全文获取类型
收费全文 | 1454篇 |
免费 | 139篇 |
国内免费 | 315篇 |
专业分类
安全科学 | 289篇 |
废物处理 | 20篇 |
环保管理 | 180篇 |
综合类 | 652篇 |
基础理论 | 393篇 |
环境理论 | 1篇 |
污染及防治 | 126篇 |
评价与监测 | 52篇 |
社会与环境 | 145篇 |
灾害及防治 | 50篇 |
出版年
2024年 | 3篇 |
2023年 | 32篇 |
2022年 | 50篇 |
2021年 | 62篇 |
2020年 | 69篇 |
2019年 | 61篇 |
2018年 | 50篇 |
2017年 | 50篇 |
2016年 | 73篇 |
2015年 | 91篇 |
2014年 | 67篇 |
2013年 | 112篇 |
2012年 | 120篇 |
2011年 | 134篇 |
2010年 | 86篇 |
2009年 | 103篇 |
2008年 | 87篇 |
2007年 | 107篇 |
2006年 | 94篇 |
2005年 | 66篇 |
2004年 | 65篇 |
2003年 | 56篇 |
2002年 | 54篇 |
2001年 | 32篇 |
2000年 | 31篇 |
1999年 | 26篇 |
1998年 | 14篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 19篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 8篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1908条查询结果,搜索用时 234 毫秒
871.
干沟泥石流是一条典型的下游集中补给型泥石流沟,其物源的启动、流通与堆积在700 m范围内完成.以2005年干沟泥石流过程为例,应用三种计算公式对该沟泥石流的动力学参数进行了计算.通过计算发现,三种公式计算结果差别不大,并取其平均值作为计算结果.根据干沟泥石流流量计算和形态调查对比分析,认为2005年干沟泥石流的形成过程具有明显的堵溃效应,且前期降雨对泥石流的发生影响较为明显.在对干沟泥石流动力学参数计算、物源补给特征及形成过程分析的基础上,认为干沟在2005年后易形成高频泥石流,对该沟泥石流开展监测预警尤为必要,提出了该沟泥石流监测预警方式并予以实施,可为干沟泥石流的防灾减灾提供科学依据. 相似文献
872.
GRAEME C. HAYS SABRINA FOSSETTE KOSTAS A. KATSELIDIS GAIL SCHOFIELD MIKE B. GRAVENOR 《Conservation biology》2010,24(6):1636-1643
Abstract: Species that have temperature‐dependent sex determination (TSD) often produce highly skewed offspring sex ratios contrary to long‐standing theoretical predictions. This ecological enigma has provoked concern that climate change may induce the production of single‐sex generations and hence lead to population extirpation. All species of sea turtles exhibit TSD, many are already endangered, and most already produce sex ratios skewed to the sex produced at warmer temperatures (females). We tracked male loggerhead turtles (Caretta caretta) from Zakynthos, Greece, throughout the entire interval between successive breeding seasons and identified individuals on their breeding grounds, using photoidentification, to determine breeding periodicity and operational sex ratios. Males returned to breed at least twice as frequently as females. We estimated that the hatchling sex ratio of 70:30 female to male for this rookery will translate into an overall operational sex ratio (OSR) (i.e., ratio of total number of males vs females breeding each year) of close to 50:50 female to male. We followed three male turtles for between 10 and 12 months during which time they all traveled back to the breeding grounds. Flipper tagging revealed the proportion of females returning to nest after intervals of 1, 2, 3, and 4 years were 0.21, 0.38, 0.29, and 0.12, respectively (mean interval 2.3 years). A further nine male turtles were tracked for short periods to determine their departure date from the breeding grounds. These departure dates were combined with a photoidentification data set of 165 individuals identified on in‐water transect surveys at the start of the breeding season to develop a statistical model of the population dynamics. This model produced a maximum likelihood estimate that males visit the breeding site 2.6 times more often than females (95%CI 2.1, 3.1), which was consistent with the data from satellite tracking and flipper tagging. Increased frequency of male breeding will help ameliorate female‐biased hatchling sex ratios. Combined with the ability of males to fertilize the eggs of many females and for females to store sperm to fertilize many clutches, our results imply that effects of climate change on the viability of sea turtle populations are likely to be less acute than previously suspected. 相似文献
873.
874.
Gilmen Smyth Micheline Gagnon Roch Roy 《International journal of occupational safety and ergonomics》2013,19(1):64-77
Back problems resulting from the compression forces on the intervertebral disks during manual material-handling tasks are an important problem affecting workers in various industries. The quantification of these forces using intradiscal pressure or biomechanical modeling is complex, time consuming, and costly, and these methods cannot be readily used in the workplace to estimate loadings on the lower back. The objective of this study was to develop a predictive model that would allow the estimation of lumbar loadings for lifting and lowering boxes using easily measured anthropometric variables and variables related to the task. A dynamic and planar segmental model and a model of internal forces at L5/S1 were used to determine the compression forces on the lower back. Two predictive models, a field model and a laboratory model, were developed to estimate the compression forces when lifting or lowering 3.3 kg to 22.0 kg boxes between heights of 15 cm and 185 cm. Both models were validated by an examination of the residuals. Their predictive performance was also compared, with the laboratory model offering a slightly better prediction than the field model. Thus, these equations represent a practical tool for a better planning of handling tasks in the working environment with the purpose of reducing the back injuries of workers. 相似文献
875.
Modifications to ecosystems often lead to externalities that can be assigned an economic value and traded in ecosystem service markets. One such value may include the provisioning of nest sites for organisms that would otherwise be ousted from the surrounding cultural landscape, such as the sand martin (Riparia riparia), small passerine utilizing river bank rippings when available. The studied sand martin population was initially characterized as relying heavily on human activities for habitat, as extensive river regulation caused the relocation of 97% of Czech sand martins to man-made habitats, most commonly sandpits and gravel-sandpits. The socioeconomic changes and strict implementation of the EIA law had further detrimental effects on this species, which already adjusted to the human-dominated landscape, ousting it for a second time from its key nesting habitats, causing closure 86% of sandpits with only occasional quarrying and closure of 47% of those with regular small-scale regular quarrying. Meanwhile, large-scale quarries remained nearly unaffected. Conversion of any actively quarried site to that with vertical slopes present, but with quarrying absent, led to the progressive disappearance of sand martin colonies in 73% of sandpits with ceased occasional quarrying and in 87% of sandpits with ceased regular small-scale quarrying. The sharp decrease in the number of nest-sites of a bird protected by law is a gloomy result of the hypertrophied business regulation (EIA is estimated to cost € 970 million annually in the E.U. alone) aimed, paradoxically, to support the environment. 相似文献
876.
John F. Joseph Hatim O. Sharif Jeffrey G. Arnold David D. Bosch 《Journal of the American Water Resources Association》2013,49(2):300-318
Abstract: The calibration of basin‐scale hydrologic models consists of adjusting parameters such that simulated values closely match observed values. However, due to inevitable inaccuracies in models and model inputs, simulated response hydrographs for multiyear calibrations will not be perfectly synchronized with observed response hydrographs at the daily time step. An analytically derived formula suggests that when timing errors are significant, traditional calibration approaches may generally underestimate the total event‐flow volume. An event‐adaptive time series is developed and incorporated into the Nash‐Sutcliffe Efficiency objective function to diagnose the potential impact of event‐flow synchronization errors. Test sites are the 50 km2 Subwatershed I of the Little River Experimental Watershed (LREWswI) in southeastern Georgia, and the 610 km2 Little Washita River Experimental Watershed (LWREW) in southwestern Oklahoma, with the Soil and Water Assessment Tool used as the hydrologic model. Results suggest that simulated surface runoff generation is 55% less for LREWswI when the daily time series is used compared with when the event‐adaptive technique is used. Event‐flow generation may also be underestimated for LWREW, but to a lesser extent than it may be for LREWswI, due to a larger portion of the event flow being lateral flow. 相似文献
877.
喹诺酮类抗生素在城市典型水环境中的分配系数及其主要环境影响因子 总被引:3,自引:3,他引:0
沉积物作为抗生素在水环境中的主要赋存介质,越来越多的研究关注抗生素在水体-沉积物中的分配行为;但此前研究多基于实验室模拟,而在自然水环境中抗生素的分配行为及其与环境因子相关性研究则较少关注.鉴于此,以石家庄市地表水和沉积物为研究对象,采用超高效液相色谱串联质谱法(HPLC-MS)分析石家庄水环境中喹诺酮类(QNs)抗生素的时空分布特征,计算其在水和沉积物中的分配系数,并确定自然水环境中分配系数的主要环境影响因子.结果表明:①在石家庄市水体和沉积物中QNs含量分别为8.0~4.4×103 ng·L-1和16~2.2×103 ng·g-1,其中恩诺沙星(ENR)和氧氟沙星(OFL)分别是水体和沉积物中主要的QNs抗生素;②石家庄市水体中QNs总含量呈现12月(1.0×104 ng·L-1)大于4月(5.5×103 ng·L-1)的趋势,沉积物中QNs亦呈现12月(7.8×103 ng·g-1)大于4月的趋势(6.2×103 ng·g-1);③石家庄市水环境中QNs抗生素的分配系数变化范围为34~2.9×105 L·kg-1,且呈现12月大于4月的趋势;④相关性分析结果表明,总氮(TN)、硝氮(NO3--N)、亚硝氮(NO2--N)和氨氮(NH4+-N)与大部分QNs[OFL、诺氟沙星(NOR)、ENR、双氟沙星(DIF)和喹酸(OXO)]分配系数显著相关,温度(T)、总有机碳(TOC)和总溶解性固体颗粒物(TDS)与个别QNs[马波沙星(MAR)和DIF]分配系数显著相关.因此,水体富营养化水平会影响抗生素在水体-沉积物中的分配行为. 相似文献
878.
Zuyin Chen Lihua Li Lichong Hao Yu Hong Wencai Wang 《Frontiers of Environmental Science & Engineering》2022,16(1):2
879.
Hengrui Tao Jia Xing Gaofeng Pan Jonathan Pleim Limei Ran Shuxiao Wang Xing Chang Guojing Li Fei Chen Junhua Li 《Frontiers of Environmental Science & Engineering》2022,16(4):44
880.
配制模拟番茄酱废水,在高径比为10的SBR反应器中,考察连续曝气条件下好氧颗粒污泥(AGS)的除污性能和微生物特性的变化。建立流体动力学模型,模拟反应器中气〖CD*2〗液〖CD*2〗污泥三相流的流态,以了解其对污泥颗粒化的影响机理。结果表明:污泥完全颗粒化后,对番茄酱废水中COD、NH3-N和PO3-4-P的去除率分别为94.37%、93.55%和9092%;绿弯菌门(Chloroflexi)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)丰度显著提高,假丝酵母菌(Candidatus saccharibacteria)为除磷功能微生物;反应器内的流态结构呈环流和旋涡流,水力剪切力的大小与颗粒粒径呈正相关,颗粒形态与流态分布有关。 相似文献