全文获取类型
收费全文 | 508篇 |
免费 | 37篇 |
国内免费 | 67篇 |
专业分类
安全科学 | 72篇 |
废物处理 | 11篇 |
环保管理 | 109篇 |
综合类 | 209篇 |
基础理论 | 102篇 |
污染及防治 | 14篇 |
评价与监测 | 29篇 |
社会与环境 | 25篇 |
灾害及防治 | 41篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 14篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 24篇 |
2015年 | 22篇 |
2014年 | 21篇 |
2013年 | 29篇 |
2012年 | 43篇 |
2011年 | 37篇 |
2010年 | 22篇 |
2009年 | 35篇 |
2008年 | 16篇 |
2007年 | 35篇 |
2006年 | 35篇 |
2005年 | 15篇 |
2004年 | 12篇 |
2003年 | 14篇 |
2002年 | 15篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 7篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 16篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 3篇 |
排序方式: 共有612条查询结果,搜索用时 15 毫秒
521.
522.
大震灾害会导致工业企业遭受惨重经济损失。为了推进灾区恢复生产和重建工作的顺利开展,快速评估工业企业地震直接经济损失具有重要意义,而我国目前尚未有成熟的针对工业企业的统一评价方法。在总结国内外地震直接经济损失评估成果的基础上,从财务会计的角度提出了一种估算工业企业各项地震易损资产项目经济损失值的方法,详细阐述了各项参数的内涵,提出如何在实际应用中确定各参数数值,并结合汶川地震黑色金属冶炼及压延加工行业地震损失案例简要说明了评估过程。结果表明,该方法将大大提升灾损评估的时效性。 相似文献
523.
为减小压力容器气体泄漏实时位置估算误差,准确监测容器工况,首先,从声学监测角度提出一种引入鲸鱼优化算法(WOA)的泄漏源估计方法,采用波达方向(DOA)估计法预测气体泄漏位置方向,获得泄漏源角坐标;然后,引入WOA自适应选择方法分解DOA的特征值,多次迭代得到最精确的泄漏位置;最后,以某化工厂中压力容器数据为实际算例,... 相似文献
524.
闵文彬 《长江流域资源与环境》2016,25(4):606-612
空气动力学阻抗的准确估算是目前卫星反演地表显热通量的关键,为了准确反演藏东南地区的地表显热通量,利用2013年6月10日西藏林芝地区的草地、麦田、河滩、林地阴坡和阳坡5种下垫面的边界层观测数据,分析常用的Thom_1975,Thom_1977和Choudhury空气动力学阻抗估算模型的适应性。结果表明:林地阴坡Choudhury模型估算值与涡动相关测量的结果有较好的一致性,其他下垫面建议采用Thom(1975)模型。 相似文献
525.
TIAN Ke-jun LIU Xin-ai JIANG Tao M.D. Kennedy J.C. Schippers P.A. Vanrolleghem 《环境科学学报(英文版)》2004,16(6):1020-1023
Membrane bioreactors(MBRs) are attracting global interest but the mathematical modeling of the biological performance of MBRs remains very limited. This study focuses on the modelling of a side-stream MBR system using Activated Sludge Model No. 1 (ASM1), and comparing the results with the modelling of traditional activated sludge processes. ASM1 parameters relevant for the long-term biological behaviour in MBR systems were calibrated(i, e. YH = 0.72gCOD/gCOD, YA = 0.25gCOD/gN, bH = 0.25 d^-1, bA = 0.080 d^-1 and fp =0.06), and generally agreed with the parameters in traditional activated sludge processes, with the exception that a higher autotrophic biomass decay rate was observed in the MBR. A sensitivity analysis for steady state operation and DO dynamics suggested that the biological performance of the MBR system (the sludge concentration, effluent quality and the DO dynamics) are very sensitive to the parameters(i.e. YH, YA, bH, hA, μmaxH and μmaxA), and influent wastewater components( X1, Ss, Xs, SNH). 相似文献
526.
ABSTRACTIn this study, a Stirling engine with a free-displacer and a kinematically controlled power piston was proposed and analyzed from thermodynamic and dynamic points of view. The analysis intended to reveal the dynamic behaviors of moving components of the engine as well as predicting global thermal performance of it. A dynamic-thermodynamic mathematical model of the engine involving the isothermal gas pressure equation and motion equations of the displacer, power piston and crankshaft was developed. For the solution of the dynamic-thermodynamic model equations, and simulation of the engine’s running, a computer program was prepared in FORTRAN language. By considering a hot-end temperature of 1,000 K and a cold-end temperature of 350 K, dimensions of mechanic, volumetric and thermal components of the engine were quantified interactively. Variations of engine speed, engine power, displacer stroke, and engine torque were examined with respect to the spring constant, displacer mass, displacer damping constant and external load and, results were graphically presented. In comparison with engines having free-piston and kinematically driven displacer, the thermodynamic performance of the free-displacer engine was found to be lower. The engine was found to be able to work at constant speed and power. The values of the displacer mass and spring constant were optimized as 1,500 g and 1,30,000 N/s, respectively and the global speed of the engine was determined to be 47.75 Hz for these values. The effective and the indicated work of the engine were determined to be 113 and 126 J, respectively. 相似文献
527.
As an effective way to construct and maintain various life pipelines in urban areas and industrial parks, the underground utility tunnel has been developed rapidly in China in recent years. However, the natural gas pipeline leakage in a utility tunnel may cause fire, explosion or other coupling disastrous accidents that could result in fatal consequences. The effective source term estimation (STE) of natural gas leakage can provide technical supports for emergency response during natural gas leakage accidents in utility tunnels. In this paper, a STE model with the combination of gas transport model, Bayesian inference and slice sampling method is proposed to estimate the source parameters of natural gas leakage in underground utility tunnels. The observed data can be integrated into the gas transport model and realize the inversion of natural gas leakage location and release rates. The parameter sensitivity analysis is presented to evaluate the robustness of the proposed model with good practicability, and the gas sensor layouts in the utility tunnel are analyzed and optimized. The spatio-temporal distribution of the leaked gas could be well predicted based on the estimation source parameters by the proposed STE model. The results show that the proposed model is an alternative and effective tool to provide technical supports for loss prevention and mitigation for natural gas leakage accidents in urban utility tunnels. 相似文献
528.
Vicente L. Lopes Adrian L. Vogl 《Journal of the American Water Resources Association》2008,44(5):1284-1294
Abstract: Determining watershed response to vegetation treatment has been the subject of numerous hydrologic studies over the years. However, generalizing the information obtained from traditional paired‐watershed studies to other watersheds in a region is problematic because of the empirical nature of such studies and the context dependence of hydrologic responses. This paper addresses the issue of generalizing hydrologic information through integration of process‐based modeling and field observations from small‐scale watershed experiments. To this end, the results from application of a process‐based model were compared with the results from small‐scale watershed experiments in ponderosa pine forests of Arizona. The model simulated treatment impacts reasonably well when compared to the traditional paired‐watershed approach. However, the model tended to overestimate water yields during periods of low flow, and there was a significant difference between the two approaches in the estimation of treatment impacts during the first four years following treatment. The results indicate that the lumped‐parameter modeling approach used here may be limited in its ability to detect small changes, and tends to overestimate changes that occur immediately following treatment. It is concluded that watershed experiments can be highly informative due to their direct examination of cause‐effect relationships, while process‐based models are useful for their processing power and focus on functional relationships. The integrated use of both watershed experiments and process‐based models provides a way to generalize hydrologic information, illuminate the processes behind landscape treatment effects, and to generate and test hypotheses. 相似文献
529.
带有阶跃函数的GIM(1)预测模型及其应用 总被引:1,自引:0,他引:1
结合某水域地面水ROD5的预测实践,研究提出了带有阶跃函数的GIM(1)预测模型,并给出了估计这种模型参数的简便方法,从而扩大了GIM(1)模型在环境系统中的应用范围,实例表明,运用该方法得到的模型比常规GIM(1)具有更高的精度。 相似文献
530.
介绍了 2种不同方法分析估算的中国农田 N2 O的排放结果 ,并讨论了减缓农田 N2 O排放的对策。用田间测量数据和 IPCC第二阶段方法学估算的中国农田 1995年 N2 O的直接排放量 (以 N计 )分别为 398和 336Gg。应用 IPCC第二阶段方法学分别计算了 194 9年等 10个年份进入中国农田的不同氮源的数量变化 ,表明化学氮肥施用量的增加是中国农田 N2 O排放量逐年上升的主要因素。田间观测结果表明 ,水田是 N2 O不可忽视的源。中国水田 N2 O排放量约占中国农田总排放量的 2 2 % ,水稻生长季水田 N2 O排放量约占农田总排放量的 9%。根据中国农作制 ,施肥和农田水分管理方面的特点 ,调整 N∶P∶ K肥料的比率 ,缩小全国氮肥施用量的地区性差异及应用硝化抑制剂和包膜缓释氮肥 ,将有助于减少农田 N2 O的排放量。 相似文献