首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1077篇
  免费   23篇
  国内免费   13篇
安全科学   31篇
废物处理   16篇
环保管理   138篇
综合类   98篇
基础理论   481篇
环境理论   1篇
污染及防治   266篇
评价与监测   48篇
社会与环境   31篇
灾害及防治   3篇
  2023年   6篇
  2022年   3篇
  2021年   9篇
  2020年   10篇
  2019年   10篇
  2018年   20篇
  2017年   25篇
  2016年   26篇
  2015年   28篇
  2014年   49篇
  2013年   96篇
  2012年   39篇
  2011年   62篇
  2010年   52篇
  2009年   64篇
  2008年   51篇
  2007年   64篇
  2006年   56篇
  2005年   27篇
  2004年   26篇
  2003年   21篇
  2002年   30篇
  2001年   35篇
  2000年   29篇
  1999年   27篇
  1998年   16篇
  1997年   9篇
  1996年   8篇
  1995年   18篇
  1994年   14篇
  1993年   13篇
  1992年   19篇
  1991年   13篇
  1990年   17篇
  1989年   10篇
  1988年   11篇
  1987年   13篇
  1986年   8篇
  1985年   5篇
  1984年   15篇
  1983年   10篇
  1982年   4篇
  1981年   5篇
  1980年   3篇
  1979年   8篇
  1978年   6篇
  1977年   5篇
  1976年   4篇
  1975年   4篇
  1974年   4篇
排序方式: 共有1113条查询结果,搜索用时 15 毫秒
171.
The increase in volumes of waste, and the difficulties of finding suitable locations for landfill sites within the borders of Copenhagen municipality, along with the need for treatment of oil and chemical waste, resulted in the erection in the early 1970s of two large waste-to-energy plants and a large centralized plant for the treatment of oil and chemical waste. Ten years later, however, it became evident that the then structure was not sufficient to face rapidly emerging problems. A number of pollution cases in Denmark which emerged during the early 1980s, proved that oil and chemical waste was being transported illegally to landfills instead of being disposed of in compliance with the obligatory system, thus becoming a threat to groundwater and drinking water supplies in Copenhagen. At the same time, waste-to-energy plants were facing pollution problems such as the emission of dioxin and large quantities of hydrochloric acid, which contribute to acidification and forest death.As a response to the increasing problems in relation to both waste incineration and deposits, new regulations from the Ministry of the Environment allowed future sanitary landfills to be located only near the coast or in areas documented to be composed of an impermeable layer of clay. New regulation also defined conditions for flue gas cleansing. However, it was clear that pollution problems combined with increases in volumes of waste called for a much firmer administration and a stronger influence on the waste flow. From February 1989 the municipalities have undertaken the obligation to assign all waste producers the means to dispose of their waste. How Copenhagen municipality has solved the problems is discussed.  相似文献   
172.
Deep learning (DL) models are increasingly used to make accurate hindcasts of management-relevant variables, but they are less commonly used in forecasting applications. Data assimilation (DA) can be used for forecasts to leverage real-time observations, where the difference between model predictions and observations today is used to adjust the model to make better predictions tomorrow. In this use case, we developed a process-guided DL and DA approach to make 7-day probabilistic forecasts of daily maximum water temperature in the Delaware River Basin in support of water management decisions. Our modeling system produced forecasts of daily maximum water temperature with an average root mean squared error (RMSE) from 1.1 to 1.4°C for 1-day-ahead and 1.4 to 1.9°C for 7-day-ahead forecasts across all sites. The DA algorithm marginally improved forecast performance when compared with forecasts produced using the process-guided DL model alone (0%–14% lower RMSE with the DA algorithm). Across all sites and lead times, 65%–82% of observations were within 90% forecast confidence intervals, which allowed managers to anticipate probability of exceedances of ecologically relevant thresholds and aid in decisions about releasing reservoir water downstream. The flexibility of DL models shows promise for forecasting other important environmental variables and aid in decision-making.  相似文献   
173.
Assisted migration (AM) is the translocation of species beyond their historical range to locations that are expected to be more suitable under future climate change. However, a relocated population may fail to establish in its donor community if there is high uncertainty in decision-making, climate, and interactions with the recipient ecological community. To quantify the benefit to persistence and risk of establishment failure of AM under different management scenarios (e.g., choosing target species, proportion of population to relocate, and optimal location to relocate), we built a stochastic metacommunity model to simulate several species reproducing, dispersing, and competing on a temperature gradient as temperature increases over time. Without AM, the species were vulnerable to climate change when they had low population sizes, short dispersal, and strong poleward competition. When relocating species that exemplified these traits, AM increased the long-term persistence of the species most when relocating a fraction of the donor population, even if the remaining population was very small or rapidly declining. This suggests that leaving behind a fraction of the population could be a robust approach, allowing managers to repeat AM in case they move the species to the wrong place and at the wrong time, especially when it is difficult to identify a species’ optimal climate. We found that AM most benefitted species with low dispersal ability and least benefited species with narrow thermal tolerances, for which AM increased extinction risk on average. Although relocation did not affect the persistence of nontarget species in our simple competitive model, researchers will need to consider a more complete set of community interactions to comprehensively understand invasion potential.  相似文献   
174.
The herbicide propanil, a synthetic anilide, was discovered in 1957 to control grasses and broad-leaf weeds in rice fields. It has been found to disrupt the electron transport chain by inhibiting the photosystem II, thus impacting plant growth. In the environment, photolysis represents a major degradation pathway, whereas volatilization is not a major route of dissipation from either water or moist soils. Propanil is rapidly degraded by microbes into the major degradation product 3,4-dichloroaniline. This degradation product has been highly detected in both groundwater and surface waters throughout the world. Propanil has been found to adversely impact many non-target organisms. It is toxic to some early life-stage aquatic organisms, in addition to being moderately toxic to the water flea (Ceriodaphnia dubia) and rainbow trout. In addition, it has been reported to pose a high acute and long-term risk to birds. In plants, growth rates are highly impacted; however, some plant species are becoming resistant to propanil.  相似文献   
175.
176.
This paper is concerned with the prediction of mass and momentum transport in turbulent wall jets developing over smooth and transitionally rough plane walls. The ability to accurately predict the resulting wall shear stresses and vertical profiles of the Reynolds stresses in these flows is prerequisite to the accurate prediction of bed scour, sediment re-suspension and transport by turbulent diffusion. The computations were performed by solving the Reynolds-averaged forms of the equations describing conservation of mass, momentum and concentration. The unknown correlations that arise from the averaging process (the Reynolds stresses in the case of the momentum equation, and the turbulent mass fluxes in the case of concentration) were obtained from the solution of modeled differential equations that describe their conservation. Since these models are somewhat more complex than those typically used in practice, their benefits are demonstrated by comparisons with results obtained from simpler, eddy-viscosity based closures. Comparisons with experimental data show that results of acceptable accuracy can be obtained only by using the appropriate combination of models for the turbulent fluxes of mass and momentum that properly account for the reduction of the Reynolds stresses due to wall damping effects, and for the modification of the mass transfer rates due to interactions with the mean rates of strain.  相似文献   
177.
Not as much abatement as has been presumed. Smog check programs aim to curb tailpipe emissions from in-use vehicles by requiring repairs whenever emissions, measured at regular time intervals, exceed a certain threshold. Using data from California, we estimate that on average 41% of the initial emissions abatement from repairs is lost by the time of the subsequent inspection, normally two years later. Our estimates imply that the cost per pound of pollution avoided is an order of magnitude greater for smog check repairs than alternative policies such as new-vehicle standards or emissions trading among industrial point sources.  相似文献   
178.
The performance of two reaction rate models based on the laminar flamelet concept have been examined by calculating the behaviour of turbulent flame deflagration inside a semi-confined explosion tube. The models formulate the mean rate of reaction as a function of a transport equation for the flamelet surface density. The difference in the models is in modelling the source/sink terms of the flamelet surface density transport equation. The models are validated using laser diagnostics of flame deflagration in methane–air flammable mixture. The predictions are compared with experimental results for propagation, pressure history and flame speed. Sensitivity to cross-flow effects are investigated through comparison between two- and three-dimensional calculations. The numerically simulated results show that experimental trends are well reproduced by both models.  相似文献   
179.
In noisy conditions, several avian species modulate their songs in amplitude and in the temporal or frequency domains, presumably to improve communication. Most studies on how passerine birds perform such adjustments have been carried out in oscines, a group well known for the importance of learning in the development of their songs. On the other hand, suboscines, in which learning appears to have little influence on the development of their songs, have been largely neglected. We evaluated song adjustment to noise in the vermilion flycatcher (Pyrocephalus rubinus), a suboscine bird. We conducted song recordings and noise measurements at several territories within Mexico City during the length of the dawn chorus. Males living in noisier places sang long songs, while those males inhabiting quieter places sang both short and long songs. We also found evidence of individual song plasticity, as males sang less versatile songs (i.e., songs with more introductory elements) later in the morning when noise levels were higher. This individual shift in song seems to be more associated to time of the day rather than to the observed rise in noise. However, we cannot discard an effect of noise, which should be evaluated with an experiment. We discuss our results in the context of other studies with oscine passerines and other taxa and consider implications for signaling in intra- and intersexual contexts.  相似文献   
180.
Honey bee workers exhibit an age-based division of labor (temporal polyethism, DOL). Younger bees transition through sets of tasks within the nest; older bees forage outside. Components of temporal polyethism remain unrevealed. Here, we investigate the timing and pattern of pre-foraging behavior in distinct strains of bees to (1) determine if a general pattern of temporal DOL exists in honey bees, (2) to demonstrate a direct genetic impact on temporal pacing, and (3) to further elucidate the mechanisms controlling foraging initiation. Honey bees selected for differences in stored pollen demonstrate consistent differences in foraging initiation age. Those selected for increased pollen storage (high pollen hoarding strain, HSBs) initiate foraging earlier in life than those selected for decreased pollen storage (low pollen hoarding strain, LSBs). We found that HSBs both initiate and terminate individual pre-foraging tasks earlier than LSBs when housed in a common hive environment. Unselected commercial bees (wild type) generally demonstrated intermediate behavioral timing. There were few differences between genotypes for the proportion of pre-foraging effort dedicated to individual tasks, though total pre-foraging effort differences differed dramatically. This demonstrates that behavioral pacing can be accelerated or slowed, but the pattern of behavior is not fundamentally altered, suggesting a general pattern of temporal behavior in honey bees. This also demonstrates direct genetic control of temporal pacing. Finally, our results suggest that earlier HSB protein (pollen) consumption termination compared to LSBs may contribute to an earlier decline in hemolymph vitellogenin protein titers, which would explain their earlier onset of foraging.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号