全文获取类型
收费全文 | 655篇 |
免费 | 37篇 |
出版年
2023年 | 5篇 |
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 13篇 |
2015年 | 13篇 |
2014年 | 31篇 |
2013年 | 46篇 |
2012年 | 42篇 |
2011年 | 46篇 |
2010年 | 24篇 |
2009年 | 18篇 |
2008年 | 31篇 |
2007年 | 32篇 |
2006年 | 25篇 |
2005年 | 20篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1994年 | 6篇 |
1992年 | 6篇 |
1991年 | 15篇 |
1990年 | 9篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 9篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 11篇 |
1971年 | 7篇 |
1970年 | 16篇 |
1969年 | 4篇 |
1968年 | 4篇 |
1967年 | 5篇 |
1965年 | 6篇 |
排序方式: 共有692条查询结果,搜索用时 296 毫秒
111.
Michela Papa Virginia Boccardi Raffaele Prestano Edith Angellotti Manuela Desiderio Luigi Marano Maria Rosaria Rizzo Giuseppe Paolisso 《PloS one》2014,9(4)
Previous studies identified comorbidities as predictors of older driver performance and driving pattern, while the direct impact of comorbidities on road crash risk in elderly drivers is still unknown. The present study is a cross-sectional aimed at investigating the association between levels of comorbidity and crash involvement in adult and elderly drivers. 327 drivers were stratified according to age range in two groups: elderly drivers (age ≥70 years old, referred as older) and adult drivers (age <70 years old, referred as younger). Driving information was obtained through a driving questionnaire. Distance traveled was categorized into low, medium and high on the basis of kilometers driven in a year. CIRS-illness severity (IS) and CIRS-comorbidity indices (CI) in all populations were calculated. Older drivers had a significantly higher crash involvements rate (p = .045) compared with the younger group based on the number of licensed drivers. Dividing comorbidity indices into tertiles among all licensed subjects, the number of current drivers significantly decreased (p<.0001) with increasing level of comorbidity. The number of current drivers among older subjects significantly decreased with increasing comorbidity level (p = .026) while no difference among younger group was found (p = .462). Among younger drivers with increasing comorbidity level, the number of road accidents significantly increased (p = .048) and the logistic regression analysis showed that comorbidity level significantly associated with crash involvement independent of gender and driving exposure. Older subjects with high level of comorbidity are able to self-regulate driving while comorbidity burden represents a significant risk factor for crash involvements among younger drivers. 相似文献
112.
Laura Viviana Fornasero María Florencia Del Papa José Luis López Francisco Javier Albicoro Juan Marcelo Zabala María Antonieta Toniutti José Francisco Pensiero Antonio Lagares 《PloS one》2014,9(8)
Desmanthus paspalaceus (Lindm.) Burkart belongs to the D. virgatus complex, subfamily Mimosoidae. The known potential as livestock fodder of several of these legumes prompted us to undertake a phenotypic, molecular, and symbiotic characterization of the D. paspalaceus symbionts in the Santa Fe province, Argentina. The rhizobia collected—containing isolates with different abiotic-stress tolerances—showed a remarkable genetic diversity by PCR fingerprinting, with 11 different amplification profiles present among 20 isolates. In selected isolates 16S-rDNA sequencing detected mesorhizobia (60%) and rhizobia (40%) within the collection, in contrast to the genus of the original inoculant strain CB3126—previously isolated from Leucaena leucocephala—that we typified here through its 16S rDNA as Sinorhizobium terangae. The results revealed the establishment by diverse bacterial genera -rhizobia, sinorhizobia, and mesorhizobia- of full N2-fixing symbiotic associations with D. paspalaceus. This diversity was paralleled by the presence of at least two different nodC allelic variants. The identical nodC alleles of the Mesorhizobia sp. 10.L.4.2 and 10.L.5.3 notably failed to group within any of the currently described rhizo-/brady-/azorhizobial nodC clades. Interestingly, the nodC from S. terangae CB3126 clustered close to homologs from common bean nodulating rhizobia, but not with the nodC from S. terangae WSM1721 that nodulates Acacia. No previous data were available on nod-gene phylogeny for Desmanthus symbionts. A field assay indicated that inoculation of D. paspalaceus with the local Rhizobium sp. 10L.11.4 produced higher aerial-plant dry weights compared to S. teranga CB3126–inoculated plants. Neither the mesorhizobia 10.L.4.2 or 10.L.5.3 nor the rhizobium 10L.11.4 induced root nodules in L. leucocephala or P. vulgaris. The results show that some of the local isolates have remarkable tolerances to several abiotic stresses including acidity, salt, and temperature; while exhibiting prominent N2 fixation; thus indicating suitability as candidates for inoculation of D. paspalaceus. 相似文献
113.
Luena Papa Mary Hahn Ellen L. Marsh Bradley S. Evans Doris Germain 《The Journal of biological chemistry》2014,289(9):5412-5416
Cancer cells are characterized by elevated levels of reactive oxygen species, which are produced mainly by the mitochondria. The dismutase SOD2 localizes in the matrix and is a major antioxidant. The activity of SOD2 is regulated by the deacetylase SIRT3. Recent studies indicated that SIRT3 is decreased in 87% of breast cancers, implying that the activity of SOD2 is compromised. The resulting elevation in reactive oxygen species was shown to be essential for the metabolic reprograming toward glycolysis. Here, we show that SOD2 itself is down-regulated in breast cancer cell lines. Further, activation of oncogenes, such as Ras, promotes the rapid down-regulation of SOD2. Because in the absence of SOD2, superoxide levels are elevated in the matrix, we reasoned that mechanisms must exist to retain low levels of superoxide in other cellular compartments especially in the intermembrane space of the mitochondrial to avoid irreversible damage. The dismutase SOD1 also acts as an antioxidant, but it localizes to the cytoplasm and the intermembrane space of the mitochondria. We report here that loss of SOD2 correlates with the overexpression of SOD1. Further, we show that mitochondrial SOD1 is the main dismutase activity in breast cancer cells but not in non-transformed cells. In addition, we show that the SOD1 inhibitor LCS-1 leads to a drastic fragmentation and swelling of the matrix, suggesting that in the absence of SOD2, SOD1 is required to maintain the integrity of the organelle. We propose that by analogy to the cadherin switch during epithelial-mesenchymal transition, cancer cells also undergo a SOD switch during transformation. 相似文献
114.
Gabriela Vaz Meirelles Arina Marina Perez Edmárcia Elisa de Souza Ferna Luisa Basei Priscila Ferreira Papa Talita Diniz Melo Hanchuk Vanessa Bomfim Cardoso Jrg Kobarg 《World journal of biological chemistry》2014,5(2):141-160
Aside from Polo and Aurora, a third but less studied kinase family involved in mitosis regulation is the never in mitosis-gene A(NIMA)-related kinases(Neks). The founding member of this family is the sole member NIMA of Aspergillus nidulans, which is crucial for the initiation of mitosis in that organism. All 11 human Neks have been functionally assigned to one of the three core functions established for this family in mammals:(1) centrioles/mitosis;(2) primary ciliary function/ciliopathies; and(3) DNA damage response(DDR). Recent findings, especially on Nek 1 and 8, showed however, that several Neks participate in parallel in at least two of these contexts: primary ciliary function and DDR. In the core section of this in-depth review, we report the current detailed functional knowledge on each of the 11 Neks. In the discussion, we return to the cross-connections among Neks and point out how our and other groups' functional and interactomics studies revealed that most Neks interact with protein partners associated with two if not all three of the functional contexts. We then raise the hypothesis that Neks may be the connecting regulatory elements that allow the cell to fine tune and synchronize the cellular events associated with these three core functions. The new and exciting findings on the Nek family open new perspectives and should allow the Neks to finally claim the attention they deserve in the field of kinases and cell cycle biology. 相似文献
115.
S. Papa A. Pellegrino G. Bartoli R. Ruosi S. Rianna A. Fuggi 《Plant biosystems》2013,147(6):1187-1198
The aim of this study was to analyse the amount and qualitative characteristics of organic matter (OM) in the litter horizon (considering leaf litter at different decomposition stages) and underlying soil to a 30-cm depth in a beech stand on the Apennines in southern Italy. Distribution of major nutrients as well as fungal and microbial biomass were also evaluated, in addition to beech leaf nutrient content monitor from full expansion to abscission in order to estimate annual nutrient input to soil from litterfall and nutrient retranslocation before abscission. OM was significantly higher in leaf litter. C/N ratio and the Na, Mn, Fe levels also decreased along the decomposition continuum, whereas N and S contents slowly decreased with soil depth. Generally, leaf nutrient content was also significantly lower in dead leaves, indicating efficient retranslocation to persistent organs. Fungal biomass was the highest in leaf layers, with no significant changes between spring and autumn samplings. Enzyme activities did not differ significantly along the decomposition continuum but marked decreases were found in the upper soil layer; these remained relatively constant, with the exception of laccase, at deeper soil depths. No seasonal effect on enzyme activities and OM content was found. 相似文献
116.
Luchetti F Canonico B Della Felice M Burattini S Battistelli M Papa S Falcieri E 《Histology and histopathology》2003,18(4):1041-1052
Hyperthermia is a known apoptotic inducer and has been recently utilized in combination with chemo-and/or radiotherapy in cancer treatment. In this study we have described its effect on SK-N-MC human neuroblastoma tumor cells, a line which grows as a double adherent and floating population. Considering this particular culture behavior, we also investigated the relationship between hyperthermia and cell adhesiveness by evaluating integrin expression, namely CD11a, which is, as known, closely correlated to cell adhesion properties. By a multiple, ultrastructural and flow cytometrical approach, we have demonstrated that hyperthermia, while triggering apoptosis, also determines a CD11a surface expression decrease in apoptotic and living cells. We thus suggest a further role for this treatment, which, affecting adhesion mechanisms, could down-regulate metastatic diffusion. 相似文献
117.
Evangelisti C Bortul R Tabellini G Papa V Cocco L Martelli AM 《European journal of histochemistry : EJH》2006,50(1):9-13
The existence of intranuclear lipid-dependent signal transduction systems has been demonstrated by several independent groups. Remarkably, intranuclear lipid-dependent signal transduction pathways are regulated independently from their membrane/cytosolic counterparts. A sizable body of evidence suggests that nuclear lipid signaling controls critical biological functions such as cell proliferation, differentiation, and apoptosis. Diacylglycerol (DG) is a fundamental lipid second messenger which is produced in the nucleus. Since the levels of nuclear DG fluctuate during the cell cycle progression, it has been suggested that this lipid second messenger has important regulatory roles. Most likely, nuclear DG serves as a chemoattractant for some isoforms of protein kinase C that migrate to the nucleus in response to a variety of agonists. The nucleus also contains diacylglycerol kinases (DGKs), i.e. the enzymes that, by converting DG into phosphatidic acid (PA), terminate DG-dependent events. This review aims at highlighting the different isozymes of DGKs present within the nucleus as well as at discussing their potential functions with particular emphasis placed on DNA replication. 相似文献
118.
Mariani E Roda P Mariani AR Vitale M Degrassi A Papa S Manzoli FA Facchini A 《Cytotechnology》1987,1(1):103-105
Old subjects exhibit a decline in circulating T cells and an impaired proliferative response to mitogens, plus a relative increase in cells with NK phenotype not associated with a concomitant increase in their cytolitic activity.In the present study a limiting dilution assay was used to evaluate the phenotype, the functional activity and the proliferative capacity of clones obtained from peripheral blood lymphocytes of old and young subjects. CD5+ CD8+ clones from old people showed a significant impairment in their proliferative capacity and a decreased lytic activity against K562 and P815-IgG cell lines. 相似文献
119.
120.