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   2908篇
  免费   181篇
  国内免费   16篇
耳鼻咽喉   10篇
儿科学   113篇
妇产科学   42篇
基础医学   530篇
口腔科学   77篇
临床医学   202篇
内科学   681篇
皮肤病学   95篇
神经病学   193篇
特种医学   67篇
外科学   295篇
综合类   9篇
预防医学   200篇
眼科学   68篇
药学   226篇
中国医学   14篇
肿瘤学   283篇
  2023年   29篇
  2022年   47篇
  2021年   74篇
  2020年   46篇
  2019年   64篇
  2018年   65篇
  2017年   71篇
  2016年   74篇
  2015年   79篇
  2014年   80篇
  2013年   120篇
  2012年   184篇
  2011年   200篇
  2010年   115篇
  2009年   125篇
  2008年   187篇
  2007年   184篇
  2006年   217篇
  2005年   196篇
  2004年   189篇
  2003年   146篇
  2002年   152篇
  2001年   23篇
  2000年   16篇
  1999年   35篇
  1998年   36篇
  1997年   23篇
  1996年   18篇
  1995年   22篇
  1994年   24篇
  1993年   24篇
  1992年   21篇
  1991年   23篇
  1990年   21篇
  1989年   16篇
  1988年   11篇
  1987年   21篇
  1986年   15篇
  1985年   19篇
  1984年   11篇
  1983年   9篇
  1982年   9篇
  1981年   7篇
  1980年   9篇
  1978年   8篇
  1977年   4篇
  1976年   3篇
  1974年   8篇
  1973年   4篇
  1971年   3篇
排序方式: 共有3105条查询结果,搜索用时 15 毫秒
121.
BACKGROUND: Despite advances in diagnostic imaging techniques, the differentiation between pancreatic cancer and focal pancreatitis remains difficult. This study evaluated the effectiveness of EUS-guided FNA in the differential diagnosis between pancreatic cancer and focal pancreatitis, with particular reference to detection of the K-ras point mutation. METHODS: The study included 62 consecutive patients with pancreatic ductal cancer and 15 patients with focal pancreatitis demonstrated as a pancreatic mass lesion by EUS. RESULTS: Sensitivity, specificity, overall accuracy, positive predictive value, and negative predictive value of cytopathologic diagnosis were 82%, 100%, 86%, 100%, and 58%, respectively. Sensitivity, specificity, overall accuracy, positive predictive value, and negative predictive value of histopathologic diagnosis were 44%, 100%, 55%, 100%, and 32%, respectively. The K-ras point mutation was found in 74% of pancreatic cancers and 0% of focal pancreatitis lesions. No complication of EUS-guided FNA was observed. CONCLUSIONS: EUS-guided FNA is useful for the differential diagnosis of pancreatic mass lesions caused by pancreatic cancer and focal pancreatitis. Analysis for the K-ras point mutation in specimens obtained by EUS-guided FNA may enhance diagnostic accuracy in indeterminate cases.  相似文献   
122.
A high dose of tumor necrosis factor (TNF)-alpha induces endothelial dysfunction and enhances apoptosis in vitro. The present study was conducted to examine whether incubating human umbilical vein endothelial cells (HUVECs) with serum from Type 2 diabetic patients complicated with retinopathy and/or microalbuminemia demonstrate endothelial dysfunction. Serum levels of TNF-alpha and vascular endothelial growth factor (VEGF) were elevated in diabetic patients. Plasma levels of TNF-alpha, two soluble TNF-alpha receptors (sTNFR), and VEGF were assessed in diabetic patients (CD, n=21) complicated with retinopathy and/or nephropathy, uncomplicated diabetic patients (UD, n=18), and in healthy normal participants (NS, n=16). In HUVECs incubated with patient's serum, endothelial constitutive nitric oxide synthase (eNOS) protein expressions were measured by Western blot analysis. Apoptosis in HUVECs was determined by optical microscopy, DNA fragmentation, and CPP32-like protease activity. Serum TNF-alpha, sTNFR-I, and asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NOS, in CD were significantly higher than in UD or NS. While, serum sTNFR-I and VEGF levels were significantly increased in the both diabetic patients, compared with those of NS, no difference was observed in the serum TNF-alpha, sTNFR-II, and ADMA levels between UD and NS. eNOS down-regulation and apoptosis were seen in HUVECs incubated with serum from CD for 24 h, but those observations were completely counteracted in the incubation by the addition of the antihuman TNF-alpha antibody. These results imply that eNOS down-regulation in CD is associated with high serum TNF-alpha levels despite of high serum of VEGF levels. Therefore, endothelial dysfunction in diabetic patients complicated with microangiopathy may, in part, be attributed to high serum TNF-alpha levels.  相似文献   
123.
In the present study, we analyzed the kinetics of serum soluble interleukin-2 receptor (sIL-2R) using data from 77 patients undergoing HLA-haploidentical transplantation using reduced-intensity conditioning (RIC), who were at an advanced stage or at high risk for relapse, to clarify the usefulness of sIL-2R as a biomarker of acute graft-versus-host disease (GVHD). Anti-T-lymphocyte globulin and methylprednisolone were used as GVHD prophylaxis. While the median sIL-2R in 38 patients not developing GVHD was suppressed at levels <740 U/ml, sIL-2R in 25 patients developing severe GVHD peaked on day 11 (1,663 U/ml), and thereafter decreased to <1,000 U/ml after day 30. The occurrence of GVHD was not limited to times of high sIL-2R level, but occurred at any time point on the sIL-2R curve. Most patients developing GVHD, however, experienced a higher sIL-2R level early in their transplant course. The combination of RIC and glucocorticoids sufficiently suppressed sIL-2R levels after HLA-haploidentical transplantation. In a multivariate analysis to identify factors associated with GVHD, day 7 sIL-2R >810 U/ml was the only factor significantly associated with the occurrence of severe GVHD (p = 0.0101).  相似文献   
124.
Summary The culture fluids of various anaerobic bacteria induced the synthesis of early antigens (EA) in Epstein-Barr virus (EBV) carrying lymphoblastoid cells. The culture fluids ofCorynebacterium butyricum andFusobacterium nucleatum were the effective inducer on EA. The inducing activity was, to some extent, dependent on theirn-butyric acid content, but appeared to be regulated by yet unidentified materials.  相似文献   
125.
Although hyperfunctioning mediastinal parathyroid lesions that require median sternotomy or thoracotomy for removal are occasionally present, the majority are located in the anterior mediastinum closely associated with the thymus. Only eight cases of ectopic hyperfunctioning parathyroid tumors in the middle mediastinum have been reported. We experienced two cases of either persistent or recurrent hyperparathyroidism in which abnormal parathyroid tissue was located in the aorticopulmonary window. One of the patients had a parathyroid adenoma and the other had metastatic lesions of parathyroid carcinoma. In both cases, thallium scanning proved useful in identifying the lesions while computed tomography scan was effective for mediastinal three-dimensional localization. In one case, single photon emission computed tomography imaging with thallium proved beneficial for both identification and localization of the middle mediastinal lesion. The surgical approach used in both cases was different. In one case, left thoracotomy was performed, after which the ligamentum arteriosum was divided, and an adenoma anterior to the left main bronchus and posterior to the left pulmonary artery removed. In the other case, two metastatic tumors of parathyroid carcinoma anterior to the right main bronchus and posterior to the right pulmonary artery were resected through a median sternotomy and opening of the pericardium.  相似文献   
126.
A 20-year-old woman with Marfan syndrome in the 19 weeks of pregnancy was admitted for a dissecting aneurysm of the ascending aorta to the proximal arch. She wanted to continue with pregnancy. A cardiotocography and a trans-esophageal echo probe which allowed visualization of the fetal heart contraction were attached on the abdomen. A cardio-pulmonary bypass was established via the right axillar and femoral arteries with bicaval drainage. The aortic isthmus and arch branches were clamped. After opening the ascending aorta, selective cerebral perfusion was initiated by quick cannulation into the left carotid and left subclavian arteries. Peripheral pressure was maintained above 80 mmHg with the flow of the selective cerebral perfusion at 1.0 L/min and flow from the femoral artery at 3.5 L/min. Hemi-arch replacement was performed using a Dacron graft. The body temperature passively descended to 35 °C. She normally delivered a healthy female baby after 37 weeks’ of gestation.  相似文献   
127.
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   
128.
We report a rare case of early gastric cancer confined to the mucosal layer with extensive duodenal invasion, curatively removed with distal gastrectomy. An 84‐year‐old Japanese woman was referred to our hospital with gastric cancer. A barium meal examination and esophagogastroduodenoscopy revealed an irregular nodulated lesion measuring 6.5 x 5.5 cm in the gastric antrum and an aggregation of small nodules in the duodenal bulb. A biopsy specimen showed well‐differentiated adenocarcinoma. The patient underwent distal gastrectomy with partial resection of the duodenal region containing the tumor and regional lymph node dissection, with no complication. Histological examination of the resected tissue confirmed well‐differentiated adenocarcinoma limited to the mucosal layer and without lymph node metastasis. The cancer extended into the duodenum as far as 38 mm distant from the pyloric ring, and the resected margins were free of cancer cells. Gastric cancer located adjacent to the pyloric ring thus has the potential for duodenal invasion, even when tumor invasion is confined to the mucosal layer. In such cases, care should be taken during examinations to detect duodenal invasion, and the distal surgical margin must be negative given sufficient duodenal resection.  相似文献   
129.
We herein present a case of recurrence of gastric cancer in the jejunal pouch after total gastrectomy in a 74-year-old man. He had a history of two operations for gastric cancer. The second operation was a completion gastrectomy with jejunal pouch reconstruction and regional lymphadenectomy, for gastric cancer in the cardia of the remnant stomach, performed 2 years and 9 months before the present admission. A follow-up endoscopy showed three elevated tumors along the suture lines in the jejunal pouch in the upper digestive tract. Resection of the jejunal pouch was performed. Gross pathological examination revealed elevated lesions along the staple suture lines in the jejunal pouch. Histopathologically, moderately differentiated tubular adenocarcinoma involving the muscular layer, without lymphatic metastases, was recognized. Recurrence of gastric cancer in the jejunal pouch after resection is rare. We suggest that implantation of exfoliated cancer cells gave rise to the recurrence of tumors on the suture line in this patient. We also review two cases of gastric cancer in the jejunal pouch after resection previously described in the literature.  相似文献   
130.
SM/J and A/J inbred strain of mice have different characteristics in circadian behaviors such as free-running period (), phase relationship () between light-dark cycles and activity rhythms, and amount of wheel-running activity. To determine the genes which affect these behaviors, a quantitative trait locus (QTL) analysis using SMXA recombinant inbred strains derived from SM/J and A/J mice was performed. Concerning , two regions on chromosomes (Chrs) 7 and 18 surpassed the genome-wide suggestive level. As for , one suggestive QTL was detected on Chr 7. The QTLs which affect daily activity counts under light-dark cycles and constant darkness were mapped to the same chromosomal regions on Chrs 1 and 17, respectively. The provisional QTLs detected in the present study might be useful for understanding the complex mechanism regulating circadian behaviors.  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