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   2476762篇
  免费   180067篇
  国内免费   3832篇
耳鼻咽喉   33554篇
儿科学   79217篇
妇产科学   64877篇
基础医学   364884篇
口腔科学   66676篇
临床医学   224278篇
内科学   483110篇
皮肤病学   54387篇
神经病学   197471篇
特种医学   93668篇
外国民族医学   500篇
外科学   373283篇
综合类   49190篇
现状与发展   12篇
一般理论   944篇
预防医学   192407篇
眼科学   56997篇
药学   183403篇
  11篇
中国医学   4776篇
肿瘤学   137016篇
  2021年   21595篇
  2019年   21978篇
  2018年   29897篇
  2017年   22595篇
  2016年   25249篇
  2015年   28447篇
  2014年   39997篇
  2013年   59507篇
  2012年   82755篇
  2011年   87983篇
  2010年   52117篇
  2009年   49333篇
  2008年   82355篇
  2007年   87551篇
  2006年   88305篇
  2005年   85758篇
  2004年   81743篇
  2003年   78531篇
  2002年   75947篇
  2001年   110384篇
  2000年   112829篇
  1999年   95132篇
  1998年   28493篇
  1997年   24895篇
  1996年   25152篇
  1995年   23714篇
  1994年   21785篇
  1993年   20554篇
  1992年   73053篇
  1991年   71036篇
  1990年   69265篇
  1989年   66478篇
  1988年   61089篇
  1987年   59850篇
  1986年   55980篇
  1985年   53758篇
  1984年   40072篇
  1983年   34102篇
  1982年   20635篇
  1979年   36441篇
  1978年   26197篇
  1977年   21690篇
  1976年   20781篇
  1975年   22189篇
  1974年   26585篇
  1973年   25198篇
  1972年   23576篇
  1971年   22325篇
  1970年   20525篇
  1969年   19530篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Abstract It is well established that thrombolytic therapy increases the risk of secondary intracerebral hemorrhage in ischemic stroke patients. However, the term “intracerebral hemorrhage” (ICH) covers a wide spectrum from tiny spots of blood to massive space-occupying hematoma. We will review the etiology and clinical consequences of secondary hemorrhage after thrombolysis in ischemic stroke patients and discuss the ability of magnetic resonance imaging (MRI) to predict this phenomenon. MRI is a highly sensitive tool for detection of hemorrhagic transformation after ischemic stroke. The definitions of a so-called symptomatic hemorrhage after ischemic infarction differ considerably and will also be described. Attributing a causal relationship of a clinical deterioration to a secondary hemorrhage is not easy and should be only addressed when it exceeds at least 30% of the infarct volume. In other patients, secondary hemorrhage might be regarded as side effect of reperfusion within the region with the most severe perfusion deficit. Cerebral microbleeds (CMBs) are a frequent finding in patients with leukoaraiosis and appear to be a general marker of various types of bleeding- prone small vessel disease and a predictor of recurrent vascular events. Current data do not support the hypothesis that the detection of CMBs is a useful diagnostic criterion for the exclusion of patients with CMBs from thrombolytic therapy. However, an increased risk for the rare patients with numerous CMBs can not be ruled out.   相似文献   
102.
103.
104.
Background: Few studies have examined the use of ultrasound for sciatic nerve localization. The authors evaluated the usefulness of low-frequency ultrasound in identifying the sciatic nerve at three locations in the lower extremity and in guiding needle advancement to target before nerve stimulation.

Methods: In this prospective observational study, 15 volunteers underwent sciatic nerve examination using a curved ultrasound probe in the range of 2-5 MHz and a Philips-ATL 5000 unit (ATL Ultrasound, Bothell, WA) in the gluteal, infragluteal, and proximal thigh regions. Thereafter, an insulated block needle was advanced inline with the ultrasound beam to reach the nerve target, which was further confirmed by electrical stimulation. The quality of sciatic nerve images, ease of needle to nerve contact, threshold stimulating current, and resultant motor response were recorded.

Results: The sciatic nerve was successfully identified in the transverse view as a solitary predominantly hyperechoic structure on ultrasound in all of the three regions examined. The target nerve was visualized easily in 87% and localized within two needle attempts in all patients. Nerve stimulation was successful in 100% after two attempts with a threshold current of 0.42 +/- 0.12 (mean +/- SD) eliciting foot plantarflexion or dorsiflexion.  相似文献   

105.
106.
Abstract  The discipline of nursing is still struggling with the differences that need to be clearly defined between the notions of care and nursing care. To be able to clarify this distinction, agreement must first be reached on the meaning of care itself. The present article proposes a conception of care in light of the philosophy of Emmanuel Levinas (1906–1995). This philosopher's thought throws considerable light on the ontology of care, thanks especially to his focus on the deeper implications of human encounter. A profound sense of responsibility towards the other enables Levinas to bring out such dimensions of the concept of care as the relation involved, the feeling of affection, and the interventions. We examine here what these entail regarding nursing care.  相似文献   
107.
108.
109.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  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