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   8405篇
  免费   456篇
  国内免费   43篇
耳鼻咽喉   75篇
儿科学   132篇
妇产科学   112篇
基础医学   1036篇
口腔科学   362篇
临床医学   592篇
内科学   2246篇
皮肤病学   171篇
神经病学   699篇
特种医学   293篇
外科学   1208篇
综合类   33篇
预防医学   306篇
眼科学   109篇
药学   578篇
中国医学   12篇
肿瘤学   940篇
  2023年   42篇
  2022年   91篇
  2021年   137篇
  2020年   76篇
  2019年   106篇
  2018年   151篇
  2017年   128篇
  2016年   151篇
  2015年   163篇
  2014年   244篇
  2013年   269篇
  2012年   440篇
  2011年   528篇
  2010年   267篇
  2009年   228篇
  2008年   403篇
  2007年   403篇
  2006年   365篇
  2005年   399篇
  2004年   368篇
  2003年   416篇
  2002年   408篇
  2001年   263篇
  2000年   271篇
  1999年   290篇
  1998年   131篇
  1997年   82篇
  1996年   79篇
  1995年   82篇
  1994年   55篇
  1993年   45篇
  1992年   173篇
  1991年   153篇
  1990年   165篇
  1989年   131篇
  1988年   147篇
  1987年   143篇
  1986年   120篇
  1985年   132篇
  1984年   87篇
  1983年   76篇
  1982年   36篇
  1979年   40篇
  1978年   34篇
  1977年   35篇
  1974年   30篇
  1972年   27篇
  1971年   40篇
  1970年   30篇
  1969年   26篇
排序方式: 共有8904条查询结果,搜索用时 15 毫秒
71.
Background: Nevus of Ota is common in Japanese women, but most patients are not examined ophthalmologically. Methods: We performed ophthalmologic examinations on 16 Japanese women who had had bluish pigmentation in the periorbital region, sclera, and conjunctiva since birth. Results: Fifteen patients had unilateral involvement, and one had bilateral lesions. The visual acuities were good, and the intraocular pressures were within normal range. All patients had a negative family history. Three patients had light pigmentation in the optic disc in the affected eye. Conclusion: We believe that optic disc pigmentation associated with nevus of Ota, as found in these three patients, may be common but have been rarely described.  相似文献   
72.
73.
Internal mammary artery embolization for hemoptysis   总被引:2,自引:0,他引:2  
PURPOSE: The purpose of this study was to determine the factors influencing development of blood supply from the internal mammary artery and to discuss the value of embolization of the abnormal branches from this vessel using small particles following occlusion of the normal distal branches using microcoils in treating hemoptysis. MATERIAL AND METHODS: Five patients with hemoptysis underwent internal mammary artery embolization with coaxial microcatheter systems. Bronchoscopy, chest radiographs, and CT were performed to determine the site and extent of the basic disease before embolotherapy in all patients. RESULTS: In all patients, pulmonary lesions had extended from the lung to the adjacent pleural surface at the anterior lung field. Four patients underwent embolization from the proximal portion of the internal mammary artery following distal coil embolization. One patient who underwent only proximal embolization had recurrent bleeding. CONCLUSION: The internal mammary artery contributes to the perfusion of lesions responsible for hemoptysis when the basic lesion involves the pulmonary parenchyma adjacent to the anterior pleural surface. Initial distal occlusion of the internal mammary artery may improve the efficacy of embolization of this artery for hemoptysis.  相似文献   
74.
Endosonography during endoscopic mucosal resection to enhance its safety   总被引:5,自引:0,他引:5  
BACKGROUND: We have performed endoscopic mucosal resection of the esophagus (172 cases), stomach (102 cases), and colon (28 cases) using a transparent plastic cap. Because the lesion-bearing mucosa is suctioned up inside the cap under endoscopic suction, the mucosa should be dissected sufficiently from the proper muscle layer to prevent perforation. METHODS: To avert the risk of perforation, we introduced endosonographic assessment of submucosal dissection (47 cases). In all cases, just keeping the ultrasonic probe on the surface of the mucosa allowed us to evaluate whether the mucosal lesion was lifted up sufficiently from the proper muscle layer after local saline injection. RESULTS: It was possible to confirm that the muscle layer was kept outside the strangulating snare by the same procedure (32 of 37 cases, 86.5%). CONCLUSIONS: We experienced five muscular resections in cases without the ultrasonic probe and no muscular resection with the ultrasonic probe. Thus we recommend endosonographic assessment during endoscopic mucosal resection to enhance its safety.  相似文献   
75.
An 18-year-old male was admitted to our Emergency Department with a traumatic abdominal wall hernia (TAWH) of the left lower quadrant (LLQ) after suffering hypogastric blunt injury and urogenital lacerations in a motorcycle accident. Upright chest X-ray showed a small amount of right infradiaphragmatic free air, and a computed tomographic (CT) scan demonstrated an abdominal wall hernia. At surgery, no impairment was found in the digestive tract, and an abdominal herniorrhaphy was performed. It is suggested that the free air had passed through a connection between the scrotal laceration and the contralateral abdominal defect via the subcutaneous space and was palpated as emphysema. This is a new type of TAWH, which suggests that blunt abdominal trauma may result in negative pressure in the subcutaneous and peritoneal cavity, and this could reflect the pathophysiology of TAWH.  相似文献   
76.
77.
78.
BACKGROUND: Although extensive studies on the detailed mechanisms of ischemia-reperfusion injury have been conducted, the implication of the fibrinolytic system has not been known. To determine the role of the fibrinolytic system in ischemia-reperfusion injury, we used tranexamic acid, a synthetic specific plasmin and tissue-type plasminogen activator inhibitor, to suppress fibrinolytic activity in a rabbit lung ischemia-reperfusion model. METHODS: New Zealand White rabbits were randomly divided into two groups: a simple ischemia group and a group injected with tranexamic acid before left hilar occlusion. After 2 hours of warm ischemia, plasma was collected from pulmonary vessels. Fibrin zymography was used to ascertain fibrinolytic activity, and enzyme-linked immunosorbent assay was used to determine soluble thrombomodulin levels as a marker for endothelial cells damage. Changes in left pulmonary function including arterial oxygen tension, peak airway pressure, and pulmonary vascular resistance were recorded during reperfusion after the 2 hours of warm ischemia. RESULTS: Fibrinolytic activity and soluble thrombomodulin levels increased in the vessels of the ischemic lung, indicating endothelial cell injury. The increased fibrinolytic activity and the rise in soluble thrombomodulin were suppressed by the preadministration of tranexamic acid, resulting in remarkably improved pulmonary function during reperfusion. After 2 hours of reperfusion, the wet-to-dry weight ratios and histological studies showed reduced pulmonary edema in the group that had received tranexamic acid. CONCLUSION: These findings suggest that the fibrinolytic system is involved in the onset mechanism of ischemia-reperfusion injury through induced endothelial cell damage and increased vascular permeability.  相似文献   
79.
Low density lipoprotein (LDL) and lipoprotein(a) suppress catecholamine secretion in cultured adrenal medullary cells. Modification of LDL by oxidation or acetylation potentiates various atherogenic actions of LDL. In the present study, we investigated whether the modification of LDL influences catecholamine secretion in cultured bovine adrenal medullary cells. The exposure of LDL to CuSO4 caused a time-dependent oxidation of LDL. Maximal oxidation of LDL was observed after exposure to CuSO4 for 24 h. Native LDL inhibited catecholamine secretion induced by carbachol to 68.5% of control. Oxidized LDL caused further inhibition of carbachol-evoked secretion to 37.6% of control. Acetylated LDL inhibited it to 41.0% of control. There was a good correlation between the extent of LDL oxidation and the inhibition of catecholamine secretion. These results suggest that oxidation or acetylation of LDL augments its inhibitory effect on the secretion of catecholamines. Since catecholamines are a risk factor of atherosclerosis, the inhibitory effect by such modified LDL may be a mechanism inhibiting atherosclerotic progression. Received: 29 January 1999 / Accepted: 19 April 1999 / Published online: 22 June 1999  相似文献   
80.
Previous studies have shown that pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF) at suprapharmacological dose induces a mild transient decrease of red blood cell counts according to thrombopoiesis in normal mice. To unravel the mechanism underlying this mild transient decrease of red blood cells, we have studied the effect of PEG-rHuMGDF on the circulating plasma and blood volume, and the serum biochemical parameters of anaemia and splenectomy. Also, we have performed histological studies of the bone marrow and the spleen of PEG-rHuMGDF-treated rats. PEG-rHuMGDF (300 microg kg(-1)]) or vehicle was subcutaneously administered to rats once a day for up to five days. From day 6 after the start of PEG-rHuMGDF administration, the platelet counts and plateletcrit levels were significantly increased, reaching peak values on day 10, and recovering to normal by day 20. The red blood cell counts and the haematocrit levels were significantly decreased on day 6 to 13. The decreases in red blood cell levels and haematocrit produced by PEG-rHuMGDF treatment were mild and had recovered by day 15. The plasma and blood volumes were significantly increased on day 10 in PEG-rHuMGDF-treated rats. No alteration of the serum biochemical parameters for anaemia, iron or total bilirubin, were observed on day 10. The histological examination on day 10 revealed a marked increase in megakaryocytes and a slight decrease in erythropoiesis in the bone marrow of rats that received PEG-rHuMGDF (300 microg kg(-1)). There was also a slight increase in splenic megakaryocytes and erythropoiesis. The decrease of red blood cells by PEG-rHuMGDF was not affected by splenectomy. These results suggest that the mild transient decrease of red blood cells induced by PEG-rHuMGDF treatment for up to five days is based mainly on the increases in the plasma and blood volume. These events are secondary changes due to the regulation of the excess production of megakaryocytes in the marrow and the peripheral platelets.  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