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   4788篇
  免费   395篇
  国内免费   12篇
耳鼻咽喉   115篇
儿科学   189篇
妇产科学   67篇
基础医学   647篇
口腔科学   75篇
临床医学   456篇
内科学   941篇
皮肤病学   57篇
神经病学   489篇
特种医学   162篇
外科学   628篇
综合类   74篇
一般理论   3篇
预防医学   492篇
眼科学   133篇
药学   309篇
中国医学   4篇
肿瘤学   354篇
  2023年   32篇
  2021年   62篇
  2020年   44篇
  2019年   59篇
  2018年   76篇
  2017年   40篇
  2016年   69篇
  2015年   77篇
  2014年   116篇
  2013年   208篇
  2012年   213篇
  2011年   226篇
  2010年   107篇
  2009年   109篇
  2008年   181篇
  2007年   223篇
  2006年   218篇
  2005年   204篇
  2004年   207篇
  2003年   197篇
  2002年   217篇
  2001年   104篇
  2000年   125篇
  1999年   97篇
  1998年   61篇
  1997年   55篇
  1996年   53篇
  1995年   44篇
  1994年   37篇
  1993年   44篇
  1992年   83篇
  1991年   122篇
  1990年   93篇
  1989年   97篇
  1988年   92篇
  1987年   75篇
  1986年   88篇
  1985年   87篇
  1984年   70篇
  1983年   44篇
  1982年   48篇
  1981年   42篇
  1980年   42篇
  1979年   55篇
  1978年   47篇
  1977年   49篇
  1976年   42篇
  1975年   51篇
  1974年   38篇
  1971年   34篇
排序方式: 共有5195条查询结果,搜索用时 15 毫秒
51.
Objectives Tonsils are uncommonly affected by granulomatous inflammation, often with an obscure cause. This study attempts to elucidate the nature of tonsillar granulomatous inflammation. Design Retrospective clinicopathologic review. Methods Twenty‐two cases of tonsillar granulomas diagnosed between 1940 and 1999 were retrieved from the files of the Armed Forces Institute of Pathology. H&E slides and a series of histochemical stains were reviewed, and patient follow‐up was obtained. Results There were 11 males and 11 females, aged 7 to 64 years (mean, 29.9 y). Most of the cases presented bilaterally (n = 19) with sore throat, dysphagia, and/or nasal obstruction. The clinical differential included chronic tonsillitis, tuberculosis, nonspecific infection, sarcoidosis, and a neoplasm. Histologically, the granulomas were focal and scattered, or diffuse, identified in the interfollicular zones (n = 16) and/or the germinal centers (n = 13), and occasionally associated with necrosis (n = 6). Based on histochemical and clinical follow‐up information, the etiology of the granulomas included sarcoidosis (n = 8), tuberculosis (n = 3), Hodgkin's lymphoma (n = 2), toxoplasmosis (n = 1), squamous cell carcinoma (n = 1), and no specific known cause (n = 7). Twelve patients were either alive at last follow‐up or had died with no evidence of disease (mean, 12.4 y), and 9 were either alive at last follow‐up or had died with disease (mean, 24.9 y). One patient was alive with unknown disease status (lost to follow‐up after 13.3 y). Conclusions Although a cause for tonsillar granulomas is frequently identified, a number may not develop an identifiable etiology, with the granulomas probably representing an exaggerated immune response to chronic tonsillitis. However, a careful work‐up must be conducted to exclude specific causes and avoid clinical mismanagement.  相似文献   
52.
Many different activities have been defined for the effective use of clinical audit. Proposes a method of linking the practice and outcome of audit with the Trust business people, setting out criteria methodology and background following a two-year research study.  相似文献   
53.
SummaryPurpose This study was undertaken to evaluate the radiographie response to two cycles of chemotherapy prior to irradiation in newly diagnosed children with high-grade astrocytomas.Patients and methods. One hundred and thirty children less than 21 years of age with newly-diagnosed highgrade astrocytoma were treated with the eight-drugs-in-one-day chemotherapy regimen as part of a phase III multi-institutional Childrens Cancer Group (CCG) trial. Computerized Tomographic (CT) or Magnetic Resonance Image (MRI) scans, obtained after two cycles of chemotherapy had been administered, were compared with post-operative scans to determine treatment response. Scans were evaluated by institutional radiologists, and were reviewed centrally by a single neuroradiologist.Results Of 79 patients with evaluable post-operative residual tumor on CT or MRI scans, 26 (33%) were determined on institutional evaluation to have had an objective response. However, central review of scans documented responses on only 14/79 (18%). A significantly higher response rate on central review was observed for those children 36 months of age or less at study entry than for older children (33% v 11%; p < 0.001). However, a higher disease progression rate was also observed for those children 36 months of age or less than for older children (21% v 2.6%; p < 0.001).Conclusion In this study, the largest yet reported in newly-diagnosed children with high-grade astrocytomas, the chemotherapy regimen has activity in younger children. The differences in response rates reported by institutional and central review highlight the difficulties inherent in assessing response to brain tumor therapy. However, the study does demonstrate the consistent ability of radiologists to identify disease progression within the institutional and central reviews.  相似文献   
54.
Objective. To assess the utility of MR in detecting surgically induced Stener lesions (displaced thumb ulnar collateral ligaments) in cadaveric models. Design. Six cadaver thumbs had ulnar collateral ligament (UCL) tears created surgically. MR examinations (2D STIR and 3D GRASS) were performed identically on all specimens both before displacement (non-Stener) and after displacement (Stener lesion) of the UCL. The MR images were then randomly numbered. Each image was evaluated separately in blinded fashion by four musculoskeletal radiologists for the presence or absence of a Stener lesion. Each radiologist reinterpreted the images after an interval of several days. The interpretation was based on previously published criteria for Stener lesion diagnosis by MR. Results. The sensitivity of GRASS ranged from 0.17 to 0.67 with the most experienced reader scoring the lowest. The specificity of GRASS ranged from 0.33 to 1.0 (most experienced reader 0.67, 0.83). STIR had a sensitivity of 0.00–0.17 and a specificity of 0.53–0.83. The values for inter- and intraobserver agreement were measured. The intraobserver for GRASS was 0.27–0.75 (most experienced reader 0.75). Conclusions. 2D imaging is probably inadequate for the evaluation of Stener lesions. The most likely reason is that the STIR slice thickness of 3 mm limits resolution of small UCLs. The poor sensitivity and specificity of GRASS as well as poor interobserver agreement suggest that MR may not be sufficiently accurate for Stener lesion evaluation.  相似文献   
55.
Medulloblastoma     
The utilization of multi-modal therapy in the treatment of medulloblastoma has improved survival rates and overall outcome. Recent large clinical trials have supported the use of radiation and chemotherapy as adjuvant treatment. Treatment advances have been made despite a poor understanding of the biological underpinnings of medulloblastoma. Current laboratory investigations are shedding light on the oncogenesis of medulloblastoma and may lead to improved treatments.  相似文献   
56.
PURPOSE: To describe the imaging and histologic features of large-core needle biopsy (LCNB) specimens of fibrous nodules. MATERIALS AND METHODS: Of 853 breast masses in which LCNB was performed, 38 (4%) revealed histologic findings of fibrous nodules. Repeat biopsy was performed in 16 lesions (surgical excision, 13 lesions; repeat LCNB, three lesions). The mammographic and ultrasonographic findings in these 16 cases, the histologic LCNB findings, and the repeat biopsy findings were retrospectively reviewed. RESULTS: Repeat biopsy findings confirmed the diagnosis of fibrous nodules in 15 of the 16 masses. In one mass, repeat LCNB findings showed a fibroadenoma. The imaging features of the fibrous nodules varied. Five nodules (33%) manifested as masses with indistinct margins; six (40%), as circumscribed masses. In four cases (27%), imaging suggested malignancy. None were calcified masses. An additional 22 masses had circumscribed or indistinct borders and were diagnosed with LCNB as fibrous nodules. None of these masses had suspicious findings, and repeat biopsy was not performed. CONCLUSION: Fibrous nodules usually manifest as masses with circumscribed or indistinct margins but can have findings suggestive of malignancy. LCNB can reveal histologic findings consistent with this diagnosis. In all masses in which repeat biopsy was performed, the diagnosis of a fibrous nodule was confirmed or another benign stromal lesion was diagnosed.  相似文献   
57.
58.

Purpose

To study the haemodynamic effects of intrathecal meperidine, administered either alone or mixed with bupivacaïne.

Methods

We studied 42 Chinese patients, aged 59–87 yr, scheduled for transurethral bladder or prostate surgery, randomized into three equals groups, that received either meperidine 0.8 mg · kg?1 meperidine 0.4 mg · kg?1 plus 1.5 ml of 0.5% heavy bupivacaïne or 3 ml of heavy bupivacaïne 0.5%. Non-invasive systolic (SAP) and mean (MAP) arterial pressures, central venous pressure and cardiac index, stroke index and heart rate (HR) measured by the BoMed NCCOM3-R7S bioimpedance device, were recorded over the first 25 min. Systemic vascular resistance index (SVRI) was derived. Onset of sensory and motor block was also measured. Decreases in MAP of 25% were treated with colloid and metaraminol. Results: The onset of block was slower in the meperidine group (P < 0.05). Decreases in SAP, MAP and SVRI (all; P < 0.001) occurred within five minutes in all three groups. The HR was increased in the bupivacaïne group (P = 0.03), but bradycardias treated with atropine occurred in six patients receiving meperidine and four patients receiving the mixture. Six patients receiving meperidine and two patients receiving the mixture required general anaesthesia for inadequate block. The incidence of nausea and vomiting was higher in the patients receiving meperidine (P < 0.05). No other complications were encountered.

Conclusions

Intrathecal meperidine used alone or mixed with bupivacaïne has no intra-operative advantage over heavy bupivacaïne 0.5%.  相似文献   
59.
Acquired intracardiac shunt after prosthetic valve replacement is a rare complication, and reoperation for correction of this disorder carries a high mortality rate. We report such a case of left ventricular-right atrial fistula after mitral valve replacement in which the patient died of multiple complications. Awareness, prevention, and early diagnosis are, therefore, extremely important.  相似文献   
60.
Computer tomography (CT) was used in 53 consecutive patients with a working diagnosis of cerebellopontine angle tumor. The CT was performed with the 160 X 160 matrix scanner, height of sections was 13 mm. Metrizoate sodium (1.5 ml/kg of body weight) was used for tumor enhancement. Seventeen CT scans revealed tumors; one patient proved at operation to be false-positive. Thirty-six CT scans revealed no tumors; two examinations may prove to be false-negative, but surgical verification has so far not been obtained. The smallest tumor demonstrated by CT extended 7 mm into the angle, while one of the possible false-negative CT scans after iophendylate injection cisternography showed a tumor extending 5 mm into the angle. It is concluded that CT is a harmless, noninvasive neuroradiological procedure, and should precede invasive procedures. It can be used safely in patients with increased intracranial pressure.  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