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   34173篇
  免费   3894篇
  国内免费   1144篇
耳鼻咽喉   165篇
儿科学   1904篇
妇产科学   746篇
基础医学   3089篇
口腔科学   806篇
临床医学   4120篇
内科学   5366篇
皮肤病学   234篇
神经病学   1769篇
特种医学   1384篇
外国民族医学   9篇
外科学   5363篇
综合类   4690篇
现状与发展   4篇
一般理论   1篇
预防医学   3358篇
眼科学   957篇
药学   2739篇
  12篇
中国医学   1072篇
肿瘤学   1423篇
  2024年   28篇
  2023年   554篇
  2022年   768篇
  2021年   1344篇
  2020年   1361篇
  2019年   1382篇
  2018年   1328篇
  2017年   1233篇
  2016年   1205篇
  2015年   1187篇
  2014年   2195篇
  2013年   2637篇
  2012年   1940篇
  2011年   2110篇
  2010年   1706篇
  2009年   1690篇
  2008年   1783篇
  2007年   1760篇
  2006年   1595篇
  2005年   1541篇
  2004年   1321篇
  2003年   1155篇
  2002年   939篇
  2001年   855篇
  2000年   768篇
  1999年   604篇
  1998年   492篇
  1997年   494篇
  1996年   421篇
  1995年   347篇
  1994年   316篇
  1993年   275篇
  1992年   240篇
  1991年   197篇
  1990年   149篇
  1989年   138篇
  1988年   121篇
  1987年   110篇
  1986年   75篇
  1985年   150篇
  1984年   125篇
  1983年   112篇
  1982年   103篇
  1981年   107篇
  1980年   80篇
  1979年   40篇
  1978年   33篇
  1977年   29篇
  1976年   21篇
  1975年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
目的观察叶酸和维生素B12对绝经后骨质疏松症妇女的骨代谢及同型半胱氨酸水平的影响。方法 80例绝经后骨质疏松症妇女参加研究。所有参与者随机接受叶酸和维生素B12(n=40)或安慰剂(n=40)治疗。在干预前的基线及干预后3个月和6个月,测量两组患者血清同型半胱氨酸、维生素B12和骨代谢标志物的水平。结果治疗前,两组患者血清同型半胱氨酸、维生素B12和骨代谢标志物水平比较差异无统计学意义(P0.05)。治疗后,两组患者同型半胱氨酸均下降,但比较差异无统计学意义(P0.05)。6个月后各组间血清维生素B12、骨钙素、CTX的变化均有显著改变且差异有统计学意义(P0.05)。结论绝经后骨质疏松症妇女补充叶酸和维生素B12可以一定程度改善同型半胱氨酸及骨代谢指标水平。  相似文献   
22.
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   
23.
24.
《Clinical neurophysiology》2019,130(5):727-738
ObjectiveFunctional processes in the brain are segregated in both the spatial and spectral domain. Motivated by findings reported at the cortical level in healthy participants we test the hypothesis in the basal ganglia of Parkinson’s disease patients that lower frequency beta band activity relates to motor circuits associated with the upper limb and higher beta frequencies with lower limb movements.MethodsWe recorded local field potentials (LFPs) from the subthalamic nucleus using segmented “directional” DBS leads, during which patients performed repetitive upper and lower limb movements. Movement-related spectral changes in the beta and gamma frequency-ranges and their spatial distributions were compared between limbs.ResultsWe found that the beta desynchronization during leg movements is characterised by a strikingly greater involvement of higher beta frequencies (24–31 Hz), regardless of whether this was contralateral or ipsilateral to the limb moved. The spatial distribution of limb-specific movement-related changes was evident at higher gamma frequencies.ConclusionLimb processing in the basal ganglia is differentially organised in the spectral and spatial domain and can be captured by directional DBS leads.SignificanceThese findings may help to refine the use of the subthalamic LFPs as a control signal for adaptive DBS and neuroprosthetic devices.  相似文献   
25.
Currently, adoptive immunotherapy is considered as one of the leading treatments in cancer. Successful adoptive immunotherapy depends on producing large numbers of desired T cells ex vivo for infusion. This requires an effective protocol for maximum functional T‐cell expansion while keeping the time and costs to a minimum. Current T‐cell expansion protocols are diverse in their methodology, and a universal protocol of expansion is wanting. Also, new findings regarding T‐cell biology, signaling, and activation have reshaped the strategies of T‐cell propagation over the years, introducing new ways to expand T cells. Here, we reviewed different conditions for blood‐derived polyclonal T‐cell expansion so as to elucidate the influential factors of T‐cell expansion and their efficacy.  相似文献   
26.
27.
28.
目的从基因分子水平探讨酒精性骨质疏松(alcoholic osteoporosis,AOP)大鼠的发病机制,观察生髓健骨胶囊对AOP大鼠骨密度(bone mineral density,BMD)、骨矿含量(bone mineral content,BMC)表达的影响,探讨生髓健骨胶囊对AOP大鼠模型的中药防治作用机理。方法选取成年雄性(清洁级)SD大鼠120只,称体重,随机分为4组,每组各30只,用白酒灌胃法造模,同时分别给予生理盐水、碳酸钙阿法D3、生髓健骨胶囊灌胃给药。于造模8、12、16周末取材,检测股骨上端BMD、BMC指标。结果检测造模干预8、12、16周后BMD、BMC指标变化,模型组BMD、BMC与正常组比较明显降低,且差异有统计学意义(P0.01),结果表明饮酒大鼠确实存在骨量减少,BMD、BMC降低;中药干预组BMD、BMC与模型组相比显著升高(P0.01);中药干预组BMD、BMC与西药对照组相比,明显升高(P0.05)。结论通过观察生髓健骨胶囊对AOP大鼠的实验指标,证明了生髓健骨胶囊能够提高AOP大鼠骨密度,增加骨矿含量,抑制矿物质丢失,改善大鼠的骨代谢。  相似文献   
29.
30.
Purpose: Non-ambulatory persons with cerebral palsy are prone to low bone mineral density. In ambulatory persons with cerebral palsy, bone mineral density deficits are expected to be small or absent, but a consensus conclusion is lacking. In this systematic review bone mineral density in ambulatory persons with cerebral palsy (Gross Motor Function Classification Scales I–III) was studied.

Materials and methods: Medline, Embase, and Web of Science were searched. According to international guidelines, low bone mineral density was defined as Z-score?≤??2.0. In addition, we focused on Z-score?≤??1.0 because this may indicate a tendency towards low bone mineral density.

Results: We included 16 studies, comprising 465 patients aged 1–65?years. Moderate and conflicting evidence for low bone mineral density (Z-score?≤??2.0) was found for several body parts (total proximal femur, total body, distal femur, lumbar spine) in children with Gross Motor Function Classification Scales II and III. We found no evidence for low bone mineral density in children with Gross Motor Function Classification Scale I or adults, although there was a tendency towards low bone mineral density (Z-score?≤??1.0) for several body parts.

Conclusions: Although more high-quality research is needed, results indicate that deficits in bone mineral density are not restricted to non-ambulatory people with cerebral palsy.

  • Implications for Rehabilitation
  • Although more high-quality research is needed, including adults and fracture risk assessment, the current study indicates that deficits in bone mineral density are not restricted to non-ambulatory people with CP.

  • Health care professionals should be aware that optimal nutrition, supplements on indication, and an active lifestyle, preferably with weight-bearing activities, are important in ambulatory people with CP, also from a bone quality point-of-view.

  • If indicated, medication and fall prevention training should be prescribed.

  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