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   613篇
  免费   55篇
  国内免费   1篇
耳鼻咽喉   4篇
儿科学   16篇
妇产科学   12篇
基础医学   50篇
口腔科学   30篇
临床医学   37篇
内科学   113篇
皮肤病学   10篇
神经病学   92篇
特种医学   20篇
外科学   108篇
综合类   17篇
预防医学   31篇
眼科学   22篇
药学   43篇
中国医学   3篇
肿瘤学   61篇
  2023年   5篇
  2022年   15篇
  2021年   27篇
  2020年   14篇
  2019年   33篇
  2018年   38篇
  2017年   14篇
  2016年   33篇
  2015年   30篇
  2014年   39篇
  2013年   31篇
  2012年   70篇
  2011年   70篇
  2010年   41篇
  2009年   23篇
  2008年   43篇
  2007年   35篇
  2006年   24篇
  2005年   21篇
  2004年   16篇
  2003年   19篇
  2002年   16篇
  2001年   4篇
  1999年   1篇
  1998年   2篇
  1997年   1篇
  1989年   1篇
  1987年   1篇
  1981年   1篇
  1973年   1篇
排序方式: 共有669条查询结果,搜索用时 15 毫秒
51.
PURPOSE: To determine how sociodemographic characteristics influence both access to transplantation and organ donation. METHODS: For all transplants in the United States from 1996 to 2001, donor-recipient pairs were categorized as white-white, white-black, black-white, or black-black. The difference in the percentage of white-black versus black-white pairs was calculated as a measure of the net transfer of organs from one racial group to another. A similar approach was used to examine the net transfer of organs across other sociodemographic categories. RESULTS: Among cadaveric renal transplants, 66% of donor-recipient pairs were white-white, 23% were white-black, 5% were black-white, and 6% were black-black. Thus, there was an 18% net transfer of organs from white donors to black recipients (23% minus 5%). Among living donor transplants involving spouses, there was a 36% net transfer from wives to husbands. Among all cadaveric transplants, there was a 36% to 68% net transfer from younger donors to older recipients. Among cadaveric nonrenal transplants, there was a 7% to 18% net transfer from lower-income donors to higher-income recipients. CONCLUSION: The sociodemographic characteristics of persons who donate organs and those who benefit from organ transplantation differ markedly. Efforts to improve access and increase donation should address these differences.  相似文献   
52.
53.
OBJECTIVES: Malnutrition is common in hospitalized older people, and some have advocated routine nutritional screening. Serum albumin and clinically based measures such as the Subjective Global Assessment (SGA) are two potential methods of assessing nutritional status in hospitalized older people. Although both measures are strongly associated with prognosis, it is not clear whether they measure similar or different clinical constructs. Our goal was to assess the degree of clinical concordance between these measures. DESIGN: Cross-sectional study. SETTING: The inpatient medical service of a university teaching hospital. PARTICIPANTS: Three hundred eleven older (aged > or =70) patients. MEASUREMENTS: We independently measured serum albumin and performed the SGA on 311 older medical patients (aged > or =70) shortly after hospital admission. The SGA classified patients as well nourished, moderately malnourished (generally 5% weight loss with mild examination findings), or severely malnourished (generally >10% weight loss with marked findings) based on findings from a directed history and examination. We compared the distribution of clinical rating in patients with differing albumin levels and examined diagnostic test characteristics of albumin as a predictor of malnutrition as diagnosed on clinical examination. RESULTS: The mean age of subjects was 79.9; 64% were women, 42% were African American. Discordance between albumin and the SGA was common. For example, 38% of patients with albumin levels of 4.0 g/dL or higher were at least moderately malnourished on the SGA, whereas 28% of patients with albumin levels lower than 3.0 g/dL were rated as well nourished. No choice of albumin level was associated with simultaneously acceptable sensitivity and specificity as a predictor of SGA ratings. The area under the receiver operating characteristic curve for albumin level as a predictor of SGA rating was 0.58, suggesting that the ability of either measure to predict the other measure is only marginally better than chance. CONCLUSIONS: Albumin levels and clinical assessments, two possible measures of nutritional status in hospitalized older people, are often discordant. To some extent, this reflects limitations in both measures as markers of nutritional status. However, it also demonstrates that, in this population, albumin and clinical assessments of nutritional status reflect fundamentally different clinical processes.  相似文献   
54.
We evaluate the suggestion that high-sensitivity C-reactive protein testing be used for risk assessment in the primary prevention of cardiovascular disease, using the criteria proposed by the Guide to Clinical Preventive Services developed by the US Preventive Services Task Force. We conclude that at present, none of the 3 major criteria--accuracy, reliability, and likelihood of beneficial intervention--are satisfied.  相似文献   
55.
The aim of this article is to evaluate and assess the impact of various factors on quality of life (QOL) in adult patients with primary brain tumors seen consecutively in routine neurooncology practice. Two hundred and fifty-seven adult patients, after undergoing surgical intervention and histologically proven primary brain neoplasms were registered in the NeuroOncology Clinic at our centre during 1 full calendar year. The study included detailed neurological assessment, evaluation of QOL using EORTC questionnaire (QLQ-30) and specific Brain Cancer module (BN 20). In the present analysis, QOL scores before starting adjuvant treatment were measured and impact of patient and tumor related factors were analyzed. Baseline global QOL data of all patients (available in 243) was relatively low including in all histological tumor types. Physical function, role function, emotion function, cognitive and social function scores were 80, 78, 65.7, 70 and 70.5 (higher values better), respectively. Domains of future uncertainty, visual disorder, motor deficit, communication deficit, headache, seizures and drowsiness scores were 19.6, 18.2, 28.5, 30.7, 21, 31.8 and 16 (lower values better), respectively. Elderly patients had poorer global score (21 points difference; p = 0.161). Patients with lower performance status (KPS < 70) had a lower global QOL (KPS ≥ 80 vs. ≤ 70; 37 vs. 67; p = 0.001) including in all histological types of high-grade gliomas (HGG) (p = 0.005), low-grade gliomas (LGG) (p = 0.04) and benign tumors (p = <0.001). Illiterate patients had lower QOL score (p = 0.005). Tumor type is an important patient related factor that influences baseline global scores (LGG vs. HGG 62 and 52; p = 0.015). Economic status significantly influence QOL scores in HGG (p = 0.052). Type of surgery (biopsy/complete excision) (p = 0.284) and site of tumor (p = 0.309) did not show any impact on QOL score. Patients with primary brain tumours before starting adjuvant therapy have relatively low baseline quality of life scores, especially in lower economic and literacy strata. Patients with malignant tumors and poor performance status had significantly lower QOL scores even before starting adjuvant treatment.  相似文献   
56.
57.
In 150 consecutive cases of simple partial epilepsy significant CT abnormalities were found in 68%. The commonest lesion noted was a hypodense lesion on unenhanced scan, with a ring or disc-like enhancement on contrast scan, and surrounding hypodensity. This lesion was seen in 39 cases and was more common in patients below the age of 15 years and in those with shorter duration of fits (less than 6 months). Nineteen of these cases had focal signs, 16 showed focal slow activity on EEG and 17/39 had neither signs nor focal slowing on EEG. Ten cases with a ring or disc enhancing lesion had evidence of tuberculosis elsewhere in the body, three more had a past history of tuberculosis and four others had a history of close contact with a case of tuberculosis. After 3 months of antitubercular treatment, 23 out of 25 patients who were rescanned showed clearing of the lesion. The two who did not were operated upon, and the lesion was shown histologically to be a tuberculoma. Ten other cases have done well, but have not been rescanned. Only one case was not treated with antitubercular therapy. She developed fits, altered consciousness, and meningitis and recovered from this serious illness after starting antitubercular therapy. Though not histologically verified, it seems justified to conclude that in India a ring or disc enhancing lesion is the commonest accompaniment of focal epilepsy, and that at least one third (and probably more) of these lesions are tuberculomas.  相似文献   
58.
Retinoid signaling regulates primitive (yolk sac) hematopoiesis   总被引:3,自引:0,他引:3       下载免费PDF全文
Ghatpande S  Ghatpande A  Sher J  Zile MH  Evans T 《Blood》2002,99(7):2379-2386
It is known from nutritional studies that vitamin A is an important factor for normal hematopoiesis, though it has been difficult to define its precise role. The vitamin A-deficient (VAD) quail embryo provides an effective ligand "knockout" model for investigating the function of retinoids during development. The VAD embryo develops with a significant reduction in erythroid cells, which has not been noted previously. Activation of the primitive erythroid program and early expression of the erythroid marker GATA-1 occurs, though GATA-1 levels eventually decline, consistent with the erythropoietic and hemoglobin deficits. However, from its early stages, the GATA-2 gene fails to be expressed normally in VAD embryos. The bone morphogenetic protein (BMP)-signaling pathway regulates GATA-2, and BMP4 expression becomes reduced in the caudal embryonic region of VAD embryos. Adding BMP4 to cultured VAD-derived explants rescues the production of erythroid cells, whereas normal embryos cultured in the presence of the BMP antagonist noggin are defective in primitive hematopoiesis. We find that cell clusters of primitive blood islands undergo an inappropriate program of apoptosis in the VAD embryo, which can explain the deficit in differentiated primitive blood cells. We propose that vitamin A-derived retinoids are required for normal yolk sac hematopoiesis and that an embryonic retinoid-BMP-GATA-2 signaling pathway controls progenitor cell survival relevant to primitive hematopoiesis.  相似文献   
59.
Background: Event Related Potential (ERP) studies have highlighted some measures, notably P3 amplitude, that are associated with both state and trait deficits in alcoholism, while studies examining N400 amplitude in alcoholism are few. The present study aims to examine differences in the N400 component, an electrophysiological correlate of semantic priming, in event‐related potentials from a lexical decision task in 87 alcohol dependent subjects and 57 community controls. Methods: Each subject was presented with 300 stimuli sequentially in a quasi‐randomized design, where 150 stimuli were words and 150 were non‐words. The subjects made a lexical decision indicating the word/non‐word status with a button press. Among the words, 50 words (primed) were always preceded by their antonyms (prime, n = 50), whereas the remaining 50 words were unrelated. N400 amplitude and latency measures were compiled from ERPs to the primed and unprimed words. Corresponding reaction time (RT) and response characteristics were also analyzed. Results: Control subjects revealed a significant attenuation of the N400 response to the primed word when compared to the unprimed word. Significantly less attenuation was observed in alcohol dependent subjects. No significant group differences were seen for latency and behavioral measures. All subjects had slower RT for unprimed words compared to primed words; however significantly less RT savings between the unprimed and primed condition was noted for alcoholics. Conclusions: These results suggest a reduced flexibility in the cognitive networks and a lack of resource optimization in alcoholics. The reduced attenuation of N400 during the primed condition in the alcohol dependent subjects may reflect an inability to engage similar neuronal substrates associated with semantic relatedness as seen in the controls. As diminished N400 attenuation during priming is observed in both alcoholics and high risk subjects, it may be a marker of risk and a good endophenotype for alcoholism.  相似文献   
60.
Ozone (O?), a commonly encountered environmental pollutant, has been shown to induce pulmonary fibrosis in different animal models; the underlying mechanism, however, remains elusive. To investigate the molecular mechanism underlying O?-induced pulmonary fibrosis, 6- to 8-week-old C57BL/6 male mice were exposed to a cyclic O? exposure protocol consisting of 2 days of filtered air and 5 days of O? exposure (0.5 ppm, 8 h/day) for 5 and 10 cycles with or without intraperitoneal injection of IN-1233, a specific inhibitor of the type 1 receptor of transforming growth factor beta (TGF-β), the most potent profibrogenic cytokine. The results showed that O? exposure for 5 or 10 cycles increased the TGF-β protein level in the epithelial lining fluid (ELF), associated with an increase in the expression of plasminogen activator inhibitor 1 (PAI-1), a TGF-β-responsive gene that plays a critical role in the development of fibrosis under various pathological conditions. Cyclic O? exposure also increased the deposition of collagens and alpha smooth muscle actin (α-SMA) in airway walls. However, these fibrotic changes were not overt until after 10 cycles of O? exposure. Importantly, blockage of the TGF-β signaling pathway with IN-1233 suppressed O?-induced Smad2/3 phosphorylation, PAI-1 expression, as well as collagens and α-SMA deposition in the lung. Our data demonstrate for the first time that O? exposure increases TGF-β expression and activates TGF-β signaling pathways, which mediates O?-induced lung fibrotic responses in vivo.  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