全文获取类型
收费全文 | 39276篇 |
免费 | 446篇 |
国内免费 | 503篇 |
专业分类
安全科学 | 1012篇 |
废物处理 | 1940篇 |
环保管理 | 5490篇 |
综合类 | 6408篇 |
基础理论 | 10525篇 |
环境理论 | 16篇 |
污染及防治 | 9290篇 |
评价与监测 | 2726篇 |
社会与环境 | 2592篇 |
灾害及防治 | 226篇 |
出版年
2022年 | 270篇 |
2021年 | 272篇 |
2020年 | 274篇 |
2019年 | 255篇 |
2018年 | 1819篇 |
2017年 | 1743篇 |
2016年 | 1788篇 |
2015年 | 671篇 |
2014年 | 748篇 |
2013年 | 2508篇 |
2012年 | 1414篇 |
2011年 | 2591篇 |
2010年 | 1707篇 |
2009年 | 1711篇 |
2008年 | 2097篇 |
2007年 | 2465篇 |
2006年 | 1215篇 |
2005年 | 1036篇 |
2004年 | 1031篇 |
2003年 | 1029篇 |
2002年 | 965篇 |
2001年 | 1098篇 |
2000年 | 848篇 |
1999年 | 521篇 |
1998年 | 395篇 |
1997年 | 386篇 |
1996年 | 400篇 |
1995年 | 447篇 |
1994年 | 385篇 |
1993年 | 384篇 |
1992年 | 361篇 |
1991年 | 361篇 |
1990年 | 354篇 |
1989年 | 328篇 |
1988年 | 282篇 |
1987年 | 243篇 |
1986年 | 285篇 |
1985年 | 280篇 |
1984年 | 325篇 |
1983年 | 302篇 |
1982年 | 301篇 |
1981年 | 287篇 |
1980年 | 256篇 |
1979年 | 265篇 |
1978年 | 185篇 |
1977年 | 195篇 |
1975年 | 158篇 |
1974年 | 178篇 |
1973年 | 160篇 |
1972年 | 187篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
171.
172.
173.
174.
OBJECTIVE: To assess the effects of Washington, D.C. law prohibiting drivers' use of hand-held cell phones on such use. METHODS: Daytime observations of drivers were conducted at signalized intersections in D.C. in March 2004, several months before the law took effect on July 1, 2004, and again in October 2004. As a comparison, observations also were conducted in areas of Virginia and Maryland located close to the D.C. border. Maryland and Virginia placed no limitations on drivers' phone use. Use was observed for 36,091 vehicles in D.C., 25,151 vehicles in Maryland, and 28,483 vehicles in Virginia. RESULTS: The rate of talking on hand-held cell phones among drivers in D.C. declined significantly from 6.1% before the law to 3.5% after. Phone use declined slightly in Maryland and increased significantly in Virginia so that, relative to the patterns of hand-held phone use in the two states, phone use in D.C. declined 50%. Hand-held phone use in D.C. declined comparably among drivers of vehicles registered in all three jurisdictions. D.C. police issued 2,556 citations and 1,232 warnings for cell phone violations during July-November 2004. There were spates of media coverage when the law was passed and when it took effect. CONCLUSIONS: D.C.'s law prohibiting drivers' hand-held phone use had a strong effect on such use among drivers in D.C. Without ongoing publicized enforcement of the law, long-term compliance may be difficult to achieve. 相似文献
175.
INTRODUCTION: Logger safety training programs are rarely, if ever, evaluated as to their effectiveness in reducing injuries. METHOD: Workers' compensation claim rates were used to evaluate the effectiveness of a logger safety training program, the West Virginia Loggers' Safety Initiative (LSI). RESULTS: There was no claim rate decline detected in the majority (67%) of companies that participated in all 4 years of the LSI. Furthermore, their rate did not differ from the rest of the WV logging industry that did not participate in the LSI. Worker turnover was significantly related to claim rates; companies with higher turnover of employees had higher claim rates. Companies using feller bunchers to harvest trees at least part of the time had a significantly lower claim rate than companies not using them. Companies that had more inspections per year had lower claim rates. CONCLUSIONS: High injury rates persist even in companies that receive safety training; high employee turnover may affect the efficacy of training programs. The logging industry should be encouraged to facilitate the mechanization of logging tasks, to address barriers to employee retention, and to increase the number of in-the-field performance monitoring inspections. Impact on industry There are many states whose logger safety programs include only about 4-8 hours of safe work practices training. These states may look to West Virginia's expanded training program (the LSI) as a model for their own programs. However, the LSI training may not be reaching loggers due to the delay in administering training to new employees and high levels of employee turnover. Regardless of training status, loggers' claim rates decline significantly the longer they work for a company. It may be that high injury rates in the state of West Virginia would be best addressed by finding ways to encourage and facilitate companies to become more mechanized in their harvesting practices, and to increase employee tenure. Increasing the number of yearly performance inspections may also be a venue to reduce claim rates. Future research could investigate in better detail the working conditions of West Virginia loggers and identify barriers to job tenure, particularly for workers whose primary job task is chainsaw operation. A larger-scale study of the effect of performance monitoring inspections on claim rates is also warranted. 相似文献
176.
PROBLEM: There is limited information about how parents view teen driving risks and intend to handle these risks during the licensing process, and how they will respond to graduated licensing provisions. METHODS: Parents in Connecticut were interviewed when their teens got their learner's permit. The survey was undertaken when the state did not have a midnight restriction or a passenger restriction. RESULTS: Generally, parents were well aware of teen driving risks, thought parents should be thoroughly involved in the licensing process, and plan to be active participants themselves. DISCUSSION: Parents were concerned about the risk of driving after midnight and already restrict that behavior. However, parents do not seem to see or understand the risks of having even one teen passenger in the vehicle. IMPACT ON INDUSTRY: The views and existing practices of parents need to be taken into account in deciding on the provisions of graduated licensing legislation and how to best ensure acceptance and compliance. 相似文献
177.
Jeffrey H. Kahn Kimberly T. Schneider Theresa M. Jenkins‐Henkelman Laura L. Moyle 《组织行为杂志》2006,27(6):793-807
The authors investigated whether the relationship between the contents of emotional social support and job burnout among high‐school teachers is spurious because of the role of dispositional positive and negative affectivity. A national sample of 339 teachers was surveyed via a web‐based procedure. Hierarchical regression analyses did not support spuriousness; emotional social support was uniquely predictive of three dimensions of burnout controlling for affectivity. As positive emotional social support increased, emotional exhaustion and cynicism decreased, and professional efficacy increased. As negative emotional social support increased, emotional exhaustion and cynicism also increased. Commonality analyses based on the present data and data reported by K. L. Zellars and P. L. Perrewé (2001; Journal of Applied Psychology, 86, 459–467) provided additional support for the unique role of emotional social support on burnout, but these analyses suggest a greater role of affectivity than emotional social support. These findings have implications for research on burnout as well as the prevention of burnout among teachers. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
178.
This study meta‐analyzed the relationships between locus of control (LOC) and a wide range of work outcomes. We categorized these outcomes according to three theoretical perspectives: LOC and well‐being, LOC and motivation, and LOC and behavioral orientation. Hypotheses reflecting these three perspectives were proposed and tested. It was found that internal locus was positively associated with favorable work outcomes, such as positive task and social experiences, and greater job motivation. Our findings are discussed in relation to research on core self‐evaluation and the Big Five personality traits. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
179.
INTRODUCTION: Using data from the NASS General Estimates System (GES), the method of induced exposure was used to assess the effects of electronic stability control (ESC) on loss-of-control type crashes for sport utility vehicles. METHOD: Sport utility vehicles were classified into crash types generally associated with loss of control and crash types most likely not associated with loss of control. Vehicles were then compared as to whether ESC technology was present or absent in the vehicles. A generalized additive model was fit to assess the effects of ESC, driver age, and driver gender on the odds of loss of control. In addition, the effects of ESC on roads that were not dry were compared to effects on roads that were dry. RESULTS: Overall, the estimated percentage reduction in the odds of a loss-of-control crash for sport utility vehicles equipped with ESC was 70.3%. Both genders and all age groups showed reduced odds of loss-of-control crashes, but there was no significant difference between males and females. With respect to driver age, the maximum percentage reduction of 73.6% occurred at age 27. The positive effects of ESC on roads that were not dry were significantly greater than on roads that were dry. 相似文献
180.
This study uses an interactionist approach to examine the moderating effect of follower trait positive affectivity (trait PA) on the relation between transformational leadership and both follower creative performance and organizational citizenship behaviors (OCB). On the basis of responses from 212 employees and their direct supervisors from the research and development department of a company in Mainland China, results support the hypothesized moderation effect. Specifically, the positive influence of transformational leadership on creative performance was significantly reduced for followers who were higher on trait PA (ΔR2 = .02, p < .05). The same pattern, in which followers' trait PA appeared to substitute for the influence of transformational leadership, generalized to the outcome of follower OCB as well (ΔR2 = .04, p < .01). We discussed theoretical and practical implications of these findings. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献