全文获取类型
收费全文 | 15549篇 |
免费 | 158篇 |
国内免费 | 126篇 |
专业分类
安全科学 | 374篇 |
废物处理 | 666篇 |
环保管理 | 1794篇 |
综合类 | 2540篇 |
基础理论 | 4309篇 |
环境理论 | 4篇 |
污染及防治 | 4035篇 |
评价与监测 | 1056篇 |
社会与环境 | 963篇 |
灾害及防治 | 92篇 |
出版年
2022年 | 127篇 |
2021年 | 104篇 |
2020年 | 100篇 |
2019年 | 106篇 |
2018年 | 195篇 |
2017年 | 234篇 |
2016年 | 326篇 |
2015年 | 266篇 |
2014年 | 455篇 |
2013年 | 1207篇 |
2012年 | 491篇 |
2011年 | 691篇 |
2010年 | 613篇 |
2009年 | 582篇 |
2008年 | 671篇 |
2007年 | 713篇 |
2006年 | 589篇 |
2005年 | 513篇 |
2004年 | 521篇 |
2003年 | 507篇 |
2002年 | 489篇 |
2001年 | 647篇 |
2000年 | 475篇 |
1999年 | 254篇 |
1998年 | 173篇 |
1997年 | 206篇 |
1996年 | 205篇 |
1995年 | 236篇 |
1994年 | 235篇 |
1993年 | 180篇 |
1992年 | 195篇 |
1991年 | 183篇 |
1990年 | 203篇 |
1989年 | 187篇 |
1988年 | 151篇 |
1987年 | 162篇 |
1986年 | 153篇 |
1985年 | 156篇 |
1984年 | 148篇 |
1983年 | 140篇 |
1982年 | 125篇 |
1981年 | 120篇 |
1980年 | 115篇 |
1979年 | 124篇 |
1978年 | 100篇 |
1977年 | 113篇 |
1975年 | 87篇 |
1974年 | 87篇 |
1973年 | 96篇 |
1972年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
681.
Silvestre García de Jalón Ana Iglesias Ruth Cunningham Juan I. Pérez Díaz 《Regional Environmental Change》2014,14(3):1229-1242
Agricultural water management needs to evolve in view of increased water scarcity, especially when farming and natural protected areas are closely linked. In the study site of Doñana (southern Spain), water is shared by rice producers and a world heritage biodiversity ecosystem. Our aim is to contribute to defining adaptation strategies that may build resilience to increasing water scarcity and minimize water conflicts among agricultural and natural systems. The analytical framework links a participatory process with quantitative methods to prioritize the adaptation options. Bottom-up proposed adaptation measures are evaluated by a multi-criteria analysis (MCA) that includes both socioeconomic criteria and criteria of the ecosystem services affected by the adaptation options. Criteria weights are estimated by three different methods—analytic hierarchy process, Likert scale and equal weights—that are then compared. Finally, scores from an MCA are input into an optimization model used to determine the optimal land-use distribution in order to maximize utility and land-use diversification according to different scenarios of funds and water availability. While our results show a spectrum of perceptions of priorities among stakeholders, there is one overriding theme that is to define a way to restore part of the rice fields to natural wetlands. These results hold true under the current climate scenario and even more so under an increased water scarcity scenario. 相似文献
682.
V.S. Yaliwal P.G. Tewari S.Y. Adaganti 《International Journal of Sustainable Engineering》2014,7(3):269-282
Renewable and alternative fuels have numerous advantages compared with fossil fuels as they are renewable and biodegradable and provide food and energy security and foreign exchange savings besides addressing environmental concerns and socio-economic issues (Yaliwal et al. 2013. International Journal of Sustainable Engineering, doi:10.1080/19397038.2013.801530. Zhu et al. 2011a, Applied Thermal Engineering 31 (14–15): 2271–2278; Zhu et al. 2011b, Fuel 90: 1743-1750; Banapurmath, Tewari, and Hosmath 2008, Renewable Energy 33: 2007-2018; Banapurmath 2009, “Performance, Combustion and Emission Characteristics of a Single Cylinder Direct Injection CI Engine Operated on Dual Fuel Mode Using Honge Oil and Producer Gas.” PhD thesis, 1–195; Banapurmath et al. 2011, Waste and Biomass Valorization 2: 1–11). In this context, the main objective of the present work is to study methods of biofuel production such as Honge oil methyl ester (HOME) using a conventional transesterification process and bioethanol from the Calliandra calothyrsus shrub using a new pretreatment method known as hydrothermal explosion. Further, experimental investigations were carried out on a single-cylinder, four-stroke, direct-injection stationary diesel engine operating in a dual-fuel mode using HOME, bioethanol and producer gas combinations to determine its performance, combustion and emission characteristics. The performance of the dual-fuel engine was analyzed at optimized engine conditions. HOME-Bioethanol (BE) blends such as HOME+ 5% bioethanol (BE5), HOME+ 10% bioethanol (BE10) and HOME+ 15% bioethanol (BE15) were prepared by adding bioethanol to HOME (on volume basis) in different proportions ranging from 5 to 15% with an increment of 5%. In this present work, the effect of different BE blends on the performance of producer gas fuelled dual fuel engine was studied. Experimental investigation on dual fuel engine using BE5-Producer gas operation resulted in up to 4–9% increased brake thermal efficiency with decreased hydrocarbon (HC), carbon monoxide (CO) and marginally increased nitric oxide (NOx) emission levels compared to HOME-Producer gas, BE10-producer gas and BE15-producer gas mode of operation. However, it was observed that, the overall performance of BE-producer gas operation was found to be lower compared to diesel-producer gas operation. 相似文献
683.
N.R. Banapurmath W.M. Budzianowski Y.H. Basavarajappa R.S. Hosmath V.S. Yaliwal P.G. Tewari 《International Journal of Sustainable Engineering》2014,7(1):55-70
The diminishing resources and continuously increasing cost of petroleum in association with their alarming pollution levels from diesel engines has led to an interest in finding alternative fuels to diesel. Emission control and engine efficiency are two of the most important parameters in current engine design. The impending introduction of emission standards such as Euro IV and Euro V has forced research towards developing new technologies for combating engine emissions. This paper examines the effects of compression ratio, swirl augmentation techniques and ethanol addition on the combustion of compressed natural gas (CNG) blended with Honge oil methyl esters (HOME) in a dual fuel engine. The present results show that the combustion of HOME and 15% ethanol blend with CNG induction in a dual-fuel engine operated in optimized parameters at an injection timing of 27° Before Top Dead Centre and a compression ratio of 17.5 resulted in acceptable combustion emissions and improved brake thermal efficiencies. The implementation of swirl augmentation techniques increased brake thermal efficiencies (BTEs) and considerably reduced combustion emissions such as smoke, HC, CO and NOx. The addition of ethanol also increased BTEs. However, at more than 15% of ethanol in HOME, NOx emissions increased dramatically. 相似文献
684.
685.
686.
M. A. Potapov I. V. Zadubrovskaya P. A. Zadubrovskii O. F. Potapova V. I. Evsikov 《Russian Journal of Ecology》2012,43(1):40-44
A comparative analysis of reproductive behavior has been performed in the steppe lemming (Lagurus lagurus) and narrow-skulled vole (Microtus gregalis). The results show that the species are similar in certain behavioral features indicative of the stability of mating pairs.
However, in the narrow-skulled vole, unlike in the steppe lemming, mature males in olfactory tests show preference for receptive
sibling females versus non-kin females. Probably, it is the absence of the incest taboo that allows the involvement of young
of the year in reproduction within growing family groups and accounts for “coloniality” of the species. 相似文献
687.
The food supply to a large metropolis such as Paris involves huge fluxes of goods, which considerably impact the surrounding rural territories. Here, we present an attempt to localise Paris food supply areas, over a period of two centuries (1786, 1886, 2006), based on the analysis of data from transportation and production statistics for cereals, animal products, and fruits and vegetables, all three categories being expressed in terms of their nitrogen (i.e. protein) content. The results show contrasting trends for the three types of agricultural products. As for cereals, the Paris supply area remained for the most part restricted to the central area of the Paris basin, a region which gradually became specialised in intensive cereal production. Conversely, as animal farming had been progressively excluded from this area, regions located west and north of Paris (Brittany, Normandy, Nord-Pas-de-Calais) gradually dominated the supply of animal products to the metropolis. In addition, imported feed from South America today contributes as much as one-third of the total ration of feed in the livestock raised in these regions. For fruits and vegetables, about one-half of the Paris supply currently comes from long-distance imports, the other half coming from areas less than 200 km from Paris. As a whole, the Paris food supply area, although it has obviously enlarged in recent periods, is still anchored to an unexpected extent (about 50%) in its traditional nearby hinterland roughly coinciding with the Seine watershed, and in the regions specialised in animal farming located west and north. On the other hand, the agricultural system of the main food supply areas has considerably opened to global markets. 相似文献
688.
The results are presented that have been obtained during long-term studies (1991–2009) on the efficiency of natural reproduction
of the beluga, Russian sturgeon, stellate sturgeon, and sterlet in different spawning zones of the Volga. The influence of
major environmental factors on the formation of the offspring of these fishes is analyzed. It is shown that the productivity
of Volga spawning grounds varies depending on the river flow volume during spring floods and the abundance of active spawners.
Practical recommendations are proposed for enhancing sturgeon reproduction in the Volga. 相似文献
689.
Zhu Ting Ganesh P. Shivakoti Chen Haiyun David Maddox 《Environment, Development and Sustainability》2012,14(2):197-220
Community-based co-management (CBCM) mechanisms for forest management have matured through the development of new economic
analysis and common property theory. However, while many local CBCM mechanisms have been initiated in Chinese Natural Reserves,
there are few objective, data-based evaluations of whether these mechanisms improve forest conservation and local livelihoods.
This research uses Baishuijiang National Natural Reserve (BNNR) as a study case to evaluate China’s current CBCM mechanisms.
The evaluation is based mainly on three criteria: efficiency, equality and sustainability of project operation. Survey data
indicate that local CBCM mechanisms provide a wide-participation platform for local villagers, associated administration managers,
research institutions and NGOs to join in forest resource protection work while improving local livelihood. CBCM projects
have also facilitated a reduction in forest resource dependency, the improvement of household income and encouragement of
local people to participate in forest resource protection. Our analysis suggests that most CBCM organizations have made progress
in efficiency, equity and sustainability. However, further study should focus on how to deal with the lingering problems of
inequity in responsibility and rights among CBCM committee members, poor distribution of benefits, insufficient program-design
and management expertise, faulty information dissemination, and insufficient capital investment. 相似文献
690.
Novel catalytic nano-sized materials based on LaCoO(x) perovskite nanoparticles incapsulated in the mesoporous matrix of zirconia were prepared, characterized by physicochemical methods and tested in complete methanol oxidation. LaCoO(x) nanoparticles were prepared inside the mesopores of ZrO(2) by decomposition of bimetallic La-Co glycine precursor complexes. The catalysts have been studied by diffuse-reflectance FTIR-spectroscopy using such probe molecules as CO, CD(3)CN and CDCl(3) to test low-coordinated metal ions. At low temperatures of decomposition of complexes (up to 400°C), low-coordinated Co(3+) ions predominate in the LaCoO(x) nanoparticles, whereas basically Co(2+) ions are found upon increasing the decomposition temperature to 600°C. The novel nano-sized perovskite catalysts exhibit a very high catalytic activity in the abatement of volatile organic compounds present in air, like methanol and light hydrocarbons. 相似文献