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   141638篇
  免费   6151篇
  国内免费   337篇
耳鼻咽喉   2278篇
儿科学   4487篇
妇产科学   3074篇
基础医学   18884篇
口腔科学   4706篇
临床医学   8688篇
内科学   35122篇
皮肤病学   4682篇
神经病学   10908篇
特种医学   3222篇
外国民族医学   2篇
外科学   17826篇
综合类   832篇
一般理论   40篇
预防医学   13579篇
眼科学   3278篇
药学   9704篇
中国医学   712篇
肿瘤学   6102篇
  2023年   876篇
  2022年   811篇
  2021年   3059篇
  2020年   1578篇
  2019年   3354篇
  2018年   5415篇
  2017年   3134篇
  2016年   2933篇
  2015年   3283篇
  2014年   3930篇
  2013年   5806篇
  2012年   10011篇
  2011年   10704篇
  2010年   5450篇
  2009年   3969篇
  2008年   8574篇
  2007年   9124篇
  2006年   8532篇
  2005年   8405篇
  2004年   7430篇
  2003年   6979篇
  2002年   6586篇
  2001年   4179篇
  2000年   4841篇
  1999年   3631篇
  1998年   639篇
  1997年   431篇
  1996年   402篇
  1995年   350篇
  1994年   266篇
  1992年   1406篇
  1991年   1172篇
  1990年   1060篇
  1989年   878篇
  1988年   741篇
  1987年   725篇
  1986年   711篇
  1985年   636篇
  1984年   455篇
  1983年   357篇
  1979年   371篇
  1975年   296篇
  1974年   353篇
  1973年   379篇
  1972年   315篇
  1971年   339篇
  1970年   331篇
  1969年   331篇
  1968年   295篇
  1967年   259篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Bone Mineral Density and Androgen Levels in Elderly Males   总被引:4,自引:0,他引:4  
To clarify the relationship of sex male hormones and bone in men, we studied in 140 healthy elderly men (aged 55–90 years) the relation between serum levels of androgens and related sex hormones, bone mineral density (BMD) at different sites, and other parameters related to bone metabolism. Our results show a slight decrease of serum-free testosterone with age, with an increase of follicle stimulating hormone (FSH) and luteinizing hormone (LH) in a third of the elderly subjects studied. BMD decreased significantly with age in all regions studied, except in the lumbar spine. We found a positive correlation between body mass index (BMI) and BMD at the lumbar spine and femoral neck (P < 0.001). No relationship was found (uni- and multivariate regression analysis) between serum androgens or sex hormone-binding globulin (SHBG) and BMD. We found a positive correlation of vitamin D binding protein (DBP) and osteocalcin with lumbar spine BMD and with BMI, DBP, IGF-1, and PTH with femoral neck BMD. In conclusion, there is a slight decline in free testosterone and BMD in the healthy elderly males. However, sex male hormones are not correlated to the decrease in hip BMD. Other age-related factors must be associated with bone loss in elderly males. Received: 29 April 1997 / Accepted: 9 November 1997  相似文献   
994.
To investigate 1) the correlation between the proliferative activity of epididymal epithelium plus myoid cells and the increase in the number of these cells and 2) the role of the basal epithelial cells in the renewal of epididymal epithelium, a quantitative evaluation of the proliferation of both epithelial cells and periductal myoid cells in the different epididymal regions (caput, corpus, and cauda) has been carried out during postnatal development of the rat by immunohistochemical evaluation of BrdU-labeling indices. These data were correlated with cell numbers and counted by the optical dissector method. The presence of bcl-2 protein was immunohistochemically detected and evaluated. No significant differences in BrdU indices were observed among epididymal regions in any stage studied. Cell proliferation decreased from the prepubertal period to adulthood in both epithelial and myoid cells in the three regions of the epididymis, suggesting a close relationship between epithelial and mesenchymal components. The numbers of both cell types were significantly higher in the caput than in the corpus and cauda in all stages studied, suggesting functional differences between regions. A negative linear correlation between proliferative activity and cell numbers was noted that might be related to regulation of the cell population size. Basal cells showed a lower proliferation rate than principal cells, but most of the immunoreactive bcl-2 protein, in pubertal and adult epididymides, was observed in basal cells. Therefore, these cells might comprise a low-proliferating and apoptosis-resistant population.  相似文献   
995.
In approximately 25-40% of infants presenting with posterior urethral valves (PUV) renal insufficiency will develop before adolescence. In some these patients, renal dysplasia, bladder dysfunction and mismanagement may precipitate renal failure at even earlier age. The goals of this study were to determine whether long-term bladder dysfunction was more frequent in children who underwent early temporary pyelostomy than in those who underwent valve ablation, and to know if bladder dysfunction and mismanagement, in some patients, could be responsible of early renal failure. Urodynamic studies were performed in 59 boys with severe PUV divided into two groups based on initial treatment. A) Valve ablation (30 p.); B) Cutaneous pyeloureterostomy (29 p.). At the end of the study 22 boys had chronic renal failure. Of the 59 boys, 42% (25 p.) had bladders with overdistended or normal behaviour, 58% (34 p.) had bladder dysfunction (instability 37%, low compliance 15%, myogenic failure 5%). The 89% of low compliance bladders, 66% of myogenic failure and 23% of those with instability were in CRF. No difference at all was found in bladder function between boys treated as neonates by high diversion or valve ablation. Of the group in chronic renal failure (22 p.), only 7 patients (32%) had bladders with normal behaviour and in five of these patients a mismanagement was directly related with a quicker renal deterioration. The 58% of our boys with severe PUV have some type of bladder dysfunction. Neonatal pyelo-ureterostomy does not increase long-term bladder dysfunction. Surgical mismanagement should be added to bladder dysfunction as contributors to earlier renal failure.  相似文献   
996.
997.
998.
Urinary infection due to urea splitting bacteria leads to a rise in urinary pH, favouring the precipitation of calcium salts and struvita crystals. If deposited on the surface of a bladder with chronic inflammation or some other previous lesion, may produce an alkaline encrusted cystitis, now a rare condition. In the case here presented, occurred in a 69-year-old male. Corynebacterium urealyticum grown in the urine, and some foci of malakoplakia were found in the area of encrustation endoscopically excised. This case seems to be the third example of alkaline encrusted cystitis associated with malakoplakia reported in the bibliography. These two conditions share similar clinical signs and may probably have a common aetiopathogenesis.  相似文献   
999.
Presentation of one case of scrotal hernia in a man of 64 years old patient. Diagnosed by cistography and ultrasound and treated by herniorraphy and posterior transuretral litolaplaxy of a vesical litiasis and RTU of prostate. Postoperative urography showed normal vesical morphology.  相似文献   
1000.
Study of 165 patients with prostate adenocarcinoma who underwent radical prostatectomy using a retropubic approach. Mean PSA is 19 ng/ml, mean age 63 years and median follow-up 26 months. 22 patients (13.2%) reported complications during the first month post-surgery, primarily urinary fistula of more than 5 days long in 5 patients and rectal injury in 3.49 patients (29%) reported complications after the first month, mainly urinary incontinence in 26 cases and stenosis of the urethrovesical juncture in 15. The group with early complications showed no significant differences compared to those who had none, neither in PSA (p = 0.3) or a worse pathological stage (p = 0.1), and no evidence is shown in terms of biochemical progression or in disease free progression (p = 1). Patients with urethrovesical juncture stenosis have higher mean PSA (p = 0.01), greater biochemical progression (p = 0.006), worse Gleason (p = 0.03 = and worse progression free survival (p = 0.01). Patients with stress incontinence showed no differences compared to the other groups relative to the studied factors.  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