全文获取类型
收费全文 | 573755篇 |
免费 | 66633篇 |
国内免费 | 276篇 |
专业分类
640664篇 |
出版年
2018年 | 4790篇 |
2016年 | 6380篇 |
2015年 | 8541篇 |
2014年 | 10239篇 |
2013年 | 14475篇 |
2012年 | 16153篇 |
2011年 | 16530篇 |
2010年 | 11049篇 |
2009年 | 10264篇 |
2008年 | 14642篇 |
2007年 | 15235篇 |
2006年 | 14553篇 |
2005年 | 14079篇 |
2004年 | 14008篇 |
2003年 | 13628篇 |
2002年 | 13379篇 |
2001年 | 28810篇 |
2000年 | 29107篇 |
1999年 | 22773篇 |
1998年 | 7362篇 |
1997年 | 7685篇 |
1996年 | 7237篇 |
1995年 | 6792篇 |
1994年 | 6769篇 |
1993年 | 6747篇 |
1992年 | 18779篇 |
1991年 | 18232篇 |
1990年 | 17687篇 |
1989年 | 17295篇 |
1988年 | 16207篇 |
1987年 | 15232篇 |
1986年 | 13795篇 |
1985年 | 13859篇 |
1984年 | 11165篇 |
1983年 | 9820篇 |
1982年 | 7361篇 |
1981年 | 6496篇 |
1980年 | 6214篇 |
1979年 | 10825篇 |
1978年 | 8221篇 |
1977年 | 7571篇 |
1976年 | 6896篇 |
1975年 | 7666篇 |
1974年 | 8196篇 |
1973年 | 8190篇 |
1972年 | 7400篇 |
1971年 | 6894篇 |
1970年 | 6010篇 |
1969年 | 5753篇 |
1968年 | 5152篇 |
排序方式: 共有10000条查询结果,搜索用时 0 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.