全文获取类型
收费全文 | 20993篇 |
免费 | 258篇 |
国内免费 | 125篇 |
专业分类
安全科学 | 545篇 |
废物处理 | 904篇 |
环保管理 | 2865篇 |
综合类 | 3458篇 |
基础理论 | 5903篇 |
环境理论 | 10篇 |
污染及防治 | 5395篇 |
评价与监测 | 1290篇 |
社会与环境 | 874篇 |
灾害及防治 | 132篇 |
出版年
2021年 | 148篇 |
2019年 | 139篇 |
2018年 | 250篇 |
2017年 | 263篇 |
2016年 | 435篇 |
2015年 | 322篇 |
2014年 | 482篇 |
2013年 | 1635篇 |
2012年 | 597篇 |
2011年 | 840篇 |
2010年 | 687篇 |
2009年 | 672篇 |
2008年 | 854篇 |
2007年 | 875篇 |
2006年 | 779篇 |
2005年 | 674篇 |
2004年 | 662篇 |
2003年 | 641篇 |
2002年 | 625篇 |
2001年 | 777篇 |
2000年 | 578篇 |
1999年 | 327篇 |
1998年 | 263篇 |
1997年 | 281篇 |
1996年 | 279篇 |
1995年 | 333篇 |
1994年 | 302篇 |
1993年 | 285篇 |
1992年 | 280篇 |
1991年 | 280篇 |
1990年 | 297篇 |
1989年 | 278篇 |
1988年 | 250篇 |
1987年 | 242篇 |
1986年 | 225篇 |
1985年 | 200篇 |
1984年 | 257篇 |
1983年 | 210篇 |
1982年 | 274篇 |
1981年 | 221篇 |
1980年 | 187篇 |
1979年 | 204篇 |
1978年 | 185篇 |
1977年 | 153篇 |
1976年 | 139篇 |
1975年 | 143篇 |
1974年 | 160篇 |
1973年 | 162篇 |
1972年 | 148篇 |
1971年 | 146篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
551.
552.
553.
554.
555.
556.
557.
558.
559.
Barbara L. Taylor § Paul R. Wade † Douglas P. De Master ‡ and Jay Barlow 《Conservation biology》2000,14(5):1243-1252
Abstract: Good management models and good models for understanding biology differ in basic philosophy. Management models must facilitate management decisions despite large amounts of uncertainty about the managed populations. Such models must be based on parameters that can be estimated readily, must explicitly account for uncertainty, and should be simple to understand and implement. In contrast, biological models are designed to elucidate the workings of biology and should not be constrained by management concerns. We illustrate the need to incorporate uncertainty in management models by reviewing the inadequacy of using standard biological models to manage marine mammals in the United States. Past management was based on a simple model that, although it may have represented population dynamics adequately, failed as a management tool because the parameter that triggered management action was extremely difficult to estimate for the majority of populations. Uncertainty in parameter estimation resulted in few conservation actions. We describe a recently adopted management scheme that incorporates uncertainty and its resulting implementation. The approach used in this simple management scheme, which was tested by using simulation models, incorporates uncertainty and mandates monitoring abundance and human-caused mortality. Although the entire scheme may be suitable for application to some terrestrial and marine problems, two features are broadly applicable: the incorporation of uncertainty through simulations of management and the use of quantitative management criteria to translate verbal objectives into levels of acceptable risk. 相似文献
560.
Riviane R. Hora Claudie Doums Chantal Poteaux Renée Fénéron Jorge Valenzuela Jürgen Heinze Dominique Fresneau 《Behavioral ecology and sociobiology》2005,59(2):285-292
Social parasites exploit the worker force of colonies of other social insects to rear their own young. Social parasitism occurs in several Hymenoptera and is particularly common in several tribes of the ant subfamilies Myrmicinae and Formicinae. Here, we document the occurrence of miniaturized queens (microgynes) in colonies of Ectatomma tuberculatum, an ant belonging to the subfamily Ectatomminae. Behavioral observations and genetic analyses show that microgynes concentrate their reproductive efforts almost exclusively on the production of sexual offspring (microgynes and males), whereas the regular, large queens (macrogynes) produce workers in addition to sexuals. According to mitochondrial and nuclear markers, gene flow between microgynes and macrogynes is extremely limited. Whereas the co-occurrence of microgynes and macrogynes in the related species Ectatomma ruidum constitutes an intraspecific polymorphism associated with alternative dispersal tactics, microgynes found in colonies of E. tuberculatum appear to be a distinct species and to represent the first case of social parasitism in the poneromorph subfamilies of ants. 相似文献