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   1279241篇
  免费   92888篇
  国内免费   2010篇
耳鼻咽喉   18199篇
儿科学   42320篇
妇产科学   37859篇
基础医学   187432篇
口腔科学   35443篇
临床医学   108420篇
内科学   252014篇
皮肤病学   26536篇
神经病学   99425篇
特种医学   50058篇
外国民族医学   366篇
外科学   197867篇
综合类   26532篇
现状与发展   1篇
一般理论   300篇
预防医学   92813篇
眼科学   29096篇
药学   97903篇
  1篇
中国医学   2499篇
肿瘤学   69055篇
  2018年   11891篇
  2015年   11685篇
  2014年   16130篇
  2013年   24510篇
  2012年   33741篇
  2011年   36195篇
  2010年   21345篇
  2009年   20138篇
  2008年   35180篇
  2007年   38137篇
  2006年   38653篇
  2005年   37943篇
  2004年   36491篇
  2003年   35464篇
  2002年   34996篇
  2001年   58103篇
  2000年   59595篇
  1999年   50705篇
  1998年   14253篇
  1997年   12831篇
  1996年   13090篇
  1995年   12361篇
  1994年   11770篇
  1993年   10872篇
  1992年   40996篇
  1991年   40362篇
  1990年   39887篇
  1989年   38709篇
  1988年   36110篇
  1987年   35354篇
  1986年   33728篇
  1985年   32138篇
  1984年   23932篇
  1983年   20822篇
  1982年   12384篇
  1981年   10930篇
  1980年   10206篇
  1979年   22636篇
  1978年   15879篇
  1977年   13731篇
  1976年   12970篇
  1975年   14204篇
  1974年   16684篇
  1973年   16076篇
  1972年   15320篇
  1971年   14229篇
  1970年   13214篇
  1969年   12733篇
  1968年   11980篇
  1967年   10479篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Diffusely adhering Escherichia coli (E. coli) strains (DAEC) represent a potential cause of diarrhoea in infants, and the detection of type three secretion system (TTSS) genes in DAEC would substantiate their pathogenic nature. In this work, four isolates of DAEC, recovered from stools of diarrhoeic children, were analysed by PCR, in order to detect the presence of TTSS genes. Primers targeted to the escC, escJ, escN and escV, some of the most conserved TTSS genes in enteropathogenic and enterohaemorrhagic Escherichia coli (EPEC and EHEC), were used in order to verify the occurrence of homologous genes in our DAEC isolates. By this approach, we were able to characterise DNA fragments corresponding to putative escJ and escN genes in all DAEC isolates. Furthermore, DNA fragments homologous to the escC and escV genes were also amplified from all isolates. Besides the similarity found among the DAEC esc homologues with EPEC and EHEC esc genes, the nucleotide sequence analysis of the flanking regions of the amplified DNA fragments suggests that the putative DAEC esc genes are organised in the same manner as observed in EPEC and in EHEC strains. The results described here provide strong evidence for the presence of a TTSS in the DAEC strains analysed, implicating a pathogenic nature of these isolates.  相似文献   
113.
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   
114.
Various forms of signal processing are used in modern ASP hearing aids. The present study investigated the relationship between sentence recognition ability and two types of signal processing used in commercially available hearing aids. Results indicated a significant improvement in sentence recognition ability employing an instrument with adaptive compression (variable release time) versus an instrument with an adaptive high-pass filter with short attack and release times. Data were obtained for a single-talker competing message at several message-to-competition ratios. The adaptive compression system may prove to be beneficial to hearing-impaired listeners in certain background noise environments.  相似文献   
115.
116.
117.
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   
118.
We tested the urine of 30 infants 6 weeks to 7 months of age after they received standard 10-micrograms (0.5-ml) doses of HbOC (HibTITER) Haemophilus influenzae b (Hib) conjugate vaccine for the presence of Hib antigenuria using a commercially available latex particle agglutination assay (Directigen). Urines were collected within 1 hour, from 1 to 3 hours, at 24 hours and at 3, 6 and 9 days after vaccine administration and reactions were quantitated from 0 to 3+. In contrast to previous studies in older children which showed little or no antigenuria following HbOC vaccination, our study shows that in infants intense Hib antigenuria is evident within 2 to 3 hours and persists 3 days after vaccine administration and that less intense antigenuria may be detected in some infants for several days. With efficacious vaccines now being used in 2- to 6-month-old infants, invasive Hib disease may soon be limited to infants of this age just before their seroconversion. It should be recognized that antigenuria occurs for several days after vaccination with Hib conjugate vaccines and that it could be erroneously interpreted as evidence of invasive Hib infection.  相似文献   
119.
38 cases of acute multilocular osteomyelitis out of a total of 165 osteomyelitis patients were treated between 1974 and 1986 at the Department of Paediatric Surgery and Paediatric Diseases at the University of Mainz. Osteomyelitis in infants was separated from juvenile osteomyelitis because of the different problems inherent to this disease depending upon the age; likewise, multilocular remote involvement was separated from regional multiple involvement. It was found that distant involvement is of special importance in infancy. 6 of the 8 cases in this group presented with symmetrical involvement. This interesting phenomenon is described in this article for the first time in acute multilocular osteomyelitis; so far, it was known to occur only in chronic recurrent multifocal osteomyelitis (CRMO). The infants in this group were predominantly newborn who were particularly severely handicapped by predisposing factors such as necessary intensive-care measures or surgical interventions. Our findings showed that in this age group most of the problems occurred, namely: 3 deaths and 2 healing defects in 8 children. For this reason it is imperative to effect particularly close monitoring of multilocular acute osteomyelitis in infancy. This must be considered as a paediatric and paediatric-surgical emergency requiring not only accurate diagnostic measures but also early internistic and surgical treatment to improve the prognosis of this specific disease pattern.  相似文献   
120.
The Authors examine the correlation between hypertensive disorders of pregnancy and fetal growth. The results of a study of 342 pregnancies, confirm a significant correlation between hypertension and fetal growth retardation. These findings, so evident in moderate and severe hypertension, have also been confirmed in cases of mild hypertension. The medical treatment also in the pregnancies with mild hypertension, and a larger utilisation of operative deliveries, determined a decrease in perinatal mortality and morbidity.  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