全文获取类型
收费全文 | 2143404篇 |
免费 | 163965篇 |
国内免费 | 4291篇 |
专业分类
耳鼻咽喉 | 29821篇 |
儿科学 | 74030篇 |
妇产科学 | 59684篇 |
基础医学 | 308695篇 |
口腔科学 | 59183篇 |
临床医学 | 191605篇 |
内科学 | 420381篇 |
皮肤病学 | 47375篇 |
神经病学 | 170922篇 |
特种医学 | 84312篇 |
外国民族医学 | 945篇 |
外科学 | 323194篇 |
综合类 | 47277篇 |
现状与发展 | 2篇 |
一般理论 | 801篇 |
预防医学 | 168868篇 |
眼科学 | 48163篇 |
药学 | 156191篇 |
5篇 | |
中国医学 | 4182篇 |
肿瘤学 | 116024篇 |
出版年
2018年 | 23057篇 |
2017年 | 17755篇 |
2016年 | 19828篇 |
2015年 | 22447篇 |
2014年 | 31052篇 |
2013年 | 46997篇 |
2012年 | 63956篇 |
2011年 | 67777篇 |
2010年 | 40325篇 |
2009年 | 38347篇 |
2008年 | 63938篇 |
2007年 | 68060篇 |
2006年 | 68503篇 |
2005年 | 66211篇 |
2004年 | 64144篇 |
2003年 | 61807篇 |
2002年 | 60057篇 |
2001年 | 100541篇 |
2000年 | 103522篇 |
1999年 | 87831篇 |
1998年 | 24893篇 |
1997年 | 22359篇 |
1996年 | 22620篇 |
1995年 | 21575篇 |
1994年 | 20268篇 |
1993年 | 18778篇 |
1992年 | 69805篇 |
1991年 | 68307篇 |
1990年 | 66566篇 |
1989年 | 63881篇 |
1988年 | 58566篇 |
1987年 | 58063篇 |
1986年 | 54270篇 |
1985年 | 52294篇 |
1984年 | 39213篇 |
1983年 | 33092篇 |
1982年 | 19498篇 |
1981年 | 17652篇 |
1979年 | 35508篇 |
1978年 | 25115篇 |
1977年 | 21284篇 |
1976年 | 19949篇 |
1975年 | 21339篇 |
1974年 | 25280篇 |
1973年 | 24401篇 |
1972年 | 22453篇 |
1971年 | 20704篇 |
1970年 | 19339篇 |
1969年 | 17716篇 |
1968年 | 16376篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Judith B. Erickson 《Child & youth care forum》1988,17(2):86-103
Several million American children are currently unsupervised during the hours between school and parents' leaving for and/or return from the workplace. Many families would prefer other arrangements, but cost or availability factors present insurmountable barriers. Although growing, the public response continues to fall far short of the need; in the meantime, private entrepreneurs are moving to fill the gaps in available services. But if these programs for school-aged children are to serve functions other than the aggrandizement of their sponsors, they must be focused on the real needs that exist among real American children. Among the real children in need of care are those who are impoverished, unsupervised, unfit physically, unprepared for the demands of school and workplace, hurried into premature adulthood, and/or disconnected from the social worlds around them. Professional child and youth care workers with experience in day care and residential settings have the preparation needed to take leadership roles in creating developmentally appropriate, effective programs to meet the emerging demands for school-age child care and to weave them into a fabric of youth-centered community services. 相似文献
993.
994.
Juvenile hypocalcemia provokes persistent electroencephalographic change in renally compromised rats
J J Lipman D L White P L Lawrence P E Teschan 《Journal of the American College of Nutrition》1988,7(6):453-460
In view of the putative involvement of calcium in uremic encephalopathy and the critical importance of this element in juvenile development, we examined the effect of temporary restriction of dietary calcium intake on serum chemistry and the quantitative electroencephalogram (Q.EEG) in unilaterally 3/4 nephrectomized juvenile male Sprague-Dawley rats. Animals were renally infarcted at 22-26 days of age (50-74 g) and placed on one of two isocaloric dietary regimens: powdered normal rat diet (ND, n = 25) or low calcium diet (LCD, n = 8) for 30 days. At this time, ND animals showed normal serum chemistries, whereas LCD rats were hypocalcemic and azotemic with significantly elevated blood urea nitrogen (BUN) and serum creatinine concentrations and reduced renal creatinine clearance values. All animals thereafter received ND for 25-34 further days, during which time chronic Q.EEG electrodes were implanted. At the end of the common ND feeding period, serum chemistry values were equal and normal in both groups. The average theta/alpha ratio (TAR) of the overnight Q.EEG was assessed for 3 days. We found that the TAR of previously LCD animals was significantly elevated compared with ND rats. This indicates an encephalopathic slowing of the background rhythm of these animals. We conclude that, following restoration of a transient uremic and hypocalcemic episode induced by LCD feeding, the Q.EEG background frequency of juvenile renally impaired rats was abnormally slow after 30 days of ND feeding. 相似文献
995.
996.
Lifetime fracture risk: an approach to hip fracture risk assessment based on bone mineral density and age 总被引:8,自引:0,他引:8
Hip fractures occur late in life following a substantial reduction in skeletal mass. If risk for such fractures could be predicted early, efforts to prevent excessive bone loss would be more successful and could be directed at the individuals most likely to be affected. With this objective in mind, we devised an approach to estimating the lifetime risk of a proximal femur fracture based on age and on current femoral bone mineral density, using population-based data from ongoing studies of osteoporosis and fractures among Rochester, Minnesota, women. Our calculations indicate that, at any given age, the lifetime risk of a proximal femur fracture rises as current bone density diminishes. At any given level of femoral bone density, lifetime risk rises with younger age and increasing life expectancy. While these trends seem robust, estimates of risk vary substantially with the assumptions that underlie the model. Consequently, these assumptions must be validated before our findings can be applied clinically to predict risk for individual patients. 相似文献
997.
998.
This paper examines the effects of intraocular epinephrine on systemic blood pressure and heart rate during cataract surgery. Sixty-two patients were studied, all of whom received an intraocular infusion of approximately 200 to 300 mL of balanced salt solution with 0.5 mL of epinephrine 1:1000. There was no statistically significant change in blood pressure or heart rate during the time of epinephrine administration. Electrocardiogram monitoring during surgery showed no changes. We believe that dilute concentrations of epinephrine administered during extracapsular cataract extraction pose little threat of systemic toxicity. 相似文献
999.
S de Bustros J T Thompson R G Michels T A Rice B M Glaser 《The British journal of ophthalmology》1988,72(9):692-695
We used vitreous surgery to remove idiopathic epiretinal membranes from the macular area in 70 consecutive cases. The abnormal tissue was successfully removed in each case. Vision improved postoperatively in 61 eyes (87%), remained unchanged in six eyes (9%), and worsened in three eyes (4%). However, at the time of final examination vision was improved in only 47 eyes (67%), primarily because of the occurrence or progression of nuclear sclerosis, which occurred in 38 of 60 phakic eyes (63%). Four preoperative factors were associated with final visual acuity of 20/60 or better: (1) initial vision of 20/100 or better, (2) shorter preoperative duration of blurred vision, (3) thin epiretinal membrane, and (4) absence of traction retinal detachment. 相似文献
1000.