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   195539篇
  免费   8929篇
  国内免费   519篇
耳鼻咽喉   2886篇
儿科学   6150篇
妇产科学   4806篇
基础医学   26884篇
口腔科学   6509篇
临床医学   12840篇
内科学   46821篇
皮肤病学   6397篇
神经病学   15944篇
特种医学   4586篇
外国民族医学   30篇
外科学   24485篇
综合类   1055篇
一般理论   49篇
预防医学   18635篇
眼科学   3961篇
药学   13458篇
中国医学   841篇
肿瘤学   8650篇
  2023年   1139篇
  2022年   1679篇
  2021年   4411篇
  2020年   2308篇
  2019年   4421篇
  2018年   6355篇
  2017年   3932篇
  2016年   3860篇
  2015年   4183篇
  2014年   5511篇
  2013年   8011篇
  2012年   12771篇
  2011年   13423篇
  2010年   7136篇
  2009年   5837篇
  2008年   10964篇
  2007年   11572篇
  2006年   10951篇
  2005年   10876篇
  2004年   9773篇
  2003年   9270篇
  2002年   8772篇
  2001年   5959篇
  2000年   6496篇
  1999年   5167篇
  1998年   1301篇
  1997年   950篇
  1996年   860篇
  1995年   739篇
  1994年   596篇
  1993年   563篇
  1992年   2280篇
  1991年   2079篇
  1990年   1875篇
  1989年   1621篇
  1988年   1438篇
  1987年   1387篇
  1986年   1315篇
  1985年   1188篇
  1984年   882篇
  1983年   749篇
  1979年   787篇
  1975年   599篇
  1974年   676篇
  1973年   728篇
  1972年   626篇
  1971年   626篇
  1970年   606篇
  1969年   596篇
  1968年   538篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
The degree of metabolic acidosis at birth has been calculated in cord artery and vein samples from 21 term fetuses with cord artery pH less than 7.20. The aim of the study was to compare base deficit values calculated from either Siggaard-Andersen alignment nomogram (BD blood) or the Acid-Base chart (BD extra cellular fluid, BDecf). BDblood was found to be consistently higher in the cord artery as compared with BDecf, 13.2 +/- 3.5 and 9.9 +/- 2.9 mmol/l (Mean +/- SD), respectively. A significant correlation was found between cord artery PCO2 and BDblood whereas BDecf appeared unaffected by PCO2. In cases with cord entanglement BDecf a-v differences were increased to 3.4 +/- 2.3 mmol/l as compared with the small a-v difference noted in acidotic cases without cord entanglement, 1.1 +/- 1.25 mmol/l. It is speculated that with acutely emerging, intermittent asphyxia due to cord compression, a cord artery and vein difference in metabolic acidosis may exist and where the vein captures the basal level and the artery the acute changes. It is concluded that BDecf in both cord artery and vein add valuable information on the mechanisms behind metabolic acidosis.  相似文献   
23.
24.
25.
The present authors investigated the excretion, distribution and pharmacokinetics of the novel potential antirheumatic agent flobufen and its active metabolite after p.o. and i.v. doses of 2, 10 and 50 mg/kg administered to rats. The drug is resorbed well from the digestive tract and mostly it is metabolized to the principal metabolite M, which is only slowly excreted from the organism mainly by renal clearance. Within the whole dose range the kinetics of the drug is linear. Binding of flobufen and M to proteins is high (95-99%). The highest concentrations of radioactive metabolites (mostly M) were found in the plasma, liver, lungs, kidneys, connective tissue and inflammatory foci. The penetration of metabolites through the placenta and excretion in human milk are relatively important.  相似文献   
26.
27.
28.
Melatonin, a pineal hormone, released photoperiodically, was administered systemically in rats, previously implanted with semimicroelectrodes into six different brain structures. The multiunit electrical activity of these structures was recorded for 10 min before and 60 min after melatonin administration in unanesthetized, freely moving rats. Different melatonin doses (100, 200, 500, and 1000 micrograms/kg) produced changes in the electrical activity of all tested structures. However, amygdala, rostral hypothalamus and mesencephalic reticular formation showed the most important changes. The main effect induced by melatonin was a dose-related decrease of the spontaneous electrical activity. The significance of these effects is discussed within the context of the behavioral and endocrinological effects of melatonin.  相似文献   
29.
BACKGROUND: The role of atopy in the evolution to chronic obstructive disease remains controversial. AIM: We aimed to assess the association between individual sensitization to common allergens and lung function. METHOD: We analysed data from 12,687 subjects aged 20 to 44 years, from 34 centres in 15 countries participating in the European Community Respiratory Health Survey (ECRHS). Participants performed a blood test, lung function test, methacholine challenge, and answered an administered questionnaire. The relationships between specific IgE, FEV1 and FEV1/FVC ratio were assessed for each study centre stratified by sex, followed by random effects meta-analysis. RESULTS: Asthmatics sensitized to house dust mite had a lower FEV1 (-119 mL in women and -112 mL in men) and FEV1/FVC ratio (-1.95%, and -2.48%) than asthmatics without sensitization. Asthmatics sensitized to cat had a lower FEV1 (statistically significant for women only) and a lower FEV1/FVC ratio. Asthmatic women sensitized to grass had a lower FEV1 and a lower ratio, and those sensitized to Cladosporium had a lower FEV1. A weak association was found with sensitization to cat and to Cladosporium among non-asthmatic women, which disappeared after adjusting for BHR. CONCLUSION: We conclude that atopy was related to a lower lung function, which was only apparent among asthmatics. This relationship was explained by specific sensitization to cat and to house dust mite, the latter being homogeneous across areas.  相似文献   
30.
Intracerebroventricular (ICV) microinfusion of recombinant human interleukin-1 beta (rhIL-1 beta, 0.125 to 2.0 ng/rat) dose-dependently suppressed 2 h and nighttime food intake in rats. The following daytime food intake did not change or increased. ICV infusion of bovine serum albumin (BSA), or heat-treated rhIL-1 beta had no effect on food intake. Pretreatment with dexamethasone (200 micrograms/rat, intraperitoneal) blocked the food intake suppression induced by low doses of rhIL-1 beta. This ability of dexamethasone, a synthetic corticosteroid, may have potential therapeutic implications in acute and chronic pathological processes associated with increased levels of IL-1 and appetite suppression.  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