首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1674篇
  免费   212篇
耳鼻咽喉   9篇
儿科学   104篇
妇产科学   36篇
基础医学   222篇
口腔科学   69篇
临床医学   265篇
内科学   265篇
皮肤病学   17篇
神经病学   135篇
特种医学   45篇
外科学   284篇
综合类   13篇
一般理论   1篇
预防医学   166篇
眼科学   16篇
药学   149篇
中国医学   1篇
肿瘤学   89篇
  2023年   26篇
  2022年   11篇
  2021年   27篇
  2020年   38篇
  2019年   44篇
  2018年   99篇
  2017年   97篇
  2016年   70篇
  2015年   76篇
  2014年   99篇
  2013年   225篇
  2012年   133篇
  2011年   143篇
  2010年   110篇
  2009年   52篇
  2008年   35篇
  2007年   13篇
  2006年   19篇
  2005年   21篇
  2004年   8篇
  2003年   11篇
  2001年   17篇
  2000年   21篇
  1999年   16篇
  1998年   26篇
  1997年   29篇
  1996年   21篇
  1995年   23篇
  1994年   19篇
  1993年   16篇
  1992年   26篇
  1991年   18篇
  1990年   13篇
  1989年   14篇
  1988年   21篇
  1987年   13篇
  1986年   8篇
  1985年   12篇
  1984年   22篇
  1983年   15篇
  1982年   22篇
  1981年   22篇
  1980年   22篇
  1979年   9篇
  1978年   7篇
  1977年   6篇
  1976年   11篇
  1975年   8篇
  1974年   10篇
  1973年   7篇
排序方式: 共有1886条查询结果,搜索用时 31 毫秒
71.

Background

Breast magnetic resonance imaging (MRI) has shown high sensitivity in determining tumor extent, multifocality, and occult contralateral breast cancer. Low specificity, unnecessary mastectomies, and costs are arguments against MRI. The purpose of this study was to determine whether preoperative breast MRI would affect primary surgical management, reduce reexcision/reoperation procedures, and influence the choice of neoadjuvant treatment in patients with newly diagnosed breast cancer.

Methods

This prospective, randomized, multicenter study included 440 breast cancer patients younger than aged 56 years from three, Swedish, large-volume breast units. Patients were randomly allocated on a 1:1 basis to either preoperative staging with breast MRI (n = 220) or no breast MRI (n = 220) (control group). Treatment planning of all patients was discussed at multidisciplinary team conferences.

Results

In patients randomized to the MRI group, who had an observed higher percentage of planned breast-conserving surgery (BCS) compared with the control group, a change from suggested breast conservation to mastectomy occurred in 23 of 153 (15 %) patients. Breast MRI provided additional information in 83 of 220 (38 %) patients, which caused a change in treatment plan in 40 (18 %). The breast reoperation rate was significantly lower in the MRI group: 11 of 220 (5 %) versus 33 of 220 (15 %) in the control group (p < 0.001). The number of mastectomies, axillary reoperations, and the number of patients receiving neoadjuvant chemotherapy after definitive treatment did not differ significantly between the groups.

Conclusions

Preoperative staging with breast MRI in women younger than age 56 years altered the treatment plan in 18 % of the patients. Although a higher MRI-related conversion rate from breast conservation to mastectomy was found, the final numbers of mastectomies did not differ between the two groups. The breast reoperation rate in the MRI group was significantly reduced.  相似文献   
72.
We evaluated secreted wingless (Wnt) modulators during cytomegalovirus (CMV) infection in solid organ transplant recipients (SOTr). The major findings were: (i) Plasma levels of Dickkopf‐1 (DKK‐1) were significantly lower in patients with CMV DNAemia above lower level of quantification at baseline. (ii) Receiver operating characteristic analysis indicated that low DKK‐1 and increased secreted frizzled related protein‐3 levels were predictors of poor virological outcomes during follow‐up. Our findings demonstrate an imbalanced pattern of circulating secreted Wnt modulators in SOTr with poor virological outcomes following treatment for CMV disease, and may suggest a role for dysregulated Wnt signaling on viral pathogenesis during CMV infection.  相似文献   
73.

Purpose

Tacrolimus (Tac) and cyclosporine (CsA) are mainly metabolized by CYP3A4 and CYP3A5. Several studies have demonstrated an association between the CYP3A5 genotype and Tac dose requirements. Recently, CYP3A4, PPARA, and POR gene variants have been shown to influence CYP3A metabolism. The present study investigated potential associations between CYP3A5*3, CYP3A4*22, PPARA c.209-1003G>A and c.208?+?3819A>G, and POR*28 alleles and dose-adjusted concentrations (C/D) of Tac and CsA in 177 renal transplant patients early post-transplant.

Methods

All patients (n?=?177) were genotyped for CYP3A4*22, CYP3A5*3, POR*28, PPARA c.209-1003G>A, and PPARA c.208?+?3819A>G using real-time polymerase chain reaction (PCR) and melting curve analysis with allele-specific hybridization probes or PCR restriction fragment length polymorphisms (RFLP) methods. Drug concentrations and administered doses were retrospectively collected from patient charts at Oslo University Hospital, Rikshospitalet, Norway. One steady-state concentration was collected for each patient.

Results

We confirmed a significant impact of the CYP3A5*3 allele on Tac exposure. Patients with POR*28 and PPARA variant alleles demonstrated 15 % lower (P?=?0.04) and 19 % higher (P?=?0.01) Tac C0/D respectively. CsA C2/D was 53 % higher among CYP3A4*22 carriers (P?=?0.03).

Conclusion

The results support the use of pre-transplant CYP3A5 genotyping to improve initial dosing of Tac, and suggest that Tac dosing may be further individualized by additional POR and PPARA genotyping. Furthermore, initial CsA dosing may be improved by pre-transplant CYP3A4*22 determination.  相似文献   
74.
The acute pulmonary responses after exposure to sulfur and nitrogen mustards are well documented whereas the late pulmonary effects are not. With a novel focus on the immune system this paper investigate whether late phase pulmonary effects developed in rats exposed to the nitrogen mustard melphalan are linked to the acute responses and whether the reactions are genetically regulated. The DA rat strain was used to establish a lung exposure model. Five other inbred rat strains (PVG, PVG.1AV1, LEW, WF and F344) were compared within the model at selected time points. All rat strains displayed a biphasic pattern of leukocyte infiltration in the lungs, dominated by neutrophils 2 days after exposure and a second peak dominated by macrophages 29 days after exposure. The number of macrophages was higher in the DA rat compared with the other strains. The infiltration of lymphocytes in the lungs varied in both time of appearance and magnitude between strains. The quantity of collagen deposition in the lungs varied between strains at day 90; LEW and WF displayed high collagen content which coincided with an increased level of cytotoxic T cells. LEW further displayed an increased number of T helper cells and natural killer (NK) T cells in the lungs. The results in this study suggest there is a link between the development of lung fibrosis and high cytotoxic cell responses and that there is a genetic influence, as there are variations in acute and late adverse reactions between rat strains in both timing and magnitude. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
75.
76.
AimsTo assess if individuals with diabetes or prediabetes report more pain or have increased use of pain medication compared to normoglycaemic individuals.MethodsUsing cross-sectional data, we studied 928 men and 1075 women from the Helsinki Birth Cohort Study in 2001–2004 at a mean age of 61.5 years. Glucose regulation was assessed with a 2-h 75 g oral glucose tolerance test, and applying World Health Organization criteria, participants were defined as having normoglycaemia, prediabetes (impaired fasting glucose or impaired glucose tolerance), newly diagnosed diabetes or previously diagnosed diabetes. Self-reported pain intensity and interference during the previous 4 weeks was estimated using the RAND 36-Item Health Survey 1.0. Information on use of pain medication during the past 12 months was obtained from the Social Insurance Institution of Finland.ResultsThere was no difference in pain intensity or interference between glucose regulation groups for neither men nor women after adjusting for covariates (age, body mass index, education years, Beck Depression Inventory and physical activity). In addition, use of pain medication was similar between glucose regulation groups.ConclusionsAlthough pain is a common symptom in the general population, impairments in glucose regulation alone does not seem to increase pain among older individuals.  相似文献   
77.
78.
Calprotectin in plasma and blood might prove to be a useful biomarker of inflammation and infection; however, automated methods for analysing the concentration of calprotectin in those materials are lacking. We have validated a fully automated turbidimetric method and present health-related reference limits. Calprotectin was measured by Siemens Advia XPT with the Bühlmann fCAL® turbo test (Bühlmann Laboratories AG, Schönenbuch, Switzerland), a particle enhanced turbidimetric immunoassay for quantification of calprotectin in fecal extracts. Plasma and serum samples were analysed directly, while whole blood was first extracted with M-PER® Mammalian Protein Extraction Reagent (ThermoFisher) and diluted with B-CAL-EX (Bühlmann). We studied analytical imprecision, estimated health-related reference limits and examined the correlation between neutrophil-calprotectin (blood-calprotectin adjusted for plasma-calprotectin) and the neutrophil count. The intermediate (‘day-to-day’) coefficient of variation was 3.5 and 1.0% for heparin-plasma-calprotectin at 0.52?mg/L and 3.53?mg/L, respectively, and 4.9% for heparin-blood-calprotectin at 50.2?mg/L. Health-related reference limits were 0.470–3.02?mg/L for calprotectin in heparin-plasma, 50.8–182?mg/L for calprotectin in heparin-blood, 0.534–2.41% for the ratio between them and 24.7–33.3?pg for the mean amount of calprotectin per neutrophil. Compared to heparin-plasma, calprotectin concentrations were significantly lower in EDTA-plasma and higher in serum (p?<?.05). Correlation between neutrophil-calprotectin and the neutrophil count was excellent. We have shown that the Bühlmann fCAL® turbo test can be used to measure calprotectin in plasma and blood.  相似文献   
79.

Purpose

The clinical diagnosis of pulmonary sarcoidosis is based on the presence of noncaseating granulomas in an appropriate clinical setting with either bilateral hilar adenopathy and/or parenchymal infiltrates. Lymphocytosis with an increased CD4/CD8 T cell ratio in bronchoalveolar lavage fluid is supportive. We evaluated the diagnostic accuracy of a predictive binary logistic regression model in sarcoidosis based on sex, age, and bronchoalveolar lavage fluid cell profile with and without the inclusion of HLA-DR+ CD8+ T cells and natural killer T-cell fractions.

Methods

A retrospective analysis of differential cell counts and lymphocyte phenotypes by flow cytometry in bronchoalveolar lavage was performed in 183 patients investigated for possible diffuse parenchymal lung disease. A logistic regression model with age, sex, lymphocyte fraction, eosinophils, and CD4/CD8 ratio in bronchoalveolar lavage fluid (basic model) was compared with a final model, which also included fractions of HLA-DR+ CD8+ T cells and natural killer T cells. Diagnostic accuracy of the two models was assessed by receiver operating characteristic (ROC) curves.

Results

The area under the ROC curve for the basic and final model was 0.898 [95 % confidence interval (CI) 0.852–0.945] and 0.937 (95 % CI 0.902–0.972), respectively, p = 0.008.

Conclusions

Assessment of HLA-DR+ CD8+ T cell and natural killer T-cell fractions may improve diagnostic accuracy and further strengthen the importance of bronchoalveolar lavage in the diagnostic workup of sarcoidosis.  相似文献   
80.
Pseudomonas aeruginosa PAO1 (tobramycin MIC?=?0.064 µg/mL) was used to perform agar diffusion tests employing tobramycin-containing tablets. Bacterial growth and formation of inhibition zones were studied by stereomicroscopy and by blotting with microscope slides and staining with methylene blue, Alcian blue and a fluorescent lectin for the P. aeruginosa PSL, which was studied by confocal laser scanning microscopy. Diffusion of tobramycin from the deposit was modelled using a 3D geometric version of Fick's second law of diffusion. The time-dependent gradual increase in the minimum biofilm eradication concentration (MBEC) was studied using a Calgary Biofilm Device. The early inhibition zone was visible after 5 h of incubation. The corresponding calculated tobramycin concentration at the border was 1.9 µg/mL, which increased to 3.2 µg/mL and 6.3 µg/mL after 7 h and 24 h, respectively. The inhibition zone increased to the stable final zone after 7 h of incubation. Bacterial growth and small aggregate formation (young biofilms) took place inside the inhibition zone until the small aggregates contained less than ca. 64 cells and production of polysaccharide matrix including PSL had begun; thereafter, the small bacterial aggregates were killed by tobramycin. Bacteria at the border of the stable inhibition zone and beyond continued to grow to a mature biofilm and produced large amount of polysaccharide-containing matrix. Formation of the inhibition zone during agar diffusion antimicrobial susceptibility testing is due to a switch from a planktonic to biofilm mode of growth and gives clinically important information about the increased antimicrobial tolerance of biofilms.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号