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   14038篇
  免费   661篇
  国内免费   119篇
耳鼻咽喉   96篇
儿科学   273篇
妇产科学   408篇
基础医学   1730篇
口腔科学   354篇
临床医学   971篇
内科学   4002篇
皮肤病学   217篇
神经病学   1307篇
特种医学   583篇
外科学   2115篇
综合类   34篇
一般理论   1篇
预防医学   501篇
眼科学   156篇
药学   695篇
中国医学   23篇
肿瘤学   1352篇
  2024年   12篇
  2023年   89篇
  2022年   200篇
  2021年   410篇
  2020年   207篇
  2019年   300篇
  2018年   391篇
  2017年   291篇
  2016年   325篇
  2015年   362篇
  2014年   553篇
  2013年   705篇
  2012年   971篇
  2011年   995篇
  2010年   641篇
  2009年   581篇
  2008年   1003篇
  2007年   1003篇
  2006年   911篇
  2005年   958篇
  2004年   850篇
  2003年   781篇
  2002年   698篇
  2001年   81篇
  2000年   71篇
  1999年   102篇
  1998年   148篇
  1997年   108篇
  1996年   130篇
  1995年   85篇
  1994年   98篇
  1993年   81篇
  1992年   69篇
  1991年   59篇
  1990年   59篇
  1989年   45篇
  1988年   33篇
  1987年   23篇
  1986年   35篇
  1985年   34篇
  1984年   30篇
  1983年   24篇
  1982年   32篇
  1981年   33篇
  1980年   31篇
  1979年   20篇
  1976年   10篇
  1974年   8篇
  1972年   8篇
  1964年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
introduction: Cancer of the testis is not always early detected and recognised, both by the physician and by the patient: sometimes physicians do not make an accurate genitals exam while patients often underestimate this problem. Case reports: Case I: 42-year-old man accepted from another hospital's Emergency, because of pain and edema of the right testis after a recent trauma on the gonad. At US, evidence of increased volume of the right testis with a large intraparenchymal hematoma. The markers were higher than normal. We performed a right orchiecthomy. The pathologist noted the presence of a mixed cancer of the testis (95% embryonal, 5% seminoma). Case II: 49-year-old man with hematuria, accepted from Emergency. The abdominal US revealed the presence of a voluminous neoformation (diameter of 12 cm) of the right kidney with neoplastic thrombosis of the right kidney vein. At the general physical exam, we detected the presence of an increased right testis, that at the US appared to be suspicious for cancer. Tumor markers were normal with the exception of αFP. We performed right nephro-adrenalectomy, right orchiectomy and removal of local nodes. The definitive histological examination demonstrated the presence of a seminoma of the testis and papillary carcinoma of the kidney with node metastasis. Discussion: Current studies showed an association between trauma and cancer of the testis, even if some authors did not find this association because they consider that patients with trauma undergo US and in that occasion cancer is incidentally detected. Conclusions: The association between trauma and cancer of the testis is controversial in current studies. Furthermore screening for the cancer of the testis does not seem to be useful, even if the self- and the physician's palpation of the testis seem to be very important because in these two cases they should allow the early detection of the condition, with a resulting better prognosis.  相似文献   
72.
PURPOSE: To demonstrate that unsupervised assessment of abdominal adipose tissue distribution by magnetic resonance imaging (MRI) can be improved by integrating automatic correction of signal inhomogeneities. MATERIALS AND METHODS: Twenty subjects (body mass index [BMI] 23.7-44.0 kg/m(2)) underwent abdominal (32 slices) MR imaging with a 1.9T Elscint Prestige scanner. Many images were affected by relevant intensity distortions. Unsupervised segmentation of subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) was performed by a previously validated algorithm exploiting standard fuzzy clustering segmentation. Images were also processed by an improved version of the software, including automatic correction of intensity inhomogeneities. To assess the effectiveness of the two methods SAT and VAT volumes were compared with manual analysis performed by a trained operator. RESULTS: Coefficient of variation between manual and unsupervised analysis was significantly improved by inhomogeneities correction in SAT evaluation. Systematic underestimation of SAT was also corrected. A less important performance improvement was found in VAT measurement. CONCLUSION: The results of this study suggest that the compensation of signal inhomogeneities greatly improves the effectiveness of the unsupervised assessment of abdominal fat. Correction of intensity distortions is important in SAT evaluation and less significant in VAT measurement.  相似文献   
73.
OBJECTIVE: We reviewed our experience in the surgical management of 80 patients with colorectal pulmonary metastases and investigated factors affecting survival. MATERIAL AND METHODS: From January 1980 to December 2000, 80 patients, 43 women and 37 men with median age 63 years (range 38-79 years) underwent 98 open surgical procedure (96 muscle-sparing thoracotomy, one clamshell and one median sternotomy) for pulmonary metastases from colorectal cancer (three pneumonectomy, 17 lobectomy, seven lobectomy plus wedge resection, six segmentectomy, three segmentectomy plus wedge resection and 62 wedge resection). Pulmonary metastases were identified at a median interval of 37.5 months (range 0-167) from primary colorectal resection. Second and third resections for recurrent metastases were done in seven and in four patients, respectively. RESULTS: Operative mortality rate was 2%. Overall, 5-year survival was 41.1%. Five-year survival was 43.6% for patients submitted to single metastasectomy and 34% for those submitted to multiple ones. Five-year survival was 55% for patients with disease-free interval (DFI) of 36 months or more, 38% for those with DFI of 0-11 months and 22.6% for those with DFI of 12-35 months (P=0.04). Five-year survival was 58.2% for patients with normal preoperative carcino-embryonic antigen (CEA) levels and 0% for those with pathologic ones (P=0.0001). Patients submitted to second-stage operation for recurrent local disease had 5-year survival rate of 50 vs. 41.1% of those submitted to single resection (P=0.326). CONCLUSIONS: Pulmonary resection for metastases from colorectal cancer may help survival in selected patients. Single metastasis, DFI>36 months, normal preoperative CEA levels are important prognostic factors. When feasible, re-operation is a safe procedure with satisfactory long-term results.  相似文献   
74.
Giant prolactinomas presenting as skull base tumors   总被引:2,自引:0,他引:2  
BACKGROUND: Prolactinomas invading the skull base are rare, and could easily be confused with skull base tumors of nonpituitary origin. CASE DESCRIPTION: We report a series of 4 cases of giant prolactinomas invading the skull base and presenting with atypical symptoms. Case 1 presented with a short history of headache and nasal obstruction. Case 2 presented with progressive hypoacusia, dizziness, and ophthalmoplegia. In Case 3, the patient developed rapid progressive visual failure and psychiatric symptoms. Case 4 presented with a 1-year history of headache and retrorbital pain. The diagnosis of prolactinoma was made on the basis of tumor immunohistochemistry and/or high plasma prolactin levels (range from 650-6,500 ng/mL). Medical treatment with the dopamine agonist cabergoline was given; it was effective in normalizing prolactin levels and inducing tumor shrinkage. CONCLUSION: Prolactin levels should be measured in all large skull base tumors involving the pituitary region before any surgery or inappropriate radiotherapy is performed.  相似文献   
75.
Lymphocyte costimulatory receptors in renal disease and transplantation   总被引:12,自引:0,他引:12  
Cell-to-cell signal exchange during antigen presentation deeply influences the profile and extent of the immune response. Together with the TCR/MHC-mediated signal, accessory signals are provided to the T cell by the antigen-presenting cell (APC), through specific receptor-ligand interactions that represent indispensable costimulation for T-cell activation and survival. The main costimulatory pathways are the B7 family members and the CD40-CD154 receptor-ligand pair. B7-1 and B7-2 costimulate T-cells by binding to CD28. Their binding is prevented by the neoexpression of CTLA4, a CD28 homologue that can deliver a negative signal. Another CD28-like molecule, called ICOS (inducible costimulator), has been described and binds B7RP-1, a third member of the B7 family, but not B7-1 and B7-2. The CD40-CD154 interaction works as a two way costimulatory system by triggering activation signals to both T-cell and APCs. Its importance is highlighted by the discovery that mutations of the CD154 gene are responsible for a severe human immunodeficiency. Disruption of the natural costimulatory interaction was highly effective for prevention and treatment in several experimental models of autoimmune disease and transplant rejection. This review focuses on the most significant advances in understanding the physiopathological events involving costimulatory molecules, and their impact on renal diseases and transplantation.  相似文献   
76.
PURPOSE: We characterize the consequences of androgen deprivation therapy on body composition in elderly men. MATERIALS AND METHODS: Using a dual energy x-ray absorptiometry instrument, we determined the changes in bone mineral density, bone mineral content, fat body mass and lean body mass in 35 patients with prostate cancer without bone metastases who received luteinizing hormone releasing hormone analogue for 12 months. RESULTS: At baseline conditions 46% of cases were classified as osteopenic and 14% as osteoporotic at the lumbar spine and 40% were osteopenic and 4% osteoporotic at the hip. Androgen deprivation significantly decreased bone mineral density either at the lumbar spine (mean gm./cm.2 [SD] 1.00 [0.194], 0.986 [0.172] and 0.977 [0.182] at baseline, and 6 and 12 months, respectively, p <0.002) or the hip (0.929 [0.136], 0.926 [0.144] and 0.923 [0.138], p <0.03). A more than 2% decrease in bone mineral density was found at the lumbar spine in 19 men (54.3%) and at the hip in 15 (42.9%). Bone mineral content paralleled the bone mineral density pattern. Lean body mass decreased (mean gm. [SD] 50,287 [6,656], 49,296 [6,554] and 49,327 [6,345], p <0.003), whereas fat body mass consistently increased (18,115 [6,209], 20,724 [6,029] and 21,604 [5,923] p <0.001). CONCLUSIONS: Serial bone densitometry evaluation during androgen deprivation therapy may allow the detection of patients with prostate cancer at risk for osteoporotic fractures, that is those with osteopenia or osteoporosis at baseline and fast bone loss. The change in body composition may predispose patients to accidental falls, thus increasing the risk of bone fracture.  相似文献   
77.
Hypertrophic anterior cervical osteophytes have been reported as a cause of dysphagia, with about 100 cases described in the literature; on the other hand, chronic or acute dyspnea due to edema of the laryngeal inlet or bilateral vocal cord adduction-fixation is rare. We report a 57-year-old patient with a 2-year history of dysphagia and episodic dyspnea, who suffered sudden, severe respiratory distress necessitating emergency tracheotomy. A voluminous anterior cervical osteophyte at the C5 level was diagnosed by computed tomography (CT) and barium swallow test and removed by an anterior approach to the cervical spine, with clinical remission. The incidence, pathogenetic mechanisms, radiological diagnosis, and surgical indications of anterior cervical osteophytes associated with dysphagia and dyspnea are discussed. We advise examining cervical spine patients with dysphagia and/or dyspnea by radiography and CT when other investigations are not conclusive for a digestive or respiratory pathology.  相似文献   
78.
Background Benign esophageal pseudoachalasia is a rare condition. Discussion We report the case of a 70-year-old man who complained of severe dysphagia after laparoscopic Nissen fundoplication and crural mesh repair performed for long-standing gastroesophageal reflux disease. Severe dysphagia and nocturnal aspiration developed soon after the operation. A marked dilatation of the esophageal body and a manometric pattern resembling achalasia was documented. Results Endoscopic balloon dilatation was ineffective. Five months after the initial operation, the patient underwent revisional laparoscopic surgery that consisted of Nissen’s wrap takedown, enlargement of the hiatus with partial resection of the mesh, Heller myotomy, and Dor fundoplication. After a 2-year follow-up, the patient is doing well and is free of symptoms.  相似文献   
79.

Background

To our knowledge, the impact of venous tumour thrombus (VTT) consistency in patients affected by renal cell carcinoma (RCC) has never been addressed.

Objective

To analyse the effect of VTT consistency on cancer-specific survival (CSS).

Design, setting, and participants

We retrospectively analysed 174 consecutive patients with RCC and renal vein or inferior vena cava (IVC) VTT who underwent surgical treatment between 1989 and 2007 at our institute.

Intervention

All patients underwent radical nephrectomy and thrombectomy.

Measurements

Pathologic specimens were reviewed by a single uropathologist. In addition to traditional pathologic features, the morphologic aspect of the tumour thrombus was evaluated to distinguish solid from friable patterns. The prognostic role of thrombus consistency (solid vs friable) on CSS was assessed by means of Cox regression models.

Results and limitations

The VTT was solid in 107 patients (61.5%) and friable in 67 patients (38.5%). The presence of a friable VTT increased the risk of having synchronous nodal or distant metastases, higher tumour grade, higher pathologic stage, and simultaneous perinephric fat invasion (all p < 0.05). The median follow-up was 24 mo. The median CSS was 33 mo; the median CSS was 8 mo in patients with a friable VTT and 55 mo in patients with a solid VTT (p < 0.001). On multivariable analyses, the presence of a friable VTT was an independent predictor of CSS (p = 0.02). The power of our conclusion may be somewhat limited by the relatively small study population and the retrospective nature of the study.

Conclusions

In patients with RCC and VTT, the presence of a friable thrombus is an independent predictor of CSS. If our finding is confirmed by further studies, the consistency of the tumour thrombus should be introduced into routine pathologic reports to provide better patient risk stratification.  相似文献   
80.
Little is known about bone mineral density (BMD) in patients with heroin addiction and subsequent methadone substitution. The goal of this study was to compare bone mass density of young HIV-negative women on long-term methadone treatment to a local group of young healthy women. Eleven women (aged 20–29) with previous heroin dependence and current methadone substitution (20–140 mg, median 60, daily) for 1.5–9 (median 3) years were compared to 30 healthy women (aged 20–28). Participants were examined with dual-energy X-ray absorptiometry of the lumbar spine (L2–L4), of the total proximal hip area, and of the femoral neck. Patients and controls had neither current nor lifetime underweight condition, had comparable ages at menarche, and did not differ significantly in current body mass index (21.9 ± 4.0, respectively, 20.5 ± 1.5 kg/m2) in spite of a largely unhealthy lifestyle (cigarette, alcohol, and cocaine consumption in patients). Patients’ total-hip parameters were marginally lower than those of controls (BMD P = 0.054, T score P = 0.049), whereas the femoral neck and lumbar spine parameters did not differ significantly between the two groups. Long-term methadone substitution in HIV-negative women seems to slightly affect bone mass density.  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