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   33937篇
  免费   312篇
  国内免费   140篇
安全科学   907篇
废物处理   1355篇
环保管理   4706篇
综合类   6144篇
基础理论   9069篇
环境理论   18篇
污染及防治   8256篇
评价与监测   2046篇
社会与环境   1644篇
灾害及防治   244篇
  2022年   242篇
  2021年   266篇
  2020年   236篇
  2019年   291篇
  2018年   396篇
  2017年   442篇
  2016年   688篇
  2015年   548篇
  2014年   776篇
  2013年   2694篇
  2012年   980篇
  2011年   1341篇
  2010年   1094篇
  2009年   1143篇
  2008年   1315篇
  2007年   1407篇
  2006年   1292篇
  2005年   1064篇
  2004年   1035篇
  2003年   1031篇
  2002年   949篇
  2001年   1178篇
  2000年   902篇
  1999年   539篇
  1998年   423篇
  1997年   439篇
  1996年   454篇
  1995年   502篇
  1994年   474篇
  1993年   455篇
  1992年   452篇
  1991年   436篇
  1990年   443篇
  1989年   408篇
  1988年   372篇
  1987年   347篇
  1986年   346篇
  1985年   328篇
  1984年   369篇
  1983年   354篇
  1982年   379篇
  1981年   348篇
  1980年   304篇
  1979年   321篇
  1978年   267篇
  1977年   248篇
  1974年   244篇
  1973年   230篇
  1972年   231篇
  1971年   214篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
This study examines how attitudes held before attending a computer course differ on the basis of gender, intention to purchase a computer, and computer ownership. Results indicate that gender and ownership are responsible for attitudinal differences, while intent to purchase is not. Further analyses reveal that attitudes differ between learning performance groups. More than all other groups, students who withdrew from the course during the semester and students with the highest performance level in the course perceive computers as increasing job complexity. Ownership eliminated nearly all gender differences in computer attitudes. The implications of these results for managers and future research are discussed.  相似文献   
112.
On November 22, 2006 the largest explosion in the history of Massachusetts occurred in Danvers, MA at approximately 2:46 am. This paper presents a detailed analysis into the potential causes and lessons learned from the Danvers explosion. Other investigative groups concluded that the cause of the explosion was an overheated production tank. However, the analyses presented here demonstrate that their proposed scenario could not have occurred and that other potential causes are more likely.Using the computational fluid dynamics tool FLACS, it was possible to investigate the chain of events leading to the explosion, including: (1) evaluating various leak scenarios by modeling the dispersion and mixing of gases and vapors within the facility, (2) evaluating potential ignition sources within the facility of the flammable fuel–air mixture, and (3) evaluating the explosion itself by comparing the resulting overpressures of the exploding fuel–air cloud with the structural response of the facility and the observed near-field and far-field blast damage. These results, along with key witness statements and other analyses, provide valuable insight into the likely cause of this incident. Based on the results of our detailed analysis, lessons learned regarding the investigative procedure and methods for mitigating this and future explosions are discussed.  相似文献   
113.
114.
115.
The alcohol ignition interlock is an in-vehicle DWI control device that prevents a car from starting until the operator provides a breath alcohol concentration (BAC) test below a set level, usually .02% (20 mg/dl) to .04% (40 mg/dl). The first interlock program was begun as a pilot test in California 18 years ago; today all but a few US states, and Canadian provinces have interlock enabling legislation. Sweden has recently implemented a nationwide interlock program. Other nations of the European Union and as well as several Australian states are testing it on a small scale or through pilot research. This article describes the interlock device and reviews the development and current status of interlock programs including their public safety benefit and the public practice impediments to more widespread adoption of these DWI control devices. Included in this review are (1) a discussion of the technological breakthroughs and certification standards that gave rise to the design features of equipment that is in widespread use today; (2) a commentary on the growing level of adoption of interlocks by governments despite the judicial and legislative practices that prevent more widespread use of them; (3) a brief overview of the extant literature documenting a high degree of interlock efficacy while installed, and the rapid loss of their preventative effect on repeat DWI once they are removed from the vehicles; (4) a discussion of the representativeness of subjects in the current research studies; (5) a discussion of research innovations, including motivational intervention efforts that may extend the controlling effect of the interlock, and data mining research that has uncovered ways to use the stored interlock data record of BAC tests in order to predict high risk drivers; and (6) a discussion of communication barriers and conceptual rigidities that may be preventing the alcohol ignition interlock from taking a more prominent role in the arsenal of tools used to control DWI. Whether interlock programs can help public policymakers achieve their expressed goals of substantially reducing the level of impaired driving will remain uncertain until procedural barriers and intransigent judiciary practices can be overcome that provide for more systematic routine use of interlock programs. Despite strong effectiveness evidence in all studies to date, the real potential of this technology to reduce the road toll cannot be estimated until they are more widely adopted.  相似文献   
116.
Subjective or perceived control over job-related activities or events is a frequently measured construct in organizational stress research. Karasek (1985) assessed perceived control as both decision authority and skill discretion at work (job decision latitude). Ganster (1989b; Dwyer and Ganster, 1991) developed a multidimensional or general measure of worker control, as well as a specific measure of work predictability. Because little published psychometric data exist for these scales, we investigated the item-level measurement properties of Karasek's and Ganster's measures. We hypothesized two separate, two-factor solutions, decision authority and skill discretion, for the job decision latitude scale, and general control and predictability, for the work control scale. The dimensionality of both measures was assessed in multiple, independent samples using confirmatory factor analyses (LISREL) with maximum likelihood estimation. Simultaneous solutions across samples were used to determine the fit of the factor models to the data. The hypothesized two-factor solutions were confirmed for both Karasek's and Ganster's scales, although item refinement is indicated. We also investigated the relative independence between Karasek's and Ganster's scales and found a lack of independence between the general control and decision authority items in one sample. © 1997 John Wiley & Sons, Ltd.  相似文献   
117.
To provide evidence of the relationship between expectations for the values that should be exhibited for effective performance by female and male managers and their actual values, data were used that had been collected as part of a leadership program conducted for managers of business organizations in the United States. From a pool of approximately 700 managers, samples were drawn of 130 male and 130 female managers. As part of leadership program, the managers had completed 26-item SYMLOG value questionnaires, rating themselves and the values they judged to be effective for a manager. Prior to their participation in the program, sets of ratings were made by the coworkers of each manager, rating the actual values of the manager and the coworkers' ideal profile for the manager. The questionnaire covers three dimensions of values: dominant versus submissive, friendly versus unfriendly, and accepting the task-orientation of established authority versus opposing it. Comparisons were made of self and coworkers' ratings on the observed (self/actual) and model (effective/ideal) values of female and male managers with ‘matched’ samples that include only female and male managers with similar ratings of actual values, as judged by their coworkers, by removing the ratings of ‘outliers’. The only significant difference in gender ratings that remains is that female managers rate themselves as more positive. There are more differences between observed and model ratings. Managers and their coworkers believe that model managers should be more dominant and friendly than they are rated to be. However the managers also believe that they should be more task-oriented while their coworkers believe that they should be less task-oriented. The majority of the female managers dropped from the matched sample because no matching male could be found were more dominant and positive and less task-oriented, thus closer to the stereotype role for females. © 1997 John Wiley & Sons, Ltd.  相似文献   
118.
OBJECTIVE: The primary objective of the study was to determine if drinking patterns on the days immediately prior to an alcohol-related motor vehicle crash (ARMVC) were significantly different than drinking patterns in the weeks prior to the crash. METHODS: Following ARMVC, 187 hospitalized non-alcohol dependent young-adults (43 females, 144 males) were enrolled. Mean age was 29.03 years, mean blood alcohol level was 165.18 mg/dL, and mean injury severity score was 10.50. When alcohol-free, subjects were interviewed by nurse clinicians to determine the quantity/frequency of alcohol consumption during the 28 days prior to the crash. Subjects reported the number of standard drinks using the Timeline Followback procedure. Total drinks/day were determined, with day 1 considered 4 weeks prior to the crash and day 28 the day of the crash. A random-intercepts general linear mixed model (GLMM) was used to test the effect of several covariates (segment 1 [days 1-26], segment 2 [days 27-28], age, sex, race, holiday/non-holiday period, driver/passenger status, and weekend/weekday crash) on the amount of standard drinks/day. RESULTS: There was no significant interaction among the covariates. The only significant predictors of drinks/day were segment 2 (b = .322, p < .0001) and gender (b = -.221, p = .016). The positive, statistically significant slope for segment 2 indicated an increase in consumption of drinks/day in the two-day period prior to the ARMVC and the negative slope for gender indicated greater consumption of drinks/day for men than women. CONCLUSION: Persons injured in an ARMVC had a significant increase in alcohol consumption on the day before and the day of vehicular crashes (days 27 and 28) as compared to the first 26 days in the 28-day period preceding the crash. When non-alcohol-dependent subjects are counseled to reduce their risk of traffic crashes, they should be alerted that when their patterns of drinking change, they are at higher risk than usual for a crash.  相似文献   
119.
120.
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