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   3727篇
  免费   263篇
  国内免费   5篇
耳鼻咽喉   69篇
儿科学   130篇
妇产科学   65篇
基础医学   451篇
口腔科学   101篇
临床医学   436篇
内科学   781篇
皮肤病学   54篇
神经病学   376篇
特种医学   196篇
外科学   400篇
综合类   71篇
一般理论   1篇
预防医学   312篇
眼科学   78篇
药学   290篇
中国医学   3篇
肿瘤学   181篇
  2021年   50篇
  2020年   32篇
  2019年   50篇
  2018年   68篇
  2017年   54篇
  2016年   40篇
  2015年   53篇
  2014年   94篇
  2013年   118篇
  2012年   190篇
  2011年   204篇
  2010年   96篇
  2009年   108篇
  2008年   182篇
  2007年   188篇
  2006年   165篇
  2005年   154篇
  2004年   162篇
  2003年   137篇
  2002年   144篇
  2001年   168篇
  2000年   146篇
  1999年   120篇
  1998年   52篇
  1997年   50篇
  1996年   44篇
  1995年   44篇
  1994年   39篇
  1993年   53篇
  1992年   79篇
  1991年   76篇
  1990年   65篇
  1989年   66篇
  1988年   58篇
  1987年   54篇
  1986年   39篇
  1985年   56篇
  1984年   28篇
  1983年   34篇
  1982年   26篇
  1981年   30篇
  1980年   27篇
  1979年   36篇
  1978年   28篇
  1975年   20篇
  1974年   29篇
  1973年   28篇
  1972年   24篇
  1971年   23篇
  1966年   20篇
排序方式: 共有3995条查询结果,搜索用时 15 毫秒
11.
12.
The efficacy of subarachnoid injection of 8 ml lidocaine 0.5% was assessed in ten outpatients having perirectal surgery in the jackknife position. This solution is hypobaric, with a baricity 0.9985 +/- 0.0003 (mean +/- SD). Injections were made with the patient in the surgical position (with the upper torso at a 15 degrees downward inclination). Sensory level was tested by pinprick. Times to two-segment regression, to complete resolution of sensory analgesia, to urination, and to discharge from the recovery room were recorded. All injections produced effective anaesthesia for surgery. Lidocaine 0.5% behaves clinically as a hypobaric solution. Dermatomal levels remained low (T11 to L5) while the patients were in the surgical position (head down), but rose two to six dermatomes if the patient's head was elevated after surgery. Time to two-segment regression was 97 +/- 36 min, time until regression to S1 was 116 +/- 22 min, time to complete resolution of sensory blockade was 151 +/- 23 min, time to urination was 197 +/- 64 min, and time to discharge from the recovery room was 205 +/- 45 min. Lidocaine 0.5% provides effective spinal anaesthesia of short duration appropriate for outpatient surgical procedures. Dermatomal sensory spread of anaesthesia, and our measurements of specific gravity, indicate that this solution is hypobaric. It appears that changes in position can alter the spread of analgesia for at least one hour after injection and, thus, we caution against elevating the patient's head in the immediate postoperative period.  相似文献   
13.
We report on a case of keratoconus in identical twins who were brought up in Christchurch, New Zealand. Videokeratoscopy using an EyeSysa (EyeSys Laboratories, Houston, Texas, USA) revealed not only marked differences in severity of keratoconus between the sisters, but also non-equivalent cone types. Both twin sisters reported an exacerbation of their keratoconus during pregnancy and during breast feeding. Various factors affecting the development and progression of keratoconus are discussed. (Clin Exp Optom 1995; 78: 4: 125–129)  相似文献   
14.
15.
This article is an overview of the promotion function as a part of the ATM's marketing mix. It approaches various promotion decision areas from a managerial perspective, focusing upon some key components of promotion planning. Rather than provide specific operational or implementation details (how to write a brochure) it is more conceptual in nature and offers a framework for promotion planners. The article addresses promotion management, promotion objectives, analysis for promotion planning, the promotion mix, and addresses the benefits and limitations of some specific promotion tools available to the ATM manager. It treats ATMs as a service and reveals specific implications for promotion strategy dictated by services. The article also reports promotion tools employed by Alabama ATMs citing data from the Alabama study.  相似文献   
16.
A role in hemostasis has been suggested for platelet membrane microvesicles (mv). The objectives of the studies reported here include functional analysis of platelet mv in models developed for study of platelet adhesion, as well as investigation of possible interactions between mv and intact platelets in these same adhesion models. Microvesicles were prepared from washed platelet concentrates by repeated freezing and thawing. Adhesion to subendothelium was measured quantitatively by radiolabelling mv with 111-In, and morphologically by scanning electron microscopy. Platelet mv adhered to subendothelium quantitatively over time. Using a modified Baumgartner chamber, we found adhesion of mv to subendothelium significantly increased with increasing shear rates. With this same model we found that prior exposure of subendothelium to mv greatly increased subsequent adhesion of platelets to the same everted vessel, compared to platelet adhesion in the absence of mv. All of these experiments were conducted with mv suspended in ACD/saline, indicating that plasma components are not essential for adhesion of mv. Our studies show that platelet mv adhere to subendothelium in much the same way as do platelets, and support the concept of a hemostatic role for mv in that they appear to increase platelet adhesion.  相似文献   
17.
The Liverpool Congenital Malformations Registry   总被引:1,自引:0,他引:1  
Data collection and validation for the Liverpool Congenital Malformations Registry (LCMR) are described. Founded in 1960, the LCMR increased its area of surveillance in 1979 to include five health districts in Liverpool and its environs with approximately 20,000 births per annum. The LCMR is now one of the members of the European Congenital Anomalies Register (EUROCAT). Multiple sources of ascertainment are employed, the most useful of these being OPCS notifications, hospital discharge letters and data from specialised paediatric units. In spite of several difficulties encountered in data collection the data base is an invaluable tool both for routine monitoring of prevalence rates and as a starting point for epidemiological research.  相似文献   
18.
Changes in plasma catecholamines, lipoproteins and dietary intake were examined in 13 medical students during a 3-month period prior to their examinations, and in 12 controls. In the medical students mean +/- s.e.(mean) plasma cholesterol increased over the study period (3.98 +/- 0.16 v. 4.26 +/- 0.16 mmol/l, P less than 0.05) and this was reflected by a rise in low-density lipoprotein cholesterol (2.53 +/- 0.15 v. 2.71 +/- 0.17 mmol/l, P less than 0.05). Both supine adrenaline (0.45 +/- 0.05 v. 0.70 +/- 0.07 nmol/l, P less than 0.01) and noradrenaline (2.74 +/- 0.18 v. 3.40 +/- 0.31 nmol/l, P less than 0.05) increased over this period. Apart from a decline in the modest alcohol consumption (9.1 +/- 3.45 v. 2.6 +/- 1.4 g/day, P less than 0.02) there was no change in dietary intake in the medical students. There were no significant changes in plasma catecholamines, lipoproteins or dietary intake in control subjects over the study period. Changes in catecholamines and lipoproteins occurring in association with chronic psychological stress may contribute to the increased coronary heart disease mortality associated with Type A behaviour and stressful life events.  相似文献   
19.
We have characterized the localization and the ontogenetic changes in Neuropeptide tyrosine (NPY) before birth and investigated the regulation of NPY expression by cortisol and undernutrition in the fetal sheep hypothalamus during late gestation. Using immunohistochemistry, we have identified NPY-containing neurons in the infundibular nucleus and the internal layer of the median eminence in fetal hypothalami collected between 110 and 147 days gestation. NPY projections were also present in the paraventricular nucleus (PVN) of fetal hypothalami at all ages between 110 days gestation and term. There was a significant increase in the amount of immunoreactive NPY/g hypothalamus between 87 and 113 days and 131–140 days gestation and a further significant increase after 141 days gestation. The total hypothalamic content of immunoreactive NPY increased significantly between 87 and 113 days and 141–145 days gestation. The levels of NPY mRNA: 18S rRNA in the mediobasal region of the fetal hypothalamus were significantly higher at 145–146 days gestation than at any earlier gestational age between 116 and 141 days gestation. Cortisol (2.5–3.0 mg/24 h) was infused intrafetally between 109 and 116 days gestation. The ratio of NPY mRNA: 18s rRNA in the mediobasal region of the fetal hypothalamus was significantly higher in the cortisol-infused group when compared with the saline-infused control group at 116 days gestation. Maternal, and hence fetal undernutrition, was induced between 110 and 146 days gestation. At 145–146 days gestation the ratio of NPY mRNA: 18S rRNA in the mediobasal region of the fetal hypothalamus was significantly higher in the undernutrition group when compared with control animals. We have therefore demonstrated that NPY is present in the hypothalamus of the sheep fetus before birth and that hypothalamic NPY content and NPY mRNA increase before delivery. We have also found that glucocorticoids and undernutrition stimulate increases in NPY mRNA levels in the hypothalamus before birth.  相似文献   
20.
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