全文获取类型
收费全文 | 5494篇 |
免费 | 45篇 |
国内免费 | 25篇 |
专业分类
安全科学 | 113篇 |
废物处理 | 257篇 |
环保管理 | 380篇 |
综合类 | 941篇 |
基础理论 | 1352篇 |
环境理论 | 5篇 |
污染及防治 | 1773篇 |
评价与监测 | 423篇 |
社会与环境 | 302篇 |
灾害及防治 | 18篇 |
出版年
2023年 | 57篇 |
2022年 | 132篇 |
2021年 | 150篇 |
2020年 | 75篇 |
2019年 | 83篇 |
2018年 | 195篇 |
2017年 | 214篇 |
2016年 | 279篇 |
2015年 | 192篇 |
2014年 | 284篇 |
2013年 | 425篇 |
2012年 | 311篇 |
2011年 | 351篇 |
2010年 | 241篇 |
2009年 | 194篇 |
2008年 | 332篇 |
2007年 | 297篇 |
2006年 | 250篇 |
2005年 | 197篇 |
2004年 | 181篇 |
2003年 | 153篇 |
2002年 | 130篇 |
2001年 | 80篇 |
2000年 | 44篇 |
1999年 | 53篇 |
1998年 | 27篇 |
1997年 | 25篇 |
1996年 | 24篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 12篇 |
1992年 | 21篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 10篇 |
1986年 | 25篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 19篇 |
1980年 | 13篇 |
1966年 | 16篇 |
1965年 | 11篇 |
1964年 | 10篇 |
1959年 | 11篇 |
1957年 | 14篇 |
1956年 | 12篇 |
1954年 | 10篇 |
排序方式: 共有5564条查询结果,搜索用时 890 毫秒
491.
Stefan Löfgren Mats Fröberg Jun Yu Jakob Nisell Bo Ranneby 《Environmental monitoring and assessment》2014,186(12):8907-8928
From a policy perspective, it is important to understand forestry effects on surface waters from a landscape perspective. The EU Water Framework Directive demands remedial actions if not achieving good ecological status. In Sweden, 44 % of the surface water bodies have moderate ecological status or worse. Many of these drain catchments with a mosaic of managed forests. It is important for the forestry sector and water authorities to be able to identify where, in the forested landscape, special precautions are necessary. The aim of this study was to quantify the relations between forestry parameters and headwater stream concentrations of nutrients, organic matter and acid-base chemistry. The results are put into the context of regional climate, sulphur and nitrogen deposition, as well as marine influences. Water chemistry was measured in 179 randomly selected headwater streams from two regions in southwest and central Sweden, corresponding to 10 % of the Swedish land area. Forest status was determined from satellite images and Swedish National Forest Inventory data using the probabilistic classifier method, which was used to model stream water chemistry with Bayesian model averaging. The results indicate that concentrations of e.g. nitrogen, phosphorus and organic matter are related to factors associated with forest production but that it is not forestry per se that causes the excess losses. Instead, factors simultaneously affecting forest production and stream water chemistry, such as climate, extensive soil pools and nitrogen deposition, are the most likely candidates The relationships with clear-felled and wetland areas are likely to be direct effects. 相似文献
492.
Loïc D’Orangeville Daniel Houle Benoît Côté Louis Duchesne 《Environmental monitoring and assessment》2014,186(12):8191-8202
The projected increase in atmospheric N deposition and air/soil temperature will likely affect soil nutrient dynamics in boreal ecosystems. The potential effects of these changes on soil ion fluxes were studied in a mature balsam fir stand (Abies balsamea [L.] Mill) in Quebec, Canada that was subjected to 3 years of experimentally increased soil temperature (+4 °C) and increased inorganic N concentration in artificial precipitation (three times the current N concentrations using NH4NO3). Soil element fluxes (NO3, NH4, PO4, K, Ca, Mg, SO4, Al, and Fe) in the organic and upper mineral horizons were monitored using buried ion-exchange membranes (PRS? probes). While N additions did not affect soil element fluxes, 3 years of soil warming increased the cumulative fluxes of K, Mg, and SO4 in the forest floor by 43, 44, and 79 %, respectively, and Mg, SO4, and Al in the mineral horizon by 29, 66, and 23 %, respectively. We attribute these changes to increased rates of soil organic matter decomposition. Significant interactions of the heating treatment with time were observed for most elements although no clear seasonal patterns emerged. The increase in soil K and Mg in heated plots resulted in a significant but small K increase in balsam fir foliage while no change was observed for Mg. A 6–15 % decrease in foliar Ca content with soil warming could be related to the increase in soil-available Al in heated plots, as Al can interfere with the root uptake of Ca. 相似文献
493.
R. Clément M. Descloitres T. Günther L. Oxarango C. Morra J.-P. Laurent J.-P. Gourc 《Waste management (New York, N.Y.)》2010,30(3):452-464
Leachate recirculation is a key process in the scope of operating municipal waste landfills as bioreactors, which aims to increase the moisture content to optimize the biodegradation in landfills. Given that liquid flows exhibit a complex behaviour in very heterogeneous porous media, in situ monitoring methods are required. Surface time-lapse electrical resistivity tomography (ERT) is usually proposed. Using numerical modelling with typical 2D and 3D injection plume patterns and 2D and 3D inversion codes, we show that wrong changes of resistivity can be calculated at depth if standard parameters are used for time-lapse ERT inversion. Major artefacts typically exhibit significant increases of resistivity (more than +30%) which can be misinterpreted as gas migration within the waste. In order to eliminate these artefacts, we tested an advanced time-lapse ERT procedure that includes (i) two advanced inversion tools and (ii) two alternative array geometries. The first advanced tool uses invariant regions in the model. The second advanced tool uses an inversion with a “minimum length” constraint. The alternative arrays focus on (i) a pole–dipole array (2D case), and (ii) a star array (3D case). The results show that these two advanced inversion tools and the two alternative arrays remove almost completely the artefacts within +/?5% both for 2D and 3D situations. As a field application, time-lapse ERT is applied using the star array during a 3D leachate injection in a non-hazardous municipal waste landfill. To evaluate the robustness of the two advanced tools, a synthetic model including both true decrease and increase of resistivity is built. The advanced time-lapse ERT procedure eliminates unwanted artefacts, while keeping a satisfactory image of true resistivity variations. This study demonstrates that significant and robust improvements can be obtained for time-lapse ERT monitoring of leachate recirculation in waste landfills. 相似文献
494.
Joakim Krook Annica Carlsson Mats Eklund Per Frändegård Niclas Svensson 《Journal of Cleaner Production》2011,19(9-10):1052-1056
Large technical systems serving the everyday needs of people, such as water supply systems, power grids or communication networks, are rich in accumulated metals. Over time, parts of these systems have been taken out of use without the system infrastructure being removed from its original location. Such metal stocks in hibernation thus constitute potential resource reservoirs accessible for recovery. In this paper, obsolete stocks of copper situated in the local power grids of two Swedish cities are quantified. Emphasis is also on economic conditions for extracting such “hibernating” cables. The results show that on a per customer basis, the two power grids contain similar amounts of copper, i.e. 0.04–0.05 tonnes per subscriber. However, the share of the copper stock that is in hibernation differs between the grids. In the larger grid of Gothenburg, almost 20% of the copper accumulated in the grid is no longer in use, while the obsolete share does not exceed 5% in the city of Linköping. For managers of local power grids, recovery of hibernating cables could be beneficial if integrated with other maintenance work on the grid. At the present price of copper, however, separate recovery of obsolete cables is not economically justified. 相似文献
495.
This work established background concentrations for the pseudo total (HNO3 + H2O2-soluble), mobilisable (NH4-acetate + EDTA-soluble) and mobile (1?M NH4NO3-soluble) element fractions of Hungarian surface soils that can be used as reference values for the soil quality standards. The 193 soils investigated were taken from the Hungarian Soil Information and Monitoring System. The background values for Al, As, B, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr and Zn were given as a range covering 95% of the variance of the representative samples. The differences between observed element concentrations and the calculated background values indicated anthropogenic or pedogenic impact in each fraction. The comparison of the calculated background values with the Hungarian quality standards and the contamination limit values of other countries showed that the limit values of a certain region or country are not suitable for other areas. Generally, Mn and Al had the highest, while Cd had the lowest concentration in each fraction. Cr and Al were the least and Sr was the most mobile element. The principal component analysis indicated different geochemical and physico-chemical behaviour of the elements in the fractions; the pseudo total fraction was influenced more by the geological behaviour, while mobilisable and mobile fraction explained a much higher proportion of the total variance of soil physico-chemical properties than soil geochemical properties. The Cd–Ni and Co–Mn element pairs were always in the same principal component in each fractions indicating similar geogenic origin and showing that their solubility changes are similar in function of soil properties. 相似文献
496.
497.
Nabil Tlili Georges Grévillot Cécile Vallières 《International Journal of Greenhouse Gas Control》2009,3(5):519-527
Experimental work is performed with a 5A zeolite on a small laboratory column with heating from the wall. Carbon dioxide adsorption occurs at atmospheric pressure and different CO2 concentrations in nitrogen. Comparisons of different methods of desorption by heating, purge and/or vacuum are studied. Desorption by heating only leads to almost pure CO2 (around 99% purity) and a recovery nearly linear to the heating temperature, ranging from 45% at 130 °C to 79% at 210 °C. Recovery can be subsequently increased with a nitrogen purge to more than 98% but the recovered carbon dioxide is diluted due to the dispersive character of the desorption wave and the operation time is long. Increasing the flow rate decreases the desorption time but has no effect on the purity because the total purge volume remains about the same. Substitution of the purge step with a vacuum step leads to pure CO2 and almost total recovery. Desorption under vacuum only without heating leads to pure CO2 (around 99% purity) but limited recovery (85% in the present work).Desorption under vacuum seems to be more simple for large-scale applications. When using a water liquid ring pump, the temperature of the ring must be kept as low as possible to provide a high operating capacity. 相似文献
498.
Bruno Nunes Fátima Brandão Tânia Sérgio Sara Rodrigues Fernando Gonçalves Alberto Teodorico Correia 《Environmental science and pollution research international》2014,21(12):7501-7511
Flatfish species, such as the turbot (Scophthalmus maximus), are common targets for toxic effects, since they are exposed through the food chain (ingestion of contaminated preys) and are in direct contact with the waterborne contaminant and sediments. Furthermore, these fish species live in close proximity to interstitial water that frequently dissolves high amounts of contaminants, including metals. Despite this significant set of characteristics, the present knowledge concerning flatfish contamination and toxicity by metals is still scarce. To attain the objective of assessing the effects of metals on a flatfish species, S. maximus specimens were chronically exposed to lead, copper and zinc, at ecologically relevant concentrations, and biochemical (oxidative stress: catalase and glutathione S-transferases activities, and lipid peroxidation; neurotoxicity: cholinesterase activity) parameters were assessed on selected tissues (gills and liver). Copper had no significant effects on all tested parameters; lead was causative of significant increases in liver GSTs activities and also in lipoperoxidation of gill tissue; exposure to zinc caused a significant increase in catalase activity of gill tissue. None of the tested metals elicited noteworthy effects in terms of neurotoxicity. The obtained results showed that only the metal lead is of some environmental importance, since it was able to cause deleterious modifications of oxidative nature at relevant concentrations. 相似文献
499.
Sebastian Weissenberger Marc Lucotte Stéphane Houel Nicolas Soumis Éric Duchemin René Canuel 《Ecological modelling》2010,221(4):610-620
A mechanistic semi-empirical carbon cycle model of the La Grande reservoir complex in northern Quebec, Canada was conceived in order to investigate the climate impact of such a large alteration of the continental water cycle. The model includes inputs from the drainage basin, organic matter release from flooded soils, CO2 emissions across the water-atmosphere interface and sedimentation. Most input data stems from previous research by our group on those ecosystems. The model includes the seven reservoirs of the La Grande complex and was run for periods of 50 and 100 years. Terrigeneous dissolved, particulate and suspended soil carbon fluxes and concentrations were computed. Over 100 years, 31.3 × 1012 g C are released from flooded soils, equivalent to 28-29% of inputs from the drainage basin. 40-74% of dissolved organic carbon is mineralized. CO2 fluxes over 100 years are 50.5-79.8 × 1012 g C, 46.4-67.9 × 1012 g C more than in the absence of reservoirs. The increase in mineralization of organic matter and in CO2 emissions is a result of the increase in cumulated water residence time due to the creation of the reservoirs. Changes in other carbon sinks and sources likely offset a part of this additional carbon flux to the atmosphere. In the first years following flooding of the reservoir, organic carbon release from flooded soils exceeds CO2 emissions, implying the downstream export of large quantities of eroded soil organic carbon. After this initial period, CO2 emissions are fuelled by organic carbon originating from the drainage basin. 相似文献
500.
Ali Jamshidparvar Faramin Javandel Alireza Seidavi Francisco Peña Blanco Andrés L. Martínez Marín Carmen Avilés Ramírez Estrella Agüera Buendía Nieves Núñez-Sánchez 《Environmental science and pollution research international》2017,24(30):23571-23577
Increasing levels of Heracleum persicum (golpar) in drinking water were studied in broilers. Two hundred and forty-one-day-old male chickens were allocated to one of six treatments: control, without added phytogenics nor probiotics in drinking water, and probiotics at recommended manufacturer’s level (P) or 1.0, 1.5, 2.0, and 2.5 ml/l of golpar extract solution (G1, G1.5, G2, and G2.5 treatments, respectively) in drinking water. As a result of this study, no linear or quadratic trends in the feed intake (FI) and feed conversion rate (FCR) due to golpar supplementation were found. Body weight gain, final body weight, and relative carcass weight showed a positive linear response with increasing levels of golpar supplementation. Neither golpar nor probiotics had effects on the percentages of edible parts of the carcass. Golpar supplementation levels caused a linear negative response of the albumin content in blood plasma, whereas both abdominal fat as percentage of carcass weight and uric acid levels in blood plasma linearly increased. The effects on Ig responses were only observed at 42 days of age and were similar in probiotics and the highest level of golpar supplementation. Based on our results, both probiotics and golpar supplementation could improve broiler performance and immune function. 相似文献