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   4885篇
  免费   487篇
  国内免费   64篇
耳鼻咽喉   34篇
儿科学   551篇
妇产科学   35篇
基础医学   442篇
口腔科学   25篇
临床医学   488篇
内科学   227篇
皮肤病学   11篇
神经病学   1526篇
特种医学   87篇
外科学   314篇
综合类   522篇
预防医学   507篇
眼科学   26篇
药学   395篇
  4篇
中国医学   207篇
肿瘤学   35篇
  2024年   6篇
  2023年   78篇
  2022年   166篇
  2021年   273篇
  2020年   249篇
  2019年   206篇
  2018年   218篇
  2017年   214篇
  2016年   199篇
  2015年   187篇
  2014年   362篇
  2013年   394篇
  2012年   265篇
  2011年   317篇
  2010年   255篇
  2009年   215篇
  2008年   207篇
  2007年   235篇
  2006年   170篇
  2005年   150篇
  2004年   103篇
  2003年   99篇
  2002年   93篇
  2001年   70篇
  2000年   64篇
  1999年   52篇
  1998年   51篇
  1997年   45篇
  1996年   39篇
  1995年   44篇
  1994年   26篇
  1993年   27篇
  1992年   19篇
  1991年   27篇
  1990年   30篇
  1989年   26篇
  1988年   16篇
  1987年   30篇
  1986年   13篇
  1985年   25篇
  1984年   24篇
  1983年   23篇
  1982年   22篇
  1981年   16篇
  1980年   19篇
  1979年   16篇
  1978年   7篇
  1977年   15篇
  1976年   13篇
  1974年   6篇
排序方式: 共有5436条查询结果,搜索用时 31 毫秒
31.
胎儿宫内窘迫对新生儿神经行为的影响   总被引:2,自引:0,他引:2  
目的:测定宫内窘迫的新生儿神经行为,以探讨宫内窘迫与新生儿神经行为表现、预后的关系。方法:用NBNA神经行为20项指标进行测定。结果:宫内窘迫新生儿60例与正常新生儿60例比较,测定总分之间差异有显著性(P<0.01)。窘迫组中41例无窒息者与正常对照差异有显著性(P<0.01),窘迫组中19例有窒息者与正常对照组差异更为显著,急性窘迫38例与慢性窘迫22例之间也有显著差异(P<0.001)。结论:胎儿宫内窘迫影响新生儿的神经行为能力。  相似文献   
32.
目的探讨注意缺陷多动障碍(attentiondeficithyperactivitydisorder,ADHD)儿童的视觉机能特征。方法采用本顿视觉保持测验(Bentonvisualretentiontest,BVRT)、连线测验(TrailMakingTest,TMT)及符号-数字模式测验(Symbol-DigitModalitiesTest,SDMT)3种方法,分别测试50例ADHD儿童和50例正常儿童的视知觉、视觉记忆、视空间结构、视觉运动注意和视觉扫描等。结果①ADHD组BVRT三种测验方试C、D、E正确分总分(4.9±2.0)低于对照组(7.7±1.4)(t总=8.00,P<0.01),而失误分总分(6.9±3.9)高于对照组(2.5±1.7)(t总=12.1,P<0.01)。②ADHD组完成A型TMT时间较对照组延长(94.6±51.2/56.9±23.7,t=4.61,P<0.05),所犯错误次数与对照组相比差异有显著性(0.3±0.8/0.1±0.3,Hc=4.46,P<0.05);ADHD组完成B型TMT时间较对照组延长(228.0±142.1/120.1±43.8,t=5.14,P<0.05),所犯错误次数较对照组明显增多(6.0±5.5/2.1±3.4,Hc=22.96,P<0.01)。③ADHD组SDMT得分低于对照组(65.2±29.3/97.9±18.8,t=6.65,P<0.01)。结论ADHD儿童存在视知觉、视觉记忆、视空间结构、视觉运动注意以及视觉扫描等视觉机能方面缺陷。  相似文献   
33.
目的:探讨注意缺陷多动障碍(Attention deficit hyperactivity disorder,ADHD)儿童在罗夏测验中的表现特征及可能的投射机制。方法:采用国内修订版罗夏测验(Rorschach Inkblot Test,RIT),结合艾森克人格问卷(EPQ)对40名ADHD男童和40名对照组儿童进行了测试。结果:ADHD儿童在RIT变量Zf、COP、3r 2/R、Zd、X %、Sum6的得分低于对照组(P<0.05);而在变量AG、Lambda、Sh、X-%、SCZI、DEPI、CDI的得分高于对照组(P<0.05);两组儿童在RIT多个变量和EPQ各分量表之间存在相关。结论:ADHD儿童在RIT中表现出较多的在客体关系、情绪特质、自我功能和认知功能方面的缺陷,说明RIT可投射出ADHD儿童内心世界的一些特点,包括自我意识不良、人际关系不良、攻击性、情绪问题、认知过程和思维能力问题。  相似文献   
34.
Summary Major changes occur in the serum level of several hormones during 5 days of heavy and continuous physical activities, with less than a total of 2 h of sleep. The present investigation was designed to evaluate the importance of caloric deficiency, energy requirement being about 8,000–10,000 kcal/24 h. A comparison between well fed subjects and those with food deprivation revealed significantly higher levels of (T3) triiodothyronin, insulin and thyroid stimulating hormone (TSH) in the well-fed subjects, who also had lower levels of growth hormone (hGH) and cortisol, whereas no difference was found between the two groups for thyroxin (T4). Increased levels were found for T3 and T4 in both groups during the first day of activity, with a concomitant decrease in TSH and a subsequent decrease of T4 during the next 2 days. T3 decreased only in the low-calory group whereas increased levels were found in the iso-calory group throughout the course. The resting levels of insulin decreased during the course in the low-calory group whereas it increased in the iso-calory group. High levels were maintained throughout the course for hGH. Cortisol showed high levels just before the start of the course and then decreased from day 2 to day 4. No difference was found between the morning and evening levels for cortisol, indicating disappearance of the circadian rhythm. The present investigation has shown that energy deficiency during prolonged physical strain is responsible for the decreased serum levels of T3 and insulin and may contribute to the decrease in TSH and the increase in hGH and cortisol.  相似文献   
35.
ADHD儿童在钟表绘画测验中的执行功能特征   总被引:2,自引:0,他引:2  
目的研究ADHD儿童在钟表绘画(CDT)测试中体现出的执行功能特征。方法对60例ADHD儿童和60例正常对照儿童进行CDT测试,综合分析两组儿童的大脑额叶执行功能的差异。结果ADHD儿童在CDT测试中的时间总分和构造总分低于对照组(3.23±1.40/4.15±0.78,11.2±1.48/11.90±0.76,t=7.742、5.073,P<0.01)。在给定十字位相标定点(3、6、9、12点)后ADHD儿童的钟面构造得分高于给定标定点之前(11.93±0.95/11.19±1.48,t=5.645,P<0.001),但时间设置评分却没有明显的提高(P>0.05)。结论ADHD儿童CDT测试得分偏低体现了其存在计划性、注意调控功能和工作记忆的缺陷,这些缺陷的核心问题是执行功能的缺陷。  相似文献   
36.

Background

Variants in GBA are the most common genetic risk factor for Parkinson's disease (PD), and are especially prevalent in the Ashkenazi Jewish (AJ) population. However, most studies on GBA in AJ genotype only seven selected Gaucher-associated pathogenic variants rather than sequencing the whole gene, which may leave carriers of PD-associated GBA variants undiscovered.

Methods

GBA was fully sequenced using molecular inversion probes (MIPs) and Sanger sequencing in 735 AJ PD patients and 662 AJ controls, from Israel and New York. Additional AJ control data (n?=?3044) from the Inflammatory Bowel Disease Exome Portal was used.

Results

Full GBA sequencing increased the number of variants discovered by 17.4%, compared to targeted genotyping. An additional 17 PD patients were identified with GBA-associated PD. The p.E326K variant was found in 1.6% of AJ PD patients, making it the second most common PD-associated GBA variant in AJ. GBA variants were found in 18% of PD patients and 7.5% of controls (OR?=?2.7, 95%CI?=?1.9–3.8, p?<?0.0001).

Conclusion

Without full sequencing of GBA, or at minimum including p.E326K in the genotyping panel, a significant proportion of variant carriers go undiscovered and may be incorrectly assigned as non-carriers in studies or clinical trials.  相似文献   
37.
Summary The primary tethered cord syndrome has been documented mainly in children and adolescents but also in adults, and patients may present with backache, neuromuscular skeletal changes such as club-foot, scoliosis, muscular atrophy, disturbances of gait, or dysfunction of bladder and rectum, or a combination of these conditions. The cadaveric case presented describes plain film radiographic and anatomical findings of spina bifida occulta at the first and second sacral levels, and an enlarged spinous process of the fifth lumbar vertebra, in a 78 year old male cadaver with a tethered spinal cord terminating at the first sacral level. During life, this man had not undergone surgery for tethered spinal cord.
Revue du syndrome de moelle attachée: étude radiologique et anatomique à propos d'un cas
Résumé Le syndrome de moelle attachée primaire a souvent été décrit chez l'enfant et l'adolescent mais aussi chez l'adulte, les patients pouvant se présenter avec des douleurs du dos, des modifications neuro-musculaires et squelettiques comme un pied bot, une scoliose, une atrophie musculaire, des anomalies de la marche, des dysfonctionnements de la vessie et/ou du rectum, ou une combinaison de ces différents symptômes. L'observation rapportée ici est l'étude anatomique et radiologique d'un spina bifida oculta des première et deuxième vertèbres sacrées associé à l'élargissement du processus épineux de la cinquième vertèbre lombaire chez un cadavre mâle de 78 ans ayant une moelle épinière attachée au niveau de la première vertèbre sacrée. Durant sa vie ce patient n'avait pas subi de chirurgie pour cette moelle attachée.
  相似文献   
38.
The concept of the accumulated O2 deficit (AOD) assumes that the O2 deficit increases monotonically with increasing work rate (WR), to plateau at the maximum AOD, and is based on linear extrapolation of the relationship between measured steady-state oxygen uptake (O2) and WR for moderate exercise. However, for high WRs, the measured O2 increases above that expected from such linear extrapolation, reflecting the superimposition of a "slow component" on the fundamental O2 mono-exponential kinetics. We were therefore interested in determining the effect of the O2 slow component on the computed AOD. Ten subjects [31 (12) years] performed square-wave cycle ergometry of moderate (40%, 60%, 80% and 90% ), heavy (40%), very heavy (80%) and severe (110% O2 peak) intensities for 10–15 min, where is the estimated lactate threshold and is the WR difference between and O2 peak. O2 was determined breath-by-breath. Projected "steady-state" O2 values were determined from sub- tests. The measured O2 exceeded the projected value after ~3 min for both heavy and very heavy intensity exercise. This led to the AOD actually becoming negative. Thus, for heavy exercise, while the AOD was positive [0.63 (0.41) l] at 5 min, it was negative by 10 min [–0.61 (1.05) l], and more so by 15 min [–1.70 (1.64) l]. For the very heavy WRs, the AOD was [0.42 (0.67) l] by 5 min and reached –2.68 (2.09) l at exhaustion. For severe exercise, however, the AOD at exhaustion was positive in each case: +1.69 (0.39) l. We therefore conclude that the assumptions underlying the computation of the AOD are invalid for heavy and very heavy cycle ergometry (at least). Physiological inferences, such as the "anaerobic work capacity", are therefore prone to misinterpretation.  相似文献   
39.
Differences between hyperkinetic children and normal children and the effects of methylphenidate on hyperkinetic children were investigated under conditions of differential attentional demands. Auditory average evoked potentials were recorded from vertex using a single/double click guessing paradigm under conditions of certainty and uncertainty. Under conditions of certainty (low attention), in which the subject was told the identity of each stimulus in advance, few significant group differences were found. Under conditions of uncertainty (high attention), in which the subject was asked to guess which stimulus would be presented, large group differences were found. In response to the second click the P200 component was found to be smaller and the N250 component was larger in hyperkinetic children than in normal children. Treatment with methylphenidate “normalized” the evoked potentials of the hyperkinetic children making them more like those of normal children. The findings are believed: 1) to reflect the deficit in attention observed behaviorally in hyperkinetic children, 2) to support a model of hypoarousal in hyperkinetic children, and 3) to reflect the behavioral “normalization” observed in hyperkinetic children treated with melhylphenidate.  相似文献   
40.
Publication bias in reproductive research   总被引:3,自引:0,他引:3  
Publication bias is defined as any tendency on the part of investigators or editors to fail to publish study results on the basis of the direction or strength of the findings. This may lead to overestimation of treatment effects in published work. Inappropriate decisions about patient management may result. We investigated what proportion of abstracts at the European Society of Human Reproduction and Embryology (ESHRE) annual meeting eventually reached full publication, what was the time to publication, and which factors might have affected publication. Among the 2691 abstracts of six ESHRE annual meetings, 151 (5.6%) reporting randomized controlled trials (RCT) were identified. Comprehensive searches of electronic databases and handsearching of the two major journals in the field yielded 79 full publications pertaining to these abstracts. Kaplan-Meier analysis estimated 56% of RCT abstracts to be eventually published in full, the median time to publication being 32.5 months. Positive outcome (i.e. significant results) did not affect the publication rate, and neither did sample size, the subject category, or the native language (English/non-English) of the country of origin. Oral presentations resulted in eventual full publication significantly more frequently (69%) than posters (42%). It is concluded that a considerable publication deficit, but not a publication bias, exists for RCT in reproductive research.  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