全文获取类型
收费全文 | 16037篇 |
免费 | 1027篇 |
国内免费 | 3658篇 |
专业分类
安全科学 | 942篇 |
废物处理 | 259篇 |
环保管理 | 4505篇 |
综合类 | 9080篇 |
基础理论 | 1773篇 |
环境理论 | 1篇 |
污染及防治 | 1507篇 |
评价与监测 | 1293篇 |
社会与环境 | 1135篇 |
灾害及防治 | 227篇 |
出版年
2024年 | 78篇 |
2023年 | 284篇 |
2022年 | 441篇 |
2021年 | 428篇 |
2020年 | 512篇 |
2019年 | 433篇 |
2018年 | 399篇 |
2017年 | 610篇 |
2016年 | 736篇 |
2015年 | 794篇 |
2014年 | 765篇 |
2013年 | 1073篇 |
2012年 | 1094篇 |
2011年 | 1238篇 |
2010年 | 896篇 |
2009年 | 905篇 |
2008年 | 708篇 |
2007年 | 1141篇 |
2006年 | 1059篇 |
2005年 | 836篇 |
2004年 | 727篇 |
2003年 | 751篇 |
2002年 | 628篇 |
2001年 | 503篇 |
2000年 | 481篇 |
1999年 | 414篇 |
1998年 | 280篇 |
1997年 | 271篇 |
1996年 | 254篇 |
1995年 | 211篇 |
1994年 | 191篇 |
1993年 | 173篇 |
1992年 | 131篇 |
1991年 | 103篇 |
1990年 | 85篇 |
1989年 | 89篇 |
1988年 | 77篇 |
1987年 | 74篇 |
1986年 | 46篇 |
1984年 | 49篇 |
1983年 | 59篇 |
1982年 | 59篇 |
1981年 | 78篇 |
1980年 | 87篇 |
1979年 | 78篇 |
1978年 | 53篇 |
1977年 | 49篇 |
1973年 | 44篇 |
1972年 | 39篇 |
1971年 | 60篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
John H. Martin 《Journal of the American Water Resources Association》1997,33(4):741-753
ABSTRACT: On May 19, 1993, a jury in the U.S. District Court for the Western District of New York found Southview Farm and Richard H. Popp guilty of violating the Clean Water Act on five occasions. The violations were the result of storm water runoff from a site used for disposal of dairy cattle manure from an unpermitted concentrated animal feeding operation. The presiding District Court judge later dismissed the jury verdict, and subsequently a U.S. Court of Appeals for the Second Circuit reversed the dismissal. The Court of Appeals concluded that the discharges were not exempt as agricultural storm water discharges, and that the manure spreaders involved were point sources. Because the use of animal manures in crop production activities will result, unavoidably, in the discharge of some pollutants to adjacent surface waters, a rational and universally applicable basis is needed to determine when such discharges are point versus nonpoint source. Current statutes and regulations do not delineate clearly such a boundary. To address this lack of specificity, I propose that application rates be based on recommended crop nutrient needs. 相似文献
952.
Martin H. David Erhard F. Joeres Eric D. Loucks Kenneth W. Potter Stuart S. Rosenthal 《Journal of the American Water Resources Association》1988,24(1):141-148
ABSTRACT: Water level fluctuations of the Great Lakes often have created regional controversies among the states and Canadian provinces that share this vast resource. Even though the 100-year range of their water levels is only four to five feet, episodes of high and low Great Lakes water levels have been a recurring problem throughout the twentieth century. The possibility of increased diversion and consumptive use has exacerbated the existing conflicts over how to manage this water resource. A research project evaluated the effects of interbasin diversion on the Great Lakes system and on the industries that depend on the maintenance of historical water levels, namely hydropower and commercial navigation. The simulation approach employed in this research and some of the important findings are presented. The approach is similar to that used in recent government studies of Great Lakes water level regulation. Several significant modifications were made specifically addressing the diversion issue. Aggregate annual impacts to hydropower and shipping resulting from a diversion of 10,000 cubic feet per second were found to vary from 60 to 100 million dollars. Increases in impacts as a function of diversion rate are nonlinear for the navigation industry. 相似文献
953.
James P. Hughes Steven P. Millard 《Journal of the American Water Resources Association》1988,24(3):521-531
ABSTRACT: A common problem arises in testing for trends in water quality when observations are reported as “less than detection limit.” If a single detection limit is used for the entire study, existing non-parametric statistical methods, modified for ties, are applicable. If, however, the detection limit varies during the course of the study, resulting in multiple detection limits, then the commonly used trend detection methods are not appropriate. A statistic similar to Kendall's tau, but based on expected ranks, is proposed. Monte Carlo simulations show that the normal approximation to the distribution of this statistic is quite good, even for small samples and a large proportion of censored observations. The statistic is also shown to have greater power than the ad-hoc method of treating all observations less than the target censored observation as tied. 相似文献
954.
David Berryman Bernard Bobe Daniel Cluis John Haemmerli 《Journal of the American Water Resources Association》1988,24(3):545-556
ABSTRACT: A review of nonparametric tests for trend leads to the conclusion that Mann-Whitney, Spearman, and Kendall tests are the best choice for trend detection in water quality time series. Recently these tests have been adapted to account for dependence and seasonality in such series (Lettenmaier, 1976; Hirsch, et al., 1972; Hirsch and Slack, 1984). For monotonic trends, a procedure allowing to select the pertinent tests considering the characteristics of time series is proposed and the practical limitations of the tests are also brought out. This procedure has been applied to identify the appropriate trend detection test for the time series of nine water quality parameters at Lake Laflamme (Québec). When a time series can be tested with the Mann-Whitney, Kendall, Spearman, or Lettenmaier (1976) test, the number of observations required to detect trends of a given magnitude, for selected significance and power levels can be calculated with the power function of the t test. When the test proposed by Hirsch, et al. (1984), Hirsch and Slack (1984), or Farrell (1980) need to be used, the number of observations can only be estimated approximately from the results of empirical power studies. 相似文献
955.
J. V. Brahana E. F. Hollyday 《Journal of the American Water Resources Association》1988,24(3):577-580
ABSTRACT: The method of identifying dry stream reaches in carbonate terrane as surface indicators of potential ground-water reservoirs offers a valuable exploration technique that is more rapid and less expensive than traditional exploration methods involving random test drilling. In areas where dry stream reaches occur, subsurface drainage successfully competes with surface drainage, and sheet-like dissolution openings have developed parallel to bedding creating the ground-water reservoir. The occurrence and hydraulic characteristics of such reservoirs are highly variable, as attested to by the wide range of well yields. Union Hollow in south-central Tennessee is the setting for a case study that illustrates the application of the dry stream reach technique. In this technique, dry stream reach identification is based on two types of readily acquired information: (1) remotely sensed black and white infrared aerial photography; and (2) surface reconnaissance of stream channel characteristics. Test drilling in Union Hollow subsequent to identification of the dry reach proved that a localized ground-water reservoir was present. 相似文献
956.
Warren Viessman 《Journal of the American Water Resources Association》1988,24(3):581-584
ABSTRACT: The cries of pending water crises are usually cast in terms of water availability and/or water quality. Unfortunately, the real factors underlying a perceived crisis are often overlooked and the solutions prescribed are fax from optimal when measured in either economic or social terms. Today's technology outstrips its implementation, yesterday's solutions are imposed on a new breed of problems, and a static game is being played in a dynamic world. There is a need for the application of innovative and revolutionary tactics, for modernizing institutions, and for educating technologists and decision makers alike in the art of communicating their views and skills. This is the challenge. If it is met, some predicted crises will not materialize, and many others will be diminished in scale. An exciting opportunity exists to extend the boundaries of a new era in water management. 相似文献
957.
Donald E. Agthe R. Bruce Billings Judith M. Dworkin 《Journal of the American Water Resources Association》1988,24(3):627-630
ABSTRACT: Socioeconomic determinants of individual household water use were estimated using regressions of these characteristics with actual household water use for winter and summer. Results were disaggregated between those consumers who were aware of an increasing block rate price structure and those who were not. Most of the informed group members believed that this price structure did result in significant reductions in water use. Nevertheless, overall water use was greater for the informed group. The determinants of water use were found to differ between informed and uninformed users as well as between winter and summer. The uninformed users were influenced by a larger set of variables in each season than the informed group. In winter, the informed group members with swimming pools and/or arid landscaping used less water than their uninformed counterparts. Summer water use increased with length of tenancy in home for the uninformed group but not for informed, while increasing with ownership for informed consumers. 相似文献
958.
John E. Keith Rangesan Narayanan 《Journal of the American Water Resources Association》1988,24(6):1247-1256
ABSTRACF: Examination of a series of studies of the economically efficient water allocations in the Upper Colorado River, Yellowstone River, and Great Basins indicate that water is not a serious general physical constraint on the development of energy resources, so long as public institutions do not hinder the exchange of water rights in markets. Energy development will cause limited impacts on other water-using sectors, principally agriculture. There appears to be little reason to develop large-scale water storage facilities, even during periods of reduced water production. Water storage developments appear to be necessary only when institutional constraints severely restrict water rights markets and transfers. 相似文献
959.
K. James. DeCook Kennith E. Foster Martin M. Karpiscak 《Journal of the American Water Resources Association》1988,24(6):1295-1301
ABSTRACT: An index of residential water efficiency - a “W-Index” - can serve as a measure of effectiveness of water conservation features in the home. The index provides a calculated numerical value for each dwelling unit, derived from the number and kind of water-saving features present, including indoor and outdoor water savers and water harvesting or recycling systems. A W-Index worksheet, devised for on-site evaluation of single-family residences in the Tucson, Arizona, region shows that a nonconserving residence with all the water-using features would use 151,000 gallons per year or 148 gallons per capita per day (gpcpd), while the fully conserving model would use 35,300 gallons per year or 35 gpcpd and with water harvesting and graywater recycling systems would have a maximum W-Index of W-160. A Tucson water conservation demonstration home, Casa del Agua, received a rating of W-139, and field tests of about 30 homes in new Tucson subdivisions show values ranging from W-75 to W-100, indicating the incorporation of some water conservation in current new models. By adjustment of some climatic or water-use parameters, the W-Index format can be applied to various types of dwelling units or to other urban areas. The W-Index can be used by individual homeowners or builders to evaluate water efficiency of residential units, or by water providers or water management agencies as a device for promoting and achieving water conservation goals. 相似文献
960.
R. C. Kattelmann N. H. Berg M. K. Pack 《Journal of the American Water Resources Association》1985,21(2):273-280
A simple simulation model designed to monitor snow-packs of the central Sierra Nevada is described. The model estimates average snow water equivalent for rectangular subregions in the area. Static subregion characteristics, daily precipitation and mean and minimum air temperatures measured at three index stations are the only needed input values. A water balance technique simulates daily snowpack changes in each subregion. Reasonable basinwide water equivalent values are produced. The procedure should be useful for estimating snow water distribution in large mountainous watersheds. 相似文献