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   4800篇
  免费   334篇
  国内免费   3篇
耳鼻咽喉   170篇
儿科学   78篇
妇产科学   78篇
基础医学   691篇
口腔科学   244篇
临床医学   439篇
内科学   873篇
皮肤病学   49篇
神经病学   508篇
特种医学   194篇
外科学   646篇
综合类   21篇
一般理论   3篇
预防医学   412篇
眼科学   112篇
药学   261篇
中国医学   7篇
肿瘤学   351篇
  2023年   48篇
  2021年   81篇
  2020年   82篇
  2019年   119篇
  2018年   110篇
  2017年   91篇
  2016年   83篇
  2015年   82篇
  2014年   102篇
  2013年   171篇
  2012年   237篇
  2011年   224篇
  2010年   127篇
  2009年   127篇
  2008年   226篇
  2007年   198篇
  2006年   198篇
  2005年   206篇
  2004年   183篇
  2003年   149篇
  2002年   146篇
  2001年   176篇
  2000年   148篇
  1999年   113篇
  1998年   53篇
  1997年   35篇
  1996年   50篇
  1995年   42篇
  1994年   34篇
  1993年   34篇
  1992年   87篇
  1991年   100篇
  1990年   117篇
  1989年   104篇
  1988年   68篇
  1987年   85篇
  1986年   77篇
  1985年   66篇
  1984年   65篇
  1983年   46篇
  1982年   42篇
  1981年   29篇
  1980年   32篇
  1979年   61篇
  1978年   37篇
  1975年   34篇
  1974年   37篇
  1973年   31篇
  1970年   35篇
  1969年   29篇
排序方式: 共有5137条查询结果,搜索用时 31 毫秒
991.
Background The aim of this paper is to examine the impact of depressive symptoms on long-term sickness absence in a representative sample of the Danish workforce. Methods This prospective study is based on 4,747 male and female employees, participating in the Danish Work Environment Cohort Study. Depressive symptoms were measured at baseline. Data on sickness absence were obtained from a national register on social transfer payments. Onset of long-term sickness absence was followed up for 78 weeks. Results The cumulative 78 weeks incidence for the onset of long-term sickness absence was 6.5% in men and 8.9% in women. Both men and women with severe depressive symptoms (≤52 points) were at increased risk of long-term sickness absence during follow-up (men: HR = 2.69; 95% CI: 1.18, 6.12; women: HR = 2.27; 95% CI: 1.25, 4.11), after adjustment for demographic, health related, and lifestyle factors. When we divided the depressive symptom scores into quartiles, we found no significant effects with regard to long-term sickness absence. Conclusions Severe depressive symptoms, as measured with the MHI-5, increased the risk of future long-term sickness absence in the general Danish working population. However, effects were not linear, but occurred mostly only in those employees with high levels of depressive symptoms.  相似文献   
992.
The aim of this work has been to construct and evaluate a system for recording distortion product otoacoustic emissions in rats at ultrasonic frequencies up to at least 50 kHz. The paper primarily describes the design of the acoustic probe system, as this is the most critical part. An acoustic ear simulator was developed and used for the subsequent calibration of the stimulus signals. A detachable probe system was provided in order to allow for visual inspection of the probe fitting in the ear canal prior to the final placement of the acoustic probe.

Test/retest performance was evaluated by comparing DP-grams and I/O curves in 12 anaesthetized Wistar rats in two sessions separated approximately by one week. The between subject variance of the 12 tested rats appeared to be very modest, thus making the setup suitable for testing, for instance, ototoxicity of drugs or detection of cochlear damage due to noise exposures in rodents.  相似文献   
993.
The purpose was to investigate the relationship between noise exposure and tinnitus among workers with normal hearing and hearing loss, respectively. We conducted a cross-sectional survey of 752 workers employed at 91 workplaces, that were investigated by means of full work-shift noise levels, questionnaire data, and bilateral pure-tone audiometry. Tinnitus was not associated with the present noise level, the duration of noise exposure, or the cumulative noise exposure if participants had normal hearing. As expected, such trends were demonstrated if participants had a hearing handicap. Based on these data, we will be cautious in ascribing tinnitus to noise exposure in our patients’ workplaces if they have a normal audiogram. Furthermore our data indicates no risk of noise-induced tinnitus at exposure levels where no hearing loss would be expected, e.g. as usually encountered in non-industrial workplaces.  相似文献   
994.
Background: Perfluorinated alkyl acids (PFAAs), persistent chemicals with unique water-, dirt-, and oil-repellent properties, are suspected of having endocrine-disrupting activity. The PFAA compounds perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are found globally in humans; because they readily cross the placental barrier, in utero exposure may be a cause for concern.Objectives: We investigated whether in utero exposure to PFOA and PFOS affects semen quality, testicular volume, and reproductive hormone levels.Methods: We recruited 169 male offspring (19–21 years of age) from a pregnancy cohort established in Aarhus, Denmark, in 1988–1989, corresponding to 37.6% of the eligible sons. Each man provided a semen sample and a blood sample. Semen samples were analyzed for sperm concentration, total sperm count, motility, and morphology, and blood samples were used to measure reproductive hormones. As a proxy for in utero exposure, PFOA and PFOS were measured in maternal blood samples from pregnancy week 30.Results: Multivariable linear regression analysis suggested that in utero exposure to PFOA was associated with lower adjusted sperm concentration (ptrend = 0.01) and total sperm count (ptrend = 0.001) and with higher adjusted levels of luteinizing hormone (ptrend = 0.03) and follicle-stimulating hormone (ptrend = 0.01). PFOS did not appear to be associated with any of the outcomes assessed, before or after adjustment.Conclusions: The results suggest that in utero exposure to PFOA may affect adult human male semen quality and reproductive hormone levels.  相似文献   
995.
996.
Background: Although common and often with long-lasting effects, child mental health problems (MHPs) are still under-recognized and under-treated. A better understanding of the factors associated with the identification of MHPs in primary care may improve the recognition of MHPs.

Objectives: To review studies on factors associated with the identification of child MHPs in primary care.

Methods: Six leading databases were systematically searched until 1 October 2018. Two independent researchers selected articles and extracted data on study characteristics and factors associated with MHP identification. Inclusion criteria were the investigation of factors associated with MHP identification by primary care professionals (PCPs) in children aged 0–18 years.

Results: Of the 6215 articles identified, 26 were included. Prevalence rates of PCP-identified MHPs varied between 7 and 30%. PCPs identified 26–60% of children with an increased risk of MHPs as indicated by MHP assessment tools, but associated factors were investigated in relatively few studies. MHPs were more often identified in children with a family composition other than married parents, with worse mental health symptoms, prior MHPs, among boys in elementary school, when contact with PCPs was related to parental psychosocial concerns or routine health check-ups, when PCPs were recently trained in MHPs or when PCPs felt less burdened treating MHPs.

Conclusion: MHP identification varied substantially between studies and PCPs and was related to several child, family and practice factors. Future studies should systematically investigate factors associated with MHP identification by PCPs and specifically in children with an increased risk of MHPs according to mental health assessment tools.  相似文献   
997.
998.
The experiment was designed to determine the pathway taken to the brain stem by periodontal afferents responsible for the digastric jaw-opening reflex induced by tooth-tapping. Cutting the trigeminal sensory roots of anesthetized decerebrate cats eliminated the ipsilateral periodontally-induced reflex, although the stretch reflexes of the jaw-closing muscles were undiminished. These results suggest that periodontal afferents causing the jaw-opening reflex reach the brainstem through the Vth sensory root, and confirm that muscle spindle afferents travel through the Vth motor root.  相似文献   
999.
The tissue solvent capacity of a 2% stabilized sodium hypochlorite solution (Milton) and a commercial calcium hydroxide solution (Calasept) was examined under in vitro conditions where autolyzed human pulp fragments weighing approximately 0.0065 g were immersed in these solutions at 37 degrees C for periods of up to 10 days. It appeared that sodium hypochlorite was able to dissolve half the volume of pulp tissue within 1 h and the remaining tissue after 2-2 1/2 h. Calcium hydroxide dissolved half the pulp volume within 2 h, whereas it took 1 week for the remaining tissue to dissolve. These findings support the use of sodium hypochlorite as an irrigation solution during canal preparation and calcium hydroxide as a canal dressing for the purpose of creating a canal free of pulp remnants before root filling.  相似文献   
1000.
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