全文获取类型
收费全文 | 29660篇 |
免费 | 301篇 |
国内免费 | 195篇 |
专业分类
安全科学 | 765篇 |
废物处理 | 1286篇 |
环保管理 | 3964篇 |
综合类 | 5402篇 |
基础理论 | 7821篇 |
环境理论 | 14篇 |
污染及防治 | 7573篇 |
评价与监测 | 1826篇 |
社会与环境 | 1327篇 |
灾害及防治 | 178篇 |
出版年
2022年 | 198篇 |
2021年 | 214篇 |
2018年 | 359篇 |
2017年 | 357篇 |
2016年 | 585篇 |
2015年 | 443篇 |
2014年 | 659篇 |
2013年 | 2268篇 |
2012年 | 813篇 |
2011年 | 1162篇 |
2010年 | 932篇 |
2009年 | 982篇 |
2008年 | 1164篇 |
2007年 | 1251篇 |
2006年 | 1114篇 |
2005年 | 957篇 |
2004年 | 944篇 |
2003年 | 922篇 |
2002年 | 865篇 |
2001年 | 1100篇 |
2000年 | 817篇 |
1999年 | 490篇 |
1998年 | 340篇 |
1997年 | 370篇 |
1996年 | 362篇 |
1995年 | 454篇 |
1994年 | 416篇 |
1993年 | 378篇 |
1992年 | 371篇 |
1991年 | 397篇 |
1990年 | 387篇 |
1989年 | 375篇 |
1988年 | 362篇 |
1987年 | 330篇 |
1986年 | 285篇 |
1985年 | 282篇 |
1984年 | 358篇 |
1983年 | 318篇 |
1982年 | 368篇 |
1981年 | 298篇 |
1980年 | 261篇 |
1979年 | 286篇 |
1978年 | 253篇 |
1977年 | 221篇 |
1976年 | 188篇 |
1975年 | 215篇 |
1974年 | 238篇 |
1973年 | 220篇 |
1972年 | 200篇 |
1971年 | 190篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
811.
Cara E. Brook James P. Herrera Cortni Borgerson Emma C. Fuller Pascal Andriamahazoarivosoa B. J. Rodolph Rasolofoniaina J. L. Rado Ravoavy Randrianasolo Z. R. Eli Rakotondrafarasata Hervet J. Randriamady Andrew P. Dobson Christopher D. Golden 《Conservation biology》2019,33(1):99-111
Subsistence hunting presents a conservation challenge by which biodiversity preservation must be balanced with safeguarding of human livelihoods. Globally, subsistence hunting threatens primate populations, including Madagascar's endemic lemurs. We used population viability analysis to assess the sustainability of lemur hunting in Makira Natural Park, Madagascar. We identified trends in seasonal hunting of 11 Makira lemur species from household interview data, estimated local lemur densities in populations adjacent to focal villages via transect surveys, and quantified extinction vulnerability for these populations based on species-specific demographic parameters and empirically derived hunting rates. We compared stage-based Lefkovitch with periodic Leslie matrices to evaluate the impact of regional dispersal on persistence trajectories and explored the consequences of perturbations to the timing of peak hunting relative to the lemur birth pulse, under assumptions of density-dependent reproductive compensation. Lemur hunting peaked during the fruit-abundant wet season (March–June). Estimated local lemur densities were roughly inverse to body size across our study area. Life-history modeling indicated that hunting most severely threatened the species with the largest bodies (i.e., Hapalemur occidentalis, Avahi laniger, Daubentonia madagascariensis, and Indri indi), characterized by late-age reproductive onsets and long interbirth intervals. In model simulations, lemur dispersal within a regional metapopulation buffered extinction threats when a majority of local sites supported growth rates above the replacement level but drove regional extirpations when most local sites were overharvested. Hunt simulations were most detrimental when timed to overlap lemur births (a reality for D. madagascariensis and I. indri). In sum, Makira lemurs were overharvested. Regional extirpations, which may contribute to broad-scale extinctions, will be likely if current hunting rates persist. Cessation of anthropogenic lemur harvest is a conservation priority, and development programs are needed to help communities switch from wildlife consumption to domestic protein alternatives. 相似文献
812.
813.
Tohamy Hossam G. Gad El-Karim Dina R. El-Sayed Yasser S. 《Environmental science and pollution research international》2019,26(21):21524-21534
Environmental Science and Pollution Research - Hydroxyurea (HDU), a class of antineoplastic drugs, has a powerful efficacy in the treatment of several types of malignancies. However, it has... 相似文献
814.
Environmental Geochemistry and Health - This study measured both PM10 and surface dust concentrations at roadside in the Central Business District of Baguio City. A total of 66 PM10 filters and 25... 相似文献
815.
816.
Stacey R. Kessler 《组织行为杂志》2019,40(9-10):1046-1054
A definitional component of organizational climate is the focus on employees' shared perceptions of the focal climate domain. To operationalize the notion of sharedness, researchers typically aggregate employees' domain‐specific climate perceptions to a higher level and justify this aggregation using quantitative indices of agreement. In the current paper, I argue that although accounting for sharedness among employees can provide some valuable insight, our overreliance on sharedness obscures some of the very organizational phenomena of interest. I discuss this issue by focusing on four costs of making unfounded assumptions regarding sharedness: (a) Aggregation assumes individual differences are a function of random error; (b) aggregation assumes that social situations are uniform across employees; (c) aggregation assumes that the unit of analysis is clear‐cut; and (d) aggregation assumes the group mean is meaningful. I argue that researchers carefully need to weigh the costs of violating these assumptions against the expected benefits of aggregating employees' climate perceptions, recognizing that sometimes employees' perceptions (i.e., psychological climate) might provide greater insight into phenomena of interest. Although I discuss these costs within the context of organizational climate research, these arguments apply to other research areas where individual perceptions are aggregated (e.g., research on leadership and teams). 相似文献
817.
Prioritizing sites for conservation based on similarity to historical baselines and feasibility of protection 下载免费PDF全文
Traci Popejoy Charles R. Randklev Thomas M. Neeson Caryn C. Vaughn 《Conservation biology》2018,32(5):1118-1127
The concept of shifting baselines in conservation science implies advocacy for the use of historical knowledge to inform these baselines but does not address the feasibility of restoring sites to those baselines. In many regions, conservation feasibility varies among sites due to differences in resource availability, statutory power, and land‐owner participation. We used zooarchaeological records to identify a historical baseline of the freshwater mussel community's composition before Euro‐American influence at a river‐reach scale (i.e., a kilometer stretch of river that is abiotically similar) in the Leon River of central Texas (U.S.A.). We evaluated how the community reference position and the feasibility of conservation might enable identification of sites where conservation actions would preserve historically representative communities and be likely to succeed. We devised a conceptual model that incorporated community information and landscape factors to link the best conservation areas to potential cost and conservation benefits. Using fuzzy ordination, we identified modern mussel beds that were most like the historical baseline. We then quantified housing density and land use near each river reach identified to estimate feasibility of habitat restoration. Using our conceptual framework, we identified reaches of high conservation value (i.e., contain the best mussel beds) and where restoration actions would be most likely to succeed. Reaches above Lake Belton were most similar in species composition and relative abundance to zooarchaeological sites. A subset of these mussel beds occurred in locations where conservation actions appeared most feasible. Our results show how to use zooarchaeological data (biodiversity data often readily available) and estimates of conservation feasibility to inform conservation priorities at a local spatial scale. 相似文献
818.
819.
820.
N.D. Woodman T.C. Rees-White A.M. Stringfellow R.P. Beaven A.P. Hudson 《Waste management (New York, N.Y.)》2014,34(11):2196-2208
The effect of applied compression on the nature of liquid flow and hence the movement of contaminants within municipal solid waste was examined by means of thirteen tracer tests conducted on five separate waste samples. The conservative nature of bromide, lithium and deuterium tracers was evaluated and linked to the presence of degradation in the sample. Lithium and deuterium tracers were non-conservative in the presence of degradation, whereas the bromide remained effectively conservative under all conditions. Solute diffusion times into and out of less mobile blocks of waste were compared for each test under the assumption of dominantly dual-porosity flow. Despite the fact that hydraulic conductivity changed strongly with applied stress, the block diffusion times were found to be much less sensitive to compression. A simple conceptual model, whereby flow is dominated by sub-parallel low permeability obstructions which define predominantly horizontally aligned less mobile zones, is able to explain this result. Compression tends to narrow the gap between the obstructions, but not significantly alter the horizontal length scale. Irrespective of knowledge of the true flow pattern, these results show that simple models of solute flushing from landfill which do not include depth dependent changes in solute transport parameters are justified. 相似文献