全文获取类型
收费全文 | 6101篇 |
免费 | 21篇 |
国内免费 | 58篇 |
专业分类
安全科学 | 535篇 |
废物处理 | 140篇 |
环保管理 | 561篇 |
综合类 | 2127篇 |
基础理论 | 1053篇 |
环境理论 | 3篇 |
污染及防治 | 1047篇 |
评价与监测 | 315篇 |
社会与环境 | 378篇 |
灾害及防治 | 21篇 |
出版年
2022年 | 42篇 |
2021年 | 69篇 |
2019年 | 42篇 |
2018年 | 73篇 |
2017年 | 67篇 |
2016年 | 97篇 |
2015年 | 67篇 |
2014年 | 128篇 |
2013年 | 386篇 |
2012年 | 135篇 |
2011年 | 198篇 |
2010年 | 149篇 |
2009年 | 183篇 |
2008年 | 177篇 |
2007年 | 201篇 |
2006年 | 152篇 |
2005年 | 128篇 |
2004年 | 278篇 |
2003年 | 294篇 |
2002年 | 199篇 |
2001年 | 186篇 |
2000年 | 102篇 |
1999年 | 82篇 |
1998年 | 83篇 |
1997年 | 57篇 |
1996年 | 37篇 |
1995年 | 115篇 |
1994年 | 87篇 |
1993年 | 77篇 |
1992年 | 75篇 |
1991年 | 67篇 |
1990年 | 86篇 |
1989年 | 69篇 |
1988年 | 62篇 |
1987年 | 61篇 |
1986年 | 47篇 |
1985年 | 49篇 |
1984年 | 40篇 |
1983年 | 56篇 |
1982年 | 41篇 |
1981年 | 48篇 |
1979年 | 39篇 |
1976年 | 39篇 |
1919年 | 56篇 |
1918年 | 51篇 |
1917年 | 37篇 |
1916年 | 62篇 |
1915年 | 43篇 |
1914年 | 78篇 |
1913年 | 111篇 |
排序方式: 共有6180条查询结果,搜索用时 171 毫秒
451.
In this paper, a mechanical filtering system to treat pig slurry is proposed. The filter was made from the aerobic decomposition product of the organic fraction of municipal wastes and wheat straw was used as the support.Using a pilot plant to treat 2100 liters of swine slurry, an adequate reduction in BOD5; COD, and other parameters was obtained. The organic matter content of the material trapped in the filter was similar to that of compost and farmyard manure, but the nitrogen and phosphorous levels and the C/N ratio were more similar to farmyard manure. After passing through a filtering system, the treated liquid can be used for fertirrigation and as a feed for algae ponds. After a period of stabilization, the solid material can be mixed to produce manure. Although wheat straw was used as the support in this experiment, other agricultural wastes such as rice straw, corn stalks, millet stems, banana, cotton, and coconut trash can be used. Rather than municipal solid waste compost, other kinds of compost obtained from agricultural wastes such as leaves, bark, husks, etc., can be used as the filter. 相似文献
452.
Adesoji O. Adelaja Robin G. Brumfield 《Journal of Agricultural and Environmental Ethics》1991,4(1):82-88
Many state governments in the United States promote locally-produced farm products. This paper discusses issues related to the ethics and equity of such promotional programs. The paper argues that generic promotion is generally easier to justify in terms of ethics and equity than brand promotion. It also argues that informative and factual brand promotions are easier to justify than deceptive and persuasive brand promotions. Additional equity issues arising when taxpayers finance state-promotional programs are also discussed. 相似文献
453.
454.
Dr Abdal‐Majeed I. Daghistani BA MSc PhD MRTPI 《Journal of Environmental Planning and Management》1991,34(1):2-9
The towns and cities of Saudi Arabia have been subjected to sustained growth pressures since the transformation of the country's economy following the discovery of oil in the Eastern Province of the Kingdom. The rapid growth which has been experienced has created major problems for the central and local government agencies responsible for planning and managing urban growth. The experience of Jeddah, one of the major cities in Saudi Arabia, is described and the problems of planning and managing its growth are analysed. Weaknesses relating to the structure of the planning system are identified, as are major difficulties in relation to the quality and quantity of professional staff. Recent attempts to improve the operation of the planning system are described and evaluated. 相似文献
455.
Saud A. Amer Timothy O. Keefer Mark A. Weltz David C. Goodrich Leslie B. Bach 《Journal of the American Water Resources Association》1994,30(1):69-83
ABSTRACT: Certain physical and chemical properties of soil vary with soil water content. The relationship between these properties and water content is complex and involves both the pore structure and constituents of the soil solution. One of the most economical techniques to quantify soil water content involves the measurement of electrical resistance of a dielectric medium that is in equilibrium with the soil water content. The objective of this research was to test the reliability and accuracy of fiberglass soil-moisture electrical resistance sensors (ERS) as compared to gravimetric sampling and Time Domain Reflectometry (TDR). The response of the ERS was compared to gravimetric measurements at eight locations on the USDA-ABS Walnut Gulch Experimental Watershed. The comparisons with TDR sensors were made at three additional locations on the same watershed. The high soil rock content (≥45 percent) at seven locations resulted in consistent overestimation of soil water content by the ERS method. Where rock content was less than 10 percent, estimation of soil water was within 5 percent of the gravimetric soil water content. New methodology to calibrate the ERS sensors for rocky soils will need to be developed before soil water content values can be determined with these sensors. 相似文献
456.
The Neebing-McIntyre floodway in Thunder Bay, Ontario, Canada, has been constructed with a relatively straight and uniform trapezoidal channel, compared with the prechannelized sinuous reaches of the Neebing and the McIntyre rivers. The flow regime of the floodway also contrasts significantly with the prechannelized regime, because of the combination of discharges from these rivers into a new channel and the regulation of flows by a diversion structure. The maximum channel capacity of the floodway is about 284 m3 s–1 (175-year regional flood), compared with about 40 m3 s–1 and 60 m3 s–1, respectively, for the Neebing and the McIntyre. According to regime theories, the construction of a straight and trapezoidal channel has upset the equilibrium of the stream system and therefore should lead to some accelerated erosion and sedimentation processes in the new channel immediately after construction. Erosion potential is particularly high during higher discharge events, when flow velocities are expected to be greater than the prechannelized velocities of the Neebing and the McIntyre. The overall sediment yield of the watershed is low (71t km–2 yr–1), compared with other documented watersheds of North America, but the rates of deposition in the floodway are relatively high, mainly due to the backwater effect of Lake Superior. Unless maintained by constant channel work, the floodway will tend to fill up with sediment, until a postconstructional equilibrium is reestablished. 相似文献
457.
Dr. Hana L. Ayala 《Environmental management》1987,11(2):141-147
We are witnessing a growing concern with the global dimension of many environmental issues, reflected in the increase in the number and significance of international environmental organizations. Yet there is no internationally applicable strategy for environmental research which is management oriented. A new type of research policy, which integrates ideas derived from environmental and human ecology, is required in order to deal with cultural and ecological diversity and their interactions as reflected in the ecology of landscapes. The newly defined concept of environmental health is proposed to fill this gap. This concept integrates the latest developments in landscape evolutionary ecology and environmental health, bringing out a conflict between making the environment conducive to human health and increasing the available options for supporting the essential biological and ecological processes of the environment. Lessons derived from the evolution of human environments are used in order to illustrate how health may become un umbrella for developing an environmental research policy, which could also serve as a catalyst for international environmental projects. 相似文献
458.
459.
In the last ten years official location policy in Nigeria for urban roadside traders, an enterprising group of urban poor operating at the lowest level of the informal sector of the economy has been very negative. Government believes that they should be removed from the streets and tucked away in obscure locations because of their tendency to deface the streets with litter and for causing vehicular and pedestrian traffic congestion. This paper identifies and assesses the magnitude of pollution created by the traders as a prelude to evolving a planning policy and strategy for regulating and formally accommodating street traders in good locations while still ensuring good environmental quality. 相似文献
460.