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   131695篇
  免费   7549篇
  国内免费   1125篇
耳鼻咽喉   2050篇
儿科学   1981篇
妇产科学   1913篇
基础医学   20968篇
口腔科学   3152篇
临床医学   12227篇
内科学   23523篇
皮肤病学   4207篇
神经病学   10591篇
特种医学   7570篇
外科学   17242篇
综合类   559篇
现状与发展   3篇
一般理论   28篇
预防医学   6949篇
眼科学   3367篇
药学   11996篇
中国医学   1514篇
肿瘤学   10529篇
  2023年   926篇
  2022年   2822篇
  2021年   4535篇
  2020年   2198篇
  2019年   3065篇
  2018年   3833篇
  2017年   3121篇
  2016年   4080篇
  2015年   5679篇
  2014年   6709篇
  2013年   7856篇
  2012年   11705篇
  2011年   11192篇
  2010年   6485篇
  2009年   5535篇
  2008年   7828篇
  2007年   7423篇
  2006年   6680篇
  2005年   6207篇
  2004年   5394篇
  2003年   4713篇
  2002年   4044篇
  2001年   3081篇
  2000年   2833篇
  1999年   2165篇
  1998年   931篇
  1997年   690篇
  1996年   524篇
  1995年   462篇
  1994年   403篇
  1993年   343篇
  1992年   764篇
  1991年   711篇
  1990年   648篇
  1989年   574篇
  1988年   474篇
  1987年   477篇
  1986年   345篇
  1985年   385篇
  1984年   270篇
  1983年   200篇
  1982年   133篇
  1981年   177篇
  1980年   130篇
  1979年   227篇
  1978年   167篇
  1977年   121篇
  1976年   132篇
  1975年   123篇
  1974年   140篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
Conversion of vinylogous glycidic ester1 to2 by a stereoselective acyclic allylic epoxidation will be presented  相似文献   
993.
1. The present study analysed the clinical course, the serial angiograms and the CT scans of the patients with angiographic arterial occlusion following vasospasm after subarachnoid hemorrhage. The occlusion was observed in 6 out of 84 patients with vasospasm. 2. The angiograms which showed this phenomenon were obtained between the 11th and the 30th day of the illness. The affected vessels were the branches of middle cerebral artery. 3. Thrombus formed on the intima which had been injured by vasospasm is suspected to be a genesis of this arterial occlusion. The pathological findings of a case in this series support this concept. 4. The surgical procedure during the direct aneurysmal operation performed in the period of "smooth narrowing" seems to be a contributing factor to the arterial occlusion. There was no correlation between antifibrinolytic therapy and this phenomenon except in one case. 5. Fibrinolytic therapy after clipping of aneurysm may be a treatment of choice for this arterial occlusion following vasospasm.  相似文献   
994.
995.
Kim DE  Lee SH  Park KI  Chang KH  Roh JK 《Archives of neurology》2000,57(12):1770-1772
BACKGROUND: Encephalomyelitis with prominent focal neurologic signs and associated neuroradiologic abnormalities has not been previously described in scrub typhus. CASE DESCRIPTION: A 22-year-old woman was admitted because of fever and an altered mental state. Neurologic examination revealed bilateral sixth and seventh nerve palsies, bilateral gaze evoked nystagmus, anarthria, dysphagia, quadriparesis, and sensory level at T1. Serum and cerebrospinal fluid samples were positive for tsutsugamushi antibody. The patient's magnetic resonance images demonstrated the lesions responsible for the neurologic dysfunctions: in the lower brainstem, cerebellar peduncles, and spinal cord. It was interesting that the gray matter of the spinal cord was predominantly involved. CONCLUSIONS: The recognition of unusual manifestations and the clinical suspicion of this treatment-responsive disease may be important, particularly in the face of increasing international and intranational travel.  相似文献   
996.
997.
In this study we investigated the extent and time course of neuronal cell death and the regulation of the proliferating cell nuclear antigen (PCNA) in the different retinal cell layers following ischemia-reperfusion injury. Retinal ischemia was induced by controlled elevation of the intraocular pressure for a duration of 60 min. Changes in thickness and cell numbers in the retinal cell layers were analyzed at various time points (1 h to 4 weeks) after reperfusion. In parallel, apoptotic cell death was determined by the TUNEL method and the expression of PCNA analyzed by immunocytochemistry. In addition, we tested whether PCNA is expressed in neurons by double immunocytochemistry. The reduction in thickness was found to be less pronounced in the inner nuclear layer (INL). Correspondingly, cell numbers decreased by only 33% in the inner retina, but by more than 80% in the outer nuclear layer (ONL). Alterations in glial cell numbers did not contribute significantly to postischemic changes in the INL and ONL as assessed by using immunocytochemical markers for microglial and Müller cells. The time course of cell death determined by the TUNEL technique also differed markedly in the retinal layers being rapid and transient in the inner retina but delayed and prolonged in the ONL. PCNA immunoreactivity was undetectable in the normal retina, but was specifically induced in neurons of the inner retina within 1 h after reperfusion and was sustained for at least 4 weeks. We conclude that in contrast to photoreceptors in the ONL, a significant proportion of inner retinal neurons is resistant to ischemic insult induced by transiently increased intraocular pressure and that PCNA may possibly play a role in the selective postischemic survival of these cells.  相似文献   
998.
Won JS  Song DK  Huh SO  Kim YH  Suh HW 《Hippocampus》2000,10(3):236-243
The in vivo short-term effect of melatonin on kainic acid (KA)-induced proenkephalin (proENK) or prodynorphin (proDYN) mRNA, and on AP-1 protein levels in the rat hippocampus, were studied. Melatonin (5 mg/kg) or saline was administered intraperitoneally (i.p.) to rats 30 min prior to and immediately after i.p. injection of KA (10 mg/kg). Rats were sacrificed 1 and 3 h after KA injection. The proENK and proDYN mRNA levels were significantly increased 3 h after KA administration. The elevations of both proENK and proDYN mRNA levels induced by KA were significantly inhibited by the preadministration with melatonin. The increases of proENK and proDYN mRNA levels induced by KA were well-correlated with the increases of c-Fos, Fra-2, FosB, c-Jun, and JunB protein levels, which were significantly increased 3 h after KA administration and effectively inhibited by administration with melatonin. In an electrophoretic mobility shift assay, both AP-1 and ENKCRE-2 DNA binding activities were increased by KA, which were also attenuated by the administration of melatonin. In addition, cross-competition studies revealed that AP-1 or ENKCRE-2 DNA binding activity was effectively reduced by the 50x unlabeled cross-competitor. Therefore, these data suggest that melatonin has an inhibitory role in KA-induced gene expression, such as proENK and proDYN mRNA expression, and this may be due to a reduction of KA-induced AP-1 or ENKCRE-2 DNA binding activity.  相似文献   
999.
Effects of small dose of brotizolam on P300   总被引:1,自引:0,他引:1  
Nine healthy men (mean age, 22.2 years) participated in two experimental sessions cross-overed randomly in a double blind manner; one with a placebo and the other with 0.125 mg of brotizolam (BTZ) administered in the morning. Resting electroencephalogram and event-related potential under oddball paradigm was recorded before and 1, 2, 4, 6 and 8 h after the administration. Mean 30-msec bin amplitude from 240 msec to 450 msec after the stimulus was compared between placebo and drug sessions in order to observe P300. Brotizolam reduced the amplitude of P300 at 6 h after administration. It was noted that the effects of BTZ were most marked at Fz.  相似文献   
1000.
Histoclinical Analysis of Early Colorectal Cancer   总被引:5,自引:0,他引:5  
To evaluate the clinicopathologic characteristics of early colorectal cancer (ECC), histopathologic and clinical features of 90 ECC patients who underwent surgical resection (not including the endoscopic polypectomized cases) and 1704 patients with advanced colorectal cancer were analyzed. Smaller size, better histologic differentiation, less lymph node (LN) metastasis, and better clinical outcome were observed in those with ECC than in patients with more advanced lesions. LN metastasis was found in 5 patients with ECC among the 56 patients who underwent bowel resection (8.9%). Tumors with LN metastasis were more frequently associated with deep submucosal invasion, absence of an adenomatous component within the tumor, sessile configuration, and lymphovascular invasion. Tumors showing deep submucosal layer invasion were associated with a more unfavorable histologic grade, lymphovascular invasion, LN metastasis, sessile morphology, and absence of an adenomatous component within the tumor. Recurrence was observed in two patients who underwent local excision for their submucosal cancer. One of the patients was salvaged after bowel resection, but one patient died of distant metastasis. From our data analysis and literature review, extensive submucosal invasion, lymphovascular invasion, sessile configuration, and tumors with no adenomatous component should be considered high risk factors for LN metastasis and recurrence after limited therapy.  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