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   767篇
  免费   38篇
  国内免费   7篇
耳鼻咽喉   4篇
儿科学   4篇
妇产科学   9篇
基础医学   131篇
口腔科学   29篇
临床医学   61篇
内科学   165篇
皮肤病学   12篇
神经病学   44篇
特种医学   13篇
外科学   174篇
综合类   6篇
预防医学   30篇
眼科学   26篇
药学   68篇
中国医学   2篇
肿瘤学   34篇
  2023年   3篇
  2022年   16篇
  2021年   33篇
  2020年   11篇
  2019年   28篇
  2018年   18篇
  2017年   17篇
  2016年   17篇
  2015年   24篇
  2014年   27篇
  2013年   28篇
  2012年   52篇
  2011年   77篇
  2010年   28篇
  2009年   33篇
  2008年   46篇
  2007年   65篇
  2006年   52篇
  2005年   60篇
  2004年   45篇
  2003年   36篇
  2002年   32篇
  2001年   11篇
  2000年   9篇
  1999年   10篇
  1998年   2篇
  1997年   3篇
  1996年   4篇
  1995年   1篇
  1994年   1篇
  1993年   3篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1979年   1篇
  1978年   2篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1968年   1篇
  1967年   1篇
  1963年   1篇
  1936年   1篇
  1935年   3篇
  1934年   1篇
  1932年   1篇
  1931年   1篇
排序方式: 共有812条查询结果,搜索用时 312 毫秒
1.
Infants living in an orphanage (n = 22) in Romania were assessed on the Test of Sensory Functions in Infants (TSFI). Testing of the institutionalized infants was done before and 6 months after an enriched caregiver intervention program. Results showed significant changes in areas of reactivity to tactile deep pressure, visual-tactile integration, oculomotor control, reactivity to vestibular stimulation and total test responses. No significant changes occurred in the area of adaptive motor functions. Effects of sensory deprivation resulting from institutional settings and changes that can occur from enriched caregiver environments are discussed.  相似文献   
2.
INTRODUCTION. This report describes the current status of nephrology and renal replacement therapy (RRT) in Romania, a country with previously limited facilities, highlighting national changes in the European context. METHODS: Trends in RRT development were analysed in 2003, on a national basis, using the same questionnaires as in previous surveys (1991, 1995). Survival data and prognostic risk factors were calculated retrospectively from a large representative sample of 2284 patients starting RRT between January 1, 1995 and December 31, 2001 (44% of the total RRT population investigated). RESULTS: In 2003, RRT incidence [128 per million population (p.m.p.)] and prevalence (250 p.m.p.) were six and five times higher, respectively, than in 1995. The annual rate of increase in the stock of RRT patients (11%) was supported mainly by an exponential development of the continuous ambulatory peritoneal dialysis (CAPD) population (+600%), while the haemodialysis (HD) growth rate was stable (+33%) and renal transplantation made a marginal contribution. Renal care infrastructure followed the same trend: nephrology departments (+100%) and nephrologists (+205%). The characteristics of RRT incident patients changed accordingly to current European epidemiology (increasing age and prevalence of diabetes and nephroangiosclerosis). The estimated overall survival of RRT patients in Romania was 90.6% at 1 year [confidence interval (CI) 89.4-91.8] and 62.2% at 5 years (CI 59.4-65.0). Patients' survival was negatively influenced (Cox regression analysis) by age >65 years (P < 0.001), lack of pre-dialysis monitoring by a nephrologist [P = 0.01, hazards ratio (HR) = 0.8], severe anaemia, lack of erythropoetin treatment (P < 0.001, HR = 0.6), and co-morbidity, e.g. cardiovascular diseases (P < 0.001, HR = 1.8) and diabetes mellitus (P < 0.001, HR = 2.2). CONCLUSIONS: Although the rate of increase in RRT patient stock in 1996-2003 in Romania was the highest in Europe, the prevalence remained below the European mean. As CAPD had the greatest expansion, followed by HD, an effective transplantation programme must be set up to overcome the imbalance. The quality of RRT appears to be good and survival was similar to that in other registries. Further evolution implies strategies of prevention, based on national surveys, supported by the Romanian Renal Registry.  相似文献   
3.
Duplication of the long arm of chromosome 1 (1q) is widely reported in human neoplasia, including the myelodysplastic syndromes (MDS). So far, it has not been described as a single aberration in the chronic myelomonocytic leukemia (CMML), a subtype of MDS. Rather, trisomy 1q was always a part of complex chromosome changes affecting the subtypes of MDS other than CMML. We report on a patient with CMML with an unbalanced translocation of the entire 1q onto the short arm of chromosome 14 as a sole cytogenetic abnormality. Fluorescence in situ hybridization (FISH) analysis with an alpha-satellite probe for the paracentric region of the long arm of chromosome 1 confirmed the presence of trisomy 1q in a derivative chromosome, der(14)t(1;14)(q12;p11). The discrepant results between the metaphase cytogenetics (100% abnormal) and interphase cytogenetic (71% nuclei with 3 signals) suggest that trisomy 1q, even in the absence of additional cytogenetic changes, has a sufficient leukemogenic potential to confer a proliferative advantage on hematopoietic cells committed to monocyte stemline both in vitro and in vivo. The literature data on partial and complete trisomy 1q in CMML is reviewed.  相似文献   
4.
5.
The aim of this research was to investigate the effect of new, non-conventional starter culture on the kinetics of the lactose transformation during milk fermentation by kombucha, at pH 5.8; 5.4; 5.1; 4.8; and 4.6, at two different temperatures 37 °C and 42 °C. Milk fermentation at 42 °C lasted significantly shorter (about 5 h, 30 min) compared to the fermentation at 37 °C. Changes of lactose concentration at the both temperatures are consisting of two retaining stages and very steep decline in–between. The analysis of the rate curves showed that the reaction rate passes through the maximum after 9 h, 30 min at 37 °C and after 4 h at 42 °C. The sigmoidal saturation curve indicates a complex kinetics of lactose fermentation by kombucha starter.  相似文献   
6.
Serotonin (5-hydroxytryptamine, 5-HT) released by platelets, mast cells, and immunocytes is a potent inflammatory mediator which modulates pain and itch sensing in the peripheral nervous system. The serotonergic receptors expressed by primary afferent neurons involved in these sensory functions are not fully identified and appear to be to a large extent species dependent. Moreover, the mechanisms through which 5-HT receptor activation is coupled to changes in neuronal excitability have not been completely revealed. Using a combination of in vitro (calcium and voltage imaging and patch-clamp) and in vivo behavioral methods, we used both male and female Wistar rats to provide evidence for the involvement of two 5-HT receptor subtypes, 5-HT1A and 5-HT3, in mediating the sustained and transient effects, respectively, of 5-HT on rat primary afferent neurons involved in pain and itch processing. In addition, our results are consistent with a model in which sustained serotonergic responses triggered via the 5-HT1A receptor are due to closure of background potassium channels, followed by membrane depolarization and action potentials, during which the activation of voltage-gated calcium channels leads to calcium entry. Our results may provide a better understanding of mammalian serotonergic itch signaling.  相似文献   
7.
Recently, chronic Aristolochia poisoning was found responsible for the aetiology of Balkan endemic nephropathy (BEN) in Croatia, Serbia, and Bosnia, and diet was the likely route of exposure to aristolochic acid (AA). BEN, often associated with an increased incidence of upper urinary tract carcinoma (UUC), also affects residents of certain rural villages in Romania. AA is a nephrotoxin and human carcinogen that forms DNA adducts after metabolic activation, which induce characteristic TP53 mutations in urothelial tumours. Here we present the first evidence linking AA exposure to UUC in residents of an endemic region in the Romanian Mehedinti County. DNA was extracted from kidney and tumour tissue of seven patients who underwent nephroureterectomy for UUC and resided in BEN villages (endemic group). Five patients with UUC from nonendemic villages served as controls. AA‐DNA adducts (7‐(deoxyadenosin‐N6‐yl)‐aristolactam I), established biomarkers of AA exposure, were identified by 32P‐postlabelling in renal DNA of six patients from the endemic group and in one of the nonendemic group (adduct levels ranged from 0.3 to 6.5 adducts per 108 nucleotides). Additionally, an A to T transversion in TP53, a base substitution characteristic of AA mutagenic activity was found in urothelial tumour DNA of one patient from the endemic group. Our results provide a molecular link to the cause of urothelial tumours in BEN regions of Romania indicating that AA is the common aetiological agent for BEN across its numerous geographical foci. Environ. Mol. Mutagen., 2012. © 2012 Wiley Periodicals, Inc.  相似文献   
8.
STUDY OBJECTIVE: To assess the accuracy of chest ultrasonography in predicting pleural effusions > 500 mL in patients receiving mechanical ventilation. DESIGN: Prospective study. SETTING: Surgical and medical ICU in a teaching hospital. PATIENTS: Forty-four patients receiving mechanical ventilation with indications of chest drainage of a nonloculated pleural effusion. INTERVENTIONS: Diagnosis of pleural effusion was based on clinical examination and chest radiography. Chest drainage was indicated when considered as potentially useful for the patient (hypoxemia and/or weaning failure). Sonograms were performed before drainage at the bedside, in the supine position, and measurements were performed at the end of expiration. Effusions were classified as > 500 mL or < or = 500 mL according to the drained volume. MEASUREMENTS AND RESULTS: The drained volume ranged from 100 to 1,800 mL (mean, 730 +/- 440 mL [+/- SD]). The distance between the lung and posterior chest wall at the lung base (PLDbase) and the distance between the lung and posterior chest wall at the fifth intercostal space (PLD5) were significantly correlated with the drained volume (PLDbase, r = 0.68, p < 0.001; PLD5, r = 0.56, p < 0.001). A PLDbase > 5 cm predicted a drained volume > 500 mL with a sensitivity of 83%, specificity of 90%, positive predictive value of 91%, and negative predictive value of 82%. Interobserver and intraobserver percentages of error were, respectively, 7 +/- 6% and 9 +/- 6% for PLDbase, and 6 +/- 5% and 8 +/- 5% for PLD5. The PaO2/fraction of inspired oxygen ratio significantly increased after chest drainage in patients with collected volumes > 500 mL (p < 0.01). CONCLUSIONS: Bedside pleural ultrasonography accurately predicted a nonloculated pleural effusion > 500 mL in patients receiving mechanical ventilation using simple and reproducible measurements.  相似文献   
9.
10.
This paper reports a systematic review of prompt-fading research, with a focus on experiments comparing two or more prompt-fading procedures. Forty-five articles with 46 experiments met the operationally-defined inclusion criteria. For the selected articles, data on several variables were extracted and analyzed. Research demonstrated that all prompt-fading procedures were generally effective in promoting acquisition of behavior. Stimulus prompting was more effective and efficient when compared to response-prompting procedures. Comparisons of response-prompting procedures yielded variable efficiency results. These outcomes are discussed in terms of the behavioral principles that facilitate transfer of stimulus control from the prompt to the discriminative stimulus, such as blocking and overshadowing. Basic investigations of the role of these behavioral principles might help develop prompt-fading procedures that are consistently effective across participants. Implications for research include suggestions for the development of individualized assessments of stimulus control, similar to the functional analysis methodology.  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