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   1513篇
  免费   156篇
  国内免费   7篇
耳鼻咽喉   3篇
儿科学   69篇
妇产科学   21篇
基础医学   166篇
口腔科学   38篇
临床医学   204篇
内科学   313篇
皮肤病学   16篇
神经病学   69篇
特种医学   258篇
外科学   210篇
综合类   35篇
预防医学   79篇
眼科学   12篇
药学   98篇
中国医学   5篇
肿瘤学   80篇
  2023年   9篇
  2021年   21篇
  2020年   15篇
  2019年   16篇
  2018年   32篇
  2017年   18篇
  2016年   30篇
  2015年   30篇
  2014年   41篇
  2013年   41篇
  2012年   38篇
  2011年   42篇
  2010年   43篇
  2009年   73篇
  2008年   54篇
  2007年   29篇
  2006年   37篇
  2005年   23篇
  2004年   37篇
  2003年   42篇
  2002年   34篇
  2001年   30篇
  2000年   39篇
  1999年   29篇
  1998年   57篇
  1997年   55篇
  1996年   66篇
  1995年   51篇
  1994年   52篇
  1993年   57篇
  1992年   32篇
  1991年   17篇
  1990年   26篇
  1989年   36篇
  1988年   49篇
  1987年   43篇
  1986年   44篇
  1985年   30篇
  1984年   23篇
  1983年   20篇
  1982年   30篇
  1981年   21篇
  1980年   18篇
  1979年   16篇
  1978年   13篇
  1977年   20篇
  1976年   19篇
  1975年   18篇
  1972年   6篇
  1968年   11篇
排序方式: 共有1676条查询结果,搜索用时 15 毫秒
71.
To understand the hematopoietic and nonhematopoietic responses to interleukin-3 (IL-3), expression of cell-surface IL-3 receptors (IL-3R) was examined on bone marrow (BM) cells and peripheral blood (PB) cells of rhesus monkeys during the course of in vivo IL-3 treatment. Whereas IL-3R expression is low in untreated monkeys, IL-3 administration led to a gradual increase in both low- and high-affinity binding sites for IL-3. This increase reflected the total number of cells expressing IL- 3Rs, as detected by flow cytometry using biotinylated IL-3. Most of these IL-3R+ cells in both BM and PB could be characterized as basophilic granulocytes that contained high levels of histamine. In contrast to the effect on these differentiated cells, IL-3 administration did not significantly alter the low level IL-3R expression on immature, CD34+ cells. Further flow cytometric analysis using biotinylated growth factors showed that the IL-3R+ basophils also expressed receptors for granulocyte-macrophage colony-stimulating factor (GM-CSF), but not for IL-6 or Kit ligand. These findings indicated that the IL-3R+ cells included neither monocytes, which express GM-CSFRs and IL-6Rs abundantly, nor mast cells, which express c- kit. By combining flow cytometric and Scatchard data, it was calculated that the basophils contain as many as 1 to 2 x 10(3) high-affinity IL- 3Rs and 15 to 30 x 10(3) low-affinity sites. The finding that in vivo IL-3 treatment leads to the production of large numbers of cells that express high levels of IL-3R and are capable of producing histamine provides an explanation for the often severe allergic reactions that occur during prolonged IL-3 administration. It also indicates that IL- 3, in addition to its direct effects on hematopoietic cells, may also stimulate hematopoiesis through the release of secondary mediators such as histamine by IL-3-responsive mature cells.  相似文献   
72.
PURPOSE: The purpose of this study was to compare the sociodemographics, self-rated health, and involvement levels of family caregivers of residents with dementia in residential care/assisted living (RC/AL) versus nursing home settings. DESIGN AND METHODS: We conducted telephone interviews with the family caregivers most involved with 353 residents of 34 residential care and 10 nursing home facilities. We measured involvement by caregiver self-report of monthly out-of-pocket spending, involvement and burden ratings, and the frequency of engaging in eight specific care activities. Open-ended questions elicited areas in which caregivers preferred different involvement and ways the facility could facilitate involvement. RESULTS: Nursing home caregivers rated their health poorer than RC/AL caregivers, but there were no sociodemographic differences between the two. RC/AL caregivers rated both their perception of involvement and burden higher and engaged more frequently in monitoring the resident's health, well-being, and finances than did nursing home caregivers, although the reported time spent per week on care did not differ. IMPLICATIONS: RC/AL and nursing home caregivers to residents with dementia may tailor their care to fit the needs of the resident and setting. Results are discussed in relation to the Congruence Model of Person-Environment Fit.  相似文献   
73.
74.

Background

Adolescent idiopathic scoliosis (AIS) is a complex genetic disorder that causes spinal deformity in approximately 3% of the population. Candidate gene, linkage, and genome-wide association studies have sought to identify genetic variation that predisposes individuals to AIS, but the genetic basis remains unclear. Copy number variants are associated with several isolated skeletal phenotypes, but their role in AIS, to our knowledge, has not been assessed.

Questions/Purposes

We determined the frequency of recurrent copy number rearrangements, chromosome aneuploidy, and rare copy number variants in patients with AIS.

Methods

Between January 2010 and August 2014, we evaluated 150 patients with isolated AIS and spinal curvatures measuring 10° or greater, and 148 agreed to participate. Genomic copy number analysis was performed on patients and 1079 control subjects using the Affymetrix® Genome-wide Human SNP Array 6.0. After removing poor quality samples, 143 (97%) patients with AIS were evaluated for copy number variation.

Results

We identified a duplication of chromosome 1q21.1 in 2.1% (N = 3/143) of patients with AIS, which was enriched compared with 0.09% (N = 1/1079) of control subjects (p = 0.0057) and 0.07% (N = 6/8329) of a large published control cohort (p = 0.0004). Other notable findings include trisomy X, which was identified in 1.8% (N = 2/114) of female patients with AIS, and rearrangements of chromosome 15q11.2 and 16p11.2 that previously have been associated with spinal phenotypes. Finally, we report rare copy number variants that will be useful in future studies investigating candidate genes for AIS.

Conclusions

Copy number variation and chromosomal aneuploidy may contribute to the pathogenesis of adolescent idiopathic scoliosis.

Clinical Relevance

Chromosomal microarray may reveal clinically useful abnormalities in some patients with AIS.  相似文献   
75.
76.
77.
78.
We compared subgroup differences in COVID-19 case and mortality and investigated factors associated with case and mortality rate (MR) measured at the county level in Mississippi. Findings were based on data published by the Mississippi State Department of Health between March 11 and July 16, 2020. The COVID-19 case rate and case fatality rate (CFR) differed by gender and race, while MR only differed by race. Residents aged 80 years or older and those who live in a non-metro area had a higher case rate, CFR, and MR. After controlling for selected factors, researchers found that the percent of residents who are obese, low income, or with certain chronic conditions were associated with the county COVID-19 case rate, CFR, and/or MR, though some were negatively related. The findings may help the state to identify counties with higher COVID-19 case rate, CFR, and MR based on county demographics and the degree of its chronic conditions.  相似文献   
79.
BackgroundPeriodontal disease is a major cause of tooth loss. Few studies have evaluated the residual area of the periodontal ligament in extracted teeth and, to the best of our knowledge, none from Latin America have done so regarding indications for extraction. The aim of this study was to evaluate the residual periodontal ligament (RPL) with respect to indication for extraction in a sample of teeth from a Brazilian Public Health Service district.Materials and methodsAll teeth extracted within the Public Health Service district of Santa Maria, Brazil, over a 5-month period were requested for analysis. A total of 414 teeth eligible for measurement were stained and evaluated for RPL using a stereo microscope. Participating Public Health Service dentists completed a questionnaire detailing demographic variables and indication for each extracted tooth. The percentage of RPL was determined for each tooth. Comparisons of RPL between teeth extracted on periodontal versus other indications were made using the Mann-Whitney test.ResultsRPL averaged 34.8% for teeth extracted on periodontal indications versus 79.5% for other teeth (P ≤ 0.001). When considering teeth with an RPL ≥ 30% as possible to maintain, 189 (76%) of the teeth extracted on periodontal indications could have been maintained. When RPL cut-off limits of ≥ 40% or ≥ 50% are applied, 93 (37%) and 43 (17%) teeth, respectively, could have been maintained.ConclusionThis study suggests that strictly based on RPL, a large number of teeth extracted on periodontal indications conceivably could be maintained.Key words: Cross-sectional studies, Prognosis, Tooth extraction, Tooth loss  相似文献   
80.
ObjectiveThis study assessed levels of anxiety, depression, and stress among family caregivers of children and adolescents with mental disorders in Ghana and the implication on medication adherence.DesignA cross-sectional study.SettingThe study was conducted at the outpatient departments of the three main public psychiatric hospitals in Ghana.ParticipantsTwo hundred and ten non-paid family caregivers of children and adolescents with mental disorders were recruited for this study.Main Outcome MeasureThe study assessed symptoms of anxiety, depression and stress among the caregivers and estimated caregiver-reported medication adherence.ResultsAbout 56.2%, 66.2% and 78% of the caregivers experienced severe anxiety, severe depression and moderate to severe stress symptoms respectively. From the multiple logistic regression model, while anxiety was significantly affected by religion and education, depression was influenced by sex, age, marital status, proximity to facility, and employment status. Female caregivers had about four times higher odds of being depressed compared to male caregivers (aOR: 3.81, 95% CI: 1.66 – 8.75). The caregiver-reported medication adherence was 11.9%. Anxiety was significantly predictive of medication adherence.ConclusionMost family caregivers of children and adolescents with mental disorders experienced symptoms of anxiety, depression and stress with anxiety having implications for medication adherence. The study findings underscore the need to consider psychological characteristics of caregivers and the provision of mental health support for them, as part of the routine health care for children and adolescents with mental disorders.FundingNone indicated  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