全文获取类型
收费全文 | 430篇 |
免费 | 24篇 |
出版年
2022年 | 4篇 |
2021年 | 9篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 17篇 |
2013年 | 44篇 |
2012年 | 25篇 |
2011年 | 20篇 |
2010年 | 21篇 |
2009年 | 19篇 |
2008年 | 22篇 |
2007年 | 30篇 |
2006年 | 18篇 |
2005年 | 20篇 |
2004年 | 25篇 |
2003年 | 23篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有454条查询结果,搜索用时 15 毫秒
71.
Graziella Malandrino Zaira Lipani Roberta G. Toro Maria E. Fragalà 《Inorganica chimica acta》2008,361(14-15):4118-4121
Bi2Mn4O10 films were deposited on SrTiO3 (1 0 0) substrates via metal–organic chemical vapor deposition (MOCVD) from the Bi(phenyl)3 and Mn(tmhd)3 (Htmhd = 2,2,6,6-tetramethyl-3,5-heptanedione) precursors. The films were deposited in the temperature range of 600–800 °C. The X-ray diffraction (XRD) characterization indicates that the Bi2Mn4O10 phase is stable within the investigated range, but the temperature plays a crucial role in determining the out-of-plane orientation of the films. The SEM shows very homogeneous surfaces with a fiber texture morphology at the highest deposition temperature. The AFM data indicate a textured surface with a root mean square roughness of 77.67 nm for films deposited at 800 °C. 相似文献
72.
73.
Scotti C Sommi P Pasquetto MV Cappelletti D Stivala S Mignosi P Savio M Chiarelli LR Valentini G Bolanos-Garcia VM Merrell DS Franchini S Verona ML Bolis C Solcia E Manca R Franciotta D Casasco A Filipazzi P Zardini E Vannini V 《PloS one》2010,5(11):e13892
Helicobacter pylori (H. pylori) is a major human pathogen causing chronic gastritis, peptic ulcer, gastric cancer, and mucosa-associated lymphoid tissue lymphoma. One of the mechanisms whereby it induces damage depends on its interference with proliferation of host tissues. We here describe the discovery of a novel bacterial factor able to inhibit the cell-cycle of exposed cells, both of gastric and non-gastric origin. An integrated approach was adopted to isolate and characterise the molecule from the bacterial culture filtrate produced in a protein-free medium: size-exclusion chromatography, non-reducing gel electrophoresis, mass spectrometry, mutant analysis, recombinant protein expression and enzymatic assays. L-asparaginase was identified as the factor responsible for cell-cycle inhibition of fibroblasts and gastric cell lines. Its effect on cell-cycle was confirmed by inhibitors, a knockout strain and the action of recombinant L-asparaginase on cell lines. Interference with cell-cycle in vitro depended on cell genotype and was related to the expression levels of the concurrent enzyme asparagine synthetase. Bacterial subcellular distribution of L-asparaginase was also analysed along with its immunogenicity. H. pylori L-asparaginase is a novel antigen that functions as a cell-cycle inhibitor of fibroblasts and gastric cell lines. We give evidence supporting a role in the pathogenesis of H. pylori-related diseases and discuss its potential diagnostic application. 相似文献
74.
Monica Cappelletti Pietro Presicce Ma Feiyang Paranthaman Senthamaraikannan Lisa A. Miller Matteo Pellegrini Myung S. Sim Alan H. Jobe Senad Divanovic Sing Sing Way Claire A. Chougnet Suhas G. Kallapur 《PLoS biology》2021,19(9)
Intrauterine infection/inflammation (IUI) is a major contributor to preterm labor (PTL). However, IUI does not invariably cause PTL. We hypothesized that quantitative and qualitative differences in immune response exist in subjects with or without PTL. To define the triggers for PTL, we developed rhesus macaque models of IUI driven by lipopolysaccharide (LPS) or live Escherichia coli. PTL did not occur in LPS challenged rhesus macaques, while E. coli–infected animals frequently delivered preterm. Although LPS and live E. coli both caused immune cell infiltration, E. coli–infected animals showed higher levels of inflammatory mediators, particularly interleukin 6 (IL-6) and prostaglandins, in the chorioamnion-decidua and amniotic fluid (AF). Neutrophil infiltration in the chorio-decidua was a common feature to both LPS and E. coli. However, neutrophilic infiltration and IL6 and PTGS2 expression in the amnion was specifically induced by live E. coli. RNA sequencing (RNA-seq) analysis of fetal membranes revealed that specific pathways involved in augmentation of inflammation including type I interferon (IFN) response, chemotaxis, sumoylation, and iron homeostasis were up-regulated in the E. coli group compared to the LPS group. Our data suggest that the intensity of the host immune response to IUI may determine susceptibility to PTL. 相似文献
75.
Theodore J. Abatzopoulos Francisco Amat Athanasios D. Baxevanis Genuario Belmonte Francisco Hontoria Stefania Maniatsi Salvatore Moscatello Graziella Mura Nickolaj V. Shadrin 《International Review of Hydrobiology》2009,94(5):560-579
Artemia urmiana (a species previously considered endemic of Lake Urmia, NW Iran) has been found in Lake Koyashskoe, a hypersaline lake on the Black Sea coast of the Crimean peninsula (Ukraine). Therefore, this is the first record of A. urmiana in Europe which updates its distribution. The species identification was based on an integrated and interdisciplinary approach using discriminant analysis of the morphometric characters, scanning electron microscopy, and molecular profile analysis. The data derived from the above mentioned approaches converge to significant similarity of the population under investigation with A. urmiana. The updated geographic distribution of the species, deriving from the present report, asks for additional contribution of other disciplines (e.g., avian dispersal of cysts, history of salt trade) to be finally clarified. At present we suggest that the punctuated geographic distribution of A. urmiana is probably linked to its low dispersal capability, and we suppose that its presence in two distant sites could be explained by historical human salt trade between Lake Urmia and the ancient port of Kimmerik, whose remains have been found in the present Lake Koyashskoe. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
76.
The vacuolar and epicuticular flavonoids and the volatiles of the leaves and parts of flower of P. spectabilis Tratt., an endemic species in the Italian Oriental Alps, were investigated. From a MeOH extract of the leaves two flavone glycosides, 8-C-β-glucopyranosylluteolin 7-O-α-arabinofuranoside (1) and 6-C-α-arabinofuranosylapigenin (2) were isolated, in addition to a flavone and three flavonols already known from species of Primula. From an EtOH extract of leaf exudates, 7,3',4'-tri-O-methylquercetin was obtained. The structures were elucidated on the basis of their 1D 1H- and 13C NMR data and 2D NMR techniques, as well as of HPLC-MS. The volatiles emitted by the leaves were mainly constituted by non-terpene derivatives, followed by comparable proportions of hemiterpens, oxygenated monoterpenes and sesquiterpene hydrocarbons. In flowers, monoterpene hydrocarbons were the most represented chemical class followed by non-terpene derivatives. Different proportions of compounds were found when individual parts of flowers were examined separately; calyx produced a greater proportion (approx. 49.5%) of non-terpenes as its volatile metabolites. P. spectabilis has glandular trichomes in the hyaline margins of the epidermal depressions, distributed on the adaxial leaf blade. Glandular hairs were also present on the corolla. Correlations of phytochemical data with the morphological features of leaf, flower and glandular hair are discussed, and a hypothesis is proposed on the ecological roles of the flavonoids and volatile compounds on the general fitness of the species and cross-pollination strategies. 相似文献
77.
Bellia F Vecchio G Cuzzocrea S Calabrese V Rizzarelli E 《Molecular aspects of medicine》2011,32(4-6):258-266
Carnosine (β-alanyl-L-histidine) is a natural dipeptide widely and abundantly distributed in excitable tissues of several animal tissues. Although its physiological role has not been completely understood yet, many beneficial actions have been attributed to carnosine, such as being an antioxidant, antiglycating and ion-chelating agent, a wound healing promoter and a free-radical scavenger. The role of carnosine in the neuroprotection of oxidative stress-driven disorders has been reviewed. The effects of carnosine have been extensively studied both in vivo and in vitro models of cerebral damages, such as neurodegenerative disorders and hypoxia-ischemia injuries. Beside the classical sacrificial agent, carnosine has been reevaluated as a molecular chaperon and an inducer of antioxidant systems in oxidative stress conditions. Thus, beneficial effects on most of the common biochemical events that characterize neurological disorders make carnosine a very promising molecule among all the endogenous compounds in the treatment and/or prevention of oxidative driven diseases. 相似文献
78.
Macchioni L Davidescu M Sciaccaluga M Marchetti C Migliorati G Coaccioli S Roberti R Corazzi L Castigli E 《Journal of bioenergetics and biomembranes》2011,43(5):507-518
Most cancer cells, including GL15 glioblastoma cells, rely on glycolysis for energy supply. The effect of antiglycolytic bromopyruvate
on respiratory parameters and viability of GL15 cells was investigated. Bromopyruvate caused Δψm and MTT collapse, ATP decrease, and cell viability loss without involving apoptotic or necrotic pathways. The autophagy marker
LC3-II was increased. Δψm decrease was accompanied by reactive oxygen species (ROS) increase and cytochrome c (cyt c) disappearance, suggesting a link
between free radical generation and intramitochondrial cyt c degradation. Indeed, the free radical inducer menadione caused
a decrease in cyt c that was reversed by N-acetylcysteine. Cyt c is tightly bound to the inner mitochondrial membrane in GL15
cells, which may confer protein peroxidase activity, resulting in auto-oxidation and protein targeting to degradation in the
presence of ROS. This process is directed towards impairment of the apoptotic cyt c cascade, although cells are committed
to die. 相似文献
79.
Lanza V Bellia F D'Agata R Grasso G Rizzarelli E Vecchio G 《Journal of inorganic biochemistry》2011,105(2):181-188
Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide widely and abundantly distributed in muscle and nervous tissues of several animal species. Many functions have been proposed for this compound, such as antioxidant and metal ion-chelator properties. However, the main limitation on therapeutic use of carnosine on pathologies related to increased oxidative stress and/or metal ion dishomeostasis is associated with the hydrolysis by the specific dipeptidase carnosinase. Several attempts have been made to overcome this limitation. On this basis, we functionalized carnosine and its amide derivative with small sugars such as glucose and lactose. The resistance of these derivatives to the carnosinase hydrolysis was tested and compared with that of carnosine. We found that the glycoconjugation protects the dipeptide moiety from carnosinase hydrolysis, thus potentially improving the availability of carnosine. The copper(II) binding properties of all the new synthesized compounds were investigated by spectroscopic (UV-Visible and circular dichroism) and ESI-MS studies. Particularly, the new family of amide derivatives that are not significantly hydrolyzed by carnosinase is a very promising class of carnosine derivatives. The sugar moiety can act as a recognition element. These new derivatives are potentially able to act as chelating agents in the development of clinical approaches for the regulation of metal homeostasis in the field of medicinal inorganic chemistry. 相似文献
80.
Giuliano Pinna Claudio Pascale Paolo Fornengo Sebastiana Arras Carmela Piras Pietro Panzarasa Gianpaolo Carmosino Orietta Franza Vincenzo Semeraro Salvatore Lenti Susanna Pietrelli Sergio Panzone Christian Bracco Roberto Fiorini Giovanni Rastelli Daniela Bergandi Bruno Zampaglione Roberto Musso Claudio Marengo Giancarlo Santoro Sergio Zamboni Barbara Traversa Maddalena Barattini Graziella Bruno 《PloS one》2014,9(4)
Epidemiological data on the impact of hypertensive crises (emergencies and urgencies) on referral to the Emergency Departments (EDs) are lacking, in spite of the evidence that they may be life-threatening conditions. We performed a multicenter study to identify all patients aged 18 years and over who were admitted to 10 Italian EDs during 2009 for hypertensive crises (systolic blood pressure ≥220 mmHg and/or diastolic blood pressure ≥120 mmHg). We classified patients as affected by either hypertensive emergencies or hypertensive urgencies depending on the presence or the absence of progressive target organ damage, respectively. Logistic regression analysis was then performed to assess variables independently associated with hypertensive emergencies with respect to hypertensive urgencies. Of 333,407 patients admitted to the EDs over the one-year period, 1,546 had hypertensive crises (4.6/1,000, 95% CI 4.4–4.9), and 23% of them had unknown hypertension. Hypertensive emergencies (n = 391, 25.3% of hypertensive crises) were acute pulmonary edema (30.9%), stroke (22.0%,), myocardial infarction (17.9%), acute aortic dissection (7.9%), acute renal failure (5.9%) and hypertensive encephalopathy (4.9%). Men had higher frequency than women of unknown hypertension (27.9% vs 18.5%, p<0.001). Even among known hypertensive patients, a larger proportion of men than women reported not taking anti-hypertensive drug (12.6% among men and 9.4% among women (p<0.001). Compared to women of similar age, men had higher likelihood of having hypertensive emergencies than urgencies (OR = 1.34, 95% CI 1.06–1.70), independently of presenting symptoms, creatinine, smoking habit and known hypertension. This study shows that hypertensive crises involved almost 5 out of 1,000 patients-year admitted to EDs. Sex differences in frequencies of unknown hypertension, compliance to treatment and risk of hypertensive emergencies might have implications for public health programs. 相似文献