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   2350509篇
  免费   171665篇
  国内免费   3332篇
耳鼻咽喉   32061篇
儿科学   75894篇
妇产科学   62709篇
基础医学   348249篇
口腔科学   63644篇
临床医学   211407篇
内科学   457473篇
皮肤病学   51762篇
神经病学   185370篇
特种医学   88039篇
外国民族医学   489篇
外科学   353928篇
综合类   47516篇
现状与发展   12篇
一般理论   851篇
预防医学   182810篇
眼科学   54330篇
药学   175130篇
  11篇
中国医学   4575篇
肿瘤学   129246篇
  2021年   18994篇
  2019年   19551篇
  2018年   27069篇
  2017年   20365篇
  2016年   22757篇
  2015年   25650篇
  2014年   36106篇
  2013年   53985篇
  2012年   74723篇
  2011年   79457篇
  2010年   47077篇
  2009年   44585篇
  2008年   74656篇
  2007年   79510篇
  2006年   80341篇
  2005年   77818篇
  2004年   74410篇
  2003年   71730篇
  2002年   69402篇
  2001年   108778篇
  2000年   111481篇
  1999年   93526篇
  1998年   26998篇
  1997年   23662篇
  1996年   24060篇
  1995年   22720篇
  1994年   20898篇
  1993年   19714篇
  1992年   72013篇
  1991年   70079篇
  1990年   68400篇
  1989年   65671篇
  1988年   60304篇
  1987年   59132篇
  1986年   55222篇
  1985年   53006篇
  1984年   39313篇
  1983年   33400篇
  1982年   19860篇
  1979年   35869篇
  1978年   25653篇
  1977年   21230篇
  1976年   20333篇
  1975年   21818篇
  1974年   26149篇
  1973年   24805篇
  1972年   23206篇
  1971年   22040篇
  1970年   20248篇
  1969年   19318篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
982.
983.
The value of maternal C-reactive protein (CRP) levels as predictors of fetal and maternal infective morbidity and fetal mortality was assessed prospectively over a 6-month period in all cases of premature rupture of the fetal membranes or suspected premature labour. Statistical analysis of results showed that CRP at a level of 1.32 mg/dl is a sensitive marker of infective morbidity in mother and neonate. Furthermore, there was a significant association between raised CRP levels and low-birth-weight babies, suggesting that intra-uterine infection is a major cause of prematurity in the study population.  相似文献   
984.
Transport of 45Ca from the lumen to the venous effluent was studied in duodena of normal, vitamin D3-replete (+D) chicks perfused through the celiac artery with 130 pM 1,25(OH)2D3 or vehicle. Administration of actinomycin D 3 h prior to perfusion did not alter the unstimulated transport rate or diminish the response to exogenous 1,25(OH)2D3: After 40 min exposure to the seco-steroid, 45Ca in the vascular effluent was 140% of control levels. The anti-microfilament agent cytochalasin b and the ionophore monensin, an inhibitor of Golgi function, similarly failed to suppress 1,25(OH)2D3-stimulated calcium transport. In pilot studies, Golgi and basal-lateral membrane fractions were prepared from duodenal epithelium of vitamin D-deficient (-D) chicks treated with vehicle or 650 pmol of 1,25(OH)2D3 in vivo 2 h, 10 h, or 15 h before sacrifice, as well as from +D birds. Analyses of Golgi fractions for cathepsin B (CB) activity revealed a biphasic response with time, increasing to 200% of -D levels 2 h after 1,25(OH)2D3 administration and in equivalent preparations from +D birds. Less pronounced increases in acid phosphatase activity were observed in the same membrane fractions. In basal-lateral membranes, enhanced CB activity was detectable 10 h after 1,25(OH)2D3 in vivo, rose to 155% of -D levels at 15 h, and to 245% of controls in fractions from +D birds, whereas acid phosphatase was 75%, 81%, and 125% of controls, respectively, at these times.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
985.
986.
A study of intravenous (i.v.) cannula usage for medical emergencies admitted to hospitals in the Newham Health District was undertaken during two defined periods (24 and 35 days). Almost half the cannulas inserted (47%) were not flushed following an initial bolus injection of heparinized saline. The duration that cannulas remained in a vein ranged from 24 hours to 8 days (median 2 days) and inflammation around the cannula site was related to the length of time since insertion but unrelated to whether the cannula was flushed regularly or to the type of fluid used. Our findings indicate a substantial wastage of i.v. cannulas due to difficulties with insertion and suggest that isotonic saline, without heparin, is effective in maintaining cannula patency for 48 hours. It is concluded that these findings are not unique to the Newham Health District and worthwhile financial savings should be achieved throughout the NHS if clinicians reconsider the indications and use of i.v. cannulas for their patients.  相似文献   
987.
M.A. Sabbahi  E.M. Sedgwick   《Brain research》1987,423(1-2):125-134
The H-reflex of 120 soleus motoneurons was recorded using fibre EMG. The recovery profile of these motoneurons was studied during monitoring surface H-reflex records in 28 adult subjects. The spectrum of motoneurons tested was homogeneous with two extremes of neurons having different characteristics. A motoneuron population (forming about 69% of our sample) had a high threshold level for electrical stimuli, short recovery time, and short recovery fringe time (called type A). A second population of motoneurons (forming about 20-30% of our sample) had a low threshold level for electrical stimuli, long recovery fringe time (called type B). During an isometric muscle contraction every motoneuron showed an early shift in recovery time (i.e. each had a shorter recovery time) with shortened recovery fringe time. These changes were larger for motoneurons type B than motoneurons type A. With paired identical electrical stimuli of varying interstimulus intervals a motoneuron may fire in response to the conditioning and test stimuli giving an H2, but not in response to both stimuli. This occurred for interstimulus intervals of 4-11 ms. A strong inhibition period was recorded with interstimulus intervals of 12-80 ms in which all motoneurons did not show any recovery. Most motoneurons recovered in orderly fashion between 80 and 300 ms of interstimulus interval, and this recovery coincided with the fast recovery recorded in surface H-reflex. All motoneurons were recovered by 3000 ms of interstimulus intervals. These findings emphasize the importance of eliciting the H-reflex every 3-5 s in H-reflex methodology in order to be assured that all excited motoneurons have been recovered.  相似文献   
988.
989.
Two hundred and thirty pregnancies were studied in 196 diabetic women. Seven women with babies found to have major malformations had a higher median first trimester haemoglobin A1 (12.9%) than the median HbA1 (10.8%) in those with normal babies (p = 0.06). No relationship was found between the occurrence of minor malformations and first trimester maternal haemoglobin A1. Two of the seven congenital malformations were diagnosed antenatally at a time when therapeutic abortion could be offered. Expert antenatal ultrasound scanning should be offered to all pregnant diabetic women as poor glycaemic control at the time of conception and organogenesis, as evidenced by raised first trimester HbA1, predisposes to congenital malformation.  相似文献   
990.
This paper gives the historical sketch necessary for an understanding of the current state of American psychiatry. It reviews some of the reasons why the rendering of good hospital care must be reconsidered, and describes some of the main features of the future public institution.  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