首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2467篇
  免费   14篇
  国内免费   14篇
安全科学   51篇
废物处理   152篇
环保管理   212篇
综合类   293篇
基础理论   553篇
环境理论   3篇
污染及防治   841篇
评价与监测   209篇
社会与环境   175篇
灾害及防治   6篇
  2023年   20篇
  2022年   69篇
  2021年   49篇
  2020年   28篇
  2019年   44篇
  2018年   75篇
  2017年   64篇
  2016年   111篇
  2015年   69篇
  2014年   121篇
  2013年   220篇
  2012年   144篇
  2011年   201篇
  2010年   132篇
  2009年   118篇
  2008年   140篇
  2007年   135篇
  2006年   111篇
  2005年   97篇
  2004年   74篇
  2003年   69篇
  2002年   64篇
  2001年   61篇
  2000年   41篇
  1999年   22篇
  1998年   16篇
  1997年   12篇
  1996年   6篇
  1995年   18篇
  1994年   20篇
  1993年   11篇
  1992年   15篇
  1991年   10篇
  1990年   9篇
  1989年   6篇
  1988年   6篇
  1985年   4篇
  1983年   5篇
  1982年   3篇
  1965年   3篇
  1964年   3篇
  1963年   4篇
  1962年   4篇
  1960年   3篇
  1958年   5篇
  1957年   2篇
  1956年   2篇
  1949年   2篇
  1940年   3篇
  1920年   2篇
排序方式: 共有2495条查询结果,搜索用时 140 毫秒
991.
Following the detection of 236U in depleted uranium (DU) ammunition used during the Balkans conflict in the 1990s, concern has been expressed about the possibility that other nuclides from the nuclear fuel cycle and, in particular, transuranium nuclides, might be present in this type of ammunition. In this paper, we report the results of uranium and plutonium analyses carried out on a depleted uranium penetrator recovered from a target site in southern Serbia. Our data show the depleted nature of the uranium and confirm the presence of trace amounts of plutonium in the penetrator. The activity concentration of (239+240)PU, at 45.4+/-0.7 Bq kg(-1), is the highest reported to date for any penetrator recovered from the Balkans. This concentration, however, is comparable to that expected to be present naturally in uranium ores and, from a radiological perspective, would only give rise to a very small increase in dose to exposed persons compared to that from the DU itself.  相似文献   
992.
993.
994.
This contribution determines the coastal erosion risk of Necochea and Quequén cities, Necochea Municipality, Buenos Aires Province (Argentina). Both risk components, hazard and vulnerability, were assessed by the construction of indices. The hazard index is composed of four indicators: the erosion or accretion rate, coastal geomorphology, storm waves effects, and sediment supply. The vulnerability index is comprised of land use/cover, demographic, life conditions, and work and consumption indicators, and includes population census data such as demographic, education, health, sanitary, economic, production, work and population exposure aspects. The analysis concluded that coastal erosion risk ranges from very low to high along the study area, Quequén yielding the highest values. Risk levels vary in both cities based on the uneven spatial distribution of hazard. The risk assessment developed herein constitutes a practical and adequate tool that can be utilized with other elements and tasks in the elaboration of a coastal management program.  相似文献   
995.
996.
997.
The environment provides many necessary services for a plethora of human activities related to that are being acknowledged as our ecosystems degrade; therefore, ecosystem-based solutions are becoming increasingly more important. Hydrologic restorations (HRs) apply this type of ecosystem approach; there are multiple examples around the Mediterranean area executed since the beginning of the twentieth century. One good example of these restoration-type solutions can be seen in the badlands of Saldaña (Palencia, Spain). This case has been particularly successful in stopping gully erosion from badlands. Despite its importance for the well-being of the inhabitants of Saldaña and surroundings, the economic effects of these services which were put into place by this HR have never been assessed. In the present study, four different and compatible ecosystem restored services have been valued in monetary terms. For their aggregation, an innovative approach has been taken using the analytic hierarchy process methodology, so the weight of each ecosystem service (ES) can be determined. The economic flow of these ESs has been calculated in terms of annual income and updated values, from which natural capital increase in the population of Saldaña can be assessed. After analysing the results, it can be concluded that the village has earned more than seven million euros, which, in turn, generates important benefits to its inhabitants.  相似文献   
998.
In this paper, we explored how aridity influences the regional deforestation and land-use patterns (i.e. crops/pastures) in South American Dry Chaco. To do this, we contrasted land use during last decade (2001–2012) with a spatially explicit aridity index, which we complemented with a crop water balance model. Land-use classifications were performed by considering the temporal variability of NDVI from MODIS satellites, showing that 40 and 60% of deforested land was assigned to crops and pastures, respectively. Results indicate that although the regional deforestation pattern was not associated with the aridity gradient, with drier areas similarly deforested as wetter areas, contrasting differences were observed in the use of this land, with crops mostly located (90%) in wetter areas and pastures evenly distributed across the whole aridity gradient. This research highlighted the strong effect of water limitations on the land-use option after deforestation and may help to set the basis for future land-use planning policies.  相似文献   
999.
Reversed phase thin layer chromatography (RPTLC) has been investigated for the estimation of octanol/water partition coefficients (P), an important parameter for the prediction of the environmental behaviour of organic chemicals. A strong correlation between P derived from the traditional octanol/water system and RPTLC has been established over five orders of magnitude. RPTLC data are likewise correlated to results obtained by high performance chromatography (HPLC). Due to the low costs, simplicity and separation power RPTLC is especially suited for the investigation and screening of mixtures of compounds before more complicated tests are involved.

Results from a round robin test on the determination of partition coefficients by HPLC, RPTLC and the batch method indicate the simplicity and accuracy of the RPTLC technique. Applications of the RPTLC‐technique on technical products and industrial waste waters are described.  相似文献   
1000.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号