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   381699篇
  免费   25040篇
  国内免费   2847篇
耳鼻咽喉   5213篇
儿科学   8328篇
妇产科学   10117篇
基础医学   53473篇
口腔科学   11833篇
临床医学   30286篇
内科学   79511篇
皮肤病学   8578篇
神经病学   27410篇
特种医学   13998篇
外国民族医学   82篇
外科学   61041篇
综合类   9971篇
现状与发展   1篇
一般理论   64篇
预防医学   17504篇
眼科学   9455篇
药学   31234篇
  1篇
中国医学   2224篇
肿瘤学   29262篇
  2021年   2673篇
  2019年   2794篇
  2018年   4585篇
  2017年   3480篇
  2016年   3603篇
  2015年   4108篇
  2014年   5819篇
  2013年   7499篇
  2012年   10214篇
  2011年   10420篇
  2010年   6306篇
  2009年   5943篇
  2008年   9587篇
  2007年   10453篇
  2006年   10338篇
  2005年   9442篇
  2004年   8943篇
  2003年   8677篇
  2002年   8326篇
  2001年   28359篇
  2000年   28885篇
  1999年   23769篇
  1998年   5204篇
  1997年   4285篇
  1996年   3857篇
  1995年   3510篇
  1994年   3128篇
  1993年   2873篇
  1992年   16101篇
  1991年   14872篇
  1990年   14212篇
  1989年   14034篇
  1988年   12640篇
  1987年   12110篇
  1986年   11154篇
  1985年   10379篇
  1984年   6944篇
  1983年   5626篇
  1982年   2729篇
  1979年   5503篇
  1978年   3359篇
  1977年   2977篇
  1975年   2658篇
  1974年   3077篇
  1973年   2881篇
  1972年   2841篇
  1971年   2782篇
  1970年   2530篇
  1969年   2559篇
  1968年   2264篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
31.
32.
ObjectiveIdentify factors associated with healthcare providers' frequency of depot medroxyprogesterone acetate (DMPA) provision to adolescents.Study designWe analyzed data from surveys mailed to a nationally representative sample of public-sector providers and office-based physicians (n=1984). We estimated adjusted odds ratios (aORs) and 95% confidence intervals (CIs) of factors associated with frequent DMPA provision to adolescents in the past year.ResultsAlthough most providers (>95%) considered DMPA safe for adolescents, fewer reported frequent provision (89% of public-sector providers; 64% of office-based physicians). Among public-sector providers, factors associated with lower odds of frequent provision included working in settings without Title X funding (aOR 0.44, 95% CI 0.30–0.64), reporting primary care as their primary clinical focus versus reproductive or adolescent health (aOR 0.42, 95% CI 0.28–0.61), and providing fewer patients with family planning services. Among office-based physicians, factors associated with lower odds of frequent provision included specializing in obstetrics/gynecology (aOR 0.50, 95% CI 0.27–0.91) and family medicine (aOR 0.21, 95% CI 0.09–0.47) versus adolescent medicine, completing training ≥15 versus <5 years ago (aOR 0.27, 95% CI 0.09–0.83), and reporting that 0–24% of patients pay with Medicaid or other government healthcare assistance versus ≥50% (aOR 0.23, 95% CI 0.09–0.61). The reason most commonly reported by providers for infrequent DMPA provision was patient preference for another method.ConclusionsWhile most providers reported frequently providing DMPA to adolescents, training on evidence-based recommendations for contraception, focused on subgroups of providers with lower odds of frequent DMPA provision, may increase adolescents' access to contraception.ImplicationsAlthough >95% of providers considered depot medroxyprogesterone (DMPA) a safe contraceptive for adolescents, only 89% of public-sector providers and 64% of office-based physicians reported frequently providing DMPA to adolescents. Provider training on evidence-based recommendations for contraception counseling and provision may increase adolescents' access to DMPA and all methods of contraception.  相似文献   
33.
Prevention Science - This study aimed to evaluate the effectiveness of the drug and violence resistance educational program (PROERD) on short-term secondary outcomes, such as intentions to use...  相似文献   
34.
35.
36.
37.
38.
39.
Harinakshi Sanikini  David C. Muller  Marisa Sophiea  Sabina Rinaldi  Antonio Agudo  Eric J. Duell  Elisabete Weiderpass  Kim Overvad  Anne Tjønneland  Jytte Halkjær  Marie-Christine Boutron-Ruault  Franck Carbonnel  Iris Cervenka  Heiner Boeing  Rudolf Kaaks  Tilman Kühn  Antonia Trichopoulou  Georgia Martimianaki  Anna Karakatsani  Valeria Pala  Domenico Palli  Amalia Mattiello  Rosario Tumino  Carlotta Sacerdote  Guri Skeie  Charlotta Rylander  María-Dolores Chirlaque López  Maria-Jose Sánchez  Eva Ardanaz  Sara Regnér  Tanja Stocks  Bas Bueno-de-Mesquita  Roel C.H. Vermeulen  Dagfinn Aune  Tammy Y.N. Tong  Nathalie Kliemann  Neil Murphy  Marc Chadeau-Hyam  Marc J. Gunter  Amanda J. Cross 《International journal of cancer. Journal international du cancer》2020,146(4):929-942
Obesity has been associated with upper gastrointestinal cancers; however, there are limited prospective data on associations by subtype/subsite. Obesity can impact hormonal factors, which have been hypothesized to play a role in these cancers. We investigated anthropometric and reproductive factors in relation to esophageal and gastric cancer by subtype and subsite for 476,160 participants from the European Prospective Investigation into Cancer and Nutrition cohort. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox models. During a mean follow-up of 14 years, 220 esophageal adenocarcinomas (EA), 195 esophageal squamous cell carcinomas, 243 gastric cardia (GC) and 373 gastric noncardia (GNC) cancers were diagnosed. Body mass index (BMI) was associated with EA in men (BMI ≥30 vs. 18.5–25 kg/m2: HR = 1.94, 95% CI: 1.25–3.03) and women (HR = 2.66, 95% CI: 1.15–6.19); however, adjustment for waist-to-hip ratio (WHR) attenuated these associations. After mutual adjustment for BMI and HC, respectively, WHR and waist circumference (WC) were associated with EA in men (HR = 3.47, 95% CI: 1.99–6.06 for WHR >0.96 vs. <0.91; HR = 2.67, 95% CI: 1.52–4.72 for WC >98 vs. <90 cm) and women (HR = 4.40, 95% CI: 1.35–14.33 for WHR >0.82 vs. <0.76; HR = 5.67, 95% CI: 1.76–18.26 for WC >84 vs. <74 cm). WHR was also positively associated with GC in women, and WC was positively associated with GC in men. Inverse associations were observed between parity and EA (HR = 0.38, 95% CI: 0.14–0.99; >2 vs. 0) and age at first pregnancy and GNC (HR = 0.54, 95% CI: 0.32–0.91; >26 vs. <22 years); whereas bilateral ovariectomy was positively associated with GNC (HR = 1.87, 95% CI: 1.04–3.36). These findings support a role for hormonal pathways in upper gastrointestinal cancers.  相似文献   
40.
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