全文获取类型
收费全文 | 389篇 |
免费 | 17篇 |
国内免费 | 24篇 |
出版年
2023年 | 6篇 |
2022年 | 10篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 11篇 |
2013年 | 34篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 6篇 |
2009年 | 15篇 |
2008年 | 14篇 |
2007年 | 32篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 15篇 |
2002年 | 12篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有430条查询结果,搜索用时 21 毫秒
91.
Feres JM Martinez ML Martinez CA Mestriner MA Alzate-Marin AL 《Molecular ecology resources》2009,9(1):434-437
Microsatellite loci that were previously developed in the tropical tree Tabebuia aurea were used for the genetic analysis of Tabebuia roseo-alba populations. Nine of 10 simple sequence repeat markers were amplified, and the polymorphism was assessed in 58 individuals sampled from two stands in southeastern Brazil. All loci were polymorphic with Mendelian inheritance. The allele numbers were high, ranging from 5 to 13 in population I and 3 to 7 in population II, with means of 8.9 and 5.5, respectively. We conclude that these markers can be efficiently used for parentage and gene-flow studies. 相似文献
92.
从长穗桑的茎皮中首次分离到9个Diels—Alder型加合物,通过NMR、MS等波谱分析手段分别鉴定为mulberrofuran K(1),mulberrofuran G(2),guangsangon L(3),kuwanon J(4),kuwanonx(5),guangsangonG(6),guangsangon B(7),guangsangon D(8),kuwanon P(9)。化合物1—9进行了抗氧化活性筛选。结果表明,在10^-5M浓度下,化合物1,2,5—7,9对Fe^2+-半胱氨酸诱导的肝微粒体脂质过氧化产生的丙二醛(malondialdehyde,MDA)有抑制作用(抑制率大于50%)。 相似文献
93.
94.
This paper contains new data on the chemical composition of the essential oil of Lippia alba (Mill.) N. E. Brown, as well as an overview of the available literature. Although the composition of the essential oil of this species is well-documented, discrepancies between the reported results suggest that many chemotypes and morphotypes exist. The analysis of essential oils obtained from the leaves of samples from three different locations in the French Overseas Departments (French Guiana, Martinique, and two different places in Guadeloupe) have shown that the composition of each one is quite different. This new data, along with a review and discussion of published studies, enabled us to establish seven distinct chemotypes. Possible connections between these chemotypes and morphotypes already described were also investigated. 相似文献
95.
Serge D. Muller Takeshi Nakagawa Jacques-Louis de Beaulieu Mona Court-Picon Christopher Carcaillet Cécile Miramont Paul Roiron Clément Boutterin Adam A. Ali Hélène Bruneton 《Journal of Biogeography》2007,34(5):876-899
Aim Previous studies have failed to reconstruct the regional post-glacial migration pattern of Abies alba in southern France. Based on the first exhaustive compilation of palaeoecological data in this region, we present the state-of-the-art and attempt to synthesize the available information concerning glacial refugia and post-glacial migration, and analyse the information with regard to climate and orography.
Location South-western Alps and adjacent areas, southern France.
Methods The work compiles the available palaeoecological data in the south-western Alps (52 sites, 290 radiocarbon dates). The post-glacial migration pattern of Abies alba is reconstructed based on 22 selected palynological analyses (11 well-dated reference sites and 11 supplementary ones).
Results The geographical patterns of approaching area limit, immigration and expansion are reconstructed at the scale of the southern French Alps.
Main conclusions Despite previous assertions, the evidence of refugia in southern France is non-existent. The late-glacial records of fir pollen, previously interpreted in French Mediterranean regions and on adjacent foot-hills as possibly reflecting regional refugia, most probably correspond to reworking phenomena or long-distance pollen transport. Fir migration, originating in the Apennine refugia and through the south-western extremity of the Alps, was extremely rapid in the southern French Alps, only spanning a few centuries between 10,100 and 9800 cal. yr bp . The subsequent spread of fir populations was controlled by local parameters, such as the aridity of the inner valleys, which resulted in a delayed expansion in comparison to other regions. Abies almost disappeared from the south-western Alps during the Roman era, around 2000 cal. yr bp . 相似文献
Location South-western Alps and adjacent areas, southern France.
Methods The work compiles the available palaeoecological data in the south-western Alps (52 sites, 290 radiocarbon dates). The post-glacial migration pattern of Abies alba is reconstructed based on 22 selected palynological analyses (11 well-dated reference sites and 11 supplementary ones).
Results The geographical patterns of approaching area limit, immigration and expansion are reconstructed at the scale of the southern French Alps.
Main conclusions Despite previous assertions, the evidence of refugia in southern France is non-existent. The late-glacial records of fir pollen, previously interpreted in French Mediterranean regions and on adjacent foot-hills as possibly reflecting regional refugia, most probably correspond to reworking phenomena or long-distance pollen transport. Fir migration, originating in the Apennine refugia and through the south-western extremity of the Alps, was extremely rapid in the southern French Alps, only spanning a few centuries between 10,100 and 9800 cal. yr bp . The subsequent spread of fir populations was controlled by local parameters, such as the aridity of the inner valleys, which resulted in a delayed expansion in comparison to other regions. Abies almost disappeared from the south-western Alps during the Roman era, around 2000 cal. yr bp . 相似文献
96.
Five Diels-Alder type adducts, named guangsangons F, G, H, I, and J, along with two known compounds, mulberrofuran J and kuwanon J, were isolated from Morus macroura Miq. Their structures were determined by means of spectroscopic analyses and chemical methods. These compounds were regarded biogenetically as Diels-Alder type adducts of dehydroprenylphenols and chalcone derivatives, and (1)H NMR variable temperature experiments suggested that they all existed as an equilibrium mixture of conformational isomers in solution. Among the isolated new compounds, guangsangons H, I, and J displayed potent antioxidant activities and moderate anti-inflammatory activities. 相似文献
97.
98.
RAMESH K. AGGARWAL D. UDAYKUMAR P. S. HENDRE A. SARKAR LALJ. I. SINGH 《Molecular ecology resources》2004,4(3):477-479
Genetic characterization of germplasm resources is necessary for their effective management and efficient utilization, especially for species like mulberry in which the available germplasm exhibits rich phenotypic diversity with almost no information about its genetic base. Here we present the first report on the isolation of six novel microsatellite markers of mulberry, developed from an enriched genomic library of Morus indica. These markers revealed a high degree of polymorphism (14–26 alleles per locus; polymorphic information content, 0.85–0.90) and a broad cross‐species affinity when tested on a set of 43 elite genotypes including 13 related Morus species. The data thus demonstrate their utility as potentially efficient genetic markers for germplasm characterization, crop improvement and molecular systematics of mulberry. 相似文献
99.
Protoplast donor tissues (leaves of shoots in culture) from a herbaceous plant ( Solanum etuberosum ) and two woody species ( Populus alba × P. grandidentata cv. Crandon and Betula platyphylla szechuanica ) were compared during plasmolysis in a range of osmotic agents and potentials. Cells from both Solanum and Populus , species proven to be amenable to protoplast division and regeneration, plasmolyzed readily at higher osmotic potentials than cells from Betula , a species recalcitrant to prolonged culture after protoplast isolation. Betula leaf mesophyll cells exhibited persistent membrane-to-wall attachments and many failed to plasmolyze even under extreme osmolarity. Although their leaves exhibited similar photosynthetic rates, photosynthetic capacity was lost from Betula protoplasts upon isolation, and retained by Solanum protoplasts. Differential stress after isolation was not detectable through vital staining, but only Solanum and Populus gave both high protoplast yields and high plating efficiencies in continued culture. 相似文献
100.
Alexandre Roulin Heinz Richner Anne-Lyse Ducrest 《Evolution; international journal of organic evolution》1998,52(5):1451-1460
Secondary sexual characters are thought to indicate individual quality. Expression of sex-limited traits in an extravagant state may require both the underlying genes and the available nutrient resources. The assessment of the relative contribution of genes, environment, and body condition is relevant for understanding to that extent the extravagant trait may signal genotypic or phenotypic quality of the individual. In birds, usually only the males are ornamented. In the barn owl, Tyto alba, both females and males display sex-limited plumage traits. Males are commonly lighter colored and females spottier. In an experiment with combined cross-fostering and brood size manipulation we determined the relative contribution of genes, environment, and body condition to the variation in plumage coloration and plumage spottiness. The partial cross-fostering experiment tested the relative importance of shared genes and a shared environment for the resemblance of related birds. Siblings raised in different nests converged toward similar trait values, offspring resembled the true but not the foster parents, and plumage traits of unrelated nestlings sharing the same nest were not correlated. Results were not inflated by maternal effects detectable in the mother's phenotype, because middaughter to mother resemblance was not higher than midson to father resemblance. This suggests that plumage coloration and spottiness are largely genetically inherited traits, and that the rearing environment does not have a strong impact on the expression of these traits. To further investigate whether the two sex-limited traits are condition dependent, brood sizes were manipulated. Enlargement or reduction of broods by two nestlings resulted in lower and higher body mass of nestlings, respectively. However, nestlings raised in enlarged or reduced broods did not show either a significantly darker or lighter or a more or less spotted plumage. We did not detect any genotype-by-environment interaction. In conclusion, simultaneous cross-fostering and brood size manipulation demonstrate that additive genetic variance for plumage coloration and spottiness is maintained and that both the rearing environment and body condition do not account for a large proportion of the phenotypic variance in female and male ornamentations. 相似文献