全文获取类型
收费全文 | 1133篇 |
免费 | 167篇 |
国内免费 | 200篇 |
专业分类
安全科学 | 271篇 |
废物处理 | 28篇 |
环保管理 | 318篇 |
综合类 | 522篇 |
基础理论 | 116篇 |
污染及防治 | 82篇 |
评价与监测 | 72篇 |
社会与环境 | 54篇 |
灾害及防治 | 37篇 |
出版年
2024年 | 4篇 |
2023年 | 34篇 |
2022年 | 30篇 |
2021年 | 55篇 |
2020年 | 52篇 |
2019年 | 46篇 |
2018年 | 30篇 |
2017年 | 61篇 |
2016年 | 88篇 |
2015年 | 75篇 |
2014年 | 61篇 |
2013年 | 97篇 |
2012年 | 112篇 |
2011年 | 96篇 |
2010年 | 66篇 |
2009年 | 64篇 |
2008年 | 37篇 |
2007年 | 65篇 |
2006年 | 65篇 |
2005年 | 45篇 |
2004年 | 27篇 |
2003年 | 42篇 |
2002年 | 29篇 |
2001年 | 34篇 |
2000年 | 14篇 |
1999年 | 16篇 |
1998年 | 11篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 4篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 6篇 |
1971年 | 11篇 |
1970年 | 4篇 |
排序方式: 共有1500条查询结果,搜索用时 484 毫秒
891.
892.
北京城市声环境自动监测系统监测点位布设方法初探 总被引:2,自引:0,他引:2
噪声自动监测相对手工监测而言,更能真实反映城市声环境质量,随着噪声自动监测技术的不断完善,自动监测替代手工监测已成为必然趋势.但目前我国城市声环境自动监测系统正处于起步阶段,国内还没有对声环境自动监测系统的点位布设提出成熟、合理的方案.文章结合北京市声环境自动监测系统建设的实际工作情况,对监测系统总体框架、自动监测点位布设的原则及方法等进行了阐述并提出近期需要解决的问题. 相似文献
893.
应用全场数学模型模拟了深圳排海的市政污水中悬浮物、化学需氧量、无机氮、活性磷酸盐及大肠菌群5个污染因子在海域大潮和小潮时对海域面积的影响。指出在不同水文条件和23m^3/d排放量下,不同质量浓度的活性磷酸盐和大肠菌群超过Ⅲ类海水水质标准的影响面积在大潮时分别为0.04km^2和7.72km^2,小潮时分别大于0.08km^2和6.16km^2;无机氮由于海水本底值较高,使得这一指标在全海域内超过Ⅲ类海水水质标准;而化学需氧量和总悬浮物质量浓度符合Ⅲ类海水水质标准。通过将现场监测资料用数模计算,提出排海污水混合区面积为1.5km^2。同时还引用部分国外的计算公式,对几种混合区允许范围进行了估算。 相似文献
894.
Chung-Huey Wu Aaron J. Dodd Cindy E. Hauser Michael A. McCarthy 《Conservation biology》2021,35(3):955-966
Conserving biodiversity and combating ecological hazards require cost-effective allocation of limited resources among potential management projects. Project priorities, however, can change over time as underlying social-ecological systems progress, novel priorities emerge, and management capabilities evolve. Thus, reallocation of ongoing investments in response to shifting priorities could improve management outcomes and address urgent demands, especially when additional funding is not available immediately. Resource reallocation, however, could incur transaction costs, require additional monitoring and reassessment, and be constrained by ongoing project commitments. Such complexities may prevent managers from considering potentially beneficial reallocation strategies, reducing long-term effectiveness. We propose an iterative project prioritization approach, based on marginal return-on-investment estimation and portfolio optimization, that guides resource reallocation among ongoing and new projects. Using simulation experiments in 2 case studies, we explored how this approach can improve efficacy under varying reallocation constraints, frequencies, costs, and rates of project portfolio change. Periodic budget reallocation could enhance the management of stochastically emerging invasive weeds in Australia and thus reduce the overall risk by up to 50% compared with a static budget. Reallocation frequency and the rate of new weed incursion synergistically increased the conservation gains achieved by allowing unconstrained reallocation. Conversely, budget reallocation would not improve the International Union for Conservation of Nature conservation status of threatened Australian birds due to slow rates of transition among conservation states; extinction risk could increase if portfolio reassessment is costly. Although other project prioritization studies may recommend periodic reassessment and reallocation, our findings revealed conditions when reallocation is valuable and demonstrated a structured approach that can help conservation agencies schedule and implement iterative budget-allocation decisions cost-effectively. 相似文献
895.
896.
针对影响航行安全的动态危险天气,提出了一种基于改进多目标粒子群算法的改航路径规划方法。首先,获取实时动态气象数据,利用栅格法对改航环境进行建模并采集危险天气区域初始边界点的历史气象数据。然后采用灰色预测模型对上述初始边界点坐标进行位置预测,进而建立改进后的实时动态环境模型。最后利用改进环境模型的多目标粒子群算法对改航路径进行动态规划。在考虑改航路径角度和距离等约束条件的基础上,确定了改航路径危险系数和距离最优的双目标函数。对中东部沿海某次短时危险天气下的航空器改航进行仿真分析,仿真结果表明改进后算法具有一定的有效性和可行性。 相似文献
897.
Use of GIS in siting stabilization pond facilities for domestic wastewater treatment 总被引:1,自引:0,他引:1
Gemitzi A Tsihrintzis VA Christou O Petalas C 《Journal of environmental management》2007,82(2):155-166
Geographic information systems (GIS) use is presented in the problem of sitting areas for construction of natural systems such as stabilization ponds (SPs) for domestic wastewater treatment. For this purpose, several variables, such as topography, land use, type of geological formation, distance to major rivers or lakes, distance to existing cities and villages, existence of environmentally protected areas, mean minimum monthly temperatures and required wastewater effluent characteristics were analyzed with the GIS, in order to accept or reject a particular area within a region. The method is applied in the region of Thrace (Northeast Greece) at the municipal level. The required area for SP systems was calculated in each of the 36 municipalities of Thrace (including two islands, Thassos and Samothraki) as a function of the population of each municipality, temperature and local wastewater effluent discharge criteria. Based on the GIS analysis, suitable locations were identified in each municipality first, and then the total required surface area of these systems was compared to the available surface area of each municipality, in order to decide whether SP systems could be a viable solution to the wastewater management problem in the particular region. In that way the present methodology offers a fast and simple method to check the suitability of new areas for construction of such systems. 相似文献
898.
Habitat protection for grassland birds is an important component of open space land acquisition in suburban Chicago. We use
optimization decision models to develop recommendations for land protection and analyze tradeoffs between alternative goals.
One goal is to acquire (and restore if necessary) as much grassland habitat as possible for a given budget. Because a viable
habitat for grassland birds consists of a relatively large core area with additional parcels of grassland habitat nearby,
the second goal is to minimize total pairwise distance between newly protected parcels and large existing reserves. We also
use the concept of an effective grassland habitat area, which considers influences that neighboring land covers have on grassland
habitat suitability. We analyze how the parcels selected for protection change as total protected effective area is traded
off against total distance. As area is weighted more heavily, the selected parcels are scattered and unconnected. As total
distance is weighted more heavily, the selected parcels coalesce around core reserves but protect less area. The differences
in selected parcels as we change the objective function weights are caused by the differences in price per unit of effective
habitat area across parcels. Parcels located in close proximity to the existing cores have relatively high prices per hectare
of effective grassland area as a consequence of high restoration costs and adverse influences from roads, urban areas and/or
forestland. As a result, these parcels have lower priority for selection when the area objective is weighted more heavily
for a given budget. 相似文献
899.
Fee-fishing involves paying a fee for the privilege of fishing a body of water where fish populations are enhanced by stocking
fish. Past literature on this activity has focused more on the operation of the enterprise and management of the fish than
the people and site characteristics. The objectives of the study were to profile anglers and describe their site/management
preferences. This study utilized an on-site interview and mail-back questionnaire at fee-fishing establishments in West Virginia
(n = 212). Factor analysis of desired recreation experiences yielded five factors: Experience nature & adventure, Stress release & relaxation, Trophy fishing, Escape, and Family time. Cluster analysis showed that these anglers can be segmented into two distinct clusters, differing by sociodemographic characteristics,
fishing behavior, and site/management preferences. The findings from this study provide baseline data to aid public resource
managers and fee-fishing business owners in determining how to provide satisfying outdoor experiences and deliver desired
services on-site. Future research will be needed from additional fee-fishing sites to obtain more detail about this outdoor
recreation cohort and be able to generalize to a larger population of participants. 相似文献
900.
结合“大大连”建设的规划和“十五”及2010年远景规划,选取了人口、国内生产总值、公共绿地面积三个决策变量建立目标规划模型,采取3种方案对大连市水资源承载力进行预测,通过对预测结果的分析并结合水资源承载力的特点提出增强水资源承载力的方案:以可持续发展的观点来设计城市发展规划;调整和改造产业结构;改变城市绿化结构;兴修水利,发展节水技术达到水资源可持续利用。 相似文献