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   1143篇
  免费   79篇
  国内免费   6篇
耳鼻咽喉   33篇
儿科学   21篇
妇产科学   52篇
基础医学   154篇
口腔科学   47篇
临床医学   109篇
内科学   352篇
皮肤病学   10篇
神经病学   148篇
特种医学   24篇
外科学   144篇
综合类   2篇
一般理论   1篇
预防医学   24篇
眼科学   5篇
药学   52篇
肿瘤学   50篇
  2023年   2篇
  2022年   12篇
  2021年   32篇
  2020年   22篇
  2019年   30篇
  2018年   46篇
  2017年   30篇
  2016年   43篇
  2015年   29篇
  2014年   45篇
  2013年   52篇
  2012年   83篇
  2011年   76篇
  2010年   44篇
  2009年   44篇
  2008年   87篇
  2007年   80篇
  2006年   77篇
  2005年   64篇
  2004年   75篇
  2003年   71篇
  2002年   50篇
  2001年   6篇
  2000年   9篇
  1999年   10篇
  1998年   11篇
  1997年   5篇
  1996年   9篇
  1995年   6篇
  1994年   2篇
  1993年   6篇
  1992年   5篇
  1991年   11篇
  1990年   3篇
  1989年   3篇
  1988年   3篇
  1987年   6篇
  1986年   6篇
  1984年   4篇
  1982年   4篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   2篇
  1973年   5篇
  1972年   1篇
  1970年   1篇
  1969年   1篇
  1968年   3篇
  1966年   1篇
排序方式: 共有1228条查询结果,搜索用时 15 毫秒
11.
Pulmonary hypertension (PH) is usually perceived as a complication of established heart failure (HF) rather than as a predictor of HF or a marker of subclinical HF. PH may develop because of cardiac alterations that result in increased filling pressures after acute myocardial infarction (AMI). We hypothesized that PH might be a useful marker to predict the risk of HF after AMI. We studied 1,054 patients with AMI. Pulmonary artery systolic pressure (PASP) was estimated using echocardiography at the index admission and PH was defined as a PASP >35 mm Hg. The primary end point was readmission for HF at 1 year. PH was present in 471 patients (44.6%) and was strongly associated with age, decreased ejection fraction, advanced diastolic dysfunction, and moderate/severe mitral regurgitation (p <0.0001 for all comparisons). Area under the receiver operating characteristic curve was significantly higher for estimated PASP (0.74 ± 0.02) compared to other echocardiographic parameters (p = 0.02 to 0.0003). After adjustments for clinical and echocardiographic variables in a Cox model, PH was associated with a hazard ratio of 3.10 for HF (95% confidence interval 1.31 to 2.57, p <0.0001). After adding estimated PASP to a model containing clinical and echocardiographic risk factors, net reclassification improvement was 0.21 (95% confidence interval 0.11 to 0.31, p <0.0001). In conclusion, PASP integrates the severity of multiple hemodynamic determinants of increased left atrial pressures that lead to an increase in pulmonary venous pressure. In AMI, PH at the index admission is a useful marker in unmasking latent subclinical HF and predicting the development of overt HF.  相似文献   
12.

Objectives

Attention deficit hyperactivity disorder (ADHD) is a childhood neurological disorder. Studies have shown that children with ADHD are more prone to caries than those without. The study investigated children diagnosed with ADHD, both with and without pharmacological intervention, and the following: DMFT\dmft, plaque index (PI), mutans streptococci (MS) levels, lactobacilli (LB) levels, salivary flow, salivary buffer capacity, oral hygiene, and diet.

Study design

DMFT/dmft index, PI, MS and LB levels, salivary flow, and salivary buffer capacity were examined in three groups of children: ADHD1—diagnosed with ADHD with no pharmacological intervention (N?=?31), ADHD2—treated with medications for ADHD (N?=?30), and a healthy control group (N?=?30). Diet and oral health habits were assessed through questionnaires completed by parents.

Results

There were no differences in the DMFT/dmft index, MS and LB counts, salivary buffer capacity, and parent reported diet and oral health behavior between the three groups. Children with ADHD demonstrated a higher plaque index.

Conclusions

Although children with ADHD did not report different diet and oral health behavior from children without ADHD, this group had significantly higher levels of plaque than the control group, which combined with hyposalivation may be a risk factor for caries at an older age.

Clinical relevance

Medicated and non-medicated ADHD children were similar to control children in their caries rate, MS and LB counts, salivary buffer capacity, and diet and oral health behavior. They differed in the amount of plaque found on their teeth. As a group, ADHD children demonstrated hyposalivation compared with the control.  相似文献   
13.
Technology has much to offer the surgical disciplines. However, teamwork, open communication, and a willingness to adapt and adopt new skills and processes are critical to achieving improved clinical outcomes.  相似文献   
14.
Merozoite surface proteins of the human malaria parasite Plasmodium falciparum are involved in initial contact with target erythrocytes, a process that begins a cascade of events required for successful invasion of these cells. In order to identify complexes that may play a role in invasion we purified detergent-resistant membranes (DRMs), known to be enriched in merozoite surface proteins, and used blue native-polyacrylamide gel electrophoresis (BN-PAGE) to isolate high molecular weight complexes for identification by mass spectrometry. Sixty-two proteins were detected and these mostly belonged to expected DRM proteins classes including GPI-anchored, multi-membrane spanning and rhoptry proteins. Proteins from seven known complexes were identified including MSP-1/7, the low (RAP1/2 and RAP1/3), and high (RhopH1/H2/H3) molecular weight rhoptry complexes, and the invasion motor complex (GAP45/GAP50/myosinA). Remarkably, a large proportion of identified spectra were derived from only 4 proteins: the GPI-anchored proteins MSP-1 and Pf92, the putative GPI-anchored protein Pf113 and RAP-1, the core component of the two RAP complexes. Each of these proteins predominated in high molecular weight species suggesting their aggregation in much larger complexes than anticipated. To demonstrate that the procedure had isolated novel complexes we focussed on MSP-1, which predominated as a distinct species at approximately 500 kDa by BN-PAGE, approximately twice its expected size. Chemical cross-linking supports the existence of a stable MSP-1 oligomer of approximately 500 kDa, probably comprising a highly stable homodimeric species. Our observations also suggests that oligomerization of MSP-1 is likely to occur outside the C-terminal epidermal growth factor (EGF)-like domains. Confirmation of MSP-1 oligomerization, together with the isolation of a number of known complexes by BN-PAGE, makes it highly likely that novel interactions occur amongst members of this proteome.  相似文献   
15.
OBJECTIVE: Aggregation (i.e., meta-ethnography or meta-synthesis) of qualitative studies remains relatively rare and controversial. We have attempted this procedure within an investigation of patient priorities and evaluations of primary care in order to triangulate an instrument development process as well as explore associated dilemmas. METHODS: The procedures included a literature search of qualitative research on patient priorities and evaluations and creation of a framework for quality assessment of retrieved papers. The tool for the evaluation of quality in qualitative studies was piloted, refined, and applied to the retrieved literature. The articles were equally distributed between two teams in random fashion, and inter-rater agreement calculated. Finally, we formulated and applied a strategy for aggregation of data from included papers that allowed comparison to a systematic review of quantitative studies on the topic. RESULTS: Thirty-seven articles met inclusion criteria. Twenty-four of these articles were of sufficient quality to be included in the qualitative aggregation. Inter-rater agreement ranged from 0.22 to 0.77 and 0.38 to 0.60 for pair and assessor comparisons, respectively. The aggregation strategy enabled synthesis within sub-categories of the heterogeneous papers. CONCLUSIONS: We have devised a modestly reliable instrument to assess the quality of qualitative work. The procedure for quality assessment and aggregation appears to be both feasible and potentially useful, though both theoretical and practical problems underline the need for further refinement prior to widespread utilization of this approach. PRACTICE IMPLICATIONS: An instrument to assess the quality of qualitative work within the context of aggregation efforts is described. Calculating inter-rater reliability in this framework can support future quality assessments. A method of breaking a heterogeneous collection of included papers into sub-categories to enable aggregation of qualitative studies is applied and demonstrates its feasibility and potential usefulness.  相似文献   
16.
CpG DNA stimulates autoreactive immature B cells in the bone marrow   总被引:2,自引:0,他引:2  
Polyclonal activation of developing B cells is an injurious process, because most of these cells are nontolerant and express autoreactive receptors. CpG DNA is a polyclonal activator of mature B cells, but its effect on developing B cells is unclear. We tested whether developing, nontolerant B cells are responsive to mitogenic stimulation by CpG DNA and whether such a stimulus can interfere with the establishment of central tolerance. We found that developing B cells express Toll-like receptor 9 and undergo a polyclonal response to CpG DNA stimulation, as revealed by proliferation and differentiation to antibody-producing cells. In vitro and ex vivo experiments revealed that stimulation with CpG DNA protects immature B cells from negative selection imposed by apoptosis and receptor editing and results in the production of autoantibodies. Finally, we found that in vivo administration of CpG DNA activates immature B cells in the bone marrow and suppresses the expression of recombination-activating genes in a mouse model of central tolerance and receptor editing. These results suggest that mitogenic signals provided by CpG DNA stimulate nontolerant immature B cells in the bone marrow and have the potential to interfere with central tolerance.  相似文献   
17.
18.
19.
ObjectiveDespite increased risks of nasolacrimal duct obstruction (NLDO) with age, and the continuous growth of the old population proportion, data on endoscopic dacryocystorhinostomy (eDCR) among the old is lacking. This study aims to evaluate long-term eDCR efficacy and safety in the old and oldest-old population.MethodsA retrospective case-control study of patients aged 80 ≤ (oldest-old) and 65–79 (old) compared with younger controls who underwent eDCR, between 2002 and 2017. Pre-, intra- and postoperative factors were collected using an integrated hospital-community system. Success rates were analyzed and measured at the first visit following surgery (immediate success), and after five years. Demographics, comorbidities, complications rates, and outcomes were compared between the groups.ResultsThe study groups included 52 oldest-old patients (mean age 83.4 ± 3.6), 127 old patients (72.3 ± 4.14) and 142 control patients (57.8 ± 18.0). The immediate and success rates were 94.2%, 93.7% and 90.8% and five-year success rates were 80.0%, 76.6% and 80% among oldest-old, old and controls, respectively. No significant differences in success rates were found, even despite higher comorbidity rates among the study's group (96 and 92.8% vs. 63.2%, among oldest-old, old and controls respectively, p <0.001). Intra- and postoperative complications rates were low in all groups.ConclusionsAmong older population, including oldest-old and old, eDCR safety and long-term outcomes are comparable with younger patients, suggesting that eDCR should be offered to NLDO patients, regardless of age.  相似文献   
20.

Objectives

The aim of the present study was to investigate the distribution of oral cariogenic bacteria among 12-year-old Palestinian children attending schools in East Jerusalem.

Materials and methods

Salivary levels of mutans streptococci (MS) and Lactobacilli (LB) were examined by semi-quantitative commercial kits and then correlated to social–demographic parameters.

Results

Overall, 52.1 % of the examined children presented the highest possible ranking score categories for MS bacteria, with only 5.4 % in the lowest category. Only 12.6 % of the school children presented the highest LB score, while 25 % had the lowest ranking score. Salivary MS levels in children attending private schools were lower than those of children in government schools and United Nations Relief and Works Agency (UNRWA) schools. Conversely, levels of LB were lowest in children attending UNRWA schools compared to government and private schools. Girls had significantly higher amounts of MS and LB than boys (p?=?0.001). Lower MS levels were significantly related to the following socioeconomic variables: higher father’s education level (p?=?0.037), higher mother’s education level (p?=?0.063), mother’s employment status (p?=?0.012), and lower home density (p?=?0.001). For LB, the only significant socioeconomic variable was higher father’s employment level, which was related to lower LB level (p?=?0.025).

Conclusions

Levels of MS and LB were found to be strongly related with socioeconomic status among Palestinian children in East Jerusalem. The relatively high prevalence of cariogenic bacteria suggests that oral care prevention and treatment demands special attention from the health care institutions and authorities.  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