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   1261篇
  免费   20篇
  国内免费   11篇
安全科学   68篇
废物处理   76篇
环保管理   298篇
综合类   171篇
基础理论   221篇
环境理论   2篇
污染及防治   301篇
评价与监测   98篇
社会与环境   40篇
灾害及防治   17篇
  2023年   9篇
  2022年   7篇
  2021年   9篇
  2020年   16篇
  2019年   16篇
  2018年   21篇
  2017年   18篇
  2016年   22篇
  2015年   20篇
  2014年   27篇
  2013年   135篇
  2012年   42篇
  2011年   58篇
  2010年   53篇
  2009年   50篇
  2008年   59篇
  2007年   67篇
  2006年   68篇
  2005年   48篇
  2004年   35篇
  2003年   53篇
  2002年   46篇
  2001年   19篇
  2000年   14篇
  1999年   19篇
  1998年   21篇
  1997年   10篇
  1996年   11篇
  1995年   23篇
  1994年   12篇
  1993年   10篇
  1992年   15篇
  1991年   13篇
  1990年   17篇
  1989年   13篇
  1988年   10篇
  1987年   9篇
  1986年   10篇
  1985年   17篇
  1984年   13篇
  1983年   20篇
  1982年   21篇
  1981年   26篇
  1980年   13篇
  1979年   14篇
  1978年   5篇
  1975年   7篇
  1974年   7篇
  1973年   8篇
  1971年   6篇
排序方式: 共有1292条查询结果,搜索用时 328 毫秒
701.
Assessment of the Antiviral Properties of Zeolites Containing Metal Ions   总被引:1,自引:0,他引:1  
The antiviral properties of zeolite (sodium aluminosilicate) powders amended with metal ions were assessed using human coronavirus 229E, feline infectious peritonitis virus (FIPV), and feline calicivirus F-9. Zeolites containing silver and silver/copper caused significant reductions of coronavirus 229E after 1 h in suspension. The silver/copper combination yielded a >5.13-log10 reduction within 24 h. It was also the most effective (>3.18-log10) against FIPV after 4 h. Other formulations were ineffective against FIPV. On plastic coupons with incorporated silver/copper-zeolites, >1.7-log10 and >3.8-log10 reductions were achieved for coronavirus 229E and feline calicivirus within 24 h, respectively. Silver/copper zeolite reduced titers of all viruses tested, suggesting that it may be effective against related pathogens of interest [i.e., SARS coronavirus, other coronaviruses, human norovirus (calicivirus)]. Of note, it was effective against both enveloped and nonenveloped viruses. Metal-zeolites could therefore possibly be used in applications to reduce virus contamination of fomites and thus the spread of viral diseases.  相似文献   
702.
OBJECTIVE: The objective of the study was to determine which vehicle factors are significantly related to pelvic injury in side impact collisions. Identification of relevant parameters could aid in the reduction of these injuries. METHOD: Side impact crashes from the CIREN database were separated into those in which the occupant sustained a pelvic fracture and those in which no pelvic fracture occurred, although all occupants had serious injuries. A multibody MADYMO model was created of a USDOT SINCAP (U.S. Department of Transportation Side Impact New Car Assessment Program) test of a vehicle with a large center console. RESULTS: From a study of 113 side impact crashes in the ciren database, nearside occupants with pelvic fractures (n = 78) had (i) more door intrusion (mean, 37 vs. 32 cm, p = 0.02) than those who had serious injuries, but not pelvic fractures (ii) a greater likelihood that the lower border of the door intruded more than the upper part (40% vs. 18%, p < 0.025); and (iii) a greater likelihood that their vehicle had a center console (47 vs. 17%, p < 0.005). Other parameters such as occupant age, weight, gender, vehicle weight, and struck vehicle speed change were not significantly different. MADYMO modeling showed that with a center console, an initial positive pelvic acceleration occurred at about 30 msec, followed at about 45 msec by a second acceleration peak in the opposite direction. Reducing console stiffness reduced the second acceleration but not the initial peak. Allowing the seat to translate laterally when contacted by the door reduced the initial pelvic acceleration by 50% and eliminated the second acceleration peak. CONCLUSIONS: Redesigning the center console using less stiff materials and allowing some lateral translation of the seat could aid in reducing pelvic injuries in side impact collisions.  相似文献   
703.
704.
We assess the spatial and geomorphic fragmentation from the recent Eagle Ford Shale play in La Salle County, Texas, USA. Wells and pipelines were overlaid onto base maps of land cover, soil properties, vegetation assemblages, and hydrologic units. Changes to continuity of different ecoregions and supporting landscapes were assessed using the Landscape Fragmentation Tool (a third-party ArcGIS extension) as quantified by land area and continuity of core landscape areas (i.e., those degraded by “edge effects”). Results show decreases in core areas (8.7 %; ~33,290 ha) and increases in landscape patches (0.2 %; ~640 ha), edges (1.8 %; ~6940 ha), and perforated areas (4.2 %; ~16230 ha). Pipeline construction dominates landscape disturbance, followed by drilling and injection pads (85, 15, and 0.03 % of disturbed area, respectively). An increased potential for soil loss is indicated, with 51 % (~5790 ha) of all disturbance regimes occurring on soils with low water-transmission rates (depth to impermeable layer less than 50 cm) and a high surface runoff potential (hydrologic soil group D). Additionally, 88 % (~10,020 ha) of all disturbances occurred on soils with a wind erodibility index of approximately 19 kt/km2/year (0.19 kt/ha/year) or higher, resulting in an estimated potential of 2 million tons of soil loss per year. Results demonstrate that infrastructure placement is occurring on soils susceptible to erosion while reducing and splitting core areas potentially vital to ecosystem services.  相似文献   
705.
Many species are restricted to a marginal or suboptimal fraction of their historical range due to anthropogenic impacts, making it hard to interpret their ecological preferences from modern-day data alone. However, inferring past ecological states is limited by the availability of robust data and biases in historical archives, posing a challenge for policy makers . To highlight how historical records can be used to understand the ecological requirements of threatened species and inform conservation, we investigated sperm whale (Physeter macrocephalus) distribution in the Western Indian Ocean. We assessed differences in information content and habitat suitability predictions based on whale occurrence data from Yankee whaling logs (1792–1912) and from modern cetacean surveys (1995–2020). We built maximum entropy habitat suitability models containing static (bathymetry-derived) variables to compare models comprising historical-only and modern-only data. Using both historical and modern habitat suitability predictions  we assessed marine protected area (MPA) placement by contrasting suitability in- and outside MPAs. The historical model predicted high habitat suitability in shelf and coastal regions near continents and islands, whereas the modern model predicted a less coastal distribution with high habitat suitability more restricted to areas of steep topography. The proportion of high habitat suitability inside versus outside MPAs was higher when applying the historical predictions than the modern predictions, suggesting that different marine spatial planning optimums can be reached from either data sources. Moreover, differences in relative habitat suitability predictions between eras were consistent with the historical depletion of sperm whales from coastal regions, which were easily accessed and targeted by whalers, resulting in a modern distribution limited more to steep continental margins and remote oceanic ridges. The use of historical data can provide important new insights and, through cautious interpretation, inform conservation planning and policy, for example, by identifying refugee species and regions of anticipated population recovery.  相似文献   
706.
707.
Given that self‐efficacy has been shown to be positively related to training outcomes, a better understanding of factors that affect self‐efficacy in complex training contexts is needed. This study examined the development of self‐efficacy in a flight‐training programme. Results indicate that training performance and self‐esteem predicted self‐efficacy for post‐training flight performance. Furthermore, prior flight experience moderated the relationships between training performance and self‐efficacy, and between self‐esteem and self‐efficacy. Implications regarding the development of self‐efficacy and the design of training programmes are discussed. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   
708.

Objectives

The objective was to determine if teenage driving behavior improves when a monitoring and feedback device is installed in the teen's vehicle.

Methods

Vehicles of 85 teenage drivers were fit with a device that detected all instances of sudden braking/acceleration, speeding, and nonuse of seat belts. Drivers were assigned randomly to one of four research groups, differing in whether or not an alert sounded in the vehicle and whether or not parents were given access to websites containing notification records. Time trends in event rates per mile traveled were compared using Poisson regression.

Results

Seat belt use improved when violations were reported to the parent websites, and improved even more when in-vehicle alerts were activated. Consistent reductions in speeding were achieved only when teenagers received alerts about their speeding behavior, believed their speeding behavior would not be reported to parents if corrected, and when parents were being notified of such behavior by report cards.

Conclusions

Electronic monitoring of teenage drivers can reduce the incidence of risky behavior, especially seat belt nonuse. More complicated behavior is more difficult to change, however.

Impact on Industry

Parent participation is key to successful behavioral modification, but it is yet to be determined how best to encourage such participation.  相似文献   
709.
710.
This paper addresses Blau's critique of our early research on behavioral aggregates; we review the theoretical and empirical work on multiple behaviors. We address the definition and measurement of behavioral aggregates, the issue of common method variance, and factors influencing behavior choices. Research from other behavioral areas that uses an approach similar to ours is reviewed as well as relevant research on withdrawal aggregates since 1991. We argue that a focus on general withdrawal constructs rather than individual behaviors will generate significant scientific and practical advantages. The study of constructs will likely provide a basis for generalizations across situations, populations, and time. © 1998 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