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   12385篇
  免费   1187篇
  国内免费   57篇
耳鼻咽喉   100篇
儿科学   536篇
妇产科学   348篇
基础医学   1751篇
口腔科学   415篇
临床医学   1363篇
内科学   2531篇
皮肤病学   187篇
神经病学   1003篇
特种医学   533篇
外科学   1526篇
综合类   313篇
一般理论   19篇
预防医学   1332篇
眼科学   103篇
药学   943篇
  1篇
中国医学   25篇
肿瘤学   600篇
  2021年   201篇
  2020年   85篇
  2019年   172篇
  2018年   253篇
  2017年   152篇
  2016年   201篇
  2015年   222篇
  2014年   280篇
  2013年   405篇
  2012年   629篇
  2011年   586篇
  2010年   348篇
  2009年   353篇
  2008年   552篇
  2007年   595篇
  2006年   531篇
  2005年   500篇
  2004年   463篇
  2003年   425篇
  2002年   424篇
  2001年   400篇
  2000年   407篇
  1999年   360篇
  1998年   176篇
  1997年   182篇
  1996年   148篇
  1995年   134篇
  1994年   137篇
  1993年   126篇
  1992年   289篇
  1991年   283篇
  1990年   264篇
  1989年   263篇
  1988年   259篇
  1987年   254篇
  1986年   246篇
  1985年   206篇
  1984年   156篇
  1983年   164篇
  1982年   97篇
  1981年   85篇
  1980年   92篇
  1979年   167篇
  1978年   127篇
  1977年   112篇
  1976年   82篇
  1975年   94篇
  1974年   103篇
  1973年   90篇
  1972年   77篇
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
961.
目的 探讨白细胞介素 8(IL 8)和内皮素① (ET 1)在慢性阻塞性肺疾病 (COPD)发病机制中的作用。方法 随机选择稳定期COPD患者 3 0例 ,健康对照组 2 0例 ,其中吸烟组和不吸烟组各 10例 ,分别用放免法检测血浆中IL 8及ET 1水平。结果 COPD组IL 8、ET 1水平明显高于对照组 (P <0 0 5 ) ,且与FEV1 %呈负相关 ;吸烟组IL 8高于不吸烟组。结论 IL 8、ET 1参于COPD气道炎症及气流阻塞的形成。  相似文献   
962.
Stice E  Rohde P  Gau J  Shaw H 《Prevention science》2012,13(2):129-139
Test (a) whether a dissonance-based eating disorder prevention program that reduces thin-ideal internalization mitigates the effects of risk factors for eating disorder onset and (b) whether the risk factors moderate the effects of this intervention on risk for eating disorder onset, to place the effects of this intervention within the context of established risk factors. Female adolescents (N = 481) with body image concerns were randomized to the dissonance-based program, healthy weight control program, expressive writing control condition, or assessment-only control condition. Denial of costs of pursuing the thin-ideal was the most potent risk factor for eating disorder onset during the 3-year follow-up (OR = 5.0). The dissonance program mitigated the effect of this risk factor. For participants who did not deny costs of pursuing the thin-ideal, emotional eating and externalizing symptoms increased risk for eating disorder onset. Negative affect attenuated the effects of each of the active interventions in this trial. Results imply that this brief prevention program offsets the risk conveyed by the most potent risk factor for eating disorder onset in this sample, implicate three vulnerability pathways to eating pathology involving thin-ideal pursuit, emotional eating, and externalizing symptoms, and suggest that negative affect mitigates the effects of eating disorder prevention programs.  相似文献   
963.
This study sought to evaluate the relationship between dietary intake of fat, polyunsaturated fat, saturated fat, arachidonic acid, and selected dietary antioxidants and levels of oxidative damage as measured by urinary levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-epi-prostaglandin F2alpha (8-iso-PGF2alpha) in women previously treated for breast cancer. Two hundred two study subjects participating in the Women's Healthy Eating and Living (WHEL) study were included in this ancillary study. Dietary intakes and concentrations of urinary 8-OHdG and 8-iso-PGF2alpha were measured at baseline and 12 mo in the 179 women included in the analytical cohort. Study subjects demonstrated a significant reduction in dietary total, polyunsaturated, and saturated fat intake and a significant increase in vitamins E and C and beta-carotene intake from baseline to 12 mo. Linear mixed-models analysis using baseline and Year 1 data indicated that vitamin E intake was inversely associated with both 8-OHdG and 8-iso-PGF2alpha. 8-Iso-PGF2alpha is increased with increased body mass index (BMI) and polyunsaturated fatty acid (PUFA) intake, indicating an increase in lipid peroxidation with greater BMI and higher PUFA intake. 8-OHdG was inversely related to age but positively related to arachidonic acid, indicating an increase in DNA damage with higher intake of arachidonic acid (meat). The results of this nested case-controlled study provide potential mechanisms by which a high fruit and vegetable, low-fat diet might reduce the recurrence rate of or early-stage breast cancer.  相似文献   
964.
BACKGROUND: According to the 2002 National Immunization Survey (NIS), vaccination coverage with recommended vaccines among U.S. children aged 19 to 35 months remained near all-time highs. Sustaining this high coverage requires significant effort, including consideration of parental vaccine safety concerns that have led to decreasing coverage in other countries. METHODS: The Parental Knowledge and Experiences module was administered to a random subset of NIS respondents from July 2001 to December 2002. The module included questions regarding attitudes toward vaccine safety and side effects, simultaneous vaccine administration, and acceptance of new vaccines. Multivariate logistic regression analyses examined associations between attitudes and up-to-date (UTD) vaccination coverage (four or more doses of diphtheria and tetanus toxoids and pertussis vaccine, three or more doses of poliovirus vaccine, one or more doses of any measles-containing vaccine, three or more doses of Haemophilus influenzae type b vaccine, and three or more doses of hepatitis B vaccine), while controlling for demographics. RESULTS: Ninety-three percent of parents rated vaccines as safe, 6% as neither safe nor unsafe, and 1% as unsafe. After adjusting for demographics, parental safety belief was significantly associated with the child's vaccination status. For children whose parents believed vaccines are safe, the odds of being UTD were 2.9 times the odds of being UTD for children of parents who believed vaccines are unsafe (75% vs 53%, respectively). Children whose parents were neutral about the safety of vaccines had vaccination coverage similar to children whose parents believed vaccines are unsafe. CONCLUSIONS: A significant association with vaccine coverage was found for a small group of parents with high vaccine safety concerns. Strategies focused on safety concerns may yield better protection for these children.  相似文献   
965.
Re-evaluating the burden of rabies in Africa and Asia   总被引:14,自引:0,他引:14  
OBJECTIVE: To quantify the public health and economic burden of endemic canine rabies in Africa and Asia. METHODS: Data from these regions were applied to a set of linked epidemiological and economic models. The human population at risk from endemic canine rabies was predicted using data on dog density, and human rabies deaths were estimated using a series of probability steps to determine the likelihood of clinical rabies developing in a person after being bitten by a dog suspected of having rabies. Model outputs on mortality and morbidity associated with rabies were used to calculate an improved disability-adjusted life year (DALY) score for the disease. The total societal cost incurred by the disease is presented. FINDINGS: Human mortality from endemic canine rabies was estimated to be 55 000 deaths per year (90% confidence interval (CI) = 24 000-93 000). Deaths due to rabies are responsible for 1.74 million DALYs lost each year (90% CI = 0.75-2.93). An additional 0.04 million DALYs are lost through morbidity and mortality following side-effects of nerve-tissue vaccines. The estimated annual cost of rabies is USD 583.5 million (90% CI = USD 540.1-626.3 million). Patient-borne costs for post-exposure treatment form the bulk of expenditure, accounting for nearly half the total costs of rabies. CONCLUSION: Rabies remains an important yet neglected disease in Africa and Asia. Disparities in the affordability and accessibility of post-exposure treatment and risks of exposure to rabid dogs result in a skewed distribution of the disease burden across society, with the major impact falling on those living in poor rural communities, in particular children.  相似文献   
966.
To investigate the relationship between homocysteine (Hcy) and B vitamins status in the Taiwanese elderly population, an analysis was made of the plasma Hcy levels in elderly persons. The study sample was taken from the Elderly Nutrition and Health Survey in Taiwan (1999-2000) (Elderly NAHSIT) and included 1094 males and 1135 females aged 65-90 years. The results showed that average plasma Hcy was 13.3+/-0.6 micromol/ L for males and 10.6+/-0.7 micromol/L for females. The average plasma Hcy levels of males from all age groups were significantly higher than those of females, and significantly increased with age (P<0.0001). The overall prevalence of hyperhomocysteinemia (Hcy>15 micromol/L) was 23.4% for elderly males and 11.2% for elderly females, and this also increased with age (P<0.0001). In subjects with normal renal function, folate, vitamin B2, B6, and B12 status were significantly lower in males with hyperhomocysteinemia, while only folate and vitamin B12 were significantly lower in females with hyperhomocysteinemia. Further analysis suggested that folate, vitamin B6 or B12 insufficiency were associated with hyperhomocysteinemia in both sexes, while vitamin B2 insufficiency was significantly associated only in males. In elderly persons with adequate folate, vitamin B6, and B12 status, there was no significant association between vitamin B2 and hyperhomocysteinemia. This association occurred only in those who had concurrent poor folate, vitamin B6, or B12 status. The strength of the association between vitamin B12 insufficiency and hyperhomocysteinemia was not affected by simultaneous vitamin B2 or B6 insufficiency, but increased about 3-fold when combined with folate. This suggests that poor folate and vitamin B12 status has a synergistic effect on the risk of hyperhomocysteinema in the elderly, as did a poor folate and vitamin B6 status. Therefore, maintaining adequate vitamin B12 status and avoiding multiple B vitamin insufficiency, especially that of folate and vitamin B12 or B6, should be emphasized as an important measure for reducing plasma Hcy levels among elderly Taiwanese.  相似文献   
967.
Iron status, prevalence of iron deficiency and elevated iron stores, and the effect of gastrointestinal ulceration on iron status in free-living Taiwanese elderly persons were all assessed in a nationally representative, cross-sectional nutrition survey--the Elderly NAHSIT. The survey included blood measurements of iron indices. Data were collected from 1202 elderly men and 1152 elderly women aged 65 years and older. Multiple iron measures, including serum ferritin (SF), transferrin saturation (Tsat), and hemoglobin were used to evaluate the prevalence of iron deficient erythropoiesis (ID) and iron deficiency anemia (IDA). Despite no routine practice of iron fortification in Taiwan, elderly subjects had a low prevalence of ID and IDA. The prevalence of ID was 2.3% in men and 1.4% in women. The prevalence of IDA was 2.5% in men and 2.0% in women. In contrast, 15.7% of men and 9.8% of women had elevated iron stores as diagnosed by SF>300 microg/L. Subjects with a history of gastrointestinal ulceration had significantly lower serum ferritin than those without ulcers, but the prevalence of anemia, ID and IDA was unaffected. In conclusion, elderly people in Taiwan are an iron-replete population with a high prevalence of elevated iron stores and a low prevalence of iron deficiency.  相似文献   
968.
There is little documented information regarding current provision of psycho-educational interventions in the context of juvenile chronic arthritis (JCA). The purpose of the present exploratory study was to gain insight and understanding of the needs and preferences of children with JCA and their parents, and to examine how these may be more adequately addressed by future psycho-educational interventions. Data were collected through focus group discussions with children, parents and health professionals, respectively. Results showed that the voices of children and their parents were as one in calling for greater availability, easier access and more comprehensive psycho-educational interventions in the context of JCA. Greater emphasis is needed upon the social and emotional aspects of chronic disease, and enhancing the self-management skills of children and their families. Moreover, content should be tailored to match broad categories of disease severity (e.g. mild or severe), developmental age and stage in the life course (e.g. child or adolescent). Group education, informal support groups, activity weekends and summer camps would be particularly welcomed by parents and children, and may serve to reduce their sense of isolation whilst providing much needed reassurance. Findings provide a useful set of signposts to guide future development of psycho-educational interventions in the field of psychosocial paediatric rheumatology.  相似文献   
969.
This study compared the prevalence of asthma with climate and air pollutant data to determine the relationship between asthma prevalence and these factors. We conducted a nationwide survey of respiratory illness and symptoms in middle-school students in Taiwan. Lifetime prevalences of physician-diagnosed asthma and of typical symptoms of asthma were compared to air monitoring station data for temperature, relative humidity, sulfur dioxide, nitrogen oxides, ozone, carbon monoxide, and particulate matter with aerodynamic diameter [less than/equal to] 10 microm (PM(10)). A total of 331,686 nonsmoking children attended schools located within 2 km of 55 stations. Asthma prevalence rates adjusted for age, history of atopic eczema, and parental education were associated with nonsummer (June-August) temperature, winter (January-March) humidity, and traffic-related air pollution, especially carbon monoxide and nitrogen oxides, for both girls and boys. Nonsummer temperature, winter humidity, and traffic-related air pollution, especially carbon monoxide and nitrogen oxides, were positively associated with the prevalence of asthma in middle-school students in Taiwan.  相似文献   
970.
A woman with a history of spontaneous abortion in her immediately prior pregnancy may be at increased risk for a pregnancy affected by a neural tube defect (NTD). A short interpregnancy interval may further increase this risk. Using data from a population-based case-control study (1989-1991), the authors investigated NTD risk resulting from a prior spontaneous abortion or elective termination and a short interpregnancy interval. Of 538 interviewed case mothers and 539 interviewed control mothers, 408 case mothers and 433 control mothers reported having a prior pregnancy. Analysis showed a slightly decreased NTD risk among mothers whose immediately prior pregnancy had ended in a spontaneous abortion or elective termination in comparison with a live birth (odds ratio (OR) = 0.82; 95% confidence interval (CI): 0.61, 1.1). This decreased risk was consistent across strata of short or long interpregnancy intervals. Additional analysis revealed an increased NTD risk for mothers with an interpregnancy interval of < or =6 months compared with >12-< or =24 months (OR = 1.5; 95% CI: 0.93, 2.4). This latter risk was greatest among mothers whose immediately prior pregnancy had resulted in a live birth (OR = 2.0; 95% CI: 1.0, 3.8) rather than a spontaneous abortion or elective termination (OR = 0.96; 95% CI: 0.44, 2.1). Adjustment for potential covariates did not substantially alter observed risk estimates.  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