全文获取类型
收费全文 | 7283篇 |
免费 | 549篇 |
国内免费 | 2898篇 |
专业分类
安全科学 | 141篇 |
废物处理 | 264篇 |
环保管理 | 917篇 |
综合类 | 5022篇 |
基础理论 | 2647篇 |
环境理论 | 2篇 |
污染及防治 | 812篇 |
评价与监测 | 558篇 |
社会与环境 | 260篇 |
灾害及防治 | 107篇 |
出版年
2024年 | 28篇 |
2023年 | 106篇 |
2022年 | 168篇 |
2021年 | 154篇 |
2020年 | 127篇 |
2019年 | 130篇 |
2018年 | 145篇 |
2017年 | 157篇 |
2016年 | 148篇 |
2015年 | 202篇 |
2014年 | 251篇 |
2013年 | 638篇 |
2012年 | 400篇 |
2011年 | 293篇 |
2010年 | 271篇 |
2009年 | 273篇 |
2008年 | 278篇 |
2007年 | 442篇 |
2006年 | 454篇 |
2005年 | 332篇 |
2004年 | 254篇 |
2003年 | 301篇 |
2002年 | 333篇 |
2001年 | 351篇 |
2000年 | 464篇 |
1999年 | 539篇 |
1998年 | 425篇 |
1997年 | 417篇 |
1996年 | 507篇 |
1995年 | 414篇 |
1994年 | 362篇 |
1993年 | 258篇 |
1992年 | 183篇 |
1991年 | 214篇 |
1990年 | 135篇 |
1989年 | 97篇 |
1988年 | 66篇 |
1987年 | 69篇 |
1986年 | 34篇 |
1985年 | 37篇 |
1984年 | 74篇 |
1983年 | 53篇 |
1982年 | 27篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 9篇 |
1976年 | 27篇 |
1975年 | 33篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
551.
552.
553.
554.
复合污染状态下尾矿区有害化学品的迁移研究 总被引:4,自引:0,他引:4
用混合尾矿浆及尾矿渣淋溶柱,研究选矿药剂在尾矿渣及尾矿废水中的静态分布及其淋溶作用,结果表明:①选矿药剂对整个尾矿区都污染,即使是水溶性好的药剂,它们在尾矿渣中的静态分布也占有相当的比例,油溶性好的药剂多存在于尾矿渣中,尾矿污染为多种药剂的复合污染,各种药剂在尾矿渣及尾矿废水中的总浓度成倍加大;②用尾矿渣淋溶柱测得单一药剂的淋溶值:25号黑药>MIBC> CN->二号油>乙基黄药>丁基黄药>Y-89黄药.但多种药剂复合污染时,药剂的淋溶距离明显加大,其中CN-和Y-89黄药加大近一倍.复合药剂污染加大药剂的残留期,也加大它们向地下水及其它水源迁移的几率. 相似文献
555.
556.
557.
In mine water pollution abatement, it is commonly assumed that known mine waste sites are the major pollution sources, thus neglecting the possibility of significant contribution from other old and diffuse sources within a catchment. We investigate the influence of different types of pollution source uncertainty on cost-effective allocation of abatement measures for mine water pollution. A catchment-scale cost-minimization model is developed and applied to the catchment of the river Dalälven, Sweden, in order to exemplify important effects of such source uncertainty. Results indicate that, if the pollution distribution between point and diffuse sources is partly unknown, downstream abatement measures, such as constructed wetlands, at given compliance boundaries are often cost-effective. If downstream abatement measures are not practically feasible, the pollution source distribution between point and diffuse mine water sources is critical for cost-effective solutions to abatement measure allocation in catchments. In contrast, cost-effective solutions are relatively insensitive to uncertainty in total pollutant discharge from mine water sources. 相似文献
558.
Field reconnaissance of the Ebocha-8 oil spill-affected site at Obiobi/Obrikom in the Niger Delta region of Nigeria was carried out to assess the extent of damage to the terrestrial ecosystem and delimit the epicenter of oil spillage. Following three successive reconnaissance surveys, the area to be sampled was delimited (200 x 200 m2), and soil samples were collected using the grid method from three replicate quadrats at two depths, surface (0-15 cm) and subsurface (15-30 cm). A geographically similar area located 50 m adjacent to the oil-polluted area was used as a reference (control) site. Total hydrocarbon content (THC) and heavy metal concentrations were later determined in the laboratory by extraction and spetrophotemetric techniques. Generally, the THC of soils at surface and subsurface depths of the oil-polluted plots was 2.06 x 10(4) +/- 4.97 x 10(3) mg/kg and 1.67 x 10(3) +/- 3.61 x 10(2) mg/kg soil, respectively, (no overlap in standard errors at 95% confidence limit) while concentrations of heavy metals(Pb, Cd, V, Cu and Ni) were enhanced, especially at the surface. The high levels of THC and heavy metals may predispose the site, which hitherto served as arable agricultural land, to impaired fertility and possible conflagration. When concentrations of heavy metals reach the levels obtained in this study, they may become toxic to plants or possibly bio-accumulate, thus leading to toxic reactions along the food chain. While the spilled-oil may have contributed to the enhanced levels of the metals in the affected soils, physico-chemical properties of the soils, mobility of metals, and the intense rainfall and flooding that preceded the period of study may have also contributed in part to their enhanced concentrations. The presence of high hydrocarbon content may cause oxygen deprivation, which may result in the death of soil fauna by asphyxiation. There is, therefore, an urgent need to clear the affected site of these excess hydrocarbon deposits so as to enhance the rehabilitation process of the affected mat layer of soils. Other appropriate mitigating measures, such as subsequent monitoring of hydrocarbon levels at suitable intervals after the clean up activities, are also recommended, with reference to the findings of this study, for effective management of the affected area. 相似文献
559.
Grasslands were once widespread and species-rich ecosystems. They have drastically decreased throughout the world, largely due to changes in land-uses. Remnant grasslands are often highly degraded and disconnected and require active conservation. In order for grasslands to be maintained worldwide, protected areas need to be created. While adequately creating and managing protected areas has proven difficult, this can be improved by following a three-point guideline: (1) consider many ecological groups (birds, insects, plants); (2) use conservation biology knowledge; (3) seek agreements with concerned parties by comprehending elements of economy, politics and sociology. Based on the example of La Crau, a steppe area in South-eastern France, this review aims at (i) illustrating that this guideline can facilitate creating and managing protected areas and (ii) proposing improvement to the guideline while keeping it simple. In La Crau, the need for conservation was first acknowledged in 1975. Between 1983, when a request for a protection decree was made and 1990, when the first concrete protection measure was taken, 20% of the steppe disappeared. It took another 8 years to reach a concerted management plan in 1998. The review shows how using ecological guidelines would have helped better and faster protection of the steppe. Improvements to the guideline drawn from the La Crau experience include: the protection of some traditional practices; the protection of some degraded habitats that can substitute for habitats that no longer exist; the restoration of degraded habitats that do not qualify for protection; and the flexibility of the management plan. 相似文献
560.
Determining a remeasurement frequency of variables over time is required in monitoring environmental systems. This article
demonstrates methods based on regression modeling and spatio-temporal variability to determine the time interval to remeasure
the ground and vegetation cover factor on permanent plots for monitoring a soil erosion system. The spatio-temporal variability
methods include use of historical data to predict semivariograms, modeling average temporal variability, and temporal interpolation
by two-step kriging. The results show that for the cover factor, the relative errors of the prediction increase with an increased
length of time interval between remeasurements when using the regression and semivariogram models. Given precision or accuracy
requirements, appropriate time intervals can be determined. However, the remeasurement frequency also varies depending on
the prediction interval time. As an alternative method, the range parameter of a semivariogram model can be used to quantify
average temporal variability that approximates the maximum time interval between remeasurements. This method is simpler than
regression and semivariogram modeling, but it requires a long-term dataset based on permanent plots. In addition, the temporal
interpolation by two-step kriging is also used to determine the time interval. This method is applicable when remeasurements
in time are not sufficient. If spatial and temporal remeasurements are sufficient, it can be expanded and applied to design
spatial and temporal sampling simultaneously. 相似文献