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   700篇
  免费   64篇
  国内免费   2篇
耳鼻咽喉   9篇
儿科学   29篇
妇产科学   27篇
基础医学   109篇
口腔科学   8篇
临床医学   119篇
内科学   134篇
皮肤病学   8篇
神经病学   57篇
特种医学   13篇
外科学   66篇
综合类   6篇
预防医学   73篇
眼科学   5篇
药学   60篇
中国医学   7篇
肿瘤学   36篇
  2023年   13篇
  2022年   30篇
  2021年   41篇
  2020年   20篇
  2019年   36篇
  2018年   44篇
  2017年   29篇
  2016年   28篇
  2015年   22篇
  2014年   34篇
  2013年   46篇
  2012年   68篇
  2011年   63篇
  2010年   29篇
  2009年   27篇
  2008年   53篇
  2007年   29篇
  2006年   42篇
  2005年   22篇
  2004年   23篇
  2003年   27篇
  2002年   20篇
  2001年   2篇
  1999年   1篇
  1998年   1篇
  1997年   5篇
  1996年   1篇
  1995年   2篇
  1994年   2篇
  1992年   2篇
  1988年   1篇
  1985年   1篇
  1983年   1篇
  1979年   1篇
排序方式: 共有766条查询结果,搜索用时 15 毫秒
81.
In present study different protein measurement methods are evaluated on the allergenic extract of Chenopodium album pollen, which was previously prepared in our laboratory and applied in skin prick testing in comparison with a commercial extract. The protein content of similar amounts of these two extracts which had caused similar skin reactions were measured with different protein assays such as protein nitrogen unit, Lowry procedure, ultra-violet absorption, and base catalyzed hydrolysis and ninhydrin (B.H.N.). The latter is recommended by World Health Organization (W.H.O.) in order to determine total protein of standard allergenic extracts. Our study indicated some differences between protein amounts measured by the various procedures. According to W.H.O. reports regarding the advantages of B.H.N. assay, due to good correlation with biological activity of allergenic extracts, we also found that this method can indicate the potency of extracts much more precisely.  相似文献   
82.

Objective

The purpose of this study was to review the literature to determine whether surface electromyography (EMG) is a reliable tool to assess paraspinal muscle fatigue in healthy subjects and in patients with low back pain (LBP).

Methods

A literature search for the period of 2000 to 2012 was performed, using PubMed, ProQuest, Science Direct, EMBASE, OVID, CINAHL, and MEDLINE databases. Electromyography, reliability, median frequency, paraspinal muscle, endurance, low back pain, and muscle fatigue were used as keywords.

Results

The literature search yielded 178 studies using the above keywords. Twelve articles were selected according to the inclusion criteria of the study. In 7 of the 12 studies, the surface EMG was only applied in healthy subjects, and in 5 studies, the reliability of surface EMG was investigated in patients with LBP or a comparison with a control group. In all of these studies, median frequency was shown to be a reliable EMG parameter to assess paraspinal muscles fatigue. There was a wide variation among studies in terms of methodology, surface EMG parameters, electrode location, procedure, and homogeneity of the study population.

Conclusions

The results suggest that there seems to be a convincing body of evidence to support the merit of surface EMG in the assessment of paraspinal muscle fatigue in healthy subject and in patients with LBP.  相似文献   
83.
84.

Background

Haemoglobin screening methods need to be highly sensitive to detect both low and high haemoglobin levels and avoid unnecessary rejection of potential blood donors. The aim of this study was to evaluate the accuracy of measurements by HemoCue in blood donors.

Materials and methods

Three hundred and fourteen randomly selected, prospective blood donors were studied. Single fingerstick blood samples were obtained to determine the donors'' haemoglobin levels by HemoCue, while venous blood samples were drawn for measurement of the haemoglobin level by both HemoCue and an automated haematology analyser as the reference method. The sensitivity, specificity, predictive values and correlation between the reference method and HemoCue were assessed. Cases with a haemoglobin concentration in the range of 12.5–17.9 g/dL were accepted for blood donation.

Results

Analysis of paired results showed that haemoglobin levels measured by HemoCue were higher than those measured by the reference method. There was a significant correlation between the reference method and HemoCue for haemoglobin levels less than 12.5 g/dL. The correlation was less strong for increasing haemoglobin levels. Linear correlation was poor for haemoglobin levels over 18 g/dL. Thirteen percent of donors, who had haemoglobin levels close to the upper limit, were unnecessarily rejected.

Discussion

HemoCue is suitable for screening for anaemia in blood donors. Most donors at Yazd are males and a significant percentage of them have haemoglobin values close to the upper limit for acceptance as a blood donor; since these subjects could be unnecessarily rejected on the basis of HemoCue results and testing with this method is expensive, it is recommended that qualitative methods are used for primary screening and accurate quantitative methods used in clinically suspicious cases or when qualitative methods fail.  相似文献   
85.
Abstract: In this work, the influences of cholecystokinin receptor antagonists L-365,260, MK-329 and proglumide on antinociception induced by baclofen and GABA uptake inhibitor 4, 5, 6, 7–tetrahydroisoxazolo [4, 5-c]pyridin-3-ol (THPO) in the tail flick test has been studied. Baclofen and THPO induced antinociception in the tail flick test. Morphine, and the CCK receptor antagonists, MK-329, L-365,260 and proglumide also induced antinociception. The CCK receptor antagonists potentiated antinociceptive response induced by both baclofen and THPO. It may be concluded that cholecystokinin receptor mechanism(s) may interact with antinociception induced by GABA receptor mechanism(s).  相似文献   
86.
The MTHFR C677T polymorphism is associated with mildly elevated homocysteine levels when folate and/or riboflavin status is low. Furthermore, a mildly elevated homocysteine level is a risk factor for osteoporotic fractures. We studied whether dietary intake of riboflavin and folate modifies the effects of the MTHFR C677T variant on fracture risk in 5,035 men and women from the Rotterdam Study. We found that the MTHFR C677T variant interacts with dietary riboflavin intake to influence fracture risk in women. INTRODUCTION: The MTHFR C677T polymorphism is associated with mildly elevated homocysteine (Hcy) levels in the presence of low folate and/or riboflavin status. A mildly elevated Hcy level was recently identified as a modifiable risk factor for osteoporotic fracture. We studied whether dietary intake of riboflavin and folate modifies the effects of the MTHFR C677T polymorphism on BMD and fracture risk. MATERIALS AND METHODS: We studied 5,035 individuals from the Rotterdam Study, >or=55 yr of age, who had data available on MTHFR, nutrient intake, and fracture risk. We performed analysis on Hcy levels in a total of 666 individuals, whereas BMD data were present for 4,646 individuals (2,692 women). RESULTS: In the total population, neither the MTHFR C677T polymorphism nor low riboflavin intake was associated with fracture risk and BMD. However, in the lowest quartile of riboflavin intake, female 677-T homozygotes had a 1.8 (95% CI: 1.1-2.9, p = 0.01) times higher risk for incident osteoporotic fractures and a 2.6 (95% CI: 1.3-5.1, p = 0.01) times higher risk for fragility fractures compared with the 677-CC genotype (interaction, p = 0.0002). This effect was not seen for baseline BMD in both men and women. No significant influence was found for dietary folate intake on the association between the MTHFR C677T genotype and fracture risk or BMD. In the lowest quartile of dietary riboflavin intake, T-homozygous individuals (men and women combined) had higher (22.5%) Hcy levels compared with C-homozygotes (mean difference = 3.44 microM, p = 0. 01; trend, p = 0.02). CONCLUSIONS: In this cohort of elderly whites, the MTHFR C677T variant interacts with dietary riboflavin intake to influence fracture risk in women.  相似文献   
87.
BACKGROUND: It is commonly believed that weight loss after biliopancreatic diversion/duodenal switch is inversely related to the length of the alimentary limb and the common channel. However, the effect of the biliopancreatic limb length (BPL) on weight loss has received little attention. METHODS: A total of 1001 patients after biliopancreatic diversion/duodenal switch (209 men and 792 women, mean age 42 +/- 10 yr, mean body mass index [BMI] 52 +/- 9 kg/m(2)) were divided into 2 groups according to the ratio of the BPL to the total small bowel length (SBL): a BPL < or =45% of the SBL versus a BPL >45% of the SBL. The nutritional parameters and percentage of excess weight loss were compared between the 2 groups. RESULTS: In patients with a BMI of < or =60 kg/m(2), the percentage of excess weight loss at 1 year postoperatively was 66.8% for those with a BPL < or =45% of the SBL and 69.3% for those with a BPL >45% of the SBL (P = NS). At 2 years, the corresponding percentages were 73.7% and 79.5% (P = NS) and, at 3 years, were 73.4% and 75.2% (P = NS). In patients with a BMI >60 kg/m(2), the corresponding percentages of excess weight loss was 56.8% versus 61.4% (P = .07) at 1 year, 62.2% versus 77.5% (P = .04) at 2 years, and 59.8% versus 77.5% at 3 years (P = .05). CONCLUSION: The results of our study have shown that amount of weight lost after biliopancreatic diversion/duodenal switch is directly related to the proportion of small bowel bypassed in patients with a BMI >60 kg/m(2). Also, the effect increased with the duration of follow-up. In less heavy patients, the BPL/SBL ratio had a minimal effect on long-term weight loss and a more pronounced effect on nutritional parameters.  相似文献   
88.
89.
Cyclooxygenase (Cox-2) is implicated in the pathogenesis of many cancers including esophageal adenocarcinoma (EAC), whereas the role of the isoform Cox-1 in carcinogenesis is not well understood. To further elucidate the role of these factors in the development of EAC, we measured the gene expressions (mRNA levels) of Cox-2 and Cox-1 by real-time quantitative polymerase chain reaction (QRT-PCR) in tissues from normal esophagus with and without erosive gastroesophageal reflux disease (GERD), Barrett's esophagus (BE), dysplasia, adenocarcinoma, and in healthy gastric antrum. All tissues were purified by laser capture microdissection from endoscopic or surgical resection specimens. Median Cox-2 gene expression did not differ significantly among the esophageal control groups but was elevated 5-fold in BE, 8-fold in dysplasia and 16-fold in EAC compared to normal esophageal controls with no erosive GERD. Erosive GERD tissue had slightly higher median Cox-2 expression but Cox-2 expression in normal antrum was much higher than that in a normal esophagus, close to that of dysplasia. In contrast to that of Cox-2, Cox-1 expression was significantly decreased in all neoplastic tissues compared to normal controls. Cox-1 and Cox-2 expression varied over a wide range in the neoplastic tissues but over a relatively narrow range in the esophageal normal tissues. The occurrence of substantial alterations in Cox-1 and Cox-2 expression at the BE stage indicates that these are early events in the development of EAC. These results confirm the important role of Cox-2 amplification in the pathogenesis of esophageal adenocarcinoma, but the unexpected down-regulation of Cox-1 raises questions about its role in carcinogenesis.  相似文献   
90.
We present the case of a trauma patient whose persistently abnormal chest radiography led to exploratory bronchoscopy. After the discovery of a foreign body in the right lower lobe bronchus, an attempted retrieval resulted in accidental perforation of a cocaine bag and release of the drug, which may have been the cause of the patient's subsequent pneumonitis.  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