全文获取类型
收费全文 | 21640篇 |
免费 | 229篇 |
国内免费 | 242篇 |
专业分类
安全科学 | 662篇 |
废物处理 | 880篇 |
环保管理 | 3034篇 |
综合类 | 4110篇 |
基础理论 | 5610篇 |
环境理论 | 13篇 |
污染及防治 | 5022篇 |
评价与监测 | 1575篇 |
社会与环境 | 1082篇 |
灾害及防治 | 123篇 |
出版年
2023年 | 110篇 |
2022年 | 179篇 |
2021年 | 162篇 |
2020年 | 132篇 |
2019年 | 168篇 |
2018年 | 414篇 |
2017年 | 435篇 |
2016年 | 637篇 |
2015年 | 391篇 |
2014年 | 565篇 |
2013年 | 1437篇 |
2012年 | 1046篇 |
2011年 | 1066篇 |
2010年 | 684篇 |
2009年 | 770篇 |
2008年 | 855篇 |
2007年 | 880篇 |
2006年 | 808篇 |
2005年 | 1029篇 |
2004年 | 1111篇 |
2003年 | 975篇 |
2002年 | 599篇 |
2001年 | 712篇 |
2000年 | 474篇 |
1999年 | 351篇 |
1998年 | 224篇 |
1997年 | 231篇 |
1996年 | 239篇 |
1995年 | 274篇 |
1994年 | 253篇 |
1993年 | 197篇 |
1992年 | 220篇 |
1991年 | 218篇 |
1990年 | 203篇 |
1989年 | 182篇 |
1988年 | 180篇 |
1987年 | 134篇 |
1986年 | 166篇 |
1985年 | 164篇 |
1984年 | 166篇 |
1983年 | 157篇 |
1982年 | 174篇 |
1981年 | 163篇 |
1980年 | 119篇 |
1979年 | 114篇 |
1978年 | 129篇 |
1977年 | 97篇 |
1976年 | 105篇 |
1974年 | 111篇 |
1967年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Geochemical characteristics of surficial sediments in the Panangad region of Cochin estuary, the largest brackish-water humid ecosystem in the south-west coast of India, were analysed. Temporal variations in nutrient stoichiometry, seasonal characteristics of redox elements Fe and S, and the phosphorus geochemistry were employed for the purpose. The stoichiometric analysis pointed towards autochthonous origin of organic matter, possibility of nitrogen limitation, and allochthonous modification of redox conditions. Seasonal variations were not statistically significant for all the geochemical parameters, whereas significant spatial variations were observed with lower values at sandy stations, suggesting that the texture of the sediments is the main factor influencing the sediment geochemistry. Significant inter-relations between the geochemical parameters also suggest a common control mechanism. Based on these geochemical characteristics, the study region can be effectively categorized into two distinct zones, viz. (1) erosion and transportation and (2) deposition zones. 相似文献
52.
53.
54.
55.
Living veligers of the Cassoidea have been observed to use a mantle appendage to form and resorb periostracum. Anatomical and histological examinations of a ranellid (Cymatium sp.) larva collected from the Red Sea in 1987 revealed the structure and location of the pallial appendage. The mantle edges of juvenile or adult species of the Cassoidea do not show a comparable specialization. It is demonstrated that cassoid larval conch characters are sufficient to prove the existence of a pallial appendage without anatomical confirmation. A mantle appendage is not known from teleplanic (long-living planktic) veligers of other gastropod superfamilies. In cases where the larval strategies of the latter are known they are totally different. Therefore it is suggested that the adaptation of cassoid larvae to pelagic life is unique among gastropods representing an autapomorphic character of the superfamily. 相似文献
56.
This paper examines the relationship between survivor reactions to a downsizing and retention subsequent to a downsizing. We hypothesize that survivors who experience the downsizing as distributively, procedurally, and interactionally just and who see top management as trustworthy will feel more attached to the organization because each reduces the threat inherent in downsizing. In addition, we hypothesize that survivors who feel empowered will also feel more attached to the organization because they feel better able to cope with the downsizing. We further hypothesize that those survivors who feel more attached to the organization following the downsizing will be more likely to remain with the organization in the coming year. The theoretical model is tested on a sample of aerospace employees who survived an organizational downsizing. The trustworthiness of management, distributive justice, procedural justice, and three dimensions of empowerment are found to facilitate more organizational attachment. Higher levels of attachment are found, in turn, to facilitate less voluntary turnover in the year following the downsizing. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
57.
58.
David W. Mehlman 《Conservation biology》1994,8(4):1141-1145
59.
In this article the authors assert that successful long-term pollution prevention will require changes in the culture and business practices of an organization such that the term “pollution prevention” eventually becomes obsolete. They envision firms evolving to a point where actions that today are referred to as pollution prevention will simply be part of standard business practices and thoroughly embedded in the firms' culture. Although pollution prevention projects and programs need to be highly visible at the outset to communicate throughout the organization and to demonstrate the benefits that can be gained, companies should adopt a long-term strategy aimed at making fundamental changes in the way they do business, rather than relying solely on piecemeal projects and special plans or programs. Such evolution of the firm will maximize the chances of meeting the dual challenges of business competitiveness and environmental stewardship. This article presents a vision for integrating environmental performance with business objectives and suggests practical steps to begin moving toward that vision. 相似文献
60.