全文获取类型
收费全文 | 34718篇 |
免费 | 345篇 |
国内免费 | 226篇 |
专业分类
安全科学 | 879篇 |
废物处理 | 1432篇 |
环保管理 | 4316篇 |
综合类 | 7891篇 |
基础理论 | 8631篇 |
环境理论 | 12篇 |
污染及防治 | 8609篇 |
评价与监测 | 1979篇 |
社会与环境 | 1356篇 |
灾害及防治 | 184篇 |
出版年
2018年 | 409篇 |
2017年 | 413篇 |
2016年 | 636篇 |
2015年 | 479篇 |
2014年 | 732篇 |
2013年 | 2524篇 |
2012年 | 878篇 |
2011年 | 1248篇 |
2010年 | 1070篇 |
2009年 | 1114篇 |
2008年 | 1301篇 |
2007年 | 1339篇 |
2006年 | 1201篇 |
2005年 | 1044篇 |
2004年 | 1056篇 |
2003年 | 992篇 |
2002年 | 969篇 |
2001年 | 1276篇 |
2000年 | 897篇 |
1999年 | 552篇 |
1998年 | 422篇 |
1997年 | 438篇 |
1996年 | 432篇 |
1995年 | 510篇 |
1994年 | 493篇 |
1993年 | 452篇 |
1992年 | 450篇 |
1991年 | 446篇 |
1990年 | 487篇 |
1989年 | 461篇 |
1988年 | 396篇 |
1987年 | 365篇 |
1986年 | 362篇 |
1985年 | 346篇 |
1984年 | 415篇 |
1983年 | 371篇 |
1982年 | 421篇 |
1981年 | 382篇 |
1980年 | 321篇 |
1979年 | 346篇 |
1978年 | 298篇 |
1977年 | 262篇 |
1976年 | 243篇 |
1975年 | 246篇 |
1974年 | 270篇 |
1973年 | 285篇 |
1972年 | 254篇 |
1971年 | 250篇 |
1968年 | 231篇 |
1967年 | 261篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
The typical parameters of acid precipitation are evaluated in the forest of Vallombrosa (Tuscan Appennines) during the dry period 1988-89. Individual rain events (dry and wet deposition) were sampled in a clearing of the forest and below the canopy of an evergreen tree as well as a deciduous broadleaf tree.
In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd. 相似文献
In atmospheric precipitation the pH values usually vary around 4.4, with neutralization in the hot season due to calcareous material from distant sources. Relatively large concentrations of Pb and Cd are found in rain, but only in a small amount in canopy leachate. Aluminium, manganese and iron are more significantly washed off than Pb and Cd. 相似文献
12.
13.
14.
15.
Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones. 相似文献
16.
17.
In a 1981 survey of 436 Florida citrus growers, 27 pesticide related poisoning incidents were reported that were to have taken place within one year of the interview date. From these reports it is possible to estimate that there are 376 citrus fieldworker related poisonings per year in Florida. This number of estimated poisonings may be developed into an incidence rate of 113 fieldworker poisonings per 10,000 fieldworkers. 相似文献
18.
19.
When combined in the lining and covering of waste-containment facilities, soil and geosynthetic components protect the environment by acting as a hydraulic barrier. Equipment loading may significantly increase the tensile stress induced in geosynthetic components, leading to a potential stability problem. Large equipment loadings may also result in a localized circular slip surface during construction operations. New analytical method based on discrete element modelling is proposed for estimating the distribution of tensile force developed in the individual geosynthetic components of the lining system and for evaluating the safety factor of slope failure due to equipment loading. The analytical results of an example are presented to demonstrate the applicability of the analytical method for the lining system of a waste landfill. The analyses of the example show that equipment loading provide a substantial increase in the tensile forces of the geosynthetic components of a lining system and that the possibility of shallow failure due to equipment loading increases as the slope becomes steeper. This method is a useful tool for analysing the lining system of waste landfills with complex lining components. 相似文献
20.
In the past 20 years a variety of indices have been suggested for measuring the severity of trauma, however none of them meets the requirement of being a simple and objective instrument that can be utilized efficiently by lay persons and providers of health services without previous experience in triaging. A new system has been proposed which meets this requirement and which has been validated with 197 injured persons at the emergency ward of the Valle University Hospital in Call, Colombia. The instrument showed a high level of concordance with the conventional triaging method and classifies victims into four categories: critical with recovery unlikely, critical but recoverable, moderately serious, and ambulatory. There is discussion on the reliability of this instrument and it is recommended that it be validated with victims from larger disasters. Regardless, it has the advantage of being specific and free of the subjectivity that characterizes other indices. 相似文献