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   26943篇
  免费   2168篇
  国内免费   682篇
耳鼻咽喉   191篇
儿科学   1282篇
妇产科学   781篇
基础医学   2120篇
口腔科学   308篇
临床医学   2451篇
内科学   4985篇
皮肤病学   255篇
神经病学   987篇
特种医学   1182篇
外国民族医学   2篇
外科学   2692篇
综合类   2530篇
现状与发展   2篇
预防医学   3960篇
眼科学   224篇
药学   3670篇
  7篇
中国医学   976篇
肿瘤学   1188篇
  2024年   32篇
  2023年   562篇
  2022年   938篇
  2021年   1487篇
  2020年   1326篇
  2019年   1382篇
  2018年   1254篇
  2017年   1020篇
  2016年   914篇
  2015年   936篇
  2014年   1957篇
  2013年   1925篇
  2012年   1531篇
  2011年   1845篇
  2010年   1459篇
  2009年   1479篇
  2008年   1459篇
  2007年   1452篇
  2006年   1093篇
  2005年   969篇
  2004年   782篇
  2003年   580篇
  2002年   452篇
  2001年   411篇
  2000年   321篇
  1999年   271篇
  1998年   205篇
  1997年   203篇
  1996年   181篇
  1995年   159篇
  1994年   137篇
  1993年   115篇
  1992年   98篇
  1991年   117篇
  1990年   98篇
  1989年   73篇
  1988年   67篇
  1987年   48篇
  1986年   54篇
  1985年   69篇
  1984年   60篇
  1983年   53篇
  1982年   48篇
  1981年   38篇
  1980年   30篇
  1979年   33篇
  1978年   24篇
  1977年   10篇
  1976年   12篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
81.
82.
目的利用UPLC-LTQ-Orbitrap-MS技术对刺果番荔枝叶的化学成分进行定性分析。方法采用Waters Acquity UPLC HSS T 3色谱柱(2.1 mm×100 mm,1.8μm),流动相为0.1%甲酸水(A)和乙腈(B)梯度洗脱,流速为0.3 mL/min,进样量2μL,在电喷雾正负离子模式下采集数据。经Reaxys数据库检索番荔枝属类化合物信息,通过质谱信息比对各化合物的m/z值、保留时间、质谱特征碎片等,并结合文献数据对鉴定的化合物进行验证。结果根据各化合物的特征裂解规律,从刺果番荔枝叶中共鉴定出45个化合物,包括16个生物碱类,14个番荔枝内酯类,7个黄酮类和8个其他类化合物,其中以番荔枝内酯类和生物碱类成分居多,与文献报道番荔枝内酯与生物碱类化合物是发挥抗癌的主要活性成分一致。结论利用UPLC-LTQ-Orbitrap-MS技术对刺果番荔枝叶中的化学成分进行了快速、准确的定性分析,为刺果番荔枝叶的提取分离与药效物质基础的研究提供依据。  相似文献   
83.
同型半胱氨酸(homocysteine,Hcy)是一种含硫氨基酸,以蛋氨酸为原料合成的,通过B族维生素,可以再循环生成蛋氨酸,或者通过转硫途径转化为半胱氨酸。通常同型半胱氨酸被认为是心脑血管的独立危险因素,现研究证实同型半胱氨酸也是骨质疏松的危险因素。目前Hcy引起骨质疏松甚至骨折的确切机制已研究出一小部分,仍有待于进一步研究。在机理上,同型半胱氨酸主要通过影响骨胶原的交联,刺激破骨细胞的形成和活性增加,及通过氧化应激产生活性氧促进成骨细胞的凋亡起作用。笔者将从同型半胱氨酸与骨密度及骨代谢指标、骨折的关系进行综述,通过提前干预Hcy的水平,预防骨折的发生,为骨质疏松症患者提供一种新的治疗方案。  相似文献   
84.
ObjectivesIncreasing physical activity is a priority worldwide, including for older adults who may have difficulty performing traditional forms of exercise, and for whom retention of muscle mass is an important consideration. Water-based exercise may provide an alternative if benefits are comparable. We compared the impact on body composition of 24-week water- versus land-walking interventions in healthy but inactive older adults.DesignRandomised, controlled trial.Methods72 participants (62.5 ± 6.8 yr) were randomised to a land-walking (LW), water-walking (WW) or control (C) group in a supervised centre-based program. The exercise groups trained 3 times/week at matched intensity (%HRR), increasing from 40–45% to 55–65% heart rate reserve (HRR). Height, weight, body mass index (BMI), waist and hip girths were recorded; dual X-ray absorptiometry (DXA) provided fat and lean tissue masses. Participants were re-assessed 24 weeks after completion of the intervention.ResultsThere were no significant changes in body mass or BMI following either exercise protocol, however central adiposity was reduced in both exercise groups, and the WW group increased lower limb lean mass. These benefits did not persist over the follow-up period.ConclusionsExercise can confer beneficial effects on body composition which are not evident when examining weight or BMI. Both WW and LW improved body composition. Water walking can be recommended as an exercise strategy for this age group due to its beneficial effects on body composition which are similar to, or exceed, those associated with land-walking. For benefits to persist, it appears that exercise needs to be maintained.  相似文献   
85.
86.
87.
《Science & Sports》2022,37(7):564-571
ObjectiveObesity is the most common childhood illness in developed countries and its prevalence continues to increase. The objective was to analyze the influence of obesity on the motor coordination of children between 6 and 9 years old.Equipment and methodsA number of 52 pupils of both genders participated for evaluation of the prevalence of obesity using the measurement of the abdominal perimeter and the Body Mass Index (BMI) categorized as Normal-Weighted, Excess Weight and Obesity. The assessment of motor coordination was performed by the KTK test. SPSS (version 19.0) was used for statistical purposes.ResultsGirls had lower levels of performance rather than boys, and the pupils presented worse levels of motor performance as the age progressed. Regarding the prevalence of obesity, the two-gender obtained high mean values for the Normal-weighted category, whereas 25% is overweight. Regarding the level of motor coordination, 57.7% of the pupils had Normal Coordination and 40.4% had coordinative difficulties. Pupils with higher values of BMI and abdominal perimeter obtains lower results of motor coordination.  相似文献   
88.
Background and aimsThe negative impact of obesity on the brain is an issue of increasing clinical interest. Hence, this review summarized evidence linking obesity with brain morphology (gray and white matter volume), brain function (functional activation and connectivity), and cognitive function.MethodsA criticals review of the relevant published English articles between 2008 and 2022, using PubMed, Google Scholar and Science Direct. Studies were included if (1) an experimental/intervention study was conducted (2) the experiment/intervention included both high fat diet or body weight, whether it could counteract the negative effect brain morphological or functional change. Critical analysis for a supporting study was also carried out.ResultsBrain dysfunction can be recognized as result from neuroinflammation, oxidative stress, change in gut-brain hormonal functionality decrease regional blood flow or diminished hippocampal size and change in gut-brain hormonal functionality; which collectively translate into a cycle of deranged metabolic control and cognitive deficits, often obesity referred as changes in brain biochemistry and brain function. Recently, a few changes in brain structure and functions could be traced back even to obese children or adult. Evidence here suggested that obesity elicits early neuroinflammation effects, which likely disrupt the normal metabolism in hypothalamus, and hippocampus result from brain insulin resistance. The mechanisms of these robust effects are discussed herein.ConclusionBrain disease is inseparable from obesity itself and requires a better recognition to allow future therapeutic targeting for treatment of obesity. Additional research is needed to identify the best treatment targets and to identify if these changes reversible.  相似文献   
89.
90.
BackgroundPoor postural stability is associated with chronic ankle instability. Previous research showed an effect of foot type on postural stability. However, the specific effect of supinated feet remains unclear.Research questionOur study aimed to assess the effect of foot type on postural stability, while taking potential confounding effects of body mass and body height into account.MethodsForty-three healthy participants between 18 and 40 years old performed barefooted single leg stance tests with eyes open (EO) and closed (EC) on solid ground, and on a balance board (BB). Foot type was determined from pressure recordings during gait, using the arch index. Ground reaction forces were measured using a force plate. Outcome measures were Center of Pressure Velocity (COPV) divided by body height, and the Horizontal Ground Reaction Force (HGRF) divided by body mass. Generalized Estimating Equations models assessed the differences between supinated, normal and pronated feet during EO, EC and on a BB.ResultsDuring EO an interaction between supinated feet and body mass showed an increase of COPV with 0.03 × 10-2 1/s per kilogram of mass relative to normal feet (p = .03). During EC this interaction was more pronounced with 0.22 × 10-2 1/s increase per kilogram mass (p < .01). The HGRF did not differ between foot types in any of the conditions.SignificanceSupinated feet have a larger increase in COPV compared to normal feet with increasing mass when standing on solid ground during EO and EC. This indicates that people with supinated feet and a higher mass are less stable during single leg stance.Level of evidenceLevel 3, associative study.  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