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   1534篇
  免费   69篇
  国内免费   11篇
耳鼻咽喉   15篇
儿科学   12篇
妇产科学   19篇
基础医学   122篇
口腔科学   17篇
临床医学   101篇
内科学   566篇
皮肤病学   14篇
神经病学   57篇
特种医学   93篇
外科学   258篇
综合类   14篇
预防医学   58篇
眼科学   7篇
药学   78篇
中国医学   15篇
肿瘤学   168篇
  2022年   7篇
  2021年   31篇
  2020年   22篇
  2019年   29篇
  2018年   38篇
  2017年   31篇
  2016年   45篇
  2015年   27篇
  2014年   25篇
  2013年   51篇
  2012年   100篇
  2011年   102篇
  2010年   55篇
  2009年   32篇
  2008年   86篇
  2007年   86篇
  2006年   74篇
  2005年   64篇
  2004年   75篇
  2003年   73篇
  2002年   70篇
  2001年   51篇
  2000年   54篇
  1999年   50篇
  1998年   20篇
  1997年   20篇
  1996年   8篇
  1995年   10篇
  1994年   9篇
  1993年   9篇
  1992年   29篇
  1991年   26篇
  1990年   29篇
  1989年   24篇
  1988年   20篇
  1987年   18篇
  1986年   15篇
  1985年   17篇
  1984年   10篇
  1983年   5篇
  1982年   3篇
  1981年   4篇
  1980年   6篇
  1979年   8篇
  1978年   12篇
  1974年   6篇
  1971年   3篇
  1969年   5篇
  1968年   3篇
  1967年   5篇
排序方式: 共有1614条查询结果,搜索用时 15 毫秒
1.
We describe a case of successful combined repair of the aortic and mitral valves for an indication of active infective endocarditis involving both valves. Mitral valve repair was achieved by vegetation debridement, fixation of the anterior mitral commissure, resection and suturing of the posterior mitral leaflet, and posterior annuloplasty with autologous pericardium. Aortic valve repair was achieved by vegetectomy and commissural plication. Postoperative clinical course was without signs of recurrent infection, and echocardiogram demonstrated mitral valve competence with trivial aortic regurgitation. We concluded that simultaneous valve repair is a viable option in the context of active endocarditis.  相似文献   
2.
Virulent influenza A viruses induce apoptosis in chickens   总被引:19,自引:0,他引:19  
Virulent avian influenza A viruses produce lethal disease in chickens. Since cell death can be caused by either necrosis or apoptosis, we investigated the types of cell death that occur in natural hosts, chickens, infected with virulent avian viruses. Using biochemical methods, we demonstrate that virulent avian influenza viruses induce apoptosis of vascular endothelial cells in liver, kidney, and brain. Viral antigens were also detected in these organs, suggesting that viral replication induces apoptosis in infected chickens. These results indicate that apoptosis does occur in virulent avian influenza virus infection in a natural host, and may contribute to the lethality of the virus.  相似文献   
3.
We encountered a patient who showed remarkably high binding capacities of both 125I-T4 and 125I-T3, which suggests the presence of antithyroid hormone autoantibody. However, the serum level of T3 in the patient was not abnormal. Study of the specificity of anti-thyroid autoantibody revealed that the antibody present in the patient was the anti T4 antibody, which cross-reacted with T3. In addition, the binding capacity of the T4 autoantibody with T3 was inhibited by T4. Endogenous T4 is always present when T3 is determined by radioimmunoassay. Our findings indicate that the normal T3 level in the patient was because endogenous T4 inhibited the autoantibody binding with T3.  相似文献   
4.
To cast light on tumorigenesis in the remnant stomach after distal gastrectomy for peptic ulcer or gastric cancer, 45 cases in gastroduodenostomy (Billroth I, 17 cases) and gastrojejunostomy (Billroth II, 28 cases) groups were compared for a series of parameters. Cancers in Billroth II were significantly more predominant in the anastomosis area and more frequently associated with Epstein-Barr virus infection. Active gastritis, accelerated epithelial cell turnover (as assessed by measurements of apoptosis and cell proliferation), DNA damage, and foveolar cell hyperplasia were all greater in anastomotic areas after Billroth II than in proximal areas after Billroth II or either area after Billroth I. K-ras mutations were rare, but Epstein-Barr virus infection in cancers was seen frequently in anastomosis cases. In conclusion, active gastritis, possibly induced by enterogastric reflux, is linked to tumorigenesis in anastomosis sites in Billroth II cases.  相似文献   
5.
Mitsuo  Honda  Kazunori  Miura Tomio  Tanigawa 《Allergy》1982,37(1):41-47
Azelastine, a newly synthesized anti-allergic agent, was tested for its effects on guinea pig macrophage chemotaxis and phagocytosis. As specific macrophage chemo-attractants, we used macrophage chemotactic factors a and c; separated and highly purified from inflamed skin sites. Macrophage chemotaxis induced by skin extract or chemotactic factors was significantly suppressed by a low concentration of the agent (1 microgram/ml); the effect was dose-dependent. The inhibition of chemotaxis was reversible, because chemotactic activity was restored when the agents was removed by washing cells before chemotactic assay. Inactivation of chemotactic factors was not detected by mixing azelastine and factors a and c. Azelastine may directly interact with macrophages to decrease their chemotactic responsiveness. beta-Glucuronidase activity in the medium and macrophages after phagocytosis of polystyrene latex particles was not affected by this agent at concentrations ranging from 1 to 10 micrograms/ml. The phagocytosis of latex particles or sheep red blood cells opsonized with IgG antibodies (EA) and anchoring of macrophages to substrate were not inhibited and azelastine did not damage the macrophages as determined by lactate dehydrogenase (LDH) release assay.  相似文献   
6.
5''-Deoxy-5-fluorouridine (5''-DFUR) and 1-(tetrahydro-2-furyl)-5-fluorouracil (tegafur), prodrugs of 5-fluorouracil (5-FU), are anticancer agents activated by thymidine phosphorylase (dThdPase). As it is well known that the levels of dThdPase are higher in tumours than in normal tissue, it should be advantageous to use such pyrimidine antimetabolites for the selective inhibition of tumour growth. However, tumours are not necessarily sensitive to 5''-DFUR and tegafur because their levels of dThdPase vary. In this study, we examined whether transfection of tumour cells with a human platelet-derived endothelial cell growth factor (PD-ECGF) complementary DNA (cDNA) expressing dThdPase would sensitize the cells to the cytotoxic effects of pyrimidine antimetabolites in vitro. A cDNA encoding PD-ECGF was transfected into PC-9 cells (human lung adenocarcinoma). The transfected cells, PC9-DPE2, had a more than 50 times higher activity of dThdPase than the parental PC-9 cells or control PC-9 cells transfected with the pcDNA3 vector alone (PC9-D1). They were more sensitive than parental PC-9 or PC9-D1 cells not only to 5''-DFUR and tegafur but also to 5-FU. In addition, we demonstrated that PC9-DPE2 cells are able to potentiate the cytotoxic effects of 5''-DFUR towards co-cultured parental PC-9 cells. This "bystander effect'' did not require cell-cell contact. These results suggest that transfection of PD-ECGF (dThdPase) genes may be useful as a gene therapy strategy for cancer treatment.  相似文献   
7.
Approximately 10-30% of the Japanese population suffer from Japanese cedar (Cryptomeria japonica) pollinosis in the spring. To date, the effects of this pollinosis on lymphocyte subpopulations have not been examined epidemiologically. To examine the effects of smoking and Japanese cedar pollinosis on lymphocyte subpopulations, we used flow cytometry to measure CD4+ and CD8+ T-lymphocyte subpopulations, natural-killer cell subpopulations, B(CD19+) lymphocytes, and total lymphocytes in 61 smokers and 51 nonsmokers. Some of these individuals had histories of pollinosis during November 1993-an off-season for Japanese cedar pollination. Our findings suggested that (a) CD4+ T-lymphocyte subpopulations (i.e., CD4+CD29+, CD4+CD45RA+, and CD4+ CD45RO+ cells) together with total CD4+ T, total T, and total lymphocytes, were increased by the effects of smoking; (b) CD8dim+CD11a+T, and CD8+CD11bt, and CD57+CD16+ natural killer cells, together with total CD8+CD11 a+ T and total CD8+ T lymphocytes, were increased by the effects of pollinosis on smokers, even though no lymphocyte subpopulations were increased by only the pollinosis effects; (c) CD4+CD29+T and CD8dimCD11a+ T lymphocytes were increased by the effects of smoking on pollinosis, and (d) CD4+CD29+ T and CD4+CD45RO+ T lymphocytes, CD8dim+CD11 a+ T, and CD8+CD11b+ T lymphocytes and CD57+CD16+ natural killer cells, together with total CD4+ T, total T (CD3+), total CD8+CD11a+, total CD8+ T, and total lymphocytes, were increased by the combined effects of smoking and pollinosis.  相似文献   
8.
Four patients were treated by placement of an expandable metallic stent (two Gianturco Z-stents, two Ultraflex stents) for malignant colorectal strictures. All four patients were able to defecate after stent placement. Stent migration was recognized in one patient. Two patients suffered from tenesmus after stent placement.  相似文献   
9.
A 65-yr-old man who underwent pancreaticoduodenectomy with portal vein resection for pancreatic cancer is alive 8 yr after surgery. Originally, computed tomography (CT) revealed an 8-cm tumor in the pancreatic head. The tumor had infiltrated the portal vein, but grew expansively, so there was neither biliary obstruction nor jaundice. Pancreaticoduodenectomy with resection of the portal vein was performed for pancreatic cancer. Many tumor-infiltrating lymphocytes were seen within cancer cell nests on routine histopathology. We performed immunostaining for CD8, and found that a large number of the lymphocytes were CD8+ T cells. The patient’s prognosis was considered poor because the tumor was large and had infiltrated the portal vein. We suspect that long-term survival may be related to the response of CD8+ T cells to the cancer.  相似文献   
10.
Thoracoscopic lung biopsy is becoming the procedure of first choice for the diagnosis of many localized and diffuse lung diseases. We have performed thoracoscopic lung biopsy for 17 patients with diffuse infiltrative lung disease, in Kurume University Hospital. There were 13 females and 4 males with a mean age of 48 years (range: 19-71 years). Thoracoscopic surgical biopsy was performed in the right lung in 12 and in the left lung in 5. Adequate lung tissue from each case was obtained for pathological examination. The mean surgical biopsy time was 49 min (range: 25-72 min) and bleeding was negligible. The mean duration for chest tube drainage was 2.6 days. No postoperative complication such as prolonged air leakage occurred. A specific diagnosis from the biopsy was achieved in 13 (76.4%) of the 17 cases. In only 6 (35.2%) of the 17 cases, the pathological diagnosis was the same as that from the thoracoscopic biopsy. In these 6 cases, the same diagnosis was obtained only in those with idiopathic interstitial pneumonitis or diffuse panbronchitis. Thoracoscopic lung biopsy was safe and useful for diagnosis for diffuse infiltrative lung disease.  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