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   380499篇
  免费   24205篇
  国内免费   2940篇
耳鼻咽喉   5192篇
儿科学   8212篇
妇产科学   10082篇
基础医学   53234篇
口腔科学   11791篇
临床医学   30216篇
内科学   78466篇
皮肤病学   8550篇
神经病学   27246篇
特种医学   13947篇
外国民族医学   83篇
外科学   60729篇
综合类   10320篇
现状与发展   1篇
一般理论   65篇
预防医学   17565篇
眼科学   9459篇
药学   31147篇
  1篇
中国医学   2292篇
肿瘤学   29046篇
  2021年   2645篇
  2019年   2755篇
  2018年   4548篇
  2017年   3465篇
  2016年   3560篇
  2015年   4079篇
  2014年   5746篇
  2013年   7422篇
  2012年   10084篇
  2011年   10277篇
  2010年   6237篇
  2009年   5897篇
  2008年   9520篇
  2007年   10351篇
  2006年   10265篇
  2005年   9321篇
  2004年   8865篇
  2003年   8657篇
  2002年   8325篇
  2001年   28341篇
  2000年   28858篇
  1999年   23702篇
  1998年   5187篇
  1997年   4281篇
  1996年   3845篇
  1995年   3491篇
  1994年   3119篇
  1993年   2849篇
  1992年   16058篇
  1991年   14825篇
  1990年   14162篇
  1989年   13964篇
  1988年   12587篇
  1987年   12062篇
  1986年   11103篇
  1985年   10323篇
  1984年   6911篇
  1983年   5601篇
  1982年   2718篇
  1979年   5478篇
  1978年   3347篇
  1977年   2971篇
  1975年   2641篇
  1974年   3064篇
  1973年   2865篇
  1972年   2829篇
  1971年   2773篇
  1970年   2510篇
  1969年   2543篇
  1968年   2250篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
11.
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   
12.
13.
14.
15.
16.
BackgroundWomen suffering from kidney disease are more prone to fertility problems, due to uremia. Fortunately, their fertility rate increases dramatically after renal transplantation. This study analyzes the predictors/risk factors of successful pregnancy with live birth outcome while presenting an overview of the 7-year experience of a single center.MethodsThis retrospective cohort study includes 239 women of reproductive age (18–40 years) who underwent renal transplantation in a tertiary Turkish clinic between October 1, 2011, and August 24, 2017. The subjects were invited to take part in a survey questioning their obstetric characteristics and they were assessed in 2 groups: fertile and infertile. Multivariable linear regression analysis was conducted to determine the predictors of a successful pregnancy.ResultsThirty-five 35 patients wished to become pregnant: 12 got pregnant spontaneously, while 21 failed to become pregnant (spontaneously). The mean age of the patients at the survey was 34 ± 7. Regular menstrual cycles after renal transplantation, tacrolimus-mycophenolate mofetil maintenance protocol, and age at transplantation were found to be predictors of spontaneous pregnancy. The duration of peritoneal dialysis was significantly longer in the infertile group (48 vs 12 months).ConclusionEnd-stage renal disease's negative impacts, including menstrual abnormality and fertility problems, can be overcome by successful kidney transplantation with appropriate immunosuppression. Minimizing the duration of peritoneal dialysis, particularly in patients who desire future fertility, may be accepted as a logical management strategy.  相似文献   
17.
18.
19.
20.
Abstract

This study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos.  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