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   939064篇
  免费   67979篇
  国内免费   1406篇
耳鼻咽喉   13055篇
儿科学   24461篇
妇产科学   23355篇
基础医学   133863篇
口腔科学   28617篇
临床医学   81107篇
内科学   185309篇
皮肤病学   19581篇
神经病学   72668篇
特种医学   37118篇
外国民族医学   79篇
外科学   153474篇
综合类   18077篇
现状与发展   1篇
一般理论   234篇
预防医学   62001篇
眼科学   21629篇
药学   72988篇
  3篇
中国医学   2180篇
肿瘤学   58649篇
  2018年   9137篇
  2017年   7164篇
  2016年   7910篇
  2015年   9007篇
  2014年   12201篇
  2013年   17752篇
  2012年   24587篇
  2011年   25528篇
  2010年   15135篇
  2009年   14500篇
  2008年   25084篇
  2007年   26202篇
  2006年   26946篇
  2005年   25895篇
  2004年   25043篇
  2003年   24014篇
  2002年   23551篇
  2001年   54890篇
  2000年   56758篇
  1999年   47141篇
  1998年   10861篇
  1997年   9554篇
  1996年   9665篇
  1995年   9008篇
  1994年   8345篇
  1993年   7649篇
  1992年   35601篇
  1991年   34018篇
  1990年   32838篇
  1989年   32007篇
  1988年   29114篇
  1987年   28342篇
  1986年   26366篇
  1985年   25232篇
  1984年   17899篇
  1983年   15200篇
  1982年   7832篇
  1981年   6788篇
  1979年   15848篇
  1978年   10649篇
  1977年   9096篇
  1976年   7914篇
  1975年   8661篇
  1974年   10514篇
  1973年   9898篇
  1972年   9404篇
  1971年   8885篇
  1970年   8453篇
  1969年   7956篇
  1968年   7231篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
This study was conducted to determine if lower steroid secretion by the small white follicles in incubating turkey hens contributes to lower circulating steroid concentrations during this time. Turkey hens were grouped as either laying or incubating. Serum samples and the ovarian small white follicles (SWF; 2-7 mm diameter) were collected from each hen. The SWF were pooled for each group and their cells were dispersed by trypsin digestion. Serum-luteinizing hormone (LH), progesterone (P), testosterone (T), and estradiol (E) concentrations were lower and serum prolactin concentration was higher during incubation than during egg laying. SWF cells from incubating hens secreted more P and T and less E in response to ovine luteinizing hormone (oLH) than did similar cell suspensions from laying hens. The incubating hens' SWF cells' capacity to secrete E but not their capacity to secrete P or T in vitro is consistent with the observed circulating levels. It is hypothesized that lower levels of circulating LH and/or higher levels of prolactin found in incubating hens may have a depressing effect on aromatase activity and/or an up-regulating effect on LH-induced P and T secretion by the SWF cells.  相似文献   
932.
933.
A variety of nutritional factors influence the bioavailability of calcium and increase a woman's risk of osteoporosis. Eight healthy women completed an 8-week metabolic study designed to investigate the effect of nonalcoholic carbonated beverage consumption on calcium metabolism. Compared with women receiving a control diet, women consuming a diet high in nonalcoholic carbonated beverages demonstrated similar mean serum levels of calcium, ionized calcium, phosphorus, alkaline phosphatase, parathyroid hormone, 1,25-dihydroxyvitamin D3, and osteocalcin. Twenty-four-hour urine volume, creatinine clearance, calcium-creatinine ratio, and phosphorus-creatinine ratio were similar during consumption of the diet high in nonalcoholic carbonated beverages and the control diet. Twenty-four-hour cyclic adenosine monophosphate-creatinine ratio was significantly lower in women consuming the diet high in nonalcoholic carbonated beverage compared with women receiving the control diet (342 +/- 27.4 nmol/mmol vs 409 +/- 22.1 nmol/mmol). Consumption of a diet high in nonalcoholic carbonated beverages on a short-term basis does not appear to affect adversely the serum or urinary markers of calcium metabolism.  相似文献   
934.
935.
936.
Bone and joint sepsis   总被引:1,自引:0,他引:1  
  相似文献   
937.
Cancers du sein     
T. Petit 《Oncologie》2007,9(9):593-644
  相似文献   
938.
The article presents an original method of laparoscopic anti-reflux surgery, immediate and long-term results of the treatment of 132 patients with esophageal opening hernia. It also describes the analysis of the life quality of patients with the gastroesophageal reflux disease before and after the surgery.  相似文献   
939.
940.
Unilateral and bilateral variation in the course and elongation of the cervical (extracranial) part of the internal carotid artery (ICA) leading to its tortuosity, kinking and coiling or looping is not a rare condition, which could be caused by both embryological and acquired factors. Patients with such variations may be asymptomatic in some cases; in others, they can develop cerebrovascular symptoms due to carotid stenosis affecting cerebral circulation. The risk of transient ischemic attacks in patients with carotid stenosis is high and its surgical correction is indicated for the prevention of ischemic stroke. Detection of developmental variations of the ICA and evaluation of its stenotic areas is very important for surgical interventions and involves specific diagnostic imaging techniques for vascular lesions including contrast arteriography, duplex ultrasonography and magnetic resonance angiography. Examination of obtained images in cases of unusual and complicated variations of vascular pattern of the ICA may lead to confusion in interpretation of data. Awareness about details and topographic anatomy of variations of the ICA may serve as a useful guide for both radiologists and vascular surgeons. It may help to prevent diagnostic errors, influence surgical tactics and interventional procedures and avoid complications during the head and neck surgery. Our present study was conducted with a purpose of updating data about developmental variations of the ICA. Dissections of the main neurovascular bundle of the head and neck were performed on a total 14 human adult cadavers (10 – Africans: 7 males & 3 females and 4 – East Indians: all males). Two cases of unilateral congenital elongation of the cervical part of the ICA with kinking and looping and carotid stenoses were found only in African males. Here we present their detailed case reports with review of the literature.  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