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   1075079篇
  免费   71569篇
  国内免费   1366篇
耳鼻咽喉   15015篇
儿科学   34609篇
妇产科学   28624篇
基础医学   153415篇
口腔科学   29571篇
临床医学   94922篇
内科学   203643篇
皮肤病学   24398篇
神经病学   81478篇
特种医学   42961篇
外国民族医学   201篇
外科学   163103篇
综合类   21703篇
现状与发展   1篇
一般理论   263篇
预防医学   74603篇
眼科学   24535篇
药学   86106篇
  7篇
中国医学   2805篇
肿瘤学   66051篇
  2019年   7762篇
  2018年   11295篇
  2017年   8907篇
  2016年   10095篇
  2015年   11260篇
  2014年   15269篇
  2013年   22205篇
  2012年   30543篇
  2011年   32288篇
  2010年   18949篇
  2009年   17814篇
  2008年   29948篇
  2007年   32067篇
  2006年   32701篇
  2005年   31033篇
  2004年   29723篇
  2003年   28552篇
  2002年   27529篇
  2001年   60021篇
  2000年   61477篇
  1999年   50928篇
  1998年   12445篇
  1997年   11002篇
  1996年   11016篇
  1995年   10320篇
  1994年   9345篇
  1993年   8858篇
  1992年   37794篇
  1991年   36278篇
  1990年   35752篇
  1989年   34294篇
  1988年   30867篇
  1987年   29993篇
  1986年   28220篇
  1985年   26453篇
  1984年   19197篇
  1983年   16117篇
  1982年   8828篇
  1979年   17033篇
  1978年   11406篇
  1977年   10230篇
  1976年   8837篇
  1975年   10071篇
  1974年   11653篇
  1973年   11274篇
  1972年   10754篇
  1971年   10092篇
  1970年   9252篇
  1969年   8938篇
  1968年   7917篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Brain cyclooxygenases (COX), the rate-limiting enzyme in prostaglandin synthesis, is rapidly and transiently induced by convulsions in hippocampal and cortical neurons. Previous studies have explored the protective effect of naproxen (non-selective COX-inhibitor) or rofecoxib (selective COX-2 inhibitor) against chemical kindling in mice. With this background, the present study was designed to explore the possible effect of nimesulide (a preferential COX-2 inhibitor) against pentylenetetrazol (PTZ)-induced kindling epilepsy in mice. To induce kindling, PTZ was injected in a subconvulsive dose (40 mg/kg, i.p.) every other day for 15 days. Nimesulide (2.5 or 5 mg/kg, p.o.) was administered each day 45 min before either PTZ or vehicle challenge. The intensity of kindling was assessed immediately after PTZ administration according to a prevalidated scoring scale. On 16th day i.e. 24 h after the last dose of PTZ, animals were sacrificed and various biochemical parameters were assessed in the whole brain. Compared with normal control group, PTZ-kindled mice had significantly higher levels of malondialdehyde, nitrite, myeloperoxidase but had lower levels of reduced glutathione in the whole brain homogenate. Chronic treatment with nimesulide (2.5 or 5 mg/kg, p.o.) for 15 days showed significant decrease in kindling score and could play a role in controlling the accompanying biochemical alterations due to PTZ. These results suggested that nimesulide, a preferential COX-2 inhibitor offered neuroprotection against PTZ-induced kindling in mice.  相似文献   
994.
OBJECTIVE: To estimate medium-term success after a technique for ultrasound-guided sclerotherapy for superficial chronic venous disease. DESIGN: A prospective study in a single unit with ultrasound surveillance after treatment. MATERIALS: Results after 1189 treatment sessions for 807 venous saphenous veins and related tributaries or non-saphenous tributaries in 489 patients. METHODS: Univariate life table analysis determined primary and secondary success rates. Multivariate Cox regression analysis detected covariates that affected outcome. RESULTS: Primary and secondary success rates at 36 months for all veins were 52.4% (95%CI 46-58%) and 76.8% (95%CI 71-82%). Cox regression analysis for primary success for all veins showed significantly worse results for saphenous veins compared to tributaries (HR 3.72 - 95%CI 1.9 to 7.3). Cox regression for all saphenous veins showed independently worse results for patients less than 40 years age (HR 2.16 - 95%CI 1.27-3.66), small compared to great saphenous veins (HR 1.58 - 95%CI 1.11-2.24), veins greater than 6mm diameter compared to smaller veins (HR 2.22 - 95%CI 1.40-3.50), liquid compared to foam sclerotherapy (HR 2.20 - 95%CI 1.28-3.78), lower volumes of sclerosant compared to volumes greater than 12 ml (HR 0.51 - 95%CI 0.33-0.81) and highly diluted compared to concentrated sclerosant (HR 2.05 - 95%CI 1.21-3.46) with worse results using highly diluted or undiluted 3% sclerosant compared to a 1.5% concentration. There were no significant differences for primary success for saphenous veins for date of procedure, sex, side, primary or recurrent varicose veins, or commercial type of sclerosant. CONCLUSIONS: Ultrasound-guided sclerotherapy gives satisfactory results if it is accepted that treatment may need to be repeated to achieve secondary success. Results provide a basis for further research to explore factors that might affect outcome. Younger patients with larger diameter saphenous veins may warrant alternative forms of treatment, particularly for small saphenous reflux.  相似文献   
995.
OBJECTIVE: A comprehensive study was performed to evaluate the accuracy of a newly developed CT-free, intra-operative planning and navigation system for anterior spine surgery. MATERIALS AND METHODS: Instruments and an image intensifier were tracked using the SurgiGATE navigation system. A laboratory study was performed on 27 plastic vertebrae. Fiducial markers were implanted in the vertebrae for accuracy evaluation purposes, and a dynamic reference base was placed on the vertebrae to establish a patient coordinate system (P-COS). Two fluoroscopic images were used for intra-operative planning. The graft bed plan was recorded in P-COS, followed by surgical formation of the graft bed, which was visualized. To evaluate the accuracy, the vertebrae were scanned with CT, and the markers were used to calculate an accurate paired-point registered transformation between the CT coordinate system and P-COS. RESULTS: Using the new SPO module, accurate planning and navigation of a resection of the vertebral body is possible using two fluoroscopic images. The overall mean error between the planned resection volume and the actual resection was 0.98 mm. In addition, the module can serve as an educational tool for training spine surgeons. CONCLUSIONS: The new fluoroscopy-based system can be used safely for accurate performance of anterior resection during spondylodesis. New methods for safe and accurate registration during anterior spine surgery need to be developed.  相似文献   
996.
Transabdominal sacrocolpopexy has been shown, in multiple long-term studies of its success and durability, to be the definitive treatment option for post-hysterectomy vaginal vault prolapse. It is, however, associated with greater morbidity than vaginal repair. We describe a minimally invasive technique for vaginal vault prolapse repair and present our experience with a minimum of one-year follow-up. The surgical technique involves five laparoscopic ports—three for the da Vinci robot and two for the assistant. After appropriate dissection a polypropylene mesh is attached to the sacral promontory and to the vaginal apex by use of Gore-Tex sutures. The mesh material is then covered by the peritoneum. Patient analysis focused on complications, urinary continence, patient satisfaction, and morbidity, with a minimum of 12 months follow-up. Forty-two patients with post-hysterectomy vaginal vault prolapse underwent robot-assisted laparoscopic sacrocolpopexy at our institute and 35 have a minimum of 12 months follow-up, with a mean follow-up of 36 months (range 12–48) in the group. Mean age was 67 (47–83) years and mean operating time was 3.1 (2.15–4.75) h for the entire cohort. All but one patient were discharged home on postoperative day one; one patient left on postoperative day two. One developed recurrent grade three rectocele, one had recurrent vault prolapse, and two suffered from vaginal extrusion of mesh. All patients were satisfied with their outcome. The robot-assisted laparoscopic sacrocolpopexy is a minimally invasive technique for vaginal vault prolapse repair, combining the advantages of open sacrocolpopexy with the reduced morbidity of laparoscopy. We observed reduced hospital stay, low occurrence of complications, and high patient satisfaction, with a minimum of 1-year follow-up. Most importantly, the long-term results of the robotic repair are similar to those of open repair, but with significantly less morbidity.  相似文献   
997.
Parenchymal disease in the allograft lung is associated with interstitial remodeling believed to be mediated by matrix metalloproteinases (MMPs). Recent studies suggest high levels of MMP-9 are associated with bronchiolitis obliterans syndrome (BOS) in lung transplant recipients. Since BOS occurs late in the posttransplant period and may be preceded by episodes of acute rejection or infection, which are associated with interstitial remodeling, we examined MMP profiles in allograft bronchoalveolar lavage (BAL) fluid in the early posttransplant period (preceding BOS). Gelatin zymography, protein array analysis and specific ELISA on BAL fluids from transplanted lungs indicated that MMP-8, MMP-9 and TIMP-1 were strongly expressed in allograft BAL fluid from stable patients, or those with infection or rejection compared to BAL fluid from normal volunteers. Elevated expression of MMP-8, MMP-9 and TIMP-1 occurred early, and was sustained for the 3.2 years covered in this study. Elevations of MMP-8, MMP-9 and TIMP-1 in the first 2 years posttransplant appear to be associated with lung transplantation itself, and not infection or rejection. These data suggest that ongoing and clinically silent MMP activity could perpetuate progressive disease in the allograft lung.  相似文献   
998.
Trauma und Berufskrankheit - Die Vermeidung gepuderter Latexhandschuhe gilt als wichtige Maßnahme zur Prävention von latexbedingten Haut- und Atemwegsallergien bei Beschäftigten im...  相似文献   
999.
This third part of this series of articles on laboratory diagnostics of rheumatic diseases considers the rheumatic diseases caused by infection by microorganisms, or reactive arthritides. The basis for laboratory diagnostics of infection-reactive arthritides is the investigation of anti-infection antibodies. In some situations, DNA amplification methods may be helpful. Bacterially infected joints should be immediately examined by arthrocentesis and microscopic examination and laboratory culture of the synovial fluid.  相似文献   
1000.
Pleural effusion is a common complication of various diseases. Conventional methods are not always capable of establishing the cause of pleural effusion, so alternative tests are needed. The aim of this study was to explore means of discriminating between different pleural effusion groups, malignant, parapneumonic and tuberculous, based on the combined function of seven biological markers. Adenosine deaminase (ADA), interferon-gamma, C-reactive protein (CRP), carcinoembryonic antigen, interleukin-6, tumour necrosis factor-alpha and vascular endothelial growth factor concentration levels were measured in pleural fluid from 45 patients with malignant, 15 with parapneumonic and 12 with tuberculous pleural effusion. Receiver operating characteristic curve analysis, multinomial logit modelling and canonical variate analysis were applied to discriminate the pleural effusion groups. The three groups could be discriminated successfully using the measured markers. The most important parameters for discrimination were ADA and CRP concentration levels. An individual with an ADA concentration level of >45 U.L(-1) and a CRP concentration of <4 mg.dL(-1) was more likely to belong to the tuberculous pleural effusion group, whereas one with an ADA concentration level of <40 U.L(-1) and a CRP concentration of >6 mg.dL(-1) was more likely to belong to the parapneumonic pleural effusion group, and one with a CRP concentration of <4 mg.dL(-1) to the malignant pleural effusion group. The combination of adenosine deaminase and C-reactive protein levels might be sufficient for discriminating between the three different groups of exudative pleural effusion: malignant, tuberculous and parapneumonic.  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