全文获取类型
收费全文 | 4576篇 |
免费 | 123篇 |
国内免费 | 715篇 |
专业分类
安全科学 | 228篇 |
废物处理 | 276篇 |
环保管理 | 717篇 |
综合类 | 1249篇 |
基础理论 | 996篇 |
环境理论 | 7篇 |
污染及防治 | 1364篇 |
评价与监测 | 289篇 |
社会与环境 | 157篇 |
灾害及防治 | 131篇 |
出版年
2023年 | 49篇 |
2022年 | 122篇 |
2021年 | 106篇 |
2020年 | 65篇 |
2019年 | 78篇 |
2018年 | 117篇 |
2017年 | 127篇 |
2016年 | 188篇 |
2015年 | 170篇 |
2014年 | 203篇 |
2013年 | 405篇 |
2012年 | 257篇 |
2011年 | 322篇 |
2010年 | 240篇 |
2009年 | 227篇 |
2008年 | 258篇 |
2007年 | 257篇 |
2006年 | 244篇 |
2005年 | 157篇 |
2004年 | 169篇 |
2003年 | 163篇 |
2002年 | 147篇 |
2001年 | 115篇 |
2000年 | 101篇 |
1999年 | 106篇 |
1998年 | 93篇 |
1997年 | 105篇 |
1996年 | 89篇 |
1995年 | 84篇 |
1994年 | 69篇 |
1993年 | 69篇 |
1992年 | 55篇 |
1991年 | 39篇 |
1990年 | 39篇 |
1989年 | 24篇 |
1988年 | 21篇 |
1987年 | 30篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 21篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 30篇 |
1980年 | 19篇 |
1979年 | 16篇 |
1977年 | 11篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1971年 | 11篇 |
排序方式: 共有5414条查询结果,搜索用时 15 毫秒
11.
12.
Peggy A. Johnson Thomas M. Heil 《Journal of the American Water Resources Association》1996,32(6):1283-1291
ABSTRACT: Bankfull depth and discharge are basic input parameters to stream planform, stream restoration, and highway crossing designs, as well as to the development of hydraulic geometry relationships and the classification of streams. Unfortunately, there are a wide variety of definitions for bankfull that provide a range of values, and the actual selection of bankfull is subjective. In this paper, the relative uncertainty in determining the bankfull depth and discharge is quantified, first by examining the variability in the estimates of bankfull and second by using fuzzy numbers to describe bankfull depth. Fuzzy numbers are used to incorporate uncertainty due to vagueness in the definition of bankfull and subjectivity in the selection of bankfull. Examples are provided that demonstrate the use of a fuzzy bankfull depth in sediment trans. port and in stream classification. Using fuzzy numbers to describe bankfull depth rather than a deterministic value allows the engineer to base designs and decisions on a range of possible values and associated degrees of belief that the bankfull depths take on each value in that range. 相似文献
13.
气象卫星遥感在干旱监测中的应用 总被引:23,自引:1,他引:23
本文根据NOAA极轨气象卫星AVHRR资料计算生成植被指数相对距平图用于旱情监测,并在江苏省1994年特大干旱中进行了应用服务 相似文献
14.
15.
Repeated application may increase rates of pesticide dissipation in soil and reduce persistence. The potential for this to occur was investigated for the fungicide, tebuconazole (alpha-[2-(4-chlorophenyl)ethyl]-alpha-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol), when used for peanut (Arachis hypogaea L.) production. Soil samples were collected from peanut plots after each of four tebuconazole applications at 2-wk intervals. Soil moisture was adjusted to field capacity as necessary and samples were incubated in the laboratory for 63 d at 30 degrees C. Untreated plot samples spiked with the compound served as controls. Results indicated accelerated dissipation in field-treated samples with the time to fifty percent dissipation (DT50) decreasing from 43 to 5 d after three tebuconazole applications. Corresponding increases in rates of accumulation and decay of degradates were also indicated. Best-fit equations (r2 = 0.84-0.98) to dissipation kinetic data combined with estimates of canopy interception rates were used to predict tebuconazole and degradates concentration in soil after each successive application. Predicted concentrations compared with values measured in surface soil samples were from twofold less to twofold greater. Use of kinetic data will likely enhance assessments of treatment efficacy and human and ecological risks from normal agronomic use of tebuconazole on peanut. However, the study indicated that varying soil conditions (in particular, soil temperature and water content) may have an equal or greater impact on field dissipation rate than development of accelerated dissipation. Results emphasize that extension of laboratory-derived kinetic data to field settings should be done with caution. 相似文献
16.
VanWoert ND Rowe DB Andresen JA Rugh CL Fernandez RT Xiao L 《Journal of environmental quality》2005,34(3):1036-1044
Urban areas generate considerably more stormwater runoff than natural areas of the same size due to a greater percentage of impervious surfaces that impede water infiltration. Roof surfaces account for a large portion of this impervious cover. Establishing vegetation on rooftops, known as green roofs, is one method of recovering lost green space that can aid in mitigating stormwater runoff. Two studies were performed using several roof platforms to quantify the effects of various treatments on stormwater retention. The first study used three different roof surface treatments to quantify differences in stormwater retention of a standard commercial roof with gravel ballast, an extensive green roof system without vegetation, and a typical extensive green roof with vegetation. Overall, mean percent rainfall retention ranged from 48.7% (gravel) to 82.8% (vegetated). The second study tested the influence of roof slope (2 and 6.5%) and green roof media depth (2.5, 4.0, and 6.0 cm) on stormwater retention. For all combined rain events, platforms at 2% slope with a 4-cm media depth had the greatest mean retention, 87%, although the difference from the other treatments was minimal. The combination of reduced slope and deeper media clearly reduced the total quantity of runoff. For both studies, vegetated green roof systems not only reduced the amount of stormwater runoff, they also extended its duration over a period of time beyond the actual rain event. 相似文献
17.
Septic system leachfields can release dissolved nitrogen in the form of nitrate into ground water, presenting a significant source of pollution. Low cost, passive modifications, which increase N removal in traditional leachfields, could substantially reduce the overall impact on ground water resources. Bench-scale laboratory models were constructed to evaluate the effect of placing an organic layer below the leachfield on total N removal. The organic layer provides a carbon source for denitrification. Column units representing septic leachfields were constructed with sawdust-native soil organic layers placed 0.45 m below the influent line and with thicknesses of 0.0, 0.3, 0.6, and 0.9 m. Using a synthetic septic tank effluent, NO(3)-N concentrations at 3.8 m below the influent line were consistently below 1 mg L(-1) during 10 months of operation compared with a NO(3)-N concentration of nearly 12 mg L(-1) in the control column. The average total N removal increased from 31% without the organic layer to 67% with the organic layer. Total N removal appeared limited by the extent of organic N oxidation and nitrification in the 0.45-m aerobic zone. Design modifications targeted at improving nitrification above the organic layer may further increase total N removal. Increased organic layer thicknesses from 0.3 m to 0.9 m did not significantly improve average total N removal, but caused a shift in residual nitrogen from organic N to ammonia N. Results indicate that addition of a layer of carbon source material at least 0.3 m thick below a standard leachfield substantially improves total N removal. 相似文献
18.
19.
Yu-Pin Lin Hone-Jay Chu Yu-Long Huang Chia-Hsi Tang Shahrokh Rouhani 《Environmental monitoring and assessment》2011,177(1-4):353-373
This study develops a stratified conditional Latin hypercube sampling (scLHS) approach for multiple, remotely sensed, normalized difference vegetation index (NDVI) images. The objective is to sample, monitor, and delineate spatiotemporal landscape changes, including spatial heterogeneity and variability, in a given area. The scLHS approach, which is based on the variance quadtree technique (VQT) and the conditional Latin hypercube sampling (cLHS) method, selects samples in order to delineate landscape changes from multiple NDVI images. The images are then mapped for calibration and validation by using sequential Gaussian simulation (SGS) with the scLHS selected samples. Spatial statistical results indicate that in terms of their statistical distribution, spatial distribution, and spatial variation, the statistics and variograms of the scLHS samples resemble those of multiple NDVI images more closely than those of cLHS and VQT samples. Moreover, the accuracy of simulated NDVI images based on SGS with scLHS samples is significantly better than that of simulated NDVI images based on SGS with cLHS samples and VQT samples, respectively. However, the proposed approach efficiently monitors the spatial characteristics of landscape changes, including the statistics, spatial variability, and heterogeneity of NDVI images. In addition, SGS with the scLHS samples effectively reproduces spatial patterns and landscape changes in multiple NDVI images. 相似文献
20.
苏州市工业用地地表径流污染特性研究 总被引:4,自引:0,他引:4
对苏州新区枫桥工业园湘江路段的10场有效降雨事件的地表径流污染特性进行了研究.研究表明.地表径流水质参数COD、SS、NH3-N、TN、TP均服从对数正态分布,在95%置信水平下,SS与COD、TP、TN之问存在线性相关性(R=0.45~0.72).统计了污染物事件平均浓度(EMC),COD、SS、NH3-N、TN、TP的EMC中值分别为213、491、2.65、5.19、1.07 mg/L,相对应的单位面积污染物负荷分别为1 898、4 375、24、46、10 kg/(hm2·a).与韩国Chongju工业区和上海市相比,SS负荷高是苏州新区枫桥工业园地表径流水质的主要特点,削减SS负荷对控制其非点源污染具有重要意义. 相似文献