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   348502篇
  免费   12671篇
  国内免费   705篇
耳鼻咽喉   3578篇
儿科学   11376篇
妇产科学   6393篇
基础医学   39152篇
口腔科学   5060篇
临床医学   29424篇
内科学   67930篇
皮肤病学   3433篇
神经病学   33847篇
特种医学   14868篇
外国民族医学   13篇
外科学   54420篇
综合类   4594篇
现状与发展   3篇
一般理论   201篇
预防医学   30846篇
眼科学   7451篇
药学   20688篇
中国医学   826篇
肿瘤学   27775篇
  2023年   697篇
  2022年   1220篇
  2021年   2863篇
  2020年   1763篇
  2019年   2895篇
  2018年   24894篇
  2017年   19431篇
  2016年   21916篇
  2015年   4310篇
  2014年   5857篇
  2013年   8573篇
  2012年   18075篇
  2011年   32627篇
  2010年   25058篇
  2009年   17489篇
  2008年   30434篇
  2007年   33340篇
  2006年   12239篇
  2005年   14171篇
  2004年   14760篇
  2003年   15177篇
  2002年   12991篇
  2001年   1732篇
  2000年   1512篇
  1999年   1737篇
  1998年   2515篇
  1997年   2211篇
  1996年   1781篇
  1995年   1676篇
  1994年   1507篇
  1993年   1405篇
  1992年   1075篇
  1991年   1033篇
  1990年   945篇
  1989年   888篇
  1988年   886篇
  1987年   757篇
  1986年   858篇
  1985年   944篇
  1984年   1243篇
  1983年   1196篇
  1982年   1661篇
  1981年   1513篇
  1980年   1455篇
  1979年   791篇
  1978年   915篇
  1977年   803篇
  1976年   716篇
  1975年   571篇
  1974年   614篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
BACKGROUND: Psychotic symptoms in Alzheimer disease (AD+P) identify a heritable phenotype associated with more rapid cognitive decline. The authors have proposed that AD+P is itself a composite of a misidentification and a paranoid subtype with increased cognitive impairment restricted to the misidentification type. Most prior studies of the clinical correlates of AD+P have been limited, however, by the inclusion of prevalent cases. METHODS: Subjects with possible or probable AD or mild cognitive impairment (MCI) without psychosis at study entry were assessed at the time of initial presentation and then annually. Psychotic symptoms were assessed using the CERAD Behavioral Rating Scale. Survival analyses used Cox proportional hazard models with time-dependent covariates to examine the predictors of psychosis onset. RESULTS: A total of 288 subjects completed at least one follow-up examination. Mean duration of follow-up was 22.1 months. The incidence of psychosis was 0.19 per person-year. Cognitive impairment was associated with onset of psychosis, largely as a result of its association with onset of the misidentification, but not the paranoid, subtype. Including psychotropic medication use in the model revealed an association of antidepressant use with the onset of psychosis. This latter association appeared to arise from an underlying association between depression and the risk of psychosis onset rather than from antidepressant treatment. CONCLUSION: These findings are consistent with the hypothesis that the misidentification and the paranoid subtypes each define a more biologically homogeneous group than AD+P as a whole. Further exploration of the relationship between depressive symptoms and psychosis in patients with AD is warranted.  相似文献   
85.
We assessed midsagittal corpus callosum size in sickle cell disease (SCD) and its relationship to lesion volume, lesion location, and cognitive functioning. Twenty-eight children with SCD and 16 demographic controls completed magnetic resonance imaging (MRI) and neuropsychological testing. Corpus callosum (CC) size was smaller for children with silent infarcts (n = 8) or overt stroke (n = 8) than for those without visible infarcts (n = 12) or control participants. Lesion volume was a robust predictor of IQ and other cognitive scores; total CC size did not typically add explanatory power for these measures. The size of the rostral body of the CC, however, independently predicted measures of distractibility, speeded production, and working memory. Posterior CC size was also decreased among many of the children with SCD, even in the absence of visible infarcts in this region. Brain morphology appears to provide additional information about SCD-related effects on the brain above and beyond visible infarcts.  相似文献   
86.
87.
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   
88.
89.
90.
BACKGROUND: Little is known about the health-related quality of life (HRQOL) of nonclinical samples of people with irritable bowel syndrome (IBS) in Canada. In a pilot survey, the impact of IBS on HRQOL using a population-based, urban sample was examined. METHODS: A random sample of Calgary residents (18 years of age or older), selected by random digit dialing (n=1521), completed a structured questionnaire including ROME II Criteria and Medical Outcomes Study Short-Form 12-Item Health Survey, version 2 (SF-12v2). The mean scale and summary scores of SF-12v2 for those who did and did not meet ROME II criteria and for those who met ROME II criteria with and without visiting a physician in past three months were determined and compared using multiple regression analyses. RESULTS: Of the 951 households successfully contacted, 590 (62%) were willing to participate, of which 437 (74%) individuals were recruited. One hundred ten IBS cases (81 of which were women) and 327 non-IBS controls (180 of which were women) were identified. All of the eight mean scale scores and the two mean summary scores were significantly lower in people with IBS than in those without, whether or not adjusting for demographics. Forty-four of the 110 IBS cases (40%) sought medical help. Significantly lower mean physical component score and three scale scores (general health, social functioning and role physical) were found in those who sought medical help than in those who did not. CONCLUSIONS: People with IBS experience significant impairment in HRQOL, including both physical and mental well-being. People with IBS who seek medical help report worse physical health than those who do not, but their mental health is no different.  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