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   987篇
  免费   27篇
  国内免费   27篇
教育   590篇
科学研究   205篇
各国文化   1篇
体育   126篇
综合类   85篇
文化理论   5篇
信息传播   29篇
  2023年   1篇
  2022年   19篇
  2021年   37篇
  2020年   29篇
  2019年   17篇
  2018年   9篇
  2017年   14篇
  2016年   12篇
  2015年   32篇
  2014年   69篇
  2013年   66篇
  2012年   75篇
  2011年   70篇
  2010年   60篇
  2009年   42篇
  2008年   51篇
  2007年   68篇
  2006年   61篇
  2005年   63篇
  2004年   49篇
  2003年   36篇
  2002年   33篇
  2001年   33篇
  2000年   17篇
  1999年   15篇
  1998年   14篇
  1997年   13篇
  1996年   14篇
  1995年   6篇
  1994年   7篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1990年   1篇
  1957年   1篇
排序方式: 共有1041条查询结果,搜索用时 0 毫秒
71.
To elucidate a higher rate of premature cardiovascular disease (CVD) in Asian Indian descendants (Roma) in Slovakia, we investigated frequency distribution, correlates and relationship of lipoprotein(a) [Lp(a)] to family CVD risk factors in Roma children and their Caucasian neighbors. The study sample consisted of 607 healthy children aged 7–18 years (55% Roma, 48% male) as part of the biracial (Roma–Caucasian) Slovak Lipid Community Study. Overall, frequency distribution data of Lp(a) were highly skewed to low concentrations, with markedly higher Lp(a) levels in Roma than in Caucasian children (median and range, mg/dL: 14.5; 0–159.2 vs 6.2; 0–112.3, P < 0.001), regardless of age and gender. Lp(a) was positively correlated with apo B (0.159, P = 0.004) in Roma, and LDL cholesterol (0.170, P = 0.005) in Caucasian children. In addition, daily income of the family was negatively related with Lp(a) in Roma (−0.134, P = 0.036) while positively in Caucasians (0.136, P = 0.047). For both race groups, no significant association was found between Lp(a) and age, body mass index, mean arterial pressure, smoking, and physical activity. Also, no significant relationships were examined between serum Lp(a) levels >30 mg/dL in children and family CVD risk factors, except for diabetes mellitus in parents of Caucasian origin (OR 4.46; 95%CI: 1.23–16.20). In a multivariate analysis, daily income, LDL cholesterol or apo B explained ~7% of the variance of Lp(a). This study suggests a significantly higher serum Lp(a) levels in Roma than in Caucasian children and a small effect, in general, of relevant CVD risk factors on the variation of Lp(a) levels in childhood.  相似文献   
72.
侯丽萍  石磊 《科技通报》2012,28(5):159-162,166
根据遗传算法和人工蜂群算法各自特点,在遗传算法框架上,利用人工蜂群算法中跟随蜂选择\搜索策略,代替遗传算法中的变异操作,提出一种基于人工蜂群算法跟随蜂选择\搜索的混合遗传算法,并应用到0-1背包问题中。实验结果表明了该算法的有效性。  相似文献   
73.
通过分析医学留学生的学习特点,总结肾内科专业留学生教学经验,探讨多媒体教学在留学生教学工作的优势,以利于更好地开展留学生教学工作,提高教学质量。  相似文献   
74.
Congenital atresia of the left main coronary artery is a rare occurrence, and surgical revascularizationbypass graft is required. We here report a rare case of congenital coronary anomaly in an infant. A 10-month-old male infant was admitted to the hospital with heart failure symptoms. Echocardiographic examinations revealed mitral valve regurgitation and ischemic changes of the anterolateral papillary muscle and chordae. Coronary angiography showed atresia of the left main coronary artery with a severe hypoplastic left anterior descending artery and a circumflex coronary artery. Unfortunately, sudden cardiac arrest occurred after catheterization and the infant did not recover despite of immediate cardiopulmonary resuscitation. Further studies are needed to find a newer diagnostic method to detect coronary anomaly in an infant, and coronary angiography, if necessary, has to be performed very carefully.  相似文献   
75.
19世纪以前,主权国家通过实施隔离与检疫措施,建设国内公共卫生体系来抗击传染病的侵袭。之后,国际社会则通过寻求国际卫生合作,构建传染病的国际治理机制以控制传染病的扩散。但该体制存在严重缺陷,不能适应传染病全球化的新发展,必须对其不断完善,建立全球卫生治理的新机制。  相似文献   
76.
标准粒子群算法(PSO)容易陷入局部最优解,导致收敛速度慢、效率低.文章结合遗传算法提出了改进的组合粒子群算法,在每次迭代后应用随机函数随机选择下一次迭代所使用的变异策略或交叉策略.由测试数据表明组合粒子群算法在求解TSP时性能上有很大提高.  相似文献   
77.
ABSTRACT

This study operationalized Weick’s [(1988). Enacted sensemaking in crisis situations. Journal of Management Studies 25(4), 305–317 and (1993). The collapse of sensemaking in organizations: The Mann Gulch disaster. Administrative Science Quarterly, 38, 628–652] theory of enacted sensemaking to examine the communication processes associated with the Flint Water Crisis of 2014–2015. A content analysis of 389 emails and attachments from a total population of N?=?37,376 pages of publicly released e-mails and documents pertaining to Flint’s water issues, identified examples of failed sensemaking by government officials. These failures hastened and intensified a growing crisis of lead contamination and an outbreak of Legionnaires disease associated with Flint’s municipal water system. Analysis of email messages suggests that strong commitments by top leaders and limited capacity were important factors as were efforts to create and maintain consensus among officials. The Flint Water Crisis offers an important application of sensemaking theory and its utility for both organizational and risk communication scholars and for practical application. The authors emphasize the importance of questioning previous assumptions and commitments, insuring that communication practitioners are involved in decisions, and avoiding over reliance on image repair as a strategic response.  相似文献   
78.
系统深入地研究了光谱与色谱方法用于有机合成分析,本文依据光谱与色谱方法发现传统合成过程中金属卟啉相互转化问题,并进行了深入探讨,从而改进了合成方法,取得良好结果。  相似文献   
79.
数学期望是随机变量的重要的数字特征之一。本文通过民事纠纷、疾病普查和利润的例子探讨离散型随机变量的数学期望在法律、医学和经济等问题的应用。  相似文献   
80.
从神经生理谈老年性痴呆症的发病机制与疗法   总被引:2,自引:0,他引:2  
从神经生理的角度分析了老年痴呆症的发病机制,认为老年痴呆与胆碱能、单胺能、神经肽能等多种递质和调制物的功能障碍有着直接的联系,提出了根据病因采用中药、西药和康复3大类的治疗方法。  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