全文获取类型
收费全文 | 12095篇 |
免费 | 110篇 |
国内免费 | 91篇 |
专业分类
安全科学 | 340篇 |
废物处理 | 453篇 |
环保管理 | 1680篇 |
综合类 | 2137篇 |
基础理论 | 3195篇 |
环境理论 | 7篇 |
污染及防治 | 3000篇 |
评价与监测 | 746篇 |
社会与环境 | 652篇 |
灾害及防治 | 86篇 |
出版年
2022年 | 101篇 |
2021年 | 101篇 |
2020年 | 81篇 |
2019年 | 97篇 |
2018年 | 164篇 |
2017年 | 145篇 |
2016年 | 224篇 |
2015年 | 200篇 |
2014年 | 273篇 |
2013年 | 896篇 |
2012年 | 360篇 |
2011年 | 511篇 |
2010年 | 424篇 |
2009年 | 487篇 |
2008年 | 528篇 |
2007年 | 529篇 |
2006年 | 461篇 |
2005年 | 432篇 |
2004年 | 359篇 |
2003年 | 370篇 |
2002年 | 358篇 |
2001年 | 479篇 |
2000年 | 353篇 |
1999年 | 210篇 |
1998年 | 134篇 |
1997年 | 163篇 |
1996年 | 166篇 |
1995年 | 193篇 |
1994年 | 196篇 |
1993年 | 161篇 |
1992年 | 134篇 |
1991年 | 173篇 |
1990年 | 165篇 |
1989年 | 163篇 |
1988年 | 117篇 |
1987年 | 115篇 |
1986年 | 118篇 |
1985年 | 91篇 |
1984年 | 110篇 |
1983年 | 110篇 |
1982年 | 120篇 |
1981年 | 109篇 |
1980年 | 97篇 |
1979年 | 117篇 |
1978年 | 78篇 |
1977年 | 79篇 |
1975年 | 78篇 |
1973年 | 73篇 |
1972年 | 65篇 |
1967年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
21.
22.
Tanay B. Yıldırım Tutku Ak Zuhal Ölmez 《Environment, Development and Sustainability》2008,10(6):871-881
While the world is going into different tourism expectations, the tourism understanding in Turkey is defined as tourism in the sea-sand-sun triangle. However, it is possible to contribute to the income and local development of the indigenous people by developing nature-based tourism. Besides, with the sustainable use and preservation of the natural-cultural assets, the damage of the traditional tourism industry on the natural and cultural environment could be reduced. In this study, it is aimed to bring up the nature-based tourism concept in Çanakkale by evaluating the nature-based tourism industry in the general of Turkey and assessing the natural-cultural resources that Çanakkale comprehends. The most important areas that have a nature-based tourism potential in Çanakkale and the tourism activities that are most suitable for these areas have been determined. 相似文献
23.
24.
Schaefer CE do Amaral EF de Mendonça BA Oliveira H Lani JL Costa LM Fernandes Filho EI 《Environmental monitoring and assessment》2008,140(1-3):279-289
The relationships between soils attributes, soil carbon stocks and vegetation carbon stocks are poorly know in Amazonia, even
at regional scale. In this paper, we used the large and reliable soil database from Western Amazonia obtained from the RADAMBRASIL
project and recent estimates of vegetation biomass to investigate some environmental relationships, quantifying C stocks of
intact ecosystem in Western Amazonia. The results allowed separating the western Amazonia into 6 sectors, called pedo-zones:
Roraima, Rio Negro Basin, Tertiary Plateaux of the Amazon, Javari-Juruá-Purus lowland, Acre Basin and Rondonia uplands. The
highest C stock for the whole soil is observed in the Acre and in the Rio Negro sectors. In the former, this is due to the
high nutrient status and high clay activity, whereas in the latter, it is attributed to a downward carbon movement attributed
to widespread podzolization and arenization, forming spodic horizons. The youthful nature of shallow soils of the Javari-Juruá-Purus
lowlands, associated with high Al, results in a high phytomass C/soil C ratio. A similar trend was observed for the shallow
soils from the Roraima and Rondonia highlands. A consistent east–west decline in biomass carbon in the Rio Negro Basin sector
is associated with increasing rainfall and higher sand amounts. It is related to lesser C protection and greater C loss of
sandy soils, subjected to active chemical leaching and widespread podzolization. Also, these soils possess lower cation exchangeable
capacity and lower water retention capacity. Zones where deeply weathered Latosols dominate have a overall pattern of high
C sequestration, and greater than the shallower soils from the upper Amazon, west of Madeira and Negro rivers. This was attributed
to deeper incorporation of carbon in these clayey and highly pedo-bioturbated soils. The results highlight the urgent need
for refining soil data at an appropriate scale for C stocks calculations purposes in Amazonia. There is a risk of misinterpreting
C stocks in Amazonia when such great pedological variability is not taken into account. 相似文献
25.
A study was conducted in central Texas to determine the potential of using remote sensing technology to distinguish Ashe juniper (Juniperus ashei Buchholz) infestations on rangelands. Plant canopy reflectance measurements showed that Ashe juniper had lower near-infrared reflectance than other associated woody plant species and lower visible reflectance than mixed herbaceous species in spring and summer. Ashe juniper could be distinguished on color-infrared aerial photographs acquired in March, April, June, and August and on QuickBird false color satellite imagery obtained in June, where it had a distinct dark reddish-brown tonal response. Unsupervised classification techniques were used to classify aerial photographic and satellite imagery of study sites. An accuracy assessment performed on a computer classified map of a photographic image showed that Ashe juniper had producer's and user's accuracies of 100% and 92.9%, respectively, whereas an accuracy assessment performed on a classified map of a satellite image of the same site showed that Ashe juniper had producer's and user's accuracies of 94.1% and 88.1%, respectively. Accuracy assessments performed on classified maps of satellite images of two additional study sites showed that Ashe juniper had producer's and user's accuracies that ranged from 87.1% to 96.4%. These results indicate that both color-infrared photography and false color satellite imagery can be used successfully for distinguishing Ashe juniper infestations. 相似文献
26.
27.
28.
Certain hydrothermal vent invertebrates, e.g. Riftia pachyptila and Calyptogena magnifica, are clearly established as harboring dense populations of chemoautotrophic sulfur bacteria in specialized tissues. By contrast, the physiological characteristics of the abundant intracellular gill symbiont of the vent mussel Bathymodiolus thermophilus have been questioned. The low activities of enzymes diagnostic for CO2 fixation (Calvin cycle) and for sulfur-driven energy generation, as measured by other investigators, have been attributed to bacterial contamination of the gill surface. Based on research at the Galápagos Rift hydrothermal vents in 1988 and subsequent laboratory experiments, the current study confirms that the B. thermophilus symbiont is a psychrophile for which thiosulfate and sulfide stimulate CO2 fixation. It strongly indicates that the symbiont is a chemoautotroph by establishing the following: (1) Sulfide and thiosulfate can stimulate CO2 fixation by partially purified symbionts by up to 43-fold and 120-fold, respectively; (2) the ribulose-1,5-bisphosphate carboxylase/oxygenase activity of the symbiont is sufficient to account for its sulfide- or thiosulfate-stimulated CO2 incorporation; (3) the symbiont's molar growth yield on thiosulfate, as judged by CO2 incorporation, is indistinguishable from that of free-living chemoautotrophs. Due to the high protein-degrading activity of B. thermophilus gill lysate, it is also suggested that host lysis of symbionts plays a more important role in the nutrition of the vent mussel than in R. pachyptila or C. magnifica, for which no comparable protein-degrading activity was found. 相似文献
29.
30.
The brittle stars Amphiura filiformis (Müller) and Ophiura albida (Forbes) were exposed to different oxygen saturations (100, 10, 5, 3, and <1% oxygen saturation) and to physiological anoxia
(<1% oxygen saturation) at different total sulfide concentrations (0, 2, 20, 200 μM). The mortality was followed during experiments and the median survival time (LT50) was determined. The infaunal A. filiformis had a significantly higher tolerance to both hypoxia and sulfide than did the epibenthic O. albida. After exposure to 10% oxygen saturation for a month, only 2.0% A. filiformis and 0% O. albida were dead. In oxygen saturations <1% A. filiformis and O. albida had a LT50 of 7.5 and 2.5 d, respectively. The presence of even very small concentrations of sulfide decreased the survival significantly.
Sulfide is shown to be the key factor for the survival of the two species.
Received: 11 October 1996 / Accepted: 12 November 1996 相似文献