全文获取类型
收费全文 | 97288篇 |
免费 | 1235篇 |
国内免费 | 1142篇 |
专业分类
安全科学 | 3896篇 |
废物处理 | 3539篇 |
环保管理 | 14861篇 |
综合类 | 21451篇 |
基础理论 | 27295篇 |
环境理论 | 74篇 |
污染及防治 | 17967篇 |
评价与监测 | 5811篇 |
社会与环境 | 4149篇 |
灾害及防治 | 622篇 |
出版年
2022年 | 823篇 |
2021年 | 816篇 |
2020年 | 663篇 |
2019年 | 883篇 |
2018年 | 1240篇 |
2017年 | 1284篇 |
2016年 | 2250篇 |
2015年 | 1859篇 |
2014年 | 2605篇 |
2013年 | 9316篇 |
2012年 | 2469篇 |
2011年 | 2978篇 |
2010年 | 3382篇 |
2009年 | 3542篇 |
2008年 | 2603篇 |
2007年 | 2512篇 |
2006年 | 2736篇 |
2005年 | 2627篇 |
2004年 | 2915篇 |
2003年 | 2778篇 |
2002年 | 2331篇 |
2001年 | 2804篇 |
2000年 | 2274篇 |
1999年 | 1627篇 |
1998年 | 1415篇 |
1997年 | 1416篇 |
1996年 | 1539篇 |
1995年 | 1641篇 |
1994年 | 1523篇 |
1993年 | 1371篇 |
1992年 | 1370篇 |
1991年 | 1328篇 |
1990年 | 1292篇 |
1989年 | 1263篇 |
1988年 | 1105篇 |
1987年 | 1016篇 |
1986年 | 1006篇 |
1985年 | 1084篇 |
1984年 | 1176篇 |
1983年 | 1187篇 |
1982年 | 1187篇 |
1981年 | 1107篇 |
1980年 | 957篇 |
1979年 | 946篇 |
1978年 | 835篇 |
1977年 | 732篇 |
1976年 | 663篇 |
1974年 | 646篇 |
1973年 | 664篇 |
1972年 | 680篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
Many studies on geological carbon dioxide (CO2) storage capacity neglect the influence of complex coupled processes which occur during and after the injection of CO2. Storage capacity is often overestimated since parts of the reservoirs cannot be reached by the CO2 plume due to gravity segregation and are thus not accessible for storage. This work investigates the effect of reservoir parameters like depth, temperature, absolute and relative permeability, and capillary pressure on the processes during CO2 injection and thus on estimates of effective storage capacity. The applied statistical characteristics of parameters are based on a large reservoir parameter database. Different measured relative permeability relations are considered. The methodology of estimating storage capacity is discussed. Using numerical 1D and 3D experiments, detailed time-dependent storage capacity estimates are derived. With respect to the concept developed in this work, it is possible to estimate effective CO2 storage capacity in saline aquifers. It is shown that effective CO2 mass stored in the reservoir varies by a factor of 20 for the reservoir setups considered. A high influence of the relative permeability relation on storage capacity is shown. 相似文献
972.
Mårten Bryngelsson Erik G. Lindfeldt Jan Heller 《International Journal of Greenhouse Gas Control》2009,3(3):255-262
This study investigates the possibility of capturing CO2 from flue gas under pressurised conditions, which could prove to be beneficial in comparison to working under atmospheric conditions. Simulations of two hybrid combined cycles with pressurised fluidised bed combustion and CO2 capture are presented. CO2 is captured from pressurised flue gas by means of chemical absorption after the boiler but before expansion. The results show a CO2 capture penalty of approximately 8 percentage points (including 90% CO2 capture rate and compression to 110 bar), which makes the efficiency for the best performing cycle 43.9%. It is 5.2 percentage points higher than the most probable alternative, i.e. using a natural gas fired combined cycle and a pulverised coal fired condensing plant separately with the same fuel split ratio. The largest part of the penalty is associated with the lower mass flow of flue gas after CO2 capture, which leads to a decrease in work output in the expander and potential for feed water heating. The penalty caused by the regeneration of absorbent is quite low, since the high pressure permits the use of potassium carbonate, which requires less regeneration heat than for example the more commonly proposed monoethanolamine. Although the efficiencies of the cycles look promising it will be important to perform a cost estimate to be able to make a fair comparison with other systems. Such a cost estimate has not been done in this study. A significant drawback of these hybrid cycles in that respect is the complex nature of the systems that will have a negative effect on the economy. 相似文献
973.
De-novo formation of dioxins and furans and the memory effect in waste incineration flue gases 总被引:1,自引:0,他引:1
The formation of dioxin (polychlorinated-rho-dibenzodioxins - PCDD) and furan (polychlorinated dibenzofurans - PCDF) in waste incineration flyash in relation to temperature has been investigated in a bench scale reactor. The PCDD/PCDF released into the exhaust gases of the reactor and trapped in a condensation and vapour phase adsorption system were also determined. The concentrations of PCDD/PCDF in the flyash were analysed in detail for all congeners and isomers including the mono-, di- and tri-PCDD/PCDF. De-novo synthesis of PCDD/PCDF was clearly seen in the flyash with large changes in concentrations of PCDD/PCDF with only small changes in temperature. Exhaust gas PCDD/PCDF were detected at all temperatures, with the maximum emission occurring at a flyash temperature of 350 degrees C, where the equivalent of over 42 times the total dioxin/furan concentration of the original flyash was lost to the vapour phase per unit mass of initial flyash. Although the desorbed species were mainly the lower mono- to tri-congener group of dioxins and furans, the desorbed dioxin/furans had a considerable toxic equivalent value. 相似文献
974.
Castrillón L Fernández-Nava Y Marañón E García L Berrueta J 《Waste management (New York, N.Y.)》2009,29(2):761-766
Cattle manure from a dairy farm was treated in order to reduce its pollution potential. The manure came from a farm with 120 cows kept in stables in a free stall barn. As pretreatment, the manure is usually filtered on the farm using a screw press separator with a 0.5 mm mesh. Approximately 70% of the total filtered volume passes through the screen, thus constituting the liquid fraction. This fraction, with a composition of around 64,500 mg COD/l, 5770 mg total-N/l and 800 mg total-P/l, was subjected to centrifugation followed by a two-step biological treatment (anoxic-aerobic) to reduce organic matter (COD), nitrogen and phosphorus compounds. Centrifugation led to the following removal efficiencies: 35% total solids, 60% COD, 75% total phosphorus and 20% total nitrogen (mainly organic nitrogen). With the subsequent anoxic-aerobic treatment, average removal efficiencies of 85% for COD, 90% for total phosphorus and 75% for total nitrogen were achieved. 相似文献
975.
The effects of aeration rate on generated compost quality, using aerated static pile method 总被引:2,自引:0,他引:2
To determine the most appropriate composting process in an active municipal solid waste system, an experiment was carried out using a nested design method with three aeration rates. During each aeration rate, parameters such as temperature, pH, EC, carbon-to-nitrogen ratio, NO(3)-N, nitrogen, potassium and phosphorous were measured and the efficiency of different composting processes was evaluated. The result of this study showed that the lower and medium aeration rates had a significant impact on nitrogen, carbon-to-nitrogen ratio and temperature profile, while higher aeration rates led to higher EC values. Furthermore, the thermophilic phase lasted 13, 9 and 4 weeks for the aeration rates of 0.4, 0.6 and 0.9 L min(-1)kg(-1), respectively. Accordingly, it was concluded that starting at a rate of 0.6 L min(-1)kg(-1) during first 2 months (about 9 weeks) of the process and continuing at a rate of 0.4 L min(-1)kg(-1)until the end of composting process would result in lower energy consumption. 相似文献
976.
Niwagaba C Nalubega M Vinnerås B Sundberg C Jönsson H 《Waste management (New York, N.Y.)》2009,29(2):585-589
In urine-diverting toilets, urine and faeces are collected separately so that nutrient content can be recycled unmixed. Faeces should be sanitized before use in agriculture fields due to the presence of possible enteric pathogens. Composting of human faeces with food waste was evaluated as a possible method for this treatment. Temperatures were monitored in three 78-L wooden compost reactors fed with faeces-to-food waste substrates (F:FW) in wet weight ratios of 1:0, 3:1 and 1:1, which were observed for approximately 20 days. To achieve temperatures higher than 15 degrees C above ambient, insulation was required for the reactors. Use of 25-mm thick styrofoam insulation around the entire exterior of the compost reactors and turning of the compost twice a week resulted in sanitizing temperatures (>or=50 degrees C) to be maintained for 8 days in the F:FW=1:1 compost and for 4 days in the F:FW=3:1 compost. In these composts, a reduction of >3 log(10) for E. coli and >4 log(10) for Enterococcus spp. was achieved. The F:FW=1:0 compost, which did not maintain >or=50 degrees C for a sufficiently long period, was not sanitized, as the counts of E. coli and Enterococcus spp. increased between days 11 and 15. This research provides useful information on the design and operation of family-size compost units for the treatment of source-separated faeces and starchy food residues, most likely available amongst the less affluent rural/urban society in Uganda. 相似文献
977.
Aging and compressibility of municipal solid wastes 总被引:2,自引:0,他引:2
The expansion of a municipal solid waste (MSW) landfill requires the ability to predict settlement behavior of the existing landfill. The practice of using a single compressibility value when performing a settlement analysis may lead to inaccurate predictions. This paper gives consideration to changes in the mechanical compressibility of MSW as a function of the fill age of MSW as well as the embedding depth of MSW. Borehole samples representative of various fill ages were obtained from five boreholes drilled to the bottom of the Qizhishan landfill in Suzhou, China. Thirty-one borehole samples were used to perform confined compression tests. Waste composition and volume-mass properties (i.e., unit weight, void ratio, and water content) were measured on all the samples. The test results showed that the compressible components of the MSW (i.e., organics, plastics, paper, wood and textiles) decreased with an increase in the fill age. The in situ void ratio of the MSW was shown to decrease with depth into the landfill. The compression index, Cc, was observed to decrease from 1.0 to 0.3 with depth into the landfill. Settlement analyses were performed on the existing landfill, demonstrating that the variation of MSW compressibility with fill age or depth should be taken into account in the settlement prediction. 相似文献
978.
979.
980.
Preferred modes of travel among older adults: What factors affect the choice to walk instead of drive? 总被引:1,自引:0,他引:1
Rebecca B. Naumann Author Vitae Ann M. Dellinger Author Vitae Author Vitae Amy E. Bonomi Author Vitae Author Vitae Robert S. Thompson Author Vitae 《Journal of Safety Research》2009,40(5):395-36