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   894717篇
  免费   73767篇
  国内免费   1873篇
耳鼻咽喉   12998篇
儿科学   25685篇
妇产科学   25975篇
基础医学   128793篇
口腔科学   26093篇
临床医学   79367篇
内科学   170440篇
皮肤病学   17499篇
神经病学   73021篇
特种医学   36526篇
外国民族医学   174篇
外科学   140324篇
综合类   25239篇
现状与发展   2篇
一般理论   304篇
预防医学   70769篇
眼科学   21325篇
药学   67014篇
中国医学   1654篇
肿瘤学   47155篇
  2018年   7924篇
  2015年   8274篇
  2014年   11868篇
  2013年   17942篇
  2012年   24302篇
  2011年   25417篇
  2010年   14809篇
  2009年   13948篇
  2008年   24015篇
  2007年   26125篇
  2006年   26044篇
  2005年   25569篇
  2004年   25150篇
  2003年   24181篇
  2002年   23268篇
  2001年   36993篇
  2000年   37613篇
  1999年   31900篇
  1998年   9650篇
  1997年   8915篇
  1996年   8803篇
  1995年   8278篇
  1994年   8029篇
  1992年   27334篇
  1991年   26716篇
  1990年   26240篇
  1989年   25251篇
  1988年   23794篇
  1987年   23384篇
  1986年   22235篇
  1985年   21615篇
  1984年   16826篇
  1983年   14333篇
  1982年   9080篇
  1981年   8426篇
  1980年   7897篇
  1979年   17087篇
  1978年   12377篇
  1977年   10389篇
  1976年   9540篇
  1975年   10351篇
  1974年   12850篇
  1973年   12342篇
  1972年   11743篇
  1971年   10883篇
  1970年   10398篇
  1969年   10083篇
  1968年   9035篇
  1967年   8359篇
  1966年   7757篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Carotid sonography is being performed on more than 5,000 participants in the Cardiovascular Health Study, a prospective, multicenter study of cardiovascular disease in men and women aged 65 years and older. The sonographic methods used to examine and measure the extracranial carotid arteries are described. Initial validation studies were performed on 61 subjects with a mean age of 68.6 years. Analysis of within- and between-sonographer differences and between-reader differences were performed for selected variables. In general, the mean absolute differences for within- and between-sonographer comparisons were small, with even less variability between readers. Variability was less for the common carotid artery than for the internal carotid artery. These data suggest that carotid sonography is a reliable and reproducible method for use in the study of carotid atherosclerosis in population studies.  相似文献   
102.
103.
Computed tomography of the brain in the Smith-Lemli-Opitz syndrome   总被引:1,自引:0,他引:1  
Computed tomographic (CT) scans of the brain in a child with Smith-Lemli-Opitz syndrome revealed enlargement of the ventricular system, hypoplasia of the cerebellum, and abnormal thickening of the gray matter, consistent with pachygyria. These findings have been previously noted in autopsies performed on patients with this disorder. We conclude that CT scanning is a valuable tool in the evaluation of children suspected of having the Smith-Lemli-Opitz syndrome.  相似文献   
104.
In 1985, we initiated a prospective clinical trial to evaluate the risk of recurrence for superficial bladder cancer. Up to now, 41 patients subjected to TUR have subsequently been monitored by immunocytology with a monoclonal antibody (mab 486 p) recently developed in our laboratory. Of these patients, 15 (36.6%) remained marker-negative and received no prophylactic therapy. There was only one recurrence (6.7%) in this subset of patients, whereas 10 out of 26 (38.5%) marker-positive patients have so far developed recurrent malignancies. In all cases, the conversion of immunocytological characteristics preceded visible recurrence by 2-5 months. These preliminary results indicate that immunocytology might make it possible to identify patients at low risk of recurrence more accurately than has so far been feasible with standard cytology or flow-cytometry.  相似文献   
105.
106.
Biological oxidation of 2,4-diamino-6-substituted pyrimidines have been studied using hepatic microsomes from various mammalian species. The nature of the enzyme(s) involved in the oxidation has been elucidated using various enzyme inhibitors and inducing agents. The 3-N-oxides were formed with 6-piperidino-, 6-diethylamino-, 6-methyl-, and 6-chloro-substituted 2,4-diaminopyrimidines: no evidence of 1-N-oxide formation was obtained. With the 6-hydroxy-, 6-amino-, and unsubstituted 2,4-diaminopyrimidines and melamine, no N-oxidative metabolite was detected. The differences in N-oxide formation was discussed in terms of the effect of substituents on tautomerism and electron distribution. The N-oxygenation was mediated via a cytochrome P450 dependent system.  相似文献   
107.
Positron emission tomography (PET) with fluorodeoxyglucose (FDG), magnetic resonance imaging (MRI), and CT were carried out in a patient with Alzheimer's disease 16 months before he died. At autopsy, the gross appearance of the brain correlated with MRI and CT, which showed some regional atrophy. These were much less revealing than PET, which correlated with microscopic findings of neuronal loss and proliferation of glia. In areas of moderately impaired local cerebral metabolic rate of glucose, as revealed by reduced FDG uptake, there was some gliosis, primarily around the numerous senile plaques. In areas of severe metabolic impairment, there was a profound loss of neurons, extensive gliosis, and a diminished appearance of plaques. PET-FDG is a better measure of the severity of Alzheimer's disease than MRI or CT, because it reflects the degree of neuronal pathology.  相似文献   
108.
109.
Neutropenic enterocolitis in adults with acute leukemia   总被引:2,自引:0,他引:2  
Neutropenic enterocolitis has been previously described only by case reports and literature reviews. Of 499 adults with acute leukemia seen over a 23-year period (1962 to 1985), 13 cases (2.6%) of neutropenic enterocolitis have been reported. Eleven of these 13 patients were profoundly neutropenic (mean white blood cell count, 472/cu mm) and developed abdominal symptoms during either initial induction or relapse of acute leukemia. Histologic confirmation was available in ten cases, five cases after surgical resection and five cases at autopsy after nonoperative management. Three patients with isolated ileocecal inflammation without infarction at the time of surgery were successfully managed without resection. Five patients treated with surgery died four to 64 weeks postoperatively (mean survival, 21.6 weeks) of nonsurgical complications of leukemia. Three patients were still alive, one patient 42 months after right hemicolectomy and two patients five months after exploration only. All five patients managed medically died an average of 1.4 days (range, zero to four days) after the onset of abdominal pain. Survival in patients with acute leukemia who develop neutropenic enterocolitis is determined by early recognition and appropriate surgical exploration that can be expected to yield an acceptable operative mortality.  相似文献   
110.
Clinical experience of phototherapy for non-haemolytic hyperbilirubinaemia in 3999 infants in Kandang Kerbau Hospital, Singapore, is documented. Phototherapy was most effective in extremely preterm infants with very low birth weight (gestation less than or equal to 32 weeks, birth weight less than or equal to 1500 g) and least effective in full term infants with very low birth weight (gestation greater than or equal to 37 weeks, birth weight less than or equal to 1500 g) and large preterm infants (gestation less than 37 weeks, birth weight greater than 2270 g). Overall, phototherapy was effective in almost all the infants, with a failure rate of only 2.00/1000 infants. No characteristic features common to all the failures could be detected. The bilirubin rebound was usually mild; repeat phototherapy was required in only 30 infants (7.50/1000), with the response to the second exposure comparable to that to the first. No infant required a third exposure. All the infants tolerated phototherapy well, none developing any illness that could be attributed to the treatment. This clinical experience shows that phototherapy for the treatment of nonhaemolytic hyperbilirubinaemia is effective and safe.  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