首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2424篇
  免费   105篇
  国内免费   322篇
安全科学   111篇
废物处理   10篇
环保管理   731篇
综合类   1051篇
基础理论   389篇
污染及防治   66篇
评价与监测   96篇
社会与环境   361篇
灾害及防治   36篇
  2024年   19篇
  2023年   33篇
  2022年   62篇
  2021年   66篇
  2020年   74篇
  2019年   77篇
  2018年   71篇
  2017年   110篇
  2016年   104篇
  2015年   111篇
  2014年   99篇
  2013年   150篇
  2012年   119篇
  2011年   189篇
  2010年   135篇
  2009年   131篇
  2008年   127篇
  2007年   175篇
  2006年   148篇
  2005年   118篇
  2004年   97篇
  2003年   111篇
  2002年   72篇
  2001年   51篇
  2000年   51篇
  1999年   46篇
  1998年   24篇
  1997年   26篇
  1996年   26篇
  1995年   15篇
  1994年   17篇
  1993年   12篇
  1992年   11篇
  1991年   9篇
  1990年   12篇
  1989年   13篇
  1988年   10篇
  1987年   9篇
  1986年   7篇
  1985年   9篇
  1984年   8篇
  1983年   10篇
  1981年   15篇
  1980年   16篇
  1979年   13篇
  1978年   6篇
  1977年   8篇
  1975年   9篇
  1972年   4篇
  1971年   5篇
排序方式: 共有2851条查询结果,搜索用时 390 毫秒
271.
黔中石漠化地区不同土地利用方式对土壤环境的影响   总被引:5,自引:0,他引:5  
在贵州省普定县喀斯特石漠化地区通过调查分析,对3种土地不同利用方式(Ⅰ封山育林地、Ⅱ退耕还林地、Ⅲ农耕地)土壤物理性质、化学性质及土壤种子库进行了研究。结果表明利用方式的不同对土壤物理性质、化学性质及土壤种子库均产生了显著的影响。土壤容重、土壤毛管孔隙度随土壤扰动的加剧而下降,表现为Ⅰ>Ⅱ>Ⅲ;土壤总孔隙度与非毛管孔隙度呈现出随土壤扰动程度增加而增加的趋势,表现为Ⅲ>Ⅱ>Ⅰ;不同层次之间容重的变异较小,土壤质地比较均一;Ⅱ土壤有机质低于类型Ⅲ和Ⅰ;Ⅰ初步形成了林地环境,林地土壤表现出良性转变。随土壤深度的增加,有机质、全氮、全磷、速效氮表现出减少的趋势,土壤扰动降低了土壤化学性质层次间变异。不同利用方式下土壤种子库物种组成变化不大,土壤中的种子集中分布在表层0~5 cm内,随土层的加深所含种子数量、物种数逐渐降低。不同利用类型的土壤种子数量在0~5 cm层次差异显著(〖WTBX〗p〖WTBZ〗=0.021 897),种子种类差异不显著(〖WTBX〗p〖WTBZ〗=0.097 628)。土壤扰动促进种子向深层传播,退耕还林有利于土壤质量的恢复。  相似文献   
272.
Delphin JE  Chapot JY 《Chemosphere》2006,64(11):1862-1869
A field experiment was conducted on a Calcaric Cambisol soil to study the consequences of the penetration depth and properties of pesticides on the risk of subsequent leaching. Three pesticides with different mobility characteristics and bromide were injected at 30 cm (where soil organic matter (OM) was 2%) and 80 cm (soil OM 0.5%) on irrigated plots without a crop. The migration of injected solutes was assessed for two years by sampling the soil solution using six porous cups installed at 50 and 150 cm depth and by relating solute contents to drainage water flux estimated by the STICS model (Simulateur mulTIdisciplinaire pour les Cultures Standard). Pesticides injected at 30 cm were strongly retained so that no metolachlor or diuron was detected at 50 and 150 cm. The ratio of atrazine peak concentration in the soil solution to concentration in the injected solution (C/C0) was 1 × 10−3 and 0.2 × 10−3, respectively, at 50 and 150 cm. When injected at 80 cm, (C/C0) of atrazine, metolachlor and diuron were 10 × 10−3, 1 × 10−3 and 0.3 × 10−3 at 150 cm, respectively; 1/(C/C0) was correlated with Koc values reported from databases. The ratio of drainage volume to the amount of water at field capacity in the soil layer between the injection point at 30 cm and the water sampling level (V/V0) at 50 and 150 cm was 0.6 and 0.9, respectively, for bromide and 1.6 and 1.0 for atrazine. V/V0 of the injected solutes at 80 cm was for bromide, atrazine, metolachlor and diuron 0.6, 0.9, 1.2 and 1.7, respectively; pesticide V/V0 was correlated with Koc. The retardation factor was a good indicator of migration risk, but tended to overestimate retardation of molecules with high Koc. Atrazine desorption represented an additional leaching risk as a source of prolonged low contamination. The large variability in soil solution of bromide and pesticide concentrations in the horizontal plane was attributed to flow paths and clods in the tilled soil layer. This heterogeneity was assumed to channel water fluxes into restricted areas and thereby increase the risk of groundwater contamination. The methodology used in the field proves to provide consistent results.  相似文献   
273.
The East Asian economy has been growing fast in recent years, and environmental stresses are building up rapidly. Transboundary air pollution, water shortages, drinking water contamination, freshwater and marine pollution, deforestation, climatic disasters, and other environmental problems are becoming serious threats to the well-being of people in this densely populated region. The ESI (environmental sustainability index) reported by the World Economic Forum in 2005 is a good indicator of the environmental status of the region; most East Asian countries ranked at the bottom. East Asia is not moving toward a sustainable society, and the environment will not sustain the current rate of economic development for long. The traditional culture of East Asia used to be sustainable, so we can learn much from our traditions. Land use should be planned from an ecological point of view so as to best preserve the land’s productivity and stability. There should be definite goals as to where and how much to preserve the three important ecological bases: forests, coastal wetlands and agricultural farms. The forest is the base for the terrestrial ecosystem, including flood control, water resources, and climate; the coastal wetland is the base for the marine ecosystem; farmland is the base for producing food. Within these defined goals, limits should be set on how much land can be utilized for activities like urban development, manufacturing, and recreation. Limits on the pollution load resulting from such activities should be set so as not to irreversibly damage the environment. Economic development should be planned to allow the use of energy and resources only after satisfying these constraints.
Jung Wk KimEmail: Phone: +82-2-8805653Fax: +82-2-8876905
  相似文献   
274.
都市农业生态系统中污水资源化利用   总被引:1,自引:0,他引:1  
文章介绍了都市农业生态系统中的污水处理工艺和资源化利用方案,并对回用过程中的水质状况进行了连续监测与分析,结果表明,主要污染物CODCr、BOD5、浊度、TN的去除率均达到90%以上。再生水完全可以满足系统内农业灌溉的要求,每年可减少50%的地下水开采量,且提供了良好的景观资源。蟹岛生态度假村以生活污水处理为中心的水资源循环利用方式,为污水资源化利用工程作了有益的尝试并取得了良好的效果。  相似文献   
275.
The High Plains aquifer (HPA) is the primary water source for agricultural irrigation in the US Great Plains. The water levels in many locations of the aquifer have declined steadily over the past several decades because the rate of water withdrawals exceeds recharge, which has been a serious concern to the water resources management in the region. We evaluated temporal trends and variations in agricultural water use and hydroclimatic variables including precipitation, air temperature, reference evapotranspiration, runoff, groundwater level, and terrestrial water storage across the HPA region for different periods from 1985 to 2020 at the grid, county, or region scale. The results showed that water withdrawals decreased from 21.3 km3/year in 1985 to 18.2 km3/year in 2015, while irrigated croplands increased from 71,928 km2 in 1985 to 78,464 km2 in 2015 in the entire HPA. The hydroclimatic time-series showed wetting trends in most of the northern HPA, but drying and warming trends in the southern region from 1985 to 2020. The groundwater level time-series indicated flat trends in the north, but significant declining in the central and southern HPA. Trends in irrigation water withdrawals and irrigation area across the HPA were controlled by the advancement of irrigation systems and technologies and the management of sustainable water use, but also were affected by dynamical changes in the hydroclimatic conditions.  相似文献   
276.
Objective: Risky driving behaviors among adolescents, such as riding with a drinking or impaired driver (RWID) or driving while under the influence (DUI) of alcohol or drugs, are significant public health concerns. Few studies have examined associations of RWID and DUI with future substance use and problems after controlling for baseline substance use. Given that the DUI/RWDD event may be a teachable moment to prevent future consequences (e.g., when injured or arrested), it is important to understand how this risk behavior relates to subsequent use and problems. This study therefore examined characteristics of adolescents who reported DUI and RWID and assessed their risk of future alcohol and marijuana use and consequences 6 months later.

Methods: Participants were 668 adolescents aged 12 to 18 (inclusive) recruited at 1 of 4 primary care clinics in Pittsburgh and Los Angeles as part of a larger randomized controlled trial. They completed surveys about their health behaviors at baseline and 6 months after baseline. We examined baseline characteristics of adolescents who reported DUI and RWID and then assessed whether past-year DUI and RWID at baseline were associated with alcohol and marijuana use and consequences 6 months after baseline.

Results: Fifty-eight percent of participants were female, 56% were Hispanic, 23% were Black, 14% were White, 7% were multiethnic or other, and the average age was 16 years (SD?=?1.9). At baseline, participants who reported RWID or DUI were more likely to be older, report past-year use of alcohol and marijuana, and more likely to have an alcohol use disorder or cannabis use disorder versus those who did not report RWID or DUI, respectively. At 6-month follow-up and after controlling for baseline demographics and baseline alcohol use, RWID was associated with more frequent drinking episodes in the past 3 months and greater number of drinks in the past month when they drank heavily. DUI at baseline was associated with more frequent heavy drinking episodes and alcohol and marijuana consequences 6 months later.

Conclusions: RWID and DUI are significantly associated with greater alcohol and marijuana use over time. This study highlights that teens may be at higher risk for problem substance use in the future even if they ride with someone who is impaired. Prevention and intervention efforts for adolescents need to address both driving under the influence and riding with an impaired driver to prevent downstream consequences.  相似文献   
277.
Introduction: Vehicle technologies that increase seat belt use can save thousands of lives each year. Kidd, Singer, Huey, and Kerfoot (2018) found that a gearshift interlock was more effective for increasing seat belt use than an intermittent audible reminder, but interlocks may not be more effective than persistent audible reminders lasting at least 90 seconds. Method: Forty-nine part-time belt users with a recent seat belt citation who self-reported not always using a seat belt drove two vehicles for 1 week each. Thirty-three drove a Chevrolet with an intermittent audible reminder followed by either a BMW with a persistent 90-second audible reminder (n = 17) or a Subaru with an incessant audible reminder (n = 16). The other 16 participants experienced the BMW persistent reminder followed by an interlock that limited speed to 15 mph during unbelted driving. These data were combined with data from 32 part-time belt users in Kidd et al. (2018) who experienced the intermittent reminder for 2 weeks or the intermittent reminder for 1 week and a gearshift interlock the next. Results: Relative to the intermittent reminder, seat belt use was significantly increased an estimated 30% by the BMW persistent reminder, 34% by the Subaru incessant reminder, and 33% by the speed-limiting interlock. Belt use was increased an estimated 16% by the gearshift interlock, but this change was not significant. More participants circumvented the speed-limiting interlock to drive unbelted than the audible reminders. Responses to a poststudy survey indicated that interlocks were less acceptable than reminders. Conclusions: Audible reminders lasting at least 90 seconds and a speed-limiting interlock were more effective for increasing seat belt use than an intermittent audible reminder, but reminders were found more acceptable. Practical applications: Strengthening existing U.S. safety standards to require audible reminders lasting at least 90 seconds for front-row occupants could save up to 1,489 lives annually.  相似文献   
278.
江汉平原湿地功能下降与洪涝灾害关系分析   总被引:6,自引:1,他引:6  
建国以来,江汉平原湿地面积及其生态功能发生了很大的变化,根据史志记载和气候资料,对江汉平原洪涝灾害的发生规律和变化趋势进行了分析,总结出江汉平原洪涝灾害频率趋高、江河湖高水位频率明显增加、外洪内涝日益严重的变化特点。据此,从时间上探讨了湿地变化与洪涝灾害之间的联系,发现历史和近代洪涝灾害的频发期与相应时期的围垦和江堤修筑有较好的对应。结合国土资源部土地变更调查数据分析了近10年来江汉平原湖泊湿地的主要转移途径,从空间上探讨了湿地动态变化与江汉平原洪涝灾害发生之间的内在联系,研究结果表明江汉平原洪涝灾害的发生和湿地面积的减少及其功能的退化之间存在着很好的相关性,从而进一步证实了湿地的围垦和退化是导致其调蓄能力降低,引发洪涝灾害加剧等负页环境效应的一个重要原因。  相似文献   
279.
可持续环境与自然资源发展核算   总被引:6,自引:0,他引:6  
对自然资源耗减价值的核算范围、核算原理、核算方法及环境污染损失价值时间长度的确定进行了论述。为准确的核算绿色GDP,研究资源、环境与经济发展之间的关系,提供了准确的数量依据。  相似文献   
280.
As data sets of multiple types and scales proliferate, it will be increasingly important to be able to flexibly combine them in ways that retain relevant information. A case in point is Amazonia, a large, data-poor region where most whole-basin data sets are limited to understanding land cover interpreted through a variety of remote sensing techniques and sensors. A growing body of work, however, indicates that the future state of much of Amazonia depends on the land use to which converted areas are put, but land use in the tropics is difficult to assess from remotely sensed data alone. An earlier paper developed new snapshots of agricultural land use in this region using a statistical fusion of satellite data and agricultural census data, an underutilized ancillary data source available across Amazonia. The creation of these land-use maps, which have the spatial detail of a satellite image and the attribute information of an agricultural census, required the development of a new statistical technique for merging data sets at different scales and of fundamentally different data types. Here we describe and assess this nonlinear technique, which reinterprets existing land cover classifications by determining what categories are most highly related to the polygon land-use data across the study area. Although developed for this region, the technique appears to hold broad promise for the systematic fusion of multiple data sets that are closely related but of different origins. The figures in the printed version of this article appear in black and white. Color figures are available from the author upon request.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号