全文获取类型
收费全文 | 25405篇 |
免费 | 1926篇 |
国内免费 | 4087篇 |
专业分类
安全科学 | 4359篇 |
废物处理 | 387篇 |
环保管理 | 3977篇 |
综合类 | 12956篇 |
基础理论 | 2858篇 |
环境理论 | 26篇 |
污染及防治 | 1835篇 |
评价与监测 | 1524篇 |
社会与环境 | 2007篇 |
灾害及防治 | 1489篇 |
出版年
2024年 | 111篇 |
2023年 | 480篇 |
2022年 | 775篇 |
2021年 | 900篇 |
2020年 | 850篇 |
2019年 | 798篇 |
2018年 | 694篇 |
2017年 | 921篇 |
2016年 | 1101篇 |
2015年 | 1111篇 |
2014年 | 1173篇 |
2013年 | 1494篇 |
2012年 | 1806篇 |
2011年 | 2015篇 |
2010年 | 1386篇 |
2009年 | 1429篇 |
2008年 | 1183篇 |
2007年 | 1661篇 |
2006年 | 1622篇 |
2005年 | 1312篇 |
2004年 | 1063篇 |
2003年 | 1158篇 |
2002年 | 940篇 |
2001年 | 784篇 |
2000年 | 690篇 |
1999年 | 682篇 |
1998年 | 503篇 |
1997年 | 431篇 |
1996年 | 368篇 |
1995年 | 317篇 |
1994年 | 321篇 |
1993年 | 265篇 |
1992年 | 210篇 |
1991年 | 162篇 |
1990年 | 114篇 |
1989年 | 81篇 |
1988年 | 75篇 |
1987年 | 40篇 |
1986年 | 31篇 |
1985年 | 48篇 |
1984年 | 27篇 |
1983年 | 29篇 |
1982年 | 36篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 30篇 |
1978年 | 19篇 |
1977年 | 21篇 |
1972年 | 21篇 |
1971年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
本文主要论述了在实现我国中长期环境与资源保护战略目标过程中,环境形势的长期性、艰巨性和复杂性;指出必须通过发展观念、经济增长方式、经济体制和政策职能的转变,树立和落实全面、协调和可持续的科学发展观,促进经济、政治、文化、生态环境的全面发展。 相似文献
23.
胡杨林的衰退原因与林地恢复策略 总被引:8,自引:0,他引:8
胡杨广布于地中海沿岸并呈带状东延至中国和蒙古人民共和国。目前,胡杨林已普遍呈不同程度退化,以塔里木盆地为例,垦伐等人为因素使林地总面积迅速减少。现场观测发现,一些林区缺乏胸径20cm以下的立木,而该地从1972年以来断绝洪水来源,显示洪水对幼苗补给可能存在相关,该地断绝洪水多年后,2002年重新出现洪泛过程,洪水退后出现大量的幼苗生长,从而证实洪水过程是胡杨幼林发生的必要条件。本文就此现象提出恢复部分林地的对策。 相似文献
24.
Marie-Claire Cordonier Segger 《Natural resources forum》2004,28(1):61-74
This article develops a practical proposal for progress on sustainable development law. It examines the prospects for an international sustainable development law to provide a framework for more effective, coherent governance. Sustainable development law is briefly defined and an analytical framework is provided. Different degrees of integration between economic, social and environmental law are described. Certain principles of international law related to sustainable development are also highlighted. It is argued that these principles may serve to guide law‐makers and jurists where social, economic and environmental law and policy conflict or overlap. Continuing, underlying questions of sustainable development governance are addressed and its global frameworks analysed. The article also focuses on the 2002 World Summit on Sustainable Development, held in Johannesburg in August‐September 2002, and its specific mandate for the United Nations Commission on Sustainable Development (UNCSD) to take related legal developments into account. The article advances a proposal: that governments, economic, social and environmental intergovernmental organizations and other actors establish a ‘network of inquiry’ with members from relevant groups, including legal and academic organizations, and other expert groups, in order to follow, research, analyse and debate legal developments in a balanced way. 相似文献
25.
E. Conrad Lamon Song S. Qian Daniel D. Richter 《Journal of the American Water Resources Association》2004,40(5):1219-1229
ABSTRACT: Dynamic linear models (DLM) and seasonal trend decomposition (STL) using local regression, or LOESS, were used to analyze the 50‐year time series of suspended sediment concentrations for the Yadkin River, measured at the U.S. Geological Survey station at Yadkin College, North Carolina. A DLM with constant trend, seasonality, and a log10 streamflow regressor provided the best model to predict monthly mean log10 suspended sediment concentrations, based on the forecast log likelihood. Using DLM, there was evidence (odds approximately 69:1) that the log10 streamflow versus log10 suspended sediment concentration relationship has changed, with an approximate 20 percent increase in the log10 streamflow coefficient over the period 1981 to 1996. However, sediment concentrations in the Yadkin River have decreased during the decade of the 1990s, which has been accompanied by a concomitant increase in streamflow variability. Although STL has been shown to be a versatile trend analysis technique, DLM is shown to be more suitable for discovery and inference of structural changes (trends) in the model coefficient describing the relationship between flow and sediment concentration. 相似文献
26.
复杂矿井通风系统角联风路自动识别方法的研究 总被引:4,自引:0,他引:4
角联风路的识别与稳定性分析是矿井通风系统稳定性与可靠性分析理论中的核心内容之一。笔者对通风系统角联风路进行了深入的研究;分析了通路法的局限性,简化了角联风路的数学模型,提出了快速、准确、灵活的角联风路自动识别的新方法——节点位置法;编写了角联风路自动识别软件,并应用现场数据进行测试,将其结果与通路法的结果进行了比较分析;证明了节点位置法是切实可行的。 相似文献
27.
介绍了如何在国家级生态示范区的可持续发展评估中运用灰色系统理论构建定量评估系统模型,并给出了关系型指标表、量纲模型、多元灰色预测模型和发展系数模型以及应用实例.根据该评估系统模型所开发的灰色评估系统由数学模型、计算机软件和硬件组成,可自动完成量纲统一、指标预测、相关分析、综合评估和趋势图表的运算和输出. 相似文献
28.
红外和热分析联用在化工产品研究中的应用 总被引:1,自引:0,他引:1
运用实例论述了红外光谱分析与热分析联用在化工产品的产品开发和检测方面的应用。 相似文献
29.
Jugder Dulam 《Water, Air, & Soil Pollution: Focus》2005,5(3-6):37-49
A discriminate analysis method for probability forecast of dust storms in Mongolia has been developed. The prediction method
uses data recorded at 23 meteorological stations in the Gobi and steppe regions of Mongolia, including surface air pressure
and geo-potential height at the 500-hPa level on grid points, and weather maps from 1975 to 1990.
Weather elements such as air temperature, pressure, geo-potential height etc, which influence the formation of dust storms,
are prepared as predictors. To select the most informative/important predictors (variables), we used a mean correlation matrix
of variables together with the Mahalonobis distance, and correlation coefficients between dust storms and predictors with
an orthogonalization for removing correlated predictors. The most informative predictors for dust storm prediction are intensities
of surface cyclones and migratory anticyclones, passage of cold fronts, the horizontal gradients of the surface air pressure
in the cold frontal zone, cyclonic circulations from the ground surface up to the 500-hPa level, the geo-potential height
at 500-hPa level and its temporal changes.
Selected predictors are used in discriminate analysis for formulating dust storm prediction equations. Sandstorm data have
been classified into three classes, viz., strong, moderate and weak dust storms, depending on their intensities, durations
and areas covered. Predictions of the probabilities of dust storm occurrence use the prediction equations for each class.
The prediction is made from 12 hours to 36 hours.
Verification of the probability forecasts of dust storms is also shown. The accuracy of forecasts is 72.2–79.9% with the data
used for developing equations (dependent variables), in contrast to 67.1–72.0% with unrelated data for deriving equations
(independent variables). 相似文献
30.
大气环境影响评价工作分级要求要点 总被引:1,自引:0,他引:1
根据大气环境影响评价工作的分级要求,提出了针对性的工作要点,以满足大气环境评价工作的需要. 相似文献