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   5388篇
  免费   362篇
  国内免费   10篇
耳鼻咽喉   68篇
儿科学   175篇
妇产科学   169篇
基础医学   715篇
口腔科学   57篇
临床医学   458篇
内科学   1161篇
皮肤病学   134篇
神经病学   502篇
特种医学   255篇
外科学   739篇
综合类   102篇
一般理论   5篇
预防医学   432篇
眼科学   161篇
药学   375篇
中国医学   9篇
肿瘤学   243篇
  2023年   65篇
  2022年   114篇
  2021年   239篇
  2020年   128篇
  2019年   196篇
  2018年   260篇
  2017年   149篇
  2016年   172篇
  2015年   189篇
  2014年   250篇
  2013年   259篇
  2012年   419篇
  2011年   445篇
  2010年   220篇
  2009年   195篇
  2008年   299篇
  2007年   287篇
  2006年   257篇
  2005年   211篇
  2004年   199篇
  2003年   164篇
  2002年   130篇
  2001年   111篇
  2000年   87篇
  1999年   61篇
  1998年   36篇
  1997年   17篇
  1996年   17篇
  1995年   12篇
  1993年   13篇
  1992年   44篇
  1991年   36篇
  1990年   40篇
  1989年   33篇
  1988年   29篇
  1987年   33篇
  1986年   35篇
  1985年   25篇
  1984年   29篇
  1983年   20篇
  1982年   19篇
  1979年   14篇
  1978年   17篇
  1977年   15篇
  1975年   13篇
  1974年   13篇
  1973年   14篇
  1970年   12篇
  1968年   13篇
  1967年   13篇
排序方式: 共有5760条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.

Objective

To evaluate whether Medicare's Hospital Readmissions Reduction Program (HRRP) is associated with increased observation stay use.

Data Sources and Study Setting

A nationally representative sample of fee-for-service Medicare claims, January 2009–September 2016.

Study Design

Using a difference-in-difference (DID) design, we modeled changes in observation stays as a proportion of total hospitalizations, separately comparing the initial (acute myocardial infarction, pneumonia, heart failure) and subsequent (chronic obstructive pulmonary disease) target conditions with a control group of nontarget conditions. Each model used 3 time periods: baseline (15 months before program announcement), an intervening period between announcement and implementation, and a 2-year post-implementation period, with specific dates defined by HRRP policies.

Data Collection/Extraction Methods

We derived a 20% random sample of all hospitalizations for beneficiaries continuously enrolled for 12 months before hospitalization (N = 7,162,189).

Principal Findings

Observation stays increased similarly for the initial HRRP target and nontarget conditions in the intervening period (0.01% points per month [95% CI −0.01, 0.3]). Post-implementation, observation stays increased significantly more for target versus nontarget conditions, but the difference is quite small (0.02% points per month [95% CI 0.002, 0.04]). Results for the COPD analysis were statistically insignificant in both policy periods.

Conclusions

The increase in observation stays is likely due to other factors, including audit activity and clinical advances.  相似文献   
85.
86.
Objective: To investigate the neuroprotective effects of Syzygium aromaticum(S.aromaticum)extract(500 mg/kg) on AlCl_3(300 mg/kg)-induced mouse model of oxidative stress and neurotoxicity.Methods: An ethanolic extract of S.aromaticum seeds was prepared and the active compounds were identified using nuclear magnetic resonance spectroscopy.BALB/c mice were divided into five groups(negative control, AlCl_3-treated, self-recovery, AlCl_3 + S.aromaticum, S.aromaticum only; n=10) and treated with AlCl_3 and S.aromaticum extract.Expression of oxidative markers [Superoxide dismutase 1(SOD1) and peroxiredoxin 6(Prdx6)] and amyloid precursor protein(APP) in the hippocampus and cortex was evaluated via PCR.Histopathological assessment was performed to investigate the extent of neurodegeneration.Results: It was observed that AlCl_3 exposure increased the expression of APP770 while simultaneously down regulated the expression of APP695.AlCl_3 also induced a significant decrease(P0.05) and an increase(P0.05) in the expression level of SOD1 and Prdx6, respectively.A substantial decrease substantial(P0.05) in the density of Nissl substance was also observed in cortex of the mice treated with AlCl_3.Interestingly, treatment with S.aromaticum extract normalized the alterations in the expression level of SOD1, Prdx6 and APPisoforms and improved the neuronal structural damage.Conclusions: The results showed that S.aromaticum is a promising antioxidant and a neuroprotective agent.  相似文献   
87.
88.
Entertainment-education is an effective health communication strategy that combines or embeds educational messages into entertainment programs to bring about social and behavior change. For years, scholars have considered how entertainment-education works. Some contemporary theories posit that entertainment-education does not engender behavior change directly but does so through mediating variables. This study adds to the literature on this topic by exploring the direct relationship between exposure and social norms instead of their relationship through behavior as a mediator. Novel to this study is the use of encoded exposure, a continuous and recognition-based measure of exposure that includes ever watching, recall, involvement, and dose in its operationalization. Using cross-sectional data from Kyunki … Jeena Issi Ka Naam Hai, an entertainment-education program in India, this exploratory analysis indicates a positive and significant relationship between encoded exposure and social norms. How can this finding be applied to future programs? Questions remain, and replication is needed, but if it is not essential to go through behavior in order to change social norms, then implications emerge for the theory and practice of entertainment-education.  相似文献   
89.
90.
Early life stress has been linked to the etiology of mental health disorders. Rodent models of neonatal maternal separation stress frequently have been used to explore the long‐term effects of early stress on changes in affective and cognitive behaviors. However, most current paradigms risk metabolic deprivation, due to prolonged periods of pup removal from the dam. We have developed a new paradigm in Balb/CByJ mice, that combines very brief periods of maternal separation with temperature stress to avoid the confound of nutritional deficiencies. We have also included a within‐litter control group of pups that are not removed from the dam. The present experiments provide an initial behavioral characterization of this new model. We show that neonatally stressed mice display increased anxiety and aggression along with increased locomotion but decreased exploratory behavior. In contrast, littermate controls show increased exploration of novelty, compared to age‐matched, colony‐reared controls. Behavioral changes in our briefly stressed mice substantially concur with the existing literature, except that we were unable to observe any cognitive deficits in our paradigm. However, we show that within litter control pups also sustain behavioral changes suggesting complex and long‐lasting interactions between different environmental factors in early postnatal life. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 283–293, 2013  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