全文获取类型
收费全文 | 1669篇 |
免费 | 97篇 |
国内免费 | 15篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 36篇 |
妇产科学 | 74篇 |
基础医学 | 181篇 |
口腔科学 | 33篇 |
临床医学 | 142篇 |
内科学 | 474篇 |
皮肤病学 | 26篇 |
神经病学 | 172篇 |
特种医学 | 44篇 |
外科学 | 134篇 |
综合类 | 4篇 |
预防医学 | 90篇 |
眼科学 | 16篇 |
药学 | 201篇 |
中国医学 | 7篇 |
肿瘤学 | 139篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 38篇 |
2021年 | 56篇 |
2020年 | 33篇 |
2019年 | 47篇 |
2018年 | 53篇 |
2017年 | 43篇 |
2016年 | 49篇 |
2015年 | 68篇 |
2014年 | 71篇 |
2013年 | 86篇 |
2012年 | 140篇 |
2011年 | 135篇 |
2010年 | 70篇 |
2009年 | 55篇 |
2008年 | 97篇 |
2007年 | 108篇 |
2006年 | 98篇 |
2005年 | 109篇 |
2004年 | 72篇 |
2003年 | 97篇 |
2002年 | 74篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 5篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1979年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有1781条查询结果,搜索用时 15 毫秒
51.
Enhancer blocking activity located near the 3′ end of the sea urchin early H2A histone gene 下载免费PDF全文
Franco Palla Raffaella Melfi Letizia Anello Maria Di Bernardo Giovanni Spinelli 《Proceedings of the National Academy of Sciences of the United States of America》1997,94(6):2272-2277
The sea urchin early histone repeating unit contains one copy of each of the five histone genes whose coordinate expression during development is regulated by gene-specific elements. To learn how within the histone repeating unit a gene-specific activator can be prevented to communicate with the heterologous promoters, we searched for domain boundaries by using the enhancer blocking assay. We focused on the region near the 3′ end of the H2A gene where stage-specific nuclease cleavage sites appear upon silencing of the early histone genes. We demonstrated that a DNA fragment of 265 bp in length, defined as sns (for silencing nucleoprotein structure), blocked the enhancer activity of the H2A modulator in microinjected sea urchin embryos only when placed between the enhancer elements and the promoter. We also found that sns silenced the modulator elements even when placed at 2.7 kb from the promoter. By contrast, the enhancer activity of the modulator sequences, located downstream to the coding region, was not affected when sns was positioned in close proximity to the promoter. Finally, the H2A sns fragment placed between the simian virus 40 regulative region and the tk promoter repressed chloramphenicol acetyltransferase expression in transfected human cell lines. We conclude that 3′ end of the H2A gene contains sequence elements that behave as functional barriers of enhancer function in the enhancer blocking assay. Furthermore, our results also indicate that the enhancer blocking function of sns lacks enhancer and species specificity and that it can act in transient assays. 相似文献
52.
Anna Maria Ferraris Letizia Canepa Cecilia Melani Maurizio Miglino Giorgio Broccia Gian Franco Gaetani 《British journal of haematology》1989,73(1):48-50
Philadelphia (Ph) chromosome-positive chronic myelogenous leukaemia (CML) was studied in a subject heterozygous for the X chromosome-linked alloenzyme system of glucose-6-phosphate dehydrogenase (G6PD). Determination of G6PD mosaicism showed homogeneous expression in granulocytes, erythrocytes and platelets. Cytogenetic studies showed the typical Ph translocation in all metaphases from bone marrow and peripheral blood myeloid cells, bcr rearrangement was detected in bone marrow and in granulocytes. B cells were stimulated with Epstein-Barr virus (EBV) in order to evaluate involvement of lymphocytes, EBV-transformed lymphoblastoid cells expressed a single G6PD phenotype and therefore probably derived from the leukaemic stem cell. However they had a normal karyotype and a constitutional bcr restriction pattern. Molecular analysis in this case of CML clarifies the differentiative potential of cells belonging to the leukaemic clone, by demonstrating that clonal Ph-negative B cells maintain normal differentiative capacity and have a bcr gene sequence which is not rearranged. 相似文献
53.
Graeme Smith Jane Apperley Dragana Milojkovic Nicholas C. P. Cross Letizia Foroni Jenny Byrne Andy Goringe Anupama Rao Jamshid Khorashad Hugues de Lavallade Adam J. Mead Wendy Osborne Chris Plummer Gail Jones Mhairi Copland British Society for Haematology 《British journal of haematology》2020,191(2):171-193
54.
Martina Gaia Cogo Stefania Rota Maria Letizia Fusco Cristina Mapelli Francesca Ferri Ildebrando Marco Appollonio 《Journal of clinical and experimental neuropsychology》2014,36(10):1066-1075
Introduction: Impairment of decision making in relapsing remitting multiple sclerosis is still controversial, and its neuropsychological correlates have never been explored thoroughly, especially in patients with minimal physical and cognitive deficits. In the present study we investigated the cognitive underpinnings of decision making under ambiguous and explicit conditions in patients with very mild relapsing remitting multiple sclerosis, using a dice and a card gambling game. Method: The study sample included 60 patients and 35 healthy subjects. In the Game of Dice Task, winning and losing probabilities are obvious to the subject, while in the Iowa Gambling Task they are initially ambiguous and have to be gradually identified. Performance at the two tasks was correlated with scores obtained at tests investigating cognitive processing speed, memory, language and executive functions. Results: Patients’ performance did not differ from that of controls at either gambling task. There was only a trend for them to be significantly slower than healthy subjects in progressively recognizing advantageous decks in the Iowa Gambling Task. While the Game of Dice was unrelated to neuropsychological tests, predictors of performance at the Iowa task were Letter Fluency and the Symbol Digit Modalities Test for the initial, under-ambiguity, trials and the Wisconsin Card Sorting Test for the last, purely under-risk, trials. Conclusions: Our results suggest that high-functioning patients with relapsing remitting multiple sclerosis are substantially capable of making advantageous decisions, even if they may be slower in processing options and shifting strategy when selection criteria are not explicit. 相似文献
55.
Application of Hydrogen Peroxide to the Control of Eutrophic Lake Systems in Laboratory Assays 总被引:1,自引:0,他引:1
Letizia Bauzá Anabella Aguilera Ricardo Echenique Darío Andrinolo Leda Giannuzzi 《Toxins》2014,6(9):2657-2675
We exposed water samples from a recreational lake dominated by the cyanobacterium Planktothrix agardhii to different concentrations of hydrogen peroxide (H2O2). An addition of 0.33 mg·L−1 of H2O2 was the lowest effective dose for the decay of chlorophyll-a concentration to half of the original in 14 h with light and 17 h in experiments without light. With 3.33 mg·L−1 of H2O2, the values of the chemical oxygen demand (COD) decreased to half at 36 and 126 h in experiments performed with and without light, respectively. With increasing H2O2, there is a decrease in the total and faecal coliform, and this effect was made more pronounced by light. Total and faecal coliform were inhibited completely 48 h after addition of 3.33 mg·L−1 H2O2. Although the densities of cyanobacterial cells exposed to H2O2 did not decrease, transmission electron microscope observation of the trichomes showed several stages of degeneration, and the cells were collapsed after 48 h of 3.33 mg·L−1 of H2O2 addition in the presence of light. Our results demonstrate that H2O2 could be potentially used in hypertrophic systems because it not only collapses cyanobacterial cells and coliform bacteria but may also reduce chlorophyll-a content and chemical oxygen demand. 相似文献
56.
Letizia Perillo Alfredo De Rosa Francesco Iaselli Fabrizia d’Apuzzo Vincenzo Grassia Salvatore Cappabianca 《Progress in orthodontics》2014,15(1)
Background
The aim of this study is to compare the dento-skeletal effects of rapid maxillary expansion (RME) and mixed maxillary expansion (MME), assessed on posteroanterior (PA) cephalograms.Methods
Treatment groups consisted of 42 patients; mean age in RME group (n = 21,13 female and 8 male subjects) was 8.8 years ± 1.37 at T0 and 9.6 years ± 1.45 at T1 and mean age in MME group (n = 21, 12 female and 9 male patients) was 8.9 years ± 2.34 at T0 and 10.5 years ± 2.08 at T1. Seventeen bilateral anatomic landmarks, 16 linear (12 skeletal and 4 dental) and 4 angular measurements were assessed for each patient at T0 and T1. Data from the two groups were compared using independent sample t test (p < 0.05).Results
At T0, the groups were similar for all examined variables (p > 0.05). Significant and equal increase of lateronasal and maxillary and upper and lower molar widths (p < 0. 01) occurred in both groups at T1. Significant but different increases were observed for maxillary incisal, upper left first molar-lateroorbitale, and maxillary first molar angles (p < 0.001 vs. p < 0.05). Significant increases were reported for upper inter-incisal width apex (p < 0.001) and upper right first molar-lateroorbitale angle (p < 0.05) only in the RME group. At T1, differences in maxillary incisal angle (p < 0.05), upper left first molar-lateroorbitale, and maxillary first molar angles (p < 0.001) were noted.Conclusions
RME and MME were both effective to increase skeletal transverse dimensions by opening mid-palatal suture in growing patients, while MME was associated with minor dental side effects than RME. 相似文献57.
Thomas A. Wadden Gary D. Foster A. Letizia Joshua E. Wilk 《The International journal of eating disorders》1993,14(1):17-25
This study examined the relationship of binge eating to a variety of metabolic, anthropometric, and psychological characteristics in 132 obese women seeking weight reduction. Contrary to findings of a reduced resting metabolic rate (RMR) in persons with bulimia nervosa, no significant differences were observed between obese bingers and nonbingers in RMR or thyroid hormones. Nor did the two groups differ significantly in weight, percentage body fat, body fat distribution, or serum lipid levels. Consistent with previous findings, however, binge eaters did score significantly higher in depression and other measures of psychopathology, as assessed by the Minnesota Multiphasic Personality Inventory. They also scored significantly higher in disinhibition and hunger but significantly lower in cognitive restraint. All of these findings await confirmation in subjects diagnosed according to criteria proposed for a new binge eating disorder. The present results, however, provide little support for the hypothesis that binge eating in obese individuals is related to reduced resting energy requirements. © 1993 by John Wiley & Sons, Inc. 相似文献
58.
Margherita Prosperi Elisa Santocchi Letizia Guiducci Jacopo Frinzi Maria Aurora Morales Raffaella Tancredi Filippo Muratori Sara Calderoni 《Nutrients》2022,14(3)
The alteration of the microbiota–gut–brain axis has been recently recognized as a critical modulator of neuropsychiatric health and a possible factor in the etiopathogenesis of autism spectrum disorders (ASD). This systematic review offers practitioners an overview of the potential therapeutic options to modify dysbiosis, GI symptoms, and ASD severity by modulating the microbiota–gut–brain axis in ASD, taking into consideration limits and benefits from current findings. Comprehensive searches of PubMed, Scopus, the Web of Science Core Collection, and EMBASE were performed from 2000 to 2021, crossing terms referred to ASD and treatments acting on the microbiota–gut–brain axis. A total of 1769 publications were identified, of which 19 articles met the inclusion criteria. Data were extracted independently by two reviewers using a preconstructed form. Despite the encouraging findings, considering the variability of the treatments, the samples size, the duration of treatment, and the tools used to evaluate the outcome of the examined trials, these results are still partial. They do not allow to establish a conclusive beneficial effect of probiotics and other interventions on the symptoms of ASD. In particular, the optimal species, subspecies, and dosages have yet to be identified. Considering the heterogeneity of ASD, double-blind, randomized, controlled trials and treatment tailored to ASD characteristics and host-microbiota are recommended. 相似文献
59.
Lunetta Christian Moglia Cristina Lizio Andrea Caponnetto Claudia Dubbioso Raffaele Giannini Fabio Matà Sabrina Mazzini Letizia Sabatelli Mario Siciliano Gabriele Simone Isabella Laura Sorarù Gianni Toriello Antonella Trojsi Francesca Vedovello Marcella D’Ovidio Fabrizio Filippi Massimo Calvo Andrea 《Journal of neurology》2020,267(11):3258-3267
Journal of Neurology - The aim of the study is to analyze the ALS disease progression and respiratory function of Italian patients treated with edaravone (EVN), as well as the adherence to, and the... 相似文献
60.
Falzone Yuri Matteo Domi Teuta Agosta Federica Pozzi Laura Schito Paride Fazio Raffaella Del Carro Ubaldo Barbieri Alessandra Comola Mauro Leocani Letizia Comi Giancarlo Carrera Paola Filippi Massimo Quattrini Angelo Riva Nilo 《Journal of neurology》2020,267(8):2272-2280
Journal of Neurology - To investigate the prognostic role and the major determinants of serum phosphorylated neurofilament heavy -chain (pNfH) concentration across a large cohort of motor neuron... 相似文献