全文获取类型
收费全文 | 343篇 |
免费 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 8篇 |
2019年 | 2篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 20篇 |
2013年 | 28篇 |
2012年 | 23篇 |
2011年 | 26篇 |
2010年 | 8篇 |
2009年 | 12篇 |
2008年 | 26篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 33篇 |
2003年 | 11篇 |
2002年 | 24篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 1篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有362条查询结果,搜索用时 15 毫秒
61.
Guimarães DO Borges WS Kawano CY Ribeiro PH Goldman GH Nomizo A Thiemann OH Oliva G Lopes NP Pupo MT 《FEMS immunology and medical microbiology》2008,52(1):134-144
A total of 39 endophytic fungi have been isolated from Viguiera arenaria and Tithonia diversifolia, both collected in S?o Paulo State, Brazil. The isolates were identified based on their ribosomal DNA sequences. The ethyl acetate (EtOAc) extracts of all endophytic fungi were evaluated for their antimicrobial, antiparasitic and antitumoral activity. Antimicrobial screening was conducted using an agar diffusion assay against three pathogenic microorganisms: Staphylococcus aureus, Escherichia coli and Candida albicans. Antiparasitic activity was determined by enzymatic inhibition of gGAPDH of Trypanosoma cruzi and adenine phosphorybosiltransferase (APRT) of Leishmania tarentolae. Antitumoral activity was tested against human T leukemia cells by the Mosmann colorimetric method. All extracts showed activity in at least one assay: 79.5% of the extracts were cytotoxic against leukemia cells, 5.1% of the extracts were active against S. aureus, 25.6% against E. coli and 64.1% against Candida albicans. Only one extract showed promising results in the inhibition of parasitic enzymes gGAPDH (95.0%) and three were found to inhibit APRT activity. The cytotoxic extract produced by the strain VA1 (Glomerella cingulata) was fractionated and yielded nectriapyrone and tyrosol. Nectriapyrone showed relevant cytotoxic activity against both human T leukemia and melanoma tumor cell lines. 相似文献
62.
Circulating hematopoietic progenitor cells in runners. 总被引:1,自引:0,他引:1
Maria R Bonsignore Giuseppe Morici Alessandra Santoro Maria Pagano Lucia Cascio Anna Bonanno Pietro Abate Franco Mirabella Mirella Profita Giuseppe Insalaco Maria Gioia A Maurizio Vignola Ignazio Majolino Ugo Testa James C Hogg 《Journal of applied physiology》2002,93(5):1691-1697
Because endurance exercise causes release of mediators and growth factors active on the bone marrow, we asked whether it might affect circulating hematopoietic progenitor cells (HPCs) in amateur runners [n = 16, age: 41.8 +/- 13.5 (SD) yr, training: 93.8 +/- 31.8 km/wk] compared with sedentary controls (n = 9, age: 39.4 +/- 10.2 yr). HPCs, plasma cortisol, interleukin (IL)-6, granulocyte colony-stimulating factor (G-CSF), and the growth factor fms-like tyrosine kinase-3 (flt3)-ligand were measured at rest and after a marathon (M; n = 8) or half-marathon (HM; n = 8). Circulating HPC counts (i.e., CD34(+) cells and their subpopulations) were three- to fourfold higher in runners than in controls at baseline. They were unaffected by HM or M acutely but decreased the morning postrace. Baseline cortisol, flt3-ligand, IL-6, and G-CSF levels were similar in runners and controls. IL-6 and G-CSF increased to higher levels after M compared with HM, whereas cortisol and flt3-ligand increased similarly postrace. Our data suggest that increased HPCs reflect an adaptation response to recurrent, exercise-associated release of neutrophils and stress and inflammatory mediators, indicating modulation of bone marrow activity by habitual running. 相似文献
63.
64.
Carlo Natale Giuseppe Giachello Federica Premoselli Pier Giorgio Montarolo Mirella Ghirardi 《PloS one》2013,8(2)
Epileptic activity is generally induced in experimental models by local application of epileptogenic drugs, including pentylenetetrazol (PTZ), widely used on both vertebrate and invertebrate neurons. Despite the high prevalence of this neurological disorder and the extensive research on it, the cellular and molecular mechanisms underlying epileptogenesis still remain unclear. In this work, we examined PTZ-induced neuronal changes in Helix monosynaptic circuits formed in vitro, as a simpler experimental model to investigate the effects of epileptiform activity on both basal release and post-tetanic potentiation (PTP), a form of short-term plasticity. We observed a significant enhancement of basal synaptic strength, with kinetics resembling those of previously described use-dependent forms of plasticity, determined by changes in estimated quantal parameters, such as the readily releasable pool and the release probability. Moreover, these neurons exhibited a strong reduction in PTP expression and in its decay time constant, suggesting an impairment in the dynamic reorganization of synaptic vesicle pools following prolonged stimulation of synaptic transmission. In order to explain this imbalance, we determined whether epileptic activity is related to the phosphorylation level of synapsin, which is known to modulate synaptic plasticity. Using western blot and immunocytochemical staining we found a PTZ-dependent increase in synapsin phosphorylation at both PKA/CaMKI/IV and MAPK/Erk sites, both of which are important for modulating synaptic plasticity. Taken together, our findings suggest that prolonged epileptiform activity leads to an increase in the synapsin phosphorylation status, thereby contributing to an alteration of synaptic strength in both basal condition and tetanus-induced potentiation. 相似文献
65.
Marcelo Mueller de Freitas Bruno Henrique Sardinha de Souza Luciano Nogueira Mirella Marconato Di Bello Arlindo Leal Boiça Júnior 《Arthropod-Plant Interactions》2018,12(1):85-96
Plants have evolved a diverse array of defensive mechanisms against biotic and abiotic stresses, which can be either constitutive or inducible. Variation in plant-intrinsic factors such as the genotype and the leaf position coupled with insect herbivory can affect the expression of resistance to insects. We investigated if soybean defense induction triggered by Spodoptera cosmioides herbivory varies in function of the genotype and leaf position. This hypothesis was tested in two bioassays using leaf discs or entire leaflets collected from the upper and lower trifoliates of S. cosmioides-injured and uninjured V3-V4 soybean plants. We used one genotype that was constitutively resistant and one that was constitutively susceptible to S. cosmioides based on previous screening. Third-instar larvae were fed one of the treatments and assayed for leaf consumption, larval growth, and efficiency of conversion of ingested food. Genotype and leaf position significantly interacted with herbivory and affected soybean-induced resistance to S. cosmioides. Negative responses on S. cosmioides larvae consumption and growth rates were only observed when leaf material was originated from the upper soybean trifoliate. The susceptible soybean genotype did not exhibit induced resistance characteristics. Food offered as leaf disc was better at demonstrating induced resistance in previously injured soybean, whereas offering entire leaflet the induced effects were less pronounced. Here we provide new findings on soybean resistance by demonstrating that resistance induction to S. cosmioides herbivory is dependent on the plant genotype and leaf position where injury took place, with negative effects better evinced in bioassays using leaf discs than entire leaflets. 相似文献
66.
Marisa Gariglio Guo-Guang Ying Laura Hertel Mirella Gaboli Roger G. Clerc Santo Landolfo 《Experimental cell research》1997,236(2):472
The high-mobility group protein T160 was isolated by screening a phage library from a murine pre-B-cell line L1210. South–Western experiments have previously shown that this protein binds to V-(D)-J recombination signal sequences, suggesting that it may be a sequence-specific DNA-binding protein. However, neither gel-shift nor footprinting analyses have been successfully employed with the T160 protein, despite an extensive effort. In this study, the T160 protein or truncated forms made soluble through denaturing and renaturing cycles in urea were successfully used in gel-shift experiments showing that T160 binds to cruciform or linear duplex DNA with no apparent sequence specificity. Furthermore, fragments longer than 100 bp efficiently formed covalently closed circular monomers in the presence of T160 and T4 DNA ligase, indicating that the protein is capable of introducing bends into the duplex. Last, tissue distribution by Western blotting analysis showed that the T160 protein is expressed in various murine tissues in addition to those of lymphoid origin. Considering its broad evolutionary conservation (from plants to mammals) also, these results suggest that the functional role of the T160 protein is not limited to V-(D)-J recombination, but might be involved in basic processes such as DNA replication and repairing, where irregular DNA structures are generated and very likely recognized by HMG domain proteins. 相似文献
67.
Daniela Virgintino Paul Monaghan David Robertson Mariella Errede Mirella Bertossi Glauco Ambrosi Luisa Roncali 《Journal of molecular histology》1997,29(9):655-660
In this study, astrocytes and microvessels of the human cerebral cortex were analysed morphometrically with the aim of acquiring
quantitative information on the glio-vascular relationships, considered to be of great importance in the formation and functioning
of the blood--brain barrier. Immunohistochemistry for the astrocytic marker, glial fibrillary acidic protein, was used with
a computerized image analysis system. The brain tissue was embedded using the progressive lowering of temperature method,
and the image analyser was applied to semithin sections subjected to immunogold--silver staining and viewed by epipolarization
microscopy. The results show that, in the human cerebral cortex, astrocytes cover 11.4% of the cortex area and that their
perivascular processes are nearly as extensive as the vascular bed (0.8% versus 1.72% of the cortex area). These processes
form a virtually continuous sheath around the vascular walls, only 11% of the vessel perimeter lacking this astrocytic glia
covering. The present results, compared with previous unpublished data obtained by conventional immunocytochemical procedures
on wax sections, indicate that low-temperature methods combined with gold--silver immunolabelling on semithin sections significantly
improve the detection of immunoreactivity and the performance of the image analyser.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
68.
69.
Elder Pupo Behnam A. Baghbaderani Victoria Lugo Julio Fernández Rolando Páez Isis Torréns 《Biotechnology letters》1999,21(12):1119-1123
The streptokinase (SK) gene from S. equisimilis H46A (ATCC 12449) was cloned in E. coli W3110 under the control of the tryptophan promoter. The recombinant SK, which represented 15% of total cell protein content, was found in the soluble fraction of disrupted cells. The solubility of this SK notably differed from that of the product of the SK gene from S. equisimilis (ATCC 9542) which had been cloned in E. coli W3110 by using similar expression vector and cell growth conditions, and occurred in the form of inclusion bodies. 相似文献
70.
Roberto Della Pergola Alessandro Fumagalli Carlo Manassero Mirella Sansoni 《Inorganica chimica acta》2008,361(6):1763-1769
The two clusters [HFe5NiN(CO)14]2− (1) and [HFe4Ni2N(CO)13]2− (2) were obtained by reaction of [Fe4N(CO)12]− and [Ni6(CO)12]2− in refluxing MeCN and EtCN, respectively, along with other Fe-Ni mixed metal clusters. Their solid state structures were determined on the [PPh4]+ salts, and both have an octahedral metal cage, containing an interstitial nitrogen atom. The two Ni atoms in 2 are cis, with a Ni-Ni separation of 2.724(1) Å. The two anions have different stereochemistry of the carbonyl ligands: in 1, five CO’s are semi-bridging, and the remaining nine are terminal; in 2 there are three asymmetric bridging and ten terminal ligands (two for each iron and one for each nickel). The hydride ligands were located in the final difference maps, both bridging a Ni-Fe edge of the clusters but, thanks to the better quality of the diffraction data, the metal-hydrogen distances were refined only in 2. In this cluster, the Fe-H and Ni-H bond lengths are 1.77(2) and 1.79(2) Å, respectively. 相似文献