全文获取类型
收费全文 | 732篇 |
免费 | 31篇 |
国内免费 | 160篇 |
专业分类
安全科学 | 133篇 |
废物处理 | 28篇 |
环保管理 | 62篇 |
综合类 | 360篇 |
基础理论 | 89篇 |
污染及防治 | 153篇 |
评价与监测 | 26篇 |
社会与环境 | 34篇 |
灾害及防治 | 38篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 29篇 |
2021年 | 27篇 |
2020年 | 23篇 |
2019年 | 26篇 |
2018年 | 27篇 |
2017年 | 33篇 |
2016年 | 26篇 |
2015年 | 27篇 |
2014年 | 33篇 |
2013年 | 47篇 |
2012年 | 46篇 |
2011年 | 55篇 |
2010年 | 54篇 |
2009年 | 53篇 |
2008年 | 57篇 |
2007年 | 55篇 |
2006年 | 41篇 |
2005年 | 29篇 |
2004年 | 25篇 |
2003年 | 32篇 |
2002年 | 26篇 |
2001年 | 24篇 |
2000年 | 27篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 13篇 |
1996年 | 11篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1983年 | 1篇 |
排序方式: 共有923条查询结果,搜索用时 15 毫秒
891.
选取南盘江流域3个水文站52 a(1961~2012年)的逐月径流资料,联合两个相邻站点,分别计算标准化径流指数(SSFI),运用游程理论识别52 a来不同站点干旱特征,并用Pair copula函数计算不同站点的联合重现期。结果表明:(1)52 a来3个站点干旱特征值的最大值都出现在2011~2012年;从单个站点看,52 a来沾益站的干旱次数、最大干旱历时、最大干旱烈度均大于高谷马站和江边街站,最大干旱峰值出现在江边街站;从联合站点看,中游以上高谷马站和沾益站的干旱特征值均大于中游以下高谷马站和江边街站,3个站点联合识别的干旱特征值大于中下游站点联合识别干旱特征值,小于中上游站点联合识别干旱特征值,上游干旱更严重;(2)Frank Pair copula函数的RMSE、AIC和BIC值最小,拟合程度最高,适合运用于南盘江流域干旱频率分析中;(3)运用Frank Pair copula函数计算得到3个水文站点2009~2012年的连续干旱重现期都在100~200 a,是52 a来最严重的一次干旱 相似文献
892.
893.
894.
895.
Possible alkylation of inorganic Hg(II) by photochemical processes in the environment 总被引:1,自引:0,他引:1
Contamination of surface waters by pesticides continues to be the focus of concern for water authorities due to the growing evidence of their deleterious effects on aquatic life. In this context, the present work investigates the occurrence of 16 selected pesticides belonging to the classes of triazines, phenylureas, organophosphates, chloroacetanilides and thiocarbamates in surface waters from the Llobregat River (NE Spain) and some of its tributaries (Anoia and Rubí) and assesses their potential impact on the aquatic organisms by applying a recently developed index, the Short-term Pesticide Risk Index for the Surface Water System (PRISW-1), which takes into account the pesticides concentrations and their overall toxicity against three aquatic organisms (algae, Daphnia, and fish). Chemical analysis, performed by means of a fully automated method based on isotope dilution on-line solid phase extraction-liquid chromatography-electrospray-tandem mass spectrometry (on-line SPE-LC-ESI-MS/MS), revealed diuron and diazinon as the most ubiquitous and abundant compounds with levels up to 818 and 132 ng L−1, respectively. Total pesticide concentrations, which in only 1 out of 66 samples surpassed 500 ng L−1, were higher in the tributaries than in the river but their contribution in terms of mass-loads to the overall pesticide pollution of the Llobregat River was relatively small. Contamination increased downstream of the river and was clearly influenced by rainfall and hence river flow. Application of the PRISW-1 index indicated that, although pesticides levels fulfilled the European Union Environmental Quality Standards (EQS) for surface waters, the existing pesticide contamination poses a low to high ecotoxicological risk for aquatic organisms, that algae and macro-invertebrates are at higher risk than fish, and that the organophosphates diazinon and malathion and the phenylurea diuron are the major contributors to the overall toxicity and therefore the most problematic compounds. 相似文献
896.
Brassinosteroid alleviates phenanthrene and pyrene phytotoxicity by increasing detoxification activity and photosynthesis in tomato 总被引:4,自引:0,他引:4
The present study was carried out to investigate the effects of exogenously applied 24-epibrassinolide (BR) on growth, gas exchange, chlorophyll fluorescence characteristics, lipid peroxidation and antioxidant systems of tomato seedlings grown under different levels (0, 10, 30, 100 and 300 μM) of phenanthrene (PHE) and pyrene (PYR) in hydroponics. A concentration-dependent decrease in growth, photosynthetic pigment contents, net photosynthetic rate (Pn), stomatal conductance (Gs), maximal quantum yield of PSII (Fv/Fm), effective quantum yield of PSII (ΦPSII), photochemical quenching coefficient (qP) has been observed following PHE and PYR exposure. By contrast, non-photochemical quenching coefficient (NPQ) was increased. PHE was found to induce higher stress than PYR. However, foliar or root application of BR (50 nM and 5 nM, respectively) alleviated all those depressions with a sharp improvement in the activity of photosynthetic machinery. The activities of guaicol peroxidase (GPOD), catalase (CAT), ascorbate peroxidase (APX) and glutathione reductase (GR) as well as content of malondialdehyde (MDA) were increased in a dose-dependent manner under PHE or PYR treatments. Compared with control the highest increments of GPOD, CAT, APX, GR and MDA by PHE/PYR alone treatments were observed following 300 μM concentration, which were 67%, 87%, 53%, 95% and 74% by PHE and 42%, 53%, 30%, 86% and 62% by PYR, respectively. In addition, both reduced glutathione (GSH) and oxidized glutathione (GSSG) were induced by PHE or PYR. Interestingly, BR application in either form further increased enzymatic and non enzymatic antioxidants in tomato roots treated with PHE or PYR. Our results suggest that BR has an anti-stress effect on tomato seedlings contaminated with PHE or PYR and this effect is mainly attributed by increased detoxification activity. 相似文献
897.
Seasonal variations of CH(4) and N(2)O emissions in response to water management of paddy fields located in Southeast China 总被引:2,自引:0,他引:2
Water management is one of the most important practices that affect methane (CH4) and nitrous oxide (N2O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH4 and N2O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH4 and N2O emissions from paddy fields were very clear. The peaks of CH4 emissions from the CI paddies were observed 1-2 d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH4 emission was observed in a short period after re-flooding. N2O emissions peaks from CI paddies were all observed 8-10 d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N2O emissions, whereas no substantial N2O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH4 emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N2O emissions were increased by 135.4% on the average. The integrative global warming potential of CH4 and N2O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH4 and N2O emissions from paddy fields while ensuring the rice yield. 相似文献
898.
研究河流中污染物的输移扩散及其影响因素,引入死区预警模型及其解析解,模拟污染物在水体中的时空变化,进而预测污染物到达下游特定地点的浓度值及相应时间.实例模拟结果,尤其是对下游断而污染物最大浓度值及其出现时间的预测结果较好,表明建立的模型能够较准确地模拟河流中污染物的输移扩散规律.本研究可为环境风险管理及突发性环境污染应急预案的制定提供科学依据. 相似文献
899.
900.