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   1419108篇
  免费   114133篇
  国内免费   3360篇
耳鼻咽喉   18427篇
儿科学   46888篇
妇产科学   41301篇
基础医学   202052篇
口腔科学   37816篇
临床医学   127298篇
内科学   285809篇
皮肤病学   33506篇
神经病学   117785篇
特种医学   54035篇
外国民族医学   464篇
外科学   211220篇
综合类   32811篇
现状与发展   3篇
一般理论   499篇
预防医学   110849篇
眼科学   31631篇
药学   99022篇
  1篇
中国医学   3357篇
肿瘤学   81827篇
  2021年   11025篇
  2019年   11852篇
  2018年   16822篇
  2017年   12835篇
  2016年   14463篇
  2015年   16223篇
  2014年   22845篇
  2013年   33826篇
  2012年   45972篇
  2011年   48516篇
  2010年   28502篇
  2009年   27342篇
  2008年   44917篇
  2007年   47399篇
  2006年   47915篇
  2005年   46425篇
  2004年   44223篇
  2003年   42145篇
  2002年   40601篇
  2001年   73096篇
  2000年   74594篇
  1999年   61635篇
  1998年   17091篇
  1997年   15515篇
  1996年   15665篇
  1995年   14871篇
  1994年   13454篇
  1993年   12635篇
  1992年   45877篇
  1991年   43522篇
  1990年   41529篇
  1989年   39585篇
  1988年   36212篇
  1987年   35380篇
  1986年   32894篇
  1985年   31320篇
  1984年   23861篇
  1983年   20053篇
  1982年   12230篇
  1981年   10811篇
  1979年   20724篇
  1978年   14600篇
  1977年   12102篇
  1976年   11388篇
  1975年   11631篇
  1974年   14000篇
  1973年   13544篇
  1972年   12648篇
  1971年   11481篇
  1970年   10921篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
991.
OBJECTIVE: To estimate the gestational age ranges that result in optimal birth outcomes for each of four risk-defined groups. STUDY DESIGN: Retrospective cohort study of singleton late third-trimester deliveries at a large urban teaching hospital between July 1995 and September 2003. Low-risk, advanced maternal age, hypertensive and diabetic patients were identified and grouped. Rates, by day of gestation at delivery, of cesarean delivery, major maternal perineal trauma, low 5-min APGAR score and NICU admission were determined for each study group. RESULTS: Each study group had meaningful changes in rates of obstetric outcomes as a function of gestational age at delivery and these patterns differed from group to group. A unique optimal time of delivery (OTD) was estimated for each group. The low-risk group OTD was calculated to be 37 weeks 1 day to 41 weeks 0 day; the advanced maternal age group OTD was 38 weeks 5 days to 39 weeks 6 days; the hypertension group OTD was 39 weeks 2 days to 40 weeks 1 day; and the diabetes mellitus group OTD was 40 weeks 3 days to 41 weeks 1 day. CONCLUSIONS: The OTD varied based on obstetrical risk. Strategies to increase the proportion of deliveries that occur within the OTD for specific risk-defined groups could theoretically improve birth outcomes.  相似文献   
992.
Introduction     
Raymond C. Read 《Hernia》2006,10(6):454-455
  相似文献   
993.
994.
The risks of viral transmission from trauma patients is a continuing concern to those involved in their care. However, the prevalence of hepatitis (HPT) in trauma patients is poorly described. The purpose of this study is to evaluate the prevalence of HPT in trauma patients admitted to an urban trauma center. Two hundred sixty-four consecutive admissions to an urban Level I trauma center underwent serologic screening for HPT. Risk factors were assessed by direct patient questioning. Serologic evidence of HPT B was found in 19.7 per cent of patients. Intravenous (IV) drug abusers represented eight per cent of the study population; this group had a 67 per cent rate of seropositivity. Hepatitis A was not found in any patient. Antigenemia was found in 1.9 per cent of patients. It is concluded that HPT B seropositivity is common in trauma patients. IV drug abusers have particularly high prevalence of HPT. This high prevalence rate of HPT B serology poses a significant risk to those involved with the care of trauma patients. The authors suggest that specific protocols to avoid the transmission of viral disease should be mandatory in urban trauma centers.  相似文献   
995.
New long-acting beta 2-adrenoceptor agonists, formoterol and salmeterol, may soon appear in several European countries for treatment of asthma. This review examines currently available information and compares the basic pharmacology and describes the clinical effects of these new drugs. The long duration of bronchodilation seen in clinical studies seems to be similar, whereas in isolated tissues there might be a difference in the binding characteristics to the beta 2-adrenoceptor. Long-acting beta 2-agonists could have an inhibitory effect on inflammatory events related to asthma, but the clinical relevance of these effects is not clear at present. Long-term studies up to one year with both new drugs have not shown any unexpected side-effects, and no tachyphylaxis to beta-adrenoceptor stimulation has been reported. Patients appear to strongly prefer the new drugs compared to the short-acting beta 2-agonists. The potential place for these drugs in the treatment of asthma is discussed and some pitfalls pointed out. It is likely that the long-acting beta 2-agonists will be beneficial to many asthmatic patients.  相似文献   
996.
997.
998.
ABSTRACT. Funclional behaviours in relation to age were investigated using data from approximately 3000 people on the Wessex Mental handicap Register. The main functional data on the register, the National Development Team's 24-item questionnaire, were cluster and factor analysed to derive a series of client-defining variables. Age-trends were analysed in relation to self and commiiniiy care skills (activities of daily living and instrumental activities of daily living), problem behaviours, chronic medical conditions, mobility and sensory abilities. Generally, it was found that differential mortality leads to an older population In gtwd health and with a high level of functional skills. As with ihe general population, however, people over 70 years old show increasing prevalence of age-related infirmities.  相似文献   
999.
Caregiving: an emerging risk factor for emotional and physical pathology   总被引:1,自引:0,他引:1  
Caregiving is the act of attending to someone or of providing services to an individual in need. It is a complex activity, with ethical, psychosocial, and demographic dimensions, as well as clinical, technical, and community service components. The author describes the complexities of caregiving and the burdens on the family in a rapidly aging society. He points out that caregiving is associated with significant risk for psychopathology and that a more comprehensive approach to the evaluation and management of chronically ill patients is necessary.  相似文献   
1000.
We measured somatosensory evoked magnetic fields during median nerve stimulation in 6 normal subjects. We applied multiple dipole models to study the spatiotemporal structure of early somatosensory evoked magnetic fields (SEFs), as well as the number, 3-dimensional location and time activity of their underlying neuronal sources. Two dipole sources were necessary to model the first 40 msec of SEFs explaining 85% of the data variance. Source 1 was located deeper than source 2, showed primarily a tangential orientation, and accounted for a larger part of the variance; source 2 showed no consistent orientation across subjects. Both sources showed biphasic time activities corresponding to the previously described N20-P30 and P25-N35 components. Spatiotemporal modeling could identify sources which could not be modeled consistently above noise by single moving dipoles (P25 component), revealed small latency differences of the two sources in some subjects suggesting parallel activation of these sources, and allowed separation of sources overlapping considerably both in space and time. We conclude that spatiotemporal modeling of SEFs may be useful to study functional anatomy of human sensorimotor cortex non-invasively.  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