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   3080487篇
  免费   249496篇
  国内免费   16676篇
耳鼻咽喉   41778篇
儿科学   90550篇
妇产科学   76374篇
基础医学   499344篇
口腔科学   80830篇
临床医学   273896篇
内科学   535072篇
皮肤病学   85179篇
神经病学   266792篇
特种医学   121460篇
外国民族医学   121篇
外科学   481545篇
综合类   94519篇
现状与发展   30篇
一般理论   2236篇
预防医学   247313篇
眼科学   71046篇
药学   214441篇
  23篇
中国医学   11466篇
肿瘤学   152644篇
  2022年   25617篇
  2021年   59160篇
  2020年   37139篇
  2019年   60879篇
  2018年   74086篇
  2017年   56303篇
  2016年   62916篇
  2015年   78451篇
  2014年   113557篇
  2013年   179862篇
  2012年   97489篇
  2011年   95399篇
  2010年   120405篇
  2009年   124657篇
  2008年   78798篇
  2007年   80766篇
  2006年   90717篇
  2005年   85585篇
  2004年   86075篇
  2003年   75936篇
  2002年   65000篇
  2001年   81834篇
  2000年   73260篇
  1999年   77963篇
  1998年   63859篇
  1997年   61932篇
  1996年   58869篇
  1995年   54318篇
  1994年   48375篇
  1993年   45265篇
  1992年   50545篇
  1991年   47076篇
  1990年   43711篇
  1989年   44121篇
  1988年   40748篇
  1987年   39570篇
  1986年   37353篇
  1985年   38018篇
  1984年   37483篇
  1983年   35164篇
  1982年   37915篇
  1981年   35965篇
  1980年   33937篇
  1979年   28478篇
  1978年   27712篇
  1977年   26460篇
  1976年   23545篇
  1975年   21470篇
  1974年   20484篇
  1973年   19505篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
CONTEXT: Although the nonmedical use of stimulant drugs such as cocaine and methamphetamine is increasingly common in many rural areas of the United States, little is known about the health beliefs of people who use these drugs. PURPOSE: This research describes illicit stimulant drug users' views on health and health-related concepts that may affect their utilization of health care services. METHODS: A respondent-driven sampling plan was used to recruit 249 not-in-treatment, nonmedical stimulant drug users who were residing in 3 rural counties in west central Ohio. A structured questionnaire administered by trained interviewers was used to collect information on a range of topics, including current drug use, self-reported health status, perceived need for substance abuse treatment, and beliefs about health and health services. FINDINGS: Participants reported using a wide variety of drugs nonmedically, some by injection. Alcohol and marijuana were the most commonly used drugs in the 30 days prior to the interview. Powder cocaine was used by 72.3% of the sample, crack by 68.3%, and methamphetamine by 29.7%. Fair or poor health status was reported by 41.3% of the participants. Only 20.9% of the sample felt they needed drug abuse treatment. Less than one third of the sample reported that they would feel comfortable talking to a physician about their drug use, and 65.1% said they preferred taking care of their problems without getting professional help. CONCLUSIONS: Stimulant drug users in rural Ohio are involved with a range of substances and hold health beliefs that may impede health services utilization.  相似文献   
994.
995.
OBJECTIVE: To assess the effect of glucose control on the rate of growth of fetuses in women with pregestational diabetes mellitus (Types 1 and 2). METHODS: All pregestational diabetic women booked at Mater Mothers' Hospital, Brisbane, Australia, between 1 January 1994 and 31 December 2002, were included. Pregnancies with congenital fetal anomalies, multiple pregnancies, and pregnancies terminated prior to 20 weeks' gestation were excluded. Dating scans were performed before 14 weeks' gestation and serial scans were performed at 18, 24, 28, 32 and 36 weeks. Fetal parameters, including biparietal diameter, femur length and abdominal circumference, were recorded. The daily growth rates for biparietal diameter, femur length, and fetal abdominal area were calculated and compared with those in a low-risk (non-diabetic) population. The growth rates in fetuses of women with satisfactory diabetic control (HbA1c < 6.5%) and unsatisfactory control (HbA1c > or = 6.5%) in the three trimesters were compared. RESULTS: A total of 174 diabetic pregnancies were included and a total of 997 ultrasound scans were performed. The growth rates for fetuses of mothers with diabetes mellitus were significantly higher than for those in the low-risk population. The z-scores for biparietal diameter, femur length, and fetal abdominal area were 0.18, 0.59 and 1.44, respectively. Fetuses of diabetic mothers with high HbA1c in the first trimester had significantly greater fetal abdominal area growth rate than those with normal HbA1c (fetal abdominal area z-score of 1.7 vs. 0.75, P = 0.009). Although the fetal abdominal area z-scores in fetuses of diabetic mothers with high HbA1c in the second or third trimesters were also higher than those with normal HbA1c levels, the differences did not reach statistical significance. Maternal obesity did not influence the fetal growth rate. CONCLUSION: The rate of growth of fetuses of diabetic mothers differs from that of the normal population. Growth acceleration persists until the late third trimester. Moreover, periconceptional glucose control appears to have a significant effect on accelerated growth of the fetal abdominal area.  相似文献   
996.
997.
科学研究的目标是创造和传播知识。这得通过对系统收集以及报告信息的批判性分析来完成。批判性分析始于一个简单的步骤,即在运用复杂统计学分析方法进行比较之前对所收集的数据进行深入检查。根据所收集的数据类型按照标准化方式进行统计学分析。在为解决研究问题而需采用合理、标准化步骤进行比较时,新知识就产生了,同时要避免错误的结论。在对数据进行仔细检查和分析之后,为了保证结论的正确性,再对数据进行一次批判性评论是非常重要的补充步骤。在科学文献中发表研究成果过程中涉及的同行评价对于传播新知识并保证其质量方面是一个非常重要的步骤。如果没有将研究成果发表供同行参考,这项研究就不算完整。  相似文献   
998.
999.
Carbon monoxide (CO), a byproduct of heme catalysis, was shown to have potent cytoprotective and anti-inflammatory effects. In vivo recipient CO inhalation at low concentrations prevented ischemia/reperfusion (I/R) injury associated with small intestinal transplantation (SITx). This study examined whether ex vivo delivery of CO in University of Wisconsin (UW) solution could ameliorate intestinal I/R injury. Orthotopic syngenic SITx was performed in Lewis rats after 6 h cold preservation in control UW or UW that was bubbled with CO gas (0.1-5%) (CO-UW). Recipient survival with intestinal grafts preserved in 5%, but not 0.1%, CO-UW improved to 86.7% (13/15) from 53% (9/17) with control UW. At 3 h after SITx, grafts stored in 5% CO-UW showed improved intestinal barrier function, less mucosal denudation and reduced inflammatory mediator upregulation compared to those in control UW. Preservation in CO-UW associated with reduced vascular resistance (end preservation), increased graft cyclic guanosine monophosphate levels (1 h), and improved graft blood flow (1 h). Protective effects of CO-UW were reversed by ODQ, an inhibitor of soluble guanylyl cyclase. In vitro culture experiment also showed better preservation of vascular endothelial cells with CO-UW. The study suggests that ex vivo CO delivery into UW solution would be a simple and innovative therapeutic strategy to prevent transplant-induced I/R injury.  相似文献   
1000.
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