全文获取类型
收费全文 | 217篇 |
免费 | 14篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 6篇 |
2015年 | 15篇 |
2014年 | 11篇 |
2013年 | 15篇 |
2012年 | 19篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 5篇 |
2008年 | 17篇 |
2007年 | 18篇 |
2006年 | 11篇 |
2005年 | 6篇 |
2004年 | 9篇 |
2003年 | 5篇 |
2002年 | 4篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有231条查询结果,搜索用时 15 毫秒
41.
An inventory of continental U.S. terrestrial candidate ecological restoration areas based on landscape context
下载免费PDF全文
![点击此处可从《Restoration Ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
James Wickham Kurt Riitters Peter Vogt Jennifer Costanza Anne Neale 《Restoration Ecology》2017,25(6):894-902
Landscape context is an important factor in restoration ecology, but the use of landscape context for site prioritization has not been as fully developed. We used morphological image processing to identify candidate ecological restoration areas based on their proximity to existing natural vegetation. We identified 1,102,720 candidate ecological restoration areas across the continental United States. Candidate ecological restoration areas were concentrated in the Great Plains and eastern United States. We populated the database of candidate ecological restoration areas with 17 attributes related to site content and context, including factors such as soil fertility and roads (site content), and number and area of potentially conjoined vegetated regions (site context) to facilitate its use for site prioritization. We demonstrate the utility of the database in the state of North Carolina, U.S.A. for a restoration objective related to restoration of water quality (mandated by the U.S. Clean Water Act), wetlands, and forest. The database will be made publicly available on the U.S. Environmental Protection Agency's EnviroAtlas website ( http://enviroatlas.epa.gov ) for stakeholders interested in ecological restoration. 相似文献
42.
Manuel J. Lpez‐Rodríguez Ignacio Peralta‐Maraver Brunella Gaetani Carmen E. Sainz‐Cantero Romolo Fochetti J. Manuel Tierno de Figueroa 《International Review of Hydrobiology》2012,97(6):485-496
In this work we present the results of a one‐year study on the macroinvertebrate community in an intermittent stream in southern Spain. We have studied the taxonomic composition, diversity and food web monthly in order to consider temporal variability in these parameters. More than 60 macroinvertebrate taxa have been recorded in the stream, but they do not cohabit at the same time. Many of them join the community at the beginning of the wet period. Afterwards, some new taxa incorporate but some others disappear. This leads to huge fluctuations in the diversity of the community and in the food web of different sampling dates. These variations are linked to environmental disturbances, mainly to flow peaks and minimums. From a relatively well structured, but simple, food web at the beginning of the wet period, it can be seen how several trophic levels disappear with time, and how several organisms change or extend their trophic function within it. We relate these variations to the intermediate disturbance hypothesis and discuss the resilience of the community of this intermittent stream (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
43.
Laura Pantaleoni Paolo Longoni Lorenzo Ferroni Costanza Baldisserotto Sadhu Leelavathi Vanga Siva Reddy Simonetta Pancaldi Rino Cella 《Protoplasma》2014,251(3):639-648
The high cost of recombinant enzymes for the production of biofuel from ligno-cellulosic biomass is a crucial factor affecting the economic sustainability of the process. The use of plants as biofactories for the production of the suitable recombinant enzymes might be an alternative to microbial fermentation. In the case of enzyme accumulation in chloroplasts, it is fundamental to focus on the issue of full photosynthetic efficiency of transplastomic plants in the field where they might be exposed to abiotic stress such as high light intensity and high temperature. Xylanases (EC 3.2.1.8), a group of enzymes that hydrolyse linear polysaccharides of beta-1,4-xylan into xylose, find an application in the biofuel industry favouring biomass saccharification along with other cell-wall degrading enzymes. In the present study, we analysed how a high level of accumulation of a thermostable xylanase in tobacco chloroplasts does not impact on photosynthetic performance of transplastomic plants grown outdoors. The recombinant enzyme was found to be stable during plant development, ex planta and after long-term storage. 相似文献
44.
What is a healthy ecosystem? 总被引:21,自引:0,他引:21
Rapid deterioration of the world's major ecosystems has intensified the need for effective environmental monitoring and the development of operational indicators of ecosystem health. Ecosystem health represents a desired endpoint of environmental management, but it requires adaptive, ongoing definition and assessment. We propose that a healthy ecosystem is one that is sustainable – that is, it has the ability to maintain its structure (organization) and function (vigor) over time in the face of external stress (resilience). Various methods to quantify these three ecosystem attributes (vigor, organization, and resilience) are discussed. These attributes are then folded into a comprehensive assessment of ecosystem health. A network analysis based ecosystem health assessment is developed and tested using trophic exchange networks representing several different aquatic ecosystems. Results indicate the potential of such an ecosystem health assessment for evaluating the relative health of similar ecosystems, and quantifying the effects of natural or anthropogenic stress on the health of a particular ecosystem over time. 相似文献
45.
Adam J. Terando Jennifer Costanza Curtis Belyea Robert R. Dunn Alexa McKerrow Jaime A. Collazo 《PloS one》2014,9(7)
The future health of ecosystems is arguably as dependent on urban sprawl as it is on human-caused climatic warming. Urban sprawl strongly impacts the urban ecosystems it creates and the natural and agro-ecosystems that it displaces and fragments. Here, we project urban sprawl changes for the next 50 years for the fast-growing Southeast U.S. Previous studies have focused on modeling population density, but the urban extent is arguably as important as population density per se in terms of its ecological and conservation impacts. We develop simulations using the SLEUTH urban growth model that complement population-driven models but focus on spatial pattern and extent. To better capture the reach of low-density suburban development, we extend the capabilities of SLEUTH by incorporating street-network information. Our simulations point to a future in which the extent of urbanization in the Southeast is projected to increase by 101% to 192%. Our results highlight areas where ecosystem fragmentation is likely, and serve as a benchmark to explore the challenging tradeoffs between ecosystem health, economic growth and cultural desires. 相似文献
46.
Tobias Rheude Costanza Pellegrini Wibke Reinhard Teresa Trenkwalder Wolfgang Koenig N. Patrick Mayr 《Biomarkers》2018,23(3):299-304
Purpose: Elevated carbohydrate antigen 125 (CA125) predicts adverse outcome after transcatheter aortic valve implantation (TAVI). While known underlying pathophysiological mechanisms of elevated CA125 include serosal effusions and inflammatory stimuli, clinical determinants associated with elevated CA125 in patients referred for TAVI remain unknown. Therefore, we investigated clinical, laboratory and echocardiographic determinants of elevated CA125 in patients with severe aortic valve stenosis referred for TAVI.Methods: This study includes 650 patients with severe aortic stenosis referred for TAVI. Baseline CA125 was determined by an immunoassay and dichotomized (elevated versus normal) based on the manufacturer cutoff value (>35?U/mL).Results: CA125 elevation was present in 28% (181/650). Patients with elevated CA125 had an overall worse clinical profile and were more symptomatic with a higher rate of NYHA class III/IV (80% versus 58%; p?0.001). In a multivariate analysis, independent predictors of elevated CA125 were New York Heart Association (NYHA) class, baseline hemoglobin, C-reactive protein (CRP), left ventricular ejection fraction and severe tricuspid regurgitation.Conclusion: Elevated CA125 levels in patients referred for TAVI summarize a subset of patients with an overall worse clinical profile who are more symptomatic. 相似文献
47.
Robert Cheng Brunella Felicetti Shilpa Palan Ian Toogood‐Johnson Christoph Scheich John Barker Mark Whittaker Thomas Hesterkamp 《Protein science : a publication of the Protein Society》2010,19(1):168-173
The Mapkap kinases 2 and 3 (MK2 and MK3) have been implicated in intracellular signaling pathways leading to the production of the pro‐inflammatory cytokine tumor necrosis factor alpha. MK2 has been pursued by the biopharmaceutical industry for many years for the development of a small molecule anti‐inflammatory treatment and drug‐like inhibitors have been described. The development of some of these compounds, however, has been slowed by the absence of a high‐resolution crystal structure of MK2. Herein we present a high‐resolution (1.9 Å) crystal structure of the highly homologous MK3 in complex with a pharmaceutical lead compound. While all of the canonical features of Ser/Thr kinases in general and MK2 in particular are recapitulated in MK3, the detailed analysis of the binding interaction of the drug‐like ligand within the adenine binding pocket allows relevant conclusions to be drawn for the further design of potent and selective drug candidates. 相似文献
48.
49.
E. van de Vosse Brunella Franco P. van der Bent Eugenio Montini Ulrike Orth Andre Hanauer N. Tijmes G.-J. B. van Ommen Andrea Ballabio J. T. den Dunnen Arthur A. B. Bergen 《Human genetics》1997,101(2):235-237
X-linked juvenile retinoschisis (RS) is a progressive vitreoretinal degeneration localised in Xp22.1-p22.2. A human homologue
of the retinal degeneration gene C (rdgC), a gene that in Drosophila melanogaster prevents light-induced retinal degeneration, was localised in the RS obligate gene region. We have tested the gene, designated
PPEF in humans, as a candidate gene in RS patients using RT-PCR and the protein truncation test on RNA and SSCP on DNA. No mutations
were identified, making it highly unlikely that PPEF is the gene implicated in RS. The data presented facilitate mutation analysis of the PPEF gene in other diseases which have been or will be localised to this region.
Received: 20 May 1997 / Accepted: 30 July 1997 相似文献
50.
Adventitious roots were observed on 3 wild perennialGlycine species, in short-poddedG. clandestina, G. latifolia and mostG. tabacina (2x, 4x, 6x), while other species lacked adventitious roots. This suggests that the adventitious roots trait is associated with B genome species. Intra- and interspecific F1 hybrids reveal that adventitious roots apparently are inherited recessively. The presence of adventitious roots or short-poddedG. clandestina, coupled with infertility with longer-poddedG. clandestina, and enzymatic and leaflet morphology differences between the twoG. clandestina subgroups, supports segregation of the short-podded form as a separate taxon. 相似文献