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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   249337篇
  免费   2371篇
  国内免费   177篇
耳鼻咽喉   1886篇
儿科学   9193篇
妇产科学   4990篇
基础医学   27408篇
口腔科学   2700篇
临床医学   18707篇
内科学   46507篇
皮肤病学   2219篇
神经病学   23744篇
特种医学   10650篇
外科学   35184篇
综合类   2667篇
现状与发展   1篇
一般理论   46篇
预防医学   24420篇
眼科学   4182篇
药学   15121篇
  3篇
中国医学   819篇
肿瘤学   21438篇
  2024年   739篇
  2023年   890篇
  2022年   1707篇
  2021年   2909篇
  2020年   1767篇
  2019年   2252篇
  2018年   23978篇
  2017年   18995篇
  2016年   21447篇
  2015年   3246篇
  2014年   3852篇
  2013年   4754篇
  2012年   12492篇
  2011年   26482篇
  2010年   21656篇
  2009年   13827篇
  2008年   23203篇
  2007年   25386篇
  2006年   4186篇
  2005年   5500篇
  2004年   6519篇
  2003年   7162篇
  2002年   5129篇
  2001年   1001篇
  2000年   1054篇
  1999年   844篇
  1998年   696篇
  1997年   614篇
  1996年   405篇
  1995年   384篇
  1994年   360篇
  1993年   291篇
  1992年   416篇
  1991年   416篇
  1990年   448篇
  1989年   390篇
  1988年   367篇
  1987年   331篇
  1986年   322篇
  1985年   305篇
  1984年   305篇
  1983年   259篇
  1982年   213篇
  1979年   257篇
  1975年   212篇
  1974年   246篇
  1973年   216篇
  1970年   215篇
  1968年   220篇
  1967年   219篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Variation in the risk of breast cancer observed among women and among populations may be explained by variation in lifetime exposure to estrogens. The suppressive effect of exercise on estradiol levels in women is well documented, but it is unknown whether habitual (i.e. typical daily) physical activity has a similar effect. Epidemiological data suggest that physical activity is one of the few modifiable factors capable of reducing the risk of breast cancer in women. We investigated whether variation in the amount of habitual activity corresponds to variation in estradiol levels in women of reproductive age. One hundred and thirty-nine regularly menstruating women 24-37 years of age collected daily saliva samples for one complete menstrual cycle and kept a daily log of physical activity. Saliva samples were analyzed for concentration of estradiol. We observed a negative relationship between habitual physical activity and salivary levels of estradiol. Mean estradiol was 21.1 pmol/l in the low, 17.9 pmol/l in the moderate and 16.6 pmol/l in the high activity group (all pairwise differences were statistically significant at P<0.009). A strong association exists between physical activity and levels of estradiol among women of reproductive age. A modern lifestyle, characterized by reduced physical activity, may therefore contribute to a rise in the levels of estradiol produced during menstrual cycles and thus to higher cumulative lifetime exposure to estradiol, resulting in a higher risk of breast cancer.  相似文献   
102.
103.
104.
There are very few reported cases of 'milk of renal calcium' since Holm's first presentation of this rare condition in 1948 [Rosenberg, J. Urol., 101: 714, 1967]. We recently had the opportunity to study 2 more cases, which are described herein.  相似文献   
105.
Progesterone secretion of cultured human granulosa cells treated with LHRH or its analogues was measured. Granulosa cells were also stimulated with LH, FSH, cAMP or forskolin. No differences could be observed in the progesterone basal secretion of cultures treated with or without LHRH or its analogues and after the various stimulations. It was concluded that the clinical experience that the sensitivity of ovaries for gonadotropins after LHRH desensitization is decreased could not be explained with the peripheral effects of LHRH on the granulosa cells. From the data obtained, the lack of LHRH receptors in the ovaries are suggested in humans.  相似文献   
106.
107.
This study aimed to investigate whether endothelial cells are damaged and to evaluate fibrinolytic system function in patients with type 2 diabetes. For this proposal, plasma levels of von Willebrand factor (an endothelial marker of injury), homocysteine (an inductor of endothelial injury), D-dimer (a marker of coagulation cascade activation) and plasminogen activator inhibitor-1 (a fibrinolysis marker) were measured in individuals with both type 2 diabetes and high blood pressure, with type 2 diabetes, with high blood pressure and in healthy control individuals. No significant differences among groups were observed for von Willebrand factor and homocysteine plasma levels. The type 2 diabetes and high blood pressure group presented a significant difference to the other groups for D-dimer and also presented high values for plasminogen activator inhibitor-1. The high blood pressure group and type 2 diabetes group presented separately higher values of plasminogen activator inhibitor-1 compared with the control group. High levels of D-dimer and plasminogen activator inhibitor-1 in patients with type 2 diabetes and high blood pressure with normoalbuminuria therefore indicate a state of hypercoagulability and hypofibrinolysis, despite no evident microvascular injury supported by normal levels of von Willebrand factor and homocysteine.  相似文献   
108.

Background  

Despite considerable knowledge about musculoskeletal disorders (MSD) and physical, psychosocial and individual risk factors there is limited knowledge about physical activity as a factor in preventing MSD. In addition, studies of physical activity are often limited to either leisure activity or physical activity at work. Studies among military personnel on the association between physical activity at work and at leisure and MSD are lacking. This study was conducted to find the prevalence of MSD among personnel in the Royal Norwegian Navy and to assess the association between physical activity at work and at leisure and MSD.  相似文献   
109.
Lateral unicompartmental knee arthroplasty (UKA) is a valid alternative treatment in the event of arthritis confined to the lateral compartment. This paper examines its indications, technique and short to medium-term results. A total of 159 Miller–Galante cemented UKA prostheses (Zimmer, Warsaw, Indiana) were implanted consecutively (131 medial and 28 lateral) by the same surgeon. This study investigates 28 lateral UKAs in 27 patients. Twenty-five implants in 24 patients (including a subject operated bilaterally) were followed up for 12–60 months. Three patients were discarded on account of to short a follow-up period. The Hospital for Special Surgery (HSS) knee score was used to compare the pre- and post-operative results of the lateral UKA patients. The HSS score improved from a pre-op mean of 59.92 (range 48–68) to 88.04 (range 71–95) at the last follow-up. There was a positive increase in the pain, function and ROM components of the score. The lateral UKA prosthesis can be regarded as a sound alternative to total knee replacement. Correct patient selection on the basis of optimum surgical indications, however, is essential. No benefits of funds were received in support of the study.  相似文献   
110.
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