全文获取类型
收费全文 | 284篇 |
免费 | 13篇 |
专业分类
297篇 |
出版年
2023年 | 1篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 21篇 |
2012年 | 34篇 |
2011年 | 19篇 |
2010年 | 14篇 |
2009年 | 14篇 |
2008年 | 19篇 |
2007年 | 18篇 |
2006年 | 16篇 |
2005年 | 10篇 |
2004年 | 12篇 |
2003年 | 16篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有297条查询结果,搜索用时 0 毫秒
41.
42.
Whether present-day European genetic variation and its distribution patterns can be attributed primarily to the initial peopling of Europe by anatomically modern humans during the Paleolithic, or to latter Near Eastern Neolithic input is still the subject of debate. Southeastern Europe has been a crossroads for several cultures since Paleolithic times and the Balkans, specifically, would have been part of the route used by Neolithic farmers to enter Europe. Given its geographic location in the heart of the Balkan Peninsula at the intersection of Central and Southeastern Europe, Serbia represents a key geographical location that may provide insight to elucidate the interactions between indigenous Paleolithic people and agricultural colonists from the Fertile Crescent. In this study, we examine, for the first time, the Y-chromosome constitution of the general Serbian population. A total of 103 individuals were sampled and their DNA analyzed for 104 Y-chromosome bi-allelic markers and 17 associated STR loci. Our results indicate that approximately 58% of Serbian Y-chromosomes (I1-M253, I2a-P37.2 and R1a1a-M198) belong to lineages believed to be pre-Neolithic. On the other hand, the signature of putative Near Eastern Neolithic lineages, including E1b1b1a1-M78, G2a-P15, J1-M267, J2-M172 and R1b1a2-M269 accounts for 39% of the Y-chromosome. Haplogroup frequency distributions in Western and Eastern Europe reveal a spotted landscape of paleolithic Y chromosomes, undermining continental-wide generalizations. Furthermore, an examination of the distribution of Y-chromosome filiations in Europe indicates extreme levels of Paleolithic lineages in a region encompassing Serbia, Bosnia-Herzegovina and Croatia, possibly the result of Neolithic migrations encroaching on Paleolithic populations against the Adriatic Sea. 相似文献
43.
Kostic Ljiljana Nikolic Nina Bosnic Dragana Samardzic Jelena Nikolic Miroslav 《Plant and Soil》2017,419(1-2):447-455
Plant and Soil - Although silicon (Si) is known to improve plant growth under low phosphorus (P) conditions, the in planta mechanisms responsible for this effect are still unknown. Here, we... 相似文献
44.
Close and distant: Contrasting the metabolism of two closely related subspecies of Scots pine under the effects of folivory and summer drought 下载免费PDF全文
Albert Rivas‐Ubach Jordi Sardans José Antonio Hódar Joan Garcia‐Porta Alex Guenther Ljiljana Paša‐Tolić Michal Oravec Otmar Urban Josep Peñuelas 《Ecology and evolution》2017,7(21):8976-8988
Metabolomes, as chemical phenotypes of organisms, are likely not only shaped by the environment but also by common ancestry. If this is the case, we expect that closely related species of pines will tend to reach similar metabolomic solutions to the same environmental stressors. We examined the metabolomes of two sympatric subspecies of Pinus sylvestris in Sierra Nevada (southern Iberian Peninsula), in summer and winter and exposed to folivory by the pine processionary moth. The overall metabolomes differed between the subspecies but both tended to respond more similarly to folivory. The metabolomes of the subspecies were more dissimilar in summer than in winter, and iberica trees had higher concentrations of metabolites directly related to drought stress. Our results are consistent with the notion that certain plant metabolic responses associated with folivory have been phylogenetically conserved. The larger divergence between subspecies metabolomes in summer is likely due to the warmer and drier conditions that the northern iberica subspecies experience in Sierra Nevada. Our results provide crucial insights into how iberica populations would respond to the predicted conditions of climate change under an increased defoliation in the Mediterranean Basin. 相似文献
45.
The aim of our study was to assess cerebral vasoreactivity (CVR) in type 2 diabetes mellitus (DM2) and factors which may influence on it. According to previous studies, evaluating CVR in DM2 on the similar way, the results were dubious. For the evaluation CVR we used breath holding index (BHI) and transcranial Doppler ultrasound (TCD) in 50 patients with DM2 and 50 sex- and age-matched healthy controls. We observed epidemiologic and clinic data, other vascular risk factors and laboratory parameters. We found statistically significant difference in BHI between patients with DM2 (BHI = 0.69 +/- 0.31) and age- and sex-matched healthy controls (BHI = 1.33+/-0.28) (p < 0.05 ). Because of a significant correlation between BHI and age (p < 0.001) in healthy controls we made an adjustment of BHI for age before further analyses (BHIadj). In DM2 group we found a significant correlation between BHIadj and age (p = 0.0004), fasting glycemia (p = 0.04), and albuminuria (p = 0.04) (creatinine clearance in multivariate analysis (p = 0.007)). Our study has shown that CVR is impaired in DM2 patients and that it's severity was associated with age, fasting glycemia and renal function. Functional TCD is a very good screening method for detection and monitoring of cerebral microangiopathic changes in DM2 patients. 相似文献
46.
47.
Unraveling the evolution of auxin signaling 总被引:1,自引:0,他引:1
De Smet I Voss U Lau S Wilson M Shao N Timme RE Swarup R Kerr I Hodgman C Bock R Bennett M Jürgens G Beeckman T 《Plant physiology》2011,155(1):209-221
Auxin signaling is central to plant growth and development, yet hardly anything is known about its evolutionary origin. While the presence of key players in auxin signaling has been analyzed in various land plant species, similar analyses in the green algal lineages are lacking. Here, we survey the key players in auxin biology in the available genomes of Chlorophyta species. We found that the genetic potential for auxin biosynthesis and AUXIN1 (AUX1)/LIKE AUX1- and P-GLYCOPROTEIN/ATP-BINDING CASSETTE subfamily B-dependent transport is already present in several single-celled and colony-forming Chlorophyta species. In addition, our analysis of expressed sequence tag libraries from Coleochaete orbicularis and Spirogyra pratensis, green algae of the Streptophyta clade that are evolutionarily closer to the land plants than those of the Chlorophyta clade, revealed the presence of partial AUXIN RESPONSE FACTORs and/or AUXIN/INDOLE-3-ACETIC ACID proteins (the key factors in auxin signaling) and PIN-FORMED-like proteins (the best-characterized auxin-efflux carriers). While the identification of these possible AUXIN RESPONSE FACTOR- and AUXIN/INDOLE-3-ACETIC ACID precursors and putative PIN-FORMED orthologs calls for a deeper investigation of their evolution after sequencing more intermediate genomes, it emphasizes that the canonical auxin response machinery and auxin transport mechanisms were, at least in part, already present before plants "moved" to land habitats. 相似文献
48.
49.
We report the further south‐eastward range extension of the invasive Asian mud‐daubing wasp, Sceliphron curvatum (Smith), initially introduced into Austria in the late 1970s. We document its presence in the central Balkan Peninsula from 1997 onwards, and we discuss the circumstances and course of its recent expansion in the area. We also report the first finding of another Asian species, Sceliphron deforme (Smith), in Europe, and we consider various aspects of this case, given the possibility that the record from southern Montenegro represents a successful introduction. 相似文献
50.