全文获取类型
收费全文 | 655807篇 |
免费 | 34210篇 |
国内免费 | 794篇 |
专业分类
耳鼻咽喉 | 8631篇 |
儿科学 | 20713篇 |
妇产科学 | 15190篇 |
基础医学 | 109515篇 |
口腔科学 | 17237篇 |
临床医学 | 56584篇 |
内科学 | 126215篇 |
皮肤病学 | 15757篇 |
神经病学 | 44089篇 |
特种医学 | 22530篇 |
外国民族医学 | 55篇 |
外科学 | 93598篇 |
综合类 | 8292篇 |
现状与发展 | 2篇 |
一般理论 | 148篇 |
预防医学 | 51119篇 |
眼科学 | 14773篇 |
药学 | 50352篇 |
1篇 | |
中国医学 | 1746篇 |
肿瘤学 | 34264篇 |
出版年
2021年 | 6680篇 |
2019年 | 6879篇 |
2018年 | 10651篇 |
2017年 | 7031篇 |
2016年 | 7627篇 |
2015年 | 8451篇 |
2014年 | 10704篇 |
2013年 | 15861篇 |
2012年 | 24749篇 |
2011年 | 27222篇 |
2010年 | 14915篇 |
2009年 | 12351篇 |
2008年 | 23489篇 |
2007年 | 25665篇 |
2006年 | 24503篇 |
2005年 | 23770篇 |
2004年 | 22452篇 |
2003年 | 21470篇 |
2002年 | 20593篇 |
2001年 | 26022篇 |
2000年 | 27035篇 |
1999年 | 21947篇 |
1998年 | 5782篇 |
1997年 | 4721篇 |
1996年 | 4751篇 |
1995年 | 4402篇 |
1992年 | 15670篇 |
1991年 | 16893篇 |
1990年 | 16886篇 |
1989年 | 16401篇 |
1988年 | 14965篇 |
1987年 | 14787篇 |
1986年 | 13797篇 |
1985年 | 13192篇 |
1984年 | 9808篇 |
1983年 | 8308篇 |
1982年 | 4344篇 |
1979年 | 9288篇 |
1978年 | 6587篇 |
1977年 | 5357篇 |
1976年 | 5710篇 |
1975年 | 6869篇 |
1974年 | 7713篇 |
1973年 | 7474篇 |
1972年 | 6849篇 |
1971年 | 6586篇 |
1970年 | 6126篇 |
1969年 | 5740篇 |
1968年 | 5405篇 |
1967年 | 4841篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
Immunohistochemical and molecular analysis of PI3K/AKT/mTOR pathway in esophageal carcinoma
下载免费PDF全文
![点击此处可从《APMIS : acta pathologica, microbiologica, et immunologica Scandinavica》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Georgia Levidou Dimitrios Theodorou Nikolaos V. Michalopoulos Efstratios Patsouris Angelica A. Saetta 《APMIS : acta pathologica, microbiologica, et immunologica Scandinavica》2015,123(8):639-647
Among the numerous signaling pathways involved in tumorigenesis, PI3K‐AKT‐mTOR is a key one that regulates diverse cellular functions. However, its prognostic value in esophageal carcinoma remains unclear. In our study, we examined the immunohistochemical expression of phosphorylated (p‐) AKT, mTOR, p70S6K and 4E‐BP1 along with the mutational status of PIK3CA and AKT1 genes by High Resolution Melting Analysis and Pyrosequencing in 44 esophageal carcinomas. The results were correlated with the clinicopathological characteristics of the patients in an effort to define their possible prognostic significance. Total p‐mTOR cytoplasmic expression, assessed in 10 random areas, was positively correlated with tumor stage (Kruskal–Wallis ANOVA, I/II vs III/IV, p = 0.0500). Μoreover, maximum p‐mTOR cytoplasmic immunoexpression, estimated in hot spot areas, was positively associated with tumor grade (Mann–Whitney U test, I/II vs III, p = 0.0565). Interestingly, p‐4E‐BP1 immunoreactivity was negatively correlated with tumor histological grade (Mann–Whitney U test, I/II vs III, p = 0.0427). No mutation was observed in exons 9 and 20 of PIK3CA gene and in exon 4 of AKT1 gene. In conclusion, our findings depict the presence of activated PI3K/AKT/mTOR pathway in esophageal cancer bringing forward p‐mTOR and p‐4E‐BP1 for their potential role in esophageal carcinogenesis. Additional studies are warranted to validate our findings. 相似文献
152.
153.
154.
155.
156.
157.
An important part of fundamental research in catalysis is based on theoretical and modeling foundations which are closely connected with studies of single-crystalline catalyst surfaces. These so-called model catalysts are often prepared in the form of epitaxial thin films, and characterized using advanced material characterization techniques. This concept provides the fundamental understanding and the knowledge base needed to tailor the design of new heterogeneous catalysts with improved catalytic properties. The present contribution is devoted to development of a model catalyst system of CeO2 (ceria) on the Cu(111) substrate. We propose ways to experimentally characterize and control important parameters of the model catalyst—the coverage of the ceria layer, the influence of the Cu substrate, and the density of surface defects on ceria, particularly the density of step edges and the density and the ordering of the oxygen vacancies. The large spectrum of controlled parameters makes ceria on Cu(111) an interesting alternative to a more common model system ceria on Ru(0001) that has served numerous catalysis studies, mainly as a support for metal clusters. 相似文献
158.
159.
Rubens Souza de OLIVEIRA Lanna Jamile Corrêa da COSTA Fernanda Atanaena Gon?alves de ANDRADE Wilson UIEDA Luzia Fátima Alves MARTORELLI Ana Paula de Arruda Geraldes KATAOKA Elizabeth Salbé Travassos da ROSA Pedro Fernando da Costa VASCONCELOS Armando de Souza PEREIRA Ant?nio Ismael Barros do CARMO Marcus Emanuel Barroncas FERNANDES 《Revista do Instituto de Medicina Tropical de S?o Paulo》2015,57(6):497-503
The outbreaks of rabies in humans transmitted by Desmodus rotundus in 2004 and 2005,
in the northeast of the Brazilian State of Para, eastern Amazon basin, made this a
priority area for studies on this zoonosis. Given this, the present study provides
data on this phenomenon in an urban context, in order to assess the possible
circulation of the classic rabies virus (RABV) among bat species in Capanema, a town
in the Amazon basin. Bats were collected, in 2011, with mist nets during the wet and
dry seasons. Samples of brain tissue and blood were collected for virological and
serological survey, respectively. None of the 153 brain tissue samples analyzed
tested positive for RABV infection, but 50.34% (95% CI: 45.67-55.01%) of the serum
samples analyzed were seropositive. Artibeus planirostris was the most common
species, with a high percentage of seropositive individuals (52.46%, 95% CI: 52.31
52.60%). Statistically, equal proportions of seropositive results were obtained in
the rainy and dry seasons (c2 = 0.057, d.f. = 1, p = 0.88). Significantly
higher proportions of males (55.96%, 95% CI: 48.96-62.96%) and adults (52.37%, 95%
CI: 47.35-57.39%) were seropositive. While none of the brain tissue samples tested
positive for infection, the high proportion of seropositive specimens indicates that
RABV may be widespread in this urban area. 相似文献
160.
S. Natoli V. Oliveira P. Calabresi L. F. Maia A. Pisani 《European journal of neurology》2020,27(9):1764-1773
The current coronavirus disease (COVID‐19) outbreak, caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), has raised the possibility of potential neurotropic properties of this virus. Indeed, neurological sequelae of SARS‐CoV‐2 infection have already been reported and highlight the relevance of considering the neurological impact of coronavirus (CoV) from a translational perspective. Animal models of SARS and Middle East respiratory syndrome, caused by structurally similar CoVs during the 2002 and 2012 epidemics, have provided valuable data on nervous system involvement by CoVs and the potential for central nervous system spread of SARS‐CoV‐2. One key finding that may unify these pathogens is that all require angiotensin‐converting enzyme 2 as a cell entry receptor. The CoV spike glycoprotein, by which SARS‐CoV‐2 binds to cell membranes, binds angiotensin‐converting enzyme 2 with a higher affinity compared with SARS‐CoV. The expression of this receptor in neurons and endothelial cells hints that SARS‐CoV‐2 may have higher neuroinvasive potential compared with previous CoVs. However, it remains to be determined how such invasiveness might contribute to respiratory failure or cause direct neurological damage. Both direct and indirect mechanisms may be of relevance. Clinical heterogeneity potentially driven by differential host immune‐mediated responses will require extensive investigation. Development of disease models to anticipate emerging neurological complications and to explore mechanisms of direct or immune‐mediated pathogenicity in the short and medium term is therefore of great importance. In this brief review, we describe the current knowledge from models of previous CoV infections and discuss their potential relevance to COVID‐19. 相似文献