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   1362篇
  免费   106篇
  国内免费   224篇
安全科学   284篇
废物处理   5篇
环保管理   157篇
综合类   530篇
基础理论   327篇
环境理论   2篇
污染及防治   62篇
评价与监测   49篇
社会与环境   200篇
灾害及防治   76篇
  2024年   10篇
  2023年   27篇
  2022年   59篇
  2021年   66篇
  2020年   60篇
  2019年   59篇
  2018年   60篇
  2017年   62篇
  2016年   72篇
  2015年   69篇
  2014年   67篇
  2013年   147篇
  2012年   81篇
  2011年   95篇
  2010年   72篇
  2009年   60篇
  2008年   60篇
  2007年   81篇
  2006年   79篇
  2005年   57篇
  2004年   50篇
  2003年   55篇
  2002年   38篇
  2001年   40篇
  2000年   26篇
  1999年   33篇
  1998年   21篇
  1997年   11篇
  1996年   7篇
  1995年   17篇
  1994年   16篇
  1993年   3篇
  1992年   2篇
  1990年   8篇
  1989年   6篇
  1988年   1篇
  1984年   2篇
  1983年   1篇
  1982年   4篇
  1980年   1篇
  1979年   1篇
  1978年   1篇
  1977年   1篇
  1973年   1篇
  1972年   2篇
  1971年   1篇
排序方式: 共有1692条查询结果,搜索用时 15 毫秒
81.
It is widely accepted that the main driver of the observed decline in biological diversity is increasing human pressure on Earth's ecosystems. However, the spatial patterns of change in human pressure and their relation to conservation efforts are less well known. We developed a spatially and temporally explicit map of global change in human pressure over 2 decades between 1990 and 2010 at a resolution of 10 km2. We evaluated 22 spatial data sets representing different components of human pressure and used them to compile a temporal human pressure index (THPI) based on 3 data sets: human population density, land transformation, and electrical power infrastructure. We investigated how the THPI within protected areas was correlated to International Union for Conservation of Nature (IUCN) management categories and the human development index (HDI) and how the THPI was correlated to cumulative pressure on the basis of the original human footprint index. Since the early 1990s, human pressure increased 64% of the terrestrial areas; the largest increases were in Southeast Asia. Protected areas also exhibited overall increases in human pressure, the degree of which varied with location and IUCN management category. Only wilderness areas and natural monuments (management categories Ib and III) exhibited decreases in pressure. Protected areas not assigned any category exhibited the greatest increases. High HDI values correlated with greater reductions in pressure across protected areas, while increasing age of the protected area correlated with increases in pressure. Our analysis is an initial step toward mapping changes in human pressure on the natural world over time. That only 3 data sets could be included in our spatio‐temporal global pressure map highlights the challenge to measuring pressure changes over time. Mapeo del Cambio en la Presión Humana Global en Tierra y Dentro de Áreas Protegidas  相似文献   
82.
A vibrant debate about the future direction of biodiversity conservation centers on the merits of the so‐called new conservation. Proponents of the new conservation advocate a series of positions on key conservation ideas, such as the importance of human‐dominated landscapes and conservation's engagement with capitalism. These have been fiercely contested in a debate dominated by a few high‐profile individuals, and so far there has been no empirical exploration of existing perspectives on these issues among a wider community of conservationists. We used Q methodology to examine empirically perspectives on the new conservation held by attendees at the 2015 International Congress for Conservation Biology (ICCB). Although we identified a consensus on several key issues, 3 distinct positions emerged: in favor of conservation to benefit people but opposed to links with capitalism and corporations, in favor of biocentric approaches but with less emphasis on wilderness protection than prominent opponents of new conservation, and in favor of the published new conservation perspective but with less emphasis on increasing human well‐being as a goal of conservation. Our results revealed differences between the debate on the new conservation in the literature and views held within a wider, but still limited, conservation community and demonstrated the existence of at least one viewpoint (in favor of conservation to benefit people but opposed to links with capitalism and corporations) that is almost absent from the published debate. We hope the fuller understanding we present of the variety of views that exist but have not yet been heard, will improve the quality and tone of debates on the subject.  相似文献   
83.
为了更全面、准确地评价土壤中金属元素对人体的健康风险,研究土壤中金属元素在结肠阶段的生物可给性具有重要意义。通过采集我国一些地区的6种土壤,利用in vitro方法(PBET和SHIME联用)研究土壤中Cu、Zn、Mn在胃、小肠、结肠阶段的生物可给性。研究显示,土壤中Cu、Zn、Mn在胃阶段的生物可给性分别为23.8%~63.0%、21.2%~64.4%、11.7%~35.6%;从胃阶段到小肠阶段,土壤中Cu的生物可给性提高了0.4%~14.4%,而土壤中Zn在小肠阶段的生物可给性降低了6.7%~38.7%。结肠阶段,土壤中Cu、Zn、Mn的生物可给性分别为2.4%~12.9%、5.7%~18.7%、6.2%~18.9%,与小肠阶段相比,分别降低了21.7%~56.9%、0.4%~36.8%、4.5%~19.1%。结果表明,在肠道微生物存在的情况下,土壤中Cu、Zn、Mn在结肠阶段有较低的人体健康风险。  相似文献   
84.
This paper argues on both theoretical and empirical grounds that, beyond a certain point, there is an unavoidable conflictbetween economic development (generally taken to mean 'materialeconomic growth') and environmental protection. Think for a moment of natural forests, grasslands, marine estuaries, salt marshes, and coral reefs; and of arable soils, aquifers, mineraldeposits, petroleum, and coal. These are all forms of 'natural capital' that represent highly-ordered self-producing ecosystemsor rich accumulations of energy/matter with high use potential (low entropy). Now contemplate despoiled landscapes, eroding farmlands, depleted fisheries, anthropogenic greenhouse gases,acid rain, poisonous mine tailings and toxic synthetic compounds.These all represent disordered systems or degraded forms of energy and matter with little use potential (high entropy). The main thing connecting these two states is human economic activity. Ecological economics interprets the environment-economyrelationship in terms of the second law of thermodynamics. The second law sees economic activity as a dissipative process. Fromthis perspective, the production of economic goods andservices invariably requires the consumption of available energy and matter. To grow and develop, the economynecessarily 'feeds' on sources of high-quality energy/matter first produced by nature. This tends to disorder and homogenizethe ecosphere, The ascendance of humankind has consistently been accompanied by an accelerating rate of ecological degradation, particularly biodiversity loss, the simplificationof natural systems and pollution. In short, contemporary political rhetoric to the contrary, the prevailing growth-oriented global development paradigm is fundamentally incompatible with long-term ecological and social sustainability. Unsustainability is not a technical nor economic problem as usually conceived, but rather a state of systemic incompatibilitybetween a economy that is a fully-contained, growing, dependent sub-system of a non-growing ecosphere. Potential solutions fly inthe face of contemporary development trends and cultural values.  相似文献   
85.
Traditionally, decision-makers have relied on economic impactestimates derived from conventional economy-wide models. Conventional models lack the environmental linkages necessary for examining environmental stewardship and economic sustainability, and in particular the ability to assess the impact of policies on natural capital. This study investigatesenvironmentally extended economic impact estimation on a regionalscale using a case study region in the province of Alberta knownas the Foothills Model Forest (FMF). Conventional economic impactmodels are environmentally extended in pursuit of enhancingpolicy analysis and local decision-making. It is found that theflexibility of the computable general equilibrium (CGE) modelingapproach offers potential for environmental extension, with a solid grounding in economic theory. The CGE approach may be the tool of the future for more complete integrated environment andeconomic impact assessment.  相似文献   
86.
Most of the energy conversion in industrial devices and equipment is completed by the motor. The acquirement of motor parameters becomes very important for designing the motor drives. The aim of this paper is to design and implement a motor measurement system. Through the processing of an Advanced RISC Machines (ARM) microcontroller, the various parameters of motors such as input voltage, input current, input power, motor speed, and motor torque can be obtained. Consequently, the torque constant, load torque, viscous friction, and the inertia of the motor are calculated and achieved. The motor parameters can be commanded and displayed in the designed human interface of a PC via USB communication. The hardware system designed in this system includes an ARM microcontroller, an inverter, a voltage sensor, a current sensor, a torque sensor, and power supply. The software programming is developed under the Visual Studio 2012 environment development platform using the C language. Finally, the prototype of the motor measurement system is completed and verified. The experimental results for the motor parameters and torque/speed characteristic are demonstrated and show the feasibility of the complete designed system.  相似文献   
87.
水资源的过度开发导致了水短缺和水生态退化,因此,提供适宜的生态流量对维护河流健康具有重要意义.以往研究聚焦断面尺度的生态流量及其保障程度,尚未有效剥离上游子流域的影响.本研究以松辽流域为研究对象,运用VMF法、Tessmann-adapted法和Smakhtin-adapted法3种水文学法核算二级水资源区生态流量及1...  相似文献   
88.
以大连市1984年-2013年逐年7、8月的日平均温度、相对湿度及平均风速等气象数据为基础,基于模糊综合评价法,对大连市夏季人体舒适度现状进行分析与评价,得到结论如下:用模糊综合评判大连市气候舒适度最适合的评判标准为气温22℃、相对湿度70%和风速2 m/s;大连市总体气候舒适状况良好,夏季相对最舒适的时间段为第6旬(8月20日~8月31日),最不舒适的时间段为第4旬(8月1日~8月10日);由于大连市夏季经常伴有雷阵雨甚至暴雨天气以及湿度大等原因,使得炎热气温所造成的不舒适的天气状况常能得到改善,因此大连市夏季舒适程度所占比例较大。  相似文献   
89.
基于REOF方法的辽宁气候舒适度区域特征分析   总被引:3,自引:0,他引:3  
基于辽宁省50个气象站1964-2008年的气象资料,采用适应东北地区的人体舒适度计算公式及分级标准,得出辽宁省近45年历年人体各舒适度级别日数,使用旋转经验正交分解法(REOF),对辽宁省气候舒适度进行区域划分,并分析了各区域气候舒适度的空间分布特征和变化趋势.结果表明:(1)根据前4个旋转倚载向量场高载荷区分布,将...  相似文献   
90.
耕地土壤的重金属有可能通过食物链网迁移转化危害生态环境和人体健康.目前,人们对兰州市耕地土壤重金属的生态环境和人体健康风险还不够清楚,从而影响对其有效管控.因此,以兰州市耕地表层土壤为研究对象,采用潜在生态风险危害指数评价As、Cd、Cr、Hg和Pb共5种重金属的生态环境风险,以USEPA提出的健康风险模型和推荐的标准评估其人体健康风险,用地理探测器探究风险空间分异的主要影响因子,以便为研究区重金属污染风险的精准管控提供科学依据.结果表明,研究区耕地表层土壤重金属对生态环境风险主要为中风险(65.25%),少部分为低风险(13.80%)和高风险(20.95%),低风险区主要位于永登县东南部、榆中县中部和北部以及皋兰县西南部;中等风险区在三县五区均有分布;高风险区位于永登县北和东南部、城关区南部、七里河东北部、西固区东部和榆中县中部.5种重金属不同暴露途径的非致癌与致癌风险均为:经口摄入>皮肤接触>呼吸摄入,总体上儿童高于成人.但是,"五毒"重金属的非致癌风险HI均小于1,表明它们对当地居民不存在不可接受的非致癌风险.As的致癌风险分别大于1×10-5(儿童2.04×10-5)和小于1×10-4(成人1.91×10-5),说明其对当地居民存在可接受的中等致癌风险,且儿童的大于成人.地理探测器分析表明,采样季平均降水量对As和Cd人体健康风险空间分异的影响最大,GDP对Cr风险空间分异的影响最大,距铁路距离对Hg和Pb风险空间分异的影响最大;交互作用探测表明,各因子之间均为双因子增强,除主导因子起作用外,pH值、坡度和海拔高度等其它因子也会增强主导因子对耕地土壤重金属风险空间分异的影响程度.  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