers for defining the possible impacts of future global climate and land-use changes on water resources. 相似文献
318.
319.
320.