全文获取类型
收费全文 | 4429篇 |
免费 | 31篇 |
国内免费 | 25篇 |
专业分类
安全科学 | 43篇 |
废物处理 | 174篇 |
环保管理 | 152篇 |
综合类 | 1986篇 |
基础理论 | 820篇 |
环境理论 | 5篇 |
污染及防治 | 899篇 |
评价与监测 | 241篇 |
社会与环境 | 150篇 |
灾害及防治 | 15篇 |
出版年
2022年 | 63篇 |
2021年 | 38篇 |
2019年 | 42篇 |
2018年 | 77篇 |
2017年 | 61篇 |
2016年 | 83篇 |
2015年 | 67篇 |
2014年 | 104篇 |
2013年 | 189篇 |
2012年 | 133篇 |
2011年 | 105篇 |
2010年 | 129篇 |
2009年 | 131篇 |
2008年 | 144篇 |
2007年 | 173篇 |
2006年 | 122篇 |
2005年 | 107篇 |
2004年 | 92篇 |
2003年 | 119篇 |
2002年 | 84篇 |
2001年 | 87篇 |
2000年 | 84篇 |
1999年 | 87篇 |
1998年 | 58篇 |
1997年 | 55篇 |
1996年 | 34篇 |
1995年 | 54篇 |
1994年 | 53篇 |
1992年 | 32篇 |
1991年 | 37篇 |
1990年 | 43篇 |
1989年 | 33篇 |
1985年 | 36篇 |
1979年 | 40篇 |
1977年 | 33篇 |
1969年 | 35篇 |
1967年 | 56篇 |
1966年 | 48篇 |
1965年 | 56篇 |
1964年 | 61篇 |
1963年 | 62篇 |
1962年 | 57篇 |
1961年 | 63篇 |
1960年 | 55篇 |
1959年 | 66篇 |
1958年 | 59篇 |
1957年 | 68篇 |
1956年 | 50篇 |
1955年 | 50篇 |
1954年 | 47篇 |
排序方式: 共有4485条查询结果,搜索用时 15 毫秒
641.
Association of extinction risk of saproxylic beetles with ecological degradation of forests in Europe
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)
Sebastian Seibold Roland Brandl Jörn Buse Torsten Hothorn Jürgen Schmidl Simon Thorn Jörg Müller 《Conservation biology》2015,29(2):382-390
To reduce future loss of biodiversity and to allocate conservation funds effectively, the major drivers behind large‐scale extinction processes must be identified. A promising approach is to link the red‐list status of species and specific traits that connect species of functionally important taxa or guilds to resources they rely on. Such traits can be used to detect the influence of anthropogenic ecosystem changes and conservation efforts on species, which allows for practical recommendations for conservation. We modeled the German Red List categories as an ordinal index of extinction risk of 1025 saproxylic beetles with a proportional‐odds linear mixed‐effects model for ordered categorical responses. In this model, we estimated fixed effects for intrinsic traits characterizing species biology, required resources, and distribution with phylogenetically correlated random intercepts. The model also allowed predictions of extinction risk for species with no red‐list category. Our model revealed a higher extinction risk for lowland and large species as well as for species that rely on wood of large diameter, broad‐leaved trees, or open canopy. These results mirror well the ecological degradation of European forests over the last centuries caused by modern forestry, that is the conversion of natural broad‐leaved forests to dense conifer‐dominated forests and the loss of old growth and dead wood. Therefore, conservation activities aimed at saproxylic beetles in all types of forests in Central and Western Europe should focus on lowlands, and habitat management of forest stands should aim at increasing the amount of dead wood of large diameter, dead wood of broad‐leaved trees, and dead wood in sunny areas. 相似文献
642.
643.
644.
645.
646.
647.
Hatice Esen Ahmet Cihan Nilgün Fiğlali 《International journal of occupational safety and ergonomics》2019,25(1):123-137
Introduction. Shift patterns, work hours, work arrangements and worker motivations have increasingly become key factors for job performance. The main objective of this article is to design an expert system that identifies the negative effects of shift work and prioritizes mitigation efforts according to their importance in preventing these negative effects. The proposed expert system will be referred to as the shift expert. Methods. A thorough literature review is conducted to determine the effects of shift work on workers. Our work indicates that shift work is linked to demographic variables, sleepiness and fatigue, health and well-being, and social and domestic conditions. These parameters constitute the sections of a questionnaire designed to focus on 26 important issues related to shift work. The shift expert is then constructed to provide prevention advice at the individual and organizational levels, and it prioritizes this advice using a fuzzy analytic hierarchy process model, which considers comparison matrices provided by users during the prioritization process. An empirical study of 61 workers working on three rotating shifts is performed. After administering the questionnaires, the collected data are analyzed statistically, and then the shift expert produces individual and organizational recommendations for these workers. 相似文献
648.
649.
Georg H. M. Krause Thomas Delschen Peter Fürst Diana Hein 《Environmental Sciences Europe》1993,5(4):194-203
Soil samples were taken from residential gardens, grasslands and forests at 22 locations in Marsberg, North Rhine-Westphalia, and analyzed for PCDD/F. Sampling was concentrated on the vicinity of a former copper smelter where copper waste material (calledKieselrot) was deposited and emissions from former stacks contaminated a large land area. Maximum PCDD/F-concentrations were 407 ng TE GBA/kg dm in garden soil (0–30 cm depth), 98 ng TE BGA/kg dm in agricultural grassland (0–10 cm depth), 227 ng TE BGA/kg dm in wasteland, and up to 8073 ng TE BGA/kg dm in forest soils. PCDD/F-levels in soil decreased with increasing distance from the former sources providing a large historic emission problem, apart from the still existing kieselrot waste site. Ash residues from former flue gas duct showed up to 2,4 mg TE BGA/kg dm. PCDD/F-concentrations in vegetable samples from highly contaminated garden soils and grass from agricultural grassland were found to be relatively low in relation to soil values. PCDD/F-levels in salad showed a mean of 2,2 ng TE BGA/kg dm while grass concentrations were <6 ng TE BGA/kg dm. Thus, no correlation was found between soil and vegetation values with the exception for carrot roots where obviously a small transfer of PCDD/F between the two media took place. PCDD/F-content in grass taken over the vegetation period showed a tendency to increase toward the end of the growing season, which is probably related to changes in the dry matter yield over the season. No correlation was found in general between soil, grass and milk PCDD/F contents when all samples were taken from the same grassland. PCDD/F-concentrations in milk ranged between 0,6 and 1,1 pg TE BGA/g milkfat and were thus in the same range as consumer milk in the Federal Republic of Germany. PCDD/F in needles from conifers showed a clear relationship with respect to distance from the former waste site. The relatively high levels in conifer needles [36 ng TE BGA/kg dm] were obviously due to sporting activities (i.e. motocross racing where contaminated material was resuspended and deposited on surrounding trees). 相似文献
650.
The complete life cycle of Pycnogonum litorale Ström was observed under laboratory conditions. At 15?°C and a 16?h light:8?h dark photocycle, the duration of embryonic development from oviposition to egg-hatching varied from 32 to 111?d. The onset of egg hatching ranged from 32 to 81?d after oviposition in different egg batches, and the period between the first and the last hatch within a single egg batch varied between 16 and 57?d. The larval period, consisting of five larval instars, lasted between 66 and 113?d. Juvenile development required seven (exceptionally 8 or 9) moults and lasted between 263 and 400?d. The average interval between successive moults in juveniles increased with increasing size from 24 to 82?d. Though females did not moult more often than their male conspecifics, they reached a size from 8.5 to 11.0?mm (average 10.1?mm) while adult males measured only 7.0 to 8.5?mm (average 7.7?mm). At low temperatures (2?°C) moulting was almost completely inhibited. After raising the temperature to 6?°C, the moulting frequency increased to a rate almost as high as at a constant temperature of 15?°C. Moulting was also retarded by starvation and accelerated by subsequent feeding. Adults lived for up to 9?years without further moults, with several periods of mating and oviposition at irregular intervals. In combination with previous long-term field observations, the present results provide a more complete picture of the life cycle of P. litorale in a natural habitat. The great variation in the duration of the different developmental stages, the ability to survive periods of cold and starvation, and the longevity of the adults are important for the survival of pycnogonid populations under changing environmental conditions. 相似文献