全文获取类型
收费全文 | 2234篇 |
免费 | 137篇 |
国内免费 | 384篇 |
专业分类
安全科学 | 124篇 |
废物处理 | 18篇 |
环保管理 | 323篇 |
综合类 | 1218篇 |
基础理论 | 266篇 |
环境理论 | 6篇 |
污染及防治 | 102篇 |
评价与监测 | 101篇 |
社会与环境 | 340篇 |
灾害及防治 | 257篇 |
出版年
2024年 | 4篇 |
2023年 | 36篇 |
2022年 | 66篇 |
2021年 | 98篇 |
2020年 | 84篇 |
2019年 | 99篇 |
2018年 | 87篇 |
2017年 | 98篇 |
2016年 | 97篇 |
2015年 | 69篇 |
2014年 | 101篇 |
2013年 | 162篇 |
2012年 | 159篇 |
2011年 | 162篇 |
2010年 | 93篇 |
2009年 | 103篇 |
2008年 | 118篇 |
2007年 | 140篇 |
2006年 | 120篇 |
2005年 | 112篇 |
2004年 | 101篇 |
2003年 | 84篇 |
2002年 | 74篇 |
2001年 | 87篇 |
2000年 | 84篇 |
1999年 | 64篇 |
1998年 | 46篇 |
1997年 | 37篇 |
1996年 | 37篇 |
1995年 | 34篇 |
1994年 | 26篇 |
1993年 | 16篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有2755条查询结果,搜索用时 450 毫秒
961.
In this paper, a real options based binominal lattices model for the investment of coal bed methane (CBM) is conducted. CBM prices and market demand are incorporated into the model as the predominant uncertain factors and it is solved by using the bidimensional binominal lattices approach. Then the model is employed to evaluate the investment in CBM projects in China, and the effect of related policies is analyzed. The empirical results demonstrate that the model can be used to offer a better explanation of why the CBM industry has developed slowly in China from an investment perspective. It is found that the current policy environment is not positive enough to attract investment in the CBM industry. Among various factors, CBM prices yield the most significant effect on stimulating investment in CBM development. Increasing the price subsidy is also an effective policy to stimulate investment and promote the development of the CBM industry in China. 相似文献
962.
南景毓 《中国环境管理干部学院学报》2013,(6):44-47
我国能源就地转化的概念虽已有两个定义,但它们没有完全反映能源就地转化本身所具有的内在特点和发展的必然趋势。通过对之进行深入研究,从能源就地转化扩大资源地能源与能源转化设备消费内需、调整资源地与能源消费地的经济结构、转变其经济增长方式、增强资源地的发展能力、缓解我国的能源运输压力和缩小我国地域间发展差距6个方面对之予以完善。 相似文献
963.
China is the second largest emitter of greenhouse gases (GHG) in the world, with potentially about two thirds of total Certified Emission Reductions (CERs) for Asia on the world carbon market (). Since 68% of its primary energy is from coal, China's average energy intensity is 7.5 times higher than the EU and 4.3 times higher than the US (EU, 2003). Therefore, introducing advanced clean technologies and management to China represents opportunities for Annex I countries to obtain low-cost CERs through CDM projects, and access to one of the largest potential energy conservation markets in the world. CDM can provide a win-win solution for both China and Annex I countries, and the Chinese government considers that the introduction of CDM projects can bring advanced energy technologies and foreign investment to China, thereby helping China's sustainable economy and generating CERs. As energy efficiency is generally low and carbon intensity is high in both China's energy supply and demand sectors, numerous options exist for cost-effective energy conservation and GHG mitigation with CDM. This paper reviews current Chinese policies and administrative and institutional settings for CDM cooperation, and discusses existing policy, institutional and other barriers in the energy market by drawing on observations and experience from previous initiatives such as Cleaner Production and energy efficiency. Some options to remove these barriers are addressed. In order to make CDM projects feasible, China's government needs to promote awareness, streamline administrative systems, and be more active in building a competitive edge in the world carbon market. 相似文献
964.
Background, Aim and Scope
Acid deposition has become a concern in south China in recent years. This phenomenon has increased to a dramatic extent with
the large use of cars and coal- fueled power plants. As a consequence, soils are becoming acidified and their element dynamics
will change. A decrease in the nutrient availability will lead to slower plant growth and maybe to a change in the forest
type with current species being replaced by new ones with less nutrient requirements. Because of these reasons, it is important
to understand how the dynamics of elements will change and what mechanism is part of the process. This knowledge is important
for modeling the acidification process and either finding ways to counter it or to predict its consequences. The primary purpose
of this study was to provide information about how the dynamics of K, Na, Ca, Mg and P are affected by acid deposition in
a typical forest in southern China.
Materials and Methods:
Experimental soils and saplings were collected directly from the monsoon evergreen broad-leaved forest in Dinghushan. All
saplings were transplanted individually into ceramic pots in August 2000 and placed in an open area near their origin site.
Pot soils were treated weekly from October, 2000 to July, 2002 with an acidic solution at pH 3.05, pH 3.52, pH 4.00 or pH
4.40, or with tap water as a control. The concentrations of SO42-, NO3-, K+, Na+, Ca2+, Mg2+ and available P and the pH were
measured in soil and leachate samples taken at different times. The sapling leaves were collected and their element concentrations
were measured at the end of the experiment.
Results:
Concentrations of soil exchangeable Ca and Mg decreased quickly over time, although only Ca showed changes with the acidic
solution treatment and soil exchangeable K was stable because of soil weathering. Leaching of K, Mg and Ca was dependent upon
the treatment acidity. Soil available P decreased slowly without any correlation with the acidity of the treatment. All the
NO3- added by the treatment was taken up by the plants, but the SO42- added accumulated in the soil.
Discussion:
Amongst the plant species, Schima superba was little affected by the treatment, the leaf P content was affected in Acmena
acuminatissima plants and Cryptocarya concinna was the most susceptible species to soil acidification, with a marked decrease
of the leaf K, Ca and Mg concentrations when the treatment acidity increased.
Conclusions:
Simulated acid deposition affected the dynamics of K, Ca and Mg in the monsoon evergreen broad-leaved forest. The dynamics
of Ca in the soil and of K, Mg and Ca in the soil leachates were affected by the acidic solution treatment. If such a soil
acidification occurs, Cryptocarya concinna will be amongst the first affected species, but Schima superba will be able to
sustain a good growth and mineral nutrition.
Recommendations and Perspectives:
Acid deposition will lead to imbalance the nutrient elements in the evergreen broad-leaved forest because of accelerated leaching
losses of soil exchangeable Ca and Mg. Measures should be developed to slow down soil acidification or nutrient decrease. 相似文献
965.
Biogeochemistry of Chinese estuarine and coastal waters: nutrients, trace metals and biomarkers 总被引:5,自引:0,他引:5
Jing Zhang 《Regional Environmental Change》2002,3(1-3):65-76
The dissolved and particulate trace metals in large and middle-sized Chinese rivers remain comparable with other less-disturbed
world systems. Levels of nutrients in Chinese rivers are high due to erosion over the drainage area and the application of
chemical fertilizers, which induces an N/P ratio up to 100–1,000. The concentrations of organic pollutants in Chinese rivers
are ranked at the lower end of those of world systems; however, pollution has been identified in coastal waters from north
to south of the country. In estuarine and coastal waters, dissolved trace metals illustrate a feature of remobilization, while
non-conservative distribution is observed, with exceptions for iron and aluminum. Particulate trace metals demonstrate a fairly
stable distribution along the salinity gradient, when the absolute concentration is normalized to reference materials. In
high-turbidity estuaries, seaward nutrient flux can be increased by a factor of 5–10. Finally, the N/P ratio approaches 10–20
at the interior of the East China Sea, indicating that in coastal regions photosynthesis changes from P to N and Si limitations.
Electronic Publication 相似文献
966.
Inrecentseveralyears ,abnormaldroughtoccursinthepartnorthernofChina .Itex ertssomeinfluenceonChina’snationaleconomyandhasarousedwideattentionfromallwalksoflife .Muchresearchindrought wetindexhasbeendonebothathomeandabroad .Theresultcanbeclassifiedintotwocategories:first,droughtindexdirectlyisdefinedbyprecipitationorothermeteorologicalfactors;second ,droughtindexisidentifiedbycalculatinggainingandlos ingoflocalwaterinaccordancewithequationofwaterbalance ,andsomealsoconsidertheim pactofdrought… 相似文献
967.
Fast economic and social changes in recent years in China have brought massive expansion, redevelopment, and restructuring
of cities. These changes offer cities the opportunity to improve environmental quality through urban green spaces (UGSs) and
to address the challenges of meeting community aspirations. This study explored peoples’ minds concerning UGSs in Guangzhou
city in south China in relation to the following: (1) knowledge and perception of 25 ecosystem services and 8 negative impacts;
(2) attitude toward site condition and management; (3) expectation of landscape design; and (4) preference ranking of venues.
A questionnaire was designed to solicit opinions from 340 respondents randomly chosen from residents living in the study area.
The results indicated widespread recognition of ecosystem services and strong support of UGS programs. Negative responses
were weakly expressed. Amelioration of urban microclimate and environmental quality were emphasized. Environmental functions
stressed in publicity programs, together with aggravating environmental problems in the city, tended to focus respondents’
attention on UGS benefits. Wildlife habitat, species conservation and other natural ecosystem services drew limited concerns.
Awareness of economic benefits was very low. Visual-landscape contributions with strong preference for naturalistic design
and recreational benefits were highlighted. Compared with other countries, Guangzhou residents were characterized by visual–scenic–recreation
orientation and pragmatic–utilitarian perception of UGSs, reflecting underlying differences in the understanding of inherent
ecosystem services of green spaces. Relevant UGS policies and practices could adopt the approaches of market survey, citizen
participation, and precision planning in order to meet increasingly mature and refined demands. Citizens’ understanding of
high-order ecosystem services could be enhanced to encourage appreciation of nature and their associated benefits. 相似文献
968.
循环经济理论及其在中国实践研究 总被引:39,自引:0,他引:39
循环经济理论在国际上尚处于探索与发展过程的过程中,本文运用系统科学和实证研究的方法,对我国循环经济理论与实践问题进行了初步分析。 相似文献
969.
Jian-Bing W Du-Ning X Xing-Yi Z Xiu-Zhen L Xiao-Yu L 《Environmental monitoring and assessment》2006,121(1-3):595-611
A total of 292 soil samples were taken from surface soil (0–20 cm) of a typical small watershed–Tongshuang in the black soil region of Heilongjiang province, northeast China in June 2005 for examining the concentration of soil organic carbon (SOC). Spatial variability of SOC in relation to topography and land use was evaluated using classical statistics, geostatistics and geographic information system (GIS) analyses. The objective of this study was to provide a scientific basis for land management targeting at improving soil quality in this region. Classical statistical analysis results indicated that the variability of SOC was moderate (C
V = 0.30). Slope position and land use types were discriminating factors for its spatial variability. Geostatistics analyses showed that SOC had a strong spatial autocorrelation, which was mainly induced by structural factors. Mean concentration of SOC in surface soil was 2.27% in this watershed, which was a very low level in the northern black soil region of northeast China. In this small watershed, present soil and water conservation measures played an important role in controlling soil loss. But SOC's restoration was unsatisfactory. Nearly three-quarters of the area had worrisome productivity. How to improve SOC concentration targeting at soil fertility is a pressing need in the future. 相似文献
970.
人类社会的城市化进程始终是与对水资源的开发利用同步的 ,水资源短缺将是制约城市发展的一道门槛。然而 ,在我国西部地区存在着严重的水资源短缺和难以利用的情况 ,无序的城市化又进一步恶化了本已极为严峻的水资源短缺。但城市化始终是实现西部开发的必然选择。因此 ,在实现西部大开发战略 ,推进城市化进程的过程中 ,必须通过严格控制中心城市规模 ,以控制对水资源的局部过度需求 ;通过进一步优化城镇体系布局 ,在推进城市化进程的同时 ,实现区域范围内水资源的供需平衡 ;通过对现有的城市产业结构加以调整 ,以提高水资源的利用效率。只有依靠这种适宜的城市化战略 ,才能在城市化进程中跨越水资源门槛 ,最终实现西部地区的可持续发展 相似文献