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   104970篇
  免费   9150篇
  国内免费   5319篇
耳鼻咽喉   1753篇
儿科学   1776篇
妇产科学   567篇
基础医学   11411篇
口腔科学   1648篇
临床医学   13197篇
内科学   8087篇
皮肤病学   517篇
神经病学   16016篇
特种医学   5344篇
外国民族医学   4篇
外科学   19937篇
综合类   17513篇
现状与发展   4篇
一般理论   1篇
预防医学   4557篇
眼科学   3239篇
药学   8246篇
  51篇
中国医学   4097篇
肿瘤学   1474篇
  2024年   233篇
  2023年   1633篇
  2022年   2399篇
  2021年   4098篇
  2020年   3934篇
  2019年   3704篇
  2018年   4153篇
  2017年   3722篇
  2016年   3861篇
  2015年   3727篇
  2014年   6560篇
  2013年   7521篇
  2012年   5898篇
  2011年   6528篇
  2010年   5628篇
  2009年   5273篇
  2008年   5365篇
  2007年   5291篇
  2006年   4957篇
  2005年   4484篇
  2004年   3584篇
  2003年   3224篇
  2002年   2760篇
  2001年   2402篇
  2000年   2224篇
  1999年   1931篇
  1998年   1831篇
  1997年   1517篇
  1996年   1275篇
  1995年   1050篇
  1994年   939篇
  1993年   841篇
  1992年   906篇
  1991年   604篇
  1990年   666篇
  1989年   476篇
  1988年   472篇
  1987年   438篇
  1986年   414篇
  1985年   528篇
  1984年   433篇
  1983年   276篇
  1982年   341篇
  1981年   276篇
  1980年   258篇
  1979年   184篇
  1978年   122篇
  1977年   124篇
  1976年   109篇
  1975年   62篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
ObjectiveHigh fluctuations in injury-risk during the playing season in soccer have been reported. As seasons are structured in periods with homogenous loads and intensities, we investigated injury-risk over season periods, contrarily to previous studies adopting a month-based approach.DesignCohort study; Level of evidence, 2.MethodsIncidence-rate ratios (IRRs) for match and training injuries were compared across six consecutive seasons of German Bundesliga, divided into six periods each: Pre-season (PS), winter-break (WB), quarter 1–4: (Q1–Q4).ResultsSignificant variations in injury-risk were observed for match and training injuries. IRRs in matches was 1.30 (95% CI: 1.11–1.53) times higher in Q3 and 1.53 (95% CI: 1.31–1.78) higher in Q4 compared to Q1. For training injuries, IRR peaked in Q1 and Q3 followed by a marked decrease in each subsequent quarter. Compared to Q4, IRR was 1.62 (95% CI: 1.40–1.86) times higher during Q3 and 1.78 (95% CI: 1.53–2.07) times higher in Q1. IRR was significantly higher in the competitive season compared to pre-season across match (IRR: 2.00, 95% CI: 1.30–3.00) and training (IRR: 1.27, 95% CI: 1.11–1.43) injuries.ConclusionsThe increased match IRRs later during the season indicate that, in practice, coaches should consider putting even more emphasis on recovery in the last part of the season. Moreover, training injuries seem to indicate a carry-over effect. Further studies need to investigate how training during preparatory phases can be implemented in a way that prevents injuries during the competitive season.  相似文献   
82.
Context: We sought to describe our experience with the Hybrid Assistive Limb® (HAL®) for active knee extension and voluntary ambulation with remaining muscle activity in a patient with complete paraplegia after spinal cord injury.

Findings: A 30-year-old man with complete paraplegia used the HAL® for 1 month (10 sessions) using his remaining muscle activity, including hip flexor and upper limb activity. Electromyography was used to evaluate muscle activity of the gluteus maximus, tensor fascia lata, quadriceps femoris, and hamstring muscles in synchronization with the Vicon motion capture system. A HAL® session included a knee extension session with the hip flexor and voluntary gait with upper limb activity. After using the HAL® for one month, the patient’s manual muscle hip flexor scores improved from 1/5 to 2/5 for the right and from 2/5 to 3/5 for the left knee, and from 0/5 to 1/5 for the extension of both knees.

Conclusion/clinical relevance: Knee extension sessions with HAL®, and hip flexor and upper-limb-triggered HAL® ambulation seem a safe and feasible option in a patient with complete paraplegia due to spinal cord injury.  相似文献   

83.
Objectives: There is a paucity of reporting on surgical outcomes of isolated posterior cruciate ligament reconstruction (PCLR). We hypothesize that isolated PCL injuries failing nonoperative treatment achieve good outcomes and are able to return to sport following PCLR.

Methods: A retrospective analysis was performed to identify patients with isolated PCL injuries that underwent reconstruction between 2001 and 2014. Patients with multi-ligamentous injury or another concomitant knee pathology were excluded. Medical records were reviewed for demographic, clinical and operative data. Patients were contacted for administration of a telephone-based questionnaire which included the International Knee Documentation Committee (IKDC) Subjective Knee Evaluation form, Lysholm-Tegner scales, Marx activity scale (MAS), return to sport status, and patient satisfaction instruments.

Results: A total of 15 isolated PCL reconstructions in 14 patients with a mean age of 27.5 years (range 17–43) met the study inclusion criteria; mean follow up was 6.3 years (range 1.4–15.2). Pre-operatively, the primary complaint was knee instability in all patients; on physical examination, lack of a firm end point during posterior drawer testing was found in 93% (14/15) of the knees. In total, 12 of 15 knees underwent transtibial, single-bundle PCLR and three of 15 underwent tibial inlay, double bundle PCLR. Graft types included: quadriceps autograft (7/15), Achilles allograft (6/15), and hamstring autograft (2/15). There were no graft failures in our patient cohort. At most recent follow up the mean scores respectively on the IKDC form, Lysholm-Tegner scales and MAS were (standard deviation): 77.3 (16.5), 83.1 (17.9), 6.13 (2.6), and 7.1 (6.0). All fourteen patients were athletes prior to their injury and 79% (11/14) returned to sport and overall patient satisfaction was 9.2/10.

Conclusions: Isolated PCLR provides good outcomes at mean medium-term follow up with restoration of function, high rate of return to sport and overall patient satisfaction.  相似文献   

84.
目的 探讨N-乙酰-5-羟色胺(N-acetylserotonin,NAS)对视网膜缺血-再灌注损伤(retina ischemia-reperfusion injury,RIRI)大鼠视网膜Fas、FasL蛋白表达的影响。方法 取健康成年Sprague Dawley大鼠54只,将大鼠随机分为正常组(6只)、RIRI组(24只)与NAS组(24只);采用高眼压法建立大鼠RIRI模型,依据造模后不同时间点将RIRI组与NAS组大鼠又分为6 h、12 h、24 h及72 h四个亚组。NAS组于造模前30 min腹腔注射NAS(5 mg·kg-1),RIRI组腹腔注射等剂量的生理盐水。通过HE染色在光学显微镜下观察各组大鼠视网膜形态学变化,并记录各组大鼠视网膜厚度及视网膜神经节细胞数,采用免疫组织化学染色法检测NAS对RIRI大鼠视网膜Fas、FasL蛋白表达的影响。结果 HE染色显示,正常组大鼠视网膜各层细胞分界清晰,形态正常,神经细胞排列整齐;RIRI组大鼠再灌注后6 h视网膜各层出现水肿,以神经节细胞层及内核层较显著,神经节细胞数较正常组减少;随后视网膜水肿进一步加重,神经节细胞继续减少;NAS组大鼠在再灌注后6 h、12 h、24 h 视网膜水肿程度较 RIRI组轻,NAS组在再灌注后72 h视网膜厚度较 RIRI组厚,NAS组各时间点神经节细胞数均较 RIRI组多,差异均有统计学意义(均为P<0.05)。免疫组织化学染色显示,正常组几乎未见 Fas+细胞。再灌注后6 h,RIRI组视网膜神经节细胞及内核层开始出现少量 Fas+细胞;再灌注后12 h,RIRI组视网膜 Fas+细胞表达逐渐增多;再灌注后24 h视网膜Fas+细胞数达到高峰,棕色阳性染色细胞分布在视网膜神经节细胞层、内丛状层、内核层及神经纤维层;再灌注后 72 h 视网膜 Fas+细胞较再灌注后 24 h 减少。NAS组在再灌注后6 h、12 h、24 h、72 h 视网膜 Fas+细胞数均较 RIRI组各时间点减少,再灌注后24 h,Fas+细胞数达较高水平,随后下降,差异均有统计学意义(均为P<0.05)。正常组视网膜可见 FasL 全层低表达。RIRI组再灌注后 6 h,视网膜神经节细胞层和神经纤维层存在少量 FasL+细胞;再灌注后12 h FasL蛋白表达逐渐增多;再灌注后24 h FasL+细胞数达高峰,可见深棕色的细胞膜及细胞质染色细胞分布在视网膜神经节细胞层、内丛状层、内核层及神经纤维层;再灌注后72 h FasL蛋白的阳性表达逐渐减少。NAS组再灌注后6 h、12 h、24 h、72 h 视网膜FasL+细胞数均少于 RIRI组各时间点阳性细胞数,差异均有统计学意义(均为P<0.05)。结论 NAS可通过抑制RIRI大鼠视网膜细胞Fas、FasL蛋白的表达,减轻缺血再灌注对大鼠视网膜细胞造成的损伤。  相似文献   
85.
A multitude of athletic injuries occur when the various tissues that make up the human body experience stresses and strains that exceed their material strength. The precise amount of stress and strain that any given tissue can withstand is determined by the mechanical properties and resultant strength of that particular tissue. These mechanical properties are directly determined by an individual’s physiology and acute regulation of these properties. A number of theoretical frameworks for athletic injury occurrence have been proposed, however, a detailed conceptual framework for injury aetiology that considers the interplay between the physiological and mechanical factors and outlines the causal pathways to tissue damage and injury is needed. This will guide injury research towards a more thorough investigation of causal mechanisms and understanding of risk factors. Further, it is important to take into account the considerable differences in loading patterns which can result in varying injury outcomes such as acute stress-related, strain-related, or overuse injury. Within this article a simplified conceptual model of athletic injury is proposed along with a detailed, evidence-informed, conceptual framework for athletic injury aetiology that focuses on stress-related, strain-related, and overuse injury.  相似文献   
86.
Objective: The objective of this study was to gain greater insight into individuals’ quality of life (QOL) definitions, appraisals, and adaptations following spinal cord injury (SCI).

Design: A mixed-methods design, applying the Schwartz and Sprangers response shift (RS) model. RS is a cognitive process wherein, in response to a change in health status, individuals change internal standards, values, or conceptualization of QOL

Setting: Community-dwelling participants who receive medical treatment at a major Midwestern medical system and nearby Veterans’ Affairs hospital.

Participants: A purposive sample of participants with SCI (N?=?40) completed semi-structured interviews and accompanying quantitative measures.

Interventions: Not applicable.

Outcome Measures: Qualitative data were analyzed using content analysis to identify themes. Analysis of variance were performed to detect differences based on themes and QOL, well-being, and demographic and injury characteristics.

Results: Four RS themes were identified, capturing the range of participant perceptions of QOL. The themes ranged from complete RS, indicating active engagement in maintaining QOL, to awareness and comparisons redefining QOL, to a relative lack of RS. Average QOL ratings differed as a function of response shift themes. PROMIS Global Health, Anxiety, and Depression also differed as a function of RS themes.

Conclusion: The RS model contextualizes differences in QOL definitions, appraisals, and adaptations in a way standardized QOL measures alone do not.  相似文献   

87.
88.
Sleep-wake rhythm disturbances,which are characterized by abnormal sleep timing or duration,are associated with cognitive dysfunction.Photoacoustic treatments including light and sound stimulation have been found to be effective in modulating sleep patterns and improving cognitive behavior in abnormal sleep-wake pattern experiments.In this study,we examined whether light and sound interventions could reduce sleep-wake pattern disturbances and memory deficits in a sleep rhythm disturbance model.We established a model of sleep rhythm disturbance in C57 BL/6 J mice via a sleep deprivation method involving manual cage tapping,cage jostling,and nest disturbance.We used a Mini Mitter radio transmitter device to monitor motor activity in the mice and fear conditioning tests to assess cognitive function.Our results indicated that an intervention in which the mice were exposed to blue light(40-Hz flickering frequency)for 1 hour during their subjective daytime significantly improved the 24-hour-acrophase shift and reduced the degree of memory deficit induced by sleep deprivation.However,interventions in which the mice were exposed to a 40-Hz blue light at offset time or subjective night time points,as well as 2 Hz-blue light at 3 intervention time points(subjective day time,subjective night time,and offset time points),had no positive effects on circadian rhythm shift or memory deficits.Additionally,a 2000-Hz sound intervention during subjective day time attenuated the24-hour-acrophase shift and memory decline,while 440-Hz and 4000-Hz sounds had no effect on circadian rhythms.Overall,these results demonstrate that photoacoustic treatment effectively corrected abnormal sleep-wake patterns and cognitive dysfunction associated with sleep-deprivation-induced disturbances in sleep-wake rhythm.All animal experiments were approved by the Experimental Animal Ethics Committee of Drum Tower Hospital Affiliated to the Medical College of Nanjing University,China(approval No.20171102)on November20,2017.  相似文献   
89.

Background

There is a need for a peripheral nerve model on which surgeons-in-training can simulate the repair of nerve injuries at their own pace. Although practicing on animal models/cadavers is considered the “gold standard” of microsurgical training, the proposed model aims to provide a platform for improving the technical skills of surgical trainees prior to their practice on cadaver/animal models. In addition, this model has the potential to serve as a standardized test medium for assessing the skill sets of surgeons.

Methods

Several formulations of silicone were utilized for the design and fabrication of a model which realizes the hierarchical structure of peripheral nerves. The mechanical properties were characterized via the Universal Testing Machine; the damage caused by the needle on the entry sites was assessed through scanning electron microscopy (SEM).

Results

Mechanical properties of the formulations of silicone were tested to mimic human peripheral nerves. A formulation with 83.3?wt% silicone oil and 0.1?wt% cotton fiber was chosen to be used as nerve fascicles. Both 83.3?wt% silicone oil with cotton fiber and 66.6?wt% silicone oil without fiber provided a microsuturing response similar to that of epineurium at a wall thickness of 1?mm. SEM also confirmed that the entry of the needle did not introduce significant holes at the microsuturing sites.

Conclusions

The proposed peripheral nerve model mimicked human tissues mechanically and cosmetically, and a simulation of the repair of a fifth-degree nerve injury was achieved.  相似文献   
90.
IntroductionThis article deals with the occurrence of health problems due to gunshot wounds to the face among military police officers, in the metropolitan region of Rio de Janeiro, who were submitted to surgery at the Oral and Maxillofacial Surgery and Traumatology Clinic of Hospital Central da Polícia Militar.ObjectiveTo identify the profile of patients submitted to surgery as a result of gunshot wounds, the anatomical distribution of maxillofacial fractures, the identified sequelae and complications, the health specialties involved in the rehabilitation of these patients, and to discuss the social, emotional and work performance-related effects of work among these subjects.MethodsA retrospective epidemiological study was carried out based on secondary data from military police officers who were submitted to surgery at Hospital Central da Polícia Militar due to gunshot wounds from June 2003 to December 2017.ResultsDuring the study period, 778 surgeries were performed in the operating room by the Oral and Maxillofacial Surgery and Traumatology service at Hospital Central da Polícia Militar, 186 of which were due to gunshot wounds (23.9%). All patients were males and the mean age 34.7 years. Bone segment loss was the most common sequela. Facial esthetic impairment and reports of insomnia were the most often identified late consequences of impact on health and social life. Regarding the occupational impacts of the sustained injury, the mean time away from work due to medical leave for the treatment of maxillofacial injuries was 11.7 months.ConclusionThe treatment of gunshot wounds patients with facial injuries requires multiple surgical interventions and their rehabilitation requires the involvement of different health specialties. Further studies are needed to qualitatively analyze the impact of this type of facial trauma on the patients' lives and their social consequences.  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