全文获取类型
收费全文 | 1296篇 |
免费 | 104篇 |
国内免费 | 12篇 |
专业分类
耳鼻咽喉 | 4篇 |
儿科学 | 58篇 |
妇产科学 | 12篇 |
基础医学 | 129篇 |
口腔科学 | 13篇 |
临床医学 | 163篇 |
内科学 | 243篇 |
皮肤病学 | 8篇 |
神经病学 | 87篇 |
特种医学 | 154篇 |
外科学 | 203篇 |
综合类 | 24篇 |
一般理论 | 1篇 |
预防医学 | 162篇 |
眼科学 | 68篇 |
药学 | 57篇 |
1篇 | |
肿瘤学 | 25篇 |
出版年
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2016年 | 9篇 |
2015年 | 14篇 |
2014年 | 24篇 |
2013年 | 31篇 |
2012年 | 51篇 |
2011年 | 46篇 |
2010年 | 25篇 |
2009年 | 26篇 |
2008年 | 47篇 |
2007年 | 49篇 |
2006年 | 59篇 |
2005年 | 54篇 |
2004年 | 52篇 |
2003年 | 41篇 |
2002年 | 44篇 |
2001年 | 48篇 |
2000年 | 36篇 |
1999年 | 34篇 |
1998年 | 29篇 |
1997年 | 27篇 |
1996年 | 27篇 |
1995年 | 20篇 |
1994年 | 29篇 |
1993年 | 20篇 |
1992年 | 23篇 |
1991年 | 28篇 |
1990年 | 25篇 |
1989年 | 38篇 |
1988年 | 35篇 |
1987年 | 40篇 |
1986年 | 29篇 |
1985年 | 19篇 |
1984年 | 25篇 |
1983年 | 28篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 24篇 |
1979年 | 23篇 |
1978年 | 11篇 |
1977年 | 14篇 |
1976年 | 22篇 |
1975年 | 10篇 |
1974年 | 15篇 |
1972年 | 8篇 |
1970年 | 9篇 |
1969年 | 6篇 |
排序方式: 共有1412条查询结果,搜索用时 46 毫秒
81.
P Ellwood M I Asher B Bj?rkstén M Burr N Pearce C F Robertson 《The European respiratory journal》2001,17(3):436-443
Several studies have suggested that the increasing prevalence of symptoms of asthma, rhinitis and eczema, could be associated with dietary factors. In the present paper, a global analysis of prevalence rates of wheeze, allergic rhinoconjunctivitis and atopic eczema was performed in relation to diet, as defined by national food intake data. Analyses were based on the International Study of Asthma and Allergies in Childhood (ISAAC) data for 6-7 and 13-14 yr old children. Symptoms of wheeze, allergic rhinoconjunctivitis and atopic eczema symptom prevalence were regressed against per capita food intake, and adjusted for gross national product to account for economic development. Dietary data were based on 1995 Food and Agriculture Organisation of the United Nations data for 53 of the 56 countries that took part in ISAAC phase I (1994/1995). The 13-14 year age group showed a consistent pattern of decreases in symptoms of wheeze (current and severe), allergic rhinoconjunctivitis and atopic eczema, associated with increased per capita consumption of calories from cereal and rice, protein from cereals and nuts, starch, as well as vegetables and vegetable nutrients. The video questionnaire data for 13-14 yr olds and the ISAAC data for 6-7 yr olds showed similar patterns for these foods. A consistent inverse relationship was seen between prevalence rates of the three conditions and the intake of starch, cereals, and vegetables. If these findings could be generalised, and if the average daily consumption of these foods increased, it is speculated that an important decrease in symptom prevalence may be achieved. 相似文献
82.
Sixty-three patients (32 women, 31 men), chronically treated with carbamazepine, phenytoin, valproate and/or phenobarbital, were investigated. Mean age at manifestation of epilepsy was 16.4 years; mean age at onset of documentation of seizure frequency was 33.7 years; mean duration of follow-up was 104.8 months; mean number of documented seizures per patient was 313.2. A statistical analysis of seizure diaries was performed. For each day the entries were the number of seizures per day. Linear trends, the amount of variance of the seizure frequency compared to randomly distributed events, were computed with the resulting coefficients fitting a general linear regression model. Non-random aggregations (clusters) were searched for as well as gaps of seizure manifestation. A similar number of patients exhibited a decrease (30%) or increase (29%) of seizure frequency during the course of epilepsy. The variance of the daily seizure frequency was in most patients (78%) significantly higher or lower (5%) than corresponding random distributions. The coupling coefficient to the day before was significantly larger than zero (indicating seizure clustering) in 57% of patients. Significant rhythmic components in seizure profiles (quasi-weekly or quasi-monthly) were found in 31 patients (both male and female). Periods of increased seizure frequency (clusters) manifested in 62% of patients; seizure gaps of at least 1 year occurred in 29 patients followed by seizure relapses in 20 patients. In conclusion, there is no evidence for a unique type of course in chronic focal epilepsy in patients on antiepileptic drugs. 相似文献
83.
Thompson EA Zhu S Hall JR House JS Ranjan R Burr JA He YY Owens DM Smart RC 《The Journal of investigative dermatology》2011,131(6):1339-1346
Human epidermis is routinely subjected to DNA damage induced by UVB solar radiation. Cell culture studies have revealed an unexpected role for C/EBPα (CCAAT/enhancer-binding protein-α) in the DNA damage response network, where C/EBPα is induced following UVB DNA damage, regulates the G(1) checkpoint, and diminished or ablated expression of C/EBPα results in G(1) checkpoint failure. In the current study we observed that C/EBPα is induced in normal human epidermal keratinocytes and in the epidermis of human subjects exposed to UVB radiation. The analysis of human skin precancerous and cancerous lesions (47 cases) for C/EBPα expression was conducted. Actinic keratoses, a precancerous benign skin growth and precursor to squamous cell carcinoma (SCC), expressed levels of C/EBPα similar to normal epidermis. Strikingly, all invasive SCCs no longer expressed detectable levels of C/EBPα. To determine the significance of C/EBPα in UVB-induced skin cancer, SKH-1 mice lacking epidermal C/EBPα (CKOα) were exposed to UVB. CKOα mice were highly susceptible to UVB-induced SCCs and exhibited accelerated tumor progression. CKOα mice displayed keratinocyte cell cycle checkpoint failure in vivo in response to UVB that was characterized by abnormal entry of keratinocytes into S phase. Our results demonstrate that C/EBPα is silenced in human SCC and loss of C/EBPα confers susceptibility to UVB-induced skin SCCs involving defective cell cycle arrest in response to UVB. 相似文献
84.
Tortelli Chiara Turi Marco Burr David C. Binda Paola 《Journal of autism and developmental disorders》2021,51(8):2908-2919
Journal of Autism and Developmental Disorders - We measured the pupil response to a light stimulus subject to a size illusion and found that stimuli perceived as larger evoke a stronger pupillary... 相似文献
85.
Rebecca A. Gladstone Ebrima Bojang John Hart Emma M. Harding-Esch David Mabey Ansumana Sillah Robin L. Bailey Sarah E. Burr Anna Roca Stephen D. Bentley Martin J. Holland 《Clinical microbiology and infection》2021,27(6):864-870
ObjectiveMass drug administration (MDA) with azithromycin for trachoma elimination reduces nasopharyngeal carriage of Streptococcus pneumoniae in the short term. We evaluated S. pneumoniae carried in the nasopharynx before and after a round of azithromycin MDA to determine whether MDA was associated with changes in pneumococcal population structure and resistance.MethodsWe analysed 514 pneumococcal whole genomes randomly selected from nasopharyngeal samples collected in two Gambian villages that received three annual rounds of MDA for trachoma elimination. The 514 samples represented 293 participants, of which 75% were children aged 0–9 years, isolated during three cross-sectional surveys (CSSs) conducted before the third round of MDA (CSS-1) and at 1 (CSS-2) and 6 (CSS-3) months after MDA. Bayesian Analysis of Population Structure (BAPS) was used to cluster related isolates by capturing variation in the core genome. Serotype and multilocus sequence type were inferred from the genotype. Antimicrobial resistance determinants were identified from assemblies, including known macrolide resistance genes.ResultsTwenty-seven BAPS clusters were assigned. These consisted of 81 sequence types (STs). Two BAPS clusters not observed in CSS-1 (n = 109) or CSS-2 (n = 69), increased in frequency in CSS-3 (n = 126); BAPS20 (8.73%, p 0.016) and BAPS22 (7.14%, p 0.032) but were not associated with antimicrobial resistance. Macrolide resistance within BAPS17 increased after treatment (CSS-1 n = 0/6, CSS-2/3 n = 5/5, p 0.002) and was carried on a mobile transposable element that also conferred resistance to tetracycline.DiscussionLimited changes in pneumococcal population structure were observed after the third round of MDA, suggesting treatment had little effect on the circulating lineages. An increase in macrolide resistance within one BAPS highlights the need for antimicrobial resistance surveillance in treated villages. 相似文献
86.
Transrenal fixation of aortic stent-grafts for the treatment of infrarenal aortic aneurysmal disease
Bove PG Long GW Zelenock GB Bendick PJ Khoury MD Burr MO Bechtel G Becker F Huckabone C 《Journal of vascular surgery》2000,32(4):697-703
PURPOSE: We evaluated our early experience with the transrenal fixation of aortic stent-grafts to determine the efficacy of this procedure and its effects on renal artery patency and hemodynamics. METHODS: Twenty-eight patients (22 men) had endoluminally placed modular bifurcated stent-grafts with a bare spring structure at the proximal end crossing the origin of both renal arteries; no patient with infrarenal fixation was included for analysis. The mean age of the patients was 75 +/- 7 years (range, 58-86 years); the mean aneurysm size was 5.8 +/- 0.8 cm (range, 4.7-7.2 cm). Eight patients had preoperative or intraoperative angiographic evidence of renal artery atherosclerotic disease, but only four vessels had luminal narrowing of 50% or greater. No complications were noted during stent-graft placement, and all patients have returned for follow-up visits, ranging from 1 to 12 months (mean follow-up, 6 +/- 4 months). Follow-up evaluations included clinical assessment, duplex ultrasound scan of the renal arteries and kidneys, and computed tomographic angiography. RESULTS: No evidence of lobular or sublobular perfusion defects of the renal parenchyma was detected postoperatively. Two patients exhibited postoperative changes in renal artery hemodynamics-one progressing from a 30% diameter reduction to a greater than 60% diameter stenosis at the 12-month follow-up visit and one with a normal renal artery preoperatively having elevated flow velocities indicative of a greater than 60% stenosis at the 1-month visit. Of 19 patients with normal preoperative renal function, only one has had persistently elevated serum creatinine levels. CONCLUSION: We conclude from this experience that the transrenal placement of open stents is safe and effectively excludes the aneurysm, potentially expanding the availability of this technique to more patients with a short infrarenal aortic neck. Long-term follow-up is essential to determine the overall efficacy of this technique and to identify potential effects on renal artery hemodynamics or kidney function. 相似文献
87.
Gamma detectors at border crossings are intended to detect illicit nuclear material. One of their performance challenges is the fact that vehicles suppress the natural background and, thus, potentially reduce probability of detection of threat items. Here we test several methods to adjust the detection to background suppression in the context of signal estimation.We show that, for the small-to-moderate suppression magnitudes, suppression adjustment leads to higher detection probability. However, for signals triggering alarm without an adjustment, adjustment does not improve estimation of the signal location, only moderately improves estimation of the signal magnitude, and does not improve estimation of the signal width. 相似文献
88.
Bone adaptation to a mechanical loading program significantly increases skeletal fatigue resistance. 总被引:6,自引:0,他引:6
Stuart J Warden Julie A Hurst Megan S Sanders Charles H Turner David B Burr Jiliang Li 《Journal of bone and mineral research》2005,20(5):809-816
Using a mechanical loading program to induce bone adaptation, we found that small (<2-fold) changes in the structural properties of the rat ulna increased its fatigue resistance >100-fold. This indicates that a moderate exercise program may be an effective preventative strategy for stress fractures. INTRODUCTION: There are currently limited preventative strategies for stress fractures. Because stress fracture risk is directly influenced by skeletal properties, it has been hypothesized that modification of these properties using a mechanical loading program may positively influence risk. The aim of this study was to investigate whether the bone changes associated with a mechanical loading program can enhance skeletal fatigue resistance. MATERIALS AND METHODS: Site-specific mechanical loading was performed on one forearm of adult female Sprague-Dawley rats using the axial compression loading model. Loading was performed 3 days/week for 5 consecutive weeks to induce adaptation. The loaded and nonloaded ulnas in each animal were removed after the loading program, and their material and structural properties were determined. The ulna pairs were subsequently loaded until fatigue failure at the same constant peak axial load. RESULTS: Mechanical loading induced consistent and predictable changes in the structural properties of loaded ulnas, with the largest change being a nearly 2-fold increase in midshaft minimum second moment of area (I(MIN)). The mechanical-loading induced bone changes resulted in a >100-fold increase in fatigue resistance in loaded ulnas, with resistance being exponentially related to the structural properties of the ulna. CONCLUSIONS: This study found that by enhancing the structural properties of a bone through a mechanical loading program, its fatigue resistance could be significantly improved. This indicates that an exercise program aimed at modifying bone structure may be used as a possible prevention strategy for stress fractures. 相似文献
89.
90.
Mary E. Barasi Michael L. Burr Emma J. E. Robshaw David J. Poor 《Journal of human nutrition and dietetics》1991,4(5):307-315
A postal survey of dietary fibre intake was conducted in two British towns in 1983, and repeated five years later. Consumption of dietary fibre had risen, the rise being greater in the town where the initial intake was higher. Changes in intake appeared to be related to health-consciousness as reflected by changes in body mass index (BMI) and smoking habit. Although dietary fibre consumption in Britain is rising overall, local differences may be widening rather than narrowing. 相似文献