全文获取类型
收费全文 | 913篇 |
免费 | 15篇 |
国内免费 | 20篇 |
专业分类
安全科学 | 70篇 |
废物处理 | 25篇 |
环保管理 | 183篇 |
综合类 | 139篇 |
基础理论 | 275篇 |
环境理论 | 3篇 |
污染及防治 | 156篇 |
评价与监测 | 59篇 |
社会与环境 | 29篇 |
灾害及防治 | 9篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 13篇 |
2017年 | 31篇 |
2016年 | 36篇 |
2015年 | 24篇 |
2014年 | 25篇 |
2013年 | 64篇 |
2012年 | 28篇 |
2011年 | 50篇 |
2010年 | 31篇 |
2009年 | 39篇 |
2008年 | 56篇 |
2007年 | 44篇 |
2006年 | 47篇 |
2005年 | 36篇 |
2004年 | 25篇 |
2003年 | 33篇 |
2002年 | 28篇 |
2001年 | 22篇 |
2000年 | 19篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 20篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 16篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有948条查询结果,搜索用时 281 毫秒
581.
582.
583.
584.
585.
Susan J. Colarullo Manoutchehr Heidari Thomas Maddock III 《Journal of the American Water Resources Association》1984,20(5):747-760
A groundwater hydraulic management model is used to identify the optimal strategy for allocating limited fresh-water supplies and containing wastes in a hypothetical aquifer affected by brine contamination from surface disposal ponds. The present cost of pumping from a network of potential supply and interception wells is minimized over a five-year planning period, subject to a set of hydraulic, institutional, and legal constraints. Hydraulic constraints are formulated using linear systems theory to describe drawdown and velocity variables as linear functions of supply and interception well discharge decision variables. Successful validation of the optimal management strategy suggests that the model formulation can feasibly be applied to define management options for locally contaminated aquifer systems which are used to fulfill fresh-water demands. 相似文献
586.
587.
In recent years, the unique stress experienced by those who do ‘people work’ has been acknowledged by the helping professions as a widespread problem and has been recognized by social scientists as a topic requiring systematic research. This paper begins by briefly reviewing research on the type of job stress experienced by workers in the helping professions. Then, a study of 142 police couples is reported, illustrating the effects of job stress on family life. In a survey study, police officers and their wives described family interactions. Officers who were experiencing stress, as measured by the Maslach Burnout Inventory, were more likely to display anger, spend time off away from the family, be uninvolved in family matters, and to have unsatisfactory marriages. An examination of the coping patterns used to deal with the stress of police work highlights differences between coping strategies used by husbands versus wives. 相似文献
588.
Composting toilets aim to recycle excrement into safe, stable humus. Preceding this, low costs, low risks, and mass reduction should be ensured. Source separating vermicomposting toilets (SSVCs) outperformed mixed latrine microbial composting toilets (MLMCs) in all categories. MLMCs: incurred ten times greater operational costs; created 10x more operator exposure; employed no proven pathogen reduction mechanism since solid end-products averaged 71,000 ± 230,000 CFU/g (fecal-origin) Escherichia coli and 24 ± 5% total solids, consistently failed NSF/ANSI Standard 41; failed to reduce volatile solids compared to raw fecal matter; increased total contaminated dry mass by 274%, and produced alkaline end-product (8.0 ± 0.7) high in toxic free ammonia (Solvita® 2.6 ± 1.5). SSVCs have low maintenance costs and risks; adequate worm density for pathogen destruction (0.03 ± 0.04 g-worm/g-material); reduced E. coli 200 ± 244 CFU/g in neutral (7.4 ± 0.3), stable (60 ± 10% volatile solids), and mature (4 ± 0 Solvita® NH3) end-product. 相似文献
589.
A fundamental requirement of task regulation in social groups is that it must allow colony flexibility. We tested assumptions
of three task regulation models for how honeybee colonies respond to graded changes in need for a specific task, pollen foraging.
We gradually changed colony pollen stores and measured behavioral and genotypic changes in the foraging population. Colonies
did not respond in a graded manner, but in six of seven cases showed a stepwise change in foraging activity as pollen storage
levels moved beyond a set point. Changes in colony performance resulted from changes in recruitment of new foragers to pollen
collection, rather than from changes in individual foraging effort. Where we were able to track genotypic variation, increases
in pollen foraging were accompanied by a corresponding increase in the genotypic diversity of pollen foragers. Our data support
previous findings that genotypic variation plays an important role in task regulation. However, the stepwise change in colony
behavior suggests that colony foraging flexibility is best explained by an integrated model incorporating genotypic variation
in task choice, but in which colony response is amplified by social interactions.
Received: 17 October 1998 / Received in revised form: 11 March 1999 / Accepted: 12 March 1999 相似文献
590.