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   759篇
  免费   70篇
  国内免费   7篇
耳鼻咽喉   5篇
儿科学   30篇
妇产科学   5篇
基础医学   87篇
口腔科学   33篇
临床医学   64篇
内科学   207篇
皮肤病学   37篇
神经病学   14篇
特种医学   105篇
外科学   72篇
综合类   33篇
预防医学   58篇
眼科学   4篇
药学   57篇
中国医学   1篇
肿瘤学   24篇
  2021年   16篇
  2020年   4篇
  2018年   8篇
  2017年   4篇
  2016年   13篇
  2015年   11篇
  2014年   13篇
  2013年   32篇
  2012年   30篇
  2011年   18篇
  2010年   30篇
  2009年   26篇
  2008年   23篇
  2007年   24篇
  2006年   30篇
  2005年   22篇
  2004年   23篇
  2003年   20篇
  2002年   26篇
  2001年   20篇
  2000年   20篇
  1999年   26篇
  1998年   37篇
  1997年   28篇
  1996年   24篇
  1995年   15篇
  1994年   29篇
  1993年   29篇
  1992年   16篇
  1991年   18篇
  1990年   14篇
  1989年   19篇
  1988年   20篇
  1987年   13篇
  1986年   14篇
  1985年   9篇
  1984年   8篇
  1983年   7篇
  1982年   9篇
  1981年   13篇
  1980年   12篇
  1979年   3篇
  1978年   4篇
  1977年   6篇
  1976年   9篇
  1975年   4篇
  1936年   6篇
  1935年   4篇
  1933年   4篇
  1932年   3篇
排序方式: 共有836条查询结果,搜索用时 46 毫秒
1.
OBJECTIVE: Nocturnal enuresis is a common pediatric problem, the etiology of which is unclear. In recent years, various studies have been published stating that children with nocturnal enuresis exhibit growth and skeletal maturation retardation. METHODS: In this cross-sectional study, we included 27 patients (16 boys, 11 girls) between the ages of 6 and 14 years who had presented with primary nocturnal enuresis (PNE) complaints. We included in the evaluation 19 healthy subjects (12 boys, 7 girls), who were the siblings of the children with PNE, as the control group. RESULTS: The patients in both groups were similar in chronological age, bone age, height and weight, with no significant difference between groups (P>0.05). CONCLUSION: The two groups in our study consisted of the same genetic background. Thus, our results were found to be different from the previous studies. We have concluded that there is no direct relationship between enuresis nocturnal and skeletal maturation.  相似文献   
2.
3.
4.
5.
6.
High serum fluoride (F-) in patients with chronic renal failure (CRF) and end-stage renal disease (ESRD) is associated with risk of renal osteodystrophy and other bone changes. This study was done to determine F- in normal healthy controls and patients with ESRD on haemodialysis (HD) or peritoneal dialysis (PD). Seventeen healthy controls (12 males, 5 females) and 39 ESRD patients on dialysis (17 males, 22 females) were recruited in the study in a community with 47.4 +/- 3.28 microM/l (range 44-51 microM/l) of F- content in drinking water. Control subjects showed a mean serum F- concentration of 1.08 +/- 0.350 microM/l. Males in control group showed slightly higher F- levels (1.15 +/- 0.334, range 0.55-1.9 microM/l) than females (0.92 +/- 0.370, range 0.6-1.5 microM/l). Mean serum F- concentration did not correlate significantly with age and sex among control subjects, whereas such correlation was observed in patients with ESRD on dialysis. Mean serum F- concentration was significantly higher in patients on dialysis (2.67 +/- 1.09, range 0.8-5.2 microM/l) than normal controls. When grouped according to sex, the mean serum F- concentration in males (3.05 +/- 1.04, range 1.8-5.2 microM/l) was significantly higher than females (2.38 +/- 1.08, range 0.8-5.2 microM/l). When patients were grouped according to age, it was observed that F- concentration was significantly higher in patients with age groups 21-70 (2.86 +/- 1.05) than those with age group 13-20 years (1.42 +/- 0.531). Thus F- concentration correlated with age and sex, being higher in males and above 20 years. Despite appreciable clearance of F- (39-90%) across the peritoneum, patients on CAPD showed higher serum F- concentration than those on HD (3.1 +/- 1.97 vs 2.5 +/- 1.137 microM/l). Of the total 39 patients on dialysis 39% had their serum F- concentration above 3.0 microM/l, posing the risk of renal osteodystrophy.   相似文献   
7.
Pre-clerking of all patients undergoing elective general surgical operations was introduced at our hospital in an attempt to reduce an unacceptably high operation cancellation rate. A prospective audit has been performed on the effect of this policy on the cancellation rate. Before the introduction of pre-clerking there was a marked seasonal variation in the number of patients who failed to attend for surgery, which could be explained by absence on holiday. This seasonal variation disappeared after the start of pre-clerking clinics, but there has been no reduction in the number of cancellations for medical reasons.  相似文献   
8.
OBJECTIVE: To determine whether there is an association between prenatal ultrasound exposure and delayed speech in children. DESIGN: Case-control study. SETTING: Network of community physicians affiliated with the Primary Care Research Unit, University of Calgary. SUBJECTS: Thirty-four practitioners identified 72 children aged 24 to 100 months who had undergone a formal speech-language evaluation and were found to have delayed speech of unknown cause by a speech-language pathologist. For each case subject the practitioners found two control subjects matched for sex, date of birth, sibling birth order and associated health problems. MAIN OUTCOME MEASURES: Rates of prenatal ultrasound exposure and delayed speech. RESULTS: The children with delayed speech had a higher rate of ultrasound exposure than the control subjects. The findings suggest that a child with delayed speech is about twice as likely as a child without delayed speech to have been exposed to prenatal ultrasound waves (odds ratio 2.8, 95% confidence limit 1.5 to 5.3; p = 0.001). CONCLUSION: An association between prenatal ultrasonography exposure and delayed speech was found. If there is no obvious clinical indication for diagnostic in-utero ultrasonography, physicians might be wise to caution their patients about the vulnerability of the fetus to noxious agents.  相似文献   
9.
1. The temperature-dependence of the uptake of 24Na and 42K into dog red cells between 38 and 4 degrees C has been investigated. The effects on the cation fluxes of partial dehydration of the cells in hyperosmolar sucrose (50-125 mM) have also been studied. 2. A Hamilton gas-tight syringe was used to pipette accurately reproducible volumes of packed cells which contained in addition to 24Na or 42K either [131I]albumin or [51Cr]EDTA as extracellular markers. 3. At 38 degrees C Na flux (m-equiv/l. isosmolar cell volume. hr) increased from 2-8 +/- 0-1 (n = 8) in cells of normal volume to 226 +/- 8 (n = 8) when the cells were shrunken by 27-4 +/- 0-6% (n = 8) in media containing sucrose (100 mM). K influx remained relatively constant under these conditions. 4. The exchange of 24Na in shrunken cells followed a single exponential time course but about 9% of the intracellular Na apparently did not exchange with 24Na in the bathing medium. 5. The steady-state influx of Na in cells of normal volume was maximal at about 22 degrees C. The temperature dependence of the Na fluxes in shrunken cells was described by an Arrhenius relationship with a change in slope at about 22 degrees C. 6. The K influx in cells of normal volume decreased as the temperature was lowered from 38 degrees C, to about 12 degrees C, at which temperature the flux was at a well defined minimum. Above 12 degrees C, cell shrinkage had hardly any effect on K influx, but below 12 degrees C the influx in shrunken cells was significantly less than in cells of normal volume. 7. The selective increase in Na flux induced by cell shrinkage results from a Na:Na exchange process which cannot be explained in terms of Ussing's (1947) model of carrier-mediated exchange diffusion. 8. The lack of coupling between the effects of temperature and cell volume on the fluxes of Na and K indicates that localized structural changes of lipid-protein complexes specific for Na or K are responsible for the cation transport characteristics of dog red cells, and that phase transitions in the lipids of the cell membrane are unlikely to account for the temperature dependence of the fluxes.  相似文献   
10.
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.   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