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   5242篇
  免费   326篇
  国内免费   14篇
耳鼻咽喉   64篇
儿科学   191篇
妇产科学   242篇
基础医学   601篇
口腔科学   34篇
临床医学   591篇
内科学   963篇
皮肤病学   65篇
神经病学   580篇
特种医学   118篇
外科学   562篇
综合类   44篇
一般理论   12篇
预防医学   699篇
眼科学   108篇
药学   305篇
中国医学   3篇
肿瘤学   400篇
  2023年   46篇
  2022年   39篇
  2021年   150篇
  2020年   89篇
  2019年   175篇
  2018年   180篇
  2017年   125篇
  2016年   114篇
  2015年   141篇
  2014年   187篇
  2013年   302篇
  2012年   434篇
  2011年   425篇
  2010年   225篇
  2009年   200篇
  2008年   365篇
  2007年   341篇
  2006年   365篇
  2005年   334篇
  2004年   297篇
  2003年   242篇
  2002年   243篇
  2001年   49篇
  2000年   38篇
  1999年   39篇
  1998年   35篇
  1997年   34篇
  1996年   24篇
  1995年   27篇
  1994年   31篇
  1993年   18篇
  1992年   25篇
  1991年   29篇
  1990年   14篇
  1989年   22篇
  1988年   17篇
  1987年   19篇
  1986年   9篇
  1985年   15篇
  1984年   18篇
  1983年   14篇
  1982年   9篇
  1981年   7篇
  1980年   7篇
  1979年   8篇
  1978年   5篇
  1977年   8篇
  1976年   5篇
  1975年   7篇
  1972年   5篇
排序方式: 共有5582条查询结果,搜索用时 156 毫秒
61.
AbstractMeeting recruitment targets for clinical trials and health research studies is a notable challenge. Unsuccessful efforts to recruit participants from traditionally underserved populations can limit who benefits from scientific discovery, thus perpetuating inequities in health outcomes and access to care. In this study, we evaluated direct mail and email outreach campaigns designed to recruit women who gave birth in North Carolina for a statewide research study offering expanded newborn screening for a panel of rare health conditions. Of the 54,887 women who gave birth in North Carolina from September 28, 2018, through March 19, 2019, and were eligible to be included on the study’s contact lists, we had access to a mailing address for 97.9% and an email address for 6.3%. Rural women were less likely to have sufficient contact information available, but this amounted to less than a one percentage point difference by urbanicity. Native American women were less likely to have an email address on record; however, we did not find a similar disparity when recruitment using direct‐mail letters and postcards was concerned. Although we sent letters and emails in roughly equal proportion by urbanicity and race/ethnicity, we found significant differences in enrollment across demographic subgroups. Controlling for race/ethnicity and urbanicity, we found that direct‐mail letters and emails were effective recruitment methods. The enrollment rate among women who were sent a recruitment letter was 4.1%, and this rate increased to 5.0% among women who were also sent an email invitation. Study Highlights
  • WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC?
Under‐representation by traditionally underserved populations in clinical trials and health research is a challenge that may in part reflect inequitable opportunities to participate.
  • WHAT QUESTION DID THIS STUDY ADDRESS?
Are direct‐mail and email outreach strategies effective for reaching and recruiting women from traditionally underserved and rural populations to participate in large‐scale, population‐based research?
  • WHAT DOES THIS STUDY ADD TO OUR KNOWLEDGE?
Despite sending recruitment letters and email invitations in roughly equal proportion by urbanicity and race/ethnicity, women living in rural areas were less likely to enroll (2.8%) than women from urban areas (4.2%). Additionally, enrollment rates decreased as the probability that women were members of a racial or ethnic minority group increased.
  • HOW MIGHT THIS CHANGE CLINICAL PHARMACOLOGY OR TRANSLATIONAL SCIENCE?
Results from this study might encourage researchers to take a holistic and participant‐centered view of barriers to study enrollment that may disproportionately affect underserved communities, including differences in willingness to participate, trust, and access to resources needed for uptake.  相似文献   
62.
BACKGROUND: The Delphi method provides an opportunity for experts (panelists) to communicate their opinions and knowledge anonymously about a complex problem, to see how their evaluation of the issue aligns with others, and to change their opinions, if desired, after reconsideration of the findings of the group's work. Delphi studies have the potential to provide valuable information, yet few researchers have taken further steps to support or refine their findings. Without this step there is a potential threat to the applicability, or external validity, of the results. AIMS: The purpose of this article is to present an argument for further inquiry to enhance and support Delphi findings, and specific approaches to this will be considered. METHODS: Methods to enhance, expand, or refine Delphi study findings are described. Mixed method design within a Delphi study on midwifery practice is described, and a follow-up narrative study to examine the findings is presented. FINDINGS: Selected results from the follow up narrative study are presented to convey how the narrative data clarified the Delphi findings. Together, the studies provide a more robust depiction of midwifery practice, process, and outcomes. Although there were similarities to the dimensions identified previously, there was a more dynamic focus and explanation of the interaction between the midwife, the woman who had received midwifery care, and the health care system. STUDY LIMITATIONS: Lack of diversity in the sample and the midwives' familiarity with the author's past research represent a potential threat to the findings. Prolonged interviews and multiple narratives were gathered in an effort to control for this. CONCLUSION: Delphi studies are research exercises conducted by a panel of experts. Designing studies to further enhance, clarify, or refine their findings from the context of practice holds promise for their ability to influence clinical care.  相似文献   
63.

Background

ST-elevation myocardial infarction (STEMI) leading to cardiac arrest is an exceptionally rare occurrence in young adults. Those affected tend to abuse sympathomimetic drugs, have strong family histories, or have a significant burden of cardiac risk factors. Another uncommon cause of STEMI is coronary artery dissection, which overwhelmingly affects middle- and older-aged women with few cardiac risk factors.

Case Report

A 22-year-old athlete with no medical history was admitted to our institution post–cardiac arrest with an anterior STEMI and concomitant right coronary dissection. To our knowledge, this represents the first documented case of these simultaneous pathologies in a young cardiac arrest survivor.

Why Should an Emergency Physician Be Aware of This?

Myocardial infarction is rare in young adults, and a diverse range of etiologies must be considered promptly to prevent delays in time-sensitive therapies, such as antiplatelet agents and revascularization. The emergency physician is most often the first point of contact in patients with acute coronary syndromes, and the failure to recognize it in young adults threatens them with premature death and potentially life-long disability.  相似文献   
64.
Constipation is prevalent in pediatric oncology patients because of treatment with vinca alkaloids and/or narcotics and lifestyle changes secondary to disease process. Sequelae of constipation include anorexia, nausea, vomiting, abdominal pain, emergency department visits, and a decrease in quality of life. There are no reliable instruments to measure constipation in children. A pilot study (N = 21) evaluating the presence and severity of constipation and the reliability and validity of a modified version of the adult Constipation Assessment Scale (CAS) in children with cancer was conducted. Patients receiving weekly vinca alkaloids and/or narcotics = 2 times per day were recruited. Initial bowel function assessments included standardized nursing and nutrition assessments, history/physical review, and baseline CAS score repeated at 1 hour to assess test-retest reliability. Subsequent assessments included CAS administered 3 times per week and daily patient bowel diaries. Test-retest reliability was evident (r = .93; P = .000). Acceptable construct validity was indicated by a difference in mean CAS scores (t = 4.4, P <.001). Patients reported difficulty with CAS questions and response selections. Symptoms asked on CAS were often not viewed as a problem.  相似文献   
65.
Colorectal cancer (CRC) is the second leading cause of cancer death in the USA. Accumulation of beta-catenin protein is nearly ubiquitous in colon adenomas and cancers, presumably due to mutations in the APC or beta-catenin genes that inhibit proteasome-dependent degradation of beta-catenin protein. Substantial clinical, epidemiological, and animal evidence indicate that sulindac and other non-steroidal anti-inflammatory drugs (NSAIDs) prevent the development of CRC. The mechanisms by which sulindac exerts its potent growth inhibitory effects against colon tumor cells are incompletely understood, but down-regulation of beta-catenin has been suggested as one potential mechanism. The goal of this study was to determine the mechanism of beta-catenin protein down-regulation by sulindac metabolites. Treatment of human colon cancer cell lines with apoptotic concentrations of sulindac metabolites (sulindac sulfide, sulindac sulfone) induced a dose- and time-dependent inhibition of beta-catenin protein expression. Inhibition of proteasome activity with MG-132 partially blocked the ability of sulindac sulfide and sulindac sulfone to inhibit beta-catenin protein expression. Pretreatment with the caspase inhibitor z-VAD-fmk blocked morphological signs of apoptosis as well as caspase cleavage, and also partially prevented beta-catenin degradation by sulindac metabolites. These effects occurred in cells with bi-allelic APC mutation (SW480), with wild-type APC but mono-allelic beta-catenin mutation (HCT116) and in cells that lack expression of either COX-1 or -2 (HCT15). These results indicate that loss of beta-catenin protein induced by sulindac metabolites is COX independent and at least partially due to reactivation of beta-catenin proteasome degradation and partially a result of caspase activation during the process of apoptosis.  相似文献   
66.
Introduction: Histone deacetylases (HDACs) have been implicated in neurogenic muscle atrophy, but the mechanisms by which HDAC inhibitors might have beneficial effects are not defined. Methods: We used sciatic nerve crush to determine the effect of butyrate on denervation‐induced gene expression and oxidative stress. Results: Butyrate treatment initiated 3 weeks before injury and continued 1 week after injury increases histone acetylation and reduces muscle atrophy after nerve crush. Butyrate delivered only after nerve crush similarly prevented muscle atrophy. Butyrate had no effect on the increase in histone deacetylase 4 (HDAC4) protein levels following nerve crush but prevented the increase in expression of myogenin, MuRF1, and atrogin‐1. Butyrate did not affect mitochondrial reactive oxygen species production, but it increased antioxidant enzyme activity, reduced proteasome activity, and reduced oxidative damage following nerve injury. Conclusions: These data suggest that HDAC inhibitors are promising pharmacological agents for treating neurogenic muscle atrophy. Muscle Nerve 52: 859–868, 2015  相似文献   
67.
The trajectory of the developing brain is characterized by a sequence of complex, nonlinear patterns that occur at systematic stages of maturation. Although significant prior neuroimaging research has shed light on these patterns, the challenge of accurately characterizing brain maturation, and identifying areas of accelerated or delayed development, remains. Altered brain development, particularly during the earliest stages of life, is believed to be associated with many neurological and neuropsychiatric disorders. In this work, we develop a framework to construct voxel‐wise estimates of brain age based on magnetic resonance imaging measures sensitive to myelin content. 198 myelin water fraction (VFM) maps were acquired from healthy male and female infants and toddlers, 3 to 48 months of age, and used to train a sigmoidal‐based maturational model. The validity of the approach was then established by testing the model on 129 different VFM datasets. Results revealed the approach to have high accuracy, with a mean absolute percent error of 13% in males and 14% in females, and high predictive ability, with correlation coefficients between estimated and true ages of 0.945 in males and 0.94 in females. This work represents a new approach toward mapping brain maturity, and may provide a more faithful staging of brain maturation in infants beyond chronological or gestation‐corrected age, allowing earlier identification of atypical regional brain development. Hum Brain Mapp 36:1233–1244, 2015. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc .  相似文献   
68.
69.

Background

Knowledge of molecular biology and genomics continues to expand rapidly, promising numerous opportunities for improving health. However, a key aspect of the success of genomic medicine is related to public understanding and acceptance.

Design

Using community consultations and an online survey, we explored public attitudes and expectations about genomics research.

Results

Thirty‐three members of the general public in Newfoundland, Canada, took part in the community sessions, while 1024 Atlantic Canadians completed the online survey. Overall, many participants noted they lacked knowledge about genetics and associated research and took the opportunity to ask numerous questions throughout sessions. Participants were largely hopeful about genomics research in its capacity to improve health, not only for current residents, but also for future generations. However, they did not accept such research uncritically, and a variety of complex issues and questions arose during the community consultations and were reflected in survey responses.

Discussion

With the proliferation of biobanks and the rapid pace of discoveries in genomics research, public support will be crucial to realize health improvements. If researchers can engage the public in regular, transparent dialogue, this two‐way communication could allow greater understanding of the research process and the design of efficient and effective genetic health services, informed by the public that will use them.  相似文献   
70.
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