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   738篇
  免费   39篇
  国内免费   3篇
耳鼻咽喉   7篇
儿科学   109篇
妇产科学   35篇
基础医学   74篇
口腔科学   6篇
临床医学   59篇
内科学   135篇
皮肤病学   13篇
神经病学   33篇
特种医学   42篇
外科学   81篇
综合类   12篇
预防医学   35篇
眼科学   86篇
药学   27篇
中国医学   3篇
肿瘤学   23篇
  2023年   4篇
  2022年   10篇
  2021年   28篇
  2020年   9篇
  2019年   20篇
  2018年   22篇
  2017年   10篇
  2016年   7篇
  2015年   18篇
  2014年   19篇
  2013年   23篇
  2012年   31篇
  2011年   32篇
  2010年   33篇
  2009年   23篇
  2008年   33篇
  2007年   35篇
  2006年   45篇
  2005年   45篇
  2004年   54篇
  2003年   41篇
  2002年   39篇
  2001年   14篇
  2000年   15篇
  1999年   11篇
  1998年   6篇
  1997年   9篇
  1996年   3篇
  1995年   4篇
  1994年   7篇
  1993年   5篇
  1992年   11篇
  1991年   11篇
  1990年   13篇
  1989年   12篇
  1988年   12篇
  1987年   14篇
  1986年   12篇
  1985年   11篇
  1984年   4篇
  1983年   6篇
  1982年   2篇
  1980年   4篇
  1978年   2篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1971年   1篇
  1969年   2篇
  1967年   1篇
排序方式: 共有780条查询结果,搜索用时 15 毫秒
51.
Fetal lung volume: estimation at MR imaging-initial results   总被引:6,自引:0,他引:6  
PURPOSE: To plot normal fetal lung volume (FLV) obtained with fast spin-echo magnetic resonance (MR) images against gestational age; to investigate the correlation between lung growth and fetal presentation, sex, and ultrasonographic (US) biometric measurements; and to investigate its potential application in fetuses with thoracoabdominal malformations. MATERIALS AND METHODS: In a prospective multicenter study, 336 fetuses suspected of having central nervous system disorders underwent fast spin-echo T2-weighted lung MR imaging. Data obtained at 21-38 weeks gestation in 215 fetuses without thoracoabdominal malformations and with normal US biometric findings were selected for an FLV normative curve. FLV measurements obtained at pathologic examination with an immersion method were compared with MR FLV measurements in 11 fetuses. MR FLV values in 16 fetuses with thoracoabdominal malformations were compared with the normative curve. RESULTS: Normal FLV increased with gestational age as a power curve; the spread of values increased with age. Interobserver correlation was excellent (R(2) = 0.96). FLV measurements at MR imaging were 0.90 times those at pathologic examination. A constant ratio (0.78) between FLV on the left and right sides was observed. No significant difference in FLV was observed between fetal presentations. Normal FLV was observed in all fetuses with cystic adenomatoid malformations and in four of six with oligohydramnios. Lowest FLV values were observed in fetuses with diaphragmatic hernia. CONCLUSION: In fetuses with normal lungs, FLV distribution against gestational age is easily assessed in utero with fast spin-echo T2-weighted MR imaging. These preliminary findings illustrate the potential for comparing FLV measurements in fetuses at risk of lung hypoplasia with normative values.  相似文献   
52.
A case of gastric pneumatosis is described in a 6 month old girl with Down syndrome. Plain abdominal radiographs showed a radiolucent rim within the gastric wall and a dilated stomach. Ultrasonography showed diffuse echoic streaks of air in the gastric wall, pneumobilia and gastroduodenal dilatation. Upper GI series showed duodenal stenosis. Gastric pneumatosis (air within the gastric wall), is an unusual radiographic finding. It may be of mechanical or inflammatory origin or, in some rare cases, remain unexplained.  相似文献   
53.
Sesame food allergy (SFA) in children is an increasingly recognized one in many countries. Our objective was to describe the course and natural history of SFA. Seventy-four patients sensitized to sesame were evaluated using clinical records, questionnaires, skin prick tests (SPT), in vitro specific immunoglobulin (sIg) E, and oral challenges (OC) and categorized into three groups: group A: patients who experienced allergic reaction after ingestion of sesame-containing food (n = 45); group B: patients evaluated for atopic dermatitis and found to be sesame SPT-positive (n = 11); group C: patients with sensitization to sesame allergen (n = 18). Group A patients were followed for an average of 6.7 yr. Analysis of our results revealed that 76% of patients in group A developed the allergy by the age of 2. The median age at onset of allergy in these patients was 1 yr. Immediate reaction to a minimal amount of sesame was characteristic. Skin was the most common site of involvement, followed by respiratory and gastrointestinal systems. Tolerance developed in only 20% of the patients. High sIgE (>0.15 IU) was demonstrated only in 75% of those in which it was examined. Sixteen patients performed oral sesame food challenge which was found positive in 88%. No correlation was found between the size of SPT and the level of in vitro sesame IgE antibodies, the outcome of OC results, and the development of tolerance to sesame. In conclusion, SFA tends to appear early in life, but unlike cow's milk and egg allergy, persists in 80% of the cases. Typical reactions combined with positive sesame SPT are reliable for diagnosis.  相似文献   
54.
Certain misleading appearances are peculiar to pediatric uroradiology. The most frequently encountered pitfalls are related to the bladder, to vesicoureteral reflux, and to the duplicated collecting system. The bi-chambered nature of the child's bladder, and the rapid settling of contrast material to the most dependent portion causes many pitfalls in diagnosis. When the child is prone, normal ureters may seem to be ectopic, and ureteroceles may become invisible. When the child is supine, the volume of urine in the bladder may be grossly under-estimated. Reflux can mimic function at urography. The dynamic nature of reflux leads to under-estimation of its presence and degree on the IVP and static cystogram. Reflux into an already dilated system can lead to over-estimation of its degree. Aberrant micturition with rapid refilling of the bladder can simulate incomplete emptying. The diagnosis of ectopic ureterocele is based on indirect evidence. Any condition that affects the urinary apparatus in the same way will have a similar appearance. A huge ureterocele may have a small ureter, and massive reflux into a lower pole ureter may make the diagnosis of duplication difficult. Ureterocele lookalikes, and effacement or intussusception of the ureterocele are cystographic pitfalls. Lower pole ureteropelvic junction obstruction and Wilms tumor in the lower portion of a kidney can have surprisingly similar appearances.  相似文献   
55.
Biopsy specimens from 23 early stage and 19 tumor‐stage mycosis fungoides (MF) patients were evaluated for miR‐155 expression by real‐time qualitative PCR and compared with 15 biopsy specimens from patients with T‐cell‐rich inflammatory skin diseases. Significant upregulation of miR‐155 was found in MF tumors compared with both early‐stage MF lesions and controls. There was no difference in miR‐155 expression between early‐stage and inflammatory dermatoses. Using laser capture microdissection, it was found that miR‐155 was significantly higher in the lymphoma cells in tumor stage compared with the intraepidermal lymphocytes in early stage. In contrast, there was no difference in miR‐155 expression between the intraepidermal lymphocytes and the dermal lymphocytes in early‐stage MF. These findings suggest that although miR‐155 expression cannot serve to discriminate early‐stage MF from inflammatory dermatoses; however, it is involved in the switch from the indolent early stage into the aggressive tumor stage of the disease.  相似文献   
56.
Prader–Willi syndrome is caused by the loss of paternal gene expression on 15q11.2–q13.2, and one of the mechanisms resulting in Prader–Willi syndrome phenotype is maternal uniparental disomy of chromosome 15. Various mechanisms including trisomy rescue, monosomy rescue, and post fertilization errors can lead to uniparental disomy, and its mechanism can be inferred from the pattern of uniparental hetero and isodisomy. Detection of a mosaic cell line provides a unique opportunity to understand the mechanism of uniparental disomy; however, mosaic uniparental disomy is a rare finding in patients with Prader–Willi syndrome. We report on two infants with Prader–Willi syndrome caused by mosaic maternal uniparental disomy 15. Patient 1 has mosaic uniparental isodisomy of the entire chromosome 15, and Patient 2 has mosaic uniparental mixed iso/heterodisomy 15. Genome‐wide single‐nucleotide polymorphism array was able to demonstrate the presence of chromosomally normal cell line in the Patient 1 and trisomic cell line in Patient 2, and provide the evidence that post‐fertilization error and trisomy rescue as a mechanism of uniparental disomy in each case, respectively. Given its ability of detecting small percent mosaicism as well as its capability of identifying the loss of heterozygosity of chromosomal regions, genome‐wide single‐nucleotide polymorphism array should be utilized as an adjunct to the standard methylation analysis in the evaluation of Prader–Willi syndrome. © 2012 Wiley Periodicals, Inc.  相似文献   
57.

Objective

To determine the incidence and temporal trends of food allergies.

Patients and Methods

We performed a historical cohort study to describe the epidemiology of food allergies among residents of all ages in Olmsted County, Minnesota, during a 10-year period from January 2, 2002, through December 31, 2011, using the Rochester Epidemiology Project database. Overall incidence and trends in biannual incidence rates over time were evaluated.

Results

During the 10-year study period, 578 new cases of food allergies were diagnosed. The average annual incidence rate was significantly higher among males compared with females (4.1 [95% CI, 3.6-4.5] vs 3.0 [95% CI, 2.7-3.4]; P<.001; per 10,000 person-years; 3.6 per 10,000 person-years overall). The pediatric incidence rate of food allergy increased from 7.0 (95% CI, 6.2-8.9) to 13.3 (95% CI, 10.9-15.7) per 10,000 person-years between the 2002-2003 and 2006-2007 calendar periods and then stabilized at 12.5 and 12.1 per 10,000 person-years in the last 2 calendar periods. Milk, peanut, and seafood were the most common allergen in infancy, in children between ages 1 and 4 years, and in the adult population, respectively.

Conclusion

This is one of the first population-based studies to examine the temporal trends of food allergies. The incidence of food allergies increased markedly between 2002 and 2009, with stabilization afterward. Additional longitudinal studies are warranted to assess for epidemiological evidence of changes in food allergy incidence with changing recommendations for allergenic food introduction.  相似文献   
58.
59.
Five patients with long-standing monocular traumatic aphakia and contact lens intolerance underwent epikeratophakia. This procedure was chosen to rehabilitate the visual function in those eyes that exhibited distorted anterior segment anatomy after trauma. Three of the patients had corneal scars associated with their old perforation wounds, and all of them had undergone an intracapsular cataract extraction soon after their original injuries. Best-corrected visual acuity was 20/50 or better in all cases before surgery. Postoperative best-corrected visual acuity improved to within two lines of the best-corrected preoperative visual acuity, after a minimum follow-up period of six months. No intraoperative complications were noted. One cornea developed late-onset partial scarring of the interface in the area of the original scar, but the process arrested spontaneously.  相似文献   
60.
A delay of more than one month between the birth of twins is an unusual occurrence presenting the obstetrician and the neonatalogist with many questions regarding the management of the case. There is the risk of prematurity for the second twin as labor has already occurred in the pregnancy. There is also a risk of infection to both mother and fetus during the interval between the two deliveries, since the stump of the first twin's cord may precipitate ascending colonization from vagina and cervix. Germs frequently recovered from the vagina e.g. Ureaplasma urealyticum, are associated with prematurity. The latter has also been responsible for lethal interstitial pneumonia in the neonate. We present a case of a patient who though she delivered twice normally, had suffered 4 first trimester abortions and one late abortion, all spontaneous. Her eighth pregnancy was a twin pregnancy. She underwent a cerclage at 14 weeks, but went into labor at 17 weeks, when she delivered the first macerated twin. She was then treated with fenoterol and ampicillin; nevertheless she delivered twin the second at 26 weeks. This 750 g baby-girl presented with severe respiratory distress. Repeated chest X rays showed perihilar infiltrates which became nodular. All cultures were negative. At the end of the first week, when her condition was considered satisfactory, she deteriorated dramatically and died in respiratory failure and DIC. Tracheal aspirates were positive for Ureaplasma urealyticum.  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