全文获取类型
收费全文 | 895篇 |
免费 | 69篇 |
国内免费 | 88篇 |
专业分类
安全科学 | 187篇 |
废物处理 | 19篇 |
环保管理 | 192篇 |
综合类 | 358篇 |
基础理论 | 110篇 |
污染及防治 | 20篇 |
评价与监测 | 51篇 |
社会与环境 | 52篇 |
灾害及防治 | 63篇 |
出版年
2024年 | 4篇 |
2023年 | 16篇 |
2022年 | 34篇 |
2021年 | 41篇 |
2020年 | 32篇 |
2019年 | 27篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 30篇 |
2015年 | 36篇 |
2014年 | 34篇 |
2013年 | 44篇 |
2012年 | 49篇 |
2011年 | 69篇 |
2010年 | 45篇 |
2009年 | 46篇 |
2008年 | 58篇 |
2007年 | 47篇 |
2006年 | 51篇 |
2005年 | 46篇 |
2004年 | 38篇 |
2003年 | 33篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 21篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有1052条查询结果,搜索用时 31 毫秒
131.
Robert M. Hughes 《Environmental management》1985,9(3):253-262
Impacts of sediments and heavy metals on the biota of streams in the copper-mining district of southwestern Montana were examined by comparing aquatic communities of impacted streams with those of control streams. Control streams were chosen through the use of a technique that identifies similar streams based on similarities in their watershed characteristics. Significant differences between impacted and control sites existed for surface substrate, riparian vegetation, and the number of macroinvertebrate taxa. These results revealed that: (a) chemical and physical habitats at the impacted sites were disrupted, (b) the presence of trout was an inadequate measure of ecological integrity for these sites, and (c) watershed classification based on a combination of mapped terrestrial characteristics provided a reasonable method to select control sites where potential control sites upstream and downstream were unsuitable. 相似文献
132.
133.
搞好综合开发是建设现代化农业的战略措施之一,而要搞好综合开发,必先搞好农业区域开发规划。本文根据涟水地区的自然资源、社会经济条件和市场对农副产品及其制品需求出发,把涟水县域划分为2个开发区域,从分析开发的潜力入手,通过投资和效益的分析,提出了区域近、远期的开发目标、步骤和相应的开发措施。 相似文献
134.
本文把模糊线性规划方法引入灾害对策的研究当中。着重讨论了疏散人口和疏散地点间的关系,简单介绍了模糊疏散距离及其初步确定方法。 相似文献
135.
目的研究低成本高效慢速烤燃试验方法。方法利用自主研发的一套慢速烤燃试验装置,以1℃/min和3.3℃/h升温程序作为对比试验,设置几种三阶段升温程序,对JBO-9013和JH-14炸药进行慢速烤燃试验,以此获得不同升温程序下试样的响应温度和响应等级。结果 1℃/min、3.3℃/h、三阶段(100/150/193℃)升温程序下,JBO-9013响应温度分别为243.1、199.5、199.8、201.4、193.0℃,响应等级均为燃烧反应;JH-14响应温度分别为211.0、186.0、191.7℃,响应等级均为爆轰反应。结论升温程序对JBO-9013和JH-14响应温度和响应剧烈程度均有影响。与GJB8018—2013中1℃/min升温程序相比,三阶段升温程序与MIL-STD-2105D和STANAG 4439中3.3℃/h烤燃试验结果吻合度较高。因此,三阶段升温程序具有缩短试验周期、提高试验效率和降低试验成本的作用。 相似文献
136.
于连荣 《中国人口.资源与环境》1996,6(4):51-55
社会主义市场经济体制的建立和完善,给计划生育工作带来了一系列的新情况、新问题。因此,把计划生育工作纳入法制的轨道显得尤为重要。本文分析了我国计划生育工作靠行政约束的局限性;总结了市场经济体制下,计划生育工作面临的新特点;阐述了加强计划生育法制建设的紧迫性和可行性;并提出了计划生育立法的基本思路 相似文献
137.
An 11-year period of water quality data, collected by the Directorate of Sate Water Works of Turkey are thoroughly analyzed
for the purpose of implementing water quality classes to water resources in the Meric Basin, located on the European land
mass of Turkey. Water quality parameters are divided into four groups as physical, organic, inorganic, and bacteriological.
The quality class of each group is evaluated by taking into account the poorest quality of any parameter in the group, after
which a quality rank is assigned to the sampling station and the waterbody in question. This method of water quality classification
imposed by the Turkish Water Quality Act, is then criticized with respect to a statistical approach. 相似文献
138.
PROBLEM: After decreasing to a historic low in 1997, motorcycle crash-related fatalities are increasing. Although causes remain unclear, motorcycle rider education and licensing play key roles in reducing motorcycle crashes and injuries. Yet, little is known about what constitutes effective rider training and licensing. This study develops a model of best practices in motorcycle rider education and licensing and combines primary and secondary data to identify states that most closely adhere to this model. Evidence on the validity of the model is also examined. METHOD: States were rated along three areas of best practices: (a) program administration; (b) rider education; and (c) licensing based on 2001 data collected for a National Highway Traffic Safety Administration (NHTSA)-sponsored study. RESULTS: Results indicate wide variation in states' adherence to best practices; several states meet most, others very few. When the areas of best practices are considered separately, a state tends to behave similarly on all three. Initial evidence supports the validity of the model, with high best practices states having the lowest rates of motorcycle fatalities. IMPACT ON TRAFFIC SAFETY: As motorcycle-related crashes increase and state and federal support for rider education programs diminishes, it is critical that states identify deficiencies in their program and learn from successful states about efficient, cost-effective strategies for increasing best practices in motorcycle rider education and licensing. 相似文献
139.
Leakage diagnosis of hydrocarbon pipelines can prevent environmental and financial losses. This work proposes a novel method that not only detects the occurrence of a leakage fault, but also suggests its location and severity. The OLGA software is employed to provide the pipeline inlet pressure and outlet flow rates as the training data for the Fault Detection and Isolation (FDI) system. The FDI system is comprised of a Multi-Layer Perceptron Neural Network (MLPNN) classifier with various feature extraction methods including the statistical techniques, wavelet transform, and a fusion of both methods. Once different leakage scenarios are considered and the preprocessing methods are done, the proposed FDI system is applied to a 20-km pipeline in southern Iran (Goldkari-Binak pipeline) and a promising severity and location detectability (a correct classification rate of 92%) and a low False Alarm Rate (FAR) were achieved. 相似文献
140.