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   21608篇
  免费   1109篇
  国内免费   157篇
耳鼻咽喉   222篇
儿科学   470篇
妇产科学   209篇
基础医学   2455篇
口腔科学   425篇
临床医学   1502篇
内科学   6044篇
皮肤病学   463篇
神经病学   1637篇
特种医学   806篇
外科学   3943篇
综合类   53篇
预防医学   539篇
眼科学   405篇
药学   1195篇
中国医学   51篇
肿瘤学   2455篇
  2024年   31篇
  2023年   205篇
  2022年   404篇
  2021年   706篇
  2020年   388篇
  2019年   476篇
  2018年   630篇
  2017年   428篇
  2016年   591篇
  2015年   558篇
  2014年   781篇
  2013年   894篇
  2012年   1414篇
  2011年   1660篇
  2010年   917篇
  2009年   809篇
  2008年   1355篇
  2007年   1398篇
  2006年   1366篇
  2005年   1408篇
  2004年   1452篇
  2003年   1296篇
  2002年   1201篇
  2001年   210篇
  2000年   194篇
  1999年   223篇
  1998年   243篇
  1997年   239篇
  1996年   163篇
  1995年   142篇
  1994年   153篇
  1993年   117篇
  1992年   118篇
  1991年   94篇
  1990年   87篇
  1989年   79篇
  1988年   57篇
  1987年   58篇
  1986年   40篇
  1985年   31篇
  1984年   37篇
  1983年   26篇
  1982年   28篇
  1981年   17篇
  1980年   18篇
  1979年   20篇
  1978年   16篇
  1977年   15篇
  1976年   12篇
  1975年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Background: Previous studies indicate that gastric carcinomas express Fas ligand and downregulate Fas to escape from the host immune attack; however, the prognostic importance of Fas/FasL expression in this tumor is yet to be evaluated.Methods: Specimens from 87 gastric carcinoma patients of different stages treated in a defined period with curative intent were evaluated for apoptosis, Fas, FasL, and CD8 expression using an immunohistochemical method.Results: The percentage of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL)-positive apoptotic cells expressed as apoptotic index (AI) was higher in 43 patients when the cut-off value was set at the median value. There were no significant correlations between AI and clinicopathologic parameters. Thirty-nine patients showed a high number of CD81 cells within cancer nests. Positive FasL and Fas expression was seen in 53 and 72 patients, respectively. CD8 and FasL expressions were related only to patients age. Fas expression had significant correlations with tumor invasion and Lauren classification. There were significant direct correlations between AI and number of nest CD81 cells and between AI and grade of Fas expression. Apoptotic index, pT stage, CD8 expression, and Fas expression were identified as independent prognostic factors.Conclusions: Spontaneous apoptosis in gastric carcinoma may be an independent prognosticator for survival and is significantly influenced by tumor Fas expression and number of nest CD81 cells.  相似文献   
992.
We previously reported that a toll‐like receptor 4 signaling contributes to the development of osteonecrosis of the femoral head. Also, oxidative stress is suggested to be one of the possible pathogenesis of osteonecrosis of the femoral head. A recent study showed that toll‐like receptor 4 signaling leads to oxidative stress. The aim of the present study was to evaluate whether toll‐like receptor 4 stimulation and subsequent corticosteroid treatment lead to the development of osteonecrosis of the femoral head in rat, and oxidative stress is associated with it. Male Wistar rats were randomly divided into four treatment groups: Saline + Saline, Saline + Methylprednisolone, Lipopolysaccharide + Saline, Lipopolysaccharide + Methylprednisolone. Osteonecrosis of the femoral head at 14 days after the treatment was observed in 1 of 10 Lipopolysaccharide + Saline, and 5 of 10 Lipopolysaccharide + Methylprednisolone treated rats. However, it was not observed at all in the Saline + Saline and Saline + Methylprednisolone treated groups. Glutathione peroxidase activity in the liver at 1 day after the treatment was significantly increased when treated with lipopolysaccharide. However, methylprednisolone treatment reduced the activity. On the other hand, glutathione peroxidase activity in the femur did not change in any intergroup. In conclusion, the present study showed that toll‐like receptor 4 stimulation by lipopolysaccharide administration strengthen incidence of corticosteroid‐induced osteonecrosis of the femoral head, however, concomitant oxidative stress via toll‐like receptor 4 signaling may not contribute to the development of osteonecrosis of the femoral head in rats. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:342–345, 2016.  相似文献   
993.
BACKGROUND: Otsuka Long-Evans Tokushima Fatty (OLETF) rats genetically develop diabetes which is associated with hypertension. In preliminary studies, urinary excretions of L-PGDS (lipocaline-type prostaglandin D synthase) increase before diabetic nephropathy obviously develops, and this may predict progression of renal injury following diabetes. In the present study, we attempted to define whether urinary excretions of L-PGDS behave as the predictor of development of diabetic nephropathy in OLETF rats. METHODS: We investigated alterations of urinary L-PGDS excretions during the establishment of diabetes and assessed the relationship between the L-PGDS excretions and renal function in OLETF rats. Furthermore, we treated OLETF rats with troglitazone and analysed the effects on L-PGDS metabolisms. Urinary L-PGDS was measured by immunoenzyme assay and the occurrence of L-PGDS and its mRNA in the kidney was assessed by immunohistochemistry and a PCR method. RESULTS: Urinary excretions of L-PGDS were significantly higher in OLETF rats than non-diabetic Long-Evans Tokushima Otsuka (LETO) rats. The excretions age-dependently increased in OLETF and this increase appeared to be due to increased glomerular permeability to L-PGDS. Messenger RNA and antigenicity of L-PGDS were demonstrated in renal tissue; however, the de novo synthesis of L-PGDS mRNA seemingly contributed to urinary L-PGDS excretions much less than glomerular filtration. Multiple regression analysis revealed that urinary L-PGDS was determined by urinary protein excretions, and not by high blood pressure per se. Conversely, urinary proteinuria in the established diabetic nephropathy was predicted by urinary L-PGDS excretions in the early stage of diabetes. CONCLUSIONS: Urinary excretions of L-PGDS are likely to reflect the underlying increase in glomerular permeability. This property may be useful to predict forthcoming glomerular damage following diabetes in OLETF rats.  相似文献   
994.
An endovascular stent graft was successfully deployed to the primary entry site in the proximal descending thoracic aorta after total aortic arch replacement using the "elephant trunk" technique in acute type A aortic dissection. The residual false lumen of the descending aorta was thrombosed completely after stent grafting. The elephant trunk was feasible for a proximal landing zone for stent grafting of the descending aorta. Stent grafting in combination with aortic arch replacement was a safe and effective procedure, and may be an alternative choice in carefully selected patients with type A aortic dissection.  相似文献   
995.
We report an adult case who presented vertigo attacks due to subclavian steal syndrome associated with the right aortic arch in a patient with Peutz-Jeghers syndrome. A 29-year-old male diagnosed as having Peutz-Jeghers syndrome developed frequent vertigo attacks and was admitted to our hospital. Blood pressure of the left arm was 20 mmHg lower than that of the right arm. Aortagraphy showed that he had a right aortic arch and isolation of the left subclavian artery. Right vertebral angiography opacified the left vertebral artery and the subclavian artery in retrograde fashion, suggesting subclavian steal phenomenon. Blood flow studies disclosed impaired reactivity to acetazolamide in the bilateral cerebellar hemispheres. We successfully carried out left common carotid artery-transverse cervical artery bypass. Postoperative angiography confirmed the patency of the graft and the disappearance of subclavian steal phenomenon. Vasoreactivity to acetazolamide normalized in the cerebellum. Vertigo attacks were not noted during the one-year follow-up period.  相似文献   
996.
997.
Chronic idiopathic colonic pseudo-obstruction (CICP) is characterized by the chronic disturbance of colonic motility without mechanical obstruction, any underlying disease or medication. Currently, there are no established medical treatments for CICP. A 62-year-old female who had undergone right hemicolectomy for splenic flexure syndrome caused by idiopathic megacolon was referred to our hospital with relapse, experiencing palpitation and abdominal fullness. She was diagnosed with CICP according to findings of marked dilation of the colon without mechanical obstruction, dilation of other parts of the gastrointestinal tract, or underlying disease. The dilated colon was surgically removed by hand-assisted laparoscopic subtotal colectomy, followed by cecorectal anastomosis. Histopathologically, there was no degeneration or lack of ganglion cells in Auerbach’s plexus. The patient has experienced no severe symptoms after undergoing the present operation.  相似文献   
998.
999.
Lymph node metastasis in T1 adenocarcinoma of the colon and rectum   总被引:11,自引:0,他引:11  
The biology of colorectal cancer differs according to location within the large intestine. To evaluate the clinical significance of tumor location as a risk factor for lymph node metastasis (LNM), we performed a detailed pathological review of T1 adenocarcinomas of the colon and rectum. T1 adenocarcinomas of the colon and rectum treated by radical resection (n = 428) were identified from prospective clinical databases at two institutions. Tumor location was assigned as right colon (cecum to transverse), left colon (splenic flexure to sigmoid), or rectum (0–18 cm from AV). Pathology slides were reviewed, extent of submucosal invasion (sm width, sm depth) was quantified using an optical micrometer, and morphologic features of the cancer and its infiltrating margin were recorded. The overall rate of LNM was 10%. On univariate analysis, LNM was significantly more common in the rectum (27/176, 15%) compared to the left colon (13/160, 8%, p = .04) or right colon (3/92, 3%, p = .003). However, on multivariate analysis, deep submucosal invasion and lymphovascular invasion were independent and significant risk factors, whereas tumor location was not. T1 colorectal cancers have a progressively higher risk of LNM as their location becomes more distal. However, the increasing rate of LNM observed in cancers of the left colon and rectum is explained by a higher prevalence of high-risk pathologic features. In early colorectal cancers, tumor morphology is the strongest clinical predictor of metastatic behavior. Presented at the Forty-Fifth Annual Meeting of The Society for Surgery of the Alimentary Tract, New Orleans, Louisiana, May 15–19, 2004 Presented at the Forty-Fifth Annual Meeting of The Society for Surgery of the Alimentary Tract, New Orleans, Louisiana, May 15–19, 2004  相似文献   
1000.
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