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   810篇
  免费   25篇
  国内免费   1篇
耳鼻咽喉   2篇
儿科学   24篇
妇产科学   12篇
基础医学   85篇
口腔科学   26篇
临床医学   90篇
内科学   132篇
皮肤病学   1篇
神经病学   71篇
特种医学   38篇
外科学   159篇
综合类   6篇
预防医学   69篇
眼科学   13篇
药学   65篇
中国医学   1篇
肿瘤学   42篇
  2023年   6篇
  2022年   16篇
  2021年   22篇
  2020年   20篇
  2019年   18篇
  2018年   23篇
  2017年   16篇
  2016年   14篇
  2015年   19篇
  2014年   38篇
  2013年   47篇
  2012年   82篇
  2011年   67篇
  2010年   30篇
  2009年   23篇
  2008年   46篇
  2007年   59篇
  2006年   38篇
  2005年   43篇
  2004年   32篇
  2003年   35篇
  2002年   31篇
  2001年   9篇
  2000年   10篇
  1999年   4篇
  1998年   2篇
  1997年   4篇
  1996年   2篇
  1995年   2篇
  1994年   2篇
  1993年   4篇
  1992年   6篇
  1991年   8篇
  1990年   7篇
  1989年   6篇
  1988年   7篇
  1987年   7篇
  1986年   4篇
  1985年   1篇
  1984年   5篇
  1983年   2篇
  1982年   5篇
  1980年   3篇
  1977年   2篇
  1976年   2篇
  1974年   1篇
  1973年   2篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有836条查询结果,搜索用时 12 毫秒
41.
Irregular bladder and bowel habits can contribute to urinary and bowel problems. Schoolchildren undergoing treatment for these problems often do not follow the recommendation of regular toilet visits at school, claiming negative perceptions of school toilets. This study examined 6- to 16-year-old schoolchildren's perceptions of school toilets and whether the perceptions affect bladder and bowel habits at school Some 385 Swedish schoolchildren aged 6 to 16 years were surveyed using a semistructured questionnaire. Children aged 13 to 16 years had the most negative perceptions. Twenty-five percent (overall 16%) of older children reported never using the school toilet to urinate, and 80% (overall 63%) never used it to defecate. Perceptions of sight and smell and emotional constraints hindered children from using the school toilets. Children generally based their perceptions of school toilets on physical appearance, offensive smell, and feelings of insecurity. Children's perceptions affected their toilet habits and would rather endure physical discomfort than the psychological and social discomfort of using the school toilet. Children already suffering from urinary tract or intestinal problems face particular difficulties without regular toilet visits during the day.  相似文献   
42.
We examined the relation of early life socioeconomic circumstances to cognition in older residents of a biracial urban community. Participants had brief cognitive testing three times at approximately 3-year intervals. At baseline, information about early life household and county socioeconomic level was collected. In mixed-effects models adjusted for age, sex, race, and education, both early life household and county socioeconomic levels were positively associated with baseline level of cognition but unrelated to cognitive decline. The results suggest that socioeconomic conditions in early life are associated with level of cognitive function in old age but not with rate of cognitive decline.  相似文献   
43.
BACKGROUND: Deficiencies in folate and vitamin B12 have been associated with neurodegenerative disease. OBJECTIVE: To examine the association between rates of age-related cognitive change and dietary intakes of folate and vitamin B12. DESIGN: Prospective study performed from 1993 to 2002. SETTING: Geographically defined biracial community in Chicago, Ill. PARTICIPANTS: A total of 3718 residents, 65 years and older, who completed 2 to 3 cognitive assessments and a food frequency questionnaire. MAIN OUTCOME MEASURE: Change in cognitive function measured at baseline and 3-year and 6-year follow-ups, using the average z score of 4 tests: the East Boston Tests of immediate and delayed recall, the Mini-Mental State Examination, and the Symbol Digit Modalities Test. RESULTS: High folate intake was associated with a faster rate of cognitive decline in mixed models adjusted for multiple risk factors. The rate of cognitive decline among persons in the top fifth of total folate intake (median, 742 microg/d) was more than twice that of those in the lowest fifth of intake (median, 186 microg/d), a statistically significant difference of 0.02 standardized unit per year (P = .002). A faster rate of cognitive decline was also associated with high folate intake from food (P for trend = .04) and with folate vitamin supplementation of more than 400 microg/d compared with nonusers (beta = -.03, P<.001). High total B12 intake was associated with slower cognitive decline only among the oldest participants. CONCLUSIONS: High intake of folate may be associated with cognitive decline in older persons. These unexpected findings call for further study of the cognitive implications of high levels of dietary folate in older populations.  相似文献   
44.
45.
Citalopram, a selective serotonin reuptake inhibitor, is one of the most commonly found drugs in Swedish forensic autopsy cases. Citalopram is a racemic drug with 50:50 of the S- and R- enantiomers. Enantioselective analysis of citalopram and its metabolites desmethylcitalopram and didesmethylcitalopram were performed in femoral blood from 53 autopsy cases by a chiral high-performance liquid chromatography (HPLC) method. The mean (+/- standard deviation) S/R ratio for citalopram was 0.67 +/- 0.25 and for desmethylcitalopram, 0.68 +/- 0.20. We found increasing S/R ratios with increasing concentrations of citalopram. We also found that high citalopram S/R ratios were associated with a high parent drug-to-metabolite ratio and may be an indicator of recent intake. Citalopram is metabolized by cytochrome P450 (CYP) 3A4, 2C19, and 2D6. Genotyping for the polymorphic CYP2C19 and CYP2D6 revealed no poor metabolizers regarding CYP2C19 and only 2 (3.8%) poor metabolizers regarding CYP2D6. The presence of drugs metabolized by and/or inhibiting these enzymes in several of the cases suggests that such pharmacokinetic interactions are a more important (practical) problem than metabolic deficiency. Enantioselective analysis of citalopram and its metabolites can provide additional information when interpreting forensic toxicology results and might be a necessity in the future.  相似文献   
46.
47.
BACKGROUND: To study the prevalence of pain during intercourse in a young population and analyze factors that may be associated with vulvar pain. METHODS: During a 2-month period, 172 women (aged 12-26 years) consulting four different adolescent health centres in Stockholm, Sweden, responded to a questionnaire concerning sexual habits, history of infections, and genital symptoms a priori vulvar pain. Multiple logistic regression model was used to evaluate the independent effects of the variables associated with vulvar pain. RESULTS: One-third of the women reported regular pain during and/or after intercourse. Having regular sexual intercourse before the age of 16 years and using oral contraception for more than 2 years were independent variables increasing the risk of vulvar pain. There was a correlation trend between vulvar pain and lack of sexual desire, recurrent candida infections, and urinary tract infections. However, there was no correlation to sexually transmitted diseases. More than 4 years of regular intercourse and coitus at least 4 times a week were factors that inversely correlated to vulvar pain. CONCLUSIONS: One-third of young women answering a questionnaire at adolescent health centres reported regular pain during and/or after intercourse. Early regular coitus and long-time use of oral contraceptives were factors associated with vulvar pain. Frequently rubbing a vulnerable mucosa may result in irreversible damage and vulvar vestibulitis syndrome.  相似文献   
48.
Accounts of self-perceptions of oral health have hitherto been rare, although they are of great interest for strategies in health promotion. The objective of this study was to increase our knowledge of adolescents' perceptions of oral health and influencing factors. Semi-structured interviews of 17 Swedish adolescents were performed. Criteria for strategic sampling were age (15, 18 years), gender (male, female), and dental health (healthy, unhealthy). Data were analyzed according to the constant comparative method. Areas of focus were general oral health, personal oral health, dental care, and life-style issues. Oral health awareness was generally low among the informants. Two categories of oral health were identified: action (the physical things we do to effect the condition of our mouths) and condition (the physical status of the mouth). Conditional aspects were most frequent in evaluations of personal oral health. The informants considered their possibilities to influence oral health limited. Perceptions of influences on oral health were related to personal and professional care, social support and impact, and external factors. 'Concern for oral health' was derived as the core category in perceived influence on oral health. The study indicates that it is important to find factors that enhance adolescents' awareness of their own resources and to seek mechanisms that govern internalization. There is a need to find strategies to convey such knowledge to the intermediaries: dental personnel and parents.  相似文献   
49.
Tumor cells might be susceptible to different effector functions of the immune system. This cytotoxic capacity has been utilized to analyze the prognostic significance of peripheral blood mononuclear cells (PBMC) in patients with metastatic colorectal carcinoma (CRC) treated with the monoclonal antibody (MAb)17-1A. Such analysis might form the basis for future patient selection and may lead to improvements in therapeutic strategies. Between 1986 and 1998, 73 patients were treated with regimens containing MAb17-1A. Prior to therapy, the lytic capability of PBMC was assayed against: K562 (4 hr assay), the CRC cell line SW948 (4 hr and 18 hr assays) and antibody-dependent cellular cytotoxicity (ADCC, 18 hr assay). Since the study was performed over 13 years, the assays were checked for time-related bias. Reproducibility over time was satisfactory. Patients exhibited a significantly higher cytotoxic capability in all 4 assays compared to healthy control donors. No correlation to clinical outcome was noted for 18 hr ADCC and 18 hr spontaneous cytotoxicity. Pretreatment natural killer (NK) cell cytotoxicity (K562) was significantly related to overall survival (OS), progression-free survival (PFS), and response rate. OS for patients with high and low NK cell cytotoxicity was 71 vs. 30 weeks, respectively (p = 0.007). NK cell cytotoxicity (K562) was an independent prognostic factor for OS (p = 0.016). Pretreatment NK cell activity is a strong prognostic factor for patients with metastatic CRC receiving MAb17-1A therapy and is a predictor for OS, PFS and response. These results should be considered when designing antibody-based therapeutic protocols.  相似文献   
50.
A large proportion of people with Alzheimer's disease (AD) are women; however, it is not clear whether this is due to higher risk of disease or solely to the larger number of women alive at ages when AD is common. Beginning in 1982, two stratified random samples of people aged > or =65 years in East Boston, Massachusetts underwent detailed, structured clinical evaluation for prevalent (467 people) and incident (642 people from a cohort previously ascertained to be disease-free) probable AD. The prevalence sample was followed for mortality for up to 11 years (through December 1992). The age-specific incidence of AD did not differ significantly by sex (for men vs. women, odds ratio = 0.92; 95% confidence interval (CI): 0.51, 1.67). Controlled for age, prevalence also did not differ significantly by sex (for men vs. women, odds ratio = 1.29; 95% CI: 0.67, 2.48). The increase in risk of mortality due to AD did not vary by sex. The odds ratio for women with AD compared with women without AD was 2.07 (95% CI: 1.21, 3.56). For men, the odds ratio was 2.22 (95% CI: 1.02, 4.81). These findings suggest that the excess number of women with AD is due to the longer life expectancy of women rather than sex-specific risk factors for the disease.  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