全文获取类型
收费全文 | 873篇 |
免费 | 49篇 |
出版年
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 33篇 |
2020年 | 16篇 |
2019年 | 30篇 |
2018年 | 35篇 |
2017年 | 32篇 |
2016年 | 35篇 |
2015年 | 70篇 |
2014年 | 64篇 |
2013年 | 72篇 |
2012年 | 67篇 |
2011年 | 68篇 |
2010年 | 25篇 |
2009年 | 38篇 |
2008年 | 64篇 |
2007年 | 31篇 |
2006年 | 38篇 |
2005年 | 34篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 21篇 |
2001年 | 15篇 |
2000年 | 15篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1966年 | 1篇 |
1963年 | 2篇 |
排序方式: 共有922条查询结果,搜索用时 125 毫秒
71.
Marie-Pierre Ledru Maria Luisa Ferraz Salatino Gregorio Ceccantini Antonio Salatino Fabio Pinheiro Jean-Christophe Pintaud 《Diversity & distributions》2007,13(6):761-771
For decades, palynologists working in tropical South America are using the genus Podocarpus as a climate indicator although without referring to any modern data concerning its distribution and limiting factors. With the aim to characterize the modern and past distribution of the southern conifer Podocarpus in Brazil and to obtain new information on the distribution of the Atlantic rainforest during the Quaternary, we examined herbarium data to locate the populations of three Brazilian endemic Podocarpus species: P. sellowii, P. lambertii , and P. brasiliensis , and extracted DNA from fresh leaves from 26 populations. Our conclusions are drawn in the light of the combination of these three disciplines: botany, palynology, and genetics. We find that the modern distribution of endemic Podocarpus populations shows that they are widely dispersed in eastern Brazil, from north to south and reveals that the expansion of Podocarpus recorded in single Amazonian pollen records may have come from either western or eastern populations. Genetic analysis enabled us to delimit regional expansion: between 5° and 15° S grouping northern and central populations of P. sellowii expanded c . 16,000 years ago; between 15° and 23° S populations of either P. lambertii or sellowii expanded at different times since at least the last glaciation; and between 23° and 30° S, P. lambertii appeared during the recent expansion of the Araucaria forest. The combination of botany, pollen, and molecular analysis proved to be a rapid tool for inferring distribution borders for sparse populations and their regional evolution within tropical ecosystems. Today the refugia of rainforest communities we identified are crucial hotspots to allow the Atlantic forest to survive under unfavourable climatic conditions and, as such, offer the only possible opportunity for this type of forest to expand in the event of a future climate change. 相似文献
72.
Photorhabdus luminescens toxin complex (Tc) has been characterized as a potent three-component insecticidal protein complex. Homologues of genes encoding P. luminescens Tc components have been identified in several other enterobacteria and in Gram-positive bacteria, showing these genes are widespread in bacteria. In particular, tc gene homologues have been identified in Yersinia enterocolitica, Yersinia pseudotuberculosis and Yersinia pestis and may have a role in Y. pestis evolution. Y. enterocolitica tc genes have been shown to be active against Manduca sexta larvae. Here, we demonstrate that expression optimization is essential to obtain bioactive P. luminescens Tc proteins and demonstrate that TcaAB and TcdB + TccC are stand-alone toxins against a M. sexta insect model. Moreover, we report that Y. pseudotuberculosis IP32953 Tc proteins are also toxic to M. sexta larvae but do not cross-potentiate as P. luminescens Tc components. 相似文献
73.
The silk gland in Lepidoptera larvae is responsible for the silk production used for shelter or cocoon construction. The secretion of fibroin and sericin by the different silk gland regions are well established. There are few attempts to detect lipid components in the insect silk secretion, although the presence of such element may contribute to the resistance of the shelter to wet environment. This study characterizes the glandular region and detects the presence of lipid components in the secretion of the silk gland of Diatraea saccharalis(Fabricius). The silk gland was submitted to histochemical procedure for lipid detection or conventionally prepared for ultrastructural analyses. Lipid droplets were histochemically detected in both the apical cytoplasm of cell of the anterior region and in the lumen among the microvilli. Ultrastructural analyses of the anterior region showed lipid material, visualized as myelin-like structures within the vesicular Golgi complex and in the apical secretory globules, mixed up with the sericin; similar material was observed into the lumen, adjacent to the microvilli. Lipids were not detected in the cells neither in the lumen of the posterior region. Our results suggest that the silk produced by D. saccharalis has a minor lipid content that is secreted by the anterior region together with the sericin. 相似文献
74.
Martins Renato Tavares de Freitas Silva Rafael Augusto Pinheiro Pinto Valria Arajo Braule Medeiros Adriana Oliveira Brito Laisa Hamada Neusa 《Hydrobiologia》2022,849(16):3531-3544
Hydrobiologia - We used experimental chambers to evaluate the effect of the temperature increasing and microbial conditioning degree on the survival and leaf consumption of two plant species... 相似文献
75.
Rosane Segalla Fábio Pinheiro Gudryan J. Baronio Leonor Patrícia Cerdeira Morellato 《Plant Species Biology》2022,37(1):118-131
Dioecy, a character common to all cycads, requires obligatory outcrossing. The absence of potential reproductive mates of the opposite sex renders individuals effectively sterile. Therefore, reproductive synchrony is essential for the reproductive success of cycads. Here, we describe the reproductive phenology, morphology, and lifespan of strobili of Zamia boliviana (Cycadales, Zamiaceae), an endemic cycad in South America. We examined the variation in timing of maturation between polliniferous and ovuliferous individuals in two Z. boliviana populations. Lifespan of polliniferous and ovuliferous strobili was based on direct observations and systematic measurements of strobili development. Phenological study covered three reproductive cohorts in two distinct cycad populations. Lifespan of polliniferous strobili was comprised of four phases and lasted 50 days until the cycle's completion, while ovuliferous strobili underwent seven phases that extended over 330 days until seed dehiscence. Both sexes produced strobili during the dry season. We identified a seasonally synchronous pattern in the reproductive phenology of Z. boliviana, with a major overlap in the phases of emergence, pollen release, and strobili receptivity between sexes, populations, and subsequent years. Reproductive events of Z. boliviana followed the seasonality of the Cerrado vegetation and climate. Synchrony between the period of strobili production and reproductive activity peaks was found in both sexes, but seed dehiscence occurred in the dry season. Our study provides relevant and new biological data for Z. boliviana in its natural habitat, demonstrating a temporal distinction between the lifespan of polliniferous and ovuliferous strobili and the necessary overlap between the release and receptivity of pollen. 相似文献
76.
Functional diversification of the dehydrin gene family in apple and its contribution to cold acclimation during dormancy
下载免费PDF全文
![点击此处可从《Physiologia plantarum》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Vítor da Silveira Falavigna Yohanna Evelyn Miotto Henrique Pessoa dos Santos Flávio Bello Fialho Márcia Margis‐Pinheiro Giancarlo Pasquali Luís Fernando Revers 《Physiologia plantarum》2015,155(3):315-329
Dehydrins (DHN) are proteins involved in plant adaptive responses to abiotic stresses, mainly dehydration. Several studies in perennial crops have linked bud dormancy progression, a process characterized by the inability to initiate growth from meristems under favorable conditions, with DHN gene expression. However, an in‐depth characterization of DHNs during bud dormancy progression is still missing. An extensive in silico characterization of the apple DHN gene family was performed. Additionally, we used five different experiments that generated samples with different dormancy status, including genotypes with contrasting dormancy traits, to analyze how DHN genes are being regulated during bud dormancy progression in apple by real‐time quantitative polymerase chain reaction (RT‐qPCR). Duplication events took place in the diversification of apple DHN family. Additionally, MdDHN genes presented tissue‐ and bud dormant‐specific expression patterns. Our results indicate that MdDHN genes are highly divergent in function, with overlapping levels, and that their expressions are fine‐tuned by the environment during the dormancy process in apple. 相似文献
77.
Salting Potency and Time‐Intensity Profile of Microparticulated Sodium Chloride in Shoestring Potatoes
下载免费PDF全文
![点击此处可从《Journal of sensory studies》网站下载免费的PDF全文](/ch/ext_images/free.gif)
78.
Direct infusion ESI‐IT‐MSn alkaloid profile and isolation of tetrahydroharman and other alkaloids from Bocageopsis pleiosperma maas (Annonaceae)
下载免费PDF全文
![点击此处可从《Phytochemical analysis : PCA》网站下载免费的PDF全文](/ch/ext_images/free.gif)
79.
80.