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   2003篇
  免费   103篇
  国内免费   17篇
耳鼻咽喉   25篇
儿科学   52篇
妇产科学   91篇
基础医学   202篇
口腔科学   45篇
临床医学   143篇
内科学   443篇
皮肤病学   29篇
神经病学   69篇
特种医学   128篇
外国民族医学   1篇
外科学   470篇
综合类   32篇
预防医学   101篇
眼科学   51篇
药学   113篇
中国医学   3篇
肿瘤学   125篇
  2023年   18篇
  2022年   45篇
  2021年   68篇
  2020年   58篇
  2019年   67篇
  2018年   121篇
  2017年   78篇
  2016年   49篇
  2015年   67篇
  2014年   105篇
  2013年   105篇
  2012年   145篇
  2011年   143篇
  2010年   89篇
  2009年   82篇
  2008年   110篇
  2007年   114篇
  2006年   114篇
  2005年   111篇
  2004年   93篇
  2003年   75篇
  2002年   67篇
  2001年   16篇
  2000年   15篇
  1999年   12篇
  1998年   10篇
  1997年   5篇
  1996年   12篇
  1995年   11篇
  1994年   7篇
  1993年   11篇
  1992年   11篇
  1991年   9篇
  1990年   9篇
  1989年   7篇
  1988年   6篇
  1987年   8篇
  1986年   4篇
  1985年   3篇
  1984年   2篇
  1983年   4篇
  1981年   4篇
  1980年   3篇
  1978年   3篇
  1976年   5篇
  1975年   2篇
  1969年   2篇
  1968年   2篇
  1967年   2篇
  1965年   3篇
排序方式: 共有2123条查询结果,搜索用时 15 毫秒
31.
We measured serum interleukin-2 receptor (sIL-2R), tumor necrosis factor-a (TNF-a), Fas receptor (sFas), nitric oxide (NO), and angiotensin converting enzyme (ACE) activity in 45 patients with congestive heart failure (CHF) of different etiologies. The relatioship between these bioindices and the severity of heart failure was analysed. Patients were classified according to the etiology of heart failure into: 15 patients with rheumatic valvular heart disease (RHD), 17 with ischemic heart disease (IHD) and 13 with idiopathic dilated cardiomyopathy (DCM). Patients were further classified according to severity of CHF following the New York Heart Association classification (NYHA) into: NYHA class II (n= 7), NYHA class III (n=20) and NYHA class IV (n=18). Eighteen healthy subjects were included as controls. Serum sIL-2R, TNF-alpha and sFas levels were determined by ELISA while serum NO and ACE levels were measured by colorimetric methods. Doppler Echocardiography was performed for all participants. Levels of sIL-2R, TNF-alpha, sFas, NO, and ACE were significantly higher in CHF patients than controls. Levels of the bioindices varied according to the CHF etiology. TNF-a level was the only one that had significant differences among different subgroups (RHD, IHD and DCM). The levels of sIL-2R, TNF-alpha, NO and sFas in patients with NYHA class IV were significantly higher than class II or III. Moreover, sIL-2R, TNF-alpha and NO levels were significantly higher in patients with diastolic dysfunction than patients with normal diastolic function. A significant positive correlations were found between sFas and both TNF-alpha and sIL-2R and between TNF-alpha and both NO and diastolic function. In addition, significant positive correlations were found between TNF-alpha and sIL-2R in both IHD and RHD patients and between sIL-2R and both ACE in IHD patients and diastolic function in DCM patients. It is concluded that a relationship exists between immune system activation, apoptosis and renin- angiotensin system in CHF and this may play a significant role in the pathophysiology and prognosis of the disease.  相似文献   
32.
33.
34.
Purpose

The purpose of the study was to determine if the ≥ 15 mm threshold currently used to define PIRADS 5 lesions is the optimal size threshold for predicting high likelihood of clinically significant (CS) cancers.

Materials

Three hundred and fifty-eight lesions that may be changed from category 4 to 5 or vice versa on the basis of the size criterion (category 4: n = 288, category 5: n = 70) from 255 patients were evaluated. Kendall’s tau-b statistic accounting for inter-lesion correlation, generalized estimation equation logistic regression, and receiver operating curve analysis evaluated two lesion size-metrics (lesion diameter and relative lesion diameter—defined as lesion diameter/prostate volume) for ability to identify CS (Gleason grade ≥ 3 + 4) cancer at targeted biopsy. Optimal cut-points were identified using the Youden index. Analyses were performed for the whole prostate (WP) and zone-specific sub-cohorts of lesions in the peripheral and transition zones (PZ and TZ).

Results

Lesion diameter showed a modest correlation with Gleason grade (WP: τB = 0.21, p < 0.0001; PZ: τB = 0.13, p = 0.02; TZ: τB = 0.32, p = 0.001), and association with CS cancer detection (WP: AUC = 0.63, PZ: AUC = 0.59, TZ: AUC = 0.74). Empirically derived thresholds (WP: 14 mm, PZ: 13 mm, TZ: 16 mm) performed similarly to the current ≥ 15 mm standard. Lesion relative lesion diameter improved identification of CS cancers compared to lesion diameter alone (WP: τB = 0.30, PZ: τB = 0.24, TZ: τB = 0.42, all p < 0.0001). AUC also improved for WP and PZ lesions (WP: AUC = 0.70, PZ: AUC = 0.68, and TZ: AUC = 0.74).

Conclusions

The current ≥ 15 mm diameter threshold is a reasonable delineator of PI-RADS category 4 and category 5 lesions in the absence of extraprostatic extension to predict CS cancers. Additionally, relative lesion diameter can improve identification of CS cancers and may serve as another option for distinguishing category 4 and 5 lesions.

  相似文献   
35.
Emergency Radiology - To correlate thromboembolic (TE) complications secondary to COVID-19 with the extent of the pulmonary parenchymal disease using CT severity scores and other comorbidities. In...  相似文献   
36.
Gross studies of skin reactions to adult antigen of Schistosoma mansoni were made on 156 hospitalized patients with schistosomiasis and 114 subjects from the nonendemic area of Hurghada in Egypt. Wheal areas equal to or greater than 1.0 cm2 indicated a positive immediate (15-min) reaction to adult worm antigen; the criterion of positivity for both 24-hour and 48-hour delayed reactions was an area of induration equal to or greater than 0.6 cm2. Immediate reactions with adult worm antigen were observed in 99% of the patients with schistosomiasis and 11% of the subjects from Hurghada: the percentages with delayed reaction were 58% and 2%, respectively. Biopsies of skin test sites at various intervals after antigen injection were done on 87 individuals. Eosinophilic and mononuclear infiltrates were characteristic of immediate and delayed skin responses, respectively. Biopsies from 22 patients with marked skin reactions 5 hours after antigen injection showed that a neutrophilic response indicative of Arthus reactivity was present in only 18. Thus, Arthus reactivity could not be determined on gross appearance alone. The studies did not show any evidence of delayed basophilic hypersensitivity to schistosome antigen. Immunofluorescent studies on a small number of biopsies suggested that a late phase (5-hour) reaction due to IgE may occur in some patients. Delayed reactivity to mumps and/or monilia skin test antigens was observed in 91% of Egyptians in a nonendemic area of schistosomiasis. Delayed hypersensitivity to PPD was detected in 44% of the same group.  相似文献   
37.
BACKGROUND: There is a paucity of data on the long-term outcome of alcohol septal ablation (ASA) for symptomatic hypertrophic obstructive cardiomyopathy (HOCM). HYPOTHESIS: The study was undertaken to evaluate the longer-term outcome of ASA therapy for symptomatic HOCM. METHODS: In all, 137 patients were enrolled consecutively (1996-1999) and 130 (95%) (74 men, 56 women, aged 51 +/- 17 years) underwent ASA and had serial prospective follow-up for up to 5 years (mean follow-up 3.6 +/- 1.4 years). Evaluation included angina (Canadian Cardiovascular Society [CCS] score), dyspnea (New York Heart Association [NYHA] class), duration of exercise on treadmill, and echocardiographic indices. RESULTS: Ethanol (3.5 +/- 1.5 cc), injected into 1.5 +/- 0.6 arteries, induced a mean peak plasma creatine kinase (CK) of 1676 +/- 944 units. Complications of procedures included death 1.5% (2/130), heart block requiring permanent pacemaker 13% (17/130), and coronary dissection 4.4% (6/130). Baseline versus last follow-up visit: NYHA class decreased from 3.0 +/- 0.4 to 1.2 +/- 0.6 (p < 0.01); CCS angina score from 2.0 +/- 0.8 to 0.08 +/- 0.4 (p < 0.01); and duration of exercise increased from 322 +/- 207 to 443 +/- 200 s (p < 0.01). Resting left ventricular outflow tract gradient at baseline versus last follow-up visit showed a decrease from 74 +/- 30 to 4 +/- 13 (p < 0.01), and the dobutamine-provoked gradient of 88 +/- 29 decreased to 21 +/- 21 (p < 0.01) mmHg. All-cause mortality over the duration of follow-up was 7.7% (10) giving an annual rate of 2.1%, and cardiac mortality was 2.3% (3) reflecting an annual rate of 0.6%. CONCLUSIONS: Alcohol septal ablation decreased symptoms and improved exercise performance, indicating that it is an effective procedure for symptomatic HOCM.  相似文献   
38.
In Caucasian hypertensives and diabetics, increased RBC sodium-lithium countertransporter activity (SLC) is a marker for end-organ complications of vascular disease. A subgroup of African Americans with high Vmax for SLC show strong correlations with dyslipidaemia, insulin resistance, microalbuminuria and higher blood pressure. The purpose of our study was to determine if Vmax in premenopausal African American women correlates with left ventricular mass (LVM) before the onset of clinically diagnosed hypertension. Non-diabetic African American women (n = 35, mean age 31 years) were evaluated for cardiovascular disease risk factors, including anthropometric and blood pressure measurements, oral glucose tolerance test (OGTT), and euglycaemic hyperinsulinaemic clamp for insulin sensitivity. Fasting blood specimens were assayed for SLC activity (Vmax) and lipids. Cardiac structure was determined by 2-D echocardiography. LVM was calculated by the cube root formula and adjusted for height (LVM index). Vmax correlated significantly with average systolic blood pressure (r = 0.45, P = 0.007), diastolic blood pressure (r = 0.48, P = 0.004), mean blood pressure (r = 0.48, P = 0.003) and LVM index (r = 0.40, P = 0.02). Vmax was also associated with fasting insulin (r = 0.39, P = 0.01), the sum of insulin (r = 0.52, P = 0.002), and insulin sensitivity adjusted for fat-free mass (r = -0.55, P = 0.001). There was no statistically significant relationship between Vmax and body mass or lipids. Vmax for SLC correlates with cardiac structure in premenopausal African American women. Vmax is also associated with insulin sensitivity and insulin resistance in this non-diabetic sample. SLC activity may be useful in identifying a subgroup of young African American women with left ventricular hypertrophy and insulin resistance before the onset of clinically diagnosed hypertension and diabetes. Journal of Human Hypertension (2000) 14, 213-219.  相似文献   
39.
There has not been as much success in the prevention and treatment of invasive fungal infections, particularly aspergillosis, compared to the prevention and treatment of cytomegalovirus infection and graft-versus-host disease in bone marrow transplant (BMT) recipients. Allogeneic BMT recipients who develop graft-versus-host disease and remain immunosuppressed for long periods are at major risk for development of these infections. Prevention of environmental exposure, antifungal chemoprophylaxis, and attempts at early diagnosis are essential for the reduction of mortality from invasive fungal infections. Chest computerized axial tomography is extremely useful in diagnosing pulmonary aspergillosis. However, microbiologic or histologic identification of infection remains essential. Unfortunately, the response to therapy in BMT recipients remains suboptimal. With the development of the lipid formulations of amphotericin B, the newer azoles, and the echinocandins, safer and more efficacious options have become available. The optimal use of antifungal agents or their combinations remains to be determined.  相似文献   
40.
IntroductionDNA methylation constitutes one important epigenetic mechanism that regulates gene expression in human cells. With regard to obesity, bariatric surgery-induced weight loss has been associated with promoter methylation changes in several genes. Hyperleptinemia is a characteristic feature of obesity. The underlying regulating mechanisms have not yet been completely elucidated.MethodsWe investigated the methylation of the promoters of the leptin gene (LEP) and the leptin receptor gene (LEPR) as well as leptin expression in pre- and postbariatric surgery patients using a comparative cross-sectional design.ResultsOur results revealed significantly higher LEP promoter methylation patterns in prebariatric surgery patients compared to postoperatively. DNA methylation of the LEPR promoter was significantly higher in the postoperative group. Moreover, we found significantly higher leptin serum levels in patients before the bariatric surgery than afterwards.DiscussionThese findings strengthen the suggestion that there is an association between LEP expression and LEP methylation in obesity. We suggest that the epigenetic profile of LEP might be influenced by leptin serum levels in the form of a regulating feedback mechanism.  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