全文获取类型
收费全文 | 1024篇 |
免费 | 52篇 |
国内免费 | 98篇 |
专业分类
安全科学 | 103篇 |
废物处理 | 19篇 |
环保管理 | 303篇 |
综合类 | 202篇 |
基础理论 | 340篇 |
环境理论 | 1篇 |
污染及防治 | 82篇 |
评价与监测 | 57篇 |
社会与环境 | 47篇 |
灾害及防治 | 20篇 |
出版年
2023年 | 16篇 |
2022年 | 14篇 |
2021年 | 32篇 |
2020年 | 31篇 |
2019年 | 21篇 |
2018年 | 15篇 |
2017年 | 21篇 |
2016年 | 37篇 |
2015年 | 24篇 |
2014年 | 26篇 |
2013年 | 60篇 |
2012年 | 29篇 |
2011年 | 72篇 |
2010年 | 46篇 |
2009年 | 78篇 |
2008年 | 61篇 |
2007年 | 58篇 |
2006年 | 76篇 |
2005年 | 57篇 |
2004年 | 36篇 |
2003年 | 35篇 |
2002年 | 40篇 |
2001年 | 27篇 |
2000年 | 34篇 |
1999年 | 14篇 |
1998年 | 23篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 12篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1972年 | 7篇 |
1971年 | 5篇 |
1970年 | 3篇 |
排序方式: 共有1174条查询结果,搜索用时 515 毫秒
781.
国外泥石流机理模型综述 总被引:7,自引:2,他引:7
综述了国外与机理有关的几个主要泥石流运动模型。建议近期泥石流运动机理研究宜着重厘定各类模型的适用范围和比较它们的应用结果,并进一步简化现有的机理模型,为泥石流防治工程提供具有一定理论基础和科学依据的流速、流量和冲击力等关键设计参数。与泥石流机理密切相关的预测预报,宜着重于泥石流的中长期预测和预警报,重点突破泥石流规模和发生频率相互关系的问题。 相似文献
782.
The fire simulation processes of the National Fire Management System's (NFMAS) Initial Attack Analysis (IAA) processor were
evaluated by conducting two types of sensitivity analysis: one based on a hypothetical set of data to assess IAA's outputs
under a wide range of fire input values, and the other using an actual Stanislaus National Forest database to test IAA's validity
with a real set of data. The results revealed that IAA's outputs (projected annual number of fires and area burned) were most
sensitive, in descending order, to the input values of the fire spread rate, the productivity rates of the suppression forces,
and the initial attack time, for all fuel models tested. In contrast, IAA's outputs were extremely insensitive to variations
in the fire size at discovery. Changes are necessary in the ways IAA incorporates the fire size at discovery to facilitate
the comparison among various fire detection options. The program's “escaped fire situation” analysis was found inadequate,
because the projected annual frequencies and final sizes of the simulated escaped fire events produced unacceptable results
with the Stanislaus National Forest database. Assigning final sizes to simulated escaped fires according to the fire intensity
level in which they are historically expected to occur provides a consistent way of calculation of the projected annual area
burned and the consequent cost plus net value change (C + NVC). 相似文献
783.
Quantitative structure-activity relationships (QSARs)were developed for 43 aromatic compounds toxicity to Photobacterium phosphoreum and Daphnia magna based on four methods: octanol/water partition coefficient, linear solvation energy relationship, molecular connectivity index and group contribution. Through the evaluation of four QSAR methods, LSER was proved to be the best. And it applied to the widest range of chemicals with the greatest accuracy. 相似文献
784.
Numerical simulation of a combined oxidation ditch flow using 3D k-εturbulence model 总被引:1,自引:0,他引:1
The standard three dimensional(3D) k-ε turbulence model was applied to simulate the flow field of a small scale combined oxidation ditch. The moving mesh approach was used to model the rotor of the ditch. Comparison of the computed and the measured data is acceptable. A vertical reverse flow zone in the ditch was found, and it played a very important role in the ditch flow behavior. The flow pattern in the ditch is discussed in detail, and approaches are suggested to improve the hydrodynamic performance in the ditch. 相似文献
785.
珠江口区域海上溢漏污染物动态预测系统的开发与应用 总被引:2,自引:0,他引:2
为了对《珠江口区域溢油应急计划》提供决策支持,在国内外最新研究成果基础上,针对珠江口海域的环境特点研究开发了先进实用的“珠江口区域海上溢漏污染动态预测系统”,综合有三维潮流模型、三维溢油与化学品漂移扩散模型、溢油风化模型、应急反应模型、以及电子海图、地理信息系统(GIS)、数据库等关键技术,能够快速准确地预测并可视化显示不同种类的溢漏油品、化学品在水面及水体中的漂移扩散范同和性质变化过程,还可以同时显示环境敏感区和应急人员设备分布等相关信息。经实际溢油案例应用表明,系统的预测结果与现场实际情况相符。此系统的成功开发应用将有效地提高对船舶污染事故的应急指挥效率。 相似文献
786.
Michel Jan Niklas Cathy Trudinger Jason Lowe Ben Matthews Brd Romstad Christiano Pires de Campos Natalia Andronova 《Environmental Science & Policy》2005,8(6):614
This paper evaluates the influence of different policy-related and scientific choices on the calculated regional contributions to global climate change (the “Brazilian Proposal”). Policy-related choices include the time period of emissions, the mix of greenhouse gases and different indicators of climate change impacts. The scientific choices include historical emissions and model representations of the climate system. We generated and compared results of several simple climate models. We find that the relative contributions of different nations to global climate change—from emissions of greenhouse gases alone—are quite robust, despite the varying model complexity and differences in calculated absolute changes. For the default calculations, the average calculated contributions to the global mean surface temperature increase in 2000 are about 40% from OECD, 14% from Eastern Europe and Former Soviet Union, 24% from Asia and 22% from Africa and Latin America. Policy-related choices, such as time period of emissions, climate change indicator and gas mix generally have larger influence on the results than scientific choices. More specifically, choosing a later attribution start date (1990 instead of 1890) for historical emissions, decreases the contributions of regions that started emitting early, such as the OECD countries by 6 percentage points, whereas it increases the contribution of late emitters such as Asia by 8 percentage points. However, only including the fossil CO2 emissions instead of the emissions of all Kyoto gases (fossil and land use change), increases the OECD contributions by 21 percentage points and decreases the contribution of Asia by 14 percentage points. 相似文献
787.
北京市大气环境二氧化硫浓度分布初探 总被引:1,自引:0,他引:1
利用北京市大气自动监测系统冬季逐时二氧化硫浓度监测资料,分析研究了对数正态分布,Weibull分布,指数分布等常用分布模型对监测资料人布推迟合的适用性,并估算出各种分布模型的参数值。研究发现城区及高百分位数二氧化硫浓度频率分布符合Weibull分布,近郊及背景站的浓度分布符合常用的对数正态分布,二氧化硫浓度的频率分布不符合指数分布规律。 相似文献
788.
789.
790.
We borrow a frontier specification from the econometrics literature to make inferences about the tolerance of the tapir to
human settlements. We estimate the width of an invisible band surrounding human settlements which would act as a frontier
or exclusion zone to the tapir to be around 290 metres. 相似文献