全文获取类型
收费全文 | 4692篇 |
免费 | 96篇 |
国内免费 | 73篇 |
专业分类
安全科学 | 213篇 |
废物处理 | 233篇 |
环保管理 | 1263篇 |
综合类 | 394篇 |
基础理论 | 1074篇 |
环境理论 | 5篇 |
污染及防治 | 1129篇 |
评价与监测 | 331篇 |
社会与环境 | 171篇 |
灾害及防治 | 48篇 |
出版年
2023年 | 22篇 |
2022年 | 20篇 |
2021年 | 47篇 |
2020年 | 30篇 |
2019年 | 59篇 |
2018年 | 69篇 |
2017年 | 88篇 |
2016年 | 109篇 |
2015年 | 109篇 |
2014年 | 105篇 |
2013年 | 538篇 |
2012年 | 174篇 |
2011年 | 247篇 |
2010年 | 189篇 |
2009年 | 187篇 |
2008年 | 254篇 |
2007年 | 255篇 |
2006年 | 232篇 |
2005年 | 161篇 |
2004年 | 181篇 |
2003年 | 187篇 |
2002年 | 166篇 |
2001年 | 79篇 |
2000年 | 105篇 |
1999年 | 96篇 |
1998年 | 73篇 |
1997年 | 64篇 |
1996年 | 72篇 |
1995年 | 71篇 |
1994年 | 61篇 |
1993年 | 65篇 |
1992年 | 72篇 |
1991年 | 43篇 |
1990年 | 52篇 |
1989年 | 43篇 |
1988年 | 32篇 |
1987年 | 38篇 |
1986年 | 44篇 |
1985年 | 40篇 |
1984年 | 44篇 |
1983年 | 50篇 |
1982年 | 38篇 |
1981年 | 54篇 |
1980年 | 45篇 |
1979年 | 22篇 |
1978年 | 24篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1975年 | 14篇 |
1971年 | 13篇 |
排序方式: 共有4861条查询结果,搜索用时 15 毫秒
221.
222.
Standard procedures for evaluating environmental impact involve comparison between before and after conditions or scenarios
or between treatment and control site pairs. In many cases, however, endogenous directional change (natural succession) is
expected to occur at a significant rate over the period of concern, particularly for manmade systems such as impoundments.
Static evaluations do not provide an adequate approach to such problems. A new evaluation frame is proposed. Nominal system
behavior over time is characterized by a stochastic envelope around a nominal trajectory. We show that both the state variance
and the sampling variance can change over time. In this context, environmental regulations can be framed as constraints, targets,
or conformance to ideal trajectories. Statistical tests for determining noncompliance are explored relative to process variance,
sample error, and sample size. Criteria are elucidated for choosing properties to monitor, sample size, and sampling interval. 相似文献
223.
ABSTRACT: Local governments often face environmental problems that cross political boundaries. The onus for solution usually falls on the moat severely affected jurisdiction, others do nothing until impacted. Resolution of these problems requires cooperation across political boundaries which means that local governments must be persuaded first that there is a problem, and second that action is required to solve it. This paper presents a method to supply low cost, credible information that can be used to achieve consensus on problem solution. A case study of a lake water quality management problem is described. Formative evaluation techniques was adapted to provide a minimum of evidence which was then used to persuade less impacted local jurisdictions to cooperate in the problem solution. 相似文献
224.
John B. Whitcomb 《Journal of the American Water Resources Association》1990,26(6):921-926
ABSTRACT: A water use model was developed to estimate water savings from installation of low-flow showerheads and toilet displacement devices in residential housing. The model measures household water use in per capita terms with adjustments for age of occupants, household income, if occupants responsible for direct payment of water bill, and type of water fixtures. Detailed data on 308 single family residences involved with a pilot retrofit program in the Seattle, Washington, area were analyzed. We estimated per capita indoor water use to decline by 6.4 and 2.1 percent from complete installation of low-flow showerheads and toilet displacement devices, respectively. 相似文献
225.
John Veevers 《The Environmentalist》1989,9(2):142-144
News And Comments
Restoring a ravished Island 相似文献226.
Data are presented for a particular population on its perception of English and Welsh local authority areas in terms of desirability for residence. The method employed permits a distinction between positive and negative judgements as well as a measure of the differing degree to which areas figure in the mind at all. It is established that the areas are seen in terms of a sharply differentiated hierarchy of preference and that there is considerable variation in the extent to which areas are “visible”. In aggregate negative judgements predominate and the most frequently expressed attitude is strong dislike. Places in the south‐west are popular as are some places in the north. London Boroughs are unpopular although in varying degrees. The most favoured place is Cornwall and the least favoured is Wolverhampton. It is argued that perceptions studied in the “direct” way used here are important to complement those employing an “oblique” method in which criteria of choice are assumed or established by social survey and then used to create a profile of preference against which places can be measured and ranked. 相似文献
227.
John R. Thene Heinz G. Stefan Ekaterini I. Daniil 《Journal of the American Water Resources Association》1989,25(6):1189-1198
ABSTRACT: A method to evaluate the effect of hydropower development on downstream dissolved oxygen (DO) is presented for a low head dam. Water, previously aerated during release over spillways and under gates, is diverted through the hydropower facility without further aeration. The oxygen transfer that occurs as a result of air entrainment at the various release points of a dam is measured. Oxygen transfer efficiencies are calculated and incorporated into an oxygen transfer model to predict average release DO concentrations. This model is used to systematically determine the effect of hydropower operation on downstream DO. Operational alternatives are investigated and a simple operational guide is developed to mitigate the effects of hydropower operation. Combinations of reduced generation and optimal releases from the dam allow the hydropower facility to operate within DO standards. 相似文献
228.
229.
230.
John M. Bartholow 《Environmental management》1991,15(6):833-845
Water temperature is almost certainly a limiting factor in the maintenance of a self-sustaining rainbow trout (Oncorhynchus mykiss, formerlySalmo gairdneri) and brown trout (Salmo trutta) fishery in the lower reaches of the Cache la Poudre River near Fort Collins, Colorado, USA. Irrigation diversions dewater
portions of the river, but cold reservoir releases moderate water temperatures during some periods. The US Fish and Wildlife
Service’s Stream Network Temperature Model (SNTEMP) was applied to a 31-km segment of the river using readily available stream
geometry and hydrological and meteorological data. The calibrated model produced satisfactory water temperature predictions
(R
2=0.88,P<0.001, N=49) for a 62-day summer period. It was used to evaluate a variety of flow and nonflow alternatives to keep water
temperatures below 23.3°C for the trout. Supplemental flows or reduced diversions of 3 m3/sec would be needed to maintain suitable summer temperatures throughout most of the study area. Such flows would be especially
beneficial during weekends when current irrigation patterns reduce flows. The model indicated that increasing the riparian
shade would result in little improvement in water temperatures but that decreasing the stream width would result in significant
temperature reductions. Introduction of a more thermally tolerant redband trout (Oncorhynchus sp.), or smallmouth bass (Micropterus dolomieui) might prove beneficial to the fishery. Construction of deep pools for thermal refugia might also be helpful. 相似文献