全文获取类型
收费全文 | 43281篇 |
免费 | 773篇 |
国内免费 | 4704篇 |
专业分类
安全科学 | 1646篇 |
废物处理 | 2040篇 |
环保管理 | 4990篇 |
综合类 | 12376篇 |
基础理论 | 9809篇 |
环境理论 | 16篇 |
污染及防治 | 12461篇 |
评价与监测 | 2533篇 |
社会与环境 | 2143篇 |
灾害及防治 | 744篇 |
出版年
2023年 | 325篇 |
2022年 | 820篇 |
2021年 | 747篇 |
2020年 | 520篇 |
2019年 | 588篇 |
2018年 | 888篇 |
2017年 | 973篇 |
2016年 | 1189篇 |
2015年 | 1169篇 |
2014年 | 1687篇 |
2013年 | 3793篇 |
2012年 | 1908篇 |
2011年 | 2380篇 |
2010年 | 1881篇 |
2009年 | 1938篇 |
2008年 | 2112篇 |
2007年 | 2021篇 |
2006年 | 1846篇 |
2005年 | 1439篇 |
2004年 | 1330篇 |
2003年 | 1424篇 |
2002年 | 1299篇 |
2001年 | 1539篇 |
2000年 | 1200篇 |
1999年 | 957篇 |
1998年 | 726篇 |
1997年 | 684篇 |
1996年 | 731篇 |
1995年 | 677篇 |
1994年 | 588篇 |
1993年 | 534篇 |
1992年 | 501篇 |
1991年 | 457篇 |
1990年 | 448篇 |
1989年 | 423篇 |
1988年 | 382篇 |
1987年 | 308篇 |
1986年 | 278篇 |
1985年 | 298篇 |
1984年 | 308篇 |
1983年 | 302篇 |
1982年 | 343篇 |
1981年 | 279篇 |
1980年 | 251篇 |
1979年 | 274篇 |
1978年 | 246篇 |
1977年 | 214篇 |
1976年 | 213篇 |
1974年 | 212篇 |
1973年 | 191篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
61.
Evolution of environmental impact assessment as applied to watershed modification projects in Canada
Herman J. Dirschl Nicholas S. Novakowski M. Husain Sadar 《Environmental management》1993,17(4):545-555
This article reviews the application of environmental impact assessment (EIA) procedures and practices to three watershed
modification projects situaled in western Canada. These ventures were justified for accelerating regional economic development,
and cover the period during which public concerns for protecting the environment rapidly made their way into the national
political agenda. An historical account and analysis of the situation, therefore, seems desirable in order to understand the
development of EIA processes, practices, and methodologies since the start of construction of the first project in 1961. This
study concludes that there has been good progress in predicting and evaluating environmental and related social impacts of
watershed modification proposals. However, a number of obstacles need to be overcome before EIA can firmly establish itself
as an effective planning tool. These difficulties include jurisdictional confusions and conflicts, division of authority and
responsibility in designing and implementing appropriate mitigative and monitoring measures, lack of tested EIA methodologies,
and limited availability of qualified human resources. A number of conclusions and suggestions are offered so that future
watershed modification proposals may be planned and implemented in a more environmentally sustainable fashion. These include:
(1) EIA processes must be completed before irrevocable decisions are made. (2) Any major intrusion into a watershed is likely
to impact on some major components of the ecosystem(s). (3) Mitigation costs must form part of the benefit-cost analysis of
any project proposal. (4) Interjurisdictional cooperation is imperative where watersheds cross political boundaries. (5) The
EIA process is a public process, hence public concerns must be dealt with fairly. (6) The role of science in the EIA process
must be at arms length from project proponents and regulators, and allowed to function in the interest of the protection of
the environment and public health and safety.
The views expressed here are the authors’ own and do not necessarily reflect those of FEARO and/or other government agencies
and officials involved in the review of these projects. 相似文献
62.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
63.
Changes in the survival parameters of the red fox were analyzed at different phases of the population cycle. It was found that the survival rate in all age classes, including newborns, drastically increased at the phase of population growth. The relationship between the general mortality rate and population size was determined. A hypothesis concerning the mechanism of these changes in the general mortality rate is suggested. 相似文献
64.
The effect of mountain relief and industrial air pollution on biometric parameters of pine stands was studied. The empirical–statistical models of the dependence of biometric characteristics on the parameters of forest sites were developed using raster modeling and multivariate analysis. The possibility of predicting changes in the biometric parameters at any site on the basis of these models is shown. 相似文献
65.
V. I. Kolmakov N. A. Gaevskii E. A. Ivanova O. P. Dubovskaya I. V. Gribovskaya E. S. Kravchuk 《Russian Journal of Ecology》2002,33(2):97-103
In the periods of summer and autumn bloom of the Stephanodiscus hantzschii Crun. in recreational water bodies, studies on the vertical distribution of chlorophyll a, its contents per unit biomass, efficiency in using photosynthetically active radiation (EPhAR), and assimilative activity of microalgae were performed. The results confirmed the existence of two ecophysiological forms of St. hantzschii and provided evidence that both forms are typically autotrophic and can efficiently use low-intensity PhAR for photosynthesis. 相似文献
66.
67.
In situ assessment of modification of sediment properties by burrowing invertebrates 总被引:4,自引:0,他引:4
Benthic organisms can significantly alter the physical properties of marine sediments, but it has hitherto been difficult to assess and quantify the effects of bioturbation. In situ geophysical techniques offer new methods for measuring these effects: measurement of acoustic shear-wave velocity and electrical resistivity allows nondestructive assessment of the properties of the grain framework and pore-fluid matrix, respectively, of the seabed sediment. The influence of burrowing invertebrates on the structural properties of sandy sediments at intertidal locations on the coast of Wales (UK) was investigated during the periol 1986–1987 using these techniques. Three species (Arenicola marina, Corophium arenarium and Lanice conchilega) were selected on the basis of their contrasting styles of burrow construction. All three species produced measurable and significant, although different, changes in bed properties. They modified shear-wave propagation through the bed by changing bed rigidity: while A. marina and C. arenarium decreased rigidity by creating open burrows, L. conchilega increased rigidity by building shell-lined tubes. All produced a decrease in electrical resistivity by altering porosity and/or tortuosity, which implies an increase in permeability; these changes were attributable not only to the presence of the burrows but also to modification of the between-burrow sediment texture and bed properties. 相似文献
68.
Cardiac anomalies may occur in isolation or can be part of a genetic syndrome. In this article, we describe some of the genetic syndromes commonly associated with cardiac anomalies where there are other sonographic features that may aid accurate prenatal diagnosis. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
69.
Zhang Jing Feng Zhiming Yang Yanzhao 《中国人口.资源与环境(英文版)》2006,4(2):33-40
The article puts forward the process and means of regional water and land balance research, and then from two scenarios which are the balances under natural regulation and human intervention, calculated and analysed the balance between water and land on Ningxia Plain. For the balance under natural regulation named farmland water balance, using farmland water resource balance equation, the research estimated the monthly farmland" water balance of 8 major crops for all of the 12 counties on Ningxia Plain in the period of 1960-2001; for the balance under human intervention, the research estimated land-use water balance equation of the counties in 2000, and calculated the balance between land use and water resources including irrigating water of all the 12 counties on Ningxia Plain. Results showed that ①precipitation can not meet the water demand of the crops for growth and development on Ningxia Plain, and water shortage is the primary character of farmland water balance under natural regulation. ②the diversity of water and land balance of different counties is distinctly influenced by the crop structure, water quantity for irrigation and irrigation level. ③Irrigation water could meet the crop water demand on Ningxia Plain in 2000, but there was not much space to expand irrigating cultivated land. 相似文献
70.