全文获取类型
收费全文 | 1203篇 |
免费 | 53篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 3篇 |
儿科学 | 30篇 |
妇产科学 | 19篇 |
基础医学 | 187篇 |
口腔科学 | 97篇 |
临床医学 | 61篇 |
内科学 | 268篇 |
皮肤病学 | 30篇 |
神经病学 | 197篇 |
特种医学 | 30篇 |
外科学 | 141篇 |
综合类 | 3篇 |
一般理论 | 1篇 |
预防医学 | 62篇 |
眼科学 | 10篇 |
药学 | 65篇 |
中国医学 | 1篇 |
肿瘤学 | 58篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 45篇 |
2020年 | 27篇 |
2019年 | 34篇 |
2018年 | 31篇 |
2017年 | 13篇 |
2016年 | 17篇 |
2015年 | 28篇 |
2014年 | 39篇 |
2013年 | 51篇 |
2012年 | 78篇 |
2011年 | 102篇 |
2010年 | 44篇 |
2009年 | 45篇 |
2008年 | 87篇 |
2007年 | 62篇 |
2006年 | 92篇 |
2005年 | 77篇 |
2004年 | 85篇 |
2003年 | 67篇 |
2002年 | 57篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 16篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1971年 | 2篇 |
1898年 | 2篇 |
排序方式: 共有1263条查询结果,搜索用时 31 毫秒
1.
Osvaldo Chiara Stefania Cimbanassi Alessio Pitidis Sergio Vesconi 《World journal of emergency surgery : WJES》2006,1(1):12-7
Preventable trauma deaths are defined as deaths which could be avoided if optimal care has been delivered. Studies on preventable
trauma deaths have been accomplished initially with panel reviews of pre-hospital and hospital charts. However, several investigators
questioned the reliability and validity of this method because of low reproducibility of implicit judgments when they are
made by different experts. Nevertheless, number of studies were published all around the world and ultimately gained some
credibility, particularly in regions where comparisons were made before and after trauma system implementation with a resultant
fall in mortality. During the last decade of century the method of comparing observed survival with probability of survival
calculated from large trauma registries has obtained popularity. Preventable trauma deaths were identified as deaths occurred
notwithstanding a high calculated probability of survival. In recent years, preventable trauma deaths studies have been replaced
by population-based studies, which use databases representative of overall population, therefore with high epidemiologic value.
These databases contain readily available information which carry out the advantage of objectivity and large numbers. Nowadays,
population-based researches provide the strongest evidence regarding the effectiveness of trauma systems and trauma centers
on patient outcomes. 相似文献
2.
The steady-state density and the turnover rates of D1-dopamine receptors were investigated in the striatum, nucleus accumbens, substantia nigra, and retina of adult (3-month-old) and aged (23-month-old) rats. The turnover rates were measured by monitoring the repopulation kinetics of D1-dopamine receptors labeled with [3H]-SCH 23390 after the irreversible inactivation induced by a single dose of N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ, 10 mg/kg, s.c.). In all the neural tissues examined, the repopulation of D1 dopamine receptors could be adequately described by a theoretical model that assumes a constant rate of receptor production (i.e. zero order) and a rate of degradation that is dependent on the receptor density at any time (i.e. first order). The results obtained indicate that the reduction in the density of D1-dopamine receptors in the striatum, nucleus accumbens and substantia nigra of aged rats is the result of a larger decrease in the receptor production rate (−44 to −60%) than in the receptor degradation rate (−21 to −46%). By contrast, the production rate of D1-dopamine receptors in the retina of aged rats remains unchanged, whilst the degradation rate is reduced by 25%. This results in an age-related increase in the density of D1-dopamine receptors in the rat retina. 相似文献
3.
Fumiharu Kimura R. Glenn Smith Osvaldo Delbono Okot Nyormoi Toni Schneider Wolfgang Nastainczyk Franz Hofmann Enrico Stefani Stanley H. Appel 《Annals of neurology》1994,35(2):164-171
Sporadic amyotrophic lateral sclerosis is an idiopathic human degenerative disease of spinal cord and brain motor neurons. Prior studies demonstrated that most patients with amyotrophic lateral sclerosis posses immunoglobulins that bind to purified L-type voltage-gated calcium channels, that titers of anti–voltage-gated calcium channel antibodies correlate with disease progression rates, and that amyotrophic lateral sclerosis patient-derived antibodies (ALS IgG) produce electrophysiological changes in the function of voltage-gated calcium channels. Using Western transfer immunoblots and enzyme-linked immunosorbent assays, the calcium ionophore–forming α1 subunig of the voltage-gated calcium channel is now identified as the major voltage-gated calcium channel antigen to which ALS IgG binds. Additionally, the binding of an L-type voltage-gated calcium channel α1 subunit–directed monoclonal antibody, which itself mimics the effects of ALS IgG on skeletal muscle voltage-gated calcium channel currents, is selectively prevented by preaddition of ALS IgG. Voltage-gated calcium channel–binding IgG from patients with Lambert-Eaton myasthenic syndrome appears to be differentiated from ALS IgG by the reactivity of the former to both α1 and β subunits of the calcium channel. These assays provide further evidence linking amyotrophic lateral sclerosis to an autoimmune process, and suggest one means to differentiate immunoglobulins from patients with amyotrophic lateral sclerosis from those of patients with another autoimmune disease expressing calcium channel antibodies. 相似文献
4.
Michelle K Williamson Jane Pirkis Jon J Pfaff Orla Tyson Moira Sim Ngaire Kerse Nicola T Lautenschlager Nigel P Stocks Osvaldo P Almeida 《BMC medical research methodology》2007,7(1):42
Background
Recruiting and retaining GPs for research can prove difficult, and may result in sub-optimal patient participation where GPs are required to recruit patients. Low participation rates may affect the validity of research. 相似文献5.
Filho OG Gordan AN Mello Rde A Neto CS Heinke T 《International journal of surgical pathology》2004,12(2):151-153
Hamartomas were first described by Albrecht in 1904, who defined them as tumor-like malformations in which there was abnormal blending of the normal components of an organ. The myoid hamartoma is a rare benign lesion of the breast and has an uncertain origin, possibly in the walls of the blood vessels, muscularis mammillae of the areolae, and mainly in myoepithelium. We report 3 cases of myoid hamartomas of the breast, with the clinical, radiologic, and histopathological findings, and review the literature. The 3 lesions showed normal breast ducts and lobules, entrapped by a muscular stroma and some foci of mature adipose tissue. The muscular origin of part of the stroma was confirmed by strong reactiveness with smooth-muscle actin. 相似文献
6.
Fbio A. Kunrath Fbio F. Mota Osvaldo L. Casagrande Raquel S. Mauler Roberto F. de Souza 《Macromolecular chemistry and physics.》2002,203(17):2407-2411
The polymerization of ethylene in the presence of 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediiminenickel(II) dichloride ( 1 ) and methylaluminoxane (MAO) gives hyperbranched polyethylene (HBPE) in appropriate reaction conditions. The system 1 /MAO is active in solvents like toluene or hexane at temperatures as high as 80 °C and ethylene pressures ranging from 1 to 15 atm. The polyethylenes obtained show high molecular weights (up to 467 kg · mol?1) and more than 218 branches per 1 000 backbone carbon atoms, qualifying these materials as hyperbranched. Dynamic‐mechanical thermal analysis (DMTA) of these materials shows high β‐transitions, directly related to the branch content of these polyethylenes.
7.
Osvaldo Santos Miodraga Stefanovska-Petkovska Ana Virgolino Ana Cristina Miranda Joana Costa Elisabete Fernandes Susana Cardoso Antnio Vaz Carneiro 《Nutrients》2021,13(3)
Self-management of health requires skills to obtain, process, understand, and use health-related information. Assessment of adolescents’ functional health literacy requires valid, reliable, and low-burden tools. The main objective of this study was to adapt and study the psychometric properties of the Newest Vital Sign for the Portuguese adolescents’ population (NVS-PTeen). Classic psychometric indicators of reliability and validity were combined with item response theory (IRT) analyses in a cross-sectional survey, complemented with a 3-month test-retest assessment. The NVS-PTeen was self-administered to students enrolled in grades 8 to 12 (12 to 17 years old) in a school setting. Overall, 386 students (191 girls) from 16 classes of the same school participated in the study (mean age = 14.5; SD = 1.5). Internal reliability of the NVS-PTeen was α = 0.60. The NVS-PTeen total score was positively and significantly correlated with Portuguese (r = 0.28) and mathematics scores (r = 0.31), school years (r = 0.31), and age (r = 0.19). Similar to the original scale (for the U.S.), the NVS-PTeen is composed of two dimensions, reading-related literacy and numeracy. Temporal reliability is adequate, though with a learning effect. IRT analyses revealed differences in difficulty and discriminative capacity among items, all with adequate outfit and infit values. Results showed that the NVS-PTeen is valid and reliable, sensible to inter-individual educational differences, and adequate for regular screening of functional health literacy in adolescents. 相似文献
8.
Ralf Berger Jurandir Marcondes Ribas Filho Osvaldo Malafaia Paulo Afonso Nunes Nassif Eduardo Nascimento Silva Alfredo Benjamin Duarte da Silva Milka Takejima Marcelo Augusto de Souza Pedro Henrique de Paula Mrio Rodrigues Montemor Netto Lucia de Noronha 《Acta cirúrgica brasileira / Sociedade Brasileira para Desenvolvimento Pesquisa em Cirurgia》2021,36(5)
9.
Liseana O. Barbosa Jos Osvaldo B. Neto Antnio Augusto L. Teixeira-Júnior Leudivan R. Nogueira Jos de Ribamar R. Calixto Isabela W. Cunha Jaqueline D. Pinho Francisco Srgio M. S. do Nascimento Syomara Pereira da C. Melo Fernando A. Soares Gyl Eanes B. Silva 《Translational andrology and urology》2021,10(4):1803
Pseudoangiosarcomatous squamous cell carcinoma, also called pseudovascular, pseudoangiomatoid or adenoid pseudovascular carcinoma, is an uncommon and highly aggressive variant of squamous cell carcinoma. Histologically, it is characterized by proliferation of atypical keratinocytes with acantholysis and formation of pseudovascular spaces, forming anastomosed channels lined with neoplastic cells that invade the dermis. These cells are positive for cytokeratin and negative for vascular markers such as CD31 and CD34. There are few reports of this variant in the literature. Skin, breast, lung and vulva involvement have been described, but to the best of our knowledge, no cases involving the penis has been described. This study aims to describe the first case of angiosarcomatous squamous cell carcinoma of the penis. The patient presented with a painful lesion in the penis associated with urinary retention. Macroscopic findings exhibited an ulcerative vegetating lesion that involving the entire glans and part of the penile body, as well as infiltration of penile structures and scrotal skin. Microscopy shows atypical proliferation of sarcomatous keratinocyte pattern mimicking vascular spaces. Human papilloma virus (HPV) biomarkers and polymerase chain reaction (PCR) were all negative. Advanced penile squamous cell carcinoma with aggressive lymph node metastasis. This report presents the first case of penile pseudoangiosarcomatous squamous cell carcinoma, as an important differential diagnosis. 相似文献
10.
Miranda Michele Zarivi Osvaldo Amicarelli Fernanda Ragnelli Anna Maria Aimola Pierpaolo Porretta Rocchina Natali Pier Giorgio Arcadi Antonio Savino Maria Poma Anna Bonfigli Antonella 《Journal of neuro-oncology》1997,31(1-2):185-193
This paper presents evidence that L-tyrosine oxidation products and 5,6-dihydroxyindole, an intermediate of melanin synthesis bind to and modify DNA structure, as tested by extracting cell DNA, using topoisomerase I and denaturation assays. When supercoiled plasmid pCU18 or pBR322 DNAs are treated with 5,6-dihydroxyindole the supercoiled species disappear and are converted to species less mobile in a gel retardation test with respect to relaxed DNA. 5,6-Dihydroxyindole causes an easier acid denaturation of the double helix. The results, that are dose dependent,would point to both intercalation and cross-linking of DNA by 5,6-dihydroxyindole and its oxidation product(s). 3H-L-tyrosine deriving radioactivity, bound to nuclear DNA, is higher at low pH, (5.6) if compared to pH 6.8. The highest radioactivity bound to cell DNA is found during the transition from the amelanotic to the melanotic phenotype in human melanoma cell lines. As a control, the binding of 3H-L-tyrosine radioactivity to human prostate fibroblast DNA was investigated. 相似文献