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   9246篇
  免费   630篇
  国内免费   30篇
耳鼻咽喉   61篇
儿科学   306篇
妇产科学   256篇
基础医学   1347篇
口腔科学   158篇
临床医学   1074篇
内科学   1885篇
皮肤病学   272篇
神经病学   1042篇
特种医学   178篇
外科学   892篇
综合类   36篇
一般理论   10篇
预防医学   951篇
眼科学   150篇
药学   522篇
中国医学   18篇
肿瘤学   748篇
  2024年   10篇
  2023年   90篇
  2022年   165篇
  2021年   378篇
  2020年   235篇
  2019年   323篇
  2018年   384篇
  2017年   268篇
  2016年   282篇
  2015年   286篇
  2014年   446篇
  2013年   554篇
  2012年   831篇
  2011年   768篇
  2010年   404篇
  2009年   361篇
  2008年   524篇
  2007年   620篇
  2006年   572篇
  2005年   541篇
  2004年   460篇
  2003年   367篇
  2002年   357篇
  2001年   42篇
  2000年   40篇
  1999年   52篇
  1998年   67篇
  1997年   50篇
  1996年   41篇
  1995年   33篇
  1994年   36篇
  1993年   25篇
  1992年   26篇
  1991年   10篇
  1990年   14篇
  1989年   14篇
  1988年   10篇
  1987年   6篇
  1986年   18篇
  1985年   12篇
  1984年   11篇
  1983年   18篇
  1982年   13篇
  1981年   8篇
  1980年   15篇
  1978年   6篇
  1977年   8篇
  1975年   6篇
  1970年   7篇
  1933年   7篇
排序方式: 共有9906条查询结果,搜索用时 0 毫秒
101.
Face perception models propose that different facial attributes are processed by anatomically distinct neural pathways that partially overlap. Whether these attributes interact functionally is an open question. Our goal was to determine if there are interactions between age and ethnicity processing and, if so, at what temporal epoch these interactions are evident. We monitored event-related potentials on electroencephalography while subjects categorized faces by age or ethnicity in two conditions: a baseline in which the other of these two properties not being categorized was held constant and an interference condition in which it also varied, as modelled after the Garner interference paradigm. We found that, when participants were categorizing faces by age, variations in ethnicity increased the amplitude of the right face-selective N170 component. When subjects were categorizing faces by ethnicity, variations in age did not alter the N170. We concluded that there is an asymmetric pattern of influence between age and ethnicity on early face-specific stages of visual processing, which has parallels with behavioural evidence of asymmetric interactions between identity and expression processing of faces.  相似文献   
102.

The number of adolescent refugees around the world has been continuously increasing over the past few years trying to escape war and terror, among other things. Such experience not only increases the risk for mental health problems including anxiety, depression, and post-traumatic stress disorder (PTSD), but also may have implications for socio-cognitive development. This study tested cognitive-affective processing in refugee adolescents who had escaped armed conflict in Syria and now resided in Istanbul, Turkey. Adolescents were split into a high trauma (n = 31, 12 girls, mean age = 11.70 years, SD = 1.15 years) and low trauma (n = 27, 14 girls, mean age = 11.07 years, SD = 1.39 years) symptom group using median split, and performed a working memory task with emotional distraction to assess cognitive control and a surprise faces task to assess emotional interpretation bias. The results indicated that high (vs. low) trauma symptom youth were ~ 20% worse correctly remembering the spatial location of a cue, although both groups performed at very low levels. However, this finding was not modulated by emotion. In addition, although all youths also had a ~ 20% bias toward interpreting ambiguous (surprise) faces as more negative, the high (vs. low) symptom youth were faster when allocating such a face to the positive (vs. negative) emotion category. The findings suggest the impact of war-related trauma on cognitive-affective processes essential to healthy development.

  相似文献   
103.
ObjectivesPostoperative delirium, associated with negative consequences including longer hospital stays and worse cognitive and physical outcomes, is frequently accompanied by sleep-wake disturbance. Our objective was to evaluate the efficacy and short-term safety of ramelteon, a melatonin receptor agonist, for the prevention of postoperative delirium in older patients undergoing orthopedic surgery.DesignA quadruple-masked randomized placebo-controlled trial (Clinical Trials.gov NCT02324153) conducted from March 2017 to June 2019.SettingTertiary academic medical center.ParticipantsPatients aged 65 years or older, undergoing elective primary or revision hip or knee replacement.InterventionRamelteon (8 mg) or placeboMeasurementsEighty participants were randomized to an oral gel cap of ramelteon or placebo for 3 consecutive nights starting the night before surgery. Trained research staff conducted delirium assessments for 3 consecutive days starting on postoperative day (POD) 0, after recovery from anesthesia, and on to POD2. A delirium diagnosis was based upon DSM-5 criteria determined by expert panel consensus.ResultsOf 80 participants, five withdrew consent (one placebo, four ramelteon) and four were excluded (four ramelteon) after randomization. Delirium incidence during the 2 days following surgery was 7% (5 of 71) with no difference between the ramelteon versus placebo: 9% (3 of 33) and 5% (2 of 38), respectively. The adjusted odds ratio for postoperative delirium as a function of assignment to the ramelteon treatment arm was 1.28 (95% confidence interval: 0.21–7.93; z-value 0.27; p-value = 0.79). Adverse events were similar between the two groups.ConclusionIn older patients undergoing elective primary or revision hip or knee replacement, ramelteon was not efficacious in preventing postoperative delirium.  相似文献   
104.
In recent years, several hierarchical extensions of well-known learning algorithms have been proposed. For example, when stimulus-action mappings vary across time or context, the brain may learn two or more stimulus-action mappings in separate modules, and additionally (at a hierarchically higher level) learn to appropriately switch between those modules. However, how the brain mechanistically coordinates neural communication to implement such hierarchical learning remains unknown. Therefore, the current study tests a recent computational model that proposed how midfrontal theta oscillations implement such hierarchical learning via the principle of binding by synchrony (Sync model). More specifically, the Sync model uses bursts at theta frequency to flexibly bind appropriate task modules by synchrony. The 64-channel EEG signal was recorded while 27 human subjects (female: 21, male: 6) performed a probabilistic reversal learning task. In line with the Sync model, postfeedback theta power showed a linear relationship with negative prediction errors, but not with positive prediction errors. This relationship was especially pronounced for subjects with better behavioral fit (measured via Akaike information criterion) of the Sync model. Also consistent with Sync model simulations, theta phase-coupling between midfrontal electrodes and temporoparietal electrodes was stronger after negative feedback. Our data suggest that the brain uses theta power and synchronization for flexibly switching between task rule modules, as is useful, for example, when multiple stimulus-action mappings must be retained and used.SIGNIFICANCE STATEMENT Everyday life requires flexibility in switching between several rules. A key question in understanding this ability is how the brain mechanistically coordinates such switches. The current study tests a recent computational framework (Sync model) that proposed how midfrontal theta oscillations coordinate activity in hierarchically lower task-related areas. In line with predictions of this Sync model, midfrontal theta power was stronger when rule switches were most likely (strong negative prediction error), especially in subjects who obtained a better model fit. Additionally, also theta phase connectivity between midfrontal and task-related areas was increased after negative feedback. Thus, the data provided support for the hypothesis that the brain uses theta power and synchronization for flexibly switching between rules.  相似文献   
105.
The presence of ectopic thyroid tissue is a frequent diagnostic feedback related to a possible histogenetic abnormality or a result of post-surgical seeding. The important challenge is the diagnostic definition of its nature, which could lead to a different therapeutic approach. We describe a case with all the possible implications and differential diagnoses supported by the application of immunohistochemistry and BRAF-V600E molecular detection.  相似文献   
106.
107.
108.
Brain Imaging and Behavior - Cognitive impairment is now recognized in a subset of patients with amyotrophic lateral sclerosis (ALS). The objective of the study was to identify group differences...  相似文献   
109.
BackgroundThe possibility of decreasing or reverting left ventricular hypertrophy and, therefore, cardiac hypertrophy (CH) is an important medical issue. The aim of the present study was to evaluate these two possibilities with a 3-week daily dose of captopril, losartan, or bromocriptine in a preventive or corrective model.MethodsAfter aorto caval fistulae (ACF) surgery on adult male Wistar rats to induce CH, animals were assigned to the preventive protocol (drug treatment began immediately after surgery) or corrective protocol (hypertrophy was allowed to develop before drug treatment). After treatments, isoproterenol was administered to half of the animals to further induce CH. The groups included the passive control, the sham-operated animals, those with ACF surgery but without drug treatment, and the 3-week treatments with captopril, losartan, or the low or high dose of bromocriptine.ResultsThree treatments, with captopril, losartan, or the high dose of bromocriptine, significantly impeded/reverted an increase in CH-related parameters in the preventive/corrective model compared to the surgically treated group without drug treatment. The same effect was found after isoproterenol administration. The present results show an avoidance/reversion of CH with these three treatments. Better results were found with the angiotensin converting enzyme inhibitor (captopril) than with the prolactin inhibitor (bromocriptine).ConclusionsTreatments with captopril, losartan, and the high dose of bromocriptine were effective in preventing/reversing the manifestation of CH in the preventive/corrective rat models. Further studies are needed to identify the initial mediator, the key component, and the molecular events involved in the pathogenesis of CH.  相似文献   
110.
Spinocerebellar ataxias are phenotypically, neuropathologically, and genetically heterogeneous. The locus of autosomal recessive spinocerebellar ataxia type 7 (SCAR7) was previously linked to chromosome band 11p15. We have identified TPP1 as the causative gene for SCAR7 by exome sequencing. A missense and a splice site variant in TPP1, cosegregating with the disease, were found in a previously described SCAR7 family and also in another patient with a SCAR7 phenotype. TPP1, encoding the tripeptidyl‐peptidase 1 enzyme, is known as the causative gene for late infantile neuronal ceroid lipofuscinosis disease 2 (CLN2 disease). CLN2 disease is characterized by epilepsy, loss of vision, ataxia, and a rapidly progressive course, leading to early death. SCAR7 patients showed ataxia and low activity of tripeptidyl‐peptidase 1, but no ophthalmologic abnormalities or epilepsy. Also, the slowly progressive evolution of the disease until old age and absence of ultra structural curvilinear profiles is different from the known CLN2 phenotypes. Our findings now expand the phenotypes related to TPP1‐variants to SCAR7. In spite of the limited sample size and measurements, a putative genotype–phenotype correlation may be drawn: we hypothesize that loss of function variants abolishing TPP1 enzyme activity lead to CLN2 disease, whereas variants that diminish TPP1 enzyme activity lead to SCAR7.  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