全文获取类型
收费全文 | 957篇 |
免费 | 197篇 |
国内免费 | 503篇 |
专业分类
安全科学 | 187篇 |
废物处理 | 23篇 |
环保管理 | 85篇 |
综合类 | 959篇 |
基础理论 | 175篇 |
污染及防治 | 89篇 |
评价与监测 | 35篇 |
社会与环境 | 58篇 |
灾害及防治 | 46篇 |
出版年
2024年 | 8篇 |
2023年 | 21篇 |
2022年 | 94篇 |
2021年 | 96篇 |
2020年 | 125篇 |
2019年 | 72篇 |
2018年 | 79篇 |
2017年 | 71篇 |
2016年 | 55篇 |
2015年 | 64篇 |
2014年 | 76篇 |
2013年 | 58篇 |
2012年 | 81篇 |
2011年 | 102篇 |
2010年 | 89篇 |
2009年 | 81篇 |
2008年 | 87篇 |
2007年 | 77篇 |
2006年 | 76篇 |
2005年 | 45篇 |
2004年 | 46篇 |
2003年 | 27篇 |
2002年 | 21篇 |
2001年 | 19篇 |
2000年 | 26篇 |
1999年 | 13篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
排序方式: 共有1657条查询结果,搜索用时 15 毫秒
81.
Chongguo Tian Jianmin Ma Liyan Liu Hongliang Jia Diandou Xu Yi-Fan Li 《Atmospheric environment (Oxford, England : 1994)》2009,43(25):3891-3901
Using a dynamic numerical atmospheric transport model for organochlorine pesticides (OCPs), the relationship between the East Asian summer monsoon and the fate of α-hexachlorocyclohexane (α-HCH), a banned OCP, in the atmosphere over Northeast Asia was investigated and assessed. The modeled temporal and spatial patterns and variability of α-HCH air concentrations during the summer months of 2005 revealed a strong link between this chemical in the atmosphere over Northeast Asia and the East Asian summer monsoon. At lower atmospheric levels, easterly and southeasterly winds blowing from relatively cold ocean surface convey α-HCH air concentration from southeast China to northeast China. A monsoon front extending from southeast China to Japan, characterized by a strong wind convergence, carried the air concentration to a high elevation of the atmosphere where it was delivered by southerly monsoon flow to northern China and North Pacific Ocean. This summer monsoon associated northward atmospheric transport caused a reversal of the soil/air exchange from outgassing to net deposition during spring–summer period. The modeled wet deposition fluxes of α-HCH agreed well with the changes in the typical summer monsoon rain bands, designated as Meiyu in China, Changma in Korea, and Baiu in Japan. The major wet deposition flux paralleled with the monsoon front as well as the monsoon rain bands. The temporal change in the fluxes exhibits abrupt northward advances, which is associated with a stepwise northward and northeastward advance of the East Asian summer monsoon. The modeled α-HCH outflow in the atmosphere from China occurs mostly in the summer months and through northeast China, featured strongly by the evolution of the summer month. This study suggests that the East Asian summer monsoon provides a major atmospheric pathway and summer outflows to α-HCH over East Asia. 相似文献
82.
Endosulfan in China 1—gridded usage inventories 总被引:9,自引:0,他引:9
Jia H Li YF Wang D Cai D Yang M Ma J Hu J 《Environmental science and pollution research international》2009,16(3):295-301
Background, aim, and scope Endosulfan, an organochlorine pesticide (OCP), is genotoxic in mammalian cells and generally considered to be toxic and classified
by the World Health Organization and the US Environmental Protection Agency as priority pollutants and a nominator for inclusion
in a future iteration of the persistent organic pollutants treaty. Endosulfan is a currently used pesticide and still being
used worldwide. The general trend of total global endosulfan use has increased continuously since the first year when this
pesticide was applied. It is critical to create national endosulfan usage/emission inventories for China to carry out source–receptor
relation analysis, risk assessment, and other research related to endosulfan in this country. Chinese inventories have been
published for some OCPs, such as technical HCH and lindane, DDT, and chlordane; for endosulfan, however, there has not been
any usage inventory available on any scales (national or provincial), although endosulfan has been widely used since 1994
in this country. This is the first part of the work. The goal of this paper is to quantify the historical production and usage
of endosulfan in China and to compile gridded historical usage inventories of endosulfan for this country. Based on these
usage inventories, emission and residue inventories will be created, which is the goal of the second part of the work.
Materials and methods Due to the lack of national production and usage information of endosulfan in China, a method to estimate the use of endosulfan
was developed. First, information of crops on which endosulfan is applied and average endosulfan use and annual application
frequencies of endosulfan on these crops were collected. Secondly, usage of endosulfan on each crop was estimated using the
national cropland area for each province from Chinese government reports. Finally, with the help of GIS (geographic information
system), the usage data of this insecticide was allocated to a grid system, with a 1/4° longitude by 1/6° latitude resolution,
with a size for each grid cell of approximately 25 km by 25 km.
Results and discussion The use of endosulfan in agriculture in China started on cotton in 1994, and on wheat, tea, tobacco, apples, and other fruits
in 1998. Endosulfan usage on cotton, wheat, tea, tobacco, and apples in China has been estimated to be approximately 25,700 t
between 1994 and 2004. The province with the highest usage of endosulfan is Henan Province, with a total usage reaching 4,000 t,
followed by the uses in Xinjiang Autonomous Region (3,200 t), Shandong Province (3,000 t), Hebei Province (2,100 t), and Anhui
Province (1,900 t). Gridded usage inventories of endosulfan at a 1/4° longitude by 1/6° latitude resolution have been created,
which indicate that the intensive endosulfan use was in the south of Hebei Province, west of Shandong Province, east of Henan
Province, north of Anhui Province, east of Jiangsu Province, and some areas in Yunnan Province and Xinjiang Autonomous Region.
General agreement has been found between the usage data from our estimation and the small amount of usage data published in
China.
Conclusions This is the first national gridded endosulfan usage inventory produced for China. The annual applications of endosulfan from
1994 to 2004 in China were estimated based on the total areas of major crops, on which endosulfan was applied, and spatial
distribution of the application was generated at provincial and prefecture levels. With the help of GIS, endosulfan usage
based on prefecture was transferred to a 1/4° longitude by 1/6° latitude gridding system. The satisfaction of the inventories
was supported by the consistence between the estimation of the annual usage and the reported annual production of endosulfan.
Recommendations and perspectives This gridded endosulfan usage inventory created in this study will be improved upon availability of new information of endosulfan.
The usage inventories can be used to create gridded emission and residue inventories for this insecticide. It is believed
that this work will pave the way for further endosulfan studies in China and beyond. 相似文献
83.
我国大多建筑施工企业目前的安全管理只局限于对施工现场的检查和整改工作,而对施工现场的整体安全性缺乏分析和有效的监控,目前安全评价技术在建筑业的运用并不成熟.运用科学的安全评价方法,对建筑施工危险性进行系统分析和研究,可以补充、完善和指导施工现场的安全管理工作. 相似文献
84.
85.
用废腈纶制备两性高分子絮凝剂的研究 总被引:1,自引:0,他引:1
为实现腈纶废料的回收利用,降低产品的生产成本,将废腈纶水解后,通过Mannich反应制得具有两性结构的聚丙烯酰胺.考察了反应条件对产物胺化度的影响,用红外光谱对产品结构进行了分析,研究了不同胺化度产品的絮凝性能.结果表明,反应时间和原料配比对产品的胺化度有较大影响.胺化度约为30%的产品在用量为7 mg/L,pH值近中性时对硅藻土悬浮液的除浊率可达95%; 与聚合氯化铝配合使用时,对实际印染废水的脱色及COD去除效果均明显优于工业聚丙烯酰胺(PAM),COD去除率可达85%. 相似文献
86.
In Canadian oil sands mining operations, bitumen is extracted from oil sands using the hot water extraction process, which produces tremendous amounts of tailings. Currently, these tailings are disposed of in large ponds, in which coarse particles settle out relatively quickly and fine particles remain suspended in water and settle very slowly. After years of settling, the fine particles form a stable suspension in water known as mature fine tailings (MFTs). Long-term storage of the MFT is costly and poses a major environmental liability.Oil sands companies are now actively investigating different approaches to replace or reduce the use of oil sands tailings ponds. Filtration of the tailings to produce “dry tailings” for stacking is now being investigated as an alternative by a number of companies. Fast water drainage is a critical step for the filtration process. In this paper, we use simple laboratory-scale filtration tests to evaluate the filterability of the oil sands tailings and to generate a parameter that can be used in filtration scale-up. It was found that the filterability of the original coarse oil sands tailings was relatively low. However, after the fines are flocculated with the coarse particles to form uniform flocs the filterability was improved by several orders of magnitude. The results demonstrate that filtration of the flocculated coarse tailings to produce the “dry” stackable tailings may be viable. 相似文献
87.
基于灰建模的瓦斯含量多变量预测模型研究 总被引:1,自引:1,他引:0
研究了GM(1,N)、GM(0,N)瓦斯含量预测模型的数学原理,收集郑煤集团告成矿地质勘探期间及生产期间的瓦斯含量实测资料,获得16个可靠点,选取基岩厚度、新生界厚度、煤层厚度、煤层水分、煤层灰分、50m顶板含砂率6个因素作灰色建模预测的指标,分别建立了GM(1,6)和GM(0,6)瓦斯含量多变量预测模型。根据计算和评价结果,GM(1,6)和GM(0,6)瓦斯含量预测模型精度均能够满足工程精度的要求,说明利用灰色模型来预测瓦斯含量是可行的。由于前者精度略高于后者,故建议告成矿采用GM(1,6)模型来进行未知地区煤层瓦斯含量的预测。需要注意,由于模型没有考虑构造的影响,在实际预测时,还应根据构造对待预测区的影响关系和影响程度对模型的预测结果进行修正。 相似文献
88.
机动车排放颗粒物成分谱对比研究 总被引:1,自引:0,他引:1
对深圳、无锡、济南和美国EPA建立的机动车排放颗粒物成分谱进行对比研究,建立的成分谱中各组分含量存在较大差别原因为使用了不同的采样方法。 相似文献
89.
90.
为解决某综放面采用顶板巷与上隅角联合抽采方式可能引起的煤自燃及瓦斯爆炸等重大安全隐患问题,采用数值模拟从瓦斯、氧气体积分数分布特点和温度场角度综合分析合理顶板巷位置与抽采流量,为协同预防瓦斯和煤自燃复合灾害提供指导。结果表明:抽采口、上隅角瓦斯体积分数随抽采流量增加而降低;抽采流量100m3/min是影响氧化带宽度变化幅度的拐点;抽采流量对采空区最高温度的影响较大,对高温范围宽度影响较小;综合确定合理顶板巷位置为内错回风巷15 m,合理抽采流量为100~150 m~3/min;现场应用表明该方案既能解决瓦斯超限问题,又能有效控制煤自燃威胁,表明数值模拟具有较好的可靠性。 相似文献