全文获取类型
收费全文 | 7503篇 |
免费 | 527篇 |
国内免费 | 2708篇 |
专业分类
安全科学 | 647篇 |
废物处理 | 383篇 |
环保管理 | 590篇 |
综合类 | 4452篇 |
基础理论 | 1172篇 |
污染及防治 | 2492篇 |
评价与监测 | 352篇 |
社会与环境 | 346篇 |
灾害及防治 | 304篇 |
出版年
2024年 | 26篇 |
2023年 | 179篇 |
2022年 | 411篇 |
2021年 | 375篇 |
2020年 | 295篇 |
2019年 | 250篇 |
2018年 | 315篇 |
2017年 | 405篇 |
2016年 | 418篇 |
2015年 | 478篇 |
2014年 | 576篇 |
2013年 | 722篇 |
2012年 | 633篇 |
2011年 | 706篇 |
2010年 | 539篇 |
2009年 | 505篇 |
2008年 | 546篇 |
2007年 | 454篇 |
2006年 | 436篇 |
2005年 | 310篇 |
2004年 | 229篇 |
2003年 | 228篇 |
2002年 | 221篇 |
2001年 | 190篇 |
2000年 | 201篇 |
1999年 | 188篇 |
1998年 | 181篇 |
1997年 | 135篇 |
1996年 | 126篇 |
1995年 | 101篇 |
1994年 | 80篇 |
1993年 | 74篇 |
1992年 | 57篇 |
1991年 | 33篇 |
1990年 | 40篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
为研究枯水期巢湖水体悬浮颗粒物(SPM)营养元素组成及其潜在环境效应,分析了2020年1月巢湖18个采样点表层水体SPM含量、颗粒有机质(SPOM)含量及氮磷组成,并利用颗粒有机碳、氮同位素组成及C/N研究了冬季巢湖SPOM的来源及其空间变化. 结果表明,悬浮颗粒物总磷(PP)浓度为0.032~0.065 mg/L,平均值为0.049 mg/L;悬浮颗粒物无机磷(PIP)浓度为0.018~0.046 mg/L,平均值为0.032 mg/L,是PP的主要组分,二者浓度均呈西湖区>东湖区>中湖区的空间分布特征. 悬浮颗粒物总氮(PN)浓度为0.254~0.424 mg/L,平均值为0.342 mg/L,其中悬浮颗粒物有机氮(PON)占比较高,表明颗粒态氮以湖泊内源性有机来源为主. 巢湖表层水体SPOM的δ13C范围在?28.72‰~?26.68‰之间,δ15N为3.34‰~9.97‰,C/N为2.51±0.95,指示冬季枯水期水体SPOM主要来自内源水生生物碎屑,而陆源径流输入对湖泊颗粒物影响较小. 研究显示:冬季巢湖悬浮颗粒有机质主要来自湖泊内源,具有潜在的营养盐效应,污染控制需要相应的策略. 相似文献
972.
近年来,渤、黄海海域呈现溶解氧浓度降低并导致季节性低氧的特征,对海洋生态环境形成潜在危害。在此背景下,本文基于2011年6月(低氧形成期)和2011年11-12月初(低氧消亡期)在渤、黄海的观测数据,通过分析水体表观耗氧量(AOU)、pH、溶解无机碳(DIC)及营养盐之间的相关关系,探讨了生源要素在低氧形成期与消亡期的变化特征及主要控制机制。结果表明,生物的光合作用与有机物的降解过程是调控低氧事件前后渤海生源要素变化的主要因素之一,而黄海底层水体有机物的降解过程是调控水体溶解氧浓度及营养盐浓度变化的主要原因之一。 相似文献
973.
974.
本文分析了我国当前水污染区域治理的难度,沿海地区水污染的主要问题,探讨了污染区域治理的基本原则,提出了水污染治理的重点区域和水污染区域治理的主要途径,并以浑河流域沈阳地区2000年水污染物总量控制为例,概述总量控制方法和目标 相似文献
975.
陶战 《中国人口.资源与环境》1994,4(1):62-64
中国农业经历了多种策略阶段,可持续发展策略是新近出现的最先进、最适合现在和将来农业发展的策略。新策略带有系统性原理,其实质是发展与生态环境保护协调的农业。因此,可持续发展措施应同时重视解决农业经济发展与生态环境保护两方面的问题。据此,本文提出了六项措施。 相似文献
976.
Daily Bank Erosion Rates in the Lower Yellow River Before and After Dam Construction 总被引:1,自引:0,他引:1
Junqiang Xia Tao Li Xiaojuan Li Xiaolei Zhang Quanli Zong 《Journal of the American Water Resources Association》2014,50(5):1325-1337
During the period of water impoundment and sediment detention of the Sanmenxia Reservoir, riverbank erosion processes played a key role in the channel evolution of the Lower Yellow River (LYR). However, research into bank erosion rates of the LYR has been neglected due to the lack of direct field monitoring. In this study, an indirect method is proposed to determine bank erosion rates at daily time scales by outlining a detailed calculation procedure using measured hydrological data. A total of 810 data points of daily bank erosion rates before and after the construction of Sanmenxia Dam was calculated at seven hydrometric sections along the LYR, with the corresponding values of the bank stability coefficient and the width‐to‐depth ratio also being calculated. Empirical relations were then developed to estimate the daily bank erosion rates, using these parameters at the sections. Temporal and spatial variability in daily bank erosion rates in the LYR before and after dam construction were also investigated, revealing that: (1) the bank erosion rates had a mean value of 16.7‐29.1 m/day in the braided reach, with a maximum value of 290.0 m/day, while they were relatively low in the meandering reach, with a mean value of 2.5 m/day; (2) the erosion rates before dam construction were slightly greater than those after dam construction, with the difference reaching 5‐10 m/day in the braided reach, decreasing in the transitional reach gradually, and being slight in the meandering reach. 相似文献
977.
978.
吴人韦 《生态与农村环境学报》2000,16(1):38-40
简要介绍了国内外旅游规划的发展历程,分析了旅游规划的现状和存在的问题,指出旅游规划的发展趋势是走向合成规划,走向社会实践,走向系统优化和走向可持续发展。 相似文献
979.
G. B. Davis C. Barber T. R. Power J. Thierrin B. M. Patterson J. L. Rayner Qinglong Wu 《Journal of contaminant hydrology》1999,36(3-4)
Data from long-term groundwater sampling, limited coring, and associated studies are synthesised to assess the variability and intrinsic remediation/natural attenuation of a dissolved hydrocarbon plume in sulphate-rich anaerobic groundwater. Fine vertical scale (0.25- and 0.5-m depth intervals) and horizontal plume-scale (>400 m) characteristics of the plume were mapped over a 5-year period from 1991 to 1996. The plume of dissolved BTEX (benzene, toluene, ethylbenzene, xylene) and other organic compounds originated from leakage of gasoline from a subsurface fuel storage tank. The plume was up to 420 m long, less than 50 m wide and 3 m thick. In the first few years of monitoring, BTEX concentrations near the point of leakage were in approximate equilibrium with non-aqueous phase liquid (NAPL) gasoline. NAPL composition of core material and long-term trends in ratios of BTEX concentrations in groundwater indicated significant depletion (water washing, volatilisation and possibly biodegradation) of benzene from residual NAPL after 1992. Large fluctuations in BTEX concentrations in individual boreholes were shown to be largely attributable to seasonal groundwater flow variations. A combination of temporal and spatial groundwater quality data was required to adequately assess the stationarity of plumes, so as to allow inference of intrinsic remediation. Contoured concentration data for the period 1991 to 1996 indicated that plumes of toluene and o-xylene were, at best, only partially steady state (pseudo-steady state) due to seasonal groundwater flow changes. From this analysis, it was inferred that significant remediation by natural biodegradation was occurring for BTEX component plumes such as toluene and o-xylene, but provided no conclusive evidence of benzene biodegradation. Issues associated with field quantification of intrinsic remediation from groundwater sampling are highlighted. Preferential intrinsic biodegradation of selected organic compounds within the BTEX plume was shown to be occurring, in parallel with sulphate reduction and bicarbonate production. Ratios of average hydrocarbon concentrations to benzene for the period 1991 to 1992 were used to estimate degradation rates (half-lives) at various distances along the plume. The estimates varied with distance, the narrowest range being, for toluene, 110 to 260 days. These estimates were comparable to rates determined previously from an in situ tracer test and from plume-scale modelling. 相似文献
980.
滇西北高原由于地处生态脆弱的石灰岩区,水土流失严重,探讨该区生态恢复过程中土壤侵蚀的变化规律,为开展人工植被建设提供依据。以时空互代的方法,通过径流小区,对坡面的产沙产流特性及其影响因素进行研究。结果表明:天然次生林和人工混交林均有较好的调节径流和减少泥沙的作用,产沙量分别比坡耕地减少了51.46%、43.18%,产流量也相应降低了39.39%、24.24%。在最大次降雨条件下,荒草丛、坡耕地、次生林和混交林单次降雨的产沙量分别占试验期产沙总量的55.38%、55.58%、58.35%和58.05%,产流量相应占产流总量的64.72%、64.63%、73.85%和55.39%。而且,产流产沙量与土壤有机质质量分数均存在明显正相关,与乔、灌层植物多样性及均匀度指数等呈显著负相关性(P<0.05)。因此,乔灌草结合的群落结构配置模式是滇西北地区水土保持林营造的目标和方向。 相似文献