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   20137篇
  免费   1653篇
  国内免费   4663篇
安全科学   2660篇
废物处理   394篇
环保管理   2838篇
综合类   12168篇
基础理论   2371篇
环境理论   14篇
污染及防治   2162篇
评价与监测   990篇
社会与环境   1816篇
灾害及防治   1040篇
  2024年   130篇
  2023年   473篇
  2022年   679篇
  2021年   732篇
  2020年   683篇
  2019年   654篇
  2018年   621篇
  2017年   832篇
  2016年   992篇
  2015年   975篇
  2014年   995篇
  2013年   1348篇
  2012年   1601篇
  2011年   1724篇
  2010年   1215篇
  2009年   1138篇
  2008年   927篇
  2007年   1347篇
  2006年   1378篇
  2005年   1051篇
  2004年   862篇
  2003年   952篇
  2002年   781篇
  2001年   648篇
  2000年   604篇
  1999年   576篇
  1998年   432篇
  1997年   344篇
  1996年   295篇
  1995年   253篇
  1994年   269篇
  1993年   221篇
  1992年   171篇
  1991年   127篇
  1990年   88篇
  1989年   54篇
  1988年   46篇
  1987年   24篇
  1986年   22篇
  1985年   33篇
  1984年   16篇
  1983年   19篇
  1982年   18篇
  1981年   14篇
  1980年   11篇
  1979年   13篇
  1978年   9篇
  1977年   13篇
  1973年   10篇
  1971年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
土壤锑污染对桑树的影响初探   总被引:1,自引:0,他引:1  
运用盆栽实验和实验分析方法,研究了土壤锑(Sb)污染对桑叶品质的影响,揭示了桑树对土壤锑的耐性机制。在土壤中分别添加三价锑15mg/kg、40mg/kg、80mg/kg、120mg/kg、160mg/kg和300mg/kg,以植物生长指标及生理指标为测试指标,实验周期60d。实验结果表明,低浓度Sb处理(<40mg/kg)对桑树生长有促进作用;随着土壤Sb浓度增高(40—300mg/kg),它对桑树产生抑制效应。但当土壤锑浓度不超过160mg/kg时,桑树对土壤锑污染有一定的耐性,其耐性指数>0.8。土壤锑污染对桑叶叶绿素含量、淀粉含量和可溶性糖含量影响不显著,桑叶中的锑含量随土壤锑含量的增加而增多。  相似文献   
92.
区域分工对区域经济发展具有重要作用。山东地处我国东部沿海,是全国人口大省、经济大省,在全国经济发展格局中占有举足轻重的地位。根据区域分工理论,对山东省在全国和区域内部分工进行了分析,揭示了山东省在全国的区际地位以及所辖17个市之间的区域分工与合作格局,为山东省强化区域分工和联系,提高区域竞争力提供决策依据。  相似文献   
93.
旅游循环经济理念下的珠江源旅游区建设初探   总被引:1,自引:0,他引:1  
旅游循环经济是发展旅游业一种新的指导思想,是实现旅游业可持续发展的新范式。针对珠江源旅游区的现状,根据旅游循环经济资源循环利用和保护并重的理念,探讨其在旅游区的林地系统利用建设、湿地系统利用建设、岩溶地貌系统利用建设、旅游服务设施系统利用建设方面的应用。  相似文献   
94.
Abstract: Natural forests in southern China have been severely logged due to high human demand for timber, food, and fuels during the past century, but are recovering in the past decade. The objective of this study was to investigate how vegetation cover changes in composition and structure affected the water budgets of a 9.6‐km2 Dakeng watershed located in a humid subtropical mountainous region in southern China. We analyzed 27 years (i.e., 1967‐1993) of streamflow and climate data and associated vegetation cover change in the watershed. Land use/land cover census and Normalized Difference of Vegetation Index (NDVI) data derived from remote sensing were used to construct historic land cover change patterns. We found that over the period of record, annual streamflow (Q) and runoff/precipitation ratio did not change significantly, nor did the climatic variables, including air temperature, Hamon’s potential evapotranspiration (ET), pan evaporation, sunshine hours, and radiation. However, annual ET estimated as the differences between P and Q showed a statistically significant increasing trend. Overall, the NDVI of the watershed had a significant increasing trend in the peak spring growing season. This study concluded that watershed ecosystem ET increased as the vegetation cover shifted from low stock forests to shrub and grasslands that had higher ET rates. A conceptual model was developed for the study watershed to describe the vegetation cover‐streamflow relationships during a 50‐year time frame. This paper highlighted the importance of eco‐physiologically based studies in understanding transitory, nonstationary effects of deforestation or forestation on watershed water balances.  相似文献   
95.
Effective EU and Member State policies for stimulating CCS   总被引:1,自引:0,他引:1  
Although CO2 capture and storage (CCS) is widely recognised as an option to mitigate climate change, consistent and effective EU policies to advance CCS are still absent. This paper discusses policy instruments for advancing large-scale deployment of CCS in the European Union, and evaluates them in a multi-criteria analysis. The EU Emissions Trading Scheme (EU-ETS) is a cost-effective instrument for limiting greenhouse gas emissions, but it is questionable whether its currently limited time horizon and short-trading periods will lead to substantial CCS diffusion. Complementary policies at the EU and the Member State level may repair this and provide sufficient incentives for CCS. Potential policies include financial instruments such as investment subsidies, a feed-in scheme, or a CO2 price guarantee, as well as a CCS mandate or a low-carbon portfolio. These policy options differ with respect to their environmental effectiveness, possible interaction with the EU-ETS, costs and financial risk involved, and their competition with other mitigation options. Interactions between Member State policies and the EU-ETS are smaller in scope than those of EU-wide policies, but they are more likely to lead to displacement of financial resources from other low-carbon technologies. In addition, national policies may pose a significant part of the financial risk of CCS operations with Member States, reducing the operator's incentive to innovate. Overall, structural policies at the EU level, such as a mandate or a low-carbon portfolio standard would be more conducive for realising large-scale deployment of CCS across the EU as well as more acceptable to environmental organisations.  相似文献   
96.
97.
Impacts on industry of Europe's emerging chemicals policy REACh   总被引:1,自引:0,他引:1  
For Europe, a new regime in chemicals regulation is about to start. After the proposal of the European Commission concerning the Registration, Evaluation and Authorization of Chemicals (REACh) passed its readings in the European Parliament and some differences with the European Council of Ministers were resolved, the regulation will come into force in June 2007. This paper is focused on the question how serious the cost burdens for industry induced by REACh will be, and whether the New European Member States (NMS) which joined the European Union in May 2004 will be able to cope with the regulation. This evaluation has been done by assessing the legislative, administrative and economic framework in New Member States and by analysing real business cases in companies. The empirical showcase business impact studies are at the same time of interest for companies of EU-15 states, other European countries who may implement the regulation, and even for exporters of raw materials and chemicals outside Europe, who will also have to comply with REACh if they market in the European Community. The results give no indications that REACh adoption will bring significant drawbacks to companies in the NMS. The emerging regulation will bring challenges for individual companies, especially for small and medium-sized ones, but for the European chemical industry as a whole, there is no question that it will be able to cope with REACh burdens without losing its global competitiveness.  相似文献   
98.
As the embodiment of human activities, the change of regional industrial structure is an essential driving factor of global environmental change. Consequently, the research on the change of regional industrial structure and associated effects on the environment is one of the key issues of researches on sustainable development, human–environment relationship, and regional response to global environment change. However, compared to the flourish of researches on environmental impact assessment of industrial departments, few studies have been conducted to assess the environmental impact of regional industrial structure. In this study, based on a synthetic analysis of environmental disturbances of different industrial departments, the environmental impact coefficient of industrial department associated with the index of environmental impact of industrial structure was constructed, so as to make a quantitative assessment of environmental impact of the change of regional industrial structure. And the results of the case study in Lijiang City, a rural region of China, have showed that there are two obvious changes of industrial structure in the study area from 1992 to 2003, associated with a continuous decreasing of the index of environmental impact of industrial structure, which indicated a positive environmental effects of the change of regional industrial structure.  相似文献   
99.
柚树间种短期经济作物在提高柚园经济效益的同时,还可提高土壤的有机质和N、P、K养分质量分数,改善柚园小区气候,增加有机肥来源。间种物残余体作为绿肥,可显著地提高柚果产量和质量。  相似文献   
100.
土壤矿物固定态铵研究进展   总被引:2,自引:0,他引:2  
主要从土壤中粘土矿物组成、有机物质、土壤水分、Fe的氧化还原、钾素状况及土壤粘粒的不同层面电荷、净表面电荷、表面电荷均匀性等方面就土壤中固定态铵的固定机制及其对作物的有效性的影响进行了综述;并对近年来土壤中固定态铵的测定方法作一评述。  相似文献   
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