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   3545篇
  免费   203篇
  国内免费   8篇
耳鼻咽喉   27篇
儿科学   103篇
妇产科学   93篇
基础医学   405篇
口腔科学   49篇
临床医学   477篇
内科学   498篇
皮肤病学   72篇
神经病学   391篇
特种医学   89篇
外科学   409篇
综合类   24篇
一般理论   1篇
预防医学   575篇
眼科学   29篇
药学   203篇
中国医学   6篇
肿瘤学   305篇
  2024年   4篇
  2023年   36篇
  2022年   51篇
  2021年   111篇
  2020年   68篇
  2019年   91篇
  2018年   108篇
  2017年   85篇
  2016年   109篇
  2015年   89篇
  2014年   116篇
  2013年   200篇
  2012年   260篇
  2011年   312篇
  2010年   137篇
  2009年   130篇
  2008年   226篇
  2007年   266篇
  2006年   225篇
  2005年   244篇
  2004年   233篇
  2003年   226篇
  2002年   211篇
  2001年   34篇
  2000年   23篇
  1999年   14篇
  1998年   27篇
  1997年   22篇
  1996年   10篇
  1995年   7篇
  1994年   7篇
  1993年   13篇
  1992年   10篇
  1991年   8篇
  1990年   7篇
  1989年   6篇
  1988年   1篇
  1987年   3篇
  1986年   4篇
  1985年   6篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   3篇
  1979年   2篇
  1976年   1篇
  1973年   1篇
  1969年   1篇
  1966年   1篇
排序方式: 共有3756条查询结果,搜索用时 31 毫秒
61.

Background

Although prenatal methylmercury exposure has been linked to poorer intellectual function in several studies, data from two major prospective, longitudinal studies yielded contradictory results. Associations with cognitive deficits were reported in a Faroe Islands cohort, but few were found in a study in the Seychelles Islands. It has been suggested that co-exposure to another contaminant, polychlorinated biphenyls (PCBs), may be responsible for the positive findings in the former study and that co-exposure to nutrients in methylmercury-contaminated fish may have obscured and/or protected against adverse effects in the latter.

Objectives

We aimed to determine the degree to which co-exposure to PCBs may account for the adverse effects of methylmercury and the degree to which co-exposure to docosahexaenoic acid (DHA) may obscure these effects in a sample of Inuit children in Arctic Québec.

Methods

IQ was estimated in 282 school-age children from whom umbilical cord blood samples had been obtained and analyzed for mercury and other environmental exposures.

Results

Prenatal mercury exposure was related to poorer estimated IQ after adjustment for potential confounding variables. The entry of DHA into the model significantly strengthened the association with mercury, supporting the hypothesis that beneficial effects from DHA intake can obscure adverse effects of mercury exposure. Children with cord mercury ≥ 7.5 μg/L were four times as likely to have an IQ score < 80, the clinical cut-off for borderline intellectual disability. Co-exposure to PCBs did not alter the association of mercury with IQ.

Conclusions

To our knowledge, this is the first study to document an association of prenatal mercury exposure with poorer performance on a school-age assessment of IQ, a measure whose relevance for occupational success in adulthood is well established. This association was seen at levels in the range within which many U.S. children of Asian-American background are exposed.

Citation

Jacobson JL, Muckle G, Ayotte P, Dewailly É, Jacobson SW. 2015. Relation of prenatal methylmercury exposure from environmental sources to childhood IQ. Environ Health Perspect 123:827–833; http://dx.doi.org/10.1289/ehp.1408554  相似文献   
62.
In 2005 the American Association of Critical Care Nurses defined six Healthy Work Environment (HWE) standards for the clinical setting (AACN, 2005), which were reaffirmed and expanded in 2016 (AACN, 2016). These clinical standards were adapted for use in the academic setting by Fontaine, Koh, and Carroll in 2012. The intention of this article is threefold: to present a revised version of the academic workplace standards which are appropriate for all School of Nursing (SON) employees, staff as well as faculty; to proposes the addition of a seventh standard, self-care, which provides the foundation for all standards; and to describe the continuing implementation of these seven standards at the University of Virginia School of Nursing (UVA SON).  相似文献   
63.
We describe a unique program, the Kansas Legislative Health Academy, that brings together state legislators from across the political spectrum to build their capacity in advancing policies that can improve the health of Kansans.To that end, the academy helps legislators develop new skills to deliberate the ethics of health policy, use systems thinking to understand the long- and short-term effects of policy action and inaction, and engage in acts of civic leadership. The academy also seeks to foster an environment of respectful open dialogue and to build new cross-chamber and cross-party relationships.Among the most important outcomes cited by program participants is the value of sustained, personal interaction and problem solving with individuals holding differing political views.Health policy often elicits controversy. Recent examples include the uproar over recommendations for mammography screening for women 40 to 49 years old and human papillomavirus vaccination for adolescent girls and boys. Perhaps the most dramatic controversy relates to the passage of the Patient Protection and Affordable Care Act (Pub L No. 111-148); despite being signed into law in 2010 and found substantially constitutional by the US Supreme Court in 2012 (Medicaid expansion was made optional for states), this legislation remains subject to vigorous dissent. Such controversies, although no doubt a function of interest-driven politics, also reflect deep differences in ethical values.Ethical values and premises underpin all public policy.1,2 Ideas about individual liberty, personal responsibility, solidarity, justice, and the role of the government are just a few of the moral constructs that often clash in the making of policy. Policy analysis often ignores these dimensions of policy-making, although that is beginning to change.3–5Here we describe a project based in part on the premise that training policymakers to recognize and talk openly about the ethical values entailed in health policy might improve its content and process. This project, the Kansas Legislative Health Academy (hereafter Health Academy), brought together state legislators from across the political spectrum to build their capacity to respond to complex health policy challenges in Kansas. To that end, the curriculum sought to help legislators develop new skills in 3 areas: health policy ethics, systems thinking, and civic leadership. The Health Academy also sought to foster an environment of open, respectful dialogue and to build new cross-chamber and cross-party relationships.To our knowledge, the Health Academy is a unique program. Many educational programs exist for legislators to focus on leadership development or specific health policy issues, but none we are aware of are specifically designed to cover a broad range of health policy issues while also addressing underlying barriers to effective policy-making within legislative bodies. In what follows, we describe the Health Academy’s origins, structure, substance, and lessons learned.  相似文献   
64.
To address shortcomings of purely reaction-time based attention bias modification (ABM) paradigms, a novel eye-tracking based ABM training (ET-ABM) was developed. This training targets the late disengagement from negative stimuli and the lack of attention for positive information, which are characteristics of depression. In the present study, 75 dysphoric students (BDI?≥?9) were randomly assigned to either this positive training (PT), or a sham-training (ST) that did not train any valence-specific gaze pattern (positive and negative pictures had to be disengaged from and attended to equally often). Results showed that the PT induced a positive attentional bias (longer fixations of positive than negative pictures). Although the ST group showed an increase in positive attentional bias as well, this increase was not as strong as in the PT group. Compared to the ST, the PT specifically induced faster disengagement from negative pictures. No differential training effects were found on stress responses or state rumination. These results show that the ET-ABM successfully modifies attentional processes, specifically late disengagement from negative stimuli, in dysphoric students, and hence might be a promising alternative to existing ABM paradigms.  相似文献   
65.
66.
Limited data are available on the longitudinal occurrence of syndemic factors among women at risk for HIV infection in the USA and how these factors relate to sexual risk over time. HVTN 906 was a longitudinal study enrolling 799 HIV-uninfected women in three cities. Assessments were done at baseline, 6, 12, and 18 months to assess syndemic factors (low education, low income, unemployment, lack of health insurance, housing instability, substance use, heavy alcohol use, partner violence, incarceration) and sexual risk outcomes. For each sexual risk outcome, a GEE model was fit with syndemic factors or syndemic score (defined as sum of binary syndemics, ranging from 0 to 9), visit, study site, age and race/ethnicity as predictors to examine the multivariable association between syndemic factors and outcomes over time. Odds of unprotected sex while drunk or high were significantly higher when women reported lack of health insurance, substance and heavy alcohol use and partner violence. Housing instability, substance and heavy alcohol use, partner violence and recent incarceration were associated with higher odds of having multiple sexual partners. Odds of sex exchange were significantly higher in the presence of unemployment, housing instability, low education, lack of health insurance, substance and heavy alcohol use, partner violence and incarceration. Housing instability, substance and heavy alcohol use, and partner violence were significantly associated with higher odds of unprotected anal sex. Odds of having a recent STI were significantly higher when women reported housing instability and partner violence. There were significantly higher odds of the reporting of any risk outcomes during follow-up with higher syndemic score. This study highlights a group of women experiencing multiple poor social and health outcomes who need to be the focus of comprehensive interventions.  相似文献   
67.
AIDS and Behavior - In this mixed-methods study, we examine the relationship between provider communication and patient health literacy on HIV continuum of care outcomes among women living with HIV...  相似文献   
68.

Objectives

The aims of the present study were: 1) to investigate the contribution of the extent of luminal stenosis and other lesion composition-related factors in predicting invasive fractional flow reserve (FFR); and 2) to explore the distribution of various combinations of morphological characteristics and the severity of stenosis among lesions demonstrating normal and abnormal FFR.

Background

In patients with stable ischemic heart disease, FFR-guided revascularization, as compared with medical therapy alone, is reported to improve outcomes. Because morphological characteristics are the basis of plaque rupture and acute coronary events, a relationship between FFR and lesion characteristics may exist.

Methods

This is a subanalysis of NXT (HeartFlowNXT: HeartFlow Analysis of Coronary Blood Flow Using Coronary CT Angiography), a prospective, multicenter study of 254 patients (age 64 ± 10 years, 64% male) with suspected stable ischemic heart disease; coronary computed tomography angiography including plaque morphology assessment, invasive angiography, and FFR were obtained for 383 lesions. Ischemia was defined by invasive FFR ≤0.80. Computed tomography angiography–defined morphological characteristics of plaques and their vascular location were used in univariate and multivariate analyses to examine their predictive value for invasive FFR. The distribution of various combinations of plaque morphological characteristics and the severity of stenosis among lesions demonstrating normal and abnormal FFR were examined.

Results

The percentage of luminal stenosis, low-attenuation plaque (LAP) or necrotic core volume, left anterior descending coronary artery territory, and the presence of multiple lesions per vessel were the predictors of FFR. When grouped on the basis of degree of luminal stenosis, FFR-negative lesions had consistently smaller LAP volumes compared with FFR-positive lesions. The distribution of plaque characteristics in lesions with normal and abnormal FFR demonstrated that whereas FFR-negative lesions excluded likelihood of stenotic plaques with moderate to high LAP volumes, only one-third of FFR-positive lesions demonstrated obstructive plaques with moderate to high LAP volumes.

Conclusions

In addition to the severity of luminal stenosis, necrotic core volume is an independent predictor of FFR. The distribution of plaque characteristics among lesions with varying luminal stenosis and normal and abnormal FFR may explain the outcomes associated with FFR-guided therapy.  相似文献   
69.
The majority of rectal cancers have local disease only at presentation, but despite meticulous surgery, a number of factors will influence outcome. Preoperative identification of adverse prognostic factors provides a rational basis for selecting preoperative therapy. Thin section MRI can influence preoperative therapeutic algorithms by T and N staging, demonstrating operability, and the potential risk of circumferential margin involvement. Endosonography may contribute to this, but has a greater role in determining intramural invasion for early tumors. The assessment of residual tumor after chemoradiotherapy remains difficult; PET scanning has been used in this situation [32], but has not been compared with MRI and is unlikely to show only residual cells with extensive fibrosis.  相似文献   
70.

Background

Rural areas have historically struggled with shortages of healthcare providers; however, advanced communication technologies have transformed rural healthcare, and practice in underserved areas has been recognized as a policy priority. This systematic review aims to assess reasons for current providers’ geographic choices and the success of training programs aimed at increasing rural provider recruitment.

Methods

This systematic review (PROSPERO: CRD42015025403) searched seven databases for published and gray literature on the current cohort of US rural healthcare practitioners (2005 to March 2017). Two reviewers independently screened citations for inclusion; one reviewer extracted data and assessed risk of bias, with a senior systematic reviewer checking the data; quality of evidence was assessed using the GRADE approach.

Results

Of 7276 screened citations, we identified 31 studies exploring reasons for geographic choices and 24 studies documenting the impact of training programs. Growing up in a rural community is a key determinant and is consistently associated with choosing rural practice. Most existing studies assess physicians, and only a few are based on multivariate analyses that take competing and potentially correlated predictors into account. The success rate of placing providers-in-training in rural practice after graduation, on average, is 44% (range 20–84%; N = 31 programs). We did not identify program characteristics that are consistently associated with program success. Data are primarily based on rural tracks for medical residents.

Discussion

The review provides insight into the relative importance of demographic characteristics and motivational factors in determining which providers should be targeted to maximize return on recruitment efforts. Existing programs exposing students to rural practice during their training are promising but require further refining. Public policy must include a specific focus on the trajectory of the healthcare workforce and must consider alternative models of healthcare delivery that promote a more diverse, interdisciplinary combination of providers.
  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