首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9723篇
  免费   734篇
  国内免费   4篇
  2023年   53篇
  2022年   95篇
  2021年   204篇
  2020年   174篇
  2019年   215篇
  2018年   274篇
  2017年   229篇
  2016年   327篇
  2015年   559篇
  2014年   553篇
  2013年   683篇
  2012年   839篇
  2011年   771篇
  2010年   514篇
  2009年   466篇
  2008年   566篇
  2007年   538篇
  2006年   522篇
  2005年   478篇
  2004年   441篇
  2003年   363篇
  2002年   344篇
  2001年   86篇
  2000年   68篇
  1999年   90篇
  1998年   118篇
  1997年   92篇
  1996年   66篇
  1995年   61篇
  1994年   66篇
  1993年   63篇
  1992年   40篇
  1991年   40篇
  1990年   45篇
  1989年   38篇
  1988年   31篇
  1987年   27篇
  1986年   23篇
  1985年   30篇
  1984年   40篇
  1983年   22篇
  1982年   27篇
  1981年   25篇
  1980年   14篇
  1979年   13篇
  1978年   14篇
  1976年   13篇
  1975年   16篇
  1974年   10篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
Abstract

For a feasible microalgae biodiesel, increasing lipid productivity is a key parameter. An important cultivation parameter is light wavelength (λ). It can affect microalgal growth, lipid yield, and fatty acid composition. In the current study, the mixture design was used as an alternative to model the influence of the λ on the Dunaliella salina lipid productivity. The illumination was considered to be the mixture of different λ (the light colors blue, red, and green). All experiments were performed with and without sodium acetate (4?g/L), as carbon source, allowing the identification of the impact of the cultivation regimen (autotrophic or mixotrophic). Without sodium acetate, the highest lipid productivity was obtained using blue and red light. The use of mixotrophic cultivations significantly enhanced the results. The optimum obtained result was mixotrophic cultivation under 65% blue and 35% green light, resulting in biomass productivity of 105.06 mgL?1day?1, a lipid productivity of 53.47 mgL?1day?1, and lipid content of 50.89%. The main fatty acids of the oil obtained in this cultivation were oleic acid (36.52%) and palmitic acid (18.31%).  相似文献   
144.
Marine heatwaves have been observed worldwide and are expected to increase in both frequency and intensity due to climate change. Such events may cause ecosystem reconfigurations arising from species range contraction or redistribution, with ecological, economic and social implications. Macrophytes such as the brown seaweed Fucus vesiculosus and the seagrass Zostera marina are foundation species in many coastal ecosystems of the temperate northern hemisphere. Hence, their response to extreme events can potentially determine the fate of associated ecosystems. Macrophyte functioning is intimately linked to the maintenance of photosynthesis, growth and reproduction, and resistance against pathogens, epibionts and grazers. We investigated morphological, physiological, pathological and chemical defence responses of western Baltic Sea F. vesiculosus and Z. marina populations to simulated near‐natural marine heatwaves. Along with (a) the control, which constituted no heatwave but natural stochastic temperature variability (0HW), two treatments were applied: (b) two late‐spring heatwaves (June, July) followed by a summer heatwave (August; 3HW) and (c) a summer heatwave only (1HW). The 3HW treatment was applied to test whether preconditioning events can modulate the potential sensitivity to the summer heatwave. Despite the variety of responses measured in both species, only Z. marina growth was impaired by the accumulative heat stress imposed by the 3HW treatment. Photosynthetic rate, however, remained high after the last heatwave indicating potential for recovery. Only epibacterial abundance was significantly affected in F. vesiculosus. Hence both macrophytes, and in particular F. vesiculosus, seem to be fairly tolerant to short‐term marine heatwaves at least at the intensities applied in this experiment (up to 5°C above mean temperature over a period of 9 days). This may partly be due to the fact that F. vesiculosus grows in a highly variable environment, and may have a high phenotypic plasticity.  相似文献   
145.
146.
147.
148.
Wetlands Ecology and Management - The mangrove-estuarine system of Marismas Nacionales, Mexico is considered the most extensive wetland complex of the eastern Pacific coast. Originally, this large...  相似文献   
149.
The Mediterranean Basin is a global biodiversity hotspot, hosting a number of native species belonging to families that are found almost exclusively in tropical climates. Yet, whether or not these taxa were able to survive in the Mediterranean region during the Quaternary climatic oscillations remains unknown. Focusing on the European free-tailed bat (Tadarida teniotis), we aimed to (a) identify potential ancient populations and glacial refugia; (b) determine the post-glacial colonization routes across the Mediterranean; and (c) evaluate current population structure and demography. Mitochondrial and nuclear markers were used to understand T. teniotis evolutionary and demographic history. We show that T. teniotis is likely restricted to the Western Palearctic, with mitochondrial phylogeny suggesting a split between an Anatolian/Middle East clade and a European clade. Nuclear data pointed to three genetic populations, one of which is an isolated and highly differentiated group in the Canary Islands, another distributed across Iberia, Morocco, and France, and a third stretching from Italy to the east, with admixture following a pattern of isolation by distance. Evolutionary and demographic reconstruction supports a pre-Last Glacial Maximum (LGM) colonization of Italy and the Anatolian/Middle East, while the remaining populations were colonized from Italy after the Younger Dryas. We also found support for demographic expansion following the Iberian colonization. The results show that during the LGM T. teniotis persisted in Mediterranean refugia and has subsequently expanded to its current circum-Mediterranean range. Our findings raise questions regarding the physiological and ecological traits that enabled species with tropical affinities to survive in colder climates.  相似文献   
150.
The International Journal of Life Cycle Assessment - Given the increasing importance of political decision-making to reduce emission targets, the main purpose of the current paper is to identify...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号