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   20352篇
  免费   292篇
  国内免费   419篇
安全科学   690篇
废物处理   883篇
环保管理   2921篇
综合类   3358篇
基础理论   5516篇
环境理论   7篇
污染及防治   5166篇
评价与监测   1202篇
社会与环境   1193篇
灾害及防治   127篇
  2023年   96篇
  2022年   174篇
  2021年   177篇
  2020年   191篇
  2019年   156篇
  2018年   398篇
  2017年   383篇
  2016年   597篇
  2015年   389篇
  2014年   466篇
  2013年   1448篇
  2012年   1007篇
  2011年   1092篇
  2010年   706篇
  2009年   806篇
  2008年   877篇
  2007年   946篇
  2006年   788篇
  2005年   975篇
  2004年   1125篇
  2003年   954篇
  2002年   582篇
  2001年   681篇
  2000年   538篇
  1999年   343篇
  1998年   214篇
  1997年   239篇
  1996年   226篇
  1995年   279篇
  1994年   215篇
  1993年   211篇
  1992年   178篇
  1991年   192篇
  1990年   182篇
  1989年   187篇
  1988年   155篇
  1987年   133篇
  1986年   158篇
  1985年   143篇
  1984年   190篇
  1983年   147篇
  1982年   172篇
  1981年   158篇
  1980年   130篇
  1979年   149篇
  1978年   94篇
  1977年   100篇
  1975年   88篇
  1974年   95篇
  1972年   98篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
983.
Editorial     
  相似文献   
984.
Objectives: In this study, we sought to accomplish the following objectives: to (1) calculate the percentage of children considered appropriately restrained across 8 criteria of increasing restrictiveness; (2) examine agreement between age- and size-based appropriateness criteria; (3) assess for changes in the percentage of children considered appropriately restrained by the 8 criteria between 2011 (shortly after updates to U.S. guidelines) and 2015.

Methods: Data from 2 cross-sectional surveys of 928 parents of children younger than 12 years old (n = 591 in 2011, n = 337 in 2015) were analyzed in 2017. Child age, weight, and height were measured at an emergency department visit and used to determine whether the parent-reported child passenger restraint was considered appropriate according to 8 criteria. Age-based criteria were derived from Michigan law and U.S. guidelines. Weight, height, and size-based criteria were derived from typical restraints available in the United States in 2007 and 2011. The percentage appropriate restraint use was calculated for each criterion. The kappa statistic was used to measure agreement between criteria. Change in appropriateness from 2011 to 2015 was assessed with chi-square statistics.

Results: Percentage appropriate restraint use varied from a low of 19% for higher weight limits in 2011 to a high of 91% for Michigan law in 2015. Agreement between criteria was slight to moderate. The lowest kappa was for Michigan law and higher weight limits in 2011 (κ = 0.06) and highest for U.S. guidelines and lower weight limits in 2011 (κ = 0.60). Percentage appropriate restraint use was higher in 2015 than 2011 for the following criteria: U.S. guidelines (74 vs. 58%, P < .001), lower weight (57 vs. 47%, P = .005), higher weight (25 vs. 19%, P = .03), greater height (39 vs. 26%, P < .001), and greater size (42 vs. 30%, P = .001).

Conclusions: The percentage of children considered to be using an appropriate restraint varied substantially across criteria. Aligning the definition of appropriate restraint use with current U.S. guidelines would increase consistency in reporting results from studies of child passenger safety in the United States. Potential explanations for the increased percentage of children considered appropriately restrained between 2011 and 2015 include adoption of the updated U.S. guidelines and the use of child passenger restraints with higher weight and height limits.  相似文献   
985.
Objective: This study evaluated the effectiveness of a series of 1-year multifaceted school-based programs aimed at increasing booster seat use among urban children 4–7 years of age in economically disadvantaged areas.

Methods: During 4 consecutive school years, 2011–2015, the Give Kids a Boost (GKB) program was implemented in a total of 8 schools with similar demographics in Dallas County. Observational surveys were conducted at project schools before project implementation (P0), 1–4 weeks after the completion of project implementation (P1), and 4–5 months later (P2). Changes in booster seat use for the 3 time periods were compared for the 8 project and 14 comparison schools that received no intervention using a nonrandomized trial process.

The intervention included (1) train-the-trainer sessions with teachers and parents; (2) presentations about booster seat safety; (3) tailored communication to parents; (4) distribution of fact sheets/resources; (5) walk-around education; and (6) booster seat inspections.

The association between the GKB intervention and proper booster seat use was determined initially using univariate analysis. The association was also estimated using a generalized linear mixed model predicting a binomial outcome (booster seat use) for those aged 4 to 7 years, adjusted for child-level variables (age, sex, race/ethnicity) and car-level variables (vehicle type). The model incorporated the effects of clustering by site and by collection date to account for the possibility of repeated sampling.

Results: In the 8 project schools, booster seat use for children 4–7 years of age increased an average of 20.9 percentage points between P0 and P1 (P0 = 4.8%, P1 = 25.7%; odds ratio [OR] = 6.9; 95% confidence interval [CI], 5.5, 8.7; P < .001) and remained at that level in the P2 time period (P2 = 25.7%; P < .001, for P0 vs. P2) in the univariate analysis. The 14 comparison schools had minimal change in booster seat use. The multivariable model showed that children at the project schools were significantly more likely to be properly restrained in a booster seat after the intervention (OR = 2.7; 95% CI, 2.2, 3.3) compared to the P0 time period and compared to the comparison schools.

Conclusion: Despite study limitations, the GKB program was positively associated with an increase in proper booster seat use for children 4–7 years of age in school settings among diverse populations in economically disadvantaged areas. These increases persisted into the following school year in a majority of the project schools. The GKB model may be a replicable strategy to increase booster seat use among school-age children in similar urban settings.  相似文献   

986.
Interpersonal trust is associated with a range of adaptive outcomes, including knowledge sharing. However, to date, our knowledge of antecedents and consequences of employees feeling trusted by supervisors in organizations remains limited. On the basis of a multisource, multiwave field study among 956 employees from 5 Norwegian organizations, we examined the predictive roles of perceived mastery climate and employee felt trust for employees' knowledge sharing. Drawing on the achievement goal theory, we develop and test a model to demonstrate that when employees perceive a mastery climate, they are more likely to feel trusted by their supervisors at both the individual and group levels. Moreover, the relationship between employees' perceptions of a mastery climate and supervisor‐rated knowledge sharing is mediated by perceptions of being trusted by the supervisor. Theoretical contributions and practical implications of our findings are discussed.  相似文献   
987.
安全生产监管是政府的重要职责,直接关系到国家财产和人民生命安全.安全生产监管中,以危险化学品的监管为重中之重.提高安全生产监管的信息化程度是降低监管强度、提高监管效率行之有效的方法.构建了由管理Agent、采集Agent、故障诊断Agent、通信Agent组成的分布式信息采集多Agent系统,将安监局监管中心对危险化学品生产过程监管的信息采集任务下移到企业端,利用多Agent系统实现危险源生产状态参数的采集、监控及分析;设计了该信息采集系统各类Agent的结构和功能.利用多Agent系统实现分散于各企业的危险源生产状态参数的信息采集、监控及分析,预测和诊断生产过程中的异常状况.通过Agent之间的合作、并行求解使危险化学品安全生产信息采集的问题得到较好地解决.  相似文献   
988.
Objective: Outcomes from previous studies report the driving under the influence (DUI) conviction rates for trauma patients in several cities within Canada and the United States over the last 2 decades. This study reports charge, conviction, and prosecution rates for trauma patients at 2 level I trauma centers servicing a large metropolitan city.

Methods: A retrospective review of the trauma databases was completed to identify patients meeting inclusion criteria. Four hundred sixty patients were identified and their records were compared with the district attorney's records for DUI charges and convictions.

Results: The conviction rate for this study was 8.7%, demonstrating continued low rates of conviction despite growing interest and public awareness of drinking and driving.

Conclusions: We discuss legal considerations that providers should consider when treating patients who have been drinking and driving.  相似文献   

989.

Background

The construction industry is one of the most injury-prone industries, in which production is usually prioritized over safety in daily on-site communication. Workers have an informal and oral culture of risk, in which safety is rarely openly expressed. This paper tests the effect of increasing leader-based on-site verbal safety communication on the level of safety and safety climate at construction sites. Method: A pre-post intervention-control design with five construction work gangs is carried out. Foremen in two intervention groups are coached and given bi-weekly feedback about their daily verbal safety communications with their workers. Foremen-worker verbal safety exchanges (experience sampling method, n = 1,693 interviews), construction site safety level (correct vs. incorrect, n = 22,077 single observations), and safety climate (seven dimensions, n = 105 questionnaires) are measured over a period of up to 42 weeks. Results: Baseline measurements in the two intervention and three control groups reveal that foremen speak with their workers several times a day. Workers perceive safety as part of their verbal communication with their foremen in only 6-16% of exchanges, and the levels of safety at the sites range from 70-87% (correct observations). Measurements from baseline to follow-up in the two intervention groups reveal that safety communication between foremen and workers increases significantly in one of the groups (factor 7.1 increase), and a significant yet smaller increase is found when the two intervention groups are combined (factor 4.6). Significant increases in the level of safety are seen in both intervention groups (7% and 12% increases, respectively), particularly in regards to 'access ways' and 'railings and coverings' (39% and 84% increases, respectively). Increases in safety climate are seen in only one of the intervention groups with respect to their 'attention to safety.' No significant trend changes are seen in the three control groups on any of the three measures. Conclusions: Coaching construction site foremen to include safety in their daily verbal exchanges with workers has a significantly positive and lasting effect on the level of safety, which is a proximal estimate for work-related accidents. It is recommended that future studies include coaching and feedback at all organizational levels and for all involved parties in the construction process. Building client regulations could assign the task of coaching to the client appointed safety coordinators or a manager/supervisor, and studies should measure longitudinal effects of coaching by following foremen and their work gangs from site to site.  相似文献   
990.
噪声是煤矿井下主要危害,对人体视觉系统的影响不容忽视。为了提高暴露在噪声环境中工人的视觉认知能力,进而减少人因事故的发生,针对视觉认知随噪声暴露时间的变化进行研究,利用Eye Link II眼动仪采集被试者的平均注视时间、平均眼跳幅度和眼跳次数3个眼动指标来衡量视觉认知能力随着综采工作面噪声暴露时间的变化。结果表明:1)噪声能够使视觉注意力下降,对视觉认知效率的影响不显著,对视觉辨识能力的影响较复杂;2)噪声在0~10 min和40~55 min时间段对视觉注意力影响较严重,在0~15 min和50~80 min时间段对视觉辨识能力影响较严重;3)被试者随时间变化出现视觉性疲劳后,噪声可轻微提高视觉认知效率和视觉辨识能力。  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