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   4167篇
  免费   308篇
  国内免费   43篇
耳鼻咽喉   26篇
儿科学   107篇
妇产科学   97篇
基础医学   620篇
口腔科学   38篇
临床医学   321篇
内科学   1143篇
皮肤病学   291篇
神经病学   558篇
特种医学   84篇
外科学   304篇
综合类   4篇
预防医学   216篇
眼科学   32篇
药学   262篇
中国医学   6篇
肿瘤学   409篇
  2024年   9篇
  2023年   52篇
  2022年   95篇
  2021年   180篇
  2020年   122篇
  2019年   132篇
  2018年   135篇
  2017年   117篇
  2016年   140篇
  2015年   170篇
  2014年   216篇
  2013年   244篇
  2012年   339篇
  2011年   339篇
  2010年   167篇
  2009年   189篇
  2008年   266篇
  2007年   263篇
  2006年   237篇
  2005年   227篇
  2004年   205篇
  2003年   201篇
  2002年   163篇
  2001年   35篇
  2000年   26篇
  1999年   27篇
  1998年   39篇
  1997年   17篇
  1996年   15篇
  1995年   21篇
  1994年   21篇
  1993年   11篇
  1992年   11篇
  1991年   11篇
  1990年   10篇
  1989年   6篇
  1988年   6篇
  1987年   8篇
  1986年   6篇
  1985年   14篇
  1984年   5篇
  1983年   4篇
  1982年   3篇
  1981年   2篇
  1980年   4篇
  1978年   1篇
  1977年   1篇
  1974年   1篇
  1970年   1篇
  1969年   3篇
排序方式: 共有4518条查询结果,搜索用时 31 毫秒
991.
According to the literature, incisional closure complications may range from postoperative surgical site infections, representing 17–22% of health care‐associated infections, surgical wound dehiscence and formation of haematomas or seromas, and can lead to delayed or impaired incision healing. These kinds of situations are more common when wounds are closed under tension or in specific patient morbidities. Obesity, in particular, is associated with an impaired blood flow to tissues, predisposing the patient to increased risk of wound complications by various mechanisms. Incisional complications can become relevant economic burdens for health care systems because of an increase in the average length of hospital stay and readmissions, and additional medical and surgical procedures. Thus, a preventive therapy may have a critical role in the management of healing. Negative pressure wound therapy (NPWT) technology as delivered by Prevena? Customizable? (Kinetic Concepts Inc., San Antonio, TX) has recently been the focus of a new investigation, as a prophylactic measure to prevent complications via immediate postoperative application in high‐risk, clean, closed surgical incisions. The authors present a 62‐year‐old class II obese female, who underwent bilateral inguinal dermolipectomy. Prophylactic NPWT as delivered by Prevena? was performed successfully over surgical incisions. Cosmetic and therapeutic results are shown.  相似文献   
992.
During infection neuraminidase desialylates platelets and induces their rapid clearance from circulation. The underlying molecular basis, particularly the role of platelet glycoprotein (GP)Ibα therein, is not clear. Utilizing genetically altered mice, we report that the extracellular domain of GPIbα, but neither von Willebrand factor nor ADAM17 (a disintegrin and metalloprotease 17), is required for platelet clearance induced by intravenous injection of neuraminidase. Lectin binding to platelet following neuraminidase injection over time revealed that the extent of desialylation of O-glycans correlates with the decrease of platelet count in mice. Injection of α2,3-neuraminidase reduces platelet counts in wild-type but not in transgenic mice expressing only a chimeric GPIbα that misses most of its extracellular domain. Neuraminidase treatment induces unfolding of the O-glycosylated mechanosensory domain in GPIbα as monitored by single-molecule force spectroscopy, increases the exposure of the ADAM17 shedding cleavage site in the mechanosensory domain on the platelet surface, and induces ligand-independent GPIb-IX signaling in human and murine platelets. These results suggest that desialylation of O-glycans of GPIbα induces unfolding of the mechanosensory domain, subsequent GPIb-IX signaling including amplified desialylation of N-glycans, and eventually rapid platelet clearance. This new molecular mechanism of GPIbα-facilitated clearance could potentially resolve many puzzling and seemingly contradicting observations associated with clearance of desialylated or hyposialylated platelet.  相似文献   
993.
BackgroundRoutine surveillance systems for pertussis often suffer from under-recognition and under-reporting.AimOur aim was to describe the epidemiology and the clinical features of pertussis in children younger than 1 year in an Italian region, detected through an enhanced hospital surveillance system.MethodsFrom 2016 to 2019, we monitored the incidence and the clinical characteristics of hospitalised pertussis cases younger than 1 year in two paediatric hospitals involved in the PERTINENT project.ResultsWe detected 141 pertussis cases, corresponding to an estimated incidence of 105.8 per 100.000 in 2016, 91.7 per 100.000 in 2017, 64.5 per 100.000 in 2018 and 40.9 per 100.000 in 2019, based on the hospitals’ catchment area, roughly corresponding to the Lazio region. A total of 101 cases (77.1%) had a household member with cough or other respiratory symptoms. The most frequent combination of symptoms was paroxysmal cough with apnoea in the absence of fever. Almost 40% had been prescribed an antibiotic treatment before hospitalisation, and the median time from symptom onset to contact with the hospital was 8 days. Thirty-one (22.0%) had complications.ConclusionAn enhanced surveillance system showed a high incidence of pertussis among infants in the Lazio region, where the impact of this disease may still be underestimated. Increasing the coverage of pertussis immunisation among pregnant women and improving the capacity for early detection in primary care may contribute to reducing the impact of pertussis among infants.  相似文献   
994.
995.
Background: To evaluate the safety and tolerability of Polyquad-preserved Travoprost (PQ-Travoprost) in patients previously treated with benzalkonium chloride (BAK)-preserved Latanoprost.

Methods: Cohort 6-month study on open-angle glaucoma or ocular hypertension patients. Complete ophthalmic examination, intraocular pressure (IOP) measurement and ocular surface status (tear film break-up time [TF-BUT], corneal staining and ocular surface disease index [OSDI]) were evaluated at baseline and 6 months later.

Results: A total of 44 patients were enrolled. Median (interquartile range [IQR]) baseline IOP was 18 (15.5 – 21) and 16 (14 – 17) mmHg (p < 0.0001) after 6 months. At baseline, 18 (40.9%) patients presented an IOP of < 18 mmHg, 11 (25%) < 16 mmHg, 2 (4.3%) < 14 mmHg and 1 (2.3%) < 12 mmHg; 6 months later the proportions were 36 (81.8%) (p < 0.0001), 21 (47.7%) (p = 0.00075), 8 (18.2%) (p = 0.0143) and 6 (13.6%) (p = 0.0253). Concerning safety, TF-BUT improved from 8 [IQR 6 – 10] to 10 [IQR 8 – 12] s (p < 0.0001). No eye developed corneal staining; punctate keratitis was absent in 13 (29.5%) patients at baseline and in 31 (70.4%) after 6 months (p < 0.001). OSDI changed from 16 (10 – 30) to 9 (2 – 20).

Conclusions: No patient treated with PQ-Travoprost developed ocular surface disease after 6 months of monotherapy, whereas many patients reached a good IOP control with lower IOP values. Ocular surface status statistically improved when examined by TF-BUT and corneal staining.  相似文献   

996.
 Obstructive sleep apnea (OSA) affects between 2% and 4% in children and there is a search for new biomarkers that can be useful both in the diagnosis and in the evolution of the disease. The surfactant protein D (SP-D) is a collection that is part of the innate immune system exerting an anti-inflammatory and antimicrobial effect. Thus, the objective of this study was to evaluate the concentration of SP-D in the suspect OSA pediatric population. A total of 178 children were recruited in this prospective study. Blood samples, sleep parameters, feeding habits, anthropometric, sociodemographic, and family data were collected. Specific biochemical determinations were made, and the plasmatic concentrations of SP-D were measured by enzyme-linked immunosorbent assay. We found no statistical correlation between the SP-D concentration and the apnea-hypopnea index (AHI) from the data. Nevertheless, the changes in SP-D levels could be correlated to a large extent by the arousals that often go along with hypopneas (r = ?0.258, p = 0.011 unadjusted; r = ?0.258, p = 0.014 adjusted by age and body mass inded [BMI] Z-score). Intermittent hypoxia was correlated with C-reactive protein levels (r = 0.547, p < 0.001 unadjusted; r = 0.542, p < 0.001 adjusted by age and BMI Z-score). Although AHI and SP-D did not appear to correlate, a secondary analysis suggests that sleep fragmentation, which is produced by arousals, may do, and further research is needed to determine the mechanisms by which changes in SP-D occur in OSA.  相似文献   
997.
998.
Introduction: The cellular prion protein (PrPC) is commonly recognized as the precursor of prions, the infectious agents of the fatal transmissible spongiform encephalopathies, or prion diseases. Despite extensive effort, the physiological role of PrPC is still ambiguous. Evidence has suggested that PrPC is involved in different cellular functions, including peripheral nerve integrity and skeletal muscle physiology. Methods: We analyzed the age‐dependent influence of PrPC on treadmill test–based aerobic exercise capacity and on a series of morphological and metabolic parameters using wild‐type and genetically modified mice of different ages expressing, or knockout (KO) for, PrPC. Results: We found that aged PrP‐KO mice displayed a reduction in treadmill performance compared with PrP‐expressing animals, which was associated with peripheral nerve demyelination and alterations of skeletal muscle fiber type. Conclusion: PrP‐KO mice have an age‐dependent impairment of aerobic performance as a consequence of specific peripheral nerve and muscle alterations. Muscle Nerve 53: 269–279, 2016  相似文献   
999.
The functional organization of the human brain consists of a high degree of connectivity between interhemispheric homologous regions. The degree of homotopic organization is known to vary across the cortex and homotopic connectivity is high in regions that share cross‐hemisphere structural connections or are activated by common input streams (e.g., the visual system). Damage to one or both regions, as well as damage to the connections between homotopic regions, could disrupt this functional organization. Here were introduce and test a computationally efficient technique, surface‐based homotopic interhermispheric connectivity (sHIC), that leverages surface‐based registration and processing techniques in an attempt to improve the spatial specificity and accuracy of cortical interhemispheric connectivity estimated with resting state functional connectivity. This technique is shown to be reliable both within and across subjects. sHIC is also characterized in a dataset of nearly 1000 subjects. We confirm previous results showing increased interhemispheric connectivity in primary sensory regions, and reveal a novel rostro‐caudal functionally defined network level pattern of sHIC across the brain. In addition, we demonstrate a structural–functional relationship between sHIC and atrophy of the corpus callosum in multiple sclerosis (r = 0.2979, p = 0.0461). sHIC presents as a sensitive and reliable measure of cortical homotopy that may prove useful as a biomarker in neurologic disease. Hum Brain Mapp 37:2849–2868, 2016. © 2016 Wiley Periodicals, Inc.  相似文献   
1000.
The mitral annulus velocities of Doppler transmitral flow and pulsed-wave tissue Doppler imaging (TDI) were sampled by echocardiography for the assessment of left ventricular (LV) diastolic function in 118 never-treated essential hypertensive patients with normal systolic function and compared with those of 59 normotensive healthy subjects matched for age and sex. A selected group (n = 26) of the hypertensive study population was observed after 1 year of pharmacologic antihypertensive treatment to determine the behavior of TDI parameters in relation to eventual regression of LV hypertrophy (LVH). We found that the TDI early myocardial diastolic wave (E(m)) was significantly lower both in concentric and eccentric LVH. In addition, TDI late myocardial diastolic wave (A(m)) was significantly higher in concentric remodeling and concentric and eccentric hypertrophy. The TDI E(m)/A(m) ratio was significantly lower in all geometric remodeling subgroups. The E/A ratio Doppler transmitral flow velocity measured showed that of the 118 patients, only 32 (25%) could really be discriminated from normal, whereas individual analysis for TDI E(m)/A(m) at the mitral annulus septal level showed that of 118 patients 108 (91%) could be discriminated from normal P < .001). The LV mass was significantly less after 1 year of treatment (LVH regression), and TDI parameters showed a trend toward normalization, in particular of TDI E(m)/A(m) at the annular septal level. Pulsed-wave TDI analysis could enable not only the early assessment of whether a patient is still in an adaptive or compensatory phase before transition to irreversible damage (pathologic phase) but also the detection of precocious LV global diastolic dysfunction. With regard to this, more extensive randomized studies are needed to evaluate the effect of different pharmacologic treatments (calcium antagonists, beta-blockers, angiotensin I and II inhibitors) on TDI parameters.  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