全文获取类型
收费全文 | 2419篇 |
免费 | 119篇 |
出版年
2023年 | 25篇 |
2022年 | 35篇 |
2021年 | 61篇 |
2020年 | 53篇 |
2019年 | 55篇 |
2018年 | 71篇 |
2017年 | 66篇 |
2016年 | 92篇 |
2015年 | 129篇 |
2014年 | 164篇 |
2013年 | 189篇 |
2012年 | 199篇 |
2011年 | 212篇 |
2010年 | 124篇 |
2009年 | 97篇 |
2008年 | 140篇 |
2007年 | 142篇 |
2006年 | 131篇 |
2005年 | 107篇 |
2004年 | 105篇 |
2003年 | 83篇 |
2002年 | 80篇 |
2001年 | 15篇 |
2000年 | 9篇 |
1999年 | 11篇 |
1998年 | 18篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1966年 | 2篇 |
排序方式: 共有2538条查询结果,搜索用时 15 毫秒
141.
Aírton J. Rombaldi Lúcia C. Pellanda Renata M. Bielemann Denise P. Gigante Pedro C. Hallal Bernardo L. Horta 《PloS one》2015,10(5)
BackgroundThere is conflicting evidence about the association between physical activity and inflammatory markers. Few prospective studies are available, particularly from low and middle-income countries. This study was aimed at assessing the cross-sectional and prospective associations between physical activity and C-reactive protein (CRP) levels in males belonging to the 1982 Pelotas (Brazil) Birth Cohort Study.MethodsThe sample comprised 2,213 males followed up at the ages of 18 and 23 years. We performed high sensitivity CRP assays; we used a cut-off of 3 mg/L in categorical analyses. We measured physical activity by self-report at ages 18 and 23 years. Body mass index and waist circumference were studies as possible mediators.ResultsCRP levels above the 3mg/L cut-off were found in 13.3% (95%CI: 11.7; 14.8) of the individuals. We found no evidence for an association between physical activity (leisure-time or all-domains) and either continuous (geometrical mean) or categorical CRP. We confirmed these null findings in (a) prospective and cross-sectional analyses; (b) trajectories analyses.ConclusionsThere was no association between CRP levels and physical activity levels in early adulthood in a large birth cohort. Little variability in CRP at this early age is the likely explanation for these null findings. 相似文献
142.
Daniella Braz Parente Fernando Fernandes Paiva Jaime Araújo Oliveira Neto Lilian Machado-Silva Fatima Aparecida Ferreira Figueiredo Valeria Lanzoni Carlos Frederico Ferreira Campos Pedro Emmanuel Alvarenga Americano do Brasil Marilia de Brito Gomes Renata de Mello Perez Rosana Souza Rodrigues 《PloS one》2015,10(5)
ObjectiveTo evaluate the capability of intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) to assess steatohepatitis and fibrosis determined by histopathology in type 2 diabetic patients.MethodsFifty-nine type 2 diabetic patients (49 women, 10 men; mean age, 54 ± 9 years) were submitted to liver biopsy for the evaluation of non-alcoholic fatty liver disease (NAFLD) and underwent DWI on a 3.0T MR system using 10 b values. Institutional approval and patient consent were obtained. Pure molecular-based (D), perfusion-related (D*), and vascular fraction (f) were calculated using a double exponential model and least squares curve fitting. D, D*, and f were compared between patients with and without steatohepatitis and between patients with and without fibrosis. The variables were compared by using the Ranksum test and Student t-test.ResultsSteatohepatitis was observed in 22 patients and fibrosis in 16 patients. A lower D median (0.70 s/mm2 vs. 0.83 s/mm2, p<0.05) and a lower D* median (34.39 s/mm2 vs. 45.23 s/mm2, p<0.05) were observed among those with steatohepatitis. A lower D median (0.70 s/mm2 vs. 0.82 s/mm2, p<0.05) and a lower D* median (35.01 s/mm2 vs. 44.76 s/mm2, p=0.05) were also observed among those with fibrosis.ConclusionIVIM-DWI has the potential to aid in the characterization of steatohepatitis and fibrosis. 相似文献
143.
The influence of alkaline and the neutral grade of magnesium aluminometasilicate as a porous solid carrier for the liquid self-emulsifying formulation with ibuprofen is investigated. Ibuprofen is dissolved in Labrasol, then this solution is adsorbed on the silicates. The drug to the silicate ratio is 1:2, 1:4, and 1:6, respectively. The properties of formulations obtained are analyzed, using morphological, porosity, crystallinity, and dissolution studies. Three solid self-emulsifying (S-SE) formulations containing Neusilin SG2 and six consisting of Neusilin US2 are in the form of powder without agglomerates. The nitrogen adsorption method shows that the solid carriers are mesoporous but they differ in a specific surface area, pore area, and the volume of pores. The adsorption of liquid SE formulation on solid silicate particles results in a decrease in their porosity. If the neutral grade of magnesium aluminometasilicate is used, the smallest pores, below 10 nm, are completely filled with liquid formulation, but there is still a certain number of pores of 40–100 nm. Dissolution studies of liquid SEDDS carried out in pH = 1.2 show that Labrasol improves the dissolution of ibuprofen as compared to the pure drug. Ibuprofen dissolution from liquid SE formulations examined in pH of 7.2 is immediate. The adsorption of the liquid onto the particles of the silicate causes a decrease in the amount of the drug released. Finally, more ibuprofen is dissolved from S-SE that consist of the neutral grade of magnesium aluminometasilicate than from the formulations containing the alkaline silicate.KEY WORDS: dissolution, ibuprofen, labrasol, magnesium aluminometasilicate, self-emulsifying powder 相似文献
144.
Fernando Oliveira Costa Luís Otávio Miranda Cota José Roberto Cortelli Sheila Cavalca Cortelli Renata Magalh?es Cyrino Eugênio José Pereira Lages Ana Paula Lima Oliveira 《PloS one》2015,10(10)
Background and Objective
Prospective studies that investigated the influence of surgical and nonsurgical procedures in the recurrence of periodontitis and tooth loss in periodontal maintenance therapy (PMT) programs have not been previously reported. The objective of this study was to evaluate longitudinally the recurrence of periodontitis in regular compliers (RC) and irregular compliers (IC) individuals undergoing surgical and non-surgical procedures over 5 years in a program of PMT.Materials and Methods
A total of 212 individuals participated in this study. Full-mouth periodontal examination including bleeding on probing, probing depth, and clinical attachment level were determined at all PMT visits over 5 years. The recurrence of periodontitis was evaluated in RC and IC individuals undergoing surgical and non-surgical procedures in PMT. The influences of risk variables of interest were tested through univariate analysis and multivariate logistic regression.Results
Recurrence of periodontitis was significantly lower among RC when compared to IC. Individuals with recurrence of periodontitis and undergoing surgical procedures showed higher probing depth and clinical attachment loss than those who received non-surgical procedures. Recurrence of periodontitis was higher in individual undergoing surgical procedures and irregular compliance during PMT.Conclusions
Irregular compliance and surgical procedures in individuals undergoing PMT presented higher rates of recurrence of periodontitis when compared to regular compliant patients undergoing non-surgical procedures. 相似文献145.
Background
Tick-borne encephalitis (TBE) presents an increasing burden in many parts of Europe, Asian Russia, Siberia, Asian former USSR and Far East. Incidence can be considered as one way to express the burden. A more comprehensive measure concerns disability-adjusted life years (DALYs), better characterizing the full burden of TBE. TBE burden in DALYs has not yet been estimated, nor has it been specified by the Global Burden of Disease (GBD) studies.Objective
The purpose of the present study is to estimate the burden of TBE in Slovenia, expressed in DALYs, both from the population and individual perspectives. We discuss the impact of TBE burden on public health and potential strategies to reduce this burden in Slovenia.Methods
The burden of TBE is estimated by using the updated DALYs'' methodology first introduced in the GBD project. The DALYs᾽ calculations are based on the health outcomes of the natural course of the disease being modelled. Corrections for under-reporting and under-ascertainment are applied. The impact of uncertainty in parameters in the model was assessed using sensitivity analyses.Results
From the population perspective, total DALYs amount to 3,450 (167.8 per 100,000 population), while from the individual perspective they amount to 3.1 per case in 2011. Notably, the consequences of TBE present a larger burden than TBE itself.Conclusions
TBE presents a relatively high burden expressed in DALYs compared with estimates for other infectious diseases from the GBD 2010 study for Slovenia. Raising awareness and increasing vaccination coverage are needed to reduce TBE and its consequences. 相似文献146.
Molecular Characterization of Subtype H11N9 Avian Influenza Virus Isolated from Shorebirds in Brazil
Renata Hurtado Thomas Fabrizio Ralph Eric Thijl Vanstreels Scott Krauss Richard J. Webby Robert G. Webster Edison Luiz Durigon 《PloS one》2015,10(12)
Migratory aquatic birds play an important role in the maintenance and spread of avian influenza viruses (AIV). Many species of aquatic migratory birds tend to use similar migration routes, also known as flyways, which serve as important circuits for the dissemination of AIV. In recent years there has been extensive surveillance of the virus in aquatic birds in the Northern Hemisphere; however in contrast only a few studies have been attempted to detect AIV in wild birds in South America. There are major flyways connecting South America to Central and North America, whereas avian migration routes between South America and the remaining continents are uncommon. As a result, it has been hypothesized that South American AIV strains would be most closely related to the strains from North America than to those from other regions in the world. We characterized the full genome of three AIV subtype H11N9 isolates obtained from ruddy turnstones (Arenaria interpres) on the Amazon coast of Brazil. For all gene segments, all three strains consistently clustered together within evolutionary lineages of AIV that had been previously described from aquatic birds in North America. In particular, the H11N9 isolates were remarkably closely related to AIV strains from shorebirds sampled at the Delaware Bay region, on the Northeastern coast of the USA, more than 5000 km away from where the isolates were retrieved. Additionally, there was also evidence of genetic similarity to AIV strains from ducks and teals from interior USA and Canada. These findings corroborate that migratory flyways of aquatic birds play an important role in determining the genetic structure of AIV in the Western hemisphere, with a strong epidemiological connectivity between North and South America. 相似文献
147.
148.
149.
150.
Malgorzata Bednarska Anna Bajer Anna Drozdowska Ewa J. Mierzejewska Katarzyna Tolkacz Renata Welc-Fal?ciak 《PloS one》2015,10(9)
Babesia spp. (Apicomplexa, Piroplasmida) are obligate parasites of many species of mammals, causing a malaria-like infection- babesiosis. Three routes of Babesia infection have been recognized to date. The main route is by a tick bite, the second is via blood transfusion. The third, vertical route of infection is poorly recognized and understood. Our study focused on vertical transmission of B. microti in a well-established mouse model. We assessed the success of this route of infection in BALB/c mice with acute and chronic infections of B. microti. In experimental groups, females were mated on the 1st day of Babesia infection (Group G0); on the 28th day post infection (dpi) in the post- acute phase of the parasite infection (G28); and on the 90th and 150th dpi (G90 and G150 group, respectively), in the chronic phase of the parasite infection. Pups were obtained from 58% of females mated in the post-acute phase (G28) and from 33% of females in groups G90 and G150. Mice mated in the pre-acute phase of infection (G0) did not deliver pups. Congenital B. microti infections were detected by PCR amplification of Babesia 18S rDNA in almost all pups (96%) from the experimental groups G28, G90 and G150. Parasitaemia in the F1 generation was low and varied between 0.01–0.001%. Vertical transmission of B. microti was demonstrated for the first time in BALB/c mice. 相似文献