全文获取类型
收费全文 | 17581篇 |
免费 | 145篇 |
国内免费 | 116篇 |
专业分类
安全科学 | 410篇 |
废物处理 | 668篇 |
环保管理 | 1936篇 |
综合类 | 5376篇 |
基础理论 | 3643篇 |
环境理论 | 2篇 |
污染及防治 | 4218篇 |
评价与监测 | 902篇 |
社会与环境 | 625篇 |
灾害及防治 | 62篇 |
出版年
2018年 | 218篇 |
2017年 | 199篇 |
2016年 | 295篇 |
2015年 | 219篇 |
2014年 | 324篇 |
2013年 | 1176篇 |
2012年 | 383篇 |
2011年 | 540篇 |
2010年 | 500篇 |
2009年 | 561篇 |
2008年 | 596篇 |
2007年 | 617篇 |
2006年 | 541篇 |
2005年 | 484篇 |
2004年 | 511篇 |
2003年 | 469篇 |
2002年 | 450篇 |
2001年 | 623篇 |
2000年 | 419篇 |
1999年 | 285篇 |
1998年 | 205篇 |
1997年 | 203篇 |
1996年 | 205篇 |
1995年 | 237篇 |
1994年 | 247篇 |
1993年 | 206篇 |
1992年 | 223篇 |
1991年 | 232篇 |
1990年 | 255篇 |
1989年 | 230篇 |
1988年 | 183篇 |
1987年 | 182篇 |
1986年 | 181篇 |
1985年 | 180篇 |
1984年 | 199篇 |
1983年 | 188篇 |
1982年 | 199篇 |
1981年 | 209篇 |
1980年 | 169篇 |
1979年 | 180篇 |
1978年 | 149篇 |
1977年 | 139篇 |
1974年 | 147篇 |
1973年 | 147篇 |
1968年 | 156篇 |
1967年 | 184篇 |
1966年 | 154篇 |
1965年 | 149篇 |
1964年 | 151篇 |
1963年 | 139篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
901.
Hillary H. Jeffcoat Marshall E. Jennings 《Journal of the American Water Resources Association》1987,23(2):313-316
ABSTRACT: An application is described of the branch-network flow model, BRANCH, to the upper Alabama River system in central Alabama. The model is used to simulate one-dimensional unsteady flows and water surface elevations in approximately 60 river miles of the Alabama River system. Preliminary calibration was made using 72 hours of observed data. Simulated discharges are about 10 percent lower than observed discharges at higher discharge rates and computed flows lag observed flows by about 30 minutes. 相似文献
902.
Kenneth G. Maxey Norman H. Starler 《Journal of the American Water Resources Association》1987,23(5):749-759
ABSTRACT: In the past, development of Federal water resource projects depended heavily or exclusively on Federal financing of construction costs. However, pressures on the Federal budget, environmental issues, and the notion that there are economic efficiency gains when beneficiaries of Federal water resource projects increase their cost share are causing changes. The case of the Central Arizona Project Plan 6 is a noteworthy example of the transition to more non-Federal participation in water resource development. This is because the non-Federal financing is to be provided for a project already under construction. The negotiation and terms of the Plan 6 financing agreement between the Department of the Interior and multiple interests in Arizona are used as an example of how Federal water project cost sharing is in a state of transition. The negotiation process is described, a financial analysis is provided, and the terms of the agreement and policy issues that were deliberated in the Executive Branch of the Federal Government are discussed. 相似文献
903.
William H. Babcock 《Journal of the American Water Resources Association》1986,22(3):405-415
ABSTRACT: After input from various interested agencies, three miles of creek were relocated to facilitate the construction of Interstate 70 through Tenmile Canyon west of Denver. The 0.5.million dollar project was designed to provide fish habitat of equal value to that present before construction or, if possible, to improve this habitat. Construction techniques were designed to minimize damage to flora and fauna. After the channels were excavated, rock and log fish habitat structures were constructed. Two years after construction, a 4 percent chance flood occurred at the project area which made almost 75 percent of the habitat structures ineffective. Pool-riffle ratios and quantity and quality of spawning areas remained essentially unchanged throughout the period. Population estimates indicated an increase in the number of fish in the postconstruction period compared to preconstruction numbers. Fish biomass estimates for the project area were comparable for the two periods. Aquatic invertebrate populations were unchanged as indicated by comparison of three pre- and postconstruction indices. 相似文献
904.
905.
This study documents the effects of power utility right-of-way construction and maintenance on the vegetation of a wooded wetland in North Reading, Massachusetts, USA. Neither activity had a substantial, long-term negative impact. Except for differences in size and maturity, the vegetation recovered in two years from nearly total destruction caused by construction. Maintenance that included the periodic removal of high-growing species led to the formation of a plant association different from the one occurring naturally, but as diverse and species rich. 相似文献
906.
Reclamation of wastes contaminated by copper,lead, and zinc 总被引:18,自引:0,他引:18
M. H. Wong 《Environmental management》1986,10(6):707-713
Waste materials containing toxic levels of copper, lead, and zinc, such as mine and smelter wastes, present difficult conditions for the establishment of vegetation. This article reviews the many attempts which have been made to reclaim these wastes. Inert wastes from mining and quarrying operations, such as slate quarry waste and certain colliery shales, seem to be good materials for reclaiming wastes contaminated by copper, lead, and zinc. Organic wastes, such as sewage sludge and domestic refuse, may provide only a temporary visual improvement and stabilization of the toxic materials.Nontolerant plant materials may often be planted directly on modern waste materials, which are less toxic than they were in the past. However, tolerant plant materials are needed for revegetating waste materials produced by early and more primitive extraction methods. 相似文献
907.
Summary In the present paper efforts have been made to identify an environmentally sustainable and economically gainful strategy for agricultural development in the Himalayan region in Uttar Pradesh State, India. In the underdeveloped rural habitat that exists, a strategy, where the economics of environmentally sustainable development can be studied, is urgently required. The findings have been based on an empirical investigation of 150 sampled households spread over fifteen villages. It was found that the state of Himalayan agriculture and allied activities was in a critical condition, requiring urgent attention in order to improve the human environment. Suggested viable improvements in Himalayan agricultural development may be grouped into four categories, viz., an expansion of the cultivated area, where the land use pattern and other factors are discussed; full utilisation of irrigation potentialities, in which water management is discussed; improvement in the cropping pattern, where the whole system of cropping is analysed; and modifications in the use of agricultural appliances, specially in hoeing, ploughing and inter-culturing implements. Based on a critical analysis of these four identified aspects, economically viable, ecologically sound and socially justified environmental planning may be effectively framed.Dr H.C. Pokhriyal is Head of the Department of Economics at Garhwal University Campus, Tehri, and Dr N.S. Bist is Professor and Head of the Department of Economics at Garhwal University, Srinagar Garhwal, Himalaya, U.P., India. 相似文献
908.
Food habits of white-tailed deer (Odocoileus virginianus) were examined from January to November 1984 via fecal-pellet analysis at Valley Forge National Historical Park (VFNHP), which represents an island habitat for deer surrounded by extensive urbanization, in southeastern Pennsylvania. In addition, use of fields by deer was compared to food habits. Herbaceous vegetation (forbs, leaves of woody plants, and conifer needles) was the predominant food type in all seasons except fall. Acorns and graminoids (grasses and sedges) were important food resources in fall and spring, respectively. Use of woody browse (twigs) was similar among seasons. Field use was relatively high during fall, winter without snow cover (<20 cm), and spring when food resources in fields were readily available. In contrast, use of fields was lowest in summer when preferred woodland foods were available and in winter with snow cover when food in fields was not readily accessible. Patterns of food-type use by deer at VFNHP indicate the year-round importance of nonwoody foods and field habitats to deer populations on public lands such as national parks in the northeastern United States. 相似文献
909.
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
910.
Kenneth H. Reckhow 《Journal of the American Water Resources Association》1988,24(4):723-734
ABSTRACT: A cross-sectional data set of 80 lakes and reservoirs in nine southeastern states was examined to specify and parameterize trophic state relationships. The relationships fitted are based on measurements of several limnological variables taken over the course of a growing season or year in each of the lakes. The trophic state models relate phosphorus and nitrogen loading to inlake phosphorus and nitrogen concentrations, which in turn are related to maximum chlorophyll level, Secchi disk depth, dominant algal species, and hypolimnetic dissolved oxygen status. Due to the empirical nature of the study, causal conclusions are limited; rather, the models are most useful for prediction of average growing season conditions related to trophic state. 相似文献