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   371篇
  免费   21篇
  国内免费   27篇
耳鼻咽喉   1篇
儿科学   6篇
基础医学   21篇
口腔科学   2篇
临床医学   25篇
内科学   25篇
皮肤病学   1篇
神经病学   6篇
特种医学   21篇
外科学   14篇
综合类   12篇
预防医学   98篇
药学   23篇
肿瘤学   164篇
  2021年   1篇
  2020年   2篇
  2018年   6篇
  2017年   2篇
  2016年   3篇
  2015年   6篇
  2014年   7篇
  2013年   16篇
  2012年   24篇
  2011年   24篇
  2010年   8篇
  2009年   14篇
  2008年   17篇
  2007年   35篇
  2006年   25篇
  2005年   21篇
  2004年   9篇
  2003年   14篇
  2002年   12篇
  2001年   14篇
  2000年   10篇
  1999年   14篇
  1998年   5篇
  1997年   5篇
  1996年   11篇
  1995年   12篇
  1994年   2篇
  1993年   7篇
  1992年   10篇
  1991年   10篇
  1990年   11篇
  1989年   8篇
  1988年   7篇
  1987年   7篇
  1986年   6篇
  1985年   5篇
  1984年   5篇
  1983年   4篇
  1982年   4篇
  1981年   6篇
  1980年   5篇
  1979年   1篇
  1977年   1篇
  1975年   2篇
  1974年   1篇
排序方式: 共有419条查询结果,搜索用时 15 毫秒
121.
Collecting detailed data on dietary supplement use is time-consuming for study participants and investigators, and this is particularly difficult for multivitamin use because of the many different formulations available. Therefore, many studies simply ask about the frequency of multivitamin use and assign default nutrient composition values to obtain nutrient intakes. Multivitamin supplements are important contributors to total nutrient intakes, but it is not known how default values affect the accuracy of intake estimation. In this study, nutrient intakes were calculated from multivitamins consumed by 26,735 multivitamin users who provided detailed information like product name(s) and frequency of use on a mailed questionnaire. We then recalculated the intakes, using 2 different assumptions about the composition of the multivitamin supplements: 1) a single default composition for all products; and 2) four default compositions, 1 for each subtype of multivitamin, i.e., one-a-day with minerals, one-a-day without minerals, B-complex or stress multivitamins, and antioxidant combinations. A total of 1246 different brands of multivitamins were reported and nutrient composition varied widely. Spearman correlation coefficient analyses, using the 4 default nutrient profiles compared with actual nutrient intakes, were >0.5 (P < 0.001) for 12 of 15 nutrients examined. However, correlations using the single default were lower, with only 5 correlations >0.5. Our findings suggest that a questionnaire designed to assess the composition profiles for 4 types of multivitamin products substantially improves the accuracy of nutrient-intake estimates over one that uses a single default nutrient profile for all multivitamin products.  相似文献   
122.
Differences in BMI among ethnic groups may be partially explained by the consumption of energy-dense foods, which influences energy intake in controlled laboratory studies. However, the role of dietary energy density (ED, kJ/g) in free-living persons is less understood. Our objective was to determine whether ED is related to current BMI and the risk for overweight and obesity and whether these relations are consistent among ethnic groups. We calculated ED from responses to a quantitative food frequency questionnaire and validated the measures against multiple 24-h recalls. Subjects consisted of 191,023 participants in the Hawaii-Los Angeles Multiethnic Cohort who were African American, Native Hawaiian, Japanese American, Latino, or Caucasian. Mean ED varied from a low of 4.62 kJ/g in Japanese American men to a high of 5.08 kJ/g in African American men. Mean BMI was lowest in Japanese Americans of both sexes and highest in Native Hawaiian men and African American women. After adjusting for the amount of food consumed per day, age, current smoking status, physical activity, chronic disease, and education, a 1 kJ/g increase in ED was associated with an increase in BMI of approximately 1 kg/m2 in each ethnic sex group. This same increase in ED was associated with a significantly increased risk of being overweight in all ethnic sex groups, varying from 4% in African American men to 34% in Japanese American women. Our findings suggest that consumption of an energy dense diet is a risk factor for higher BMI in both men and women across ethnic groups.  相似文献   
123.
OBJECTIVES: To assess the pathology of gastric carcinoma and to determine whether carcinoma of the cardia occurs more often among whites than among other ethnic groups in Hawaii. This study focuses on demographic differences in subsite locations and histologic types of gastric carcinoma. METHODS: We reviewed 532 sequential gastric carcinomas accessioned between 1993 and 1999 in the Hawaii Tumor Registry. Pathology reports and slides were reviewed by the study pathologist. RESULTS: Carcinoma of the cardia occurred in 51 (15.8%) of 323 males compared with 18 (8.6%) of 209 females (P = 0.02, after age adjustment). The age-adjusted percent of cardia cases was 41.8% for Hawaiian white males compared with 13.4% for men of all other ethnic groups (P = 0.0002). The age-adjusted percent of cardia cases was 22.4% for Hawaiian white females compared with 7.3% for females of other groups. (P = 0.08). At all age levels, females had more frequent diffuse carcinomas and less frequent intestinal type gastric carcinomas than men. The age-adjusted percent with diffuse carcinoma was 35.3% for females and 13.7% for males (P < 0.0001). Also, the sex-adjusted percent with diffuse carcinoma was 26.0% for patients younger than 75 years of age compared with 17.0% for patients 75 years or older (P = 0.01). Conversely, the sex-adjusted percent with intestinal carcinoma was 67.9% for patients younger than 75 years of age compared with 77.1% for patients 75 years or older (P = 0.02). The proportion of cases showing precursor lesions (intestinal metaplasia or superficial gastritis) increased progressively with the distance of the carcinoma from the cardia. CONCLUSIONS: Carcinoma of the cardia is predominantly a tumor of white males and is not associated with the multifocal gastritis characteristically found with carcinoma distal to the cardia. Diffuse gastric carcinoma shows no ethnic predilection, but expression of this phenotype is clearly related to the age and gender of the patient.  相似文献   
124.
Fat, meat, and prostate cancer   总被引:8,自引:0,他引:8  
  相似文献   
125.
126.
Steroid hormones, such as estrogens, appear to be associated with ovarian carcinogenesis, but the precise biological mechanisms are unclear. Polymorphisms in genes that regulate the concentration of estrogens and their metabolites may contribute directly to the individual variation in ovarian cancer risk through a mechanism involving oxidative stress or indirectly by influencing ovarian cancer susceptibility associated with ovulation and reproduction. We conducted a population-based, case-control study of primary ovarian cancer between 1993 and 1999 in Hawaii to test several genetic and related hypotheses. A personal interview and blood specimen were obtained in the subjects' homes. In a sample of 129 epithelial ovarian cancer cases and 144 controls, we compared the frequencies of several polymorphisms in genes that regulate steroid hormone metabolism and catecholestrogen formation. Multivariate unconditional logistic regression was used to model the association of each genetic polymorphism separately after adjusting for age, ethnicity, and other covariates. The high-activity Val432 allele of the CYP1B1 gene, which may be linked to oxidative stress through elevated 4-hydroxylated catecholestrogen formation, was associated with an increased risk of ovarian cancer. The Val/Leu genotype for CYP1B1 was associated with an odds ratio of 1.8 (95% confidence interval, 1.0-3.3) and the Val/Val genotype with an odds ratio of 3.8 (95% confidence interval, 1.2-11.4) compared with the Leu/Leu genotype (P = 0.005). Tobacco smokers with at least one CYP1A1 (MspI) m2 allele, one CYP1B1 Val allele, one COMT Met allele, or two CYP1A2 A alleles were at significantly increased risk of ovarian cancer compared to never-smokers with CYP1A1 (MspI) ml/ml, CYP1B1 Leu/Leu, COMT Val/Val, or CYP1A2 A/A genotypes, respectively. We found a positive statistical interaction (P = 0.03) between tobacco smoking and the CYP1A1 (MspI) polymorphism on the risk of ovarian cancer. None of the other gene-environment (pregnancy, oral contraceptive pill use) or gene-gene interactions were statistically significant. Although not significant, there was a suggestion that the effect of the CYP1B1 Val allele was reduced substantially in the presence of the high-activity COMT Met allele. These findings suggest that the CYP1B1-Val allele and perhaps other genetic polymorphisms in combination with environmental or hormonal exposures are susceptibility factors for ovarian cancer.  相似文献   
127.

Background and Aims

Various downstaging therapies were introduced to liver recipients who could not meet the relative criteria for liver transplantation, and many endpoints were reported. The most common criteria used were the Milan criteria and the University of California, San Francisco (UCSF) criteria. However, no comparison was made between them, and we attempted to find possible differences between the living donor liver transplantation (LDLT) patients who met the Milan criteria and those who met the UCSF criteria after accepting preoperative downstaging therapies.

Materials and Methods

We performed a retrospective study of all 72 patients at our center from January 2003 to March 2009 who were diagnosed with advanced hepatocellular carcinoma but accepted various downstaging therapies. Some patients met the Milan criteria (group 1), and some met the UCSF criteria (group 2) but not the Milan criteria. We collected the data from the two groups and then compared the preoperative demographic data, downstaging therapies, intraoperative data from LDLT, and the recovery and complications after LDLT. Survival rates were compared using Kaplan?CMeier analysis.

Results

Only 44 patients (61.1?%) met the criteria for liver transplantation, 21 cases met the Milan criteria (group 1), and 23 cases met the UCSF criteria (group 2) but not the Milan criteria. All of the 44 patients accepted right lobe living liver donor liver transplantation in our center. The difference in the baseline characteristics between the two groups did not reach statistical significance. The mean number of downstaging treatments per patient was 1.81?±?0.35 in group 1 and 1.83?±?0.41 in group 2 (P?=?0.928). Most of the patients received only one downstaging treatment, and transcatheter arterial chemoembolization (TACE) was the most common downstaging therapy. Four patients suffered complications after downstaging therapies: intra-abdominal hemorrhage after right hepatectomy, upper gastrointestinal hemorrhage after TACE, biliary fistula after resection, and hand?Cfoot syndrome after taking sorafenib. All complications after LDLT, classified according to the Clavien?CDindo system, were compared within the two groups, and the calculated score of the complications in group 1 was 1.48?±?1.63, which was greater than that of group 2 (1.39?±?1.64), but this difference did not reach statistical significance (P?=?0.865). The 1-, 3-, and 5-year survival rates were 90.4, 76.2, and 71.4?% in group 1 and 91.3, 73.9, and 69.6?% in group 2, respectively (P?>?0.05). Seven patients (three in group 1 and four in group 2) had tumor recurrence after a median follow-up period of 72?months. The pathology findings were not different between the two groups.

Conclusion

Recipients who meet the Milan or UCSF criteria after accepting successful preoperative downstaging therapy in LDLT can achieve the same result.  相似文献   
128.
Common genetic risk variants for type 2 diabetes (T2D) have primarily been identified in populations of European and Asian ancestry. We tested whether the direction of association with 20 T2D risk variants generalizes across six major racial/ethnic groups in the U.S. as part of the Population Architecture using Genomics and Epidemiology Consortium (16,235 diabetes case and 46,122 control subjects of European American, African American, Hispanic, East Asian, American Indian, and Native Hawaiian ancestry). The percentage of positive (odds ratio [OR] >1 for putative risk allele) associations ranged from 69% in American Indians to 100% in European Americans. Of the nine variants where we observed significant heterogeneity of effect by racial/ethnic group (P(heterogeneity) < 0.05), eight were positively associated with risk (OR >1) in at least five groups. The marked directional consistency of association observed for most genetic variants across populations implies a shared functional common variant in each region. Fine-mapping of all loci will be required to reveal markers of risk that are important within and across populations.  相似文献   
129.
130.
An epidemiologic study of thyroid cancer in Hawaii   总被引:5,自引:0,他引:5  
A population-based case-control interview study was designed to test the hypothesis that dietary iodine or the consumption of goitrogenic vegetables increases the risk of thyroid cancer. A total of 191 histologically confirmed cases (64 percent female) and 441 matched controls from five ethnic groups in Hawaii were available for analysis. Among women, intake of seafood (especially shellfish), harm ha (a fermented fish sauce), and dietary iodine were associated with an increased risk of cancer, whereas consumption of goitrogenic (primarily cruciferous) vegetables was associated with a decreased risk. Non-dietary risk factors included miscarriage (especially at first pregnancy), use of fertility drugs, family history of thyroid disease, obesity, and work as a farm laborer. The odds ratio for the combined effect of a high iodine intake and a first-pregnancy miscarriage was 4.8 (95 percent confidence interval [CI]=1.2 – 19.2); and for high iodine intake and use of fertility drugs 7.3 (95 percent CI=1.5 – 34.5). Among men, positive associations were found for obesity, work as a farm laborer, and a past history of benign thyroid disease. Although this study identified several dietary and non-dietary risk factors for thyroid cancer, it could not fully explain the exceptionally high incidence rates among Filipino women in Hawaii.Drs Kolonel, Hankin, and Wilkens are in the Epidemiology Program, Cancer Research Center, University of Hawaii. Dr Fukunaga is at the Kuakini Medical Center, Honolulu, HI, USA. Dr Hinds was with the Epidemiology Program at the time of this work and is now with the Snobomish Health District, Everett, WA, USA. Address correspondence to Dr Kolonel at 1236 Lauhala Street, Room 407, Honolulu, HI 96813, USA. This work was supported in part by grant no. 1 PO1 33619 and contract no. N01 CN 55424 from the National Cancer Institute, US Department of Health and Human Services.  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