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   580362篇
  免费   67243篇
  国内免费   283篇
  647888篇
  2018年   4869篇
  2016年   6507篇
  2015年   8726篇
  2014年   10467篇
  2013年   14755篇
  2012年   16507篇
  2011年   16870篇
  2010年   11253篇
  2009年   10433篇
  2008年   14927篇
  2007年   15503篇
  2006年   14824篇
  2005年   14341篇
  2004年   14271篇
  2003年   13871篇
  2002年   13611篇
  2001年   28885篇
  2000年   29162篇
  1999年   22853篇
  1998年   7449篇
  1997年   7739篇
  1996年   7301篇
  1995年   6842篇
  1994年   6833篇
  1993年   6800篇
  1992年   18849篇
  1991年   18311篇
  1990年   17748篇
  1989年   17354篇
  1988年   16252篇
  1987年   15292篇
  1986年   13842篇
  1985年   13902篇
  1984年   11243篇
  1983年   9878篇
  1982年   7438篇
  1981年   6556篇
  1980年   6300篇
  1979年   10884篇
  1978年   8290篇
  1977年   7644篇
  1976年   6951篇
  1975年   7716篇
  1974年   8254篇
  1973年   8263篇
  1972年   7429篇
  1971年   6937篇
  1970年   6047篇
  1969年   5794篇
  1968年   5175篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE--To examine the relation between bone density and indices of calcium metabolism including parathyroid hormone and 25-hydroxyvitamin D concentrations in middle aged women. DESIGN--A cross sectional study. SETTING AND SUBJECTS--138 women volunteers aged 45-65 with no known osteoporosis and unselected for disease status recruited for a dietary assessment study from the community using general practice registers. Volunteer rate was 20%. MAIN OUTCOME MEASURE--Bone mineral density measured with dual energy x ray absorptiometry. RESULTS--Bone density at the lumbar spine and neck and trochanteric regions of the femur was inversely related to serum intact parathyroid hormone concentrations and positively related to serum 25-hydroxyvitamin D concentrations. These associations were independent of possible confounding factors, including age, body mass index, cigarette smoking habit, menopausal status, and use of diuretics and postmenopausal hormone replacement therapy. These associations were apparent throughout the whole distribution of bone density and 25-hydroxyvitamin D and parathyroid hormone concentrations within the normal range, suggesting a physiological relation. CONCLUSIONS--The findings are consistent with the hypothesis that parathyroid hormone and 25-hydroxyvitamin D concentrations influence bone density in middle aged women. Findings from this study together with other work suggest that the role of vitamin D in osteoporosis should not be neglected. The associations with parathyroid hormone also indicate plausible biological mechanisms. The roughly 5-10% difference in bone density between top and bottom tertiles of serum 25-hydroxyvitamin D concentrations, though not large in magnitude, may have considerable public health implications in terms of prevention of osteoporosis and its sequelae, fractures.  相似文献   
42.
43.
44.
Argon laser surgery is an effective treatment for ectasias and congenital port-wine stains; however, its use in children under the age of 13 is controversial. This paper reviews 202 children under the age of 13 who underwent argon laser treatments for congenital port-wine stains, spider angiomas, epidermal nevi, and lentigines. The clinical characteristics of port-wine stains in 170 children are discussed. Good to excellent results (moderate to complete clearing) in port-wine stains were obtained in 60 percent of patients and seemed to correlate best with lack of blanchability on pressure. Hypertrophic scarring was seen in only 7 children, all of whom had undressed wounds; no significant scarring has been seen in any subsequent child who had maintained a dressed wound postoperatively.  相似文献   
45.
46.
Trigger finger is a relatively common clinical entity, most frequently caused by stenosing tenosynovitis. Several other conditions not related to tenosynovitis also have been described as a cause of triggering, and these have been reviewed. We present a rare anomaly of the fourth lumbrical muscle insertion as a cause of triggering of the right little finger. This was completely relieved following excision of the anomalous muscle. This rare anatomic variant should be added to the list of potential causes of trigger finger.  相似文献   
47.
48.
49.
50.
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