全文获取类型
收费全文 | 6462篇 |
免费 | 544篇 |
国内免费 | 2798篇 |
专业分类
安全科学 | 151篇 |
废物处理 | 233篇 |
环保管理 | 829篇 |
综合类 | 4918篇 |
基础理论 | 2301篇 |
环境理论 | 2篇 |
污染及防治 | 657篇 |
评价与监测 | 403篇 |
社会与环境 | 203篇 |
灾害及防治 | 107篇 |
出版年
2024年 | 8篇 |
2023年 | 58篇 |
2022年 | 159篇 |
2021年 | 165篇 |
2020年 | 141篇 |
2019年 | 142篇 |
2018年 | 128篇 |
2017年 | 150篇 |
2016年 | 162篇 |
2015年 | 169篇 |
2014年 | 206篇 |
2013年 | 439篇 |
2012年 | 364篇 |
2011年 | 261篇 |
2010年 | 250篇 |
2009年 | 235篇 |
2008年 | 215篇 |
2007年 | 360篇 |
2006年 | 386篇 |
2005年 | 282篇 |
2004年 | 227篇 |
2003年 | 271篇 |
2002年 | 306篇 |
2001年 | 311篇 |
2000年 | 458篇 |
1999年 | 524篇 |
1998年 | 412篇 |
1997年 | 412篇 |
1996年 | 501篇 |
1995年 | 407篇 |
1994年 | 359篇 |
1993年 | 256篇 |
1992年 | 174篇 |
1991年 | 216篇 |
1990年 | 134篇 |
1989年 | 95篇 |
1988年 | 66篇 |
1987年 | 66篇 |
1986年 | 33篇 |
1985年 | 33篇 |
1984年 | 73篇 |
1983年 | 52篇 |
1982年 | 26篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1977年 | 7篇 |
1976年 | 27篇 |
1975年 | 33篇 |
1974年 | 11篇 |
排序方式: 共有9804条查询结果,搜索用时 15 毫秒
221.
This paper, based on the autonomy concept, continues to investigate hierarchical forms and spatial structure of ecosystems. The former can lead to limits for the selection of the component parts of an ecosystem and a distinction between its endogenous and exogenous variables; and the latter can be lead to a hypothesis of the space of an ecosystem: the space of an ecosystem = its habitat area + supporting area + impact area, and two characteristics of ecosystems, space-overlapping and the area of ecosystem space, have been further studied referring to human activities. 相似文献
222.
The effects of different aluminium chloride concentrations together with varying calciumchloride concentrations on root growth, cell division and nucleoli in root tip cells of Allium cepa werestudied. The concentrations used for aluminium chloride were 10-4, 10-3 and 10-2 mol/L ; and for calcium chloride were 10-5 , 10-4 , 10-3 and 10-2 mol/L, respectively. The results showed that after thetreatments with 10-2 to 10-3 mol/L Al3+ , root growth was severely inhibited , a large nurnber of thecells with c-mitosis were induced and the nucleolar material was extruded from the nucleus into the cytoplasm. However , the treatments with 10-2 to 10-3 mol/L of Al3+ together with 10-2)to 10-5 mol/LCa2+ suggested that Ca2+ gave the obviously protective effects against Al3+ poisoning in root growth.cell division and nucleoli of the root tip cells in A. cepa. The possible mechanism of these protective effects of Ca2+) is also briefly discussed. 相似文献
223.
In this paper it was reported that PbCl2 , CdCl2 , HgCl2, and aquatic environmental samples containing Al, Cd, Cu, Pb, Sr, Zn and other heavy metal ions as well as organic chemicals suppressed thegrowth of E. coli only at higher exposed concentrations. The stimulative effects of PbCl2 and HgCl2 on thegrowth of E. coli were clearly showed at lower concentrations and longer time. It suggested that the toxic effects of heavy metal ions and other pollutants on the growth of E. coli are variable according to the differentexposed levels. 相似文献
224.
Trace copper (II) in water can be preconcentrated using silica gel modified with 1-(2-pyridylazo)-2-naphthol (PAN) and be determined spectrophotometri-cally. The conditions for the preconcentration were studied. The method was applied to both artificial and natural water samples and the results suggest that copper (II) of ppb level in water can be measured accurately after the preconcentration. 相似文献
225.
226.
本文通过笔者的调查及对辽河近三o年水质监测数据的分析,得出了辽河新民段水生生物资源枯竭的原因是河水中溶解氧过低的结论. 相似文献
227.
ThebufferingeffectsofaquaticsedimentsagainstacidicdepositionLiaoBohan;TangHongxiao(ResearehCenterforEco-EnvironmentalSciences... 相似文献
228.
根据兖州矿区基地近6年的大气监测资料,对区域性大气质量状况进行了分析,并提出了改善大气质量的四条措施。 相似文献
229.
运用文献、调查访问、观察、实验、统计及分析等研究方法,对有、无排球技术基础学生的对比分析,探讨软式排球的健身价值。研究结果表明:软式排球较硬式排球技术更易学习掌握,更易在学生中组织比赛,有着很重要的健身价值。为使软式排球更具有健身和娱乐性,应在比赛中灵活制定比赛规则。 相似文献
230.