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   20225篇
  免费   1274篇
  国内免费   30篇
耳鼻咽喉   200篇
儿科学   724篇
妇产科学   609篇
基础医学   2467篇
口腔科学   173篇
临床医学   3912篇
内科学   3396篇
皮肤病学   342篇
神经病学   1749篇
特种医学   316篇
外科学   1750篇
综合类   160篇
一般理论   34篇
预防医学   2709篇
眼科学   197篇
药学   1308篇
  2篇
中国医学   7篇
肿瘤学   1474篇
  2023年   118篇
  2022年   153篇
  2021年   430篇
  2020年   285篇
  2019年   436篇
  2018年   522篇
  2017年   436篇
  2016年   448篇
  2015年   498篇
  2014年   662篇
  2013年   994篇
  2012年   1505篇
  2011年   1500篇
  2010年   840篇
  2009年   760篇
  2008年   1379篇
  2007年   1506篇
  2006年   1469篇
  2005年   1372篇
  2004年   1347篇
  2003年   1234篇
  2002年   1149篇
  2001年   149篇
  2000年   87篇
  1999年   137篇
  1998年   234篇
  1997年   185篇
  1996年   181篇
  1995年   157篇
  1994年   158篇
  1993年   114篇
  1992年   74篇
  1991年   71篇
  1990年   73篇
  1989年   56篇
  1988年   75篇
  1987年   58篇
  1986年   62篇
  1985年   53篇
  1984年   56篇
  1983年   38篇
  1982年   65篇
  1981年   71篇
  1980年   62篇
  1979年   30篇
  1978年   33篇
  1977年   27篇
  1976年   20篇
  1974年   18篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
991.
OBJECTIVES: This study sought to determine adherence of physicians to tuberculosis (TB) screening guidelines among foreign-born persons living in the United States who were applying for permanent residency. METHODS: Medical forms of applicants from 5 geographic areas were reviewed, along with information from a national physician database on attending physicians. Applicant and corresponding physician characteristics were compared among those who were and were not correctly screened. RESULTS: Of 5739 applicants eligible for screening via tuberculin skin test, 75% were appropriately screened. Except in San Diego, where 11% of the applicants received no screening, most of the inappropriate screening resulted from the use of chest x-rays as the initial screening tool. CONCLUSIONS: Focused physician education and periodic monitoring of adherence to screening guidelines are warranted.  相似文献   
992.
OBJECTIVES: This study examined the relative perceived effectiveness of 30 antidrug public service announcements (PSAs) and assessed the extent to which judgments of effectiveness are related to judgments of realism, amount learned, and positive and negative emotional responses. METHODS: Data were obtained from 3608 students in grades 5 through 12 in 10 schools. The ethnically diverse sample was 50.8% male. Students in 5 experimental conditions viewed sets of 6 antidrug PSAs and filled out a brief evaluation questionnaire following each PSA. Those in the control condition viewed a non-drug-related television program. RESULTS: The relative perceived effectiveness of the 30 PSAs varied considerably. Sixteen were rated as significantly more effective, and 6 as significantly less effective, than the control program. Relative rated effectiveness was highly related to realism (r =.87), amount learned (r =.88), negative emotion (r =.87), and positive emotion (r = -.35). CONCLUSIONS: Evaluative research is necessary to prevent broadcast of PSAs that could have a negative impact. PSAs should point out the negative consequences of drug use behavior rather than telling adolescents to "just say no."  相似文献   
993.
We assessed prospectively the risk of increased incidence of respiratory symptoms after exposure to particular fungal genera in a susceptible population--namely, infants (n = 880) at high risk for developing asthma. Days of wheeze or persistent cough, information on maternal allergy and asthma, socioeconomic variables, and housing characteristics were collected over the course of the infant's first year of life. Exposure to mold was assessed by airborne samples collected at one time early in the infant's life. Fungi were identified to genus level, recorded as colony-forming units per cubic meter (CFU/m3), and then categorized into four levels: 0 (undetectable), 1-499 CFU/m3 (low), 500-999 CFU/m3 (medium), and greater than or equal to 1,000 CFU/m3 (high). Effects of mold on wheeze and persistent cough, adjusting for potential confounding factors, were examined with Poisson regression analyses. The two most commonly found genera were Cladosporium (in 62% of the homes) and Penicillium (41%). Cladosporium was associated with reported mold (p < 0.02) and water leaks (p < 0.003). Rate of persistent cough was associated with reported mold [Rate ratio (RR) = 1.49; 95% CI, 1.18-1.88]. The highest level of Penicillium was associated with higher rates of wheeze (RR = 2.15; 95% CI, 1.34-3.46) and persistent cough (RR = 2.06; 95% CI, 1.31-3.24) in models controlling for maternal history of asthma and allergy, socioeconomic status, season of mold sample, and certain housing characteristics. We conclude that infants in this high-risk group who are exposed to high levels of Penicillium are at significant risk for wheeze and persistent cough.  相似文献   
994.
Previously we reported that vitamin A-deficient (-A) mice had a profound reduction in T helper 2 (Th2) cells, accounting for their depressed T-dependent antibody responses. Providing vitamin A or its active metabolites reversed this defect. The current experiments utilized splenocytes from T cell receptor transgenic mice to investigate how all-trans retinoic acid (atRA) augments Th2 development. These cells were stimulated in vitro in the presence or absence of atRA, with or without exogenous cytokines driving Th1 or Th2 development. Without exogenous cytokines, atRA addition significantly inhibited the interferon (IFN)-gamma response but did not alter the interleukin (IL)-4 response. With Th1 polarizing cytokines, atRA enhanced the IFN-gamma response, with no effect on the IL-4 response. Most importantly, with the Th2 polarizing cytokine IL-4, atRA significantly increased the IL-4 secretion (fivefold) and also increased the Th2 cell frequency twofold. The striking Th2 enhancement was also observed when only antigen-presenting cells were treated with atRA before stimulation of untreated CD4(+) transgenic T cells, but not vice versa. Thus, atRA maximized Th2 cell development in an IL-4-dependent manner, through an effect on antigen-presenting cell function.  相似文献   
995.
996.
997.
OBJECTIVE: To determine the effectiveness of a clinical practice guideline (CPG) on the use of parenteral nutrition (PN) at a tertiary care pediatric hospital. METHODS: Review of prospectively collected data on hospital-wide PN use 2 years before and 5 years after the establishment of the CPG. Effectiveness of the CPG was measured as the percentage of PN courses lasting fewer than 5 days and the number of PN starts per 1000 patient days. RESULTS: During the study period, 5745 PN courses were administered. The mean (SD) number of PN starts per 1000 inpatient days was 8.86 (0.78) before the CPG and 9.54 (2.49) afterwards (p = .28). The percentage courses of PN lasting for fewer than 5 days declined from 26.3% before the CPG to 18.4% afterwards (p < .0001). A multivariate model confirmed that the rate of short-term PN starts declined after the CPG was issued. The mean (SD) number of PN courses shorter than 5 days in the 2 years before the CPG was 2.33 (0.42) per 1000 patient days versus 1.75 (0.45) in the 5 years after the CPG was instituted (p = .005), which is a 25% decline. The services with the highest volume of PN use showed the most significant decreases in short-term PN use. A cost savings to the hospital of more than $50,000 may have been realized. CONCLUSIONS: In a large pediatric tertiary care hospital, a CPG was successfully deployed. CPGs can favorably affect the use rates and costs of parenteral nutrition.  相似文献   
998.
Anxiety and fear   总被引:1,自引:0,他引:1  
OBJECTIVE: We assessed the ability of child and adolescent practitioners to discriminate between anxiety items from the Revised Children's Manifest Anxiety Scale (RCMAS) and fear items from the Fear Survey Schedule for Children-Revised (FSSC-R). In addition, we examined the effects age, gender, nationality, and therapeutic orientation on discrimination ability. METHOD: Child and adolescent psychiatrists and psychologists from two university hospitals in Australia and the USA completed a questionnaire comprised of items randomly chosen from the RCMAS and the FSSC-R. Clinicians rated each item on the extent to which the item represented the construct of anxiety or fear, using a 7-point Likert-type scale. RESULTS: Clinicians were more accurate in their perceptions of anxiety than in their perceptions of fear. Clinicians with a psychodynamic orientation were more likely to perceive an item as describing anxiety, and were less likely to identify fear. There was a significant interaction between age, scale and perception, with the youngest clinicians showing the greatest perceptual differentiation between the fear and anxiety items. CONCLUSIONS: The results suggest a need to develop common terminology among researchers and clinicians, develop scales with items specific to the pathology they intend to measure, and consider the variables influencing the clinicians rating them.  相似文献   
999.
Researchers have suggested that educational attainment and occupational status--indicators of cognitive and/or neurologic "reserve"--can help persons compensate for clinical manifestations of Alzheimer's disease (AD), such as the rates of cognitive and functional decline. The effects of educational attainment on rates of decline could be "direct" independent of occupational status), "indirect" (working through occupational status), or both. We used multilevel analysis for repeated measures to study the effects of educational attainment and occupational status on rates of decline in cognition (Mini-Mental State Examination, MMSE) and function (Cleveland Scale for Activities of Daily Living). Subjects included persons with "probable" or "possible" AD, drawn from our Alzheimer's Disease Research Center registry (N = 482 in the analysis of cognitive decline, and N = 450 in the analysis of functional decline). When controlling for year of birth, gender, ethnicity, and duration of illness, we found that there was an inverse relationship between number of years of education and rate of decline in MMSE, but effects of occupational status were not significant. This implies a "direct" effect of education on decline in MMSE, but no "indirect" effect through occupational status. Neither educational attainment nor occupational status affected rate of decline in functional ability. We conclude that education slows the rate of cognitive decline in persons with AD, but not through its impact on occupational status. Thus, the protective effects of reserve may be established early in life, before people enter the workforce.  相似文献   
1000.
OBJECTIVE: This study examined the lifetime use of alcohol, drug, and mental health treatment services by recently incarcerated women prison inmates. METHODS: A total of 805 women entering a North Carolina prison for new felony charges in 1991 and 1992 were interviewed in person shortly after incarceration. The women were assessed for psychiatric disorders and lifetime use of substance abuse and mental health treatment services. Rates of service use were analyzed by inmate characteristics and were compared with rates for a sample of women in the community in North Carolina. RESULTS: The majority of women inmates reported a history of using substance abuse services or mental health services or both. Those with psychiatric disorders and prison recidivists were the most likely to have used such services. Rates of service use were substantially higher for the inmates than for the women in the community, even when the effects of having a psychiatric or substance use disorder were controlled for. CONCLUSIONS: Many of the incarcerated women in the study met lifetime criteria for alcohol, drug, and mental health disorders that were significantly related to their use of substance abuse and mental health treatment services. The majority of the inmates met criteria for a current disorder despite past treatment. Further research is needed to help in developing programs to reduce women inmates' alcohol, drug, and mental health problems.  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