全文获取类型
收费全文 | 29220篇 |
免费 | 1951篇 |
国内免费 | 4872篇 |
专业分类
安全科学 | 3137篇 |
废物处理 | 471篇 |
环保管理 | 6400篇 |
综合类 | 15596篇 |
基础理论 | 3138篇 |
环境理论 | 13篇 |
污染及防治 | 1914篇 |
评价与监测 | 1913篇 |
社会与环境 | 2279篇 |
灾害及防治 | 1182篇 |
出版年
2024年 | 80篇 |
2023年 | 330篇 |
2022年 | 604篇 |
2021年 | 736篇 |
2020年 | 785篇 |
2019年 | 684篇 |
2018年 | 622篇 |
2017年 | 902篇 |
2016年 | 1098篇 |
2015年 | 1214篇 |
2014年 | 1258篇 |
2013年 | 1751篇 |
2012年 | 2016篇 |
2011年 | 2206篇 |
2010年 | 1607篇 |
2009年 | 1622篇 |
2008年 | 1278篇 |
2007年 | 2040篇 |
2006年 | 1964篇 |
2005年 | 1587篇 |
2004年 | 1367篇 |
2003年 | 1467篇 |
2002年 | 1196篇 |
2001年 | 990篇 |
2000年 | 949篇 |
1999年 | 884篇 |
1998年 | 647篇 |
1997年 | 560篇 |
1996年 | 488篇 |
1995年 | 438篇 |
1994年 | 417篇 |
1993年 | 371篇 |
1992年 | 266篇 |
1991年 | 214篇 |
1990年 | 157篇 |
1989年 | 125篇 |
1988年 | 110篇 |
1987年 | 83篇 |
1986年 | 59篇 |
1985年 | 59篇 |
1984年 | 63篇 |
1983年 | 70篇 |
1982年 | 67篇 |
1981年 | 79篇 |
1980年 | 88篇 |
1979年 | 79篇 |
1978年 | 53篇 |
1977年 | 52篇 |
1973年 | 47篇 |
1971年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
931.
Most writers on resource management presume that local populations, if they act in their self-interest, seldom conserve or protect natural resources without external intervention or privatization. Using the example of forest management by villagers in the Indian Himalayas, this paper argues that rural populations can often use resources sustainably and successfully, even under assumptions of self-interested rationality. Under a set of specified social and environmental conditions, conditions that prevail in large areas of the Himalayas and may also exist in other mountain regions, community institutions are more efficient in managing resources than either private individuals or the central government. In advancing this argument, the paper undermines the often dogmatic belief in the universal superiority of private forms of ownership and management. 相似文献
932.
Adaptive management: Promises and pitfalls 总被引:3,自引:1,他引:3
Proponents of the scientific adaptive management approach argue that it increases knowledge acquisition rates, enhances information flow among policy actors, and provides opportunities for creating shared understandings. However, evidence from efforts to implement the approach in New Brunswick, British Columbia, Canada, and the Columbia River Basin indicates that these promises have not been met. The data show that scientific adaptive management relies excessively on the use of linear systems models, discounts nonscientific forms of knowledge, and pays inadequate attention to policy processes that promote the development of shared understandings among diverse stakeholders. To be effective, new adaptive management efforts will need to incorporate knowledge from multiple sources, make use of multiple systems models, and support new forms of cooperation among stakeholders. 相似文献
933.
皖南山区中华猕猴桃的气候适宜性区划 总被引:1,自引:1,他引:1
本文在简要分析皖南山区气候特征的基础上,根据中华猕猴桃的生长习性,提出了发展只结猕猴桃的适宜栽培高度区划,为合理利用山区气候资源发展猕猴桃生产提供科学依据。 相似文献
934.
ClO2处理含铁,锰及细菌饮用水的应用研究 总被引:1,自引:0,他引:1
为了除去水中高含量的铁,锰及细菌,采用ClO2氧化Fe^2+,Mn^2+和灭菌的方法。研究结果表明,处理后水平铁,锰都末检出,细菌指标符合国家饮用水标准。此法具有工艺简单,操作方便,反应速度快,去除率极高,不产生致癌物质THM、且能很好地除水中的异味及色度等优点。此法适用于各种生活给水系统。 相似文献
935.
936.
Allan K Fitzsimmons 《Journal of the American Water Resources Association》1996,32(2):217-227
ABSTRACT: Protection of ecosystems as entities on the landscape has attracted a wide range of support. Ecosystem-based public policies are claimed to be more effective, efficient, and scientifically sound than other approaches to environmental and natural resource policy. The ecosystem concept was never intended to serve as a public policy guide or to determine landscape units for land management purposes. This paper critically examines the use of the ecosystem concept in public policy and land use management and analyzes the proposed rule to manage the National Forest System according to ecosystem management principles. The concept is found to be unsuitable as a basis for guiding environmental and natural resource public policies in general while the proposed rule to manage the national forests according to ecosystem management principles is shown to be incoherent. 相似文献
937.
938.
Shiping Liu Steven T Yen Dana W. Kolpin 《Journal of the American Water Resources Association》1996,32(4):845-853
ABSTRACT: Atrazine and atrazine-residue (atrazine + two metabolites - deethylatrazine and deisopropylatrazine) concentrations were examined to determine if consideration of these atrazine metabolites substantially adds to our understanding of the distribution of this pesticide in groundwater of the midcontinental United States. The mean of atrazine.residue concentrations was 53 percent greater than that of atrazine alone for those observations above the detection limit (> 0.05 μg/l). Furthermore, a censored regression analysis using atrazine-residue concentrations revealed significant factors not identified when only atrazine concentrations were used. Thus, knowledge of concentrations of these atrazine metabolites is required to obtain a true estimation of risk of using these aquifers as sources for drinking water, and such knowledge also provides information that ultimately may be important for future management policies designed to reduce atrazine concentrations in ground water. 相似文献
939.
Frank A. Ward Thomas P Lynch 《Journal of the American Water Resources Association》1996,32(6):1127-1138
ABSTRACT: This paper presents an integrated optimal control model that optimizes economic performance of reservoir management in watersheds in which there are significant economic and hydrologic interdependencies. The model is solved using the General Algebraic Modeling System (GAMS). Results show that application of this model to New Mexico's Rio Chama basin can increase total system benefits over historical benefits by exploiting complementarities between hydroelectricity production, instream recreation, and downstream lake recreation. 相似文献
940.
L. Jeffrey Lefkoff Donald R. Kendall 《Journal of the American Water Resources Association》1996,32(3):451-463
ABSTRACT: A non-linear optimization model is applied to the California State Water Project (SWP) and portions of the Central Valley Project (CVP). The model accounts for the major hydrologic, regulatory, and operational features of both projects. The model maximizes long-term SWP yields over a 70-year period, using a quarterly time step. The potential for increased yield associated with a proposed facility improvement is evaluated with the model. The proposed facility is an extension of the Folsom-South Canal, which would allow water to be conveyed from the American River below Folsom Reservoir into New Melones Reservoir on the Stanislaus River or into the California Aqueduct. Model results indicate that extension of the Folsom-South Canal has the potential to increase SWP yields by 13 percent. 相似文献