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   2569篇
  免费   233篇
  国内免费   2篇
耳鼻咽喉   19篇
儿科学   105篇
妇产科学   74篇
基础医学   355篇
口腔科学   23篇
临床医学   305篇
内科学   488篇
皮肤病学   50篇
神经病学   271篇
特种医学   69篇
外科学   243篇
综合类   28篇
一般理论   6篇
预防医学   406篇
眼科学   47篇
药学   151篇
肿瘤学   164篇
  2024年   4篇
  2023年   27篇
  2022年   40篇
  2021年   104篇
  2020年   65篇
  2019年   81篇
  2018年   93篇
  2017年   71篇
  2016年   93篇
  2015年   85篇
  2014年   105篇
  2013年   123篇
  2012年   214篇
  2011年   234篇
  2010年   119篇
  2009年   99篇
  2008年   174篇
  2007年   167篇
  2006年   165篇
  2005年   176篇
  2004年   132篇
  2003年   126篇
  2002年   118篇
  2001年   8篇
  2000年   7篇
  1999年   15篇
  1998年   19篇
  1997年   12篇
  1996年   10篇
  1995年   12篇
  1994年   11篇
  1993年   8篇
  1992年   8篇
  1991年   8篇
  1990年   6篇
  1989年   2篇
  1988年   7篇
  1987年   2篇
  1986年   4篇
  1985年   9篇
  1984年   6篇
  1983年   7篇
  1982年   3篇
  1981年   4篇
  1980年   3篇
  1979年   3篇
  1975年   2篇
  1972年   2篇
  1970年   3篇
  1919年   1篇
排序方式: 共有2804条查询结果,搜索用时 265 毫秒
91.

Background

Youth mentoring programs rely largely on volunteers, but youth facing significant risks may be poor candidates for volunteer-based interventions. Full-time “professional” mentors in highly structured programs may be better suited to partner effectively with such youth and their families, but few studies examine professional mentoring interventions. Because of mentoring’s inherent flexibility, mentors’ role conceptualizations can profoundly influence the nature of their work. Serving as a professional mentor may have important implications for how mentors conceptualize and perform their role.

Objective

This qualitative study examined the role conceptions of professional mentors serving at-risk youth.

Methods

Semi-structured interviews with mentors were transcribed, coded, and subjected to thematic analysis.

Results

Mentors described the importance of “professionalism” in prioritizing mentoring, expending considerable effort, and performing difficult or unpleasant tasks. They reported that serving multiple children full-time enabled them to rapidly build expertise, that credibility and authority granted them because of their professional status facilitated their work across multiple key contexts, and that their expertise and long-term commitment facilitated the development of deep relationships. Mentors perceived their role as highly challenging but reported high self-efficacy. They described high multifaceted organizational support, a community for youth, and an individualized child focus.

Conclusions

A mentoring model delivered by experienced professional mentors may hold promise for working with youth at high risk. The role conceptualizations of mentors and the organizational culture within which mentors work may be important in helping youth succeed.  相似文献   
92.
Over the past few years, increasing public and political pressure has supported legalization of medical marijuana. One of the main thrusts in this effort has related to the treatment of refractory epilepsy—especially in children with Dravet syndrome—using cannabidiol (CBD). Despite initiatives in numerous states to at least legalize possession of CBD oil for treating epilepsy, little published evidence is available to prove or disprove the efficacy and safety of CBD in patients with epilepsy. This review highlights some of the basic science theory behind the use of CBD, summarizes published data on clinical use of CBD for epilepsy, and highlights issues related to the use of currently available CBD products.Cannabidiol is the major nonpsychoactive component of Cannabis sativa. Over the centuries, a number of medicinal preparations derived from C. sativa have been employed for a variety of disorders, including gout, rheumatism, malaria, pain, and fever. These preparations were widely employed as analgesics by Western medical practitioners in the 19th century (1). More recently, there is clinical evidence suggesting efficacy in HIV-associated neuropathic pain, as well as spasms associated with multiple sclerosis (1).  相似文献   
93.
94.
Rare variant tests have been of great interest in testing genetic associations with diseases and disease‐related quantitative traits in recent years. Among these tests, the sequence kernel association test (SKAT) is an omnibus test for effects of rare genetic variants, in a linear or logistic regression framework. It is often described as a variance component test treating the genotypic effects as random. When the linear kernel is used, its test statistic can be expressed as a weighted sum of single‐marker score test statistics. In this paper, we extend the test to survival phenotypes in a Cox regression framework. Because of the anticonservative small‐sample performance of the score test in a Cox model, we substitute signed square‐root likelihood ratio statistics for the score statistics, and confirm that the small‐sample control of type I error is greatly improved. This test can also be applied in meta‐analysis. We show in our simulation studies that this test has superior statistical power except in a few specific scenarios, as compared to burden tests in a Cox model. We also present results in an application to time‐to‐obesity using genotypes from Framingham Heart Study SNP Health Association Resource.  相似文献   
95.
Cellular plasticity is a topical subject with interest spanning a wide range of fields from developmental biology to regenerative medicine. Even the nomenclature is a subject of debate, and the underlying mechanisms are still under investigation. On top of injury repair, cell plasticity is a constant physiological process in adult organisms and tissues, in response to homeostatic challenges. In this review we discuss two examples of plasticity for the maintenance of homeostasis in the renal system—namely the renin‐producing juxtaglomerular cells (JG cells) and cortical collecting duct (CCD) cells. JG cells show plasticity through recruitment mechanisms, answering the demand for an increase in renin production. In the CCD, cells appear to have the ability to transdifferentiate between principal and intercalated cells to help maintain the highly regulated solute transport levels of that segment. These two cases highlight the complexity of plasticity processes and the role they can play in the kidney.  相似文献   
96.
ObjectiveTo determine how many patients with chronic osteoarthritis pain respond to various non-surgical treatments.Data sourcesPubMed and the Cochrane Library.Study selection Published systematic reviews of randomized controlled trials (RCTs) that included meta-analysis of responder outcomes for at least 1 of the following interventions were included: acetaminophen, oral nonsteroidal anti-inflammatory drugs (NSAIDs), topical NSAIDs, serotonin-norepinephrine reuptake inhibitors (SNRIs), tricyclic antidepressants, cannabinoids, counseling, exercise, platelet-rich plasma, viscosupplementation, glucosamine, chondroitin, intra-articular corticosteroids, rubefacients, or opioids.Synthesis In total, 235 systematic reviews were included. Owing to limited reporting of responder meta-analyses, a post hoc decision was made to evaluate individual RCTs with responder analysis within the included systematic reviews. New meta-analyses were performed where possible. A total of 155 RCTs were included. Interventions that led to more patients attaining meaningful pain relief compared with control included exercise (risk ratio [RR] of 2.36; 95% CI 1.79 to 3.12), intra-articular corticosteroids (RR = 1.74; 95% CI 1.15 to 2.62), SNRIs (RR = 1.53; 95% CI 1.25 to 1.87), oral NSAIDs (RR = 1.44; 95% CI 1.36 to 1.52), glucosamine (RR = 1.33; 95% CI 1.02 to 1.74), topical NSAIDs (RR = 1.27; 95% CI 1.16 to 1.38), chondroitin (RR = 1.26; 95% CI 1.13 to 1.41), viscosupplementation (RR = 1.22; 95% CI 1.12 to 1.33), and opioids (RR = 1.16; 95% CI 1.02 to 1.32). Preplanned subgroup analysis demonstrated no effect with glucosamine, chondroitin, or viscosupplementation in studies that were only publicly funded. When trials longer than 4 weeks were analyzed, the benefits of opioids were not statistically significant.ConclusionInterventions that provide meaningful relief for chronic osteoarthritis pain might include exercise, intra-articular corticosteroids, SNRIs, oral and topical NSAIDs, glucosamine, chondroitin, viscosupplementation, and opioids. However, funding of studies and length of treatment are important considerations in interpreting these data.  相似文献   
97.
98.
99.
Chemokines, including chemokine (C-X-C motif) ligand 1 (CXCL1), may enhance tumor epithelial-stromal interactions facilitating tumor growth and invasion. Studies have linked CXCL1 expression to gastric, colon and skin cancers, however, no study to date has been reported describing CXCL1 in human prostate tumors. Herein, we set out to describe the expression pattern of CXCL1 in human prostate tumors.  相似文献   
100.
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