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   2748篇
  免费   126篇
  国内免费   25篇
耳鼻咽喉   12篇
儿科学   72篇
妇产科学   72篇
基础医学   292篇
口腔科学   127篇
临床医学   254篇
内科学   660篇
皮肤病学   44篇
神经病学   158篇
特种医学   366篇
外科学   273篇
综合类   17篇
预防医学   97篇
眼科学   16篇
药学   179篇
中国医学   4篇
肿瘤学   256篇
  2022年   20篇
  2021年   37篇
  2020年   32篇
  2019年   40篇
  2018年   54篇
  2017年   28篇
  2016年   34篇
  2015年   47篇
  2014年   62篇
  2013年   78篇
  2012年   119篇
  2011年   119篇
  2010年   59篇
  2009年   98篇
  2008年   77篇
  2007年   99篇
  2006年   108篇
  2005年   134篇
  2004年   137篇
  2003年   86篇
  2002年   72篇
  2001年   80篇
  2000年   79篇
  1999年   62篇
  1998年   70篇
  1997年   58篇
  1996年   78篇
  1995年   75篇
  1994年   44篇
  1993年   48篇
  1992年   41篇
  1991年   42篇
  1990年   60篇
  1989年   71篇
  1988年   68篇
  1987年   56篇
  1986年   49篇
  1985年   56篇
  1984年   38篇
  1983年   30篇
  1982年   34篇
  1981年   29篇
  1980年   16篇
  1979年   13篇
  1978年   11篇
  1977年   34篇
  1976年   21篇
  1975年   18篇
  1971年   11篇
  1969年   9篇
排序方式: 共有2899条查询结果,搜索用时 15 毫秒
81.
AIM: The aim of this study was to evaluate the practice of colonoscopy and sigmoidoscopy in France in 2000. METHODS: A prospective study was conducted in November 2000 using questionnaires sent to all gastroenterologists practicing in France (N=2858) who were asked to reply to items concerning colonoscopies and sigmoidoscopies performed on two workdays chosen in advance. The response rate was 32.8%. Data were extrapolated to establish estimates for the entire year. RESULTS: An estimated 894000 colonoscopies and 115320 sigmoidoscopies were performed in 2000. Single-use material was used in 22.1% of the procedures. Indications for endoscopy were mainly hematochezia (21.6%), gastrointestinal symptoms (35%) and surveillance of patients with a history of previous polypectomy (15%). Colorectal cancer screening was the indication for 20% of colonoscopies. Abnormal findings were reported for 54.8% of the endoscopies (polyps for 287218 procedures and cancer for 32799). Failure was noted in 4.9% of colonoscopies. The complication rate was 0.48%. Most polyps were adenomas (64.4%) or hyperplasic polyps (28.1%). The overall estimated number of colonoscopies with polypectomy was 224133. CONCLUSION: In 2000 there was an increased rate of colonoscopy for colorectal cancer screening (20%) but an overall decrease (2.5%) in the total number of colonoscopies compared to 1999. Abnormal findings were disclosed by 54.8% of the procedures. Extrapolation from these data indicates that colonoscopic screening enabled the diagnosis of 32799 colorectal cancers.  相似文献   
82.
Cerebral malaria is thought to involve specific attachment of Plasmodium falciparum-infected knobby red cells to venular endothelium. The nature of surface ligands on host endothelial cells that may mediate cytoadherence is poorly understood. We have investigated the effects of soluble thrombospondin, rabbit antiserum raised against thrombospondin, and human immune serum on cytoadherence of parasitized erythrocytes in ex vivo mesocecum vasculature. Preincubation of infected red cells with soluble thrombospondin or human immune serum inhibits binding of infected red cells to rat venular endothelium. Infusion of the microcirculatory preparation with rabbit antithrombospondin antibodies before perfusion of parasitized erythrocytes also resulted in decreased cytoadherence. In addition, incubation of infected cells with human immune sera obtained from malaria patients significantly inhibited the observed cytoadherence. Our results indicate that thrombospondin mediates binding of infected red cells to venular endothelium and may thus be involved in the pathogenesis of cerebral malaria.  相似文献   
83.
The occurrence of small-bowel cancer in Crohn's disease (CD) is a rare event. The risk seems to be greatest in patients with long-standing disease. Strictureplasty has proved to be a valuable alternative in the management of Crohn's strictures of the small-bowel. Critics and proponents of strictureplasty for selected patients with smallbowel Crohn's disease have voiced their concerns about cancer risk in the strictured or strictureplasty site. To date, there has been no clear or detailed report of such an occurrence. The authors report the first case of small-bowel adenocarcinoma arising at the site of a previous strictureplasty. In this patient, biopsies of the strictures at the original operation confirmed CD and excluded both cancer and dysplasia. Malignancy occurred seven years later at a strictureplasty site. The main clinical sign associated with the adenocarcinoma was severe, persistent anemia. The authors conclude that the risk of adenocarcinoma developing at the site of a previous strictureplasty for CD, although small, is real.  相似文献   
84.
Depressive rumination is an emotion regulation strategy that is considered a major risk factor for depression and other emotional disorders. While well-established measures of trait rumination are available, a psychometrically sound measure of state rumination is lacking. We report on the development and validation of a new self-report measure, the Brief State Rumination Inventory (BSRI), in both Dutch and English. In Study 1, we report the results of a multi-group confirmatory factor analysis across three independent samples (n?=?155; n?=?141; n?=?199). The analysis supported the unidimensionality and measurement invariance of the 8-item BSRI. We also examined its construct validity, showing that scores on the BSRI were positively related to measures of negative affect, trait rumination, and symptoms of depression and anxiety. Scores were negatively related to adaptive emotion regulation strategies and to positive affect. In Study 2 (n?=?60), we demonstrated the measure’s sensitivity to an experimental manipulation of rumination. Taken together, these findings suggest that the BSRI is a quick-to-administer, valid, and reliable measure of state rumination.  相似文献   
85.
Clinical Rheumatology - Kawasaki disease (KD) is the most frequent cause of acquired heart disease in children in high-income countries because of coronary artery involvement. Risk factors for...  相似文献   
86.
This study investigated the effects of metformin on pancreatic A-B- and D-cell functions using the isolated perfused rat pancreas model. The lactate output rate following metformin infusion was also monitored. Metformin was infused at the low "therapeutic" concentration of 1.5 micrograms/ml and its effects were evaluated in three different glycaemic conditions: during a basal infusion of 4.44 mM glucose, during a moderate increase to 8.88 mM of glucose concentration, and finally during a higher 16.66 mM glycaemic stimulus. Basal insulin secretion and B-cell release during the lower hyperglycaemic stimulus were unaffected by metformin infusion. On the contrary, the drug significantly enhanced insulin response to 16.66 mM glucose, particularly by increasing the second phase of hormone release. Glucagon and somatostatin releases during metformin infusion were similar to the secretory pattern observed in the control experiments both in the basal condition and in the presence of the two different hyperglycaemic stimuli. Finally metformin did not modify the lactate output rate from perfused pancreas, irrespective of the different glycaemic conditions employed. Therefore our data suggest--at least in rats, in in vitro experiments but above all in the presence of markedly elevated hyperglycaemic conditions--that metformin may influence the glucose stimulatory effect on B-cell activity.  相似文献   
87.
88.
Summary. The molecular defects causing CRM+ factor VII deficiency were investigated in seven unrelated subjects and several members of their families.
Four missense mutations located in the catalytic domain of factor VII were found. The previously reported 304ArgGln substitution was present in the homozygous and heterozygous forms, with different polymorphic haplotypes, thus demonstrating that it is recurrent and frequent in the Italian population. The 310Cys Phe substitution was found in the homozygous form and in the compound heterozygous condition with the nonsense mutation 356Trpstop. Two missense mutations, 298MetIle and 342GlyArg, were found in the homozygous and in the heterozygous condition respectively.
Molecular heterogeneity was further increased by finding of the 353ArgGln polymorphism in the doubly heterozygous condition with the 304 and 342 mutations.
Plausible explanations for loss of FVII function were found by inspecting a model of the serine protease domain of factor VIIa. Inefficient activation of the catalytic site is predicted for 298MetIle. 342GlyArg would directly distort the geometry of the 'oxyanion hole'preventing formation of a substrate enzyme intermediate. 310Cyshe is predicted to have an adverse effect on tissue factor interaction. These mutations point to important regions of the factor VII molecule.  相似文献   
89.
90.
From October 1, 1984 to December 31, 1991 at the Clinica Chirurgica II of the University of Bologna, 140 patients submitted to ileal pouch-anal anastomosis for ulcerative colitis (UC) and familial adenomatous polyposis (FAP). Nineteen patients (13.5 percent) developed septic complications. Of these, 11 patients (7.8 percent) had pelvic sepsis. Eight patients required further surgical intervention. Five patients underwent the redo pouch procedure. Another redo pouch was performed in a patient who had previously, in another hospital, had an ileal pouch-anal anastomosis placed and then removed because of ischemic necrosis of the reservoir. No deaths are reported in the reoperated patients. Currently, five of the six patients who underwent the redo pouch procedure have a well-functioning ileoanal anastomosis. The redo pouch procedure should always be attempted prior to the establishment of pelvic fibrosis.  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