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   21555篇
  免费   1373篇
  国内免费   63篇
耳鼻咽喉   344篇
儿科学   1210篇
妇产科学   538篇
基础医学   1904篇
口腔科学   403篇
临床医学   1677篇
内科学   5120篇
皮肤病学   352篇
神经病学   1099篇
特种医学   758篇
外国民族医学   2篇
外科学   3839篇
综合类   484篇
一般理论   3篇
预防医学   1233篇
眼科学   922篇
药学   1628篇
  1篇
中国医学   82篇
肿瘤学   1392篇
  2023年   159篇
  2022年   304篇
  2021年   817篇
  2020年   429篇
  2019年   642篇
  2018年   763篇
  2017年   521篇
  2016年   549篇
  2015年   549篇
  2014年   845篇
  2013年   1053篇
  2012年   1567篇
  2011年   1424篇
  2010年   898篇
  2009年   689篇
  2008年   1047篇
  2007年   1071篇
  2006年   1008篇
  2005年   924篇
  2004年   850篇
  2003年   718篇
  2002年   642篇
  2001年   509篇
  2000年   537篇
  1999年   425篇
  1998年   171篇
  1997年   146篇
  1996年   121篇
  1995年   123篇
  1994年   116篇
  1993年   90篇
  1992年   291篇
  1991年   261篇
  1990年   232篇
  1989年   231篇
  1988年   185篇
  1987年   189篇
  1986年   166篇
  1985年   174篇
  1984年   154篇
  1983年   147篇
  1982年   66篇
  1981年   76篇
  1979年   118篇
  1978年   86篇
  1977年   63篇
  1974年   79篇
  1973年   110篇
  1972年   101篇
  1971年   70篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
91.
OBJECTIVE: To assess the safety and efficacy of early amino acid (AA) administration in preterm neonates <28 weeks gestational age. STUDY DESIGN: Prospective data collection for 1 year for the late AA group (AA started at 12-30 h) and for another year with practice change to early AA administration (immediately after stabilization). RESULTS: Time of initiation of AA differed (early group 4+/-3 h vs late group 20+/-6 h; P<0.001). There were no statistically significant differences in the incidence of clinically significant metabolic acidosis. Blood urea at 24 h was higher in the early AA group. No significant differences in growth rate or neonatal outcomes were identified. Days to regain birth weight and sepsis were lower in the early AA group. CONCLUSIONS: Early AA administration was not associated with any clinically significant adverse effects; it was associated with reduction in the incidence of sepsis and marginally effective in reducing time to regain birth weight.  相似文献   
92.
Previous work showed that GABAergic differentiation in developing chick retina depends on insulin and cell interactions. Here, we investigated whether it depended on cell signaling mediated by retina cognin, a 50 kDa cell recognition molecule. Cognin mediates cell adhesion in vitro and occurs on retinal neurons that become both GABAergic and cholinergic. We investigated two markers of GABAergic differentiation: glutamate decarboxylase (GAD) activity and high-affinity GABA uptake. Both increase during differentiation of retinal neurons in culture and can be easily measured. We blocked cognin-mediated cell signaling with cognin antibody and found a reduction of the developmental increase in GAD activity in cultures of retinal neurons from 7 and 11 day chick embryos. There was no reduction of high-affinity GABA uptake. This suggested that cognin-mediated signaling was necessary for the normal developmental increase in GAD but not for high-affinity GABA uptake. These results contrasted with our previous observations on cholinergic differentiation in cultured retinal neurons. We found that cognin antibody blocked the normal developmental increase in choline acetyltransferase (ChAT) only if the cells were exposed before embryonic day 7. Thus, while both GAD and ChAT activity appear to be controlled by cell signaling involving cognin, the periods of developmental sensitivity for the two differentiation markers are different. Antibodies to other adhesion molecules, Ng-CAM, and N-cadherin, did not similarly affect GAD activity. Antibodies to laminin at a 10-fold higher concentration inhibited GAD activity only in early embryonic retina. Tests for protein synthesis and “housekeeping” enzyme activity demonstrated that the cognin antibody effect was selective for neuronal differentiation pathways. Thus, GABAergic differentiation in developing retina is sensitive to cell signaling mediated in part by cognin.  相似文献   
93.
94.
Four hundred eighty-three epileptic children attending the Pediatric Epilepsy Clinic at Bai Jerbai Wadia Hospital for Children, Bombay, India were classified according to the International League Against Epilepsy (ILAE) classification of epileptic seizures (1981) and epilepsies and epileptic syndromes (1989). The predominant seizures were partial (53.6), generalized (40.3%), and unclassifiable (6%). In epilepsies and epileptic syndromes, 55.3% were partial, 27% were generalized, 13.5% were undetermined, and 4.1% were special syndromes. Although our results were similar in many respects to those of other reported series, some differences were observed in the incidence of partial and generalized seizures, and partial and generalized epileptic syndromes and their subgroups, such as idiopathic, symptomatic, and cryptogenic partial syndromes, idiopathic generalized syndromes, and symptomatic specific syndromes. These differences are probably due to different age limits, methods of case ascertainment and inclusion criteria, different genetic and environmental factors, variable interpretation of clinical and EEG features, and lack of facilities for investigation in developing countries. Despite various limitations, we were able to classify most cases; the ILAE classification can be used in developing countries so that comparison can be made with other studies.  相似文献   
95.
A case of a giant right atrial diverticulum associated with neonatal supraventricular tachycardia is reported. The electrocardiogram in sinus rhythm showed pre-excitation that may have been caused by the right atrial diverticulum adhering to the right ventricle.  相似文献   
96.
97.
98.
99.
100.
We reviewed the records of 104 patients with Stage T1NO or Stage T2NO epidermoid carcinoma of the supraglottic larynx treated between 1965 and 1979. In 79 patients, surgery was the only type of initial treatment. These 79 patients are the subjects of this report. Forty-eight (61%) of these patients were treated by total laryngectomy, whereas 31 (39%) had a partial laryngectomy. An elective unilateral radical neck dissection was performed on 31 patients considered at high risk, but metastatic disease was found in the dissected side of the neck histologically in only 32% (ten of 31) of these patients. The minimum follow-up period was 5 years and the maximum was 20 years. Twenty-nine percent of the patients (23 of 79) experienced a neck relapse. The neck relapse rate was the same whether the patients did or did not have an elective radical neck dissection. Among the patients who experienced a neck relapse, 65% (15 of 32) have died of the cancer. Among those who did not experience a neck relapse, none (zero of 56) have died of the cancer (P less than 0.01). These results indicate that in surgically treated patients with early stage supraglottic larynx cancer, neck relapse was the major cause of failure associated with death from cancer. Strategies for decreasing the relapse rate are discussed.  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