全文获取类型
收费全文 | 2595篇 |
免费 | 194篇 |
国内免费 | 600篇 |
专业分类
安全科学 | 118篇 |
废物处理 | 18篇 |
环保管理 | 498篇 |
综合类 | 1605篇 |
基础理论 | 371篇 |
环境理论 | 1篇 |
污染及防治 | 137篇 |
评价与监测 | 211篇 |
社会与环境 | 315篇 |
灾害及防治 | 115篇 |
出版年
2024年 | 7篇 |
2023年 | 51篇 |
2022年 | 89篇 |
2021年 | 93篇 |
2020年 | 80篇 |
2019年 | 71篇 |
2018年 | 91篇 |
2017年 | 109篇 |
2016年 | 138篇 |
2015年 | 156篇 |
2014年 | 127篇 |
2013年 | 183篇 |
2012年 | 200篇 |
2011年 | 208篇 |
2010年 | 175篇 |
2009年 | 171篇 |
2008年 | 116篇 |
2007年 | 185篇 |
2006年 | 185篇 |
2005年 | 163篇 |
2004年 | 106篇 |
2003年 | 107篇 |
2002年 | 87篇 |
2001年 | 63篇 |
2000年 | 67篇 |
1999年 | 43篇 |
1998年 | 35篇 |
1997年 | 21篇 |
1996年 | 30篇 |
1995年 | 25篇 |
1994年 | 19篇 |
1993年 | 27篇 |
1992年 | 29篇 |
1991年 | 14篇 |
1990年 | 15篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1984年 | 3篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1972年 | 9篇 |
1971年 | 6篇 |
排序方式: 共有3389条查询结果,搜索用时 15 毫秒
11.
淮河干流及主要支流夏季浮游植物群落生物多样性评价 总被引:6,自引:0,他引:6
浮游植物是水生态系统的重要组成部分,其群落变化与水体环境条件密切相关,是反映河流健康的主要生物指标.为揭示淮河流域浮游植物群落特征及其与水质的相互关系,于2015年夏季对淮河流域典型水体—淮河干流、沙颍河、涡河和淠河进行系统的水质及浮游植物调查,探明浮游植物群落及其空间分布特征,并结合水体理化指标和生物指数进行水质评价.结果表明,淮河干流及主要支流27个点位中共获得浮游植物8门71属153种,主要隶属于绿藻门(Chlorophyta)、硅藻门(Bacillariophyta)、蓝藻门(Cyanophyta).浮游植物密度为0.019×10~5~131.824×10~5ind·L~(-1),不同河段浮游植物分布表现出较为显著的空间差异性,平均密度大小呈现沙颖河淮河干流涡河淠河的特点.非参数多维尺度分析(Non-metric Multidimensional Scaling,NMDS)表明,淮河干流、淠河和涡河的浮游植物群落组成和结构的相似性较高,而与沙颍河的浮游植物群落存在一定的差异.Shannon多样性指数H'介于0.78~3.21之间,Margalef丰富度指数D介于1.03~4.79之间,Pielou均匀度指数J介于0.12~0.73之间.水质生物评价结果显示,淮河流域大部分水体处于中等污染状况,部分点位处于重污染状况,其结果与水质综合污染指数评价结果具有较好的一致性.研究结果可为淮河水污染防治和水生态修复提供基础依据. 相似文献
12.
土地利用方式下土壤有机碳特征及影响因素——以后寨河喀斯特小流域为例 总被引:1,自引:0,他引:1
为研究喀斯特小流域土壤有机碳空间分布与土地利用之间的关系,基于网格法在后寨河流域挖掘了2 755个土壤剖面,并采集了22 057个土壤样品。分析了后寨河流域不同土地利用方式下土壤有机碳密度特征。结果表明:后寨河流域土壤有机碳密度主要受人为干扰、土壤厚度与岩石裸露率的制约。不同利用方式土壤有机碳密度(0~100 cm)总体上呈现以下规律:水田>旱地>经果林地>园地>草地>弃耕地>坡耕地>乔灌木林地>乔木林地>荒地>灌木林地>灌草地。后寨河流域100 cm土壤有机碳平均碳密度为8.70 kg/m2,低于中国土壤有机碳平均密度10.83 kg/m2,总有机碳储量为5.39×108 kg。科学合理地进行土地利用方式调整与管理,可以增大喀斯特小流域土壤有机碳储量。 相似文献
13.
A membrane extraction-gas chromatography method was developed fordetermination of organophosphorus pesticides and related compounds including methamidophos, DDVP, dimethoate, methyl parathion, parathion, thiophosphoric acid trimethyl ester, and thiophosphoramidic acid dimethyl ester in water samples. In thismethod, surface-modified acetic cellulose membranes were used to extract the target analytes in water samples, the extracted analytes were back-extracted into a small amount of methanol, andgas chromatography with pulsed flame photometric detector (GC-PFPD) was used to determine the concentrations of targetanalytes in the extracts. The recoveries obtained for thetarget analytes spiked into the water samples ranged from 66to 94%. The method detection limit for each target analyte was 0.05 g L-1. The method developed in this study had shown the advantages of being cheap, simple, fast, and reliable. It had been used successfully to determine the concentrations of target analytes in river water samples. 相似文献
14.
A study was carried out in a part of Palar and Cheyyar river basin to evaluate the current status of iron, manganese, zinc and atrazine concentrations, their origin and distribution in groundwater. Groundwater samples were collected during post-monsoon (March 1998 and February 1999) and pre-monsoon (June 1999) periods from 41 sampling wells distributed throughout the study area. The groundwater samples were analyzed for trace metals using AAS and atrazine using HPLC. The concentration of the trace elements in groundwater is predominant during pre-monsoon period. Distribution pattern indicates that the concentration of these elements increases from west to northeast and towards Palar river. Lower concentrations in the central part may be due to recharge of fresh water from the lakes located here. During most of the months, as there is no flow in Palar river, the concentrations of trace elements in groundwater are high. Drinking water standards indicate that Mn and Zn cross the permissible limit recommended by EPA during the pre-monsoon period. A comparison of groundwater data with trace element chemistry of rock samples shows the abundance of trace elements both in the rock and water in the order of Fe > Mn > Zn and Fe > Zn > Mn. This indicates that iron in groundwater is derived from lithogenic origin. Further, Fe, Mn and Zn have good correlation in rock samples, while it is reverse in the case of water samples, indicating the non-lithogenic origin of Mn and Zn. Atrazine (a herbicide) was not detected in any of the groundwater samples in the study area, perhaps due to low-application rate and adsorption in the soil materials. 相似文献
15.
16.
Macroinvertebrate Regionalisation for use in the Management of Aquatic Ecosystems in Victoria, Australia 总被引:5,自引:0,他引:5
The development of a broader, more holistic approach to aquaticecosystem management has been called for in recent years. Physical and chemical objectives alone are no longer consideredsufficient for the protection of aquatic ecosystems and shouldbe supplemented with biological objectives. The ubiquitousand sedentary nature of macroinvertebrates, combined with theirmeasurable response to environmental conditions, favour their use as important indicators in environmental policies. To establish biological objectives, there is a need for a regionalframework to limit the variability between ecosystems. Past studies have demonstrated that an a posteriori regionalisationapproach may be more useful than an a priori approach in explaining single component (e.g. macroinvertebrates) patternsacross ecosystems. This is particularly important as aquaticresource management agencies often focus on one or twocomponents of the ecosystem to assess environmental health. This study uses an a posteriori method to delineate and describebiological regions based on edge and riffle macroinvertebrate data. The regionalisation will provide a framework for settingbiological objectives, based on the range of reference conditionsmeasured within each separate region. The objectives will includeregional checklists for taxa and biotic indices. Predictive modelling in the style of RIVPACS or AUSRIVAS will also be usedwithin each region to develop objectives, incorporating local, regional and systematic features as predictor variables. 相似文献
17.
Georgios D. Gikas Trisevgeni Yiannakopoulou Vassilios A. Tsihrintzis 《Environmental Modeling and Assessment》2006,11(3):219-233
SWAT ver. 2000 was used to predict hydrographs, and sediment, nitrate and total phosphorus loadings from a 1349 km2 mountainous/agricultural watershed in Northern Greece. The model was calibrated and verified using continuous meteorological
data from eight stations within the drainage area, and runoff, sediment and nutrient concentrations measured at nine stations
located within the main tributaries of the watershed, for the time period from May 1st, 1998 to January 31st, 2000. Model
validation methodology and resulting input parameters appropriate for Mediterranean drainage basins are presented. Predicted
by the model hydrographs, sedimentographs and pollutographs are plotted against observed values and show good agreement. Model
performance is evaluated using the root mean square error computation and scattergrams of predicted versus observed data.
The validated model is also used to test the effectiveness of three alternative cropping scenarios in reducing nutrient loadings
from the agricultural part of the watershed. The study showed that this model, if properly validated, can be used effectively
in testing management scenarios in Mediterranean drainage basins. 相似文献
18.
19.
水蚀风蚀交错带小流域生态环境综合治理模式研究 总被引:26,自引:1,他引:26
水蚀风蚀交错带是黄土高原侵蚀最严重的地区和黄河下游河床粗泥沙的主要来源区,其生态环境脆弱、治理难度大,加之晋陕蒙能源基地的大规模开发,也带来了新的环境问题。鉴于治黄和煤田开发及生态环境整治的紧迫需要,以水蚀风蚀交错带六道沟小流域为试区,分析研究了该区水蚀风蚀时空分布规律及脆弱生态环境特征,提出以防治水蚀和风蚀为中心,以提高生态经济效益和持续发展为目标,以基本农田优化结构和高效利用及植被建设为重点,建立具有防蚀固沙兼高效生态经济功能的大农业复合生态系统综合治理模式,取得了良好的社会与经济效益。 相似文献
20.