全文获取类型
收费全文 | 99571篇 |
免费 | 1264篇 |
国内免费 | 1332篇 |
专业分类
安全科学 | 3923篇 |
废物处理 | 3837篇 |
环保管理 | 14727篇 |
综合类 | 22170篇 |
基础理论 | 27693篇 |
环境理论 | 81篇 |
污染及防治 | 18579篇 |
评价与监测 | 6122篇 |
社会与环境 | 4443篇 |
灾害及防治 | 592篇 |
出版年
2022年 | 989篇 |
2021年 | 996篇 |
2020年 | 748篇 |
2019年 | 973篇 |
2018年 | 1473篇 |
2017年 | 1466篇 |
2016年 | 2483篇 |
2015年 | 2001篇 |
2014年 | 2830篇 |
2013年 | 9608篇 |
2012年 | 2743篇 |
2011年 | 3241篇 |
2010年 | 3574篇 |
2009年 | 3679篇 |
2008年 | 2798篇 |
2007年 | 2677篇 |
2006年 | 2821篇 |
2005年 | 2679篇 |
2004年 | 2912篇 |
2003年 | 2814篇 |
2002年 | 2287篇 |
2001年 | 2665篇 |
2000年 | 2205篇 |
1999年 | 1623篇 |
1998年 | 1395篇 |
1997年 | 1395篇 |
1996年 | 1519篇 |
1995年 | 1621篇 |
1994年 | 1510篇 |
1993年 | 1354篇 |
1992年 | 1356篇 |
1991年 | 1308篇 |
1990年 | 1272篇 |
1989年 | 1227篇 |
1988年 | 1052篇 |
1987年 | 1002篇 |
1986年 | 997篇 |
1985年 | 1076篇 |
1984年 | 1163篇 |
1983年 | 1179篇 |
1982年 | 1177篇 |
1981年 | 1097篇 |
1980年 | 953篇 |
1979年 | 923篇 |
1978年 | 826篇 |
1977年 | 712篇 |
1976年 | 639篇 |
1975年 | 607篇 |
1973年 | 630篇 |
1972年 | 644篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media. 相似文献
52.
The occurrence and impact of psychological contract violations were studied among graduate management alumni (N = 128) who were surveyed twice, once at graduation (immediately following recruitment) and then two years later. Psychological contracts, reciprocal obligations in employment developed during and after recruitment, were reported by a majority of respondents (54.8 per cent) as having been violated by their employers. The impact of violations are examined using both quantitative and qualitative data. Occurrence of violations correlated positively with turnover and negatively with trust, satisfaction and intentions to remain. 相似文献
53.
54.
55.
56.
57.
Early non-invasive fetal sexing is widely available over the Internet, leading to concerns about its possible use for sex selection. The aim of this review is to summarise the results of surveys describing lay attitudes towards sex selection for non-medical reasons to help address or inform such concerns. A search of electronic databases and key journals was supplemented by an Internet search and citation-tracking. Twenty-one quantitative studies were identified. Most were conducted in the US, with five recent studies in the UK and Germany. Most studies found that, overall, people were not in favour of sex selection. However, this varied from 94 to 18%. People may hold more negative attitudes when the method of sex selection is specified, particularly if this involves termination of pregnancy (TOP). Attitudes towards the general availability of sex selection are less negative than those towards personal use. Attitudes were consistently negative in German surveys. Little is known of such attitudes outside the US, the UK and Germany, and how such attitudes may change as new sex selection technologies become available. Studies of use of early non-invasive fetal sexing for sex selection for non-medical reasons are needed to assess the extent to which concerns about usage are justified and to assist in debates on how these might be most appropriately addressed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
58.
59.
60.
Critical loads offer a unique way of evaluating impacts of acid deposition by quantifying environmental sensitivity. The critical loads of acidity for UK peat soils have been based upon an arbitrary reduction in pH of 0.2 units. This chemical shift needs to be better related to adverse effects on sensitive biological receptors. It is known that effective precipitation pH equates closely to soil solution pH, and the latter is directly linkable to biotic effects of pH change. On continuation of a long-term experiment assessing impacts of simulated acid rain on peat microcosms in a realistic outdoor environment, Calluna vulgaris continued to flourish at acid deposition loads well above the existing critical load. Calluna plants were harvested and analysed, and acid deposition treatments to the microcosms continued to allow natural vegetation to regenerate. A diverse mixture of moorland plants and bryophytes established at acidity treatments well above the existing critical load, and only a very high acid load resulted in no natural regeneration. A critical effective rain pH value of 3.6 is suggested as a basis for setting critical loads. At this pH, Calluna grows well, and a healthy diverse vegetation community re-establishes when harvested. It is suggested that the peat critical load should be set at the acid load that, at any specific site, would result in a mean effective precipitation pH of 3.6. 相似文献