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   101285篇
  免费   1250篇
  国内免费   1330篇
安全科学   4015篇
废物处理   3897篇
环保管理   15237篇
综合类   21686篇
基础理论   27823篇
环境理论   74篇
污染及防治   19618篇
评价与监测   6129篇
社会与环境   4728篇
灾害及防治   658篇
  2022年   858篇
  2021年   887篇
  2020年   692篇
  2019年   906篇
  2018年   1382篇
  2017年   1396篇
  2016年   2338篇
  2015年   1882篇
  2014年   2605篇
  2013年   9273篇
  2012年   2745篇
  2011年   3473篇
  2010年   3544篇
  2009年   3694篇
  2008年   3094篇
  2007年   2997篇
  2006年   3056篇
  2005年   2893篇
  2004年   3120篇
  2003年   3054篇
  2002年   2535篇
  2001年   2994篇
  2000年   2362篇
  1999年   1682篇
  1998年   1411篇
  1997年   1414篇
  1996年   1550篇
  1995年   1648篇
  1994年   1533篇
  1993年   1379篇
  1992年   1391篇
  1991年   1349篇
  1990年   1308篇
  1989年   1259篇
  1988年   1097篇
  1987年   1038篇
  1986年   1009篇
  1985年   1083篇
  1984年   1176篇
  1983年   1185篇
  1982年   1182篇
  1981年   1105篇
  1980年   957篇
  1979年   951篇
  1978年   839篇
  1977年   723篇
  1976年   645篇
  1974年   629篇
  1973年   662篇
  1972年   674篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
We examined the impact of stressful job demands on employee attitudes and attendance. Using Karasek's (1979) theory of job decision latitude as the conceptual foundation, we hypothesized that mental and physical work demands would interact with employee beliefs of personal control. Survey data from 90 male manufacturing employees regarding their control beliefs were combined with objective job analysis data concerning mental and physical demands and one year's worth of archival data regarding unexcused absences, sick days, and days tardy. There were significant interactions between control and objective psychological demands that indicated that these demands were associated with higher levels of tardiness and sick days only under conditions of low perceived control. In contrast, subjective workload ratings showed no relationship with tardiness and sick days, but, in interaction with control, predicted work satisfaction and voluntary absence. We discussed these results in terms of a stress process that affects health-related attendance independent of employee attitudes.  相似文献   
162.
163.
Cultural heritage is being addressed by a number of charters and conventions and it is clear that its consideration within decision-making processes is progressively becoming a real challenge, both for developers and public authorities. Against this background, this paper reviews the environmental assessment framework developed by the European Community, as this should increasingly influence decision making about cultural heritage in an urban setting. The legislative framework for access to environmental information is also reviewed because of its relevance to the decision-making process.The Directives on Environmental Impact Assessment and Strategic Environmental Assessment both require a consideration of cultural heritage in decision making. This requirement can go some way to addressing the paradox in the European Community's position whereby the community wishes to conserve and enhance its own cultural identity whilst, at the same time, cultural heritage is usually defined at a local level. The present paper suggests that, given their flexibility, the two European Community directives on environmental assessment constitute a promising opportunity to address this seeming paradox, but that there is a significant gap between legal obligations and the methodological tools to meet them.  相似文献   
164.
Aspects of the trophic attributes of the mudskipper,Periophthalmus barbarus occurring in the mangrove swamps of ImoRiver estuary, Nigeria, were investigated during a 12-month period(April, 1992-March, 1993). Feeding intensity increased with size;it was higher in the dry season (November-April) than in the wetseason (May-October); monthly changes in the indices of feedingintensity were significantly correlated. Major food objectscomprised detritus and benthic algae; crustaceans, insects,macrophyte matter and sand grains were minor food objects whilefish, molluscs, Chilopoda, nematodes and fungi were unconsciouslydevoured objects. Diet varied seasonally; algae and sesarmid crabswere generally more in the dry season than during the rains whereasFPOM and fish increased in the wet over dry season. The mudskipperdisplay a high degree of euryphagy and can be considered as ageneralist and an omnivore. The lower trophic status of P. barbarusqualifies it as a good aquaculture candidate. Food richness washigher in big-sized class (BSC) than small-sized class (SSC).Size-based and seasonal variations were not apparent in foodrichness. Diet breadth was higher in the BSC than the SSC; therewas dry season increase in diet breadth.  相似文献   
165.
Previous researchers have hypothesized that site-faithful animals may benefit from the presence of familiar neighbors. This study compares the relative costs of territorial defense against new and former neighbors by male willow ptarmigan (Lagopus lagopus). Territorial defense against new neighbors appeared to require a greater expenditure of both time and effort than did defense against former neighbors. Territorial males that had several new neighbors spent a higher proportion of time fighting than did males with fewer new neighbors, and males with both new and former neighbors spent a greater amount of time fighting with their new neighbors, on average, than with their former neighbors. In addition, fights with new neighbors occurred relatively more frequently and were longer than fights with former neighbors. Finally, fights involving new neighbors tended to escalate to higher levels than fights between former neighbors. Reduced defensive costs for site-faithful, territorial males may provide one explanation for the tendency of males to be more site-faithful than females in many species.  相似文献   
166.
167.
168.
Studies were conducted to understand 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) behaviour in the near surface zone in relation to the operating conditions: UV-intensity, temperature and exposure modes. Comparisons have been made between Oriel lamp exposure tests and sunlight exposure tests. Under Oriel lamp exposure, the convective transport of TCDD, which depends on operating temperature, was the limiting factor in the cleanup process. The product differences between Oriel exposure tests and sunlight exposure tests probably result from the difference of UV-intensities.  相似文献   
169.
170.
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