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   5322篇
  免费   235篇
  国内免费   27篇
耳鼻咽喉   70篇
儿科学   136篇
妇产科学   141篇
基础医学   522篇
口腔科学   120篇
临床医学   380篇
内科学   1471篇
皮肤病学   19篇
神经病学   632篇
特种医学   303篇
外科学   774篇
综合类   11篇
预防医学   163篇
眼科学   53篇
药学   241篇
中国医学   9篇
肿瘤学   539篇
  2024年   4篇
  2023年   64篇
  2022年   48篇
  2021年   214篇
  2020年   117篇
  2019年   127篇
  2018年   199篇
  2017年   119篇
  2016年   158篇
  2015年   167篇
  2014年   256篇
  2013年   275篇
  2012年   461篇
  2011年   421篇
  2010年   217篇
  2009年   246篇
  2008年   349篇
  2007年   336篇
  2006年   346篇
  2005年   331篇
  2004年   267篇
  2003年   261篇
  2002年   195篇
  2001年   39篇
  2000年   30篇
  1999年   38篇
  1998年   33篇
  1997年   28篇
  1996年   15篇
  1995年   22篇
  1994年   12篇
  1993年   15篇
  1992年   18篇
  1991年   22篇
  1990年   12篇
  1989年   10篇
  1988年   16篇
  1987年   6篇
  1986年   11篇
  1985年   12篇
  1984年   12篇
  1983年   3篇
  1982年   3篇
  1981年   3篇
  1980年   5篇
  1979年   8篇
  1978年   4篇
  1972年   4篇
  1971年   2篇
  1967年   2篇
排序方式: 共有5584条查询结果,搜索用时 453 毫秒
101.
Purpose

To compare the accuracy of Contrast-Enhanced Spectral Mammography (CESM), MG, US, and breast MRI in estimating the size of breast lesions requiring surgery. The postoperative histology size of the lesion was used as the gold standard.

Material and methods

Two hundred thirty-three non-benign lesions in 189 patients were included in the analyses. All the selected patients underwent CESM and at least one other conventional diagnostic exam (US, MG, or MRI). Subsequently, all the patients underwent surgery preceded by cytological/histological examination. The largest diameter of the lesion at imaging was measured by a radiologist with more than 10 years’ experience and then compared with the size of the lesion in the histological sample at the surgery (gold standard).

Results

Among the 233 breast lesions, 196 were evaluated with US, 206 with MG and 160 with MRI. We found no statistically significant differences between size measurements using CESM and MRI compared with the measurements at the surgery (p value 0.63 and 0.51), whereas a significant difference was found for MG and US (p?<?0.001).

Conclusion

CESM is a reliable method for estimating the size of breast lesions: its performance seems superior to US and MG and comparable to MRI.

  相似文献   
102.
OBJECTIVE: In this prospective study we evaluate the effects of high-dose recombinant human erythropoietin (rHuEPO) on quality of life (QOL) and brain function in patients with low-risk myelodysplastic syndromes (MDS) (<10% marrow blasts). Preliminary data are reported. METHODS: Eleven consecutive patients were given rHuEPO (40,000 IU two times a week) for 12 wk. Responsive patients continued with 40,000 IU/wk for further 12 wk. Changes in QOL were assessed by the Functional Assessment of Cancer Therapy-Anemia (FACT-An) self-report. Neurophysiological evaluation at the start of the therapy (t0) included duplex scanning of neck vessels, transcranial Doppler sonography (TCD), a complex neuropsychological evaluation, and quantitative electroencephalography (qEEG). Eight patients completed the neurophysiological evaluation after 24 wk (t1). RESULTS: Six patients (55%) achieved an erythroid response after 12 wk, which was maintained after 24 wk of treatment. FACT-An score showed a relevant improvement between t0 and t1 in these patients. At baseline, TCD showed a mean cerebral blood flow (CBF) velocity in the upper normal range. Abnormalities in brain function were observed in five patients. In the eight patients who were re-evaluated at t1, improvement was observed in three responding patients, two of them with abnormal values at t0. A strict correlation between QOL and neurophysiological improvements was not observed. CONCLUSIONS: A high-dose induction phase with rHuEPO followed by maintenance therapy may be an effective therapeutic schedule for low-risk MDS patients. The erythroid response was associated with positive changes in the QOL. Neurophysiological improvements occurred only in a part (50%) of responding patients, mainly those who showed altered results at baseline.  相似文献   
103.
104.
Since melatonin receptors are present in the intestines, the possibility that this hormone may affect intestinal motility has been studied in the rat. Sprague-Dawley male rats were given a carmine cochineal powder meal and were injected intraperitoneally with 1, 10, 100, or 1000 g/kg melatonin. Sixty minutes after treatment, intestinal transit was found to be faster in animals treated with small doses of melatonin (1 or 10 g/kg) than in saline-injected controls. This effect, however, appear to be clearly reversed with 100 or 1000 g/kg melatonin. In fact, these doses of the hormone reduced intestinal transit in rats. The nonselective melatonin receptor antagonist, luzindole (administered intraperitoneally in a dose of 0.25 mg/kg, 15 min prior to melatonin injection) totally prevented the accelerating effect of melatonin (10 g/kg) on intestinal transit. Luzindole per se failed to affect gut motility. Injection of the reversible acetylcholinesterase inhibitor and cholinergic agent, neostigmine, accelerated intestinal transit but failed to influence melatonin effect on this parameter. In contrast, intraperitoneal injection of the muscarinic receptor antagonist atropine delayed intestinal transit per se but did not reduce the stimulating effect of melatonin on this parameter. Intestinal myoelectrical recording revealed that intestinal myoelectrical activity was increased by intraperitoneal injection of melatonin (10 g/kg). Administration of luzindole totally prevented melatonin-induced increase of intestinal myoelectrical activity. These results indicate that melatonin may affect intestinal motility in rats when administered in small doses. This effect might be mediated by melatonin receptors in the intestines, although the involvement of central receptors for the hormone is also possible.  相似文献   
105.
BACKGROUND/AIMS: We studied the influence of biochemical and virologic patterns and interferon on the outcome of anti-HBe positive chronic hepatitis B in 164 (103 treated) consecutive patients, followed-up prospectively for a mean of 6 years (21 months-12 years). METHODS: Histology, biochemical and virologic profiles were characterized by monthly monitoring during the first 12 months of follow-up. Thereafter patients underwent blood and clinical controls every 4 and 6 months, respectively. Cirrhosis at follow-up histology or end stage complications of cirrhosis served as end points for the analysis of factors influencing disease progression in patients with baseline chronic hepatitis or cirrhosis, respectively. RESULTS: Disease progression was associated with older age (P<0.001), absence of previous HBeAg history (P=0.017) and higher serum HBV-DNA levels (P=0.009) (more frequently observed in unremitting disease profile, P=0.012) at multivariate analysis. Fluctuations of IgM anti-HBc levels (associated with disease exacerbations, P=0.045) correlated with end stage complications in cirrhotics (P=0.011). Disease improved in 14.6 and 1.6% of treated and untreated patients, respectively (P=0.015): interferon slowed disease progression (P<0.001). CONCLUSIONS: The outcome of anti-HBe positive chronic hepatitis B is worsened by older age and persistent viral replication or hepatitis exacerbations in chronic hepatitis or in cirrhotic patients, respectively. Interferon reduces by 2.5-folds disease progression.  相似文献   
106.
Objectives. We sought to compare myocardial contrast echocardiography with low dose dobutamine echocardiography for predicting 1-month recovery of ventricular function in acute myocardial infarction treated with primary coronary angioplasty.

Background. The relation between myocardial perfusion and contractile reserve in patients with acute myocardial infarction, in whom anterograde flow is fully restored without significant residual stenosis, is still unclear.

Methods. Thirty patients with acute myocardial infarction treated successfully with primary coronary angioplasty underwent intracoronary contrast echocardiography before and after angioplasty and dobutamine echocardiography 3 days after the index infarction. One month later, two-dimensional echocardiography and coronary angiography were repeated in all patients and contrast echocardiography in 18 patients.

Results. After coronary recanalization, 26 patients showed myocardial reperfusion within the risk area, although 4 did not. At 1-month follow-up, all patients had a patent infarct-related artery without significant restenosis. Both left ventricular ejection fraction and wall motion score index within the risk area significantly improved in the patients with reperfusion ([mean ± SD] 38 ± 8% vs. 48 ± 12%, p < 0.005; and 2.35 ± 0.5 vs. 2 ± 0.6, p < 0.001, respectively), but not in those with no reflow. Of the 72 nonperfused segments before angioplasty, 27 showed functional improvement at follow-up. Myocardial contrast echocardiography had a sensitivity and a negative predictive value similar to dobutamine echocardiography in predicting late functional recovery (96% vs. 89% and 89% vs. 93%, respectively), but a lower specificity (18% vs. 91%, p < 0.001), positive predictive value (41% vs. 86%, p < 0.001) and overall accuracy (47% vs. 90%, p < 0.001).

Conclusions. Microvascular integrity is a prerequisite for myocardial viability after acute myocardial infarction. However, contrast enhancement shortly after recanalization does not necessarily imply a late functional improvement. Thus, contractile reserve elicited by low dose dobutamine is a more accurate predictor of regional functional recovery after reperfused acute myocardial infarction than microvascular integrity.

(J Am Coll Cardiol 1996;28:1677–83)>  相似文献   

107.
PURPOSE This retrospective study evaluates the effect of abdominal hysterectomy on patients affected by descending perineum syndrome. METHODS Eighty-nine female patients affected by descending perineum syndrome and one group of 10 healthy women with normal bowel habits were studied retrospectively. Thirty-two descending perineum syndrome patients (Group 1) had received an abdominal hysterectomy for benign diseases, while 57 descending perineum syndrome patients (Group 2) had not undergone this surgery. All 99 subjects underwent clinical evaluation, computerized anorectal manometry, and defecography. RESULTS Dyschezia was found predominantly in Group 2 subjects (P < 0.05). Fecal incontinence was significantly higher in Group 1 than in Group 2 (P < 0.05). The worst anal resting pressure was found in the incontinent Group 1 patients (P < 0.01). Rectoanal intussusception was a significant defecographic sign in Group 1 subjects (P < 0.05). CONCLUSIONS Clinical evaluation and instrumental data suggested a possible link between fecal incontinence and abdominal hysterectomy in patients affected by descending perineum syndrome.  相似文献   
108.
To study the effects of sampling through cardiac catheters on indices of platelet function, we measured the levels of platelet factor 4 (PF4), beta thromboglobulin (BTG), and platelet aggregate ratio (PAR) in 10 patients with atrioventricular accessory pathway (AVNAP), six patients with primary pulmonary hypertension (PPH), and six patients with critical narrowing of the left anterior descending artery (LAD). In AVNAP and LAD patients samples were drawn simultaneously from a peripheral vein, coronary sinus, and brachial artery; in AVNAP patients samples were also obtained from the axillary vein before the coronary sinus was entered. In PPH patients samples were drawn from pulmonary artery, aorta, and a peripheral vein; in these patients the effects of an intravenous infusion of prostacyclin (PGl2) (2 to 8 ng/kg/min) on PF4, BTG, and PAR were also studied at all sampling sites. In all patients arterial, coronary sinus, pulmonary arterial, and axillary venous levels of PF4, BTG, and PAR significantly exceeded those measured in the peripheral vein. PGl2 infusion resulted in a significant decrease of PF4 at all sampling sites, while no consistent BTG changes were observed and PAR levels did not decrease in the peripheral vein. Although a considerable interpatient variability in PF4 levels was observed, a significant (r = 0.91) correlation was found in patients with AVNAP between simultaneous coronary sinus and arterial PF4 levels. The value of PF4 coronary sinus-arterial difference in LAD patients was consistently higher than that calculated in AVNAP patients (54.5 ± 28.9 vs 4.2 ± 3.8 ng/ml). In conclusion: (1) a considerable and variable degree of platelet activation occurs with catheter sampling, preventing the measurement of absolute levels of platelet metabolites; (2) among the indices examined PF4 appears the most sensitive for detecting changes in platelet activity; and (3) the measurement of coronary sinus-arterial PF4 differences may provide information on directional changes in transcardiac platelet behavior.  相似文献   
109.
Purpose  Some patients, having undergone sphincter-saving operations for rectal cancer, may suffer from fecal incontinence. This study was designed to evaluate the results of rehabilitative treatment in patients with fecal incontinence after sphincter-saving operations and to identify the negative factors that influence therapeutic success. Methods  Between January 2000 and June 2007, 88 incontinent patients (54 women; age range, 47–73 years; 69 had received a low anterior rectal resection; 19 a straight coloanal anastomosis) were included in the study. After a preliminary clinical evaluation, including the Wexner Incontinence Scale score, anorectal manometry was performed. All 88 patients underwent rehabilitative treatment according to the “multimodal rehabilitative program” for fecal incontinence. At the end of program, all 88 patients were reassessed by means of a clinical evaluation and anorectal manometry; their results were compared with the clinical and manometric data from ten healthy control subjects. Postrehabilitative Wexner Incontinence Scale scores were used for an arbitrary schedule of patients divided into three classes: Class I, good (score ≤3); Class II, fair (score >3 to ≤6); Class III, poor (score >6). Results  After rehabilitation, there was a significant improvement in the overall mean Wexner Incontinence Scale score (P < 0.03) for both surgical operation types (low anterior rectal resection: P < 0.05; coloanal anastomosis: P < 0.02). Only 21 patients (23.8 percent) were symptom-free, and 37 (42 percent) were considered Class III. A significant postrehabilitative direct correlation was found between: 1) Wexner Incontinence Scale score and degree of genital relaxation (rρ s 0.78; P < 0.001); 2) Wexner Incontinence Scale score and irradiation (rρ s 0.72; P < 0.01); and 3) Wexner Incontinence Scale score and pelvic (rρ s 0.65; P < 0.01) or anal surgery (rρ s 0.68; P < 0.01). No significant differences were found between prerehabilitative and postrehabilitative anal pressures in low anterior rectal resection and coloanal anastomosis patients. Conclusions  After rehabilitation, some patients become symptom-free, many patients show an improvement in the Wexner Incontinence Scale score, and others exhibit the highest grades of fecal incontinence. Genital relaxation, radiotherapy, and previous pelvic, and/or anal surgery are impeding factors to rehabilitative success.  相似文献   
110.
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