全文获取类型
收费全文 | 2078篇 |
免费 | 34篇 |
国内免费 | 15篇 |
专业分类
安全科学 | 69篇 |
废物处理 | 74篇 |
环保管理 | 378篇 |
综合类 | 336篇 |
基础理论 | 483篇 |
环境理论 | 4篇 |
污染及防治 | 529篇 |
评价与监测 | 151篇 |
社会与环境 | 91篇 |
灾害及防治 | 12篇 |
出版年
2023年 | 22篇 |
2022年 | 23篇 |
2021年 | 28篇 |
2020年 | 25篇 |
2019年 | 30篇 |
2018年 | 41篇 |
2017年 | 55篇 |
2016年 | 50篇 |
2015年 | 53篇 |
2014年 | 56篇 |
2013年 | 155篇 |
2012年 | 80篇 |
2011年 | 122篇 |
2010年 | 85篇 |
2009年 | 99篇 |
2008年 | 109篇 |
2007年 | 131篇 |
2006年 | 94篇 |
2005年 | 81篇 |
2004年 | 81篇 |
2003年 | 77篇 |
2002年 | 83篇 |
2001年 | 42篇 |
2000年 | 34篇 |
1999年 | 28篇 |
1998年 | 28篇 |
1997年 | 27篇 |
1996年 | 22篇 |
1995年 | 27篇 |
1994年 | 26篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 18篇 |
1985年 | 9篇 |
1984年 | 11篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 8篇 |
1979年 | 14篇 |
1978年 | 8篇 |
1977年 | 9篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1954年 | 8篇 |
排序方式: 共有2127条查询结果,搜索用时 93 毫秒
991.
992.
Soil Water Sample Collector 总被引:1,自引:0,他引:1
993.
An important policy question receiving considerable attention concerns the risk perception–risk mitigation process that guides how individuals choose to address natural hazard risks. This question is considered in the context of wildfire. We analyze the factors that influence risk reduction behaviors by homeowners living in the wildland–urban interface. The factors considered are direct experience, knowledge of wildfire risk, locus of responsibility, fulltime/seasonal status, and self-efficacy. Survey data from three homeowner associations in the western U.S. are used to estimate the direct and indirect effects of this relationship. Our results indicate that the effects of knowledge and locus of responsibility are mediated by homeowners' risk perceptions. We also find that beliefs of self-efficacy and fulltime/seasonal status have a direct influence on risk reduction behaviors. Finally, we find, surprisingly, that direct experience with wildfire does not directly influence the risk perception–risk mitigation process. 相似文献
994.
Jeroen P. H. M. van den Wijngaard Asli Umur Michael G. Ross Martin J. C. van Gemert 《黑龙江环境通报》2008,28(4):280-291
Twin–twin transfusion syndrome (TTTS) represents a pregnancy complication with a high risk for perinatal mortality and postnatal morbidity. Mathematical models have been utilized to examine the mechanisms of disease and potential treatment modalities. We developed four consecutive models based on pathophysiology mechanisms. Conceptually, these models remained simple, but with increased complexity in details. We present our models tutorially with the necessary equations expressed in words. The aetiology of TTTS was related to AV anastomoses from donor to recipient and their growth commensurate with placental growth. We assessed that natural growth of placenta and foetuses causes the diameter and length of the AV, as well as the AV's pressure gradient, to increase proportional to gestational age. The AV transfusion then increases faster than natural foetal growth. A progressively increasing discordance subsequently develops, not compensated for by foetal growth. A simulation is performed to show how this discordance in blood volumetric development causes successive discordances in other functions, particularly renal, circulatory, and cardio-vascular, resulting in disease progression to the various stages of TTTS. In conclusion, mathematical modelling of TTTS has provided an understanding of the sequence of events that leads to the various presentations of TTTS stages as well as the efficacy of therapies. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
995.
Exploring alternative states in ecological systems with a qualitative analysis of community feedback
Martin P. Marzloff Jeffrey M. Dambacher Stewart D. Frusher 《Ecological modelling》2011,222(15):2651-2662
Demonstrating and predicting the existence of alternative states in natural communities remains a challenge for ecologists and is essential for resource managers. Positive feedback is often presented as central in maintaining alternative ecosystem states, but no formal approach relates this part of theory to real world applications. Through qualitative modelling of community response to long-term perturbations, we define generic mechanistic links between positive feedback and the occurrence of alternative states. Positive feedback diminishes a system's overall resistance to change, and can create and maintain correlations in the relative abundance of variables that coincide with alternative states.Through specific models of the dynamics of Tasmanian rocky-reef communities, which are affected by climate and fishing and persist within alternative states, we demonstrate the ability of our theoretical framework to predict alternative states in ecosystems and inform management intervention. A qualitative knowledge of community structure permits a thorough analysis of system feedback and an assessment of the potential for an ecosystem to exhibit alternative states. We illustrate the usefulness of the approach to inform management priorities, and to focus monitoring and field research on the key drivers of ecosystem dynamics. 相似文献
996.
Michael M. Pollock Timothy J. Beechie Martin Liermann Richard E. Bigley 《Journal of the American Water Resources Association》2009,45(1):141-156
Abstract: We compared summer stream temperature patterns in 40 small forested watersheds in the Hoh and Clearwater basins in the western Olympic Peninsula, Washington, to examine correlations between previous riparian and basin‐wide timber harvest activity and stream temperatures. Seven watersheds were unharvested, while the remaining 33 had between 25% and 100% of the total basin harvested, mostly within the last 40 years. Mean daily maximum temperatures were significantly different between the harvested and unharvested basins, averaging 14.5°C and 12.1°C, respectively. Diurnal fluctuations between harvested and unharvested basins were also significantly different, averaging 1.7°C and 0.9°C, respectively. Total basin harvest was correlated with average daily maximum temperature (r2 = 0.39), as was total riparian harvest (r2 = 0.32). The amount of recently clear‐cut riparian forest (<20 year) within 600 m upstream of our monitoring sites ranged from 0% to 100% and was not correlated to increased stream temperatures. We used Akaike’s Information Criteria (AIC) analysis to assess whether other physical variables could explain some of the observed variation in stream temperature. We found that variables related to elevation, slope, aspect, and geology explain between 5% and 14% more of the variability relative to the variability explained by percent of basin harvested (BasHarv), and that the BasHarv was consistently a better predictor than the amount of riparian forest harvested. While the BasHarv is in all of the models that perform well, the AIC analysis shows that there are many models with two variables that perform about the same and therefore it would be difficult to choose one as the best model. We conclude that adding additional variables to the model does not change the basic findings that there is a relatively strong relationship between maximum daily stream temperatures and the total amount of harvest in a basin, and strong, but slightly weaker relationship between maximum daily stream temperatures and the total riparian harvest in a basin. Seventeen of the 40 streams exceeded the Washington State Department of Ecology’s (DOE) temperature criterion for waters defined as “core salmon and trout habitat” (class AA waters). The DOE temperature criterion for class AA waters is any seven‐day average of daily maximum temperatures in excess of 16°C. The probability of a stream exceeding the water quality standard increased with timber harvest activity. All unharvested sites and five of six sites that had 25‐50% harvest met DOEs water quality standard. In contrast, only nine of eighteen sites with 50‐75% harvest and two of nine sites with >75% harvest met DOEs water quality standard. Many streams with extensive canopy closure, as estimated by the age of riparian trees, still had higher temperatures and greater diurnal fluctuations than the unharvested basins. This suggests that the impact of past forest harvest activities on stream temperatures cannot be entirely mitigated through the reestablishment of riparian buffers. 相似文献
997.
L.P. Walker G.B. VanderGheynst 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1041-1050
ABSTRACT Oxygen (O2) sensors have been developed for in situ measurement of O2 in high-solids degradation processes. The O2 sensor has been shown to withstand the corrosive environment of the biodegradation process with high humidity and temperatures exceeding 60 oC. Calibration tests prior to and after in situ operation showed the sensor to perform accurately and reproducibly after 71 days of in situ operation. A linear relationship between O2-sensor output and water vapor pressure was confirmed through calibration experiments. To compensate for the effect of water vapor pressure on O2-sensor measurements, O2 concentration was expressed on a dry air basis using the confirmed linear relationship. In situ O2-sensor output expressed on a dry air basis was found to follow trends of gas samples analyzed by gas chromatography with good agreement. 相似文献
998.
Jukka M. Kurola Mona Arnold Merja H. Kontro Matti Talves Martin Romantschuk 《Waste management (New York, N.Y.)》2010,30(5):779-786
In the present study, we investigated the effects of two bulking materials, Sphagnum peat and pine wood chips, on the early stages of biowaste composting in two pilot-scale processes. Emphasis was placed on studying the formation conditions of malodorous compost gases in the initial phases of the processes. The results showed that gas emission leaving an open windrow and a closed drum composting system contained elevated concentrations of fermentative microbial metabolites when acid Sphagnum peat (pH 3.2) was used as a bulking material. Moreover, the gas emission of the peat amended drum composter contained a high concentration of odour (up to 450,000 ou m?3 of air). The highest odour values in the outlet gas of peat amended composts coincided with the elevated concentrations of volatile organic compounds such as acetoin and buthanedion. We conclude that the acidifying qualities of composting substrates or bulking material may intensify odour emission from biowaste composts and prolong the early stages of the composting process. 相似文献
999.
Laura Martin 《Conservation biology》2010,24(5):1172-1173
1000.
Wu Chuandong Yang Fan Brancher Marlon Liu Jiemin Qu Chen Piringer Martin Schauberger Günther 《Environmental science and pollution research international》2020,27(30):37684-37698
Environmental Science and Pollution Research - Airborne emissions from concentrated animal feeding operations (CAFOs) have the potential to pose a risk to human health and the environment. Here, we... 相似文献