全文获取类型
收费全文 | 206篇 |
免费 | 24篇 |
国内免费 | 34篇 |
专业分类
安全科学 | 34篇 |
废物处理 | 3篇 |
环保管理 | 20篇 |
综合类 | 66篇 |
基础理论 | 89篇 |
污染及防治 | 11篇 |
评价与监测 | 14篇 |
社会与环境 | 22篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 11篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 13篇 |
2016年 | 6篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 13篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 21篇 |
2007年 | 33篇 |
2006年 | 10篇 |
2005年 | 9篇 |
2004年 | 8篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有264条查询结果,搜索用时 734 毫秒
21.
南岭山区传统聚落景观资源及其旅游开发研究 总被引:6,自引:0,他引:6
南岭山区的乡村传统聚落,经特定历史地理环境的演进和发展,以其特有的景观美学价值、鲜明的地域文化特色和科学实用价值的完美结合,而成为极为珍贵的历史文化遗产。由于古代南岭山区复杂地理环境的隔绝机制和移民们一直恪守着祖宗留下的遗风,其聚落景观至今得以大量保存而成为极富开发价值的
旅游资源。为促进南岭山区21世纪社会经济的快速发展,应将这一丰富的旅游资源的开发利用和保护列入议事日程。但必须深入调查研究,并坚持突出重点,择优开发;因地制宜,突出地域文化特色;旅游开发与乡村社会经济发展协调;保护与利用并重等开发原则。 相似文献
22.
铝盐最佳混凝形态及最佳pH范围研究 总被引:38,自引:3,他引:38
本文从理论上分析了铝盐的水解聚合过程,预测了铝盐混凝过程进行时的最佳混凝形态及最佳pH范围,并且通过实验手段分析说明了铝盐的最佳混凝形态,混凝特征及最佳pH范围,得到了较为一致的结果。 相似文献
23.
Studies of habitat selection and movements often use radio-tracking data for defining animal home ranges. Home ranges (HR) can be approximated by a utilization density distribution (UD) that instead of assuming uniform use of areas within HR boundary provides a probabilistic measure of animal space use. In reality, radio-tracking data contain periods of frequent autocorrelated observations interspersed with temporally more independent observations. Using such temporally irregular data directly may result in biased UD estimates, because areas that have been sampled intensively receive too much weight. The problem of autocorrelation has been tackled by resampling data with an appropriate time interval. However, resampling may cause a large reduction in the data set size along with a loss of information. Evidently, biased UD estimates or reduction in data may prejudice the results on animal habitat selection and movement. We introduce a new method for estimating UDs with temporally irregular data. The proposed method, called the time kernel, accounts for temporal aggregation of observations and gives less weight to temporally autocorrelated observations. A further extension of the method accounts also for spatially aggregated observations with relatively low weights given to observations that are both temporally and spatially aggregated. We test the behaviour of the time kernel method and its spatiotemporal version using simulated data. In addition, the method is applied to a data set of brown bear locations. 相似文献
24.
25.
Elie Gaget Diego Pavón-Jordán Alison Johnston Aleksi Lehikoinen Wesley M. Hochachka Brett K. Sandercock Alaaeldin Soultan Hichem Azafzaf Nadjiba Bendjedda Taulant Bino Luka Božič Preben Clausen Mohamed Dakki Koen Devos Cristi Domsa Vitor Encarnação Kiraz Erciyas-Yavuz Sándor Faragó Teresa Frost Clemence Gaudard Lívia Gosztonyi Fredrik Haas Menno Hornman Tom Langendoen Christina Ieronymidou Vasiliy A. Kostyushin Lesley J. Lewis Svein-Håkon Lorentsen Leho Luigujõe Włodzimierz Meissner Tibor Mikuska Blas Molina Zuzana Musilová Viktor Natykanets Jean-Yves Paquet Nicky Petkov Danae Portolou Jozef Ridzoň Samir Sayoud Marko Šćiban Laimonas Sniauksta Antra Stīpniece Nicolas Strebel Norbert Teufelbauer Goran Topić Danka Uzunova Andrej Vizi Johannes Wahl Marco Zenatello Jon E. Brommer 《Conservation biology》2021,35(3):834-845
Climate warming is driving changes in species distributions and community composition. Many species have a so-called climatic debt, that is, shifts in range lag behind shifts in temperature isoclines. Inside protected areas (PAs), community changes in response to climate warming can be facilitated by greater colonization rates by warm-dwelling species, but also mitigated by lowering extirpation rates of cold-dwelling species. An evaluation of the relative importance of colonization-extirpation processes is important to inform conservation strategies that aim for both climate debt reduction and species conservation. We assessed the colonization-extirpation dynamics involved in community changes in response to climate inside and outside PAs. To do so, we used 25 years of occurrence data of nonbreeding waterbirds in the western Palearctic (97 species, 7071 sites, 39 countries, 1993–2017). We used a community temperature index (CTI) framework based on species thermal affinities to investigate species turnover induced by temperature increase. We determined whether thermal community adjustment was associated with colonization by warm-dwelling species or extirpation of cold-dwelling species by modeling change in standard deviation of the CTI (CTISD). Using linear mixed-effects models, we investigated whether communities in PAs had lower climatic debt and different patterns of community change than communities outside PAs. For CTI and CTISD combined, communities inside PAs had more species, higher colonization, lower extirpation, and lower climatic debt (16%) than communities outside PAs. Thus, our results suggest that PAs facilitate 2 independent processes that shape community dynamics and maintain biodiversity. The community adjustment was, however, not sufficiently fast to keep pace with the large temperature increases in the central and northeastern western Palearctic. Our results underline the potential of combining CTI and CTISD metrics to improve understanding of the colonization-extirpation patterns driven by climate warming. 相似文献
26.
顾志龙 《中国安全科学学报》1998,8(1):73-77
论述了将小型链条炉排工业锅炉的炉拱设计成在运行中可以全量调节的结构,以适应燃用多种煤种的需要,并减少与固定拱操作有关的意外伤亡事故。这项技术有创新性,适用性和推广价值 相似文献
27.
The grand skink, Oligosoma grande, is a diurnal rock-dwelling lizard from the tussock grasslands of Central Otago, New Zealand, whose diet includes a variety
of arthropods and fruit. We conducted a field experiment to examine the influence of prey distribution on foraging behavior
and spacing patterns. On sites where prey distribution was unaltered (control sites), males and females differed in diet and
foraging behavior. Most male feeding attempts were directed at large strong-flying insects, and males used a saltatory search
pattern that involved relatively infrequent moves of long duration. Females spent more effort catching small weak-flying insects
and visiting fruiting plants. Their search behavior involved frequent moves of short duration. The placement of meat-bait
on experimental sites led to a redistribution of large flies without influencing other prey types. Experimental females switched
foraging strategy by adopting a search pattern of relatively infrequent moves of long duration, increasing the frequency of
attempts to capture large prey, and reducing the importance of fruit in their diet. The experimental manipulation appeared
to influence space use. On control sites, both sexes had comparably sized home ranges. On experimental sites, male home ranges
were significantly larger than female home ranges.
Received: 3 November 1997 / Accepted after revision: 13 December 1998 相似文献
28.
北京市夏季空气微生物粒度分布特征 总被引:19,自引:6,他引:13
着重研究了夏季空气微生物的粒度分布特征,比较分析了北京市空气微生物粒度分布的变化状况.结果表明:空气细菌、空气真菌和空气放线菌的粒度分布特征各不相同, 并且不随着时间和空间的变化而变化.空气细菌呈偏态分布,大于2.0 μm的粒子约占总数的80.0%,小于1.0 μm的粒子最少,约占9.0%.空气真菌呈对数正态分布,1.0~6.0 μm的粒子约占70.0%,小于1.0 μm的粒子最少,约占5.0%.空气放线菌粒度分布与正态分布恰好相反,大于8.2 μm和小于1.0 μm的粒子约占60.0%;3.0~6.0 μm的粒子最少,约占10.0%.此外不同功能区优势真菌粒度分布规律基本一致.枝孢属(Cladosporium),青霉属(Penicillium)和曲霉属(Aspergillus)粒度主要分布在F3,F4和F5(1.0~6.0 μm)中,约占总数的85.0%,呈对数正态分布.而交链孢属(Alternaria)和无孢菌(nonsporing)主要分布在前4级(>2.0 μm),分别约占总数的90.0%和75.0%,呈偏态分布.在过去10年的城市化进程中,北京市空气微生物粒度分布的基本趋势没有变化,但是空气真菌粒度分布的峰值由原来的3.0~6.0 μm降低到2.0~3.0 μm. 相似文献
29.
Li Yang Tao Chen Kai-Chong Shi Lu Zhang Ngwe Lwin Peng-Fei Fan 《Conservation biology》2023,37(1):e14045
Species shift their distribution in response to climate and land-cover change, which may result in a spatial mismatch between currently protected areas (PAs) and priority conservation areas (PCAs). We examined the effects of climate and land-cover change on potential range of gibbons and sought to identify PCAs that would conserve them effectively. We collected global gibbon occurrence points and modeled (ecological niche model) their current and potential 2050s ranges under climate-change and different land-cover-change scenarios. We examined change in range and PA coverage between the current and future ranges of each gibbon species. We applied spatial conservation prioritization to identify the top 30% PCAs for each species. We then determined how much of the PCAs are conserved in each country within the global range of gibbons. On average, 31% (SD 22) of each species’ current range was covered in PAs. PA coverage of the current range of 9 species was <30%. Nine species lost on average 46% (SD 29) of their potential range due to climate change. Under climate-change with an optimistic land-cover-change scenario (B1), 12 species lost 39% (SD 28) of their range. In a pessimistic land-cover-change scenario (A2), 15 species lost 36% (SD 28) of their range. Five species lost significantly more range under the A2 scenario than the B1 scenario (p = 0.01, SD 0.01), suggesting that gibbons will benefit from effective management of land cover. PA coverage of future range was <30% for 11 species. On average, 32% (SD 25) of PCAs were covered by PAs. Indonesia contained more species and PCAs and thus has the greatest responsibility for gibbon conservation. Indonesia, India, and Myanmar need to expand their PAs to fulfill their responsibility to gibbon conservation. Our results provide a baseline for global gibbon conservation, particularly for countries lacking gibbon research capacity. 相似文献
30.
The effect of seawater salinity on nitrite accumulation in short-range nitrification to nitrite as the end product was studied by using a SBR. Experimental results indicated that the growth of nitrobacteria was inhibited and very high levels of nitrite accumulation at different salinities were achieved under the conditions of 25--28℃, pH 7.5--8.0, and the influent ammonia nitrogen of 40--70mg/L when seawater flow used to flush toilet was less than 35% (salinity 12393 mg/L, Cl^- 6778mg/L) of total domestic wastewater flow, which is mainly ascribed to much high chlorine concentration of seawater. Results showed that high seawater salinity is available for short-range nitrification to nitrite as the end product. When the seawater flow used to flush toilet accounting for above 70% of the total domestic wastewater flow, the removal efficiency of ammonia was still above 80% despite the removal of organics declined obviously(less than 60% ). It was found that the effect of seawater salinity on the removal of organics was negative rather than positive one as shown for ammonia removal. 相似文献