全文获取类型
收费全文 | 398篇 |
免费 | 14篇 |
国内免费 | 9篇 |
专业分类
安全科学 | 19篇 |
废物处理 | 17篇 |
环保管理 | 91篇 |
综合类 | 38篇 |
基础理论 | 138篇 |
环境理论 | 1篇 |
污染及防治 | 71篇 |
评价与监测 | 30篇 |
社会与环境 | 16篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 4篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 28篇 |
2012年 | 19篇 |
2011年 | 32篇 |
2010年 | 19篇 |
2009年 | 19篇 |
2008年 | 26篇 |
2007年 | 33篇 |
2006年 | 26篇 |
2005年 | 7篇 |
2004年 | 18篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有421条查询结果,搜索用时 15 毫秒
111.
Charlie M. Shackleton Fiona Parkin Maphambe I. Chauke Linda Downsborough Ashleigh Olsen Gregg Brill Craig Weideman 《Environment, Development and Sustainability》2009,11(2):229-240
Harvesting of non-timber forest products is an integral component of rural livelihoods throughout the developing world. At
times this is at odds with conservation objectives. Reconciliation of the two requires examination of local level contexts
and needs. This paper reports on the harvesting needs for Ischyrolepis by a rural community in South Africa, against the setting that they had recently been prohibited from harvesting by the local
conservation officials. Interviews were conducted with conservation officials to understand the reasoning for the prohibition.
Local demand for Ischyrolepis was assessed by household surveys, as well as in-depth interviews with traders. The density and size class distribution of
Ischyrolepis was determined using transects. The total annual demand for Ischyrolepis was determined to be approximately only 2.7% of the standing crop. The bulk of the annual demand was for small-scale trade,
the income from which was a primary source of income for the few harvesters. Very little evidence could be found indicating
that harvesting was damaging the resource or its habitat, and local knowledge suggested that the abundance of the species
was stimulated by harvesting. Even if market demand were to increase, the size of the shoots required means that less than
20% of the standing crop could be harvested annually. Current regulations around harvesting are in a state of revision, and
hence confusion prevails regarding if harvesting is permissible, and if so, under what conditions, which is detrimental to
both conservation and livelihoods.
Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue. 相似文献
112.
Peter M. Schwarz Craig A. Depken II Alex Hanning Kristen Peterson 《Journal of environmental management》2009,90(12):3730
This study uses California data to compare redevelopment for properties subject to mandatory and voluntary cleanup. CalSites are subject to the CERCLA liability approach, while properties in the Voluntary Cleanup Program (VCP) are subject to a risk-based approach (RBA) that allows some contamination to remain for non-residential redevelopment. The expectation is that VCPs will show a greater proportion of industrial redevelopment, which has the least stringent standard, and a smaller proportion of residential redevelopment. The results show an overall trend toward more residential redevelopment of contaminated properties, but consistent with expectations, the trend is weaker for VCP properties than CalSites. 相似文献
113.
Craig Loehle T. Bently Wigley Erik Schilling Vickie Tatum John Beebe Eric Vance Paul Van Deusen Philip Weatherford 《Environmental management》2009,44(6):1136-1148
Managed forests are a primary land use within the Coastal Plain of the southern United States. These forests are generally
managed under standards, guidelines, or regulations to conserve ecosystem functions and services. Economic value of commercial
forests provides incentives for landowners to maintain forests rather than convert them to other uses that have substantially
reduced environmental benefits. In this review, we describe the historical context of commercial forest management in the
southern United States Coastal Plain, describe how working forests are managed today, and examine relationships between commercial
forest management and maintenance of functional aquatic and wetland systems and conservation of biological diversity. Significant
challenges for the region include increasing human population and urbanization and concomitant changes in forest area and
structure, invasive species, and increased interest in forest biomass as an energy feedstock. Research needs include better
information about management of rare species and communities and quantification of relationships between ecosystem attributes
and forest management, including biomass production and harvest. Incentives and better information may help commercial forest
managers in the Coastal Plain more efficiently contribute to landscape-scale conservation goals. 相似文献
114.
115.
Craig A. Peters 《黑龙江环境通报》2001,21(11):917-923
Fetal models of urinary tract disease have been used for many years and have provided unique and important insights into the pathophysiology of these conditions. This review will summarize the principal model systems used and the current directions of investigation. These models (including rabbit, opossum, sheep and recently swine) have demonstrated that in utero obstruction of the urinary tract alters renal growth, differentiation and produces stereotypical patterns of tissue response, particularly fibrosis. New molecular understanding of these processes has identified specific mechanisms that may be key elements in the development of renal dysfunction due to obstruction. These factors include the renin–angiotensin system (RAS) and its interaction with TGF-β in altering growth regulation and tissue fibrosis. These factors offer the prospect of clinical utility as markers of disease progression as well as pharmacologic therapy. Gene knockout systems have opened a new horizon of molecular models of congenital obstructive uropathy with insights into the role of the RAS in particular. It remains to be defined how closely these knockouts represent the human conditions they resemble. Continued application of fetal models of urinary obstruction, integrating large animal and knockout systems offers promise for improved diagnosis and treatment in these challenging conditions. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
116.
Summary Male sticklebacks (Gasterosteus aculeatus) actively competed for a limited number of clay flowerpots as nest sites in circular wading pools. Males nesting in pots spawned earlier and more often, had higher mean and lower variance for hatching success (number of fry per gram of estimated clutch weight), and suffered fewer stolen fertilizations, nest raids, and territorial encounters than did males nesting outside pots, and in pools without pots (Table 2). Males nesting in pots had the more even temporal distribution of fanning bouts and interfanning intervals; the durations of fanning bouts and interfanning intervals were less variable for these males (Table 2).In replicate aquaria, one male nested on each side of a glass partition and both males spawned approximately simultaneously. Flowerpots were provided to one, both, or neither male. Males with pots had higher mean hatching success, fewer territorial encounters, and the more even temporal distribution of fanning bouts and interfanning intervals (Table 4).Thus it appears that nest site concealment, in the form of clay flowerpots, affected male hatching success, reproductive success, and parental behavior, even when physical contact between males was prevented. These data suggest that a causal relationship may exist between the paternal fanning regime and the subsequent hatching success. Furthermore, these data suggest that males which nest in high concealment increase their reproductive success, and that females which spawn with these males reduce the variance of their hatching success as well as increase their mean hatching success. 相似文献
117.
This paper presents results from field studies carried out during the 1993-1998 Australian cotton (Gossypium hirsutum L.) seasons to monitor off-target droplet movement of endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepin 3-oxide) insecticide applied to a commercial cotton crop. Averaged over a wide range of conditions, off-target deposition 500 m downwind of the field boundary was approximately 2% of the field-applied rate with oil-based applications and 1% with water-based applications. Mean airborne drift values recorded 100 m downwind of a single flight line were a third as much with water-based application compared with oil-based application. Calculations using a Gaussian diffusion model and the U.S. Spray Drift Task Force AgDRIFT model produced downwind drift profiles that compared favorably with experimental data. Both models and data indicate that by adopting large droplet placement (LDP) application methods and incorporating crop buffer distances, spray drift can be effectively managed. 相似文献
118.
The ensemble Kalman Filter (EnKF) applied to a simple fire propagation model by a nonlinear convection-diffusion-reaction
partial differential equation breaks down because the EnKF creates nonphysical ensemble members with large gradients. A modification
of the EnKF is proposed by adding a regularization term that penalizes large gradients. The method is implemented by applying
the EnKF formulas twice, with the regularization term as another observation. The regularization step is also interpreted
as a shrinkage of the prior distribution. Numerical results are given to illustrate success of the new method. 相似文献
119.
120.
Clarifying the role of fire in the deciduous forests of eastern North America: reply to Matlack
下载免费PDF全文
![点击此处可从《Conservation biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)