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   44119篇
  免费   3119篇
  国内免费   865篇
耳鼻咽喉   237篇
儿科学   1798篇
妇产科学   1177篇
基础医学   6212篇
口腔科学   1231篇
临床医学   3158篇
内科学   9280篇
皮肤病学   694篇
神经病学   3487篇
特种医学   1985篇
外国民族医学   4篇
外科学   5936篇
综合类   2889篇
现状与发展   3篇
预防医学   3032篇
眼科学   426篇
药学   3599篇
  27篇
中国医学   846篇
肿瘤学   2082篇
  2024年   83篇
  2023年   604篇
  2022年   1422篇
  2021年   1874篇
  2020年   1517篇
  2019年   2535篇
  2018年   2483篇
  2017年   1645篇
  2016年   1232篇
  2015年   1266篇
  2014年   2185篇
  2013年   2165篇
  2012年   1515篇
  2011年   1659篇
  2010年   1348篇
  2009年   1428篇
  2008年   1336篇
  2007年   1197篇
  2006年   1141篇
  2005年   926篇
  2004年   841篇
  2003年   854篇
  2002年   624篇
  2001年   592篇
  2000年   547篇
  1999年   529篇
  1998年   414篇
  1997年   367篇
  1996年   319篇
  1995年   237篇
  1994年   209篇
  1993年   153篇
  1992年   135篇
  1991年   128篇
  1990年   107篇
  1989年   107篇
  1988年   100篇
  1985年   1009篇
  1984年   1796篇
  1983年   1100篇
  1982年   1226篇
  1981年   1191篇
  1980年   985篇
  1979年   881篇
  1978年   803篇
  1977年   684篇
  1976年   791篇
  1975年   558篇
  1974年   496篇
  1973年   552篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
ObjectivesVitamin D deficiency is prevalent among older adults. We aimed to study whether residential greenness could alter serum 25(OH)D concentrations as a possible mechanism of residential greenness's positive health effects.DesignA longitudinal cohort study.Setting and ParticipantsWe included older adults aged ≥65 years from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) with follow-up between 2012 and 2014.MethodsWe measured residential greenness by calculating annual average Normalized Difference Vegetation Index (NDVI) in a 500 m radius by using satellite images around each participant's residential address. Serum 25-hydroxyvitamin D (25(OH)D) concentration was dichotomized into 2 categories: nondeficiency (≥50 nmol/L) and deficiency (<50 nmol/L). We used the generalized estimating equation to examine the relationship between annual average NDVI and serum 25(OH)D.ResultsWe included 1336 participants in our analysis. The annual average NDVI was 0.49, and mean serum 25(OH)D was 43 nmol/L at baseline. Each 0.1-unit increase in annual average NDVI was associated with a 13% higher odds of vitamin D nondeficiency [95% confidence interval (CI): 1.01, 1.26]. The association was stronger among men [odds ratio (OR): 1.17, 95% CI: 1.02, 1.35] than women (OR: 1.08, 95% CI: 0.91, 1.29) and also stronger among those who were free of activities of daily living (ADL) disability at baseline (OR: 1.12, 95% CI: 1.00, 1.25). During the follow-up period, the participants who lived in greener areas were more likely to have an improved, rather than stable or deteriorated, vitamin D status (OR: 1.94, 95% CI: 1.51, 2.51).Conclusions and ImplicationsOur study suggests that higher levels of residential greenness are associated with higher serum 25(OH)D concentrations, which has implications for prevention of vitamin D deficiency among older adults.  相似文献   
23.
BackgroundHigher vitamin D status has been associated with symptom improvement and decreased risk of various autoimmune disorders. Our objective was to determine whether higher serum 25-hydroxyvitamin D (25OHD) concentration correlated with less severe first-diagnosed bullous pemphigoid (BP) in older inpatients.MethodsThis cross-sectional study was performed from November 2012 to February 2014 among 30 consecutive older inpatients (21 women; mean ± SD, 83 ± 7 years; all Caucasian) with a de novo diagnosis of active BP recruited in the Department of Dermatology of Angers University Hospital, France. The severity of BP was graded clinically on the basis of i) the number of bullae during the first three days of hospitalization (grade 0–4, worse), and ii) the extent of the lesions (grade 0–5, worse).ResultsSixteen participants had ≤ 5 bullae at the time of diagnosis, 8 had 6–20 bullae, 3 had 20–50 bullae, and 3 had >50 bullae. The lesions were spread over 5 cutaneous areas in 5 participants (17%). The median 25OHD concentration was 23 [IQR, 16–42] nmol/L. Serum 25OHD concentration was inversely correlated with the bullae grade (ρ = − 0.38, p = 0.04) and the lesion extension grade (ρ = − 0.50, p = 0.005).ConclusionsHigher serum 25OHD concentration correlated with less severe BP prior to initiation of treatment among our sample of older inpatients. This result suggests that vitamin D may be involved in the pathophysiology of BP and could serve as prognostic biomarker of BP.  相似文献   
24.

Background

Acute myocardial infarction (AMI) causes irreversible myocardial damage and release of inflammatory mediators, including cytokines, chemokines and miRNAs. We aimed to investigate changes in the levels of cytokines (IL-6, TNF-α and IL-10), miRNAs profiles (miR-146 and miR-155) and distribution of different monocyte subsets (CD14++CD16-, CD14++CD16+, CD14+CD16++) in the acute and post-healing phases of AMI.

Methods

In eighteen consecutive AMI patients (mean age 56.78?±?12.4 years, mean left ventricle ejection fraction – LVEF: 41.9?±?9.8%), treated invasively, monocyte subsets frequencies were evaluated (flow cytometry), cytokine concentrations were analyzed (ELISA) as well as plasma miRNAs were isolated twice – on admission and after 19.2?±?5.9 weeks of follow-up. Measurements were also performed among healthy volunteers.

Results

AMI patients presented significantly decreased frequencies of classical cells in comparison to healthy controls (median 71.22% [IQR: 64.4–79.04] vs. 84.35% [IQR: 81.2–86.7], p?=?0.001) and higher percent of both intermediate and non-classical cells, yet without statistical significance (median 6.54% [IQR: 5.14–16.64] vs. 5.87% [IQR: 4.48–8.6], p?=?0.37 and median 5.99% [IQR: 3.39–11.5] vs. 5.26% [IQR: 3.62–6.2], p?=?0.42, respectively). In AMI patients both, analyzed plasma miRNA concentrations were higher than in healthy subjects (miR-146: median 5.48 [IQR: 2.4–11.27] vs. 1.84 [IQR: 0.87–2.53], p?=?0.003; miR-155: median 25.35 [IQR: 8.17–43.15] vs. 8.4 [IQR: 0.08–16.9], p?=?0.027, respectively), and returned back to the values found in the control group in follow-up. miR-155/miR-146 ratio correlated with the frequencies of classical monocytes (r=0.6, p?=?0.01) and miR-155 correlated positively with the concentration of inflammatory cytokines ? IL-6 and TNF-α.

Conclusions

These results may suggest cooperation of both pro-inflammatory and anti-inflammatory signals in AMI in order to promote appropriate healing of the infarcted myocardium.  相似文献   
25.
Schizophrenia is a chronic and severe psychiatric disorder that has profound impact on an individual’s life and on society. Thus, developing more effective therapeutic interventions is essential. Over the past quarter‐century, an abundance of evidence from pharmacologic challenges, post‐mortem studies, brain imaging, and genetic studies supports the role of glutamatergic dysregulation in the pathophysiology of schizophrenia, and the results of recent randomized clinical trials based on this evidence have yielded promising results. In this article, we review the evidence that alterations in glutamatergic neurotransmission, especially focusing on the N‐methyl‐d ‐aspartate receptor (NMDAR) function, may be a critical causative feature of schizophrenia, how this contributes to pathologic circuit function in the brain, and how these insights are revealing whole new avenues for treatment development that could reduce treatment‐resistant symptoms, which account for persistent disability.  相似文献   
26.
目的:对比解剖性肝脏体积(ALV)和功能性肝脏体积(FLV)与肝功能Child-Pugh分级的相关性。方法:选择温州医科大学附属第二医院育英儿童医院2014年1月至2019年4月同时行增强CT和Gd-EOB-DTPA增强MRI扫描的肝硬化患者25例。对所有患者进行肝功能Child-Pugh评分,检测所有入组患者每个肝段的Gd-EOB-DTPA增强MRI平扫期和肝胆特异期的信号对比增强率(CER),以CT扫描的数据为基础利用MI-3DVS计算每个肝段的ALV和全肝的FLV。分析ALV和FLV与肝功能Child-Pugh分级的相关性。结果:肝功能Child-Pugh分级与ALV呈负相关(r=-0.792,P<0.001),曲线拟合的决定系数(R2)=0.63;肝功能Child-Pugh分级与FLV亦呈负相关(r=-0.911,P<0.001),曲线拟合的R2=0.80。FLV与肝功能Child-Pugh分级有更显著的负相关性。结论:结合Gd-EOB-DTPA增强MRI平扫期和肝胆特异期的信号CER和ALV计算所得的FLV较ALV能更好地反映肝脏的功能状态。  相似文献   
27.
2‐deoxy D‐glucose (2DG) was tested for efficacy in treating alopecia areata using the C3H/HeJ skin graft model. 2DG has proven to be efficacious in treatment of various mouse models of autoimmunity with minimal serious side effects noted. This agent has been shown to normalize abnormally activated T‐cell populations while also preventing cell surface expression of NKG2D; key factors defining alopecia areata disease progression. Daily oral ingestion of 2DG via drinking water to mice with patchy or diffuse alopecia areata for 16 weeks failed to prevent expansion of alopecia or cause regrowth of hair in treated mice. Histologically, there were no differences between treated and control groups. These results indicate that, while 2DG is effective for some autoimmune diseases, it was not efficacious for the cell‐mediated autoimmune mouse disease, alopecia areata.  相似文献   
28.
29.
30.
Vitamin D is responsible for multiple metabolic functions in humans. Rickets are the most common disease caused by vitamin D deficiency. It is caused by poor calcium intake resulting in poor serum-ionized calcium. The purpose of this study is to develop a rapid, sensitive, and feasible method to determine the 25-hydroxy-vitamin D3 (25(OH)D3) levels in blood samples for clinical assessment. In this study, gas chromatography coupled mass spectrometry with trimethylsilyl derivatization (TMS-GC-MS) is the most suitable protocol for quantitative analyses of 25(OH)D3. Performance of method was evaluated and compared with liquid chromatography and immunoassay. Method validation has been carried out with plasma specimens. The limit of quantitation of TMS-GC-MS method is 1.5 ppb with good linear correlation. Furthermore, the dietary intake and nutritional status of vegetarian and non-vegetarians in Taiwan were assessed by our validated method. As a result, this vitamin D nutrition survey demonstrates that most Taiwanese people have insufficient vitamin D. Due to dietary habits; the male vegans may have the highest risk of vitamin D deficiency.  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