全文获取类型
收费全文 | 1019篇 |
免费 | 48篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 27篇 |
儿科学 | 13篇 |
妇产科学 | 18篇 |
基础医学 | 143篇 |
口腔科学 | 173篇 |
临床医学 | 84篇 |
内科学 | 188篇 |
皮肤病学 | 37篇 |
神经病学 | 78篇 |
特种医学 | 28篇 |
外科学 | 84篇 |
综合类 | 7篇 |
预防医学 | 98篇 |
眼科学 | 10篇 |
药学 | 59篇 |
中国医学 | 6篇 |
肿瘤学 | 21篇 |
出版年
2023年 | 13篇 |
2022年 | 28篇 |
2021年 | 66篇 |
2020年 | 41篇 |
2019年 | 43篇 |
2018年 | 54篇 |
2017年 | 33篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 66篇 |
2013年 | 66篇 |
2012年 | 94篇 |
2011年 | 114篇 |
2010年 | 57篇 |
2009年 | 29篇 |
2008年 | 69篇 |
2007年 | 50篇 |
2006年 | 31篇 |
2005年 | 37篇 |
2004年 | 19篇 |
2003年 | 19篇 |
2002年 | 21篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1936年 | 2篇 |
排序方式: 共有1074条查询结果,搜索用时 15 毫秒
41.
Intraspinal neural stem cell transplantation in amyotrophic lateral sclerosis: Phase 1 trial outcomes 下载免费PDF全文
42.
Rosenkrantz AB Mussi TC Spieler B Melamed J Taneja SS Huang WC 《Journal of magnetic resonance imaging : JMRI》2012,35(6):1478-1483
Purpose:
To assess the utility of apparent diffusion coefficient (ADC) values obtained from diffusion‐weighted imaging (DWI) in distinguishing high‐grade bladder cancer with and without metastatic disease.Materials and Methods:
Seventeen patients with histologically confirmed high‐grade bladder cancer who underwent pelvic magnetic resonance imaging (MRI) at 1.5T including DWI using b‐values of 0, 400, and 800 sec/mm2 were assessed. Histologic findings and follow‐up imaging were used to establish the reference standard in terms of metastatic disease. Two radiologists independently recorded ADC of all lesions following a training session, with their results averaged. Mann–Whitney U‐test, receiver operating characteristic (ROC) curve analysis and intraclass correlation coefficient (ICC) were used for data analysis.Results:
Metastatic disease was characterized as present or absent in eight and nine patients, respectively. ADC was significantly lower among cases with metastatic disease than among cases without metastatic disease, both within the entire cohort (1.07 ± 0.18 × 10?3 mm2/s vs. 1.45 ± 0.22 × 10?3 mm2/s; P = 0.002) and within the subset of patients with muscle‐invasive tumor (1.06 ± 0.19 × 10?3 mm2/s vs. 1.45 ± 0.23 × 10?3 mm2/s; P = 0.017). Area under the ROC curve for identifying metastatic disease using ADC was 0.944, with optimal threshold of 1.21 × 10?3 mm2/s, which was associated with a sensitivity of 87.5%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 90.0%. Interreader agreement for ADC was excellent (ICC = 0.91).Conclusion:
In this preliminary study, ADC was significantly different between cases of high‐grade urothelial carcinoma of the bladder with and without metastatic disease. These results may have value in assessing the metastatic potential of patients with localized high‐grade tumors of the bladder. J. Magn. Reson. Imaging 2012;35:1478–1483. © 2012 Wiley Periodicals, Inc.43.
44.
45.
Meyer-Fernandes JR Saad-Nehme J Peres-Sampaio CE Belmont-Firpo R Bisaggio DF Do Couto LC Fonseca De Souza AL Lopes AH Souto-Padrón T 《Parasitology research》2004,93(1):41-50
In this work, we describe the ability of living epimastigotes of Trypanosoma cruzi to hydrolyze extracellular ATP. In these intact parasites, there was a low level of ATP hydrolysis in the absence of any divalent metal (2.42±0.31 nmol Pi/h×108 cells). ATP hydrolysis was stimulated by MgCl2, and the Mg-dependent ecto-ATPase activity was 27.15±2.91 nmol Pi/h×108 cells. The addition of MgCl2 to the extracellular medium increased the ecto-ATPase activity in a dose-dependent manner. This stimulatory activity was also observed when MgCl2 was replaced by MnCl2, but not by CaCl2 or SrCl2. The apparent Km for Mg-ATP2– was 0.61 mM, and free Mg2+ did not increase the ecto-ATPase activity. This ecto-ATPase activity was insensitive to the inhibitors of other ATPase and phosphatase activities. To confirm that this Mg-dependent ATPase was an ecto-ATPase, we used an impermeant inhibitor, DIDS (4, 4.diisothiocyanostylbene 2-2-disulfonic acid) as well as suramin, an antagonist of P2 purinoreceptors and inhibitor of some ecto-ATPases. These two reagents inhibited the Mg2+-dependent ATPase activity in a dose-dependent manner. A comparison among the Mg2+-ecto-ATPase activities of the three forms of T. cruzi showed that the noninfective epimastigotes were less efficient at hydrolyzing ATP than the infective trypomastigote and amastigote stages. 相似文献
46.
47.
Giselli Matsumoto Rodolfo de Paula Vieira Thais Mauad Carmen Diva Saldiva de André Paulo Hilário Nascimento Saldiva 《Environmental research》2010,110(3):237-243
The present study aimed to verify the time course of the effects of environmental levels of urban air pollution toxicity on lung arterioles. BALB/c mice (n=56) were continuously exposed to selective chambers equipped with (filtered, F) or without (non-filtered, NF) filter devices for particles and toxic gases for 24 h/day, over 14, 21, 30 or 45 days. After exposure, we evaluated the lumen-wall relationship (an estimator of arteriolar narrowing), endothelial nitric oxide synthase (eNOS) and endothelin type A receptor (ETAr) expression in the vascular wall and inflammatory influx of the peribronchiolar area. Concentrations of fine particulate matter (PM≤2.5 μg/m3), nitrogen dioxide (NO2), black smoke (BS), humidity and temperature in both the environment and inside the chambers were measured daily. Filters cleared 100% of BS and 97% of PM inside the F chamber. The arteriole wall of the lungs of mice from NF chamber had an increased ETAr expression (p≤0.042) concomitant to a decrease in the lumen/wall ratio (p=0.02) on the early days of exposure, compared to controls. They also presented a progressive increment of inflammatory influx in the peribronchiolar area during the study (p=0.04) and decrement of the eNOS expression on the 45th day of exposure in both vascular layers (p≤0.03). We found that after 14 days of exposure, the ambient levels of air pollutants in Sao Paulo induced vasoconstriction that was associated with an increase in ETAr expression. These vascular results do not appear to be coupled to the progressive inflammatory influx in lung tissue, suggesting a down-regulation of vasoconstrictive mechanisms through an imbalance in the cytokines network. It is likely that these responses are protective measures that decrease tissue damage brought about by continuous exposure to air pollutants. 相似文献
48.
Xavier AC Siqueira SA Costa LJ Mauad T Nascimento Saldiva PH 《Virchows Archiv : an international journal of pathology》2005,446(3):225-231
Autopsy findings of missed diagnoses that would probably have changed management or prognosis occur in up to 29% of cases in general hospitals. Such proportions may be higher in subsets of patients with complex diseases. We reviewed 2908 consecutive autopsies performed over a period of 29 months in a large-volume hospital, analyzing 118 autopsies of patients with hematological malignancies or severe aplastic anemia. A review of macroscopic reports as well as microscopic examination of tissue samples was performed. Medical records were reviewed for clinical diagnoses. Discordances between clinical and autopsy diagnoses were classified using Goldmans criteria. Additionally, we searched for clinical parameters correlated with occurrence of class-I discrepancy using a multivariate method. Median age was 46.5 years, and 25.4% had received a hematopoietic stem-cell transplant. Overall, 11.9% (6.6–19.1%) of patients died before conclusion of the hematological diagnosis and 33% (24.6–42.3%) died with no active hematological disease. We found class-I discrepancy in 31.3% (23.1–40.5 %) of cases. The most common among these diagnoses were hematological disease, pneumonia and gastrointestinal bleeding. In a univariate analysis, being elderly (P=0.04) was positively correlated with the finding of class-I discrepancies; while, having received previous specific hematological treatment (P=0.0005) or hematopoietic stem-cell transplants (P=0.013), or being admitted to a specialized hematology unit (P=0.0006) were negatively correlated to the occurrence of such discrepancies. Multivariate analysis showed that care in a specialized hematology unit (OR 0.34, 0.12–0.93) was independently associated with lower occurrence of discrepancies. We concluded that critical diagnoses are often missed in highly complex hematological patients especially in the absence of admission to specialized hematology units. 相似文献
49.
Forte Lucas Dantas Maia de Almeida Rodrigues Natália Cordeiro André Vitor de Fante Thais de Paula Simino Laís Angélica de Souza Torsoni Adriana Torsoni Márcio Alberto Gobatto Claudio Alexandre Barros Manchado-Gobatto Fúlvia 《Journal of muscle research and cell motility》2022,43(1):35-44
Journal of Muscle Research and Cell Motility - Acute metabolic and molecular response to exercise may vary according to exercise’s intensity and duration. However, there is a lack regarding... 相似文献
50.
Rossi FS Mascaretti RS Haddad LB Freddi NA Mauad T Rebello CM 《Clinics (S?o Paulo, Brazil)》2008,63(2):237-244
INTRODUCTION: Studies comparing high frequency oscillatory and conventional ventilation in acute respiratory distress syndrome have used low values of positive end-expiratory pressure and identified a need for better recruitment and pulmonary stability with high frequency. OBJECTIVE: To compare conventional and high frequency ventilation using the lower inflection point of the pressure-volume curve as the determinant of positive end-expiratory pressure to obtain similar levels of recruitment and alveolar stability. METHODS: After lung lavage of adult rabbits and lower inflection point determination, two groups were randomized: conventional (positive end-expiratory pressure = lower inflection point; tidal volume=6 ml/kg) and high frequency ventilation (mean airway pressures= lower inflection point +4 cmH2O). Blood gas and hemodynamic data were recorded over 4 h. After sacrifice, protein analysis from lung lavage and histologic evaluation were performed. RESULTS: The oxygenation parameters, protein and histological data were similar, except for the fact that significantly more normal alveoli were observed upon protective ventilation. High frequency ventilation led to lower PaCO2 levels. DISCUSSION: Determination of the lower inflection point of the pressure-volume curve is important for setting the minimum end expiratory pressure needed to keep the airways opened. This is useful when comparing different strategies to treat severe respiratory insufficiency, optimizing conventional ventilation, improving oxygenation and reducing lung injury. CONCLUSIONS: Utilization of the lower inflection point of the pressure-volume curve in the ventilation strategies considered in this study resulted in comparable efficacy with regards to oxygenation and hemodynamics, a high PaCO2 level and a lower pH. In addition, a greater number of normal alveoli were found after protective conventional ventilation in an animal model of acute respiratory distress syndrome. 相似文献