全文获取类型
收费全文 | 2831篇 |
免费 | 180篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 41篇 |
儿科学 | 89篇 |
妇产科学 | 46篇 |
基础医学 | 413篇 |
口腔科学 | 173篇 |
临床医学 | 196篇 |
内科学 | 694篇 |
皮肤病学 | 68篇 |
神经病学 | 145篇 |
特种医学 | 194篇 |
外国民族医学 | 1篇 |
外科学 | 259篇 |
综合类 | 62篇 |
一般理论 | 1篇 |
预防医学 | 285篇 |
眼科学 | 29篇 |
药学 | 164篇 |
中国医学 | 47篇 |
肿瘤学 | 116篇 |
出版年
2023年 | 16篇 |
2022年 | 73篇 |
2021年 | 96篇 |
2020年 | 65篇 |
2019年 | 92篇 |
2018年 | 115篇 |
2017年 | 67篇 |
2016年 | 72篇 |
2015年 | 86篇 |
2014年 | 113篇 |
2013年 | 138篇 |
2012年 | 195篇 |
2011年 | 201篇 |
2010年 | 127篇 |
2009年 | 111篇 |
2008年 | 138篇 |
2007年 | 135篇 |
2006年 | 102篇 |
2005年 | 111篇 |
2004年 | 71篇 |
2003年 | 57篇 |
2002年 | 78篇 |
2001年 | 41篇 |
2000年 | 49篇 |
1999年 | 34篇 |
1998年 | 44篇 |
1997年 | 41篇 |
1996年 | 40篇 |
1995年 | 41篇 |
1994年 | 30篇 |
1993年 | 22篇 |
1992年 | 24篇 |
1991年 | 12篇 |
1990年 | 22篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 28篇 |
1986年 | 23篇 |
1985年 | 26篇 |
1984年 | 25篇 |
1983年 | 25篇 |
1982年 | 18篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1976年 | 12篇 |
1973年 | 11篇 |
1969年 | 11篇 |
1968年 | 12篇 |
排序方式: 共有3023条查询结果,搜索用时 31 毫秒
81.
AJ Geall A Verma GR Otten CA Shaw A Hekele K Banerjee Y Cu CW Beard LA Brito T Krucker DT O'Hagan M Singh PW Mason NM Valiante PR Dormitzer SW Barnett R Rappuoli JB Ulmer CW Mandl 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(36):14604-14609
Despite more than two decades of research and development on nucleic acid vaccines, there is still no commercial product for human use. Taking advantage of the recent innovations in systemic delivery of short interfering RNA (siRNA) using lipid nanoparticles (LNPs), we developed a self-amplifying RNA vaccine. Here we show that nonviral delivery of a 9-kb self-amplifying RNA encapsulated within an LNP substantially increased immunogenicity compared with delivery of unformulated RNA. This unique vaccine technology was found to elicit broad, potent, and protective immune responses, that were comparable to a viral delivery technology, but without the inherent limitations of viral vectors. Given the many positive attributes of nucleic acid vaccines, our results suggest that a comprehensive evaluation of nonviral technologies to deliver self-amplifying RNA vaccines is warranted. 相似文献
82.
Neide Pena Coto Josete Barbosa Cruz Meira Reinaldo Brito e Dias Larissa Driemeier Guilherme de Oliveira Roveri Pedro Yoshito Noritomi 《Dental traumatology》2012,28(2):108-113
Abstract – There has been a significant increase in the number of facial fractures stemming from sport activities in recent years, with the nasal bone one of the most affected structures. Researchers recommend the use of a nose protector, but there is no standardization regarding the material employed. Clinical experience has demonstrated that a combination of a flexible and rigid layer of ethylene vinyl acetate (EVA) offers both comfort and safety to practitioners of sports. The aim of the present study was the investigation into the stresses generated by the impact of a rigid body on the nasal bone on models with and without an EVA protector. For such, finite element analysis was employed. A craniofacial model was constructed from images obtained through computed tomography. The nose protector was modeled with two layers of EVA (1 mm of rigid EVA over 2 mm of flexible EVA), following the geometry of the soft tissue. Finite element analysis was performed using the LS Dyna program. The bone and rigid EVA were represented as elastic linear material, whereas the soft tissues and flexible EVA were represented as hyperelastic material. The impact from a rigid sphere on the frontal region of the face was simulated with a constant velocity of 20 m s?1 for 9.1 μs. The model without the protector served as the control. The distribution of maximal stress of the facial bones was recorded. The maximal stress on the nasal bone surpassed the breaking limit of 0.13–0.34 MPa on the model without a protector, while remaining below this limit on the model with the protector. Thus, the nose protector made from both flexible and rigid EVA proved effective at protecting the nasal bones under high‐impact conditions. 相似文献
83.
Tostões RM Leite SB Serra M Jensen J Björquist P Carrondo MJ Brito C Alves PM 《Hepatology (Baltimore, Md.)》2012,55(4):1227-1236
Primary cultures of human hepatocyte spheroids are a promising in vitro model for long-term studies of hepatic metabolism and cytotoxicity. The lack of robust methodologies to culture cell spheroids, as well as a poor characterization of human hepatocyte spheroid architecture and liver-specific functionality, have hampered a widespread adoption of this three-dimensional culture format. In this work, an automated perfusion bioreactor was used to obtain and maintain human hepatocyte spheroids. These spheroids were cultured for 3-4 weeks in serum-free conditions, sustaining their phase I enzyme expression and permitting repeated induction during long culture times; rate of albumin and urea synthesis, as well as phase I and II drug-metabolizing enzyme gene expression and activity of spheroid hepatocyte cultures, presented reproducible profiles, despite basal interdonor variability (n = 3 donors). Immunofluorescence microscopy of human hepatocyte spheroids after 3-4 weeks of long-term culture confirmed the presence of the liver-specific markers, hepatocyte nuclear factor 4α, albumin, cytokeratin 18, and cytochrome P450 3A. Moreover, immunostaining of the atypical protein kinase C apical marker, as well as the excretion of a fluorescent dye, evidenced that these spheroids spontaneously assemble a functional bile canaliculi network, extending from the surface to the interior of the spheroids, after 3-4 weeks of culture. Conclusion: Perfusion bioreactor cultures of primary human hepatocyte spheroids maintain a liver-specific activity and architecture and are thus suitable for drug testing in a long-term, repeated-dose format. 相似文献
84.
Elizabete Bagordakis Lívia Máris Ribeiro Paranaiba Luciano Abreu Brito Sibele Nascimento de Aquino Ana Camila Messetti Hercílio Martelli‐Junior Mario Sergio Oliveira Swerts Edgard Graner Maria Rita Passos‐Bueno Ricardo D. Coletta DDS MS PhD 《American journal of medical genetics. Part A》2013,161(5):1177-1180
85.
Lorena C.W. Brito Silvia DalBó Tatiane M. Striechen Jéssica M. Farias Luiz R. Olchanheski Jr. Reila T. Mendes José C.R. Vellosa Giovani M. Fávero Regina Sordi Jamil Assreuy Fábio A. Santos Daniel Fernandes 《Archives of oral biology》2013
Objectives
This study aimed to evaluate the systemic inflammatory response and cardiovascular changes induced by experimental periodontitis in rats.Design
Experimental periodontitis was induced by placing a cotton ligature around the cervix of both sides of mandibular first molars and maxillary second molars in each male rat. Sham-operated rats had the ligature removed immediately after the procedure. Seven, 14 or 28 days after procedure, the effects of acetylcholine, sodium nitroprusside and phenylephrine were evaluated on blood pressure, aortic rings and isolated and perfused mesenteric bed. The blood was obtained for plasma Interleukin-6 (IL-6), C-reactive protein (CRP) and lipid evaluation. The mesenteric vessels were obtained to evaluate superoxide production and nitric oxide synthase 3 (NOS-3) expression.Results
Ligature induced periodontitis reduced endothelium-dependent vasodilatation, a hallmark of endothelial dysfunction. This effect was associated with an increase in systemic inflammatory markers (IL-6 and CRP), worsens on lipid profile, increased vascular superoxide production and reduced NOS-3 expression. It is interesting to note that many of these effects were transitory.Conclusion
Periodontitis induced a transient systemic and vascular inflammation which leads to endothelial dysfunction, an initial step for cardiovascular diseases. Moreover, the animal model of periodontitis used here may represent a valuable tool for studying the relationship between periodontitis and endothelial dysfunction. 相似文献86.
Vicente Castelo Branco Leitune Fabrício Mezzomo Collares Antonio Takimi Ginia Brito de Lima César Liberato Petzhold Carlos Pérez Bergmann Susana Maria Werner Samuel 《Journal of dentistry》2013
Objectives
The purpose of this study was to develop an adhesive resin with incorporation of niobium pentoxide and evaluate its properties.Methods
Niobium pentoxide was characterised by X-ray diffraction, surface area, particle size, micro-Raman, scanning electron microscopy and the effectiveness of silanisation process by Fourier Transform Infrared (FTIR). An experimental adhesive resin was formulated with 0, 5, 10 and 20 wt% Nb2O5. The formulated adhesive resins were evaluated based on microhardness, degree of conversion, radiopacity and interface (resin/dentine) characterisation by micro-Raman.Results
The particles used in this study presented a monoclinic crystalline phase with typical chemical groups and micrometre mean size. Microhardness and radiopacity increased with higher amounts of Nb2O5, and the particles were able to penetrate into the hybrid layers.Conclusions
Therefore, Nb2O5 may be an alternative for polymer-based biomaterials.Clinical significance: Niobium pentoxide could be used to produce adhesive resins with enhanced properties. 相似文献87.
88.
89.
90.