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   627篇
  免费   13篇
  国内免费   8篇
安全科学   27篇
废物处理   27篇
环保管理   146篇
综合类   52篇
基础理论   151篇
环境理论   1篇
污染及防治   138篇
评价与监测   66篇
社会与环境   25篇
灾害及防治   15篇
  2023年   5篇
  2022年   5篇
  2021年   8篇
  2020年   9篇
  2019年   4篇
  2018年   16篇
  2017年   13篇
  2016年   18篇
  2015年   9篇
  2014年   27篇
  2013年   42篇
  2012年   26篇
  2011年   35篇
  2010年   35篇
  2009年   26篇
  2008年   39篇
  2007年   33篇
  2006年   38篇
  2005年   27篇
  2004年   17篇
  2003年   29篇
  2002年   20篇
  2001年   10篇
  2000年   11篇
  1999年   5篇
  1998年   13篇
  1997年   9篇
  1996年   14篇
  1995年   10篇
  1994年   16篇
  1993年   9篇
  1992年   3篇
  1991年   8篇
  1990年   2篇
  1989年   5篇
  1988年   3篇
  1987年   4篇
  1985年   6篇
  1984年   7篇
  1983年   6篇
  1982年   8篇
  1980年   2篇
  1978年   3篇
  1973年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1966年   1篇
  1964年   1篇
  1936年   1篇
排序方式: 共有648条查询结果,搜索用时 312 毫秒
461.
Infosafe today is a MSDS Management system utilised by many of the world lead ing companies, locally, nationally or globally. The success of Infosafe lies in the system design, which was conceived  相似文献   
462.
ABSTRACT: A critical examination of the techniques used to assess and specify environmental instream flow requirements is provided. The strengths and weaknesses of individual techniques are evaluated on both an absolute and a comparative basis. Particular attention is given to the problem of specifying environmental flow requirements in Australia where the hydrology has distinctly different characteristics to those in countries where most of the models for prediction of instream flow requirements were developed. Broad recommendations as to the suitability and use of the different techniques for different conditions are provided.  相似文献   
463.
This study examined whether an employee's level of absenteeism was affected by age, organizational tenure, perceptions of interactional justice, affective and continuance commitment, and the perceived absence norm in the employees' work unit or department. One hundred and sixty-six nursing and food services employees in a mid-size chronic care hospital provided attitudinal and perceptual data on an employee survey. Absence data (absence frequency and total days absent) were collected during the 12-month period immediately following an employee survey. Hypothesized relations between the various individual- and group-level factors and employee absenteeism were specified in a structural model and tested using LISREL 7 (Joreskog and Sorbom, 1989). General support was found for the study hypotheses.  相似文献   
464.
Against a background of inward investment into the region, the paper examines crucial issues relating to labour. It examines approaches to recruitment and the selection process. Skill shortages and strategies for overcoming the problem are analysed together with a consideration about management and managers. The paper concludes with a detailed assessment of policies relating to training.  相似文献   
465.
ABSTRACT: Soil water potentials, slope throughflow, runoff chemistry, and isotopic composition were monitored in a 97 m2 zero-order basin within the Maimai 8 watershed on the South Island of New Zealand, for a natural rain storm and two artificial water applications. Contrary to results previously reported for other portions of the Maimai catchment, much of the runoff occurred as a shallow subsurface organic layer flow. For the 47 mm natural rain event, pre-storm soil matric potential ranged from ?60 to ?150 cm H2O. No saturation was produced within the profile, and the majority of storm runoff emanated from flow within the organic horizon perched on the mineral soil surface. Hillslope applications corroborated this interpretation by showing >90 percent new water flushing with negligible mineral soil moisture response. Although the mechanisms cited in the text are not representative of the entire catchment, the study demonstrates: (1) the value of a combined physical-chemical-isotopic approach in quantifying slope processes, and (2) the heterogeneous nature and diversity of slope runoff pathways in a relatively homogeneous catchment.  相似文献   
466.
ABSTRACT: Precipitation, throughfall, and stream pH were measured weekly over a 27-week period in 1982 on the Little Millseat watershed in eastern Kentucky. The average pH values over the study period were 4.3, 4.9, and 6.4, respectively, indicating significant buffering as water moved from the atmosphere, through the deciduous canopy, and through or over the soil to the stream. Regression analysis demonstrated that the timing and amount of precipitation were important factors influencing the pH of the throughfall. Weekly precipitation and the three-week average precipitation were statistically significant variables, explaining 53 percent of the variance in the observed through- fall pH. Precipitation pH was not a statistically significant variable for this watershed and sampling period.  相似文献   
467.
ABSTRACT: An experimental investigation of the random component in stream meandering is described. The results of sixty replicate experiments of meander initiation and development made using the same discharge, bed material and bed slope are described and analyzed. It is demonstrated that the commencement of meandering is a random process. The random component in meander behavior is indicated by the size of the coefficients of variation of meander amplitude and wavelength of 0.45 and 0.22, respectively. A simple model is put forward to explain the observed deterministic and random components of meander behavior.  相似文献   
468.
The country estate has a particular place in the English countryside and its contribution to the landscape scene is distinct and valuable. The paper describes an approach to planning a large country estate of parkland, woodland and estate villages in Cheshire. A Reconnaissance Survey led to the Outline Strategy for six ‘landscape types’ discovered on the estate. The Landscape Conservation Plan is described and the crucial importance of conservation measures is emphasised.  相似文献   
469.
To accommodate possible parameter changes in time series at times which are not specified in advance, we propose an adaptive procedure for estimating parameters and for forecasting. The mechanism for activating the adaptive procedure is a successively updated change-detection statistic. The statistic has small expected value when no change is present and has large value when change takes place - the larger the change, the larger the statistic. The statistic defines discounting factors which determine how much of the past will be used both for estimating parameters and for forecasting. The change-detection statistic is designed to effect major changes to parameter estimates and to forecasts in a discrete fashion only, as opposed to certain other adaptive procedures that react continuously to perceived fluctuations in data, and so indicate change even when parameters remain fixed. The procedure is illustrated using exponential smoothing and Holt's linear exponential smoothing and is applied to a hydrological series.  相似文献   
470.
ABSTRACT Methods of institutional coordination derived from the applied behavioral sciences have been useful in determining the policy planning, and implementation responsibilities that must be shared between local governments, watershed districts, and a regional planning body in the Minneapolis-St. Paul Metropolitan Area. The confines of the traditional behavioral science models of organizations and institutional change processes, and the realities of administrative systems imbedded in political processes at both the local and state levels, have created conflicts between regional planners, watershed district staff and consultants, and municipal administrators. A conceptual framework based on work by Selznick on institutions was applied to two watershed districts, and the results evaluated for other research purposes as well as policy development for the 1973 Minnesota legislative session.  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