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   2314篇
  免费   173篇
  国内免费   47篇
耳鼻咽喉   11篇
儿科学   94篇
妇产科学   45篇
基础医学   353篇
口腔科学   55篇
临床医学   199篇
内科学   637篇
皮肤病学   47篇
神经病学   152篇
特种医学   162篇
外科学   289篇
综合类   15篇
预防医学   137篇
眼科学   31篇
药学   138篇
  1篇
中国医学   2篇
肿瘤学   166篇
  2023年   15篇
  2022年   13篇
  2021年   49篇
  2020年   24篇
  2019年   43篇
  2018年   75篇
  2017年   52篇
  2016年   58篇
  2015年   61篇
  2014年   75篇
  2013年   101篇
  2012年   129篇
  2011年   128篇
  2010年   83篇
  2009年   83篇
  2008年   118篇
  2007年   132篇
  2006年   94篇
  2005年   78篇
  2004年   68篇
  2003年   72篇
  2002年   77篇
  2001年   54篇
  2000年   66篇
  1999年   49篇
  1998年   60篇
  1997年   68篇
  1996年   65篇
  1995年   53篇
  1994年   40篇
  1993年   50篇
  1992年   32篇
  1991年   37篇
  1990年   24篇
  1989年   29篇
  1988年   43篇
  1987年   33篇
  1986年   32篇
  1985年   26篇
  1984年   15篇
  1983年   16篇
  1982年   9篇
  1981年   13篇
  1980年   13篇
  1978年   8篇
  1977年   12篇
  1976年   7篇
  1975年   11篇
  1974年   5篇
  1969年   5篇
排序方式: 共有2534条查询结果,搜索用时 31 毫秒
81.

Objectives

This study sought to investigate the incidence, associated findings, and natural history of effusive-constrictive pericarditis (ECP) after pericardiocentesis.

Background

ECP is characterized by the coexistence of tense pericardial effusion and constriction of the heart by the visceral pericardium. Echocardiography is currently the main diagnostic tool in the assessment of pericardial disease, but limited data have been published on the incidence and prognosis of ECP diagnosed by echo-Doppler.

Methods

A total of 205 consecutive patients undergoing pericardiocentesis at Mayo Clinic, Rochester, Minnesota, were divided into 2 groups (ECP and non-ECP) based on the presence or absence of post-centesis echocardiographic findings of constrictive pericarditis. Clinical, laboratory, and imaging characteristics were compared.

Results

ECP was subsequently diagnosed in 33 patients (16%) after pericardiocentesis. Overt clinical cardiac tamponade was present in 52% of ECP patients and 36% of non-ECP patients (p = 0.08). Post-procedure hemopericardium was more frequent in the ECP group (33% vs. 13%; p = 0.003), and a higher percentage of neutrophils and lower percentage of monocytes were noted on pericardial fluid analysis in those patients. Clinical and laboratory findings were otherwise similar. Baseline early diastolic mitral septal annular velocity was significantly higher in the ECP group. Before pericardiocentesis, respiratory variation of mitral inflow velocity, expiratory diastolic flow reversal of hepatic vein, and respirophasic septal shift were significantly more frequent in the ECP group. Fibrinous or loculated effusions were also more frequently observed in the ECP group. Four deaths occurred in the ECP group; all 4 patients had known malignancies. During median follow-up of 3.8 years (interquartile range: 0.5 to 8.3 years), only 2 patients required pericardiectomy for persistent constrictive features and symptoms.

Conclusions

In a large cohort of unselected patients undergoing pericardiocentesis, 16% were found to have ECP. Pre-centesis echocardiographic findings might identify such patients. Long-term prognosis in those patients remains good, and pericardiectomy was rarely required.  相似文献   
82.
Study of GH sensitivity in chilean patients with idiopathic short stature   总被引:2,自引:0,他引:2  
We hypothesized that some children with idiopathic short stature in Chile might bear heterozygous mutations of the GH receptor. We selected 26 patients (3 females, 23 males) from 112 patients who consulted for idiopathic short stature at the University of Chile. Their chronological age was 8.3 +/- 1.9, and bone age was 6.1 +/- 1.0 yr. Their height was -3.0 +/- 0.7 SDS; IGF-I, -1.2 +/- 1.1 SD; IGF binding protein 3, -0.7 +/- 2.0 SDS; and GH binding protein, 0.4 +/- 0.8 SDS. Patients were admitted, and blood samples were obtained every 20 min to determine GH concentrations overnight. Coding sequences and intron-exon boundaries of exons 2-10 of GH receptor gene were amplified by PCR and subsequently analyzed through single-strand conformational analysis. Mean serum GH concentration, over 12-h, was 0.20 +/- 0.08 nM; pulse amplitude, 0.40 +/- 0.15 nM; number of peaks, 5.8 +/-1.5 peaks/12 h; peak value of GH during the 12-h sampling, 1.03 +/- 0.53 nM; and area under the curve, 151.4 +/- 56.1 nM/12 h. There were positive correlations between mean GH vs. area under the curve (P < 0.001) and GH peak (P < 0.01). The single-strand conformational analysis of the GH receptor gene showed abnormal migration for exon 6 in 9 patients and for exon 10 in 9 patients, which (by sequence analysis) corresponded to 2 polymorphisms of the GH receptor gene: an A-to-G transition in third position of codon 168 in exon 6 and a C-to-A transversion in the first position of codon 526 in exon 10. We further sequenced all coding exons and intron-exon boundaries in the most affected patients (nos. 6, 9, 11, 14, 15, 16, and 23). This analysis revealed a C-to-T transition in codon 161 of exon 6 in patient 23, which results in an amino acid change (Arg to Cys) in an heterozygous form in the patient and his father. In conclusion, the results of our study suggest that, in Chilean patients with idiopathic short stature, GH receptor gene mutations are uncommon, although we cannot exclude mutations that were missed by single-strand conformational analysis or mutations within introns or in the promoter regions of the GH receptor gene.  相似文献   
83.
Major histocompatibility complex class II (MHC‐II) molecules bind to and display antigenic peptides on the surface of antigen‐presenting cells (APCs). In the absence of infection, MHC‐II molecules on APCs present self‐peptides and interact with CD4+ T cells to maintain tolerance and homeostasis. In the thymus, self‐peptides bind to MHC‐II molecules expressed by defined populations of APCs specialised for the different steps of T‐cell selection. Cortical epithelial cells present peptides for positive selection, whereas medullary epithelial cells and dendritic cells are responsible for peptide presentation for negative selection. However, few data are available on the peptides presented by MHC molecules in the thymus. Here, we apply mass spectrometry to analyse and identify MHC‐II‐associated peptides from five fresh human thymus samples. The data show a diverse self‐peptide repertoire, mostly consisting of predicted MHC‐II high binders. Despite technical limitations preventing single cell population analyses of peptides, these data constitute the first direct assessment of the HLA‐II‐bound peptidome and provide insight into how this peptidome is generated and how it drives T‐cell repertoire formation.  相似文献   
84.
BALB/c mice with pulmonary tuberculosis (TB) develop a T helper cell type 1 that temporarily controls bacterial growth. Bacterial proliferation increases, accompanied by decreasing expression of interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α and inducible nitric oxide synthase (iNOS). Activation of dendritic cells (DCs) is delayed. Intratracheal administration of only one dose of recombinant adenoviruses encoding granulocyte–macrophage colony‐stimulating factor (AdGM‐CSF) 1 day before Mycobacterium tuberculosis (Mtb) infection produced a significant decrease of pulmonary bacterial loads, higher activated DCs and increased expression of TNF‐α, IFN‐γ and iNOS. When AdGM‐CSF was given in female mice B6D2F1 (C57BL/6J X DBA/2J) infected with a low Mtb dose to induce chronic infection similar to latent infection and corticosterone was used to induce reactivation, a very low bacilli burden in lungs was detected, and the same effect was observed in healthy mice co‐housed with mice infected with mild and highly virulent bacteria in a model of transmissibility. Thus, GM‐CSF is a significant cytokine in the immune protection against Mtb and gene therapy with AdGM‐CSF increased protective immunity when administered in a single dose 1 day before Mtb infection in a model of progressive disease, and when used to prevent reactivation of latent infection or transmission.  相似文献   
85.
Manometry of the alimentary tract is a valuable and widely used means to evaluate and diagnose the function of the alimentary tract. However, the measurement can be inconvenient due to the invasive method used, and the many factors affecting results. Research on colonic pressure data is even more insufficient. This paper deals with colonic pressure data via an improved method ensuring that pressure data of the whole colon is available. The data is analysed based on the learning vector quantization (LVQ) method. Testing results show that this method distinguishes the normal data and the abnormal data, consistently with the original diagnoses. This method can serve as an assistant diagnosis of colonic motility and contributes to further research on colonic motility based on pressure data.  相似文献   
86.
Background and aimsWe aimed to analyze the relationship between the initial chest X-ray findings in patients with severe acute respiratory syndrome due to infection with SARS-CoV-2 and eventual clinical worsening and to compare three systems of quantifying these findings.Material and methodsThis retrospective study reviewed the clinical and radiological evolution of 265 adult patients with COVID-19 attended at our center between March 2020 and April 2020. We recorded data related to patients’ comorbidities, hospital stay, and clinical worsening (admission to the ICU, intubation, and death). We used three scoring systems taking into consideration 6 or 8 lung fields (designated 6 A, 6 B, and 8) to quantify lung involvement in each patient's initial abnormal chest X-ray and to classify its severity as mild, moderate, or severe, and we compared these three systems. We also recorded the presence of alveolar opacities and linear opacities (fundamentally linear atelectasis) in the first chest X-ray with pathologic findings.ResultsIn the χ2 analysis, moderate or severe involvement in the three classification systems correlated with hospital admission (p = 0.009 in 6 A, p = 0.001 in 6 B, and p = 0.001 in 8) and with death (p = 0.02 in 6 A, p = 0.01 in 6 B, and p = 0.006 in 8). In the regression analysis, the most significant associations were 6 B with alveolar involvement (OR 2.3; 95%CI 1.1.–4.7; p = 0.025;) and 8 with alveolar involvement (OR 2.07; 95% CI 1.01.–4.25; p = 0.046). No differences were observed in the ability of the three systems to predict clinical worsening by classifications of involvement in chest X-rays as moderate or severe.ConclusionModerate/severe extension in the three chest X-ray scoring systems evaluating the extent of involvement over 6 or 8 lung fields and the finding of alveolar opacities in the first abnormal X-ray correlated with mortality and the rate of hospitalization in the patients studied. No significant difference was found in the predictive ability of the three classification systems proposed.  相似文献   
87.

Background

Mexican-American women are disproportionately vulnerable to cardio-metabolic dysfunction and related health conditions such as cardiovascular disease and diabetes. Research shows that low socioeconomic status contributes to this populations excess vulnerability to cardio-metabolic dysfunction, but little is known about the contribution of cultural factors to these associations.

Purpose

The current study explored the association between fatalism and cardio-metabolic dysfunction in a randomly selected community cohort of middle-aged Mexican–American women and examined whether fatalism could be conceptualized as a pathway linking socioeconomic status to cardio-metabolic dysfunction in this population.

Method

Participants included 300 women (ages 40–65), recruited from San Diego communities located near the Mexican border, who completed a self-administered survey battery and underwent a fasting clinical exam between the years 2006 and 2009.

Results

Linear regression analyses and mediation analyses utilizing bootstrapping procedures were performed to test study hypotheses. After controlling for age, menopausal status, and acculturation level, fatalism was associated with cardio-metabolic dysfunction. Although slightly attenuated, this relationship persisted after accounting for socioeconomic status. In addition, individuals of low socioeconomic status displayed more fatalistic beliefs and higher cardio-metabolic dysfunction after accounting for relevant covariates. Finally, the indirect effect of socioeconomic status on cardio-metabolic dysfunction via fatalism reached statistical significance.

Conclusions

Fatalism may be an important independent risk factor for cardio-metabolic dysfunction in Mexican–American women as well as a mechanism linking socioeconomic status to cardio-metabolic health.  相似文献   
88.
89.
90.
We reviewed systematically sugammadex vs neostigmine for reversing neuromuscular blockade. We included 17 randomised controlled trials with 1553 participants. Sugammadex reduced all signs of residual postoperative paralysis, relative risk (95% CI) 0.46 (0.29–0.71), p = 0.0004 and minor respiratory events, relative risk (95% CI) 0.51 (0.32–0.80), p = 0.0034. There was no difference in critical respiratory events, relative risk (95% CI) 0.13 (0.02–1.06), p = 0.06. Sugammadex reduced drug‐related side‐effects, relative risk (95% CI) 0.72 (0.54–0.95), p = 0.02. There was no difference in the rate of postoperative nausea or the rate of postoperative vomiting, relative risk (95% CI) 0.94 (0.79–1.13), p = 0.53, and 0.87 (0.65–1.17), p = 0.36 respectively.  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