全文获取类型
收费全文 | 3867篇 |
免费 | 741篇 |
国内免费 | 756篇 |
专业分类
安全科学 | 1552篇 |
废物处理 | 79篇 |
环保管理 | 690篇 |
综合类 | 1863篇 |
基础理论 | 311篇 |
污染及防治 | 315篇 |
评价与监测 | 137篇 |
社会与环境 | 150篇 |
灾害及防治 | 267篇 |
出版年
2024年 | 17篇 |
2023年 | 88篇 |
2022年 | 177篇 |
2021年 | 221篇 |
2020年 | 205篇 |
2019年 | 224篇 |
2018年 | 153篇 |
2017年 | 201篇 |
2016年 | 265篇 |
2015年 | 259篇 |
2014年 | 231篇 |
2013年 | 261篇 |
2012年 | 367篇 |
2011年 | 322篇 |
2010年 | 242篇 |
2009年 | 229篇 |
2008年 | 181篇 |
2007年 | 303篇 |
2006年 | 247篇 |
2005年 | 157篇 |
2004年 | 128篇 |
2003年 | 113篇 |
2002年 | 98篇 |
2001年 | 88篇 |
2000年 | 85篇 |
1999年 | 53篇 |
1998年 | 54篇 |
1997年 | 49篇 |
1996年 | 41篇 |
1995年 | 35篇 |
1994年 | 44篇 |
1993年 | 30篇 |
1992年 | 17篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 18篇 |
1984年 | 6篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 7篇 |
1973年 | 5篇 |
1972年 | 12篇 |
1971年 | 10篇 |
1970年 | 6篇 |
排序方式: 共有5364条查询结果,搜索用时 15 毫秒
101.
Chansheng He 《Journal of the American Water Resources Association》1997,33(5):1055-1068
ABSTRACT: Growing interest in agricultural irrigation in the Great Lakes basin presents an increasing competition to other uses of Great Lakes water. This paper, through a case study of the Mud Creek Irrigation District in the Saginaw Bay basin, Michigan, evaluates the potential hydrologic effects of withdrawing water for agricultural irrigation to the Great Lakes. Crop growth simulation models for corn, soybeans, dry beans, and the FAO Penman method were used to estimate the difference in evapotranspiration rates between irrigated and nonirrigated identical crops, based on climate, soil, and management data. The simulated results indicate that an additional 70–120 mm of water would be evapotranspirated during the growing season from irrigated crop fields as compared to nonirrigated identical plantings. Dependent upon the magnitude of irrigation expansion, an equivalent of about 1 to 5 mm of water from Lakes Huron-Michigan could be lost to the atmosphere. If agricultural irrigation further expands in the entire Great Lakes basin, the aggregated potential of water loss to the atmosphere through ET from all five Great Lakes would be even greater. 相似文献
102.
在工程建设中,工地及邻近地区的断层活动性是工程设计的一项重要依据。在总结以往研究的基础上,介绍了显微构造分析法和包裹体方法在断层活动性评价中的国内外最新研究成果。事实表明,这两种方法在工程地质领域具有良好的应用前景。 相似文献
103.
孟连,丽江地震前云南天文台时纬残差异常 总被引:3,自引:0,他引:3
本文分析了云南天文台光电等高仪自有观测以来的时纬残差异常与云南及其周邻地区大地震的对应关系;并报导了孟连、丽江地震前云南天文台的时纬残差均有明显异常。这再次证明时纬残差的明显异常可为台站周围的强震预测提供可靠信息 相似文献
104.
Christopher I. Thornton Steven R. Abt Warren P. Clary 《Journal of the American Water Resources Association》1997,33(6):1279-1288
ABSTRACT: A meandering stream channel was simulated in the Hydraulics Laboratory at Colorado State University and a series of tests was conducted using four types of vegetation to evaluate the potential effects of vegetation on sediment deposition and retention in a stream channel. The data collected included average flow velocity, flow depth, length of vegetation, density of vegetation, cross-sectional area of the vegetative stem, wetted perimeter of the vegetative stem, and injection and flushing time. The findings indicated that the vegetation could retain from 30 to 70 percent of the deposited sediments. The ability of vegetation to entrap and retain sediment is related to the length and cross-sectional area of the vegetation. The variables describing the flow and the vegetative properties were combined to form a predictive parameter, the sedimentation factor (Sd) that can be compared with the amount of sediment entrapped by vegetation in a stream system. A relation was developed correlating vegetation length to sediment retention after flushing for flexibility and rigid vegetation. 相似文献
105.
热辐射的破坏准则和池火灾的破坏半径 总被引:10,自引:4,他引:10
热辐射破坏是发生在开放气环境中的池火灾的主要破坏机理。本文讨论了热辐射的破坏准则,提出预测池火灾破坏半径的方法,进行了数值模拟计算,分而和时纳了池火灾的基本规律 相似文献
106.
107.
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
108.
Alberto Padilla Antonio Pulido-Bosch Maria L. Calvache Angela Vallejos 《Journal of the American Water Resources Association》1996,32(5):917-928
ABSTRACT: Autoregressive moving average (ABMA) models have been applied to study the flow series of the karstic springs of La Villa, Fuente Mayor (Spain), and Aliou (France). The theoretical meaning of the parameters involved in the model upon applying it to a simplified scheme of the emptying of a karstic aquifer is first analyzed. The types of transformations necessary to apply these models to the flow series that lack normality and have strong periodic components are also indicated, as are the advantages of this type of model and the physical significance of the parameters obtained, with respect to the standpoint of hydraulics, ranging from rather homogeneous aquifers (La Villa) to extremely karstic (Aliou), including aquifers with intermediate characteristics (Fuente Mayor). 相似文献
109.
SCR反应塔入口段烟气速度场的数值模拟 总被引:2,自引:1,他引:2
使用商业计算软件CFX5.7.1,采用标准k-ε湍流模型,模拟了SCR脱硝反应塔入口段烟气速度场,并分析比较了导流板对烟气速度场的影响及均匀SCR反应塔进口处烟气速度场的作用。 相似文献
110.
可视化灾害数字仿真重构理论及实证研究(Ⅱ)--理论框架与概念化范式 总被引:2,自引:1,他引:2
可视化灾害数字仿真重构理论研究,不仅可以实现对灾害空间数据进行有效的集成管理和时空分析,而且为灾害的防治、应急管理和工程论证等提供可靠的依据,是解决灾害实验的危险性和不可重复性的最佳途径.本文提出可视化灾害数字仿真重构理论的概念、研究对象和方法,综述该理论所需要涉及多种跨学科的技术支持,提出灾害数字仿真重构理论的实施流程,按照致灾因子孕育、发生以及作用于承灾体形成灾害的过程为线索,建立灾害数字仿真模型的概念化范式.上述工作共同构成灾害数字仿真重构的完整理论体系. 相似文献