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   1414446篇
  免费   107858篇
  国内免费   4516篇
耳鼻咽喉   17872篇
儿科学   45630篇
妇产科学   38232篇
基础医学   207907篇
口腔科学   37751篇
临床医学   137425篇
内科学   275688篇
皮肤病学   27251篇
神经病学   118962篇
特种医学   51029篇
外国民族医学   369篇
外科学   197125篇
综合类   30018篇
现状与发展   2篇
一般理论   533篇
预防医学   120924篇
眼科学   31229篇
药学   103928篇
  6篇
中国医学   3274篇
肿瘤学   81665篇
  2021年   12203篇
  2019年   12877篇
  2018年   17877篇
  2017年   13414篇
  2016年   14474篇
  2015年   16657篇
  2014年   22971篇
  2013年   35567篇
  2012年   49176篇
  2011年   51972篇
  2010年   29969篇
  2009年   27627篇
  2008年   47622篇
  2007年   50497篇
  2006年   50418篇
  2005年   48977篇
  2004年   46827篇
  2003年   44468篇
  2002年   43258篇
  2001年   61504篇
  2000年   62963篇
  1999年   52910篇
  1998年   15625篇
  1997年   14219篇
  1996年   13874篇
  1995年   13238篇
  1994年   12320篇
  1993年   11527篇
  1992年   42038篇
  1991年   41189篇
  1990年   39816篇
  1989年   37726篇
  1988年   34941篇
  1987年   34069篇
  1986年   32534篇
  1985年   31052篇
  1984年   23623篇
  1983年   20236篇
  1982年   12562篇
  1981年   11062篇
  1979年   21192篇
  1978年   15271篇
  1977年   12565篇
  1976年   12306篇
  1975年   12496篇
  1974年   15098篇
  1973年   14754篇
  1972年   13579篇
  1971年   12565篇
  1970年   11651篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
991.
Folate receptor alpha (FRalpha) expression in epithelial ovarian cancer may be related to folate intake. We examined this association using multivitamin intake, a proxy for folic acid, and assessed whether the relation was modified by alcohol intake, a folate agonist. Cases (n = 148) with suspected epithelial ovarian cancer, of ages > or = 20 years, were seen at Mayo Clinic, Minnesota, between 2000 and 2004; those with tumor specimens (n = 108) were included in analyses. Outpatient controls (n = 148) without cancer and with at least one ovary intact were matched to cases by age (within 5 years) and state of residence. Multivitamin (> or = 4 pills/wk) and weekly alcohol (> or = 5 drinks) intakes were assessed. Tumor specimens were analyzed immunohistochemically for FRalpha. Multivariable rate ratios (RR) and 95% confidence intervals (CI) were estimated using unconditional logistic regression. In case-control analysis, the RRs of multivitamin intake with absent/weak/moderate and strong-expressing FRalpha tumors were 0.30 (95% CI, 0.12-0.70) and 0.47 (95% CI, 0.24-0.91), respectively. For alcohol, the associations were 0.84 (95% CI, 0.24-2.86) and 1.65 (95% CI, 0.69-3.93), respectively. In case-case analysis, the RR associated with developing strong-expressing versus other FRalpha tumors was 3.13 (95% CI, 1.14-8.65) for multivitamins and 1.58 (95% CI, 0.45-5.60) for alcohol. The data did not support evidence for an interaction between multivitamin and alcohol intake with risk of developing a strong-expressing FRalpha tumor. The association of multivitamin intake with ovarian cancer may depend on FRalpha expression level.  相似文献   
992.
993.
994.
995.
OBJECTIVES: The aim of the study was to check and present data on the relation between combined oral contraceptives (COC) use and body weight in young women living in Poland. METHODS: Observational study on the group of young women on COC and the control group of young women who never used COC. Candidates for study (145 women) and control (218 women) groups were recruited in selected gynecological clinics in Poland during the period of 1-31 January 2002 (with the use of randomization). RESULTS: Both groups (study and control) were almost identical in age, anthropometric characteristics, number of pregnancies and deliveries. On the basis of this investigation it was found that there was no relation between use of COC and weight gain. Observed (in both groups) weight gain in young women was most probably related rather to time-passing (patients were getting older). The higher risk for overweight and obesity was found in the group of young women who had already had problems with overweight in their childhood. and in the group of women with high weight gain during the first pregnancy. CONCLUSION: COC use is not associated with weight gain in young women with a Central European life-style.  相似文献   
996.
PURPOSE: To provide a model for assessing occupational therapy workforce needs by using a demand-based approach to determine current workforce status in the Northwest region. Regional information may have implications for addressing national occupational therapy service needs. METHOD: A questionnaire was sent to a proportional random sample of 234 facilities that hire occupational therapy practitioners. Data were collected in July-August 2003 using structured mailing and follow-up procedures. RESULTS: Response rate was 79%. Twenty-four percent reported occupational therapy vacancies and 11% occupational therapy assistant vacancies; 48% predicted an increase in occupational therapy positions in the next 2 years and 41% an increase in occupational therapy assistant positions. Sixty-three percent of respondents reported difficulty in hiring. DISCUSSION: This study identifies an occupational therapy workforce shortage in the Northwest. Management of a shortage is critical, for even short-term adjustments could lead to permanent changes in service provision. This study demonstrates the importance of current information on the status of the national workforce and serves as a model for future studies.  相似文献   
997.
998.
999.
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