全文获取类型
收费全文 | 3320篇 |
免费 | 30篇 |
国内免费 | 173篇 |
专业分类
安全科学 | 96篇 |
废物处理 | 198篇 |
环保管理 | 291篇 |
综合类 | 592篇 |
基础理论 | 777篇 |
环境理论 | 2篇 |
污染及防治 | 1130篇 |
评价与监测 | 241篇 |
社会与环境 | 183篇 |
灾害及防治 | 13篇 |
出版年
2023年 | 18篇 |
2022年 | 69篇 |
2021年 | 40篇 |
2020年 | 24篇 |
2019年 | 37篇 |
2018年 | 117篇 |
2017年 | 51篇 |
2016年 | 76篇 |
2015年 | 84篇 |
2014年 | 90篇 |
2013年 | 268篇 |
2012年 | 89篇 |
2011年 | 157篇 |
2010年 | 138篇 |
2009年 | 152篇 |
2008年 | 160篇 |
2007年 | 186篇 |
2006年 | 144篇 |
2005年 | 117篇 |
2004年 | 144篇 |
2003年 | 139篇 |
2002年 | 115篇 |
2001年 | 239篇 |
2000年 | 143篇 |
1999年 | 71篇 |
1998年 | 40篇 |
1997年 | 47篇 |
1996年 | 33篇 |
1995年 | 40篇 |
1994年 | 42篇 |
1993年 | 41篇 |
1992年 | 30篇 |
1991年 | 35篇 |
1990年 | 27篇 |
1989年 | 32篇 |
1988年 | 20篇 |
1987年 | 17篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 18篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 11篇 |
1979年 | 13篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1975年 | 12篇 |
1973年 | 9篇 |
1972年 | 10篇 |
排序方式: 共有3523条查询结果,搜索用时 828 毫秒
681.
填埋堆体表面形变监测是填埋场库容管理和堆体失稳等风险分析的核心,其时空高分辨率监测研究近年来引起广泛关注。基于航空摄影的地表测量技术具有采集速度快、时空分辨率高等优点,但在填埋场特殊环境下,面对高频填埋活动、显著的堆体变化以及防雨膜覆盖等干扰时,要同时满足高时空分辨率和耗时短的动态监测要求,无人机的最佳飞行参数设定亟待研究。为此,该研究模拟中等规模危险废物填埋场的规模和日填埋量,利用专业级无人机获取模拟区域图像,空三加密处理生成三维点云数据,利用Arcmap叠加分析多期监测数据,从点位坐标、重构尺度、重构体积、体积差分精度4个角度分析重构误差。结果表明:三维重构的坐标精度可以达到米级;重构尺度误差为2~3 cm,重构体积误差为0.16~0.17 m3,差分体积误差为0.16~0.17 m3;进一步研究发现,高度为25~55 m时,高度越高精度越低,相机倾角为[-53°,-60°]时,精度最高,旁向重叠率大于80%时,误差骤减且基本稳定。考虑到填埋场的填埋作业间隔、无人机续航能力等对飞行时间的约束,为获得最佳精度,建议无人机飞行高度为37 m、相机倾斜角度为[-53°,-60°]、旁向重叠率为80%。 相似文献
682.
Numerical study on the ozone formation inside street canyons using a
chemistry box model 总被引:1,自引:1,他引:0
Tropospheric ozone is a secondary air pollutant produced in the presence of nitrogen oxides (NO_x),volatile organic compounds (VOCs),and solar radiation.In an urban environment,ground-level vehicular exhaust is the major anthropogenic source of ozone precursors.In the cases of street canyons,pollutant dilution is weakened by the surrounding buildings that creates localized high concentration of NO_x and VOCs,and thus leads to high potential of ozone formation.By considering the major physical and chemica... 相似文献
683.
Çetin Tolga Solak Cüneyt Nadir Yılmaz Elif 《Environmental science and pollution research international》2021,28(32):43567-43578
Environmental Science and Pollution Research - The K?z?l?rmak River is the longest river (1.355 km) in Turkey and flows into the Black Sea. Main pressures in the basin are waste... 相似文献
684.
Summary The purpose of the paper is to examine the feasibility of used oil drums as a lining material for shallow rural wells. The discussion focuses upon the comparison of the water quality in the oil drum-lined holes with other local water sources. The response to the innovation, from a range of guinea worm prone rural environments in Ibarapa district, Oyo State, Nigeria, was encouraging. The study noted substantial reductions in cyclop population (potential for guinea worm infection) and improved water quality in the sanitary wells as compared to rural ponds. Investigations also reveal substantial saving in costs in using oil drum-lining as opposed to concrete. Findings point to the need for this kind of water scheme as opposed to sophisticated boreholes, and deep well programmes, especially in situations of limited funds and technical skills necessary to install and maintain water supply systems.Dr Abimbola Y. Sangodoyin obtained his first degree in Agricultural Engineering at the University of Ibadan. He subsequently obtained a MSc in Water Resources Technology and a PhD in Civil Engineering at the University of Birmingham, UK. He is currently a lecturer in the Department of Agricultural Engineering, University of Ibadan where his research has focused on rural water systems and urban solid waste disposal and pollution problems.Mr Miebaka J. Ayotamuno has trained to Master's level as an Agricultural Engineer at the University of Ibadan. He is currently a member of staff at the Department of Agricultural Engineering, River State University of Science and Technology, Port Harcourt, Nigeria. 相似文献
685.
Light microscopic study of different body organs of cat-fish following exposure to HgCl2 0.2 mg/L in water for 30 days revealed that focal degeneration of liver cells and disorganization of hepatic cords occurred at places. Furthermore, centrilobular atrophy and compensatory hypertrophy of some hepatic cells were also observed. In the kidneys disintegration of renal epithelium along with displacement of nuclei, shrinkage of glomeruli, breakdown of Bowman's capsule and heavy infiltration by inflammatory cells were observed. The histopathological changes noted in the intestine included degeneration of lining epithelium, and diminution of goblet cells. Microscopic section of ovaries exhibited reduction of ooplasm leading to formation of atypical oocytes. An increase in the occurrence of atretic oocytes and interfolicular spaces was also discernible. No histopathological lesions could be detected in testes of male fish probably because of the difference in the maturity of the control and experimental groups. The pathomorphological alterations in relation to mercury toxicity in spleen were associated with the disorganization of the splenic cords resulting in the displacement of lymphatic tissue cells within the substance of splenic pulp. Marked depletion of the red pulp was noticeable. 相似文献
686.
687.
688.
689.
A brush delivered to the biopsy site by a metal introducer and cannula set was tested as an alternative implement for transcervical collection of chorionic villi. This implement was easy to use and readily identified by ultrasound. With only one attempt at sampling, the overall collection rate for 83 patients was 65 per cent. With practice 84 per cent successful collection was achieved. Gestations between 8 and 11 weeks was the best time for collection of chorionic villi. A single sampling can produce adequate material (15 mg wet weight) suitable for diagnostic purposes. No gestation sac was perforated but some slight bleeding followed the procedure. Appreciable success following a single sampling attempt coupled with the low complication rate suggests that this technique may have clinical application and deserves further investigation. 相似文献
690.
US Energy Conservation and Efficiency: Benefits and Costs 总被引:1,自引:0,他引:1
D. Pimentel A. Pleasant J. Barron J. Gaudioso N. Pollock E. Chae Y. Kim A. Lassiter C. Schiavoni A. Jackson M. Lee A. EATON 《Environment, Development and Sustainability》2004,6(3):279-305
With increased energy conservation plus the adoption of diverse energy efficient technologies, the US economy could save about 32 quads or about 33% of its current energy consumption, if sound conservation energy use policies were implemented over approximately 10 years. This potential of 32 quads is slightly greater than the current US oil imports. The systems that have the greatest potential to provide major energy savings are transportation, residential energy use, and the food system. Not only saving energy has merit in itself, but it would save US citizens approximately $438 billion per year, helping support the US economy, a high standard of living, and energy security. In addition, this analysis suggests that reducing the $40 billion in taxpayer money spent on subsidies of the energy industries would further increase conservation. 相似文献