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   52437篇
  免费   3780篇
  国内免费   257篇
耳鼻咽喉   517篇
儿科学   1915篇
妇产科学   1365篇
基础医学   7991篇
口腔科学   789篇
临床医学   5050篇
内科学   11675篇
皮肤病学   1173篇
神经病学   5876篇
特种医学   1116篇
外科学   4338篇
综合类   294篇
现状与发展   1篇
一般理论   43篇
预防医学   4775篇
眼科学   858篇
药学   4026篇
中国医学   136篇
肿瘤学   4536篇
  2024年   67篇
  2023年   618篇
  2022年   461篇
  2021年   2420篇
  2020年   1398篇
  2019年   1792篇
  2018年   1969篇
  2017年   1593篇
  2016年   1753篇
  2015年   1902篇
  2014年   2472篇
  2013年   3103篇
  2012年   4563篇
  2011年   4565篇
  2010年   2422篇
  2009年   2067篇
  2008年   3450篇
  2007年   3440篇
  2006年   3108篇
  2005年   2826篇
  2004年   2622篇
  2003年   2337篇
  2002年   2106篇
  2001年   246篇
  2000年   187篇
  1999年   255篇
  1998年   335篇
  1997年   285篇
  1996年   195篇
  1995年   184篇
  1994年   181篇
  1993年   140篇
  1992年   98篇
  1991年   83篇
  1990年   65篇
  1989年   76篇
  1988年   73篇
  1987年   64篇
  1986年   60篇
  1985年   60篇
  1984年   83篇
  1983年   66篇
  1982年   77篇
  1981年   64篇
  1980年   60篇
  1979年   29篇
  1978年   31篇
  1977年   34篇
  1976年   25篇
  1974年   19篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
991.
992.
993.

Purpose

The pharmacokinetic (PK) parameters of many drugs are altered as a consequence of the pathophysiological changes associated with critical illness. The critically ill population presents challenges when titrating infusions of sedatives and analgesics to maintain optimal sedation and pain levels. This systematic review examined the PK data in critically ill adult patients with prolonged infusions (>24 hours) of commonly used sedatives and analgesics to highlight possible altered PK parameters compared with noncritically ill patients.

Methods

A literature search of PK studies was performed by using MEDLINE (1946–December 2017) and EMBASE (1910–December 2017); we identified further studies by citation tracking (Web of Science) and checked references of retrieved studies and review articles. All studies were included that were published in English, Chinese, or German; conducted in critically ill adult patients receiving lorazepam, midazolam, propofol, dexmedetomidine, sufentanil, alfentanil, remifentanil, morphine, or fentanyl infusion for ≥24 hours; and reported PK parameters. When appropriate, we conducted a meta-analysis on volume of distribution at steady state (Vdss) (liters), clearance (Cl) (liters per hour), and elimination t1/2 (hours) by using a DerSimonian-Laird random effects model to estimate the summary mean and 95% CIs. Results were compared with commonly reported PK ranges in 70-kg noncritically ill patients.

Findings

Thirty-three randomized controlled trials and prospective cohort studies were identified involving 1803 adult critically ill patients with 35 drug treatment arms: fifteen midazolam (n?=?906) studies, three dexmedetomidine (n?=?561), nine propofol (n?=?165), four lorazepam (n?=?86), one morphine (n?=?20), two remifentanil (n?=?55), and one sufentanil (n?=?10). Each study showed large variations in Vdss, Cl, and elimination t1/2 within and between individual participants. High clinical and methodical heterogeneity between the dexmedetomidine studies prevented the direct comparison of PK parameters between critically ill and noncritically ill patients. Use of midazolam, propofol, and lorazepam in critically ill patients was associated with at least a 2- to 4-fold increase in Vdss compared with noncritically ill patients; Cl decreased ~2-fold for midazolam and 10-fold for morphine. Critically ill patients receiving prolonged infusions of midazolam, propofol, remifentanil, and sufentanil had at least 2-fold longer elimination or terminal t1/2 than noncritically ill patients.

Implications

These findings show a marked difference in many PK parameters from those reported for noncritically ill patients. Initiatives to improve the delivery of prolonged sedatives and analgesic infusions should be informed by PK parameters (Vdss, context-sensitive t1/2, and elimination t1/2) and data derived from critically ill patients.  相似文献   
994.

Background

Various endocrine signals oscillate over the 24‐hour period and so does the responsiveness of target tissues. These daily oscillations do not occur solely in response to external stimuli but are also under the control of an intrinsic circadian clock.

Design

We searched the PubMed database to identify studies describing the associations of clock genes with endocrine diseases.

Results

Various human single nucleotide polymorphisms of brain and muscle ARNT‐like 1 (BMAL1) and Circadian Locomotor Output Cycles Kaput (CLOCK) genes exhibited significant associations with type 2 diabetes mellitus. ARNTL2 gene expression and upregulation of BMAL1 and PER1 were associated with the development of type 1 diabetes mellitus. Thyroid hormones modulated PER2 expression in a tissue‐specific way, whereas BMAL1 regulated the expression of type 2 iodothyronine deiodinase in specific tissues. Adrenal gland and adrenal adenoma expressed PER1, PER2, CRY2, CLOCK and BMAL1 genes. Adrenal sensitivity to adrenocorticotrophin was also affected by circadian oscillations. A significant correlation between the expression of propio‐melanocorticotrophin and PER 2, as well as between prolactin and CLOCK, was found in corticotroph and lactosomatotroph cells, respectively, in the pituitary. Clock genes and especially BMAL1 showed an important role in fertility, whereas oestradiol and androgens exhibited tissue‐specific effects on clock gene expression. Metabolic disorders were also associated with circadian dysregulation according to studies in shift workers.

Conclusions

Clock genes are associated with various endocrine disorders through complex mechanisms. However, data on humans are scarce. Moreover, clock genes exhibit a tissue‐specific expression representing an additional level of regulation. Their specific role in endocrine disorders and their potential implications remain to be further clarified.  相似文献   
995.
996.
997.

Purpose

The accumulation of advanced glycation end products (AGEs) in local tissue is an important cause of low-grade inflammation and oxidative stress and is linked to late diabetic complications. Physical activity has various beneficial cardiometabolic effects in type 1 diabetes (T1D) and is associated with lower frequency of chronic complications of diabetes, although the specific mechanisms still remain unclear. The present study determines the association between self-reported physical activity and skin autofluorescence (AF), a marker of tissue accumulation of AGEs in adults with T1D.

Methods

We enrolled 119 patients (63 women), aged 34 years (interquartile range [IQR], 26–41 years), with T1D duration of 17 years (IQR, 12–25 years), glycosylated hemoglobin (HbA1c) of 7.9% (IQR, 7.1%–8.9%) referred to an outpatient diabetes clinic. Patients with diabetes duration of <5 years, age >65 years, concomitant diabetic ketoacidosis, and severe complications that restrict physical activity (eg, diabetic foot, diabetic proliferative retinopathy, blindness) were excluded. Physical activity was measured with the short version of the International Physical Activity Questionnaire (IPAQ-SF), and raw scores were then log-transformed because of non-normality. The accumulation of AGEs in the skin was assessed on the basis of skin AF. Correlations between AF and various laboratory and clinical findings were assessed, and multivariate linear regression analysis was used to examine factors that influenced AGEs.

Findings

Skin AF correlated positively with age (Spearman’s coefficient [Rs] = 0.47; P < 0.0001), HbA1c (Rs = 0.30; P = 0.001), waist-to-hip ratio (WHR; Rs = 0.23; P = 0.02), and negatively with logIPAQ-SF (Rs = –0.28; P = 0.002). A stepwise multivariable linear regression analysis indicated age (β = 0.46; P < 0.0001), HbA1c (β = 0.21; P = 0.01), and logIPAQ-SF score (β = –0.17; P = 0.04) as predictors of the skin AF after adjustment for sex and WHR (R2 = 0.36; P < 0.0001).

Implications

Higher physical activity is related to lower accumulation of AGEs in patients with T1D. Our study provides new insight into the beneficial effects of physical activity in T1D according to tissue accumulation of AGEs.  相似文献   
998.

Introduction

The purpose of this review is to present the current and emerging treatment alternatives for Leber’s hereditary optic neuropathy (LHON), emphasizing the most recent use of idebenone and stem cells or gene therapy.

Methods

A comprehensive literature review was performed at the PubMed database regarding the various treatment modalities for LHON.

Results

Treatment modalities for LHON include nutritional supplements, activators of mitochondrial biogenesis, brimonidine, and symptomatic and supportive treatment, but nowadays attention is being paid to idebenone and gene therapy or stem cells.

Conclusion

The treatment of LHON remains challenging, given the nature of the disease and its prognosis.
  相似文献   
999.
Purpose

The aim of this study was to evaluate the utility of added DWI sequences as an adjunct to traditional MR imaging in the evaluation of abnormal placentation in patients with suspicion for placenta accreta spectrum abnormality or morbidly adherent placenta (MAP).

Materials and methods

The study was approved by local ethics committee. The subjects included pregnant women with prenatal MRI performed between July 2013 to July 2015. All imaging was performed on a Philips 1.5T MR scanner using pelvic phased-array coil. Only T2-weighted and diffusion-weighted imaging (DWI) series were compiled for review. Two randomized imaging sets were created: set 1 included T2-weighted series only (T2W); set 2 included T2W with DWI series together (T2W + DWI). Three radiologists, blinded to history and pathology, reviewed the imaging, with 2 weeks of time between the two image sets. Sensitivity, specificity, and overall accuracy for MAP were calculated and compared between T2W only and T2W + DWI reads. Associations between imaging findings and invasion on pathology were tested using the Chi-squared test. Confidence scores, inter-reader agreement, and systematic differences were documented.

Results

A total of 17 pregnant women were included in the study. 8 cases were pathologically diagnosed with MAP. There were no significant differences in the diagnostic accuracy between T2W and T2W + DWI in the diagnosis of MAP in terms of overall accuracy (62.7% for T2W vs. 68.6% for T2W + DWI, p = 0.68), sensitivity (70.8% for T2W vs. 95.8% for T2W + DWI, p = 0.12), and specificity (55.6% for T2W vs. 44.4% for T2W + DWI, p = 0.49). There was no significant difference in the diagnostic confidence between the review of T2W images alone and the T2W + DWI review (mean 7.3 ± 1.8 for T2W vs. 7.5 ± 1.8 for T2W + DWI, p = 0.37).

Conclusion

With the current imaging technique, addition of DWI sequence to the traditional T2W images cannot be shown to significantly increase the accuracy or reader confidence for diagnosis of placenta accreta spectrum abnormality. However, DWI does improve identification of abnormalities in the placental–myometrial interface.

  相似文献   
1000.

Context

This review summarizes the current randomized controlled trials literature on psychological and physical outcomes of psychosocial interventions in pediatric oncology.

Objectives

The objective of this study was to evaluate the effectiveness and impact of psychosocial interventions in children with cancer.

Methods

A search of the literature resulted in a total of 12 randomized clinical trials and these have evaluated psychosocial interventions in children younger than 18 years with current and previous diagnoses of cancer. Outcome measures were both psychological (e.g., symptoms of anxiety, depression, quality of life, and self-esteem) and physical (e.g., cancer symptoms, treatment adherence, and pain). Interventions identified included cognitive behavioral therapy (CBT; n = 4), joint CBT and physical exercise therapy (n = 1), family therapy (n = 2), therapeutic music video (n = 2), self-coping strategies (n = 1), a wish fulfillment intervention (n = 1), and joint family therapy and CBT (n = 1).

Results

Nine studies reported statistically significant improvements on psychological outcomes. These findings suggest that psychosocial interventions are effective at reducing anxiety and depressive symptoms as well as improving quality of life. Additionally, six studies found psychosocial interventions to have a positive impact on physical symptoms and well-being, including a reduction in procedural pain and symptom distress.

Conclusion

These findings suggest that mental health needs in pediatric oncology patients can and should be addressed, potentially which will lead to better mental and physical health outcomes.  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