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   7478篇
  免费   941篇
  国内免费   1614篇
安全科学   1590篇
废物处理   125篇
环保管理   1045篇
综合类   4200篇
基础理论   1164篇
污染及防治   511篇
评价与监测   329篇
社会与环境   644篇
灾害及防治   425篇
  2024年   63篇
  2023年   186篇
  2022年   340篇
  2021年   380篇
  2020年   368篇
  2019年   298篇
  2018年   250篇
  2017年   376篇
  2016年   384篇
  2015年   409篇
  2014年   343篇
  2013年   414篇
  2012年   607篇
  2011年   666篇
  2010年   517篇
  2009年   559篇
  2008年   396篇
  2007年   462篇
  2006年   473篇
  2005年   332篇
  2004年   259篇
  2003年   245篇
  2002年   249篇
  2001年   186篇
  2000年   189篇
  1999年   149篇
  1998年   147篇
  1997年   123篇
  1996年   104篇
  1995年   97篇
  1994年   82篇
  1993年   67篇
  1992年   58篇
  1991年   31篇
  1990年   25篇
  1989年   28篇
  1988年   22篇
  1987年   18篇
  1986年   17篇
  1985年   10篇
  1984年   8篇
  1983年   4篇
  1981年   14篇
  1980年   16篇
  1979年   14篇
  1978年   9篇
  1974年   5篇
  1972年   4篇
  1971年   12篇
  1970年   5篇
排序方式: 共有10000条查询结果,搜索用时 676 毫秒
471.
The examination of the possible direct link between environmental protection and firm performance in the literature has generally produced mixed results. The present paper contributes to the literature by using the resource-based view as a mediating process in this relationship. The study specifically tests whether or not the resource-based view of the firm mediates the positive relationships of proactive environmental management and improved environmental performance with competitive advantage, which also has consequences for financial performance. We also check the possible link between the adoption of a pioneering approach and good environmental management practices. Our findings support that early investment timing and intensity in environmental issues impact on the adoption of a proactive environmental management, which in turn helps to improve environmental performance. The findings also show that a firm's resources and competitive advantage act as mediator variables for a positive relationship between environmental protection and financial performance. This contribution is original because the present paper develops a comprehensive whole picture of this path process, which has previously only been partially discussed in the literature. In addition, this study clarifies a relevant point in the literature, namely that the effect of environmental protection on firm performance is not direct and can vary depending on the sector considered. Whereas competitive advantage in relation to costs influences financial performance in the IPPC law sector, the relevant influence in the hotel sector comes from competitive advantage through differentiation.  相似文献   
472.
基于“反规划”视角的乡村旅游规划新途径探析   总被引:1,自引:0,他引:1  
引入"反规划"思想,针对传统规划方法给乡村旅游带来的不利影响,强调"反规划"在乡村旅游规划中应用的必要性与可行性。通过与传统规划方法进行对比分析发现,当前乡村旅游规划中存在不少亟待解决的问题。同时,探析了"反规划"思想在乡村旅游规划中的运用,建立乡村旅游"反规划"发展模式为保障乡村旅游可持续性发展提供了理论依据。  相似文献   
473.
随着经济的快速发展,机动车排气污染已成为我国城市空气污染的重要来源,而且在一定时段,机动车排气污染已成为空气污染最主要的污染源之一。以济南市经十路为例,采用实地调查的方法,得出各时段的车流量,选用大气环评助手EIAA中的CALINE4模式对机动车尾气中的主要污染物CO、NOx、THC的排放浓度进行估算,得出3种污染物CO、NOx、THC最大值均出现在7:00—8:00之间,最小值均出现在12:00-13:00之间,排放强度由大到小为:CO、THC、NOx。  相似文献   
474.
本文介绍了煤粉制备系统含尘废气的特性及治理技术的发展与应用,并从袋除尘器类型的确定、处理风量的确定、过滤风速的选取、过滤面积的计算和除尘器规格的选取等方面介绍了煤磨袋除尘器的选型,以及FGM(M)型气箱脉冲防爆袋除尘器、MMC型脉冲喷吹防爆袋除尘器和LPMC型低阻高效防爆袋除尘器在煤粉制备系统除尘中的应用推广情况。  相似文献   
475.
我国现在正处于环境事故高发期,而环境污染损害赔偿是企业,甚至是国家必须面对的现实问题。然而单凭企业承担责任是力所不能及的,最终不得不由国家买单,给国家带来沉重的负担。这种情况迫切需要建立环境污染损害责任保险机制,即绿色保险,把赔偿引向社会化。保险本身就是一种救灾形式,因为它能分散风险,减少损失。针对我国的具体情况,建立适宜的环境污染责任保险模式才能平衡发展与环境保护的关系、在全社会牢固树立生态文明理念。  相似文献   
476.
Abstract: The Soil and Water Assessment Tool (SWAT) model was evaluated for estimation of continuous daily flow based on limited flow measurements in the Upper Oyster Creek (UOC) watershed. SWAT was calibrated against limited measured flow data and then validated. The Nash‐Sutcliffe model Efficiency (NSE) and mean relative error values of daily flow estimations were 0.66 and 15% for calibration, and 0.56 and 4% for validation, respectively. Also, further evaluation of the model’s estimation of flow at multiple locations was conducted with parametric paired t‐test and nonparametric sign test at a 95% confidence level. Among the five main stem stations, four stations were statistically shown to have good agreement between predicted and measured flows. SWAT underestimated the flow of the fifth main stem station possibly because of the existence of complex flood control measures near to the station. SWAT estimated the daily flow at one tributary station well, but with relatively large errors for the other two tributaries. The spatial pattern of predicted flows matched the measured ones well. Overall, it was concluded from the graphical comparisons and statistical analyses of the model results that SWAT was capable of reproducing continuous daily flows based on limited flow data as is the case in the UOC watershed.  相似文献   
477.
Abstract: The hydrologic performance of DRAINMOD 5.1 was assessed for the southern Quebec region considering freezing/thawing conditions. A tile drained agricultural field in the Pike River watershed was instrumented to measure tile drainage volumes. The model was calibrated using water table depth and subsurface flow data over a two‐year period, while another two‐year dataset served to validate the model. DRAINMOD 5.1 accurately simulated the timing and magnitude of subsurface drainage events. The model also simulated the pattern of water table fluctuations with a good degree of accuracy. The R2 between the observed and simulated daily WTD for calibration was >0.78, and that for validation was 0.93. The corresponding coefficients of efficiency (E) were >0.74 and 0.31. The R2 and E values for calibration/validation of subsurface flow were 0.73/0.48 and 0.72/0.40, respectively. DRAINMOD simulated monthly subsurface flow quite accurately (E > 0.82 and R2 > 0.84). The model precisely simulated daily/monthly drain flow over the entire year, including the winter months. Thus DRAINMOD 5.1 performed well in simulating the hydrology of a cold region.  相似文献   
478.
NaCl和KCl对厌氧污泥抑制的动力学研究   总被引:2,自引:0,他引:2  
在厌氧颗粒污泥和厌氧絮状污泥系统中,进行盐质量浓度(NaCl或KCl质量浓度,下同)对厌氧污泥抑制动力学的研究,得到不同拟合的COD降解动力学方程及参数.实验结果表明:当盐质量浓度为10~30 g/L时,KCl对厌氧污泥的COD比降解速率的抑制程度大于NaCl;当盐质量浓度由0 g/L增至10 g/L时,半速率常数逐渐增加;当盐质量浓度由10 g/L增至30 g/L时,半速率常数逐渐减小;在厌氧污泥系统中,NaCl抑制作用下的盐抑制常数高于KCl,且颗粒污泥的盐抑制常数高于絮状污泥.  相似文献   
479.

Introduction

The purpose of this study was to develop an integrated methodology that links occupant injury risk functions, estimated in the laboratory, with real world medical treatment costs by using the abbreviated injury score (AIS). Using our model, the expected medical treatment costs for crash injuries to various body regions and of different severities can be investigated.

Methods

First, the simulation results are compared with NHTSA crash data. We used a modified kinematics simulation model that incorporates an F = Eb function as a supplement to the previous Steffan's model to obtain a more accurate acceleration history a(t). Second, head injury criteria HIC36 can be calculated from a(t), and we use the injury probability P as a function of HIC36, as proposed by Kuppa, to obtain the injury risk function for various AIS values. Third, medical treatment cost models for various AIS values can be calculated by using a regression cost model with real world data. Finally, the injury risk function and medical treatment cost models are linked through AIS values. We establish an integrated methodology and predict medical costs and car safety data using real world police reports, medical treatment costs, and laboratory simulation results.

Results

Using head injuries in frontal crashes as an example, we focus on simulation parameters for different vehicle models, with and without airbags. We specifically examine impact closing speed, Delta-V, and impact directions.

Conclusion

Simulation results can be used to supplement insufficient real crash data, in particular ΔV, and injury risk results from police crash reports.

Impact on industry

The proposed integrated methodology may provide the vehicle industry with a new safety assessment method. Real crash data coupling provides consumers with more realistic and applicable information.  相似文献   
480.
Modeling perceived collision risk in port water navigation   总被引:1,自引:0,他引:1  
An increase in the likelihood of navigational collisions in port waters has put focus on the collision avoidance process in port traffic safety. The most widely used on-board collision-avoidance system is the automatic radar plotting aid which is a passive warning system that triggers an alert based on the pilot’s pre-defined indicators of distance and time proximities at the closest point of approaches in encounters with nearby vessels. To better help pilot in decision making in close quarter situations, collision risk should be considered as a continuous monotonic function of the proximities and risk perception should be considered probabilistically. This paper derives an ordered probit regression model to study perceived collision risks. To illustrate the procedure, the risks perceived by Singapore port pilots were obtained to calibrate the regression model. The results demonstrate that a framework based on the probabilistic risk assessment model can be used to give a better understanding of collision risk and to define a more appropriate level of evasive actions.  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