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   3135036篇
  免费   267459篇
  国内免费   13880篇
耳鼻咽喉   43497篇
儿科学   96338篇
妇产科学   80975篇
基础医学   504521篇
口腔科学   86153篇
临床医学   279633篇
内科学   543016篇
皮肤病学   84814篇
神经病学   271687篇
特种医学   125156篇
外国民族医学   196篇
外科学   492364篇
综合类   101240篇
现状与发展   24篇
一般理论   2177篇
预防医学   265029篇
眼科学   71220篇
药学   215787篇
  22篇
中国医学   9108篇
肿瘤学   143418篇
  2021年   54505篇
  2020年   34765篇
  2019年   57633篇
  2018年   69897篇
  2017年   53230篇
  2016年   58761篇
  2015年   73190篇
  2014年   107268篇
  2013年   172250篇
  2012年   82814篇
  2011年   80703篇
  2010年   113169篇
  2009年   118808篇
  2008年   68035篇
  2007年   70238篇
  2006年   81487篇
  2005年   77164篇
  2004年   79691篇
  2003年   70913篇
  2002年   60569篇
  2001年   83958篇
  2000年   76108篇
  1999年   79964篇
  1998年   63057篇
  1997年   61522篇
  1996年   59261篇
  1995年   54807篇
  1994年   49142篇
  1993年   45971篇
  1992年   57328篇
  1991年   54583篇
  1990年   51791篇
  1989年   51373篇
  1988年   48154篇
  1987年   47064篇
  1986年   44872篇
  1985年   45466篇
  1984年   43532篇
  1983年   40207篇
  1982年   40250篇
  1981年   38092篇
  1980年   36017篇
  1979年   36865篇
  1978年   33504篇
  1977年   30825篇
  1976年   28033篇
  1975年   26555篇
  1974年   27674篇
  1973年   26591篇
  1972年   25028篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
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   
993.
994.
995.
A total of 42 patients with recurrent superficial bladder tumors or carcinoma in situ entered a prospective, randomized trial to compare the efficacy of bacillus Calmette-Guerin therapy with and without quarterly maintenance instillations of bacillus Calmette-Guerin. Maintenance therapy did not reduce further bladder tumor recurrence rates or the interval to recurrence in patients who responded to the initial course of therapy. However, prolongation of toxicity was observed with maintenance bacillus Calmette-Guerin therapy.  相似文献   
996.
In the brain of quaking and shiverer mutants, vitamin E content was normal when related to both wet weight and dry weight. When related to lipid extract, phosphorus, and polyunsaturated fatty acids, vitamin E was slightly increased only in the quaking mutant. In the sciatic nerve from trembler mutants, vitamin E was 134% of control values in the dry material, but normal in relation to wet weight. It was 260% in the lipid extract and 716% based on phosphorus. In relation to total fatty acids, there was a threefold increase in trembler mutants. Interestingly, it was increased approximately three times when related to 18∶2 n?6, 20∶4 n?6, and 20∶5 n?3, and seven times when related to 22∶6 n?3. The fact that the amount of vitamin E in fresh weight was normal, suggests that vitamin E plays a role in some nonmembrane material, such as the extracellular matrix or the basal lamina.  相似文献   
997.
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   
998.
We compared the biomechanical properties of passive and stimulated muscle rapidly lengthened to failure in an experimental animal model. The mechanical parameters compared were force to tear, change in length to tear, site of failure, and energy absorbed by the muscle-tendon unit before failure. Paired comparisons were made between 1) muscles stimulated at 64 Hz (tetanic stimulation) and passive (no stimulation) muscles, 2) muscles stimulated at 16 Hz (wave-summated stimulation) and passive muscles, and 3) muscles stimulated at 64 Hz and at 16 Hz. Both tetanically stimulated and wave-summation contracted muscles required a greater force to tear (at 64 Hz, 12.86 N more, P less than 0.0004; and at 16 Hz, 17.79 N more, P less than 0.003) than their nonstimulated controls, while there was no statistical difference in failure force between muscles stimulated at 16 Hz and 64 Hz. The energy absorbed was statistically greater for the stimulated muscles than for the passive muscles in Groups 1 and 2 (at 64 Hz, 100% more, P less than 0.0003; and 16 Hz, 88% more, P less than 0.0002). In Group 3, the tetanically contracted muscle-tendon units absorbed 18% more energy than the wave-summated stimulated muscles (P less than 0.01). All muscles tore at the distal musculotendinous junction, and there was no difference in the length increase at tear between muscles in each group. These findings may lead to enhanced understanding of the mechanism and physiology of muscle strain injuries.  相似文献   
999.
1000.
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   
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