全文获取类型
收费全文 | 780篇 |
免费 | 136篇 |
国内免费 | 49篇 |
专业分类
安全科学 | 471篇 |
废物处理 | 14篇 |
环保管理 | 64篇 |
综合类 | 233篇 |
基础理论 | 65篇 |
污染及防治 | 7篇 |
评价与监测 | 22篇 |
社会与环境 | 16篇 |
灾害及防治 | 73篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 29篇 |
2021年 | 40篇 |
2020年 | 45篇 |
2019年 | 42篇 |
2018年 | 18篇 |
2017年 | 41篇 |
2016年 | 55篇 |
2015年 | 57篇 |
2014年 | 31篇 |
2013年 | 30篇 |
2012年 | 72篇 |
2011年 | 64篇 |
2010年 | 34篇 |
2009年 | 44篇 |
2008年 | 34篇 |
2007年 | 46篇 |
2006年 | 41篇 |
2005年 | 54篇 |
2004年 | 22篇 |
2003年 | 31篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 11篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1971年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有965条查询结果,搜索用时 312 毫秒
891.
892.
Effluent monitoring typically requires a large number of analytes and samples during the initial or startup phase of a facility. Once a baseline is established, the analyte list and sampling frequency may be reduced. Although there is a large body of literature relevant to the initial design, few, if any, published papers exist on updating established effluent monitoring programs. This paper statistically evaluates four years of baseline data to optimize the liquid effluent monitoring efficiency of a centralized waste treatment and disposal facility at a large defense nuclear complex. Specific objectives were to: (1) assess temporal variability in analyte concentrations, (2) determine operational factors contributing to waste stream variability, (3) assess the probability of exceeding permit limits, and (4) streamline the sampling and analysis regime. Results indicated that the probability of exceeding permit limits was one in a million under normal facility operating conditions, sampling frequency could be reduced, and several analytes could be eliminated. Furthermore, indicators such as gross alpha and gross beta measurements could be used in lieu of more expensive specific isotopic analyses (radium, cesium-137, and strontium-90) for routine monitoring. Study results were used by the state regulatory agency to modify monitoring requirements for a new discharge permit, resulting in an annual cost savings of US $223,000. This case study demonstrates that statistical evaluation of effluent contaminant variability coupled with process knowledge can help plant managers and regulators streamline analyte lists and sampling frequencies based on detection history and environmental risk. 相似文献
893.
894.
Chronic amniotic fluid leakage is a rare complication of genetic amniocentesis. Pregnancy outcomes in two such patients are presented and six previous cases reviewed. Although chorioamnionitis has not been reported, potentially serious complications may occur including an increased risk for pre-term delivery and fetal skeletal deformity. While conservative management of post-amniocentesis amniotic fluid leakage is advocated, patients should be advised of these risks. 相似文献
895.
896.
897.
Jenq-Tzong Shiau Hsin-Yi Wang Chang-Tai Tsai 《Journal of the American Water Resources Association》2006,42(6):1549-1564
Abstract: Bivariate flood frequency analysis offers improved understanding of the complex flood process and useful information in preparing flood mitigation measures. However, difficulties arise from limited bivariate distribution functions available to jointly model the correlated flood peak and volume that have different univariate marginal distributions. Copulas are functions that link univariate distribution functions to form bivariate distribution functions, which can overcome such difficulties. The objective of this study was to analyze bivariate frequency of flood peak and volume using copulas. Separate univariate distributions of flood peak and volume are first fitted from observed data. Copulas are then employed to model the dependence between flood peak and volume and join the predetermined univariate marginal distributions to construct the bivariate distribution. The bivariate probabilities and associated return periods are calculated in terms of univariate marginal distributions and copulas. The advantage of using copulas is that they can separate the effect of dependence from the effects of the marginal distributions. In addition, explicit relationships between joint and univariate return periods are made possible when copulas are employed to construct bivariate distribution of floods. The annual floods of Tongtou flow gauge station in the Jhuoshuei River, Taiwan, are used to illustrate bivariate flood frequency analysis. 相似文献
898.
Xiaobo Zhou Naraine Persaud Huaguo Wang Hangsheng Lin 《Journal of the American Water Resources Association》2006,42(6):1659-1670
Abstract: Multifractal scaling behavior of long-term records of daily runoff time series in 32 subwatersheds covering a wide range of sizes was examined. These subwatersheds were associated with four agricultural watersheds with different climates and topography. The empirical moment scaling curves obtained using the trace moment method showed that the runoff time series exhibited a multifractal behavior, which was valid over a time scale range from one day to about three years. The multi-fractal scaling of the runoff time series was well described by the Universal Multifractal Model. The spectral analysis (β < 1) and the order of fractional integration (H ⋍; 0) indicated that the runoff time series were conservative. The multifractal parameters, α (multifractal index) and C1 (co-dimension), were reasonably close to each other for subwatersheds within each of the watersheds and were generally similar among the four watersheds. The α values of the four watersheds were 1.10 ± 0.13, 1.61 ± 0.06,1.61 ± 0.24, and 1.63 ± 0.19. The C1 values of four watersheds were 0.19 ± 0.01, 0.17 ± 0.01, 0.17 ± 0.04, and 0.11 ± 0.02. The multifractal analyses provided useful insight into the runoff time series, especially the occurrence and distribution of extreme events. 相似文献
899.
依据高斯模型瞬间泄漏原理,以Visual Basic 6.0和Oracle 8i为开发工具,建立了一个毒气瞬间泄漏后伤害区域的评估系统.该系统根据有毒气体泄漏时的各条件参数,按照高斯模型将毒气浓度视为时间和位置的函数,参考中毒人员在毒气中的暴露时间,计算出中毒人员毒气吸入量,并以该吸入量为标准,该系统将毒气泄漏后的影响区域划分为致死区、重伤区和致伤区.系统输出的结果为二维的伤害区域的边界,使其计算结果科学、直观和实用. 相似文献
900.
模拟评估法在液氨泄漏事故后果预测中的应用 总被引:2,自引:0,他引:2
结合安徽某公司生产工艺的实际,对其液氨储罐区进行了危险性分析和重大危险源的辨识,并利用事故模拟评估技术,对液氨泄漏事故进行了模拟预测。研究结果表明:在风速为2.7m/s,大气稳定度级别为中性的条件下,持续泄漏半小时后,下风向的扩散范围将达到129.47m,方向上的扩散距离达到8.47m,毒害面积为1722.55m2,在该范围内人吸入氨气5~10min将会死亡。该研究为安全评价提供参考并为政府企业制定安全应急预案提供定量科学数据。 相似文献