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   4601篇
  免费   236篇
  国内免费   11篇
耳鼻咽喉   16篇
儿科学   77篇
妇产科学   41篇
基础医学   632篇
口腔科学   69篇
临床医学   383篇
内科学   1120篇
皮肤病学   274篇
神经病学   310篇
特种医学   148篇
外科学   755篇
综合类   40篇
预防医学   333篇
眼科学   61篇
药学   304篇
中国医学   5篇
肿瘤学   280篇
  2023年   21篇
  2022年   23篇
  2021年   91篇
  2020年   43篇
  2019年   79篇
  2018年   87篇
  2017年   53篇
  2016年   64篇
  2015年   86篇
  2014年   120篇
  2013年   172篇
  2012年   278篇
  2011年   325篇
  2010年   166篇
  2009年   169篇
  2008年   313篇
  2007年   297篇
  2006年   302篇
  2005年   320篇
  2004年   307篇
  2003年   279篇
  2002年   249篇
  2001年   71篇
  2000年   68篇
  1999年   69篇
  1998年   73篇
  1997年   53篇
  1996年   34篇
  1995年   39篇
  1994年   35篇
  1993年   37篇
  1992年   52篇
  1991年   55篇
  1990年   35篇
  1989年   27篇
  1988年   36篇
  1987年   27篇
  1986年   30篇
  1985年   25篇
  1984年   25篇
  1983年   21篇
  1981年   13篇
  1980年   15篇
  1979年   12篇
  1978年   11篇
  1977年   10篇
  1975年   10篇
  1974年   13篇
  1972年   12篇
  1968年   10篇
排序方式: 共有4848条查询结果,搜索用时 15 毫秒
1.
2.
3.
Considering that the 1.32-μm Nd-YAG laser should have physicothermal properties close to those of the CO2 laser, a series of experiments were conducted on rat cortex (N = 51). Three laser wavelengths were compared: CO2 laser (10.6 μm), 1.06-μm Nd-YAG, and 1.32-μm Nd-YAG lasers. For each shot, temperature measurements were recorded with an infrared thermographic videocamera. The digitized signals were figured as thermal profiles and temperature developments. Ninety-five shots were correctly studied and analyzed: CO2, N = 29; 1.06-μm Nd-YAG, N = 20; 1.32-μm Nd-YAG, N = 46. The histological lesions produced by these three lasers were compared on animals killed 24 hours (N = 20), 8 days (N = 20), and 30 days (N = 5) after the laser impacts. For equivalent densities of energy, the depth of cortical necrosis was comparable for the CO2 laser (200–250 μm) and the 1.32-μm Nd-YAG laser (210–260μm) whatever the date of death; the 1.06-μm Nd-YAG laser shots were responsible for much more important damage (400–550μm). Because of its important absorption in water and nervous tissue, the authors consider the 1.32-μm Nd-YAG laser most suitable for neurosurgery, particularly because it is conducted through optic fibers, and therefore is easy to handle during neurosurgical procedures.  相似文献   
4.
BACKGROUND: An imbalance in the ratio of arachidonic acid and docosahexaenoic acid (DHA) was found in cystic fibrosis (CF) affected tissues and was suggested to promote inflammation. Several studies have shown that the long chain n-3 fatty acids reduced inflammatory activity while others have highlighted prooxidant activity of DHA at high concentrations. The aim of our study was to evaluate the effects of an intravenous fish-oil emulsion enriched with n-3 FA in patients with CF on plasma and platelet FA composition and peroxidation markers. METHODS: 13 patients with CF received one IV emulsion per week of 2 mL/kg fish-oil n-3 emulsion for 12 weeks. RESULTS: There was a significant increase in 20:5 n-3 and 22:6 n-3 platelet FA composition, no variation in 20:4 n-6, a decrease in n-9. There was no variation in plasma FA composition. Specific urinary markers of lipid peroxidation derived from n-3 and n-6 showed a very high level before infusion compared with usual values in healthy subjects which was not affected by treatment. A significant weight loss and a decrease in reduced glutathione were observed in adult patients. CONCLUSIONS: The intravenous administration of n-3 FA in CF patients induced a significant modification in platelet FA composition but no modification of oxidative markers. However, the weight loss and the decreased level in reduced glutathione observed in adult patients may suggest a potential deleterious activity for some patients. Further studies are necessary to determine the optimal dose and route for long chain FA administration required to reach a potential beneficial effect.  相似文献   
5.
Background: Although opioids are unsurpassed analgesics, experimental and clinical studies suggest that opioids activate N-methyl-d-aspartate pronociceptive systems leading to pain hypersensitivity and short-term tolerance. Because it is difficult in humans to differentiate pain from hyperalgesia during the postoperative period, the authors performed experimental studies with fentanyl using the rat incisional pain model for evaluating relations between hyperalgesia and short-term tolerance. Because N-methyl-d-aspartate receptor antagonists oppose both pain hypersensitivity and tolerance induced by opioids, the authors examined the capability of ketamine for improving exaggerated postoperative pain management.

Methods: During halothane anesthesia, a hind paw plantar incision was performed in rats receiving four fentanyl subcutaneous injections (100 [mu]g/kg per injection, every 15 min). In some groups, three subcutaneous ketamine injections (10 mg/kg per injection, every 5 h) were performed in saline- or fentanyl-treated rats. One day after surgery, the analgesic effect of morphine (2 mg/kg subcutaneous) was tested. Analgesia, mechanical hyperalgesia, tactile allodynia, and pain score were assessed for several days using the paw pressure vocalization test, the von Frey application test, and the postural disequilibrium test.

Results: Fentanyl induced analgesia but also produced exaggerated postoperative pain as indicated by the enhancement of hyperalgesia, allodynia, and weight-bearing decrease after hind paw plantar incision. Ketamine pretreatment prevented such a fentanyl-induced enhancement of postoperative pain and improved its management by morphine.  相似文献   

6.
A case of pulmonary Langerhans cell histiocytosis, proved by both lung high-resolution computed tomography and lung biopsy, is described. Following smoking cessation, lung nodules and cysts gradually disappeared on serial computed tomography scans, with complete clearance of the lesions after 12 months. The role of tobacco smoking is discussed, in detail, against the background of the literature.  相似文献   
7.
The production of monoclonal autoantibodies derived from individuals with autoimmune diseases constitutes a powerful tool to analyse an autoimmune process at both the antigen and antibody levels. We established a human anti-epithelial cell surface monoclonal antibody by applying hybridoma technology using peripheral blood lymphocytes from a patient with pemphigus vulgaris using a heteromyeloma as the fusion partner. The F12 monoclonal antibody displays four major characteristics: (1) it belongs to the IgM, kappa class; (2) it binds to the cell surface of stratified squamous and simple epithelia; (3) it recognizes an antigenic determinant associated with the desmosomal complex as demonstrated by indirect immunoelectron microscopy; (4) by immunoblotting analysis, it reacts with a 185 kDa polypeptide which was also recognized by a few pemphigus vulgaris sera. Although the F12 monoclonal antibody does not have the immunochemical properties of classical pemphigus vulgaris autoantibodies, several arguments suggest its relevance to the pemphigus vulgaris autoimmune response and, therefore, the heterogeneity of the antigen/antibody systems involved in this autoimmune disorder.  相似文献   
8.
Hepatobiliary scintigraphy in a patient with bilhemia   总被引:1,自引:0,他引:1  
A 4-year-old child referred for acute jaundice following percutaneous needle biopsy of the liver underwent hepatobiliary scintigraphy. Although all conventional liver tests suggested preservation of hepatocyte function, the tracer uptake in the liver appeared dramatically reduced at scintigraphy and the blood pool activity did not decrease significantly until the end of the study. Visualization of the bile ducts indicated, however, that the tracer was taken up by the hepatocyte and further excreted into the biliary tree. There was no tracer pooling in the biliary tree although no bowel activity was observed, even on delayed images. The association of persistent blood pool activity, bile duct visualization without tracer pooling, and nonvisualization of the bowel was caused by a continuous recirculation of the tracer from the biliary tree into the bloodstream. The presence of a biliovenous fistula was further proven by percutaneous transhepatic cholangiography performed 24 h later. Since 1975, only 16 cases of bilhemia have been reported. To the best of our knowledge the scintigraphic pattern of this rare but lifethreatening complication has not previously been reported.  相似文献   
9.
Adhesive properties of Haemophilus influenzae to different human cells   总被引:1,自引:0,他引:1  
The adhesion of 19 nontypable strains and 3 typable (type b) Haemophilus influenzae to human cells was examined using buccal epithelial cells (BEC), the continuous HEp-2 cell line and human 0 erythrocytes. The strains were classified into three phenotypes, according to their adhesive properties. Phenotype 1 consists of strains that adhere to both buccal epithelial cells and HEp-2 cells. Phenotype 2 consists of strains that adhere to both buccal epithelial cells and erythrocytes and strains belonging to phenotype 3 adhere to none of the three cell types used. Among 22 strains studied, 18 (81.8%) belonged to phenotype 1, 2 (9.1%) to phenotype 2 and 2 (9.1%) to phenotype 3. Fimbriae were observed for 11 (61%) among the 18 adherent strains belonging to phenotype 1. The 7 nonpiliated strains adhered with a significant adhesion index, thus this results would indicate that a non fimbrial adhesin exists.  相似文献   
10.
Mirizzi's syndrome is the name given to common bile duct obstruction secondary to a stone in the cystic duct. The cause of the biliary obstruction is often difficult to establish before operation. We report two cases of Mirizzi's syndrome, diagnosed endoscopically and treated without surgery. One of the patients was treated by drainage of both the common bile duct and the gallbladder associated with monooctanoin dissolution of the gallstone. The other was treated by common bile duct stenting.  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