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   1397091篇
  免费   103806篇
  国内免费   2102篇
耳鼻咽喉   20437篇
儿科学   48569篇
妇产科学   37783篇
基础医学   199934篇
口腔科学   37643篇
临床医学   121260篇
内科学   279404篇
皮肤病学   31518篇
神经病学   112479篇
特种医学   56376篇
外国民族医学   660篇
外科学   214035篇
综合类   27624篇
现状与发展   1篇
一般理论   412篇
预防医学   102301篇
眼科学   30610篇
药学   102871篇
  3篇
中国医学   2601篇
肿瘤学   76478篇
  2019年   10321篇
  2018年   15715篇
  2017年   12178篇
  2016年   13744篇
  2015年   14849篇
  2014年   19814篇
  2013年   31031篇
  2012年   42157篇
  2011年   45066篇
  2010年   26783篇
  2009年   24454篇
  2008年   43724篇
  2007年   46692篇
  2006年   46678篇
  2005年   45520篇
  2004年   44261篇
  2003年   43117篇
  2002年   42352篇
  2001年   67843篇
  2000年   71413篇
  1999年   59229篇
  1998年   16399篇
  1997年   14778篇
  1996年   15023篇
  1995年   14125篇
  1994年   13430篇
  1993年   12422篇
  1992年   45118篇
  1991年   43969篇
  1990年   42680篇
  1989年   40642篇
  1988年   37339篇
  1987年   36739篇
  1986年   34023篇
  1985年   32862篇
  1984年   24699篇
  1983年   20754篇
  1982年   12245篇
  1981年   11174篇
  1979年   21726篇
  1978年   15231篇
  1977年   12948篇
  1976年   12043篇
  1975年   12980篇
  1974年   14991篇
  1973年   14397篇
  1972年   13161篇
  1971年   11968篇
  1970年   11269篇
  1969年   10210篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
In order to study the involvement of NMDA-receptor activation in brain development, rat pups were chronically treated with the non-competitive NMDA antagonist MK-801 during the neonatal period. We recorded the cortical EEG at various vigilance states throughout the treatment period. Spectral analysis of the EEG showed reduced power in the delta (delta) frequency range (1.5-4 Hz) during quiet sleep and less power in the theta (theta) range (4-7 Hz) during REM-sleep in MK-801 animals than in controls. No significant differences were found for the total time spent in each of the different vigilance states. We conclude that chronic MK-801 treatment probably causes a developmental retardation in state-related brain activities.  相似文献   
162.
A total of 102 patients were examined, 32 of these with true eczema, 38 with exudative mycosis of the soles, and 32 with eczema etiologically related to a fungal infection. Analysis of the immune and biochemical reactions in the examinees has shown a marked reduction of adenyl nucleotides in the leukocytic suspension and neutrophils of patients with a mycotic infection as against those with true eczema. The lowest creatine phosphate levels were detected in the leukocytic suspension and neutrophils of the patients suffering from eczema etiologically related to mycosis and exudative mycosis of the soles. These results give grounds to search for effective corrective therapy.  相似文献   
163.
This paper reports the changes in prolactin levels after 12 spontaneous and 52 induced pregnancies in 54 women with unambiguous hyperprolactinaemia (median plasma prolactin levels 67.5 ng/ml, range 40-400). Twenty-three of the patients showed radiological evidence of prolactinoma. The pregnancies were induced in 37 patients by bromocriptine, in nine by metergoline, in two by lisuride and in four by other treatments. Of the 64 pregnancies, 16 ended in spontaneous abortion, while 48 went to term. Follow-up was continued for at least 6 months after delivery or until the end of lactation. In a control group of 32 hyperprolactinaemic women (median prolactin 70 ng/ml, range 40-400) not wishing to become pregnant, prolactin changes were similarly registered over a mean period of 15 months without any treatment (range 6-38 months). After pregnancy, a significant downward trend of plasma prolactin was observed in the puerperal women with a 'normalization' rate of 17%. No changes were observed in the 32 controls who did not become pregnant.  相似文献   
164.
165.
The authors analysed the prevalence of atrioventricular conduction defects and sinus node dysfunction by Holter monitoring in three population groups with similar clinical characteristics: 50 controls (Group I), 17 physically fit subjects with an atrioventricular conduction defect on the resting ECG which was usually asymptomatic (Group II), and 48 professional pilots who were also physically fit but who had no conduction defects on resting ECG (Group III). The 24 hour recordings showed: --a similar incidence of sinus dysrhythmias and atrioventricular conduction defects in the three groups although the frequency of low degree block was a little higher in sportsmen; --a preponderance of the association of first degree block and nocturnal Luciani-Wenckebach periods, sometimes with episodes of Mobitz II block; --the absence of progression to high-degree atrioventricular block. Holter monitoring would therefore seem to be a good method of detecting and following up abnormalities of sinus node function and atrioventricular conduction defects in asymptomatic patients. In addition, it gives a qualitative and quantitative assessment of the recorded changes and provides a means of monitoring their evolution.  相似文献   
166.
Thiarubrine A, a dithiacyclohexadiene polyine from the roots of Chaenactis douglasii, and a related dithiacyclohexadiene from Rudbeckia hirta exhibit strong light-independent antibacterial and antifungal activity. This activity is enhanced by exposure to visible light. Visible light also converts the compounds to the corresponding thiophenes. These are antibiotic only when irradiated with UV-A. Dithiacyclohexadienes are the first polyines to exhibit such complex mechanisms of toxicity towards microorganisms.  相似文献   
167.
The administration of prophylactic antibiotics in surgery is appropriate for many patients. Data have shown extending the duration of prophylaxis beyond 48 hours does not lower the rate of postoperative-infection. The purpose of this project was to concurrently assess the duration of prophylactic antibiotic use. A total of 95 patients were monitored over 3 weeks. Eighty patients (84.2%) received antimicrobial therapy. In 23 of these patients (28.75%) the duration of antibiotic administration was longer than 2 days without clinical or microbiological evidence of infection. In 5 other patients only postoperative antibiotics were prescribed. The cost difference between the actual duration of antibiotic administration and 2 days of the same regimen was +1,364.58. Extrapolating for one year, it can be estimated that antibiotic costs could be reduced about +23,600. Pharmacists can focus on the duration of antibiotic prophylaxis as a cost containment measure.  相似文献   
168.
The percentage uptake of [123I]metaiodobenzylguanidine (MIBG) by tumors of the paraganglion system is compared with the number of neurosecretory granules (assessed by both light and electron microscopy) in the subsequently resected tumors in six patients. Iodine-123 MIBG was injected intravenously; the tumor uptake of [123I]MIBG varied between 0.001% and 0.14% of the injected dose per gram of tumor tissue at 22 hr. The number of neurosecretory granules in tissue sections was scored on a scale of I-III. A direct proportional correlation was found between the percentage uptake of [123I]MIBG by the tumor and the number of neurosecretory granules in the tissue sections but not with plasma or urinary catecholamines. This technique for imaging reflects the storage status of the tumor better than plasma and urinary catecholamine measurements.  相似文献   
169.
170.
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