全文获取类型
收费全文 | 1704篇 |
免费 | 87篇 |
国内免费 | 166篇 |
专业分类
安全科学 | 132篇 |
废物处理 | 34篇 |
环保管理 | 354篇 |
综合类 | 537篇 |
基础理论 | 590篇 |
污染及防治 | 70篇 |
评价与监测 | 67篇 |
社会与环境 | 129篇 |
灾害及防治 | 44篇 |
出版年
2024年 | 4篇 |
2023年 | 31篇 |
2022年 | 56篇 |
2021年 | 40篇 |
2020年 | 48篇 |
2019年 | 35篇 |
2018年 | 31篇 |
2017年 | 43篇 |
2016年 | 61篇 |
2015年 | 63篇 |
2014年 | 72篇 |
2013年 | 117篇 |
2012年 | 68篇 |
2011年 | 111篇 |
2010年 | 98篇 |
2009年 | 84篇 |
2008年 | 87篇 |
2007年 | 87篇 |
2006年 | 107篇 |
2005年 | 87篇 |
2004年 | 96篇 |
2003年 | 73篇 |
2002年 | 59篇 |
2001年 | 79篇 |
2000年 | 45篇 |
1999年 | 44篇 |
1998年 | 35篇 |
1997年 | 27篇 |
1996年 | 29篇 |
1995年 | 22篇 |
1994年 | 13篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1957条查询结果,搜索用时 609 毫秒
571.
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
572.
Evaluating Controlling Factors to Ali/(Ca + Mg) Molar Ratio in Acidic Soil Water, Southern and Southwestern China: Multivariate Approach 总被引:2,自引:0,他引:2
Guo JH Zhang XS Vogt RD Xiao JS Zhao DW Xiang RJ Luo JH 《Environmental monitoring and assessment》2007,129(1-3):321-329
Ali/(Ca + Mg) molar ratio in soil water has been used as an indicator to the effects of acid deposition on terrestrial ecosystems.
However, the main factors controlling this ratio have not been well documented in southern and southwestern China. In this
study, we presented the variation in inorganic aluminum (Ali) and Ali/(Ca + Mg) molar ratio in different sites and soil horizons based on two to three years monitoring data, and evaluated the
main factors controlling Ali/(Ca + Mg) molar ratio using principle component analysis (PCA) and partial least square (PLS) regression. Monitoring data
showed although Ali/(Ca + Mg) molar ratios in most soil water were lower than assumed critical 1.0, higher molar ratios were found in some soil
water at TSP and LXH site. Besides acid loading, both soil properties and soil water chemistry affected the value of Ali/(Ca + Mg) molar ratio in soil water. Partial least square (PLS) indicated that they had different relative importance in
different soil horizons. In A-horizon, soil aluminum saturation (AlS) had higher influence on Ali/(Ca + Mg) molar ratio than soil water chemistry did; higher soil aluminum saturation (AlS) led to higher Ali/(Ca + Mg) molar ratio in soil water. In the deeper horizons (i.e., B1-, B2- and BC-horizon), inorganic aluminum (Ali) in soil water had more and more important role in regulating Ali/(Ca + Mg) molar ratio. On regional scale, soil aluminum saturation (AlS) as well as cation exchange capacity (CEC) was the
dominant factor controlling Ali/(Ca + Mg) molar ratio. This should be paid enough attention on when making regional acid rain control policy in China. 相似文献
573.
Philip M. Fearnside 《Environmental management》1997,21(4):553-570
574.
575.
Phil Cottle 《Mitigation and Adaptation Strategies for Global Change》2007,12(1):181-201
The author uses his own data gleaned from over 10 years of commercial forestry insurance across the world to propose that
despite a low intrinsic fire risk across most of Southeast Asia, especially Indonesia, commercial fire losses are unacceptably
high, and could be reduced substantially within the current financial legal and political framework within which forestry
companies operate.
Opening with a statement about the dearth of forest fire loss data in the commercial sector, it is observed that the consequent
inability of general insurers to estimate the rate of fire loss leads to very low insurance participation in forestry within
Indonesia. A summary is then provided of the financial and environmental benefits of insurance participation in commercial
forestry were this situation to be changed.
A short discussion on risk perceptions is introduced to make the point that without reliable commercial forest fire loss data,
risk perceptions of fire exposure in Southeast Asia by the financial sector, including insurers, is a barrier to risk transfer
and investment. While real fire risk and perceived fire risk for Indonesia seem at present to be in agreement, the paper challenges
that this should the case.
Comparisons are made with different parts of the world with the knowledge that, in commercial terms, plantations in the low
latitudes behave similarly everywhere in terms of fire causes, fire propagation factors, and characteristics of plantation
or managed mixed forest fires. A review of the fire sizes within commercial forests is a good indicator of the efficiency
of fire management strategies, and profiles from a high fire risk territory and Indonesia are compared.
Using commercial and unidentified data the author then demonstrates that commercial growers in Indonesia have a high annual
rate of forest fire loss and may also have a significant catastrophe fire exposure. This ‘cat’ exposure is far greater than
for equivalent plantations in clearly higher fire risk environments. These conclusions are and should be discussed with forestry
companies to change attitude and investment levels.
Practical points for improved plantation fire management are made along with comments about the resources required. A parallel
discussion then reviews fire risk assessment and management by the insurers to prevent their own ‘forest fire’ losses if they
are to get further involved with the provision of Indonesian commercial forest risk transfer. The explanation of how insurers
price risk within a portfolio helps identify the specific data needed for a proper risk management strategy to be developed. 相似文献
576.
Microscale Spatial Variation in Forest Litter Phytotoxicity 总被引:1,自引:0,他引:1
The spatial variation (within a 100 × 100 m plot) in the pollution of forest litter with heavy metals (Cu, Cd, Pb, and Zn), its acidity, and phytotoxicity (measured by the results of the root test using seedlings from a genetically homogeneous sample of common dandelion (Taraxacum officinale s.l.) have been estimated. Forest litter has been sampled in three zones differing in the toxic impact of long-term polymetal pollution by emissions from a copper-smelting plant emissions in the Middle Urals. The phytotoxicity variation is maximum in a moderately polluted plot, where both very high and very low pollution levels were observed, which determines a substantially nonlinear dose–effect relationship. The litter phytotoxicity is mainly accounted for by exchangeable forms of metals. Biological testing of samples from the most polluted plot has demonstrated marked antagonism between heavy metals and acidity. 相似文献
577.
阐述了营造生物防火林带是阻隔林火蔓延、实现"绿色防火"的主要措施,对保障森林资源安全、减少森林灾害的损失将发挥积极作用. 相似文献
578.
Reduced emissions of acidifying pollutants have changed the acidification process, and as a result, forest soils and surface
waters are slowly recovering in Sweden. However, model calculations show that some areas may never recover completely unless
further measures, such as liming, are undertaken. Liming of surface waters (lakes, rivers and wetlands) has been successfully
practised in Sweden since the 1970s, but repeated treatments are necessary. A full recovery of acidified lakes and streams
without frequent liming is however not possible until soil acidification is reversed in the most strongly affected areas.
In this study, the recovery of acidified streams was examined using ‘the total catchment approach’ i.e. treatment of both
recharge and discharge areas. The aim was to compare the quantitative effect of different treatments on run off chemistry
and the recovery of brown trout. Catchments in southwest Sweden were treated with a combination of 2 tons of wood ash and
4, 6 or 12 tons of crushed limestone per hectare in 1998/1999. Treatment of both recharge and discharge areas resulted in
fast and significant changes in stream water quality, e.g. increased concentrations of calcium, higher pH and ANC and a decreased
concentration of inorganic aluminium. The initial changes were dependent on the distribution of the applied lime between discharge
and recharge areas rather than the average dose on the total catchment. Treatment of recharge areas only, resulted in smaller
but still significant effects on calcium, pH and ANC in stream water. Furthermore, there was an initial leaching of nitrate
but it was only minor compared with the elevated leaching that occurs after a clear-cut. As a result of the treatments, brown
trout is now successfully reproducing.
Olle Westling (deceased). 相似文献
579.
580.
/ The Itapiranga Sustainable Logging Plan provides an example of how Brazil's licensing system functions for logging companies in the state of Amazonas. Two questions need to be dealt with: "How sustainable can logging in the Amazon be?" and "What and how effective are existing legal mechanisms to deal with logging projects?" The environmental impact assessment (EIA) and environmental impact statement (EIS, known as the RIMA in Brazil), present relatively detailed accounts of biodiversity and the need to adopt conservation strategies to protect it. However, social and health impacts are only superficially addressed. The economic sustainability of the operation over multiple cycles is not demonstrated. The multidisciplinary teams responsible for the EIA and EIS (RIMA) reports are hired by the project proponent, an arrangement inherently carrying the risk of biasing the result. Logging reduces biodiversity, releases greenhouse gases and inflicts social and health costs. These impacts reduce the ability of Amazonian forests to provide environmental services and to supply food and livelihood security to local populations. The reports inflate positive effects such as employment: the estimated number of jobs was cut by more than half in a revision made after the EIA and EIS (RIMA) had been approved. Not only do the reports need to be more realistic in assessing both positive and negative consequences of proposed projects, but better means are needed to ensure that promised mitigatory measures are enforced in practice. Many of the lessons that can be drawn from the Itapiranga Plan are not unique to logging projects and apply to licensing of development activites generally in Brazil and elsewhere. 相似文献