全文获取类型
收费全文 | 850篇 |
免费 | 41篇 |
国内免费 | 95篇 |
专业分类
安全科学 | 38篇 |
废物处理 | 12篇 |
环保管理 | 128篇 |
综合类 | 402篇 |
基础理论 | 155篇 |
污染及防治 | 77篇 |
评价与监测 | 161篇 |
社会与环境 | 9篇 |
灾害及防治 | 4篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 8篇 |
2021年 | 19篇 |
2020年 | 22篇 |
2019年 | 16篇 |
2018年 | 13篇 |
2017年 | 20篇 |
2016年 | 33篇 |
2015年 | 28篇 |
2014年 | 32篇 |
2013年 | 52篇 |
2012年 | 34篇 |
2011年 | 46篇 |
2010年 | 34篇 |
2009年 | 36篇 |
2008年 | 34篇 |
2007年 | 34篇 |
2006年 | 46篇 |
2005年 | 25篇 |
2004年 | 27篇 |
2003年 | 38篇 |
2002年 | 20篇 |
2001年 | 21篇 |
2000年 | 26篇 |
1999年 | 25篇 |
1998年 | 23篇 |
1997年 | 17篇 |
1996年 | 15篇 |
1995年 | 22篇 |
1994年 | 33篇 |
1993年 | 19篇 |
1992年 | 20篇 |
1991年 | 19篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有986条查询结果,搜索用时 265 毫秒
341.
Null models reveal preferential sampling, spatial autocorrelation and overfitting in habitat suitability modelling 总被引:2,自引:0,他引:2
Bea Merckx Maaike SteyaertAnn Vanreusel Magda VincxJan Vanaverbeke 《Ecological modelling》2011,222(3):588-597
Nowadays, species are driven to extinction at a high rate. To reduce this rate it is important to delineate suitable habitats for these species in such a way that these areas can be suggested as conservation areas. The use of habitat suitability models (HSMs) can be of great importance for the delineation of such areas. In this study MaxEnt, a presence-only modelling technique, is used to develop HSMs for 223 nematode species of the Southern Bight of the North Sea. However, it is essential that these models are beyond discussion and they should be checked for potential errors. In this study we focused on two categories (1) errors which can be attributed to the database such as preferential sampling and spatial autocorrelation and (2) errors induced by the modelling technique such as overfitting, In order to quantify these adverse effects thousands of nulls models were created. The effect of preferential sampling (i.e. some areas where visited more frequenty than others) was investigated by comparing model outcomes based from null models sampling the actual sampling stations and null models sampling the entire mapping area (Raes and ter Steege, 2007). Overfitting is exposed by a fivefold cross-validation and the influence of spatial autocorrelation is assessed by separating test and training sets in space. Our results clearly show that all these effects are present: preferential sampling has a strong effect on the selection of non-random species models. Crossvalidation seems to have less influence on the model selection and spatial autocorrelation is also strongly present. It is clear from this study that predefined thresholds are not readily applicable to all datasets and additional tests are needed in model selection. 相似文献
342.
平原河网地区农村生活污染入河机制 总被引:1,自引:0,他引:1
以太滆运河流域前黄镇和雪堰镇为研究区,设计农村生活非点源污染调查问卷,采用随机抽样的方法,调查了39个行政村中85个自然村的农村生活污染情况。通过对问卷的统计分析得到了厕所使用类型的比例、化粪池中上清液和固体残渣的去向以及生活垃圾处置等信息。在对农村生活污染进行分类的基础上,估算出该地区农村生活污染入河系数为:CODCr,6.6%~13.3%;TN,18.1%~18.6%;TP,8.2%~12.5%。 相似文献
343.
Timothy H. Robinson John M. Melack 《Journal of the American Water Resources Association》2013,49(4):793-809
Nitrate and phosphate export coefficient models were developed for coastal watersheds along the Santa Barbara Channel in central California. One approach was based on measurements of nutrient fluxes in streams from specific land use classes and included a watershed response function that scaled export up or down depending on antecedent moisture conditions. The second approach for nutrient export coefficient modeling used anthropogenic nutrient loading for land use classes and atmospheric nutrient deposition to model export. In an application of the first approach to one watershed, the nitrate and phosphate models were within 20% of measured values for most storms. When applied to another year, both nitrate and phosphate models generally performed adequately with annual, storm‐flow, and base‐flow values within 20% of measured nutrient loadings. Less satisfactory results were found when applied to neighboring watersheds with difference percentages of land use and hydrologic conditions. Application of the second approach was less successful than the first approach. 相似文献
344.
345.
346.
347.
在沙尘暴应急监测方法研究中,通过对总悬浮颗粒物采样仪器及各种采样参数的研究确定和降尘采样器的研制,制定出沙尘暴应急监测方法。 相似文献
348.
349.
350.
北京市民居室内气态多环芳烃呼吸暴露评价 总被引:2,自引:0,他引:2
采用被动采样装置采集并测定北京地区38个家庭采暖期和非采暖期室内空气中的7种气态多环芳烃(PAHs)的含量.结果表明,室内气态PAHs以2、3环组分为主,7种气态PAHs的总平均浓度为100 ng/m3左右.根据实测的PAHs浓度、不同年龄段人群室内平均停留时间及其相应的呼吸速率,计算得到室内成年人(包括老人)对7种气态PAHs的潜在总暴露速率在采暖期和非采暖期分别为66 ng/h和58 ng/h;而未成年人的潜在总暴露速率则分别为56 ng/h和50 ng/h. 相似文献