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   137828篇
  免费   12374篇
  国内免费   3628篇
耳鼻咽喉   1064篇
儿科学   1938篇
妇产科学   1378篇
基础医学   12235篇
口腔科学   4561篇
临床医学   22093篇
内科学   15234篇
皮肤病学   1457篇
神经病学   12072篇
特种医学   24893篇
外国民族医学   304篇
外科学   12377篇
综合类   18102篇
现状与发展   11篇
预防医学   5171篇
眼科学   1947篇
药学   8122篇
  72篇
中国医学   3972篇
肿瘤学   6827篇
  2024年   132篇
  2023年   1988篇
  2022年   2810篇
  2021年   4806篇
  2020年   4931篇
  2019年   4720篇
  2018年   4741篇
  2017年   4865篇
  2016年   5152篇
  2015年   5109篇
  2014年   12325篇
  2013年   11270篇
  2012年   9332篇
  2011年   9727篇
  2010年   9583篇
  2009年   9356篇
  2008年   7627篇
  2007年   6447篇
  2006年   5622篇
  2005年   4922篇
  2004年   4196篇
  2003年   3399篇
  2002年   2688篇
  2001年   2526篇
  2000年   2022篇
  1999年   1631篇
  1998年   1458篇
  1997年   1363篇
  1996年   1146篇
  1995年   1146篇
  1994年   956篇
  1993年   790篇
  1992年   685篇
  1991年   598篇
  1990年   493篇
  1989年   373篇
  1988年   370篇
  1987年   318篇
  1986年   254篇
  1985年   301篇
  1984年   263篇
  1983年   189篇
  1982年   203篇
  1981年   214篇
  1980年   175篇
  1979年   128篇
  1978年   107篇
  1977年   77篇
  1976年   103篇
  1975年   39篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
BackgroundThe impact of removing the upper airway lymphoid tissue and in particular, tonsillectomy, in adults with OSA has not been demonstrated in large populations.AimsTo compare the severity of OSA and the prevalence of cardiovascular, metabolic and respiratory co-morbidities between patients with OSA who had undergone previous tonsillectomy and those who had not.MethodsThe 19,711 participants in this study came from the European sleep apnea database (ESADA) which comprises data from unselected adult patients aged 18–80 years with a history of symptoms suggestive of OSA referred to sleep centers throughout Europe.ResultsThere were no differences between the two groups in terms of sex ratio and age (146 patients with previous tonsillectomy vs. 19565 patients without). Patients who had undergone tonsillectomy had a lower body mass index (29.3 ± 5.2 kg/m2 vs 32.2 ± 6.6 kg/m2, p < 0.001), lower subjective sleep latency (17.1 ± 17.8 min vs 25.5 ± 30.4 min, p = 0.001), lower ODI (15.7 ± 18.3 events/hour vs 30.7 ± 26.1 events/hour, p < 0.001), and SpO2<90% time during sleep (21.8 ± 47.5 min vs 52.6 ± 80.8 min, p < 0.001). OSA patients with tonsillectomy had a lower prevalence of Type II diabetes mellitus (p = 0.001), hypertension (p < 0.001) and a higher prevalence of hyperlipidemia (p < 0.001) and were less likely to be commenced on CPAP (p < 0.001).ConclusionIn a large population of almost 20,000 OSA patients from across Europe, patients who had undergone tonsillectomy presented with less severe OSA at time of diagnosis, and had a lower prevalence of Type II diabetes mellitus and cardiovascular co-morbidities.  相似文献   
34.
35.
Arguably, the two most important causes of pathological healing in the skin are diabetes and ageing. While these factors have historically been considered independent modifiers of the healing process, recent studies suggest that they may be mechanistically linked. The primary contributor to diabetic pathology is hyperglycaemia, which accelerates the production of advanced glycation end products, a characteristic of ageing tissue. Indeed, advanced age also leads to mild hyperglycaemia. Here, we discuss emerging literature that reveals a hitherto unappreciated link between cellular senescence, diabetes and wound repair. Senescent cells cause widespread destruction of normal tissue architecture in ageing and have been shown to be increased in chronic wounds. However, the role of senescence remains controversial, with several studies reporting beneficial effects for transiently induced senescence in wound healing. We recently highlighted a direct role for senescence in diabetic healing pathology, mediated by the senescence receptor, CXCR2. These findings suggest that targeting local tissue senescence may provide a therapeutic strategy applicable to a broad range of chronic wound types.  相似文献   
36.
PurposeThe purpose of this study was to compare morphologic assessment and relaxometry of patellar hyaline cartilage between conventional sequences (fast spin-echo [FSE] T2-weighted fat-saturated and T2-mapping) and synthetic T2 short-TI inversion recovery (STIR) and T2 maps at 1.5 T magnetic resonance imaging (MRI).MethodThe MRI examinations of the knee obtained at 1.5 T in 49 consecutive patients were retrospectively studied. There were 21 men and 28 women with a mean age of 45 ± 17.7 (SD) years (range: 18–88 years). Conventional and synthetic acquisitions were performed, including T2-weighted fat-saturated and T2-mapping sequences. Two radiologists independently compared patellar cartilage T2-relaxation time on conventional T2-mapping and synthetic T2-mapping images. A third radiologist evaluated the patellar cartilage morphology on conventional and synthetic T2-weighted images. The presence of artifacts was also assessed. Interobserver agreement for quantitative variables was assessed using intraclass correlation coefficient (ICC).ResultsIn vitro, conventional and synthetic T2 maps yielded similar mean T2 values 58.5 ± 2.3 (SD) ms and 58.8 ± 2.6 (SD) ms, respectively (P = 0.414) and 6% lower than the expected experimental values (P = 0.038). Synthetic images allowed for a 15% reduction in examination time compared to conventional images. On conventional sequences, patellar chondropathy was identified in 35 patients (35/49; 71%) with a mean chondropathy grade of 4.8 ± 4.8 (SD). On synthetic images, 28 patients (28/49; 57%) were diagnosed with patellar chondropathy, with a significant 14% difference (P = 0.009) and lower chondropathy scores (3.7 ± 4.9 [SD]) compared to conventional images. Motion artifacts were more frequently observed on synthetic images (18%) than on conventional ones (6%). The interobserver agreement was excellent for both conventional and synthetic T2 maps (ICC > 0.83). Mean cartilage T2 values were significantly greater on synthetic images (36.2 ± 3.8 [SD] ms; range: 29-46 ms) relative to conventional T2 maps (31.8 ± 4.1 [SD] ms; range: 26-49 ms) (P < 0.0001).ConclusionDespite a decrease in examination duration, synthetic images convey lower diagnostic performance for chondropathy, greater prevalence of motion artifacts, and an overestimation of T2 values compared to conventional MRI sequences.  相似文献   
37.
PurposeThe purpose of this study was to investigate right atrial and ventricular strain parameters on cardiac magnetic resonance (CMR) in patients with precapillary pulmonary hypertension (PPH) and whether they can aid in the assessment of PPH prognosis.Materials and methodsAdult patients with groups 1 and 4 PPH were invited to participate in the study. Age- and sex-matched healthy volunteers were also recruited as controls. At baseline, patients underwent clinical examination, N-terminal pro-B-type natriuretic peptide measurement and CMR with feature tracking post-processing (CMR-FT). Healthy controls underwent only CMR-FT. The study's primary endpoint was clinical failure, defined as death, hospitalization or demonstrable clinical deterioration during follow-up. Patients who were unable to perform 6-minute walking test due to musculoskeletal disorders were excluded from the study.ResultsThirty-six patients (8 men, 28 women; mean age, 50.6 ± 13.8 [SD] years [range: 18.6–78.5 years]) and 12 healthy control subjects (5 mean, 7 women; mean age, 40.6 ± 13.5 [SD] years [range: 23.1–64.4 years]) were recruited. Right ventricular global longitudinal strain (GLS) was significantly impaired in PPH patients (?20.2 ± 5.3 [SD] % [range: ?28.8 to ?9.1%] vs. ?28.4 ± 3.1% [?33.7 to ?22.7%] respectively, P < 0.001). The right atrial GLS was significantly impaired in PPH compared to healthy controls (?19.9 ± 4.5% [range: ?28.6 to ?3.6%] vs. ?26.5 ± 4.2% [range: ?32.8 to ?15.8%] respectively) (P < 0.001). Clinical failure occurred in 19 (19/36, 53%) of patients. Right ventricular GLS predicted clinical failure most reliably among CMR parameters (?22.6 ± 3.8 [SD] % [range: ?27.6 to ?12.7%] for patients without clinical failure vs. ?18 ± 5.6 [SD] % [range: ?28.8 to ?9.1%] for patients with clinical failure; hazard ratio [HR] = 1.85; P = 0.007; area under the AUC curve = 0.75). Lower absolute right atrial GLS was significantly associated with clinical failure (?22.7 ± 3.0 [SD] % [range: ?28.6 to ?17.7%] for patients without clinical failure vs. ?16.9 ± 5.8 [SD] % [range: ?24.2 to ?3.6%] for patients with clinical failure) (HR = 1.53; P = 0.035).ConclusionCMR feature tracking-derived myocardial strain parameters of both the right atrium and ventricle can assist clinicians in the prognosis of PPH.  相似文献   
38.
Backgrounds:The main objective of this study was to compare the pain control efficacy of local administration of Lidocaine with or without the nonsteroidal anti-inflammatory drug, Ketorolac, and local conventional Lidocaine injection in core needle biopsy of the musculoskeletal tumor.Methods:The current study was a randomized, double-blind controlled clinical trial that included 128 patients with suspected musculoskeletal tumors. Patients were randomly assigned to either the Ketorolac plus Lidocaine (n = 64) or Lidocaine group (n = 64). The Ketorolac – Lidocaine combination syringe contained 30 mg Ketorolac and 2% Lidocaine – adrenaline dosage, and the Lidocaine syringe contained 2% Lidocaine – adrenaline dosage. The level of pain after core needle biopsy was evaluated for each patient at 1, 6, 12, 24, 48, and >48 hours by a Visual Analog Scale (VAS). The mean VAS changes over time were compared between the Ketorolac plus Lidocaine and Lidocaine groups using a linear mixed model.Results:baseline information including mean age of patients in Lidocaine group (51.5 ± 19.4 years) and in Lidocaine – Ketorolac combination group (50.1 ± 18 years), diagnosis (malignant, benign, metastatic, infection), tumor location (upper and lower extremities, back), VAS score 1-hour post-operation (mild and moderate pain) were noted. The VAS score ratings were significantly lower in Lidocaine – Ketorolac combination group when compared to the Lidocaine group during the 1 to 24 hours post-operation time period.Conclusion:Patients receiving Lidocaine – Ketorolac combination dosage had significantly lower VAS scores, and these results confirm that local injection of Lidocaine – Ketorolac combination had a superior pain-controlling effect during the first 24 hours after the biopsy procedure in comparison to Lidocaine injection alone, as measured by VAS score scale.  相似文献   
39.
目的探析慢性阻塞性肺疾病合并侵袭性肺曲霉菌病患者的临床特点。方法对医院2018年2月—2019年12月间收治的慢性阻塞性肺疾病合并侵袭性肺曲霉菌病患者24例相关临床数据进行回顾性分析,归纳此类患者的临床特点,以期为以后收治此类患者在诊疗上提供可参考数据。结果慢性阻塞性肺疾病合并侵袭性肺曲霉菌病患者典型临床症状为肺部罗音、呼吸障碍、胸痛、咳嗽咳痰、发热。影像学检查后典型表现为肺部炎性渗出、空洞、结节、实变。经过积极治疗后有8例患者判定为治疗有效。结论收治慢性阻塞性肺疾病合并侵袭性肺曲霉菌病患者应该做到早期阶段准确诊断,积极治疗,是保障预后的重点。  相似文献   
40.
Amacrine cells of the retina are conspicuously variable in their morphologies, their population demographics, and their ensuing functions. Vesicular glutamate transporter 3 (VGluT3) amacrine cells are a recently characterized type of amacrine cell exhibiting local dendritic autonomy. The present analysis has examined three features of this VGluT3 population, including their density, local distribution, and dendritic spread, to discern the extent to which these are interrelated, using male and female mice. We first demonstrate that Bax-mediated cell death transforms the mosaic of VGluT3 cells from a random distribution into a regular mosaic. We subsequently examine the relationship between cell density and mosaic regularity across recombinant inbred strains of mice, finding that, although both traits vary across the strains, they exhibit minimal covariation. Other genetic determinants must therefore contribute independently to final cell number and to mosaic order. Using a conditional KO approach, we further demonstrate that Bax acts via the bipolar cell population, rather than cell-intrinsically, to control VGluT3 cell number. Finally, we consider the relationship between the dendritic arbors of single VGluT3 cells and the distribution of their homotypic neighbors. Dendritic field area was found to be independent of Voronoi domain area, while dendritic coverage of single cells was not conserved, simply increasing with the size of the dendritic field. Bax-KO retinas exhibited a threefold increase in dendritic coverage. Each cell, however, contributed less dendrites at each depth within the plexus, intermingling their processes with those of neighboring cells to approximate a constant volumetric density, yielding a uniformity in process coverage across the population.SIGNIFICANCE STATEMENT Different types of retinal neuron spread their processes across the surface of the retina to achieve a degree of dendritic coverage that is characteristic of each type. Many of these types achieve a constant coverage by varying their dendritic field area inversely with the local density of like-type neighbors. Here we report a population of retinal amacrine cells that do not develop dendritic arbors in relation to the spatial positioning of such homotypic neighbors; rather, this cell type modulates the extent of its dendritic branching when faced with a variable number of overlapping dendritic fields to approximate a uniformity in dendritic density across the retina.  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