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   4913篇
  免费   139篇
  国内免费   62篇
安全科学   270篇
废物处理   168篇
环保管理   1245篇
综合类   534篇
基础理论   1349篇
环境理论   8篇
污染及防治   996篇
评价与监测   317篇
社会与环境   172篇
灾害及防治   55篇
  2023年   60篇
  2022年   56篇
  2021年   56篇
  2020年   62篇
  2019年   69篇
  2018年   122篇
  2017年   133篇
  2016年   179篇
  2015年   121篇
  2014年   160篇
  2013年   407篇
  2012年   232篇
  2011年   304篇
  2010年   202篇
  2009年   236篇
  2008年   260篇
  2007年   255篇
  2006年   227篇
  2005年   195篇
  2004年   180篇
  2003年   148篇
  2002年   140篇
  2001年   86篇
  2000年   94篇
  1999年   68篇
  1998年   74篇
  1997年   60篇
  1996年   63篇
  1995年   78篇
  1994年   74篇
  1993年   66篇
  1992年   57篇
  1991年   39篇
  1990年   35篇
  1989年   36篇
  1988年   30篇
  1987年   39篇
  1986年   40篇
  1985年   39篇
  1984年   44篇
  1983年   44篇
  1982年   52篇
  1981年   43篇
  1980年   31篇
  1979年   15篇
  1978年   29篇
  1977年   16篇
  1976年   13篇
  1972年   7篇
  1971年   9篇
排序方式: 共有5114条查询结果,搜索用时 15 毫秒
131.
This paper provides an overview of a collaborative study on visualizing climate change at the local scale. A conceptual framework has been developed, in which local scenarios and visualizations of climate change impacts and response were created to facilitate local dialogue on incorporating climate change into long-term planning and implementation of community development decisions. As part of a larger effort to generate a new integrated participatory visioning process, this paper describes a case study of the District of North Vancouver which created visualizations of changing mountain snow and landscape conditions, and provides new insights on issues and dilemmas in using realistic landscape visualizations to depict scientific modelling projections, local responses to climate change, and uncertainty. Results from this study suggest that the visualizations, and subsequent dialogue sessions, did influence emotional response to climate change as well as self-assessed understanding of adaptation and mitigation response options. However, there is a need to test this visioning process with larger heterogeneous groups of participants in order to better assess its effectiveness in enabling dialogue on local responses to climate change.  相似文献   
132.
How best to optimize the biodiversity gain from agri-environment schemes (AES) has recently been identified as a key policy-relevant question. Here, the effects of two features of lowland agricultural landscapes on the abundance and diversity of larger moths are contrasted. Although both features bring about positive effects, hedgerow trees have a larger impact than 6 m wide grassy field margins. Whilst AES payments are given to create and maintain grass margins, no financial reward is currently offered for the retention of hedgerow trees. Furthermore, it was only in areas where the amount of land under AES was experimentally increased, by targeting farmers, that the presence of hedgerow trees resulted in a substantially higher abundance (+60%) and diversity (+38%) of moths. Thus, by using larger moths as bio-indicators of landscape-scale quality, it is demonstrated that improvements to the cost-effectiveness of AES could be achieved, firstly, by providing more appropriate financial rewards to farmers for different landscape features, and secondly, through landscape-scale targeting of farmers to encourage participation in AES.  相似文献   
133.
Neanderthals disappeared sometime between 30,000 and 24,000?years ago. Until recently, Neanderthals were understood to have been predominantly meat-eaters; however, a growing body of evidence suggests their diet also included plants. We present the results of a study, in which sequential thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) were combined with morphological analysis of plant microfossils, to identify material entrapped in dental calculus from five Neanderthal individuals from the north Spanish site of El Sidrón. Our results provide the first molecular evidence for inhalation of wood-fire smoke and bitumen or oil shale and ingestion of a range of cooked plant foods. We also offer the first evidence for the use of medicinal plants by a Neanderthal individual. The varied use of plants that we have identified suggests that the Neanderthal occupants of El Sidrón had a sophisticated knowledge of their natural surroundings which included the ability to select and use certain plants.  相似文献   
134.
气候确实在发生变化。以往人们随意地认为这与温室效应气体排放量的增加有关,现在这种观点已得到充分证实。自1991年以来.已出现了自有记录以来全球气温最高的十个年份.而在上个世纪,温度上升7约0.6摄氏度。在同一期间内,全球的海平面上升了约20厘米.部分原因是陆地上冰层融化.海洋自身发生热膨胀。许多山峰上的冰盖正在消失.最近几十年来,夏秋季节北冰洋的冰层厚  相似文献   
135.
The sinusoidal fetal heart rate pattern has been described in association with severe fetal anaemia, with fetal hypoxaemia, and with the administration of parenteral narcotics. Here, we report a case of decreased fetal movement in which a sinusoidal tracing was recorded. The sonographic diagnosis of a massive fetal intracranial haemorrhage was made. A non-interventive approach was taken and the fetus died soon after in utero. We review 28 previous cases in which the prenatal sonographic diagnosis of fetal intracranial haemorrhage was made, including the underlying maternal and fetal factors and neonatal outcomes. We propose that the sinusoidal tracing in this case was due to the intracranial bleed and suggest that fetal intracranial haemorrhage be considered in the sonographic evaluation of the fetus with a sinusoidal pattern.  相似文献   
136.

Introduction

Although prior studies of road traffic accidents have found between-group differences in risk, little attention has been given to the encounter between drivers involved in severe collisions.

Method

The present study empirically evaluates two different possible causes of "social accidents," which are defined as collisions between two or more drivers where some faulty social interaction might be assumed, and which are the most prevalent cause of road injuries. The analyses use merged Israeli collision records from 1983 to 2004 with data from two national censuses, thus providing an unprecedented empirical basis to study the social foundations of car accidents. The data are used to adjudicate between two alternative hypotheses: the heterogeneity hypothesis (socially different drivers tend to collide) versus the homogeneity hypothesis (socially similar drivers tend to collide).

Results

Multivariate analyses provide preliminary support for the latter hypothesis. Given an accident, there are more collisions among drivers from the same broad educational group, and the factors that influence this correlation are independent of geography. The paper thus leads to the idea that severe collisions reflect a sociological or ecological process that is akin to acciphilia.

Impact on Industry

The preliminary findings suggest that variation between drivers may be preferable to similarity, since apparently there is a greater tendency toward collisions between similar drivers.  相似文献   
137.
138.
139.
Although malignant transformation of fetal cervical teratoma is extremely rare, perinatal morbidity is high and usually related to the size of the tumour, which may compromise fetal swallowing and subsequently lead to upper airway obstruction. We present a case in which mid-trimester serial sonography demonstrated markedly rapid early growth of a lesion of this type between 17 and 19 weeks' gestation indicating the aggressive nature of this tumour, assisting parental decision to terminate the pregnancy. Histopathology confirmed grade 3 immaturity of the lesion.  相似文献   
140.
This study quantifies the disruption of zooplankton population fluctuations in relation to two magnitudes of fire retardant contamination events using artificial ponds as model systems. Population time series were analysed using redundancy analysis where time was modelled with a principal coordinate of neighborhood matrices approach that identified relevant scales of fluctuation frequencies. Analyses of temporal coherence provided insight whether population fluctuations correlated with system intrinsic or extrinsic forces. Responses to stress were species-specific and context-dependant. Contamination changed temporal structure in some species. These alterations were associated with an increased intrinsic control of dynamics. In some cases the magnitude of impact was unrelated to contamination severity. Some populations were less tolerant of pollution in the low relative to the high concentration treatment. Results suggest that population-level monitoring of degraded sites may be suboptimal because disparate population responses complicate the selection of specific sentinel organisms to monitor stress.  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