全文获取类型
收费全文 | 84061篇 |
免费 | 1215篇 |
国内免费 | 1058篇 |
专业分类
安全科学 | 3626篇 |
废物处理 | 2982篇 |
环保管理 | 13135篇 |
综合类 | 20844篇 |
基础理论 | 25404篇 |
环境理论 | 71篇 |
污染及防治 | 11648篇 |
评价与监测 | 5036篇 |
社会与环境 | 3112篇 |
灾害及防治 | 476篇 |
出版年
2022年 | 773篇 |
2021年 | 774篇 |
2020年 | 635篇 |
2019年 | 849篇 |
2018年 | 1027篇 |
2017年 | 1056篇 |
2016年 | 2071篇 |
2015年 | 1809篇 |
2014年 | 2554篇 |
2013年 | 9201篇 |
2012年 | 1903篇 |
2011年 | 1928篇 |
2010年 | 3119篇 |
2009年 | 3244篇 |
2008年 | 1422篇 |
2007年 | 1215篇 |
2006年 | 1802篇 |
2005年 | 1896篇 |
2004年 | 2222篇 |
2003年 | 2038篇 |
2002年 | 1604篇 |
2001年 | 1781篇 |
2000年 | 1736篇 |
1999年 | 1389篇 |
1998年 | 1339篇 |
1997年 | 1318篇 |
1996年 | 1441篇 |
1995年 | 1531篇 |
1994年 | 1435篇 |
1993年 | 1288篇 |
1992年 | 1269篇 |
1991年 | 1246篇 |
1990年 | 1191篇 |
1989年 | 1164篇 |
1988年 | 1004篇 |
1987年 | 947篇 |
1986年 | 980篇 |
1985年 | 1047篇 |
1984年 | 1140篇 |
1983年 | 1156篇 |
1982年 | 1166篇 |
1981年 | 1087篇 |
1980年 | 932篇 |
1979年 | 902篇 |
1978年 | 812篇 |
1977年 | 705篇 |
1976年 | 629篇 |
1975年 | 589篇 |
1973年 | 611篇 |
1972年 | 615篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Luís Costa Kirsten Thonicke Benjamin Poulter Franz-W. Badeck 《Regional Environmental Change》2011,11(3):543-551
Within the changing fire regimes of Portugal, the relative importance of humans and climatic variability for regional fire
statistics remains poorly understood. This work investigates the statistical relationship between temporal dynamics of fire
events in Portugal and a set of socioeconomic, landscape, and climatic variables for the time periods of 1980–1990, 1991–2000,
and extreme fires years. For 10 of 15 districts, it was possible to observe moderate shifts in the significance of fire drivers
for the first two decadal periods. For others, pronounced changes of the significance of fire drivers were found across time.
Results point toward a dynamic (perhaps highly non-linear) behavior of socioeconomic and landscape fire drivers, especially
during the occurrence of extreme fire years of 2003 and 2005. At country level, population density alone explained 42% of
the inter-annual and inter-district deviance in number of fires. At the same temporal and spatial scale, the explanatory power
of temperature anomalies proved to explain 43% of area burnt. We highlight the necessity of including a broad set of socioeconomic
and landscape fire drivers in order to account for potential significance shifts. In addition, although climate does trigger
broad favorable fire conditions across Portugal mainland, socioeconomic and landscape factors proved to determine much of
the complex fire patterns at a subnational scale. 相似文献
982.
Mesay Mulugeta Christian J. EngelsenGrethe Wibetoe Walter Lund 《Waste management (New York, N.Y.)》2011,31(2):253-258
The release and charge-based fractionation of As, Cr, Mo, Sb, Se and V were evaluated in leachates generated from recycled concrete aggregates (RCA) in a laboratory and at a field site. The leachates, covering the pH range 8.4-12.6, were generated from non-carbonated, and artificially and naturally carbonated crushed concrete samples. Comparison between the release of the elements from the non-carbonated and carbonated samples indicated higher solubility of the elements from the latter. The laboratory leaching tests also revealed that the solubility of the elements is low at the “natural pH” of the non-carbonated materials and show enhancement when the pH is decreased. The charge-based fractionation of the elements was determined by ion-exchange solid phase extraction (SPE); it was found that all the target elements predominantly existed as anions in both the laboratory and field leachates. The high fraction of the anionic species of the elements in the leachates from the carbonated RCA materials verified the enhanced solubility of the oxyanionic species of the elements as a result of carbonation. The concentrations of the elements in the leachates and SPE effluents were determined by inductively coupled plasma mass spectrometry (ICP-MS). 相似文献
983.
Recycling of the product of thermal inertization of cement-asbestos for various industrial applications 总被引:1,自引:0,他引:1
984.
985.
Patel TM Chheda H Baheti A Patel P Nath K 《Environmental science and pollution research international》2011,19(7):2994-3004
Background and purpose
Besides the opportunities for reuse, stringent regulations and growing public awareness demand an enhanced quality of effluent from dye industries. Treatment of an aqueous solution of dye (reactive red 198) was carried out in a nanofiltration unit using both flat sheet and spiral wound modules to obtain a comparative performance evaluation in terms of permeate flux and quality.Methods
Hydrophilized polyamide membrane with molecular weight cutoff of 150 was used for the experiments. Effects of trans-membrane pressure (TMP), feed concentration and addition of salt on permeate flux were investigated. Percent reduction of color, chemical oxygen demand (COD), total dissolved solid (TDS), and conductivity were determined to assess performance of the membrane.Results
The maximum flux decline was 16.1% of its initial value at 490 kPa TMP with 50 ppm feed concentration in spiral wound module, whereas the same in flat sheet under same conditions was 7.2%. The effect of TMP showed a quasi-linear increase in flux with increasing pressure. Increased permeate concentration led to the reduction in observed retention of dye in the membrane. The average reduction in color, COD, and TDS were 96.88%, 97.38%, and 89.24%, respectively. The decline in permeate flux was more in case of spiral wound module compared to flat sheet. However, spiral wound module performed better in terms of color removal, COD reduction, and TDS removal.Conclusion
Substantial removal of color was achieved in the nanofiltration experiments with a marked reduction in COD and TDS. The process allowed the production of permeate stream with great reutilization possibilities. 相似文献986.
A. M. Rusanov 《Russian Journal of Ecology》2011,42(1):30-37
Data are presented that show the significance of the humus state of chernozem soils, their amphiphilic (hydrophobic-hydrophilic) components, and related physical properties (density, structural condition, and water permeability) for regeneration of natural vegetation and restoration of its species com-position in pasture ecosystems. 相似文献
987.
988.
The World Bank used the Consumer Price Index (CPI) to calculate changes in the world poverty level (measured in U.S. dollars)
prior to 1982. In 1983, the U.S. Bureau of Labor Statistics (BLS) replaced the CPI with several indices including CPI-W which
was then adopted by the World Bank. This caused the inflated rate of the U.S. dollars and the percentage of the world population
in poverty to be dramatically underestimated. This new incorrect procedure gives 25% (1.5 million) below the poverty line
in 2005, while the more appropriate procedure (described herein) gives 52% (3.3 million in 2005). The rapid rise of the poverty
line (using the preferable CPI) starting in 1987 occurred at nearly the same time as the peak in per capita annual cereal
production. 相似文献
989.
N. Mithil Kumar K. Varaprasad G. Ramachandra Reddy G. Siva Mohan Reddy Y. Sivabharathi G. Venkata Subba Reddy S. Venkata Naidu 《Journal of Polymers and the Environment》2011,19(1):225-229
Synthesis and characterization of novel biodegradable, water soluble and optically active DL-malic acid (DMA) and citric acid
(CA) copolymers were studied for possible use as antibacterial agents. The copolymers were synthesized by direct bulk melt
condensation in the absence of a catalyst above 150 °C. Characterization of obtained copolymers was carried out with the help
of infrared absorption spectra, differential scanning calorimetry and thermo gravimetric analysis. The antibacterial activity
of copolymers against bacteria was investigated. The results obtained shows the above copolymers possess a broad wound dressing
activity against different types of bacteria and may be useful as antibacterial agents. 相似文献
990.
Scientific community and policy-makers share the common interest in identifying and evaluating potential impacts of climate change on ecosystems, relying mainly on probabilistic methods of exploring the risks. In this perspective, the concept of ensemble forecasting makes possible to handle uncertainties associated with climate risk analysis by focusing on a range of potential or probable impact scenarios rather than actualizing a single case. In this paper, an ensemble of simulations based on the Lund-Potsdam-Jena (LPJ) model was used to investigate the uncertainty upon predictions of the future Euro-Mediterranean vegetation distribution, carbon dynamics, and water budget. Twenty simulations from past to future were based on the combination of different climate inputs, vegetation model parameterizations, and configurations. The evaluation of results combined the separate deterministic future projections from the LPJ model into a single probabilistic projection, associating a likelihood degree in accordance with the most recent Intergovernmental Panel on Climate Change terminology. Results projected a general critical situation in terms of water availability, made more serious if considering that also the occurrence of extreme-related events, e.g., fires, is expected to become more frequent as favored by more recurrent drought episodes. Although more uncomfortable climate conditions were projected for vegetation, net primary production (NPP) was predicted to increase due to the potential enrichment of CO2 in atmosphere and its fertilization effects on vegetation. The combination of rising NPP and fire frequency may shape the carbon cycle components, as the carbon losses by fire also were projected to increase. 相似文献