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   659873篇
  免费   40577篇
  国内免费   739篇
耳鼻咽喉   9327篇
儿科学   21940篇
妇产科学   17068篇
基础医学   106714篇
口腔科学   19766篇
临床医学   56552篇
内科学   119630篇
皮肤病学   16140篇
神经病学   51091篇
特种医学   24618篇
外国民族医学   63篇
外科学   99186篇
综合类   9120篇
一般理论   156篇
预防医学   47171篇
眼科学   15272篇
药学   50468篇
中国医学   1216篇
肿瘤学   35691篇
  2019年   5020篇
  2018年   7916篇
  2017年   6214篇
  2016年   7360篇
  2015年   7418篇
  2014年   9323篇
  2013年   15179篇
  2012年   19979篇
  2011年   22236篇
  2010年   12903篇
  2009年   11175篇
  2008年   21641篇
  2007年   23102篇
  2006年   23094篇
  2005年   22519篇
  2004年   21622篇
  2003年   21003篇
  2002年   20736篇
  2001年   29144篇
  2000年   31278篇
  1999年   24359篇
  1998年   7062篇
  1997年   6051篇
  1996年   6114篇
  1995年   5572篇
  1994年   5211篇
  1992年   16966篇
  1991年   17427篇
  1990年   17556篇
  1989年   16951篇
  1988年   15602篇
  1987年   15511篇
  1986年   14525篇
  1985年   14037篇
  1984年   10593篇
  1983年   9056篇
  1982年   5259篇
  1979年   10143篇
  1978年   7472篇
  1977年   6373篇
  1976年   6134篇
  1975年   6969篇
  1974年   8215篇
  1973年   7626篇
  1972年   7401篇
  1971年   7130篇
  1970年   6597篇
  1969年   6242篇
  1968年   5929篇
  1967年   5387篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Exposure to cadmium via the diet is known to depend to a large extent on the intake of cereal grains, particularly the high-fibre fractions of wheat. Subjects with low iron status absorb more cadmium than those with better iron status. The purpose of the present study was to determine to what extent cadmium accumulation in human placenta is affected by the intake of grain fibre and maternal iron status during pregnancy. Thirty-nine pregnant women participated in the study. In each trimester the women were requested to complete a dietary history and to allow blood samples to be taken for haemoglobin, serum ferritin and serum thiocyanate determinations, the latter as a marker for smoking. At delivery the whole placenta was taken for the determination of the cadmium concentration. The 32 women who had serum thiocyanate levels less than 70 mumol/l, who had completed at least one dietary history and from whom a blood sample was obtained in the third trimester, were included in the final statistical analyses. In the group of women who consumed less than the median intake of grain fibre and had more than 15 micrograms ferritin/l serum in the third trimester, the placenta cadmium concentration was nearly half that in the placentae of women who had consumed more grain fibre or had lower iron status in late pregnancy.  相似文献   
72.
This paper examines the effect of patient age, tumour grade and extent of surgery on the outcome of treatment of 278 patients with high grade malignant gliomas referred to the Queensland Radium Institute between 1980 and 1987. The aim was to determine whether the extent of surgical resection alters survival rates. The extent of surgery had no effect on survival except for those patients with grade 3 tumours in whom a total excision was possible. Those in whom only a biopsy was done did not have a worse prognosis. Grading was found to be of importance, as patients with grade 3 tumours had a better survival than those with grade 4 tumours. In grade 4 tumours, those under 30 years of age had a better survival than those over 30 years, whereas with grade 3 tumours there was a gradation of age effect (under 40 years best, then 40–49 years, and those 50 years and over doing worst).  相似文献   
73.
74.
75.
76.
77.
Three hundred and twenty samples of subgingival plaque were obtained from 80 caucasian girls, ranging from 10 to 13 years of age. The samples were analyzed to verify the influence of age upon colonization of the gingival sulcus by microorganisms potentially pathogenic to the periodontal tissues. The gingival and plaque status were evaluated through the gingival index (GI) and plaque index (PlI) and the microflora was assessed by the enzymatic method benzoyl-arginine-naphthylamide (BANA). The results of the BANA test were positive for 62.50% of the tested individuals and 40% of the examined sites. The influence of age was statistically significant on BANA reactivity, and the number of positive sites was greater at 11 (57.5%) than at 12 years (28.8%).  相似文献   
78.
79.
80.
Variations of the medial and inferior choanal limits may facilitate snoring. These are: 1) short vomer without crista choanalis vomeris and adaptational formations, 2) extremely concave posterior margin of the hard palate leading to disproportion between the muscular and aponeurotic part of m. tensor veli palatini and hence to a flabby soft palate especially during sleep, and 3) neonatal relation of the height and width of the choane resulting in a very large choanal region instead of relative reduction of choanal width compared to its increasing height. All these variations result in a flabby soft palate especially during sleep and may lead to formation of whirles of inspired air and snoring.  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