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   17666篇
  免费   161篇
  国内免费   77篇
安全科学   483篇
废物处理   658篇
环保管理   2521篇
综合类   2865篇
基础理论   4776篇
环境理论   5篇
污染及防治   4522篇
评价与监测   1071篇
社会与环境   893篇
灾害及防治   110篇
  2023年   114篇
  2022年   141篇
  2021年   146篇
  2020年   140篇
  2019年   205篇
  2018年   245篇
  2017年   252篇
  2016年   394篇
  2015年   280篇
  2014年   405篇
  2013年   1349篇
  2012年   485篇
  2011年   723篇
  2010年   586篇
  2009年   561篇
  2008年   727篇
  2007年   744篇
  2006年   721篇
  2005年   539篇
  2004年   631篇
  2003年   560篇
  2002年   520篇
  2001年   726篇
  2000年   484篇
  1999年   294篇
  1998年   258篇
  1997年   235篇
  1996年   248篇
  1995年   258篇
  1994年   283篇
  1993年   224篇
  1992年   256篇
  1991年   227篇
  1990年   264篇
  1989年   240篇
  1988年   200篇
  1987年   177篇
  1986年   162篇
  1985年   169篇
  1984年   194篇
  1983年   183篇
  1982年   188篇
  1981年   182篇
  1980年   140篇
  1979年   155篇
  1978年   132篇
  1977年   119篇
  1975年   118篇
  1974年   115篇
  1972年   134篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
    
Objective: There has been a longstanding desire for a map to convert International Classification of Diseases (ICD) injury codes to Abbreviated Injury Scale (AIS) codes to reflect the severity of those diagnoses. The Association for the Advancement of Automotive Medicine (AAAM) was tasked by European Union representatives to create a categorical map classifying diagnoses codes as serious injury (Abbreviated Injury Scale [AIS] 3+), minor/moderate injury (AIS 1/2), or indeterminate. This study's objective was to map injury-related ICD-9-CM (clinical modification) and ICD-10-CM codes to these severity categories.

Methods: Approximately 19,000 ICD codes were mapped, including injuries from the following categories: amputations, blood vessel injury, burns, crushing injury, dislocations/sprains/strains, foreign body, fractures, internal organ, nerve/spinal cord injury, intracranial, laceration, open wounds, and superficial injury/contusion. Two parallel activities were completed to create the maps: (1) An in-person expert panel and (2) an electronic survey. The panel consisted of expert users of AIS and ICD from North America, the United Kingdom, and Australia. The panel met in person for 5 days, with follow-up virtual meetings to create and revise the maps. Additional qualitative data were documented to resolve potential discrepancies in mapping. The electronic survey was completed by 95 injury coding professionals from North America, Spain, Australia, and New Zealand over 12 weeks. ICD-to-AIS maps were created for: ICD-9-CM and ICD-10-CM. Both maps indicated whether the corresponding AIS 2005/Update 2008 severity score for each ICD code was AIS 3+, 1/2, or indeterminable. Though some ICD codes could be mapped to multiple AIS codes, the maximum severity of all potentially mapped injuries determined the final severity categorization.

Results: The in-person panel consisted of 13 experts, with 11 Certified AIS specialists (CAISS) with a median of 8 years and an average of 15 years of coding experience. Consensus was reached for AIS severity categorization for all injury-related ICD codes. There were 95 survey respondents, with a median of 8 years of injury coding experience. Approximately 15 survey responses were collected per ICD code. Results from the 2 activities were compared, and any discrepancies were resolved using additional qualitative and quantitative data from the in-person panel and survey results, respectively.

Conclusions: Robust maps of ICD-9-CM and ICD-10-CM injury codes to AIS severity categories (3+ versus <3) were successfully created from an in-person panel discussion and electronic survey. These maps provide a link between the common ICD diagnostic lexicons and the AIS severity coding system and are of value to injury researchers, public health scientists, and epidemiologists using large databases without available AIS coding.  相似文献   
982.
983.
984.
985.
The 2001 National Land Cover Database (NLCD) provides 30-m resolution estimates of percentage tree canopy and percentage impervious cover for the conterminous United States. Previous estimates that compared NLCD tree canopy and impervious cover estimates with photo-interpreted cover estimates within selected counties and places revealed that NLCD underestimates tree and impervious cover. Based on these previous results, a wall-to-wall comprehensive national analysis was conducted to determine if and how NLCD derived estimates of tree and impervious cover varies from photo-interpreted values across the conterminous United States. Results of this analysis reveal that NLCD significantly underestimates tree cover in 64 of the 65 zones used to create the NCLD cover maps, with a national average underestimation of 9.7% (standard error (SE) = 1.0%) and a maximum underestimation of 28.4% in mapping zone 3. Impervious cover was also underestimated in 44 zones with an average underestimation of 1.4% (SE = 0.4%) and a maximum underestimation of 5.7% in mapping zone 56. Understanding the degree of underestimation by mapping zone can lead to better estimates of tree and impervious cover and a better understanding of the potential limitations associated with NLCD cover estimates.  相似文献   
986.
    
We suggest the term ‘hyper-echogenic colon’ to describe a hyperechoic foetal colonic content with no other intestinal abnormality. This is a rare pattern, which to our knowledge, has never been correlated with a specific pathology. The accidental observation of a cystine kidney stone in an infant who presented with this sign during the prenatal period made it possible to diagnose this disease retrospectively in two other children. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
987.
988.
    
In this work we explore the inner time dynamics of 222Rn gaseous emissions of a bubbling mud volcano located in northern Apennines (Italy). In order to discriminate shallow environmental effects, barometric and temperature series have been also monitored and compared with 222Rn data. The Lomb periodogram and the Higuchi techniques have been applied to characterize the time dynamics of the experimental time series. No significant periodicity has been identified and the power spectrum is characterised by a monotonic decrease with frequency f which follows a typical power law (∝f−α). Our findings suggest to consider the 222Rn time series as a realization of an antipersistent stochastic process. This indicates that the dynamics underlying Radon emissions from bubbling mud volcanoes is complex and that a relatively large number of unknown factors control the process. This result discourages the use of bubbling gaseous emissions for the monitoring of geodynamic processes. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
989.
Many alpine ski areas have recently adopted voluntary environmental programs (VEPs) such as using recycling, renewable energy, and biofuels to help reduce their environmental impacts. Studies have addressed the performance of these VEPs in mitigating environmental impacts of this industry, but little is known about visitor awareness and perceptions of these programs. This article addresses this knowledge gap by exploring skier and snowboarder knowledge of VEPs at a ski area and the influence of these programs on their motivations to visit this area currently and behavioral intentions to visit again in the future. Data were obtained from an onsite survey at the Mt. Bachelor ski area in Oregon, USA (n = 429, 89.7% response rate). Few skiers and snowboarders were knowledgeable of VEPs at this area and fewer than 20% were motivated to visit on their current trip because of these programs. Other attributes such as scenery, snow conditions, and access were more important for influencing visitation. Up to 38% of skiers and snowboarders, however, intend to visit this ski area more often if it adopts and promotes more VEPs. Managers can use these results to inform communication and marketing of their environmental programs and performance to visitors. Additional implications for management and future research are discussed.  相似文献   
990.
    
Outlying pollutant concentration data are frequently observed in time series studies conducted to investigate the effects of atmospheric pollution on mortality/morbidity. These outliers may severely affect the estimation procedures and even generate unexpected results like a protective effect of pollution. Although robust methods have been proposed to downweight the effect of outliers in the response variable distribution, little has been done to handle outlying explanatory variable values. We consider a robust local polynomial smoothing technique which may be useful for such purposes. It is based on downweighting points with a small design density and may also be used as a diagnostic tool to identify outliers. Using data from a study conducted in São Paulo, Brazil, we show how an unexpected form of the relative risk curve of mortality attributable to pollution by SO2 obtained via nonrobust methods may be completely reversed when the proposed technique is employed. Copyright © 2004 John Wiley & Sons, Ltd.  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