全文获取类型
收费全文 | 537篇 |
免费 | 51篇 |
出版年
2023年 | 5篇 |
2022年 | 9篇 |
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 15篇 |
2017年 | 27篇 |
2016年 | 24篇 |
2015年 | 25篇 |
2014年 | 29篇 |
2013年 | 38篇 |
2012年 | 42篇 |
2011年 | 33篇 |
2010年 | 31篇 |
2009年 | 31篇 |
2008年 | 28篇 |
2007年 | 28篇 |
2006年 | 22篇 |
2005年 | 23篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1993年 | 1篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 4篇 |
1966年 | 1篇 |
排序方式: 共有588条查询结果,搜索用时 46 毫秒
31.
Soghomonyan S Hajitou A Rangel R Trepel M Pasqualini R Arap W Gelovani JG Alauddin MM 《Nature protocols》2007,2(2):416-423
Non-invasive imaging of transgene expression requires the appropriate combination of a reporter gene and a reporter probe. [18F]FEAU positron emission tomography (PET) is used for the assessment of herpes simplex virus type-1 thymidine kinase gene expression. Hybrid AAV phage (termed AAVP) can be adapted to transduce mammalian cells by targeting to a specific receptor. We evaluated a targeted AAVP vector using [18F]FEAU PET. This protocol describes [18F]FEAU production and dosing, micro-PET imaging and image analysis. 2-Deoxy-2-trifluoromethanesulfonyl-1,3,5-tri-O-benzoyl-alpha-D-ribofuranose is radio-fluorinated, converted into its 1-bromo derivative and coupled with protected 5-ethyl uracil. The coupled product is hydrolyzed and purified using HPLC. Tumor-bearing animals targeted with either retroviral or AAVP vectors are anesthetized and injected with [18F]FEAU (0.1 mCi per mouse); this is followed 2 h after injection by imaging on a micro-PET. Production of [18F]FEAU requires approximately 3.5 h from the end of bombardment. PET imaging studies require 2-3 h (depending on the number of animals) after synthesis of [18F]FEAU. 相似文献
32.
Bruno de Souza Gonçalves Jéssica M. de Moura Valadares Silmara L. G. Alves Simone C. Silva Luciana P. Rangel Vanessa F. Cortes José A. F. P. Villar Leandro A. Barbosa Hérica de Lima Santos 《Journal of cellular biochemistry》2019,120(10):17108-17122
Recently, cardiotonic steroids (CTS) have been shown to lead to the activation of Na,K-ATPase at low concentrations in brain, promoting neuroprotection against ischemia. We report here the results of the use of digoxin and its semisynthetic derivatives BD-14, BD-15, and BD-16 against partial chemical ischemic induction followed by reperfusion in murine neuroblastoma cells neuro-2a (N2a). For chemical ischemic induction, sodium azide (5 mM) was used for 5 hours, and then reperfusion was induced for 24 hours. Na,K-ATPase activity and protein levels were analyzed in membrane preparation of N2a cells pretreated with the compounds (150 nM), in the controls and in induced chemical ischemia. In the Na,K-ATPase activity and protein levels assays, the steroids digoxin and BD-15 demonstrated a capacity to modulate the activity of the enzyme directly, increasing its levels of expression and activity. Oxidative parameters, such as superoxide dismutase (SOD) activity, lipid peroxidation (thiobarbituric acid reactive substance), glutathione peroxidase (GPx), glutathione (GSH) levels, hydrogen peroxide content, and the amount of free radicals (reactive oxygen species) during induced chemical ischemia were also evaluated. Regarding the redox state, lipid peroxidation, hydrogen peroxide content, and GPx activity, we have observed an increase in the chemical ischemic group, and a reduction in the groups treated with CTS. SOD activity increased in all treated groups when compared to control and GSH levels decreased when treated with sodium azide and did not change with CTS treatments. Regarding the lipid profile, we saw a decrease in the content of phospholipids and cholesterol in the chemical ischemic group, and an increase in the groups treated with CTS. In conclusion, the compounds used in this study demonstrate promising results, since they appear to promote neuroprotection in cells exposed to chemical ischemia. 相似文献
33.
Enrico Ceccarelli Ariadna Rangel Negrín Alejandro Coyohua-Fuentes Domingo Canales-Espinosa Pedro Américo D. Dias 《American journal of primatology》2020,82(2):e23099
Benefits of group life depend in large part on whether animals remain cohesive, which often requires collective decisions about where and when to move. During a group movement, the leader may be considered as the individual occupying the vanguard position of the group progression, when its movement evokes following by other group members. In nondespotic societies, individuals with greater incentives to move frequently are leaders. During 15 months of observations (1,712 contact hours), we investigated two mantled howler monkey (Alouatta palliata) groups at La Flor de Catemaco (Los Tuxtlas, Mexico) to examine whether sex and female reproductive state influenced leadership likelihood in two contexts: movements toward feeding trees; movements associated with loud calls, a group-defense behavior used by males of this genus. Females led and occupied forward positions during group movements toward feeding trees more often than adult males. Adult females led these movements more frequently when they were gestating than when they were lactating or cycling. There were no differences between sexes in the leadership of group movements associated with loud calls. Leadership by gestating females is perhaps the result of their higher nutritional/energetic needs when compared with cycling females, and of their greater mobility when compared with lactating females carrying dependent offspring. Female leadership during movements toward feeding trees may be a mechanism to optimize access to food resources in mantled howler monkeys. 相似文献
34.
Rangel LB Malaquias AT Lara LS Silva IV De Souza AM Lopes AG Caruso-Neves C 《Biochimica et biophysica acta》2001,1512(1):90-97
This study describes the modulation of the ouabain-insensitive Na(+)-ATPase activity from renal proximal tubule basolateral membranes (BLM) by protein kinase C (PKC). Two PKC isoforms were identified in BLM, one of 75 kDa and the other of 135 kDa. The former correlates with the PKC isoforms described in the literature but the latter seems to be a novel isoform, not yet identified. Both PKC isoforms of BLM are functional since a protein kinase C activator, TPA, increased the total hydroxylamine-resistant 32P(i) incorporation from [gamma-32P]ATP into the BLM. In parallel, TPA stimulated the Na(+)-ATPase activity from BLM in a dose-dependent manner, the effect being reversed by the PKC inhibitor sphingosine. The stimulatory effect of TPA on Na(+)-ATPase involved an increase in the V(max) (from 13.4+/-0.6 nmol P(i) mg(-1) min(-1) to 25.2+/-1.4 nmol P(i) mg(-1) min(-1), in the presence of TPA, P<0.05) but did not change the apparent affinity for Na(+) (K(0.5)=14.5+/-2.1 mM in control and 10.0+/-2.1 mM in the presence of TPA, P>0.07). PKC involvement was further confirmed by stimulation of the Na(+)-ATPase activity by the catalytic subunit of PKC (PKC-M). Finally, the phosphorylation of an approx. 100 kDa protein in the BLM (the suggested molecular mass of Na(+)-ATPase [1]) was induced by TPA. Taken together, these findings indicate that PKCs resident in BLM stimulate Na(+)-ATPase activity which could represent an important mechanism of regulation of proximal tubule Na(+) reabsorption. 相似文献
35.
Drosophila perlecan modulates FGF and hedgehog signals to activate neural stem cell division 总被引:3,自引:0,他引:3
Park Y Rangel C Reynolds MM Caldwell MC Johns M Nayak M Welsh CJ McDermott S Datta S 《Developmental biology》2003,253(2):247-257
Mutations in the Drosophila trol gene cause cell cycle arrest of neuroblasts in the larval brain. Here, we show that trol encodes the Drosophila homolog of Perlecan and regulates neuroblast division by modulating both FGF and Hh signaling. Addition of human FGF-2 to trol mutant brains in culture rescues the trol proliferation phenotype, while addition of a MAPK inhibitor causes cell cycle arrest of the regulated neuroblasts in wildtype brains. Like FGF, Hh activates stem cell division in the larval brain in a Trol-dependent fashion. Coimmunoprecipitation studies are consistent with interactions between Trol and Hh and between mammalian Perlecan and Shh that are not competed with heparin sulfate. Finally, analyses of mutations in trol, hh, and ttv suggest that Trol affects Hh movement. These results indicate that Trol can mediate signaling through both of the FGF and Hedgehog pathways to control the onset of stem cell proliferation in the developing nervous system. 相似文献
36.
Souza NA Andrade-Coêlho CA Vilela ML Rangel EF 《Memórias do Instituto Oswaldo Cruz》2001,96(3):319-324
During two consecutive years, studies on the sand fly fauna in Po?o das Antas and Fazenda Bom Retiro, two Atlantic Rain Forest Reserves from the State of Rio de Janeiro, were performed using Shannon traps, CDC light traps and human bait collections. Eleven species were identified; Lutzomyia longipalpis, L. migonei, L. edwardsi, L. intermedia, L. whitmani, L. fischeri, L. shannoni, L. ayrozai, L. hirsuta, L. monticola and L. misionensis (first occurrence in the State of Rio de Janeiro). L. intermedia and L. whitmani were the predominant anthropophilic species around houses, while L. hirsuta predominated in the forest. 相似文献
37.
38.
We evaluated the effects of exposure to doses supplied at an environmentally realistic intensity of UV-B radiation (800 mW m(-2) weighted irradiance) on the culturability and germination of selected strains of the entomopathogenic Hyphomycetes Verticillium lecanii and Aphanocladium album. Increased UV-B exposure decreased relative percent culturability for all strains. Four hours of exposure to UV-B were sufficient to reduce the culturability close to zero. The LT(50) (50% lethal time) ranged from 120 ± 5 min for the V. lecanii strain ARSEF 6430 to 86 ± 14 min for the A. album strain ARSEF 6433. A strong delay in the germination of surviving conidia was observed. To determine the occurrence of photoreactivation in these two genera, we evaluated the effect of exposure to visible light after exposure to UV-B radiation. There was no significant difference in relative culturability between conidia exposed to visible light after UV-B exposure compared to those incubated in the dark after UV-B exposure. This indicates that photoreactivation, if it occurs, must have limited importance in the repair of the damage induced by UV-B radiation in these two genera. 相似文献
39.
Ramírez-López E Corona-Hernández J Dendooven L Rangel P Thalasso F 《Bioresource technology》2003,88(3):259-263
Biofiltration is the most commonly used biological gas treatment technology and is extensively used for the treatment of polluted air with gas flow rates of up to 2 x 10(5) m(3)/h. It involves a filter bed of organic matter serving both as carrier for microorganisms and as nutrient supplier. Polluted gas passes through the filter bed and is cleaned by biological activity. Biofiltration is not being developed in Latin America as in the USA, Canada or Europe; the main reason probably being the absence of specific technology and of potential organic carriers locally available. Five different agriculture by-products available in Latin America: peanut shells, rice husk, coconut shells, cane bagasse and maize stubble, were chemically, physically and structurally characterized for their potential use as biofilter carrier. It was found that peanut shells could be used as biofilter carrier and therefore would have potential biological application. 相似文献
40.
Caruso-Neves C Lara LS Rangel LB Grossi AL Lopes AG 《Biochimica et biophysica acta》2000,1467(1):189-197
Angiotensin-(1-7) (Ang-(1-7)) modulates the Na+-ATPase, but not the Na+,K+-ATPase activity present in pig kidney proximal tubules. The Na+-ATPase, insensitive to ouabain, but sensitive to furosemide, is stimulated by Ang-(1-7) (68% by 10(-9) M), in a dose-dependent manner. This effect is due to an increase in Vmax, while the apparent affinity of the enzyme for Na+ is not modified. Saralasin, a general angiotensin receptor antagonist, abolishes the stimulation, demonstrating that the Ang-(1-7) effect is mediated by receptor. The Ang-(1-7) stimulatory effect is not changed by either PD 123319, an AT2 receptor antagonist, or A779, an Ang-(1-7) receptor antagonist. On the other hand, increasing the concentration of the AT1 receptor antagonist losartan from 10(-11) to 10(-9) M, reverses the Ang(1-7) stimulation completely. A further increase to 10(-3) M losartan reverses the Na+-ATPase activity to a level similar to that obtained with Ang-(1-7) (10(-9) M) alone. The stimulatory effect of Ang-(1-7) at 10(-9) M is similar to the effect of angiotensin II (AG II) alone. However, when the two peptides are both present, Na+-ATPase activity is restored to control values. These data suggest that Ang-(1-7) selectively modulates the Na+-ATPase activity present in basolateral membranes of kidney proximal tubules through a losartan-sensitive receptor. This receptor is probably different from the receptor involved in the stimulation of the Na+-ATPase activity by angiotensin II. 相似文献