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   304046篇
  免费   17858篇
  国内免费   425篇
耳鼻咽喉   4373篇
儿科学   10635篇
妇产科学   10450篇
基础医学   45842篇
口腔科学   7722篇
临床医学   24785篇
内科学   57822篇
皮肤病学   6560篇
神经病学   21543篇
特种医学   11858篇
外国民族医学   43篇
外科学   48042篇
综合类   7790篇
现状与发展   1篇
一般理论   162篇
预防医学   20583篇
眼科学   7110篇
药学   21239篇
中国医学   820篇
肿瘤学   14949篇
  2021年   2428篇
  2019年   2517篇
  2018年   3873篇
  2017年   2845篇
  2016年   3265篇
  2015年   3694篇
  2014年   4861篇
  2013年   7562篇
  2012年   9472篇
  2011年   9934篇
  2010年   6457篇
  2009年   5791篇
  2008年   9043篇
  2007年   9931篇
  2006年   9789篇
  2005年   9350篇
  2004年   9026篇
  2003年   8519篇
  2002年   8099篇
  2001年   13611篇
  2000年   13985篇
  1999年   11663篇
  1998年   3087篇
  1997年   2839篇
  1996年   2685篇
  1995年   2590篇
  1992年   8436篇
  1991年   8556篇
  1990年   8359篇
  1989年   8167篇
  1988年   7367篇
  1987年   7122篇
  1986年   6763篇
  1985年   6560篇
  1984年   4794篇
  1983年   4144篇
  1982年   2484篇
  1979年   4453篇
  1978年   3244篇
  1977年   2738篇
  1976年   2516篇
  1975年   2853篇
  1974年   3369篇
  1973年   3385篇
  1972年   3137篇
  1971年   2966篇
  1970年   2854篇
  1969年   2602篇
  1968年   2557篇
  1967年   2384篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
The purpose of this study was to provide, in a large number of patients, comprehensive Doppler echocardiographic assessment of normal St Jude Medical mitral valve prosthesis function using Doppler-derived hemodynamic variables, including the mitral valve prosthesis-to-left ventricular outflow tract time-velocity integral ratio and prosthesis performance index. The pressure half-time was less than 130 milliseconds in all patients, and all but one patient had either a peak early mitral diastolic velocity of 2 m/s or less or a mitral valve prosthesis-to-left ventricular outflow tract time-velocity integral ratio of less than 2.2. There was a significant (P < .001) negative correlation between the prosthesis performance index and prosthesis size. This negative correlation suggests that there is more efficient use of the in vitro geometric orifice area with smaller prostheses.  相似文献   
103.
Relatives of 22 schizotypal probands were evaluated for lifetime psychiatric diagnoses. Forty-four (N = 44) of the 97 available relatives were interviewed directly using the Diagnostic Interview Schedule. The rates of psychiatric diagnoses were compared with those of sixty-six (N = 66) of 140 relatives of 30 depressed patients. Family history of mental illness was ascertained by the informant method on the remainder of relatives of both proband groups. The rate of depression found in the relatives of schizotypal patients was 52% in those directly interviewed and 25.7% when informants' reports on unavailable relatives are pooled with direct interview data. These rates were not significantly higher than those found for the relatives of depressed probands (34.8% by direct interview and 21% including reports from informants). The high rates of depression in the relatives of schizotypal probands may indicate that schizotypal personality is associated with affective disorder and not only with schizophrenia. However, the high rates may be due to the presence of depressive character traits in relatives, which inflate the rates of dysthymic disorder and other chronic depressive disorders in the relatives of borderline patients.  相似文献   
104.
Results of an examination of 39 patients are described and critically assessed. An analysis of the resolving power of the method of ultrasonic angiography in pathological formations of major vessels of the neck is given.  相似文献   
105.
Reliable discrimination between sinus tachycardia (ST) and pathologic tachycardia has been a major problem for automatic implantable antitachycardia devices. In patients whose sinus response to activity is as rapid or faster than their pathologic tachycardia (rate crossover), these unsophisticated devices deliver the programmed tachycardia response to either the pathologic or sinus tachycardia. Over a one-year period, 50 Intermedics Intertach Model 262–12 antitachycardia pulse generators were implanted to evaluate the specificity of a new group of tachycardia recognition algorithms. Patients were subjected to exercise testing and noninvasive programmed stimulation to demonstrate the efficacy of this new approach. The five recognition algorithms tested were various combinations of the following criteria: high rate HR), sudden onset (SO), rate stability (RS), and sustained high rate (SHR). False positive rates (tachycardia response inappropriately triggered by ST) were as follows: HR (93%); HR + SO (3%); HR + RS (63%); HR + (RS or SHR) (87%); HR + HS + SO (8%). Pair-wise significance testing between HR only and HR + SO (p < 0.001), HR + RS (p = 0.01) and HR + SO + RS (p < 0.001), demonstrated a significant reduction in the rate of false positives through the use of the sudden onset and rate stability criteria in concert with the standard high rate criterion.  相似文献   
106.
107.
108.
109.
OBJECTIVES: The aim was to assess the natural course of oral lichen lesions (OLL) among unselected, non-consulting individuals. SUBJECTS AND METHODS: A cohort of 327 subjects with OLL, confirmed in 1973-1974 during a population-based survey in two Swedish municipalities, was followed through January 2002 via record linkages with nationwide and essentially complete registers. A sample of 80 drawn from the 194 surviving subjects who still resided in the area in 1993-1995 was invited for interview and oral re-examination. RESULTS: At the end of follow-up, one case of oral cancer was detected, while 0.4 were expected. The overall mortality among subjects with OLL was not significantly different from that in the 15,817 OLL-free subjects who participated in the initial population based survey in 1973-1974. The lesion had disappeared in 14 (39%) of 36 re-examined subjects with white OLLs in 1973-1974, and four (11%) had transformed into red types. In the corresponding group of 19 with red forms initially, five (26%) had become lesion free and four (21%) had switched to white types. Although the cohort size does not permit firm conclusions regarding oral cancer risk, the natural course over up to 30 years appears to be benign in the great majority.  相似文献   
110.
Prisons and prison inmates present important targets for HIV/AIDS prevention interventions. Inmates often have histories of high-risk behavior that place them in danger of contracting HIV/AIDS, and rates of HIV/AIDS tend to be much higher in this population. The goal of this study was to assess the effectiveness of a prison-based HIV/AIDS intervention to change attitudes toward HIV prevention, norms supporting HIV prevention, perceived behavioral control (i.e., self-efficacy) for HIV prevention behaviors, and intentions to engage in HIV prevention behaviors postrelease. The intervention also had the goal of encouraging inmates to become HIV/AIDS peer educators. The intervention appeared most successful at influencing beliefs and behaviors related to peer education and somewhat successful at influencing beliefs and intentions related to condom use. Analyses also showed some significant differences in effectiveness by race/ethnicity. Results are discussed from the perspectives of both research and practice with regard to prison-based HIV prevention efforts.  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