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   823篇
  免费   42篇
  国内免费   5篇
耳鼻咽喉   17篇
儿科学   15篇
妇产科学   51篇
基础医学   88篇
口腔科学   12篇
临床医学   89篇
内科学   221篇
皮肤病学   14篇
神经病学   72篇
特种医学   19篇
外科学   88篇
综合类   4篇
一般理论   1篇
预防医学   68篇
眼科学   18篇
药学   37篇
肿瘤学   56篇
  2024年   1篇
  2023年   6篇
  2022年   14篇
  2021年   31篇
  2020年   13篇
  2019年   30篇
  2018年   41篇
  2017年   24篇
  2016年   24篇
  2015年   27篇
  2014年   37篇
  2013年   44篇
  2012年   66篇
  2011年   77篇
  2010年   36篇
  2009年   42篇
  2008年   53篇
  2007年   54篇
  2006年   60篇
  2005年   42篇
  2004年   30篇
  2003年   34篇
  2002年   23篇
  2001年   6篇
  2000年   6篇
  1999年   7篇
  1998年   5篇
  1997年   4篇
  1996年   2篇
  1995年   1篇
  1993年   2篇
  1992年   4篇
  1991年   2篇
  1990年   2篇
  1989年   2篇
  1988年   3篇
  1987年   4篇
  1985年   3篇
  1984年   3篇
  1978年   1篇
  1976年   1篇
  1970年   3篇
排序方式: 共有870条查询结果,搜索用时 31 毫秒
771.
772.
This study evaluates the occurrence of bacteriophages carrying antibiotic resistance genes in animal environments. bla(TEM), bla(CTX-M) (clusters 1 and 9), and mecA were quantified by quantitative PCR in 71 phage DNA samples from pigs, poultry, and cattle fecal wastes. Densities of 3 to 4 log(10) gene copies (GC) of bla(TEM), 2 to 3 log(10) GC of bla(CTX-M), and 1 to 3 log(10) GC of mecA per milliliter or gram of sample were detected, suggesting that bacteriophages can be environmental vectors for the horizontal transfer of antibiotic resistance genes.  相似文献   
773.
The serotonin transporter is an important regulator of serotonergic signaling. In order to analyze where the Drosophila melanogaster ortholog of the mammalian serotonin transporter (dSERT) is expressed in the nervous system, a dSERT antibody serum was used. Ectopic expression studies and loss of function analysis revealed that the dSERT antibody serum specifically recognizes dSERT. It was shown that in the embryonic nervous system dSERT is expressed in a subset of Engrailed-positive neurons. In the larval brain, dSERT is exclusively expressed in serotonergic neurons, all of which express dSERT. dSERT-positive neurons surround almost all brain neuropiles. In the mushroom body of the adult brain, extrinsic serotonergic neurons expressing dSERT engulf the mushroom body lobes. These neurons show regional differences in dSERT and serotonin expression. At the presynaptic terminals, serotonin release is sterically linked to serotonin reuptake. In contrast to this, there are other areas in serotonergic neurons where dSERT expression and/or function are uncoupled from synaptic neurotransmitter recycling and serotonin release. The localization pattern of dSERT can be employed to further understanding and analysis of serotonergic networks.  相似文献   
774.
BackgroundThe recommendation of screening with ankle brachial index (ABI) in asymptomatic individuals is controversial. The aims of the present study were to develop and validate a pre-screening test to select candidates for ABI measurement in the Spanish population 50–79 years old, and to compare its predictive capacity to current Inter-Society Consensus (ISC) screening criteria.Methods and resultsTwo population-based cross-sectional studies were used to develop (n = 4046) and validate (n = 3285) a regression model to predict ABI < 0.9. The validation dataset was also used to compare the model's predictive capacity to that of ISC screening criteria.The best model to predict ABI < 0.9 included age, sex, smoking, pulse pressure and diabetes. Assessment of discrimination and calibration in the validation dataset demonstrated a good fit (AUC: 0.76 [95% CI 0.73–0.79] and Hosmer–Lemeshow test: χ2: 10.73 (df = 6), p-value = 0.097).Predictions (probability cut-off value of 4.1) presented better specificity and positive likelihood ratio than the ABI screening criteria of the ISC guidelines, and similar sensitivity. This resulted in fewer patients screened per diagnosis of ABI < 0.9 (10.6 vs. 8.75) and a lower proportion of the population aged 50–79 years candidate to ABI screening (63.3% vs. 55.0%).ConclusionThis model provides accurate ABI < 0.9 risk estimates for ages 50–79, with a better predictive capacity than that of ISC criteria. Its use could reduce possible harms and unnecessary work-ups of ABI screening as a risk stratification strategy in primary prevention of peripheral vascular disease.  相似文献   
775.
776.
777.
778.
The obesity paradox in heart failure (HF) is criticized because of the limitations of body mass index (BMI) in correctly characterizing overweight and obese patients, necessitating a better evaluation of nutritional status. The aim of this study was to assess nutritional status, BMI, and significance in terms of HF survival. Anthropometry and biochemical nutritional markers were assessed in 55 HF patients. Undernourishment was defined as the presence of ≥2 of the following indexes below the normal range: triceps skinfold, subscapular skinfold, arm muscle circumference, albumin, and total lymphocyte count. Patients were also stratified by BMI and followed for a median of 26.7 months. Across BMI strata, no patient was underweight, 31% were normal weight, 42% were overweight, and 27% were obese. Undernourishment was present in 53% of normal-weight patients, 22% of overweight patients, and none of the obese patients (p = 0.001). Undernourished patients had significantly higher mortality (p = 0.009) compared to well-nourished patients. In multivariate analysis, only undernutrition (hazard ratio 3.149, 95% confidence interval 1.367 to 7.253), New York Heart Association functional class (hazard ratio 3.374, 95% confidence interval 1.486 to 7.659), and age (hazard ratio 1.115, 95% confidence interval 1.045 to 1.189) remained in the model. Among nutritional indicators, subscapular skinfold was the best predictor of mortality; patients with subscapular skinfold in the fifth percentile had higher mortality (p = 0.0001). In conclusion, BMI does not indicate true nutritional status in HF. Classifying patients as well nourished or undernourished may improve risk stratification.  相似文献   
779.
780.
Non-syndromic X-linked deafness is highly heterogeneous. At least five different clinical forms have been described, but only two loci have been mapped. Here we report a Spanish family affected by a previously undescribed X-linked form of hearing impairment. Deafness is non- syndromic, sensorineural, and progressive. In affected males, the auditory impairment is first detected at school age, affecting mainly the high frequencies. Later it evolves to become severe to profound, involving all frequencies for adulthood. Carrier females manifest a moderate hearing impairment in the high frequencies, with the onset delayed to the fourth decade of life. Deafness was assumed to be X- linked dominant, with incomplete penetrance and variable expressivity in carrier females. The family was genotyped for a set of microsatellite markers evenly spaced at intervals of about 10 cM. We found evidence of linkage to markers in the Xp22 region (maximum lod score of 5.30 at theta = 0.000 for DXS8036 and for DXS8022). The position of the novel deafness locus (DFN6) was refined by haplotype analysis. Mapping of the breakpoints in two critical recombinants allowed us to define an interval for DFN6, delimited by DXS7108 on the distal side and by DXS7105 on the proximal side, and spanning a genetic distance of about 15 cM.   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