全文获取类型
收费全文 | 509篇 |
免费 | 38篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 23篇 |
2014年 | 36篇 |
2013年 | 53篇 |
2012年 | 35篇 |
2011年 | 51篇 |
2010年 | 19篇 |
2009年 | 23篇 |
2008年 | 36篇 |
2007年 | 21篇 |
2006年 | 34篇 |
2005年 | 24篇 |
2004年 | 34篇 |
2003年 | 22篇 |
2002年 | 23篇 |
2001年 | 6篇 |
1999年 | 1篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有547条查询结果,搜索用时 546 毫秒
541.
Maura L. Celli Satoshi Hirata Masaki Tomonaga 《International journal of primatology》2004,25(6):1267-1281
Some tool use in wild chimpanzees is seasonal because they follow the patterns of availability of resources. The type and abundance of vegetation affect the selection of materials used for tools. Besides triggering, does seasonality also shape tool use? We tested the tool performance of 2 chimpanzee groups in a large outdoor compound, enriched with hundreds of plants. We conducted the experiments in 4 seasons to test their behavioural adaptation to the environmental changes. Initially the groups showed preference for different tool materials, one group using grass, abundant in summer, the other using twigs. While twigs were constant through the year, the availability of grass fluctuated greatly, affecting the number of insertions and success of the individuals that used it. Therefore, seasonality did not affect the performance of the group that preferred twigs (less abundant but constant) as it affected the performance of the group that preferred grass (plentiful in certain seasons and scarce in others). We recorded several cases of observation, which may have biased the choices of material. Analysis of the episodes and first insertions of some subjects suggests social transmission, which might explain the initial intergroup difference in tool preference. 相似文献
542.
Silvia Massari Carla Perego Valeria Padovano Anna D'Amico rea Raimondi Maura Francolini Grazia Pietrini 《Traffic (Copenhagen, Denmark)》2009,10(2):246-257
In this study, we examined the role of the L27 [(LIN2-LIN7) domain] and PDZ domain (domain previously found in PSD95-DlgA-ZO-1) for protein–protein interaction of the scaffold protein LIN7 in tight junction (TJ) assembly in Madin–Darby canine kidney (MDCK) cells and found that the stable expression of a LIN7 mutant lacking the L27 domain (ΔL27 mutant) acts as a dominant interfering protein by inhibiting TJ localization of endogenous LIN7. The loss of LIN7 did not alter the localization of the PALS1 (protein associated with LIN7) partner of the L27 domain but prevented TJ localization of the insulin receptor substrate p53 (IRSp53), a partner of the PDZ domain of LIN7. The function of both L27 and PDZ domains of LIN7 in IRSp53 localization to TJs has been further demonstrated by reducing the expression of LIN7 (LIN7 small hairpin RNA experiments) and by expression of IRSp53 deleted of its motif for PDZ interaction (IRSp53Δ5) or fused to the L27 domain of LIN7 (L27-IRSp53Δ5). Cell lines with decreased localization of LIN7 and IRSp53 to TJs showed defects during assembly of TJs and cyst polarization and failed to activate Rac1, a member of the Rho guanosine triphosphatases family crucially involved in actin organization and orientation of apicobasal polarity. These data therefore indicate that LIN7–IRSp53 association plays a role during assembly of functional TJs and surface polarization in epithelial cells. 相似文献
543.
544.
Alexsandro S. Galdino Cirano J. Ulhoa Lídia Maria P. Moraes Maura V. Prates Carlos Bloch Jr & Fernando A.G. Torres 《FEMS microbiology letters》2008,280(2):189-194
A Cryptococcus flavus gene ( AMY1 ) encoding an extracellular α-amylase has been cloned. The nucleotide sequence of the cDNA revealed an ORF of 1896 bp encoding for a 631 amino acid polypeptide with high sequence identity with a homologous protein isolated from Cryptococcus sp. S-2. The presence of four conserved signature regions, (I) 144 DVVVNH149 , (II) 235 GLRIDSLQQ243 , (III) 263 GEVFN267 , (IV) 327 FLENQD332 , placed the enzyme in the GH13 α-amylase family. Furthermore, sequence comparison suggests that the C. flavus α-amylase has a C-terminal starch-binding domain characteristic of the CBM20 family. AMY1 was successfully expressed in Saccharomyces cerevisiae . The time course of amylase secretion in S. cerevisiae resulted in a maximal extracellular amylolytic activity (3.93 U mL−1 ) at 60 h of incubation. The recombinant protein had an apparent molecular mass similar to the native enzyme ( c . 67 kDa), part of which was due to N-glycosylation. 相似文献
545.
Massimo Aureli Maura Samarani Nicoletta Loberto Elena Chiricozzi Laura Mauri Sara Grassi Domitilla Schiumarini Alessandro Prinetti Sandro Sonnino 《Glycoconjugate journal》2018,35(4):397-402
Sphingolipid metabolism is an intricate network of several interdependent and co-regulated pathways. In addition to the mainstream biosynthetic and catabolic pathways, several processes, even if less important in contributing to the final tissue sphingolipid composition from the quantitative point of view, might become relevant when sphingolipid metabolism is for any reason dysregulated and concur to the onset of neuronal pathologies. The main subcellular sites involved in the mainstream metabolic pathway are represented by the Golgi apparatus (for the biosynthesis) and by the lysosomes (for catabolism). On the other hand, the minor collateral pathways are associated with the plasma membrane and membranes of other organelles, and likely play important roles in the local regulation of membrane dynamics and contribute to maintain a perfect membrane organization functional to the physiology of the cell. In this review, we will consider few aspects of the sphingolipid metabolic pathway depending by the dynamic of the membranes that seems to become relevant in neurodegenerative diseases. 相似文献
546.
Silas P. Rodrigues Maura Da Cunha José A. Ventura Patricia Machado Bueno Fernandes 《Plant cell reports》2009,28(5):861-871
Spontaneous latex exudation is the main symptom of papaya sticky (meleira) disease caused by the Papaya meleira virus (PMeV), a double-stranded RNA (dsRNA) virus. This paper describes different effects of PMeV on papaya latex. Latex samples
were subjected to different histochemical tests to evaluate their chemical composition. Additionally, the integrity of the
latex particles was assessed by transmission and scanning electron microscopy analysis. Biochemical and micro- and macro-element
measurements were performed. PMeV dsRNA extraction was performed to evaluate the interaction of the virus with the latex particles.
Sticky diseased latex was positive for alkaloid biosynthesis and showed an accumulation of calcium oxalate crystals. PMeV
also increased H2O2 synthesis within sticky diseased laticifers. The protein, sugar and water levels were altered, probably due to chemical changes.
The morphology of the latex particles was further altered; PMeV particles seemed to be bound to the latex particles. The alkaloid
and H2O2 biosynthesis in the papaya laticifers indicate a papaya defense response against PMeV. However, such efforts failed, as the
virus affected the plant latex. The effects described here suggest some advantages of the infection process, including facilitating
the movement of the virus within the papaya plant. 相似文献
547.
Kathlyn Vasconcelos Gevú Maura Da Cunha Claudia Franca Barros Sabrina Magna Pereira Helena Regina Pinto Lima 《Plant Systematics and Evolution》2014,300(5):1089-1098
Xylem structural characteristics are rarely used to separate tribes. This study aims to characterize the morphology of subterranean organs and determine both the occurrence and distribution of the vessel elements in ten species, belonging to Alpinieae and Zingibereae tribes. Species were from protected areas in the Brazilian Atlantic Rain Forest or from private cultivation areas. Roots and rhizomes processing followed both light and scanning electron microscopy procedures. According to morphological and anatomical characteristics, Euclidean distances among taxa were calculated, resulting in a dendrogram based on the unweighted pair group method with arithmetic mean (UPGMA) clustering. Despite our results indicating a similarity among all the species studied, they could be segregated by using qualitative and special metabolites characters in both the rhizome and the root. Vessel elements were found to be confined to the roots, presenting several basal characters in most of species, except for Alpinia purpurata and Etlingera species. 相似文献