全文获取类型
收费全文 | 977篇 |
免费 | 124篇 |
国内免费 | 111篇 |
专业分类
安全科学 | 218篇 |
废物处理 | 6篇 |
环保管理 | 114篇 |
综合类 | 500篇 |
基础理论 | 232篇 |
污染及防治 | 26篇 |
评价与监测 | 31篇 |
社会与环境 | 28篇 |
灾害及防治 | 57篇 |
出版年
2024年 | 6篇 |
2023年 | 24篇 |
2022年 | 38篇 |
2021年 | 53篇 |
2020年 | 44篇 |
2019年 | 35篇 |
2018年 | 21篇 |
2017年 | 29篇 |
2016年 | 34篇 |
2015年 | 47篇 |
2014年 | 39篇 |
2013年 | 42篇 |
2012年 | 59篇 |
2011年 | 76篇 |
2010年 | 67篇 |
2009年 | 55篇 |
2008年 | 51篇 |
2007年 | 63篇 |
2006年 | 76篇 |
2005年 | 52篇 |
2004年 | 44篇 |
2003年 | 38篇 |
2002年 | 38篇 |
2001年 | 39篇 |
2000年 | 43篇 |
1999年 | 13篇 |
1998年 | 14篇 |
1997年 | 16篇 |
1996年 | 4篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1212条查询结果,搜索用时 115 毫秒
71.
水环境质量综合评价的新模型 总被引:23,自引:0,他引:23
为检验已订的水环境质量评价标准的合理性,解决各单项水质指标的评估结果的不相容性问题,提高水质等级模型的分辨率,提出了一种新的水质评价模型-逻辑斯谛曲线(LOG)模型,它的水质等级是连续的实数值;根据LOG模型的参数值可以分析各水质指标值对水质等级的影响程度,从而检验原订水质等级标准的合理性;并给出了基于实码遗传算法的LOG建模的实施方案.实例研究说明,这套方案是实用的和通用的,在其它环境质量综合评价中也具有广泛的应用价值. 相似文献
72.
73.
74.
Biogeographic theory predicts that rare species occur more often in larger, less‐isolated habitat patches and suggests that patch size and connectivity are positive predictors of patch quality for conservation. However, in areas substantially modified by humans, rare species may be relegated to the most isolated patches. We used data from plant surveys of 81 meadow patches in the Georgia Basin of Canada and the United States to show that presence of threatened and endangered plants was positively predicted for patches that were isolated on small islands surrounded by ocean and for patches that were isolated by surrounding forest. Neither patch size nor connectivity were positive predictors of rare species occurrence. Thus, in our study area, human influence, presumably due to disturbance or introduction of competitive non‐native species, appears to have overwhelmed classical predictors of rare species distribution, such that greater patch isolation appeared to favor presence of rare species. We suggest conservation planners consider the potential advantages of protecting geographically isolated patches in human‐modified landscapes because such patches may represent the only habitats in which rare species are likely to persist. Influencia Humana y Predictores Biogeográficos Clásicos de la Ocurrencia de Especies Raras 相似文献
75.
LINDA LAIKRE MIJA JANSSON FRED W. ALLENDORF SVEN JAKOBSSON NILS RYMAN 《Conservation biology》2013,27(2):248-253
The wolf (Canis lupus) is classified as endangered in Sweden by the Swedish Species Information Centre, which is the official authority for threat classification. The present population, which was founded in the early 1980s, descends from 5 individuals. It is isolated and highly inbred, and on average individuals are more related than siblings. Hunts have been used by Swedish authorities during 2010 and 2011 to reduce the population size to its upper tolerable level of 210 wolves. European Union (EU) biodiversity legislation requires all member states to promote a concept called “favourable conservation status” (FCS) for a series of species including the wolf. Swedish national policy stipulates maintenance of viable populations with sufficient levels of genetic variation of all naturally occurring species. Hunting to reduce wolf numbers in Sweden is currently not in line with national and EU policy agreements and will make genetically based FCS criteria less achievable for this species. We suggest that to reach FCS for the wolf in Sweden the following criteria need to be met: (1) a well‐connected, large, subdivided wolf population over Scandinavia, Finland, and the Russian Karelia‐Kola region should be reestablished, (2) genetically effective size (Ne) of this population is in the minimum range of Ne = 500–1000, (3) Sweden harbors a part of this total population that substantially contributes to the total Ne and that is large enough to not be classified as threatened genetically or according to IUCN criteria, and (4) average inbreeding levels in the Swedish population are <0.1. Efectos de la Cacería sobre el Estatus de Conservación Favorable de Lobos Suecos con Endogamia Alta 相似文献
76.
Large (>90%) for gestational age (LGA) fetuses are usually identified incidentally. Detection of the LGA fetus should first prompt the provider to rule out incorrect dates and maternal diabetes. Once this is done, consideration should be given to certain overgrowth syndromes, especially if anomalies are present. The overgrowth syndromes have significant clinical and molecular overlap, and are associated with developmental delay, tumors, and other anomalies. Although genetic causes of overgrowth are considered postnatally, they are infrequently diagnosed prenatally. Here, we review prenatal sonographic findings in fetal overgrowth syndromes, including Pallister-Killian, Beckwith-Wiedemann, Sotos, Perlman, and Simpson-Golabi-Behmel. We also discuss prenatal diagnosis options and recurrence risks. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
77.
78.
Joong Hoon Kim Zong Woo Geem Eung Seok Kim 《Journal of the American Water Resources Association》2001,37(5):1131-1138
ABSTRACT: A newly developed heuristic algorithm, Harmony Search, is applied to the parameter estimation problem of the nonlinear Muskingum model. Harmony Search found better values of parameters in the nonlinear Muskingum model than five other methods including another heuristic method, genetic algorithm, in terms of SSQ (the sum of the square of the deviations between the observed and routed outflows), SAD (the sum of the absolute value of the deviations between the observed and routed outflows), DPO (deviations of peak of routed and actual flows), and DPOT (deviations of peak time of routed and actual outflow). Harmony Search also has the advantage that it does not require the process of assuming the initial values of design parameters. The sensitivity analysis of Harmony Memory Considering Rate showed that relatively large values of Harmony Memory Considering Rate makes the Harmony Search converge to a better solution. 相似文献
79.
LEONARDO A. GALLO†† PAULA MARCHELLI† LUIS CHAUCHARD‡ MARCELO GONZALEZ PEÑALBA§ 《Conservation biology》2009,23(4):895-898
Abstract: Researchers dealing with conservation subjects usually do not put the results of their work into practice, even when the primary purpose of their research is the preservation of biodiversity. In the South American temperate forests we identified an area with the highest genetic diversity in Argentina of Nothofagus nervosa, one of the most relevant southern beech species. Based on the information of our scientific study and our recommendations, the authorities of Lanin National Park changed the protection status of this area to avoid logging. The new forestry management plans include consideration of "high genetic diversity" in decisions on where logging will be allowed. Results of our initial genetic study induced the analysis of biodiversity at the species and ecosystems levels, which yielded results similar to our genetic studies. A strong connection among researchers and managers from the onset of our study and the awareness of the former about the importance of the implementation of the research work were key to bridging the gap between conservation research and conservation practice. 相似文献
80.