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   1337306篇
  免费   102372篇
  国内免费   4258篇
耳鼻咽喉   16826篇
儿科学   43744篇
妇产科学   36506篇
基础医学   198418篇
口腔科学   35956篇
临床医学   129974篇
内科学   258891篇
皮肤病学   26472篇
神经病学   112084篇
特种医学   48342篇
外国民族医学   367篇
外科学   184516篇
综合类   28824篇
现状与发展   2篇
一般理论   460篇
预防医学   114684篇
眼科学   29062篇
药学   99189篇
  6篇
中国医学   3206篇
肿瘤学   76407篇
  2021年   11133篇
  2019年   11778篇
  2018年   16440篇
  2017年   12377篇
  2016年   13376篇
  2015年   15312篇
  2014年   20937篇
  2013年   32226篇
  2012年   44512篇
  2011年   47156篇
  2010年   27231篇
  2009年   25069篇
  2008年   42971篇
  2007年   45309篇
  2006年   45417篇
  2005年   43848篇
  2004年   41767篇
  2003年   39689篇
  2002年   38445篇
  2001年   60948篇
  2000年   62593篇
  1999年   52369篇
  1998年   14620篇
  1997年   13316篇
  1996年   13156篇
  1995年   12492篇
  1994年   11659篇
  1993年   10943篇
  1992年   41631篇
  1991年   40815篇
  1990年   39500篇
  1989年   37385篇
  1988年   34637篇
  1987年   33749篇
  1986年   32189篇
  1985年   30693篇
  1984年   23066篇
  1983年   19611篇
  1982年   11765篇
  1979年   20835篇
  1978年   14834篇
  1977年   12078篇
  1976年   11889篇
  1975年   12121篇
  1974年   14812篇
  1973年   14488篇
  1972年   13368篇
  1971年   12422篇
  1970年   11488篇
  1969年   10422篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
951.
952.
953.
954.
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   
955.
956.
957.
958.
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   
959.
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   
960.
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