全文获取类型
收费全文 | 390篇 |
免费 | 51篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 16篇 |
2016年 | 7篇 |
2015年 | 25篇 |
2014年 | 21篇 |
2013年 | 27篇 |
2012年 | 25篇 |
2011年 | 24篇 |
2010年 | 20篇 |
2009年 | 8篇 |
2008年 | 16篇 |
2007年 | 22篇 |
2006年 | 16篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 24篇 |
2002年 | 17篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 12篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1971年 | 1篇 |
1967年 | 3篇 |
1966年 | 4篇 |
1958年 | 1篇 |
1934年 | 1篇 |
1933年 | 1篇 |
排序方式: 共有441条查询结果,搜索用时 312 毫秒
41.
42.
Populations of the introduced Heracleum mantegazzianum consist of dense central stands, which gradually give way to open stands towards the margins. To analyse whether open stands
are due to unsuitable conditions or represent the invading front for further spread, we studied life-cycle, population dynamics,
stand structure and soil conditions of open and dense stands over two transition periods. Populations decreased during the
first interval but increased after the extremely dry and warm summer of 2003 during the second interval. Open stands had shorter
generation times, lower height, smaller proportions of small individuals and were less in equilibrium with the environment
than dense stands. In open stands, growth to higher stages was most important, while in dense stands delayed development (self-loops)
had a strong effect on population growth; stasis and fecundity contributed most to the difference in λ between stand types.
By petiole extension H. mantegazzianum may raise its leaves just above the resident vegetation. Therefore, younger stages develop faster in open stands, whereas
strong competition by conspecific adults leads to longer generation times and a higher proportion of small individuals in
dense stands. Disturbance due to extreme climatic conditions in summer 2003 equalised population dynamics of both stand types.
Life-cycle variation between stand types makes it difficult to infer simple management rules. However, our data suggest that
small and/or open stands of H. mantegazzianum may eventually serve as initials for further spread after land-use changes, whereas dense stands are stable and may represent
sources of propagules. 相似文献
43.
Relocation,high‐latitude warming and host genetic identity shape the foliar fungal microbiome of poplars
下载免费PDF全文
![点击此处可从《Molecular ecology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Miklós Bálint László Bartha Robert B. O'Hara Matthew S. Olson Jürgen Otte Markus Pfenninger Amanda L. Robertson Peter Tiffin Imke Schmitt 《Molecular ecology》2015,24(1):235-248
Micro‐organisms associated with plants and animals affect host fitness, shape community structure and influence ecosystem properties. Climate change is expected to influence microbial communities, but their reactions are not well understood. Host‐associated micro‐organisms are influenced by the climate reactions of their hosts, which may undergo range shifts due to climatic niche tracking, or may be actively relocated to mitigate the effects of climate change. We used a common‐garden experiment and rDNA metabarcoding to examine the effect of host relocation and high‐latitude warming on the complex fungal endophytic microbiome associated with leaves of an ecologically dominant boreal forest tree (Populus balsamifera L.). We also considered the potential effects of poplar genetic identity in defining the reactions of the microbiome to the treatments. The relocation of hosts to the north increased the diversity of the microbiome and influenced its structure, with results indicating enemy release from plausible pathogens. High‐latitude warming decreased microbiome diversity in comparison with natural northern conditions. The warming also caused structural changes, which made the fungal communities distinct in comparison with both low‐latitude and high‐latitude natural communities, and increased the abundance of plausible pathogens. The reactions of the microbiome to relocation and warming were strongly dependent on host genetic identity. This suggests that climate change effects on host–microbiome systems may be mediated by the interaction of environmental factors and the population genetic processes of the hosts. 相似文献
44.
Enzymatic degradation of lignin‐carbohydrate complexes (LCCs): Model studies using a fungal glucuronoyl esterase from Cerrena unicolor
下载免费PDF全文
![点击此处可从《Biotechnology and bioengineering》网站下载免费的PDF全文](/ch/ext_images/free.gif)
45.
46.
The effects of plants (corn, soybean, and sunflower) and fertilizer on mobility of more than 60 elements were assessed in a greenhouse experiment. Unplanted columns with the same soil served as controls. Half the columns received fertilizer and all columns were watered at the same rate. At the end of the experiment, the columns were watered to mimic a rainstorm event such that water drained from the bases of the columns, which was collected and analyzed for element content. Soil from between the roots of the plants was also collected and the water-extractable fraction determined. It was expected that (1) more mobile elements, as measured by water extraction, would be leached from the soils at a higher rate compared to less mobile elements, (2) plants would immobilize most elements, but that some would be immobilized, and (3) that this would depend on plant species. The results led to the following conclusions: plants cause metal mobility to vary over a wide range for a specific soil and do mobilize some elements (e.g., Th) while immobilizing others (e.g., U). The effects depended on plant species for some elements. Water-extractable fractions of elements do not predict mobility. 相似文献
47.
48.
We present here a neural network based method for prediction of N-terminal acetylation-by far the most abundant post-translational modification in eukaryotes. The method was developed on a yeast dataset for N-acetyltransferase A (NatA) acetylation, which is the type of N-acetylation for which most examples are known and for which orthologs have been found in several eukaryotes. We obtain correlation coefficients close to 0.7 on yeast data and a sensitivity up to 74% on mammalian data, suggesting that the method is valid for eukaryotic NatA orthologs. 相似文献
49.
Richter R Bistrian R Escher S Forssmann WG Vakili J Henschler R Spodsberg N Frimpong-Boateng A Forssmann U 《Journal of immunology (Baltimore, Md. : 1950)》2005,175(3):1599-1608
Monocyte infiltration into inflammatory sites is generally preceded by neutrophils. We show here that neutrophils may support this process by activation of CCL15, a human chemokine circulating in blood plasma. Neutrophils were found to release CCL15 proteolytic activity in the course of hemofiltration of blood from renal insufficiency patients. Processing of CCL15 immunoreactivity (IR) in the pericellular space is suggested by a lack of proteolytic activity in blood and blood filtrate, but a shift of the retention time (t(R)) of CCL15-IR, detected by chromatographic separation of CCL15-IR in blood and hemofiltrate. CCL15 molecules with N-terminal deletions of 23 (delta23) and 26 (delta26) aa were identified as main proteolytic products in hemofiltrate. Neutrophil cathepsin G was identified as the principal protease to produce delta23 and delta26 CCL15. Also, elastase displays CCL15 proteolytic activity and produces a delta21 isoform. Compared with full-length CCL15, delta23 and delta26 isoforms displayed a significantly increased potency to induce calcium fluxes and chemotactic activity on monocytes and to induce adhesiveness of mononuclear cells to fibronectin. Thus, our findings indicate that activation of monocytes by neutrophils is at least in part induced by quantum proteolytic processing of circulating or endothelium-bound CCL15 by neutrophil cathepsin G. 相似文献
50.
Peter Munk Michael M. Hansen Gregory E. Maes Torkel G. Nielsen Martin Castonguay Lasse Riemann Henrik Sparholt Thomas D. Als Kim Aarestrup Nikolaj G. Andersen Mirjam Bachler 《Proceedings. Biological sciences / The Royal Society》2010,277(1700):3593-3599
Anguillid freshwater eels show remarkable life histories. In the Atlantic, the European eel (Anguilla anguilla) and American eel (Anguilla rostrata) undertake extensive migrations to spawn in the oceanic Sargasso Sea, and subsequently the offspring drift to foraging areas in Europe and North America, first as leaf-like leptocephali larvae that later metamorphose into glass eels. Since recruitment of European and American glass eels has declined drastically during past decades, there is a strong demand for further understanding of the early, oceanic phase of their life cycle. Consequently, during a field expedition to the eel spawning sites in the Sargasso Sea, we carried out a wide range of dedicated bio-physical studies across areas of eel larval distribution. Our findings suggest a key role of oceanic frontal processes, retaining eel larvae within a zone of enhanced feeding conditions and steering their drift. The majority of the more westerly distributed American eel larvae are likely to follow a westerly/northerly drift route entrained in the Antilles/Florida Currents. European eel larvae are generally believed to initially follow the same route, but their more easterly distribution close to the eastward flowing Subtropical Counter Current indicates that these larvae could follow a shorter, eastward route towards the Azores and Europe. The findings emphasize the significance of oceanic physical–biological linkages in the life-cycle completion of Atlantic eels. 相似文献