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   23046篇
  免费   1147篇
  国内免费   252篇
耳鼻咽喉   252篇
儿科学   480篇
妇产科学   667篇
基础医学   2607篇
口腔科学   523篇
临床医学   1702篇
内科学   6181篇
皮肤病学   401篇
神经病学   2490篇
特种医学   889篇
外科学   3655篇
综合类   46篇
一般理论   4篇
预防医学   904篇
眼科学   281篇
药学   1350篇
  1篇
中国医学   48篇
肿瘤学   1964篇
  2024年   62篇
  2023年   214篇
  2022年   403篇
  2021年   739篇
  2020年   460篇
  2019年   523篇
  2018年   687篇
  2017年   556篇
  2016年   639篇
  2015年   714篇
  2014年   927篇
  2013年   1119篇
  2012年   1766篇
  2011年   1791篇
  2010年   1011篇
  2009年   994篇
  2008年   1618篇
  2007年   1598篇
  2006年   1454篇
  2005年   1382篇
  2004年   1350篇
  2003年   1211篇
  2002年   1072篇
  2001年   151篇
  2000年   118篇
  1999年   163篇
  1998年   184篇
  1997年   165篇
  1996年   166篇
  1995年   126篇
  1994年   85篇
  1993年   95篇
  1992年   91篇
  1991年   68篇
  1990年   63篇
  1989年   77篇
  1988年   50篇
  1987年   64篇
  1986年   52篇
  1985年   37篇
  1984年   55篇
  1983年   48篇
  1982年   35篇
  1981年   41篇
  1980年   42篇
  1979年   19篇
  1978年   14篇
  1977年   20篇
  1976年   14篇
  1974年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
ObjectiveThe aim of the present study was to test the ability of adolescents with a current anxiety diagnosis to recognize facial affective expressions, compared to those without an anxiety disorder.MethodsForty cases and 27 controls were selected from a larger cross sectional community sample of adolescents, aged from 10 to 17 years old. Adolescent’s facial recognition of six human emotions (sadness, anger, disgust, happy, surprise and fear) and neutral faces was assessed through a facial labeling test using Ekman’s Pictures of Facial Affect (POFA).ResultsAdolescents with anxiety disorders had a higher mean number of errors in angry faces as compared to controls: 3.1 (SD = 1.13) vs. 2.5 (SD = 2.5), OR = 1.72 (CI95% 1.02 to 2.89; p = 0.040). However, they named neutral faces more accurately than adolescents without anxiety diagnosis: 15% of cases vs. 37.1% of controls presented at least one error in neutral faces, OR = 3.46 (CI95% 1.02 to 11.7; p = 0.047). No differences were found considering other human emotions or on the distribution of errors in each emotional face between the groups.ConclusionOur findings support an anxiety-mediated influence on the recognition of facial expressions in adolescence. These difficulty in recognizing angry faces and more accuracy in naming neutral faces may lead to misinterpretation of social clues and can explain some aspects of the impairment in social interactions in adolescents with anxiety disorders.  相似文献   
943.
ObjectiveTo investigate the possible correlations between clinico-radiological features and pathophysiological mechanisms in patients with dystonia secondary to focal brain lesions.MethodsSingle and paired-pulse transcranial magnetic stimulation was used to assess corticospinal excitability in 10 patients (4 females; mean age 61) and a group of normal controls. Active threshold, latency and amplitude of motor evoked potentials (MEPs), silent period (SP) duration and short-interval intracortical inhibition (SICI) were evaluated.ResultsPatients with lesions involving the putamen and caudate presented with dystonic postures at rest. TMS assessment in these subjects showed increased MEP amplitude on the affected side and a bilateral decrease of SP duration and SICI. When the lesion spared the putamen and caudate, mainly involving the thalamus, the clinical picture was dominated by slow repetitive involuntary movements and tremor. In the affected side of these subjects the MEP amplitude was reduced and the MEP threshold was increased.ConclusionsWhen putamen and caudate were lesioned, the patients presented with dystonic postures at rest; furthermore the patients showed changes of corticospinal excitability in comparison to both healthy subjects and other dystonic patients.SignificanceThere are correlations between type of dystonia, site of the lesion and neurophysiological findings.  相似文献   
944.
BackgroundSleep disordered breathing (SDB) is common in obese adults, but not all obese adults have SDB. The aim of these analyses was to determine what predicted SDB in a sample of obese adults.MethodsWe conducted cross-sectional analysis of 139 obese men and women aged 18–50 years who are chronic short sleepers. Habitual sleep duration and sleep efficiency were estimated using two weeks of wrist actigraphy. Respiratory disturbance index (RDI) was assessed by a portable screening device. SDB was defined as RDI ? 15 events h?1. Subjective sleep quality, sleepiness, and sociodemographic characteristics were evaluated by questionnaires.ResultsIncreased sleep duration from actigraphy was associated with reduced odds of SDB (OR 0.44 per hour, p = 0.043). Neither subjective sleep quality nor sleepiness was associated with SDB. Male sex, older age, and increased waist circumference were associated with increased odds of SDB.ConclusionsIn this sample of obese adults, subjective measures of sleep quality and sleepiness were not indicators of SDB. These results suggest that, in obese patients, physicians should not rely on subjective measures to determine who should be referred for a clinical sleep study. A wider use of portable apnea screening devices should be considered in nonsymptomatic, non-Hispanic white males.  相似文献   
945.
Studies reporting an inverse association between Alzheimer's disease (AD) and cancer are scant. Available data are mostly based on ancillary findings of mortality data or obtained from studies evaluating frequency of neoplasms in AD patients independently if they occurred before or after AD. Moreover, some studies estimated frequencies of neoplasms in demented individuals, who were not necessarily AD patients. We estimated frequency of tumors preceding the onset of AD in AD patients and compared it to that of age- and gender-matched AD-free individuals. Occurrence of tumors preceding AD onset was assessed through a semi-structured questionnaire. Tumors were categorized as benign, malignant, or of uncertain classification and as endocrine-related or not. Odds ratios (OR), used as measure of the association between the two diseases, were adjusted for tumor categories and known risk factors for AD and tumors. We included 126 AD patients and 252 matched controls. Tumor frequency before AD onset was 18.2% among cases and 24.2% among controls. There was a suggestive trend of an overall inverse association between the two diseases (adjusted OR 0.6; 95% CI 0.4-1.1; p = 0.11). Risk for neoplasms was significantly reduced only for women (adjusted OR, 0.5; 95% CI 0.3-0.9; p = 0.03) and for endocrine related tumors (adjusted OR, 0.5; 95% CI 0.2-1; p = 0.04). Our study confirms the inverse association reported in previous epidemiological studies. Though our findings might be explained by processes playing an opposite role in tumors development and neurodegeneration, they are also suggestive for a possible role of estrogen.  相似文献   
946.
BACKGROUND Chronic lymphocytic inflammation with pontine perivascular enhancement responsive to steroids (CLIPPERS) is a central nervous system inflammatory disease. OBJECTIVE To describe the disease course of CLIPPERS. DESIGN A nationwide study was implemented to collect clinical, magnetic resonance imaging, cerebrospinal fluid, and brain biopsy specimen characteristics of patients with CLIPPERS. SETTING Academic research. PATIENTS Twelve patients with CLIPPERS. MAIN OUTCOME MEASURES The therapeutic management of CLIPPERS was evaluated. RESULTS Among 12 patients, 42 relapses were analyzed. Relapses lasted a mean duration of 2.5 months, manifested frequent cerebellar ataxia and diplopia, and were associated with a mean Expanded Disability Status Scale (EDSS) score of 4. Besides typical findings of CLIPPERS, magnetic resonance imaging showed brainstem mass effect in 5 patients, extensive myelitis in 3 patients, and closed ring enhancement in 1 patient. Inconstant oligoclonal bands were found on cerebrospinal fluid investigation in 4 patients, with an increased T-cell ratio of CD4 to CD8. Among 7 available brain biopsy specimens, staining was positive for perivascular CD4 T lymphocytes in 5 samples. Thirty-eight of 42 relapses were treated with pulse corticosteroid therapy, which led to improvement, with a mean residual EDSS score of 1.9 (range, 0-7). In 1 patient with untreated relapses, scores on the EDSS progressively increased to a score of 10 at death. Among 5 patients without long-term corticosteroid therapy, the mean annualized relapse rate was 0.5 (range, 0.25-2.8). Among 7 patients taking oral corticosteroids, no relapses occurred in those whose daily dose was 20 mg or higher. No progressive course of CLIPPERS was observed. Four patients with a final EDSS score of 4 or higher had experienced previous severe relapses (EDSS score, ≥5) and brainstem and spinal cord atrophy. CONCLUSIONS CLIPPERS is a relapsing-remitting disorder without progressive forms. Long-term disability is correlated with the severity of previous relapses. Further studies are needed to confirm that prolonged corticosteroid therapy prevents further relapses.  相似文献   
947.
Astroglial type‐1 cannabinoid (CB1) receptors are involved in synaptic transmission, plasticity and behavior by interfering with the so‐called tripartite synapse formed by pre‐ and post‐synaptic neuronal elements and surrounding astrocyte processes. However, little is known concerning the subcellular distribution of astroglial CB1 receptors. In particular, brain CB1 receptors are mostly localized at cells' plasmalemma, but recent evidence indicates their functional presence in mitochondrial membranes. Whether CB1 receptors are present in astroglial mitochondria has remained unknown. To investigate this issue, we included conditional knock‐out mice lacking astroglial CB1 receptor expression specifically in glial fibrillary acidic protein (GFAP)‐containing astrocytes (GFAP‐CB1‐KO mice) and also generated genetic rescue mice to re‐express CB1 receptors exclusively in astrocytes (GFAP‐CB1‐RS). To better identify astroglial structures by immunoelectron microscopy, global CB1 knock‐out (CB1‐KO) mice and wild‐type (CB1‐WT) littermates were intra‐hippocampally injected with an adeno‐associated virus expressing humanized renilla green fluorescent protein (hrGFP) under the control of human GFAP promoter to generate GFAPhrGFP‐CB1‐KO and ‐WT mice, respectively. Furthermore, double immunogold (for CB1) and immunoperoxidase (for GFAP or hrGFP) revealed that CB1 receptors are present in astroglial mitochondria from different hippocampal regions of CB1‐WT, GFAP‐CB1‐RS and GFAPhrGFP‐CB1‐WT mice. Only non‐specific gold particles were detected in mouse hippocampi lacking CB1 receptors. Altogether, we demonstrated the existence of a precise molecular architecture of the CB1 receptor in astrocytes that will have to be taken into account in evaluating the functional activity of cannabinergic signaling at the tripartite synapse.  相似文献   
948.
Neostigmine test (NT) is a pharmacological test, demonstrating a clinical improvement in patients affected by myasthenia gravis (MG). We aim to compare clinical evaluation and neurophysiological recordings by concentric-needle single-fiber electromyography (CN-SFEMG) in response to acute administration of neostigmine in ocular and generalized MG patients. Twenty-three MG patients (10 with ocular MG and 13 with generalized MG) were evaluated before and after 90 min neostigmine 0.5-mg administration. Clinical responsiveness was assessed by MG composite (MGC) scale. Neurophysiological evaluation by CN-SFEMG considered analysis of mean value of consecutive differences (MCD), single-pair jitter, and blocks. MGC scores significantly improved after NT in generalized MG patients (MGC 11.1?±?7.6 vs 9.1?±?6.7, p?=?0.02), whereas the improvement was not significant in the ocular group. CN-SFEMG recordings significantly improved after NT in generalized MG patients (MCD 58.9?±?18.8 vs 45.9?±?23.2 μs, p?=?0.003; single-pair jitter 49.8?±?26.9 vs 24.1?±?26.7%, p?=?0.0001; blocks 6.2?±?9.5 vs 2.6?±?7.4%, p?=?0.03) as well as in ocular MG patients (MCD 50.8?±?22.7 vs 40.1?±?22.9 μs, p?=?0.01; single-pair jitter 35.9?±?23.7 vs 20.0?±?25.1%, p?=?0.001). CN-SFEMG is a reliable tool to evaluate responsiveness to acute administration of neostigmine in MG. Moreover, neurophysiological modifications to NT could show subclinical improvement in ocular MG better than that of the clinical scale.  相似文献   
949.
Coffee may interfere with the dopaminergic transmission, and this action would possibly enhance motor activity and exert an antidyskinetic effect in Parkinson’s disease (PD). This study aimed to see whether coffee habit could be associated with change in striatal dopamine active transporter (DAT)-single photon emission computed tomography (SPECT) imaging in PD. A total of 83 PD patients (71 current coffee drinkers and 12 never drinkers) underwent a DAT-SPECT study, using [123I]FP-CIT as radionuclide. Socio-demographic and clinical information as well as smoking habit was collected at the time of imaging acquisition. The Unified Parkinson’s Disease Rating Scale part III was used to evaluate disease severity. On multivariable analysis, chronic coffee consumption was not associated with any significant change in striatal uptake of the radionuclide. However, the number of years patients drunk coffee was correlated with a significant increase in age at PD onset (p?<?0.001). Confirming a previous report, current cigarette smoking was associated with a reduction of radionuclide uptake in putamen and caudate (p?<?0.001).  相似文献   
950.
Diffusion-weighted imaging study of patients with essential tremor.   总被引:1,自引:0,他引:1  
The pathophysiology of essential tremor (ET) is unknown. PET and fMRI studies have revealed bilateral activation and (1)H-MRS studies metabolic abnormalities in the cerebellum and other functionally related brain structures in ET. Diffusion-weighted imaging (DWI) was used to search for evidence of tissue integrity abnormalities in these areas in ET patients and 10 matched controls by calculating water apparent diffusion coefficients (ADCs). Regions of interest included the left and right cerebellum, red nucleus, thalamus, caudate, putamen, pallidum, and frontal white matter. Histograms of ADCs were generated for all pixels in the infratentorial compartment and manually segmented areas corresponding to brainstem, vermis, and cerebellar hemispheres. ADC values were similar in all brain areas in patients and controls. Our study did not detect changes affecting the investigated brain regions in ET patients. These findings argue against major structural damage in the ET brain, although more subtle neurodegenerative changes cannot be ruled out.  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