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   2487篇
  免费   151篇
  国内免费   13篇
耳鼻咽喉   12篇
儿科学   136篇
妇产科学   33篇
基础医学   322篇
口腔科学   42篇
临床医学   250篇
内科学   489篇
皮肤病学   56篇
神经病学   270篇
特种医学   215篇
外国民族医学   1篇
外科学   243篇
综合类   119篇
一般理论   1篇
预防医学   221篇
眼科学   26篇
药学   147篇
中国医学   7篇
肿瘤学   61篇
  2021年   37篇
  2019年   35篇
  2018年   35篇
  2017年   30篇
  2016年   41篇
  2015年   69篇
  2014年   52篇
  2013年   84篇
  2012年   100篇
  2011年   96篇
  2010年   70篇
  2009年   62篇
  2008年   85篇
  2007年   101篇
  2006年   75篇
  2005年   90篇
  2004年   89篇
  2003年   82篇
  2002年   93篇
  2001年   71篇
  2000年   67篇
  1999年   60篇
  1998年   44篇
  1997年   58篇
  1996年   54篇
  1995年   43篇
  1994年   29篇
  1993年   29篇
  1992年   42篇
  1991年   50篇
  1990年   48篇
  1989年   71篇
  1988年   58篇
  1987年   56篇
  1986年   50篇
  1985年   39篇
  1984年   44篇
  1983年   36篇
  1982年   24篇
  1981年   22篇
  1980年   16篇
  1979年   31篇
  1978年   23篇
  1977年   24篇
  1976年   30篇
  1975年   15篇
  1974年   20篇
  1973年   29篇
  1972年   19篇
  1971年   17篇
排序方式: 共有2651条查询结果,搜索用时 15 毫秒
71.
This report is on a 14-month-old boy with manifestations of Opitz (G/BBB) syndrome in whom a 22q11.2 deletion was found. Deletion analysis was requested because of some findings in this patient reminiscent of velocardiofacial (VCF) syndrome. The extent of aspiration and of respiratory symptoms in this child is not usually seen in VCF syndrome. Opitz syndrome maps to at least two loci, one on Xp, the other on 22q11.2. © 1996 Wiley-Liss, Inc.  相似文献   
72.
A taxometric method for diagnosis of drug-induced tardive dyskinesia is described. The method, using items from the Abnormal Involuntary Movement Scale (AIMS) as indicators of the syndrome, is applied in a sample of children diagnosed earlier as autistic and participating in an ongoing treatment program. The method includes procedures for estimation of the prevalence rate of the syndrome and the valid positive and false positive rates for each indicator of the syndrome and it includes tests (referred to as "consistency tests") for checking the internal validity or goodness-of-fit of the statistical model. The agreement of the taxometric classification with that obtained by using criteria suggested by Schooler and Kane was very good. In general, the results were encouraging enough to warrant further study of this kind of method for the detection and diagnosis of tardive dyskinesia.  相似文献   
73.
Sir William Osler's angina pectoris and other disorders   总被引:1,自引:0,他引:1  
  相似文献   
74.
75.
马骁  卡索  刘成  李丹  刘守应  王永成 《中国骨伤》2012,25(4):338-340
目的:探讨前后路联合手术治疗髋臼双柱骨折的效果并分析影响疗效的相关因素。方法:2007年8月至2009年7月收治髋臼双柱骨折患者19例,男13例,女6例;年龄27~52岁,平均39.6岁。高位双柱骨折11例,低位双柱骨折8例,双柱骨折累及骶髂关节1例。受伤至手术时间4~11 d,平均5.8 d。患者均采用前后联合入路手术,重建钢板和螺钉内固定。结果:除1例死亡外本组全部获随访,随访时间12~18个月,平均13.6个月。关节功能根据Harris评分标准,术后功能优9例,良7例,可2例。结论:经前后路联合切开复位内固定治疗髋臼双柱骨折疗效满意。  相似文献   
76.
Resonating circadian clocks enhance fitness in cyanobacteria   总被引:24,自引:1,他引:24       下载免费PDF全文
In some organisms longevity, growth, and developmental rate are improved when they are maintained on a light/dark cycle, the period of which “resonates” optimally with the period of the endogenous circadian clock. However, to our knowledge no studies have demonstrated that reproductive fitness per se is improved by resonance between the endogenous clock and the environmental cycle. We tested the adaptive significance of circadian programming by measuring the relative fitness under competition between various strains of cyanobacteria expressing different circadian periods. Strains that had a circadian period similar to that of the light/dark cycle were favored under competition in a manner that indicates the action of soft selection.  相似文献   
77.
BackgroundAdult imaging for blunt cerebrovascular injuries (BCVI) is based on the Denver and Memphis screening criteria where CT angiogram (CTA) is performed for any one of the criteria being positive. These guidelines have been extrapolated to the pediatric population. We hypothesize that the current adult criteria applied to pediatrics lead to unnecessary CTA in pediatric trauma patients.Study designAt our center, a 9-year retrospective study revealed that strict adherence to the Denver and Memphis criteria would have resulted in 332 unnecessary CTAs out of 2795 trauma patients with only 0.3% positive for BCVI. We also conducted a retrospective chart review of 776,355 pediatric trauma patients in the National Trauma Data Bank (NTDB) from 2007 to 2014. Data collection included children between ages 0 and 18, ICD-9 search for blunt cerebrovascular injury, and ICD-9 codes that applied to both Denver and Memphis criteria.ResultsOf 776,355 pediatric trauma activations, 81,294 pediatric patients in the NTDB fit the Denver/Memphis criteria for screening CTA neck or angiography based on ICD-9 codes, while only 2136 patients suffered BCVI. Strict utilization of the Denver/Memphis criteria would have led to a negative CTA in 79,158 (97.4%) patients. Multivariate regression analysis indicates that patients with skull base fracture, cervical spine fractures, cervical spine fracture with cervical cord injury, traumatic jugular venous injury, and cranial nerve injury should be considered part of the screening criteria for BCVI.ConclusionOur study suggests the Denver and Memphis criteria are inadequate screening criteria for CTA looking for BCVI in the pediatric blunt trauma population. New criteria are needed to adequately indicate the need for CT angiography in the pediatric trauma population.Level of evidenceIV.  相似文献   
78.
79.
G Caughey  H Wong  G Gamsu  J Golden 《Chest》1985,88(5):659-662
We compared conventional bronchoscopic transbronchial biopsy (TBB) and bronchoalveolar lavage (BAL) with non-bronchoscopic bronchoalveolar lavage (NB-BAL) in nine patients with acquired immunodeficiency syndrome (AIDS) and bilateral lung infiltrates. NB-BAL was carried out with a control-tipped reusable catheter. In each patient, bronchoscopic procedures were performed in the right lung, followed immediately by NB-BAL in the left lung. The specimens obtained by NB-BAL confirmed the presence of P carinii pneumonia in seven of eight patients in whom the diagnosis was established by TBB or BAL. Viral cultures of NB-BAL specimens yielded cytomegalovirus (CMV) in four of five subjects with evidence of CMV via bronchoscopic technique, including two instances in which CMV was not detected by BAL. Complications were limited to right-sided pneumothorax attributable to TBB. Accuracy of NB-BAL appears to be comparable to that of conventional bronchoscopic approaches in the diagnosis of AIDS-related pulmonary infection with P carinii or CMV. NB-BAL may be a safer and more economical alternative to TBB and BAL in the diagnosis of pulmonary opportunistic infections.  相似文献   
80.

Background

On more and more websites, consumers are provided with public reports about health care. This move toward provision of more comparative information has resulted in different information types being published that often contain contradictory information.

Objective

The objective was to assess the current state of the art in the presentation of online comparative health care information and to compare how the integration of different information types is dealt with on websites. The content analysis was performed in order to provide website managers and Internet researchers with a resource of knowledge about presentation formats being applied internationally.

Methods

A Web search was used to identify websites that contained comparative health care information. The websites were systematically examined to assess how three different types of information (provider characteristics and services, performance indicators, and health care user experience) were presented to consumers. Furthermore, a short survey was disseminated to the reviewed websites to assess how the presentation formats were selected.

Results

We reviewed 42 websites from the following countries: Australia, Canada, Denmark, Germany, Ireland, the Netherlands, Norway, the United Kingdom, the United States, and Sweden. We found the most common ways to integrate different information types were the two extreme options: no integration at all (on 36% of the websites) and high levels of integration in single tables on 41% of the websites). Nearly 70% of the websites offered drill down paths to more detailed information. Diverse presentation approaches were used to display comparative health care information on the Internet. Numbers were used on the majority of websites (88%) to display comparative information.

Conclusions

Currently, approaches to the presentation of comparative health care information do not seem to be systematically selected. It seems important, however, that website managers become aware of the complexities inherent in comparative information when they release information on the Web. Important complexities to pay attention to are the use of numbers, the display of contradictory information, and the extent of variation among attributes and attribute levels. As for the integration of different information types, it remains unclear which presentation approaches are preferable. Our study provides a good starting point for Internet research to further address the question of how different types of information can be more effectively presented to consumers.  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