全文获取类型
收费全文 | 2600篇 |
免费 | 455篇 |
国内免费 | 356篇 |
专业分类
安全科学 | 886篇 |
废物处理 | 51篇 |
环保管理 | 788篇 |
综合类 | 868篇 |
基础理论 | 299篇 |
污染及防治 | 212篇 |
评价与监测 | 109篇 |
社会与环境 | 57篇 |
灾害及防治 | 141篇 |
出版年
2024年 | 5篇 |
2023年 | 54篇 |
2022年 | 105篇 |
2021年 | 126篇 |
2020年 | 114篇 |
2019年 | 114篇 |
2018年 | 72篇 |
2017年 | 127篇 |
2016年 | 153篇 |
2015年 | 166篇 |
2014年 | 124篇 |
2013年 | 129篇 |
2012年 | 206篇 |
2011年 | 192篇 |
2010年 | 139篇 |
2009年 | 189篇 |
2008年 | 124篇 |
2007年 | 147篇 |
2006年 | 133篇 |
2005年 | 119篇 |
2004年 | 79篇 |
2003年 | 107篇 |
2002年 | 101篇 |
2001年 | 71篇 |
2000年 | 83篇 |
1999年 | 62篇 |
1998年 | 50篇 |
1997年 | 34篇 |
1996年 | 44篇 |
1995年 | 27篇 |
1994年 | 23篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 13篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有3411条查询结果,搜索用时 30 毫秒
991.
992.
Cyclic volatile methylsiloxanes (cVMS) such as octamethycyclotetrasiloxane (D4), decamethycyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) are widely used as intermediates in the synthesis of high-molecular weight silicone polymers or as ingredients in the formulation of personal care products. The global environmental fate, latitudinal distribution, and long range transport of those cVMS were analyzed by two multimedia chemical fate models using the best available physicochemical properties as inputs and known persistent organic pollutants (POPs) and highly persistent volatile organic chemicals (“fliers”) as reference. The global transport and accumulation characteristics of cVMS differ from those of typical POPs in three significant ways. First, a large fraction of the released cVMS tends to become airborne and is removed from the global environment by degradation in air, whereas known POPs have a tendency to be distributed and persistent in all media. Secondly, although cVMS can travel a substantial distance in the atmosphere, they have little potential for deposition to surface media in remote regions. This contrasts with a deposition potential of known POPs that exceeds that of cVMS by 4–5 orders of magnitude. Thirdly, cVMS have short global residence times with the majority of the global mass removed within 3 months of the end of release. Global residence times of POPs on the other hand are in years. The persistent fliers resemble the cVMS with respect to the first two attributes, but their global residence times are more like those of the POPs. 相似文献
993.
天津市空气污染预报方法 总被引:6,自引:2,他引:4
文章论述了空气污染预报几种理论和方法,特别详细介绍了天津市空气质量预报方法及其应用效果。 相似文献
994.
Numerical Investigation of Boundary-Layer Evolution and Nocturnal Low-Level Jets: Local versus Non-Local PBL Schemes 总被引:3,自引:0,他引:3
Kesu Zhang Huiting Mao Kevin Civerolo Stephen Berman Jia-Yeong Ku S. Trivikrama Rao Bruce Doddridge C. Russell Philbrick Richard Clark 《Environmental Fluid Mechanics》2001,1(2):171-208
Numerical simulations of the evolution of the planetary boundary layer (PBL) and nocturnal low-level jets (LLJ) have been carried out using MM5 (version 3.3) with four-dimensional data assimilation (FDDA) for a high pollution episode in the northeastern United States during July 15–20, 1999. In this paper, we assess the impact of different parameterizations on the PBL evolution with two schemes: the Blackadar PBL, a hybrid local (stable regime) and non-local (convective regime) mixing scheme; and the Gayno–Seaman PBL, a turbulent kinetic energy (TKE)-based eddy diffusion scheme. No FDDA was applied within the PBL to evaluate the ability of the two schemes to reproduce the PBL structure and its temporal variation. The restriction of the application of FDDA to the atmosphere above the PBL or the lowest 8 model levels, whichever is higher, has significantly improved the predicted strength and timing of the LLJ during the night. A systematic analysis of the PBL evolution has been performed for the primary meteorological fields (temperature, specific humidity, horizontal winds) and for the derived parameters such as the PBL height, virtual potential temperature, relative humidity, and cloud cover fraction. There are substantial differences between the PBL structures and evolutions simulated by these two different schemes. The model results were compared with independent observations (that were not used in FDDA) measured by aircraft, RASS and wind profiler, lidar, and tethered balloon platforms during the summer of 1999 as part of the NorthEast Oxidant and Particle Study (NE-OPS). The observations tend to support the non-local mixing mechanism better than the layer-to-layer eddy diffusion in the convective PBL. 相似文献
995.
996.
官地水库的库首由雅砻江自身河弯形成了一个近东西向的单薄分水岭,该分水岭南北方向上长仅1 880m,沿南北向展布的石炭系-二叠系碳酸盐岩贯穿了水库内外,构成了潜在的库水外渗通道.笔者在现场地质、水文地质调查和观测资料综合分析的基础上,构建了该地区的水文地质概念模型,运用数值模拟方法对天然和水库正常蓄水条件下的地下水流场特征进行了模拟,通过对不同条件下地下水流场特征的分析研究,认为天然条件下地下水分水岭已经消失,水库正常蓄水条件下存在水库渗漏问题.水库正常蓄水条件下地下水渗流场的模拟结果表明,其水库渗漏量约3 670 m3/d,其中通过平川组上段、马坪组中段和阳新组上段地层渗漏的水量约占总渗漏量的77%,因此防渗的关键是封堵这三套地层. 相似文献
997.
998.
Mechanistic Virtual Modeling: Coupling a Plant Simulation Model with a Three-dimensional Plant Architecture Component 总被引:3,自引:0,他引:3
Eric Jallas Ron Sequeira Pierre Martin Sam Turner Petraq Papajorgji 《Environmental Modeling and Assessment》2009,14(1):29-45
The aim of this research is to integrate plant architectural modeling or “visualization modeling” and “mechanistic” or physiologically
based modeling to describe how a real plant functions using a virtual crop. Virtual crops are life-like computer representations
of crops based on individual plants and including the representation of the substrate on which the plants grow. The integration
of a three-dimensional expression and the mechanistic model of plant development and growth requires the knowledge of the
position of the organs along the different plant axes (the topology), their sizes, their forms, and their spatial orientation.
The plant simulation model simulates the topology and organ weight or length. The superposition of spatial position and the
topology produces the architecture of the plant. The association between sizes and organs creates what we refer to as the
plant morphological model. Both components, the architectural model and the morphology model, are detailed in this paper.
Once the integration is complete, the system produces a movie-like animation that shows the plant growing. The integrated
model may simulate one or several plants growing simultaneously (in parallel). Visual capabilities make the proposed system
very unique as it allows users to judge the results of the simulation the same way a farmer judges the situation of the crops
in real life, by visually observing the field. 相似文献
999.
Evaluating Spatio-temporal Complexities of Forest Management: An Integrated Agent-based Modeling and GIS Approach 总被引:1,自引:0,他引:1
The objective of this study is to integrate agent-based modeling and geographic information systems (GIS) for examining how
interactions within forest management lead to patterns of land-cover change. Specifically, this study evaluates how management
agents behave in the presence of variable timber prices, harvesting costs, and accessibility to timber and how their actions
influence the spatial characteristics of the forest landscape over time. The GIS calculates the average harvested patch size,
number of patches, and total harvested area as measures of emergent patterns resulting from agent actions. The results from
the agent-based GIS model reveal that good economic conditions lead to few but large harvested patches, while deteriorating
conditions will see more patches of smaller size if forest companies have access to high-quality timber. This study emphasizes
the need for a complex systems approach to forest management as the model illustrates how system elements interact in a manner
to produce emergent spatial patterns over time. 相似文献
1000.
Modeling Runoff Response to Land Cover and Rainfall Spatial Variability in Semi-Arid Watersheds 总被引:5,自引:0,他引:5
Mariano Hernandez Scott N. Miller David C. Goodrich Bruce F. Goff William G. Kepner Curtis M. Edmonds K. Bruce Jones 《Environmental monitoring and assessment》2000,64(1):285-298
Hydrologic response is an integrated indicator of watershed condition, and significant changes in land cover may affect the overall health and function of a watershed. This paper describes a procedure for evaluating the effects of land cover change and rainfall spatial variability on watershed response. Two hydrologic models were applied on a small semi-arid watershed; one model is event-based with a one-minute time step (KINEROS), and the second is a continuous model with a daily time step (SWAT). The inputs to the models were derived from Geographic Information System (GIS) theme layers of USGS digital elevation models, the State Soil Geographic Database (STATSGO) and the Landsat-based North American Landscape Characterization classification (NALC) in conjunction with available literature and look up tables. Rainfall data from a network of 10 raingauges and historical stream flow data were used to calibrate runoff depth using the continuous hydrologic model from 1966 to 1974. No calibration was carried out for the event-based model, in which six storms from the same period were used in the calculation of runoff depth and peak runoff. The assumption on which much of this study is based is that land cover change and rainfall spatial variability affect the rainfall-runoff relationships on the watershed. To validate this assumption, simulations were carried out wherein the entire watershed was transformed from the 1972 NALC land cover, which consisted of a mixture of desertscrub and grassland, to a single uniform land cover type such as riparian, forest, oak woodland, mesquite woodland, desertscrub, grassland, urban, agriculture, and barren. This study demonstrates the feasibility of using widely available data sets for parameterizing hydrologic simulation models. The simulation results show that both models were able to characterize the runoff response of the watershed due to changes of land cover. 相似文献