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   49014篇
  免费   3187篇
  国内免费   193篇
耳鼻咽喉   524篇
儿科学   1241篇
妇产科学   859篇
基础医学   6406篇
口腔科学   1252篇
临床医学   4767篇
内科学   9973篇
皮肤病学   725篇
神经病学   4787篇
特种医学   2551篇
外国民族医学   6篇
外科学   7233篇
综合类   593篇
一般理论   40篇
预防医学   4018篇
眼科学   1199篇
药学   2926篇
中国医学   69篇
肿瘤学   3225篇
  2023年   206篇
  2022年   348篇
  2021年   808篇
  2020年   612篇
  2019年   811篇
  2018年   952篇
  2017年   773篇
  2016年   914篇
  2015年   1051篇
  2014年   1468篇
  2013年   2044篇
  2012年   3101篇
  2011年   3287篇
  2010年   1866篇
  2009年   1707篇
  2008年   3056篇
  2007年   3144篇
  2006年   3106篇
  2005年   3040篇
  2004年   2852篇
  2003年   2764篇
  2002年   2663篇
  2001年   620篇
  2000年   568篇
  1999年   635篇
  1998年   602篇
  1997年   471篇
  1996年   425篇
  1995年   404篇
  1994年   322篇
  1993年   292篇
  1992年   373篇
  1991年   342篇
  1990年   310篇
  1989年   328篇
  1988年   295篇
  1987年   312篇
  1986年   284篇
  1985年   302篇
  1984年   307篇
  1983年   294篇
  1982年   319篇
  1981年   299篇
  1980年   263篇
  1979年   228篇
  1978年   234篇
  1977年   195篇
  1976年   169篇
  1975年   177篇
  1974年   184篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
There is still some debate regarding the prognostic significance of left ventricular longitudinal systolic dysfunction as assessed by tissue Doppler (TD) imaging in patients with chronic heart failure (HF), since previous studies have included patients with postischemic wall motion abnormalities. Thus, this study was designed to ascertain whether TD-derived longitudinal systolic dysfunction may influence the outcome of patients with nonischemic chronic HF. In 200 consecutive patients with chronic HF secondary to dilated cardiomyopathy and no history of ischemic heart disease, peak systolic mitral annular velocity (S(m) ) was measured by pulsed TD at the septal and lateral annular sites. The end points were cardiac death or hospitalization for worsening HF. Mean follow-up duration was 30 months. In a time independent analysis, averaged S(m) calculated as the average of septal and lateral S(m) , resulted to be a significant predictor of outcome in the study population (area under receiver-operator characteristic curve: cardiovascular death, 0.69, P < 0.0001; cardiovascular events, 0.64, P = 0.0005). In a time-dependent analysis, average S(m) was associated with both cardiovascular death (hazard ratio 0.832, P = 0.0019) and cardiovascular events (hazard ratio 0.904, P = 0.039), independently of other clinical risk factors and echocardiographic parameters of systolic function. Septal S(m) but not lateral S(m) was independently associated with the outcome measures. In conclusion, the assessment of systolic mitral annular velocity by pulsed TD is a useful indicator for prognostic stratification of patients with nonischemic dilated cardiomyopathy and chronic HF.  相似文献   
993.
It has been shown in adults that individual differences in intelligence are related to the integrity of the interaction between parietal and frontal brain regions. Since connectivity between distant brain regions strengthens during childhood, it is unclear when in the course of development this relationship emerges. Thus, the goal of this study was to determine whether parietal‐frontal functional connectivity is associated with intelligence in young children. We performed independent component analyses on resting‐state fMRI data of 115 children (6–8 years old) to select seed and target regions for a seed/target region correlation analysis. We found that higher nonverbal intelligence was associated with increased functional connectivity between right parietal and right frontal regions, and between right parietal and dorsal anterior cingulate regions. The association between intelligence and functional connectivity between certain brain regions was stronger in girls than boys. In conclusion, we found that connectivity between the parietal and frontal lobes is critically involved in intelligence in young children. Hum Brain Mapp 34:3299–3307, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   
994.
BackgroundEspecially in older people, physicians are faced with the coexistence of type 2 diabetes mellitus (T2DM) and Parkinson's disease (PD). Therefore, this research aimed to compare diabetes endpoints between T2DM with and without PD.MethodsBased on the standardized, multicenter, prospective DPV database, 178,992 T2DM patients (≥40 years) were analyzed. 1579 were diagnosed with PD and/or received specific treatment. Hierarchical multivariable regression models were used for group comparisons; adjusted estimates based on observed marginal frequencies were calculated.ResultsPD patients were significantly older (77.9 vs. 70.0 years; p < 0.0001) and had a longer diabetes duration (10.3 vs. 8.4 years; p < 0.0001). In young PD patients (<50 years), percentage of females was significantly higher compared to age-matched T2DM patients without PD or people of the German population (66.7 vs. 38.1 vs. 49.0%; p < 0.0001, p < 0.02).After demographic adjustment, T2DM patients with PD showed a significantly lower HbA1c (58.0 vs. 60.3 mmol/mol; p < 0.0001), OAD/GLP-1 treatment (41.9 vs. 45.9%; p < 0.01) and frequency of dyslipidemia (62.0 vs. 64.5%; p < 0.05). In contrast, rates of insulin therapy (57.8 vs. 54.8%; p < 0.05), hypertension (73.3 vs. 68.6%; p < 0.001), antihypertensive medication (60.4 vs. 56.1%; p < 0.01), stroke (12.0 vs. 7.3%; p < 0.0001), dementia (9.2 vs. 2.6%; p < 0.0001) and repeated inpatient care (15.7 vs. 12.0%; p < 0.0001) were significantly higher and duration of hospital stay (6.2 vs. 4.7 days; p < 0.0001) was significantly longer in T2DM with PD.ConclusionClear demographic and clinical differences were observed between T2DM with and without PD. In PD patients, metabolic control is better, potentially due to more intensive medical care.  相似文献   
995.
996.
We tested the validity of the Lees-Haley Fake Bad Scale (FBS) and the family of MMPI-2 F scales (F-family; F, F(p), and F-K scales) in predicting improbable psychological trauma claims in an applied setting. Litigants reporting implausible symptoms long after minor scares and nonlitigants clinically referred following severe stressors completed the MMPI-2. Both groups were naturally matched on social class. The FBS demonstrated sensitivity, specificity, and positive predictive power in the detection of atypical problems but the F-family showed poor utility. FBS cutting scores derived from logistic regression were applied to a third group made up of litigants with histories of undeniably severe traumas. A substantial number of this third group scored above cutoffs for exaggeration, but this finding is ambiguous. Reasons for the F-family's insensitivity to real-world exaggeration may include using student simulators for validation and content reflective of psychotic simulation. The superiority of the FBS in applied forensic settings could derive from its development in actual litigants and content reflective of nonpsychotic exaggerations. The FBS appears acceptable for use in applied forensic settings where persons seek compensation for nonpsychotic syndromes.  相似文献   
997.
The acquisition of syntactic categories is a crucial step in the process of acquiring syntax. At this stage, before a full grammar is available, only surface cues are available to the learner. Previous computational models have demonstrated that local contexts are informative for syntactic categorization. However, local contexts are affected by sentence‐level structure. In this paper, we add sentence type as an observed feature to a model of syntactic category acquisition, based on experimental evidence showing that pre‐syntactic children are able to distinguish sentence type using prosody and other cues. The model, a Bayesian Hidden Markov Model, allows for adding sentence type in a few different ways; we find that sentence type can aid syntactic category acquisition if it is used to characterize the differences in word order between sentence types. In these models, knowledge of sentence type permits similar gains to those found by extending the local context.  相似文献   
998.
BackgroundFreezing of gait is a disabling feature of Parkinson's disease, and so far no established treatment exists. Deep brain stimulation of the pedunculopontine area has been proposed to treat refractory gait disorders, yet data on measurable effects, especially in combination with stimulation of other targets, are scarce.MethodsAcute effects of either low frequency pedunculopontine stimulation or high frequency stimulation of the posteroventral lateral globus pallidus internus and a combination of both in a 66-year-old man with advanced Parkinson's disease were assessed. Four weeks after the intervention, the gait was examined with patient blinded in each condition using computerized gait analysis.ResultsIsolated pedunculopontine or pallidal stimulation had a mild impact on gait ignition and freezing of gait, but combined stimulation had a marked effect.ConclusionsCombined multifocal stimulation may be a promising option for gait ignition and freezing of gait in advanced Parkinson's disease.  相似文献   
999.
Purpose: To review the use of therapeutic botulinum toxin type A (BoNT-A) treatments in uncommon neurogenetic syndromes.

Method: A retrospective questionnaire and interview study of a selected case series to assess the efficacy and safety following initial BoNT-A treatment (50–400 units per subject) was conducted to determine the response of families to treatment. Twelve male and six female subjects with ages from 2–19 years were included. The reasons for treatments were based on both patient-related and caregiver-related objectives. Satisfaction with achievement of stated goals was assessed by follow-up interviews.

Results: Beneficial effects were reported in 56%, some effects in 22% and no to minimal effects in 22%. The duration of effect ranged from 10 days to 12 months with an average of 3.16 months. Ten families would repeat the injections as needed, four would not and four were not sure. Unanticipated effects of BoNT-A treatments were reported by some families. Adverse effects did not occur with the doses that were used.

Conclusions: The results suggest that obtaining family input may be useful when treating spasticity in unusual circumstances. The use of BTX-A in uncommon neurogenetic syndromes was supported by the majority of families interviewed.  相似文献   
1000.
In cancer therapy, a promising treatment option to accomplish a high tumor-to-normal-tissue ratio is endovascular intervention with microsized particles, such as embolotherapy. In this study, alginate microspheres (ams) were prepared with the JetCutter technique, which is based on cutting a sodium alginate solution jet stream into small droplets of uniform size which are then cross-linked with different lanthanides or iron-III, resulting in microspheres of a predefined size which can be visualized by magnetic resonance imaging (MRI). The microspheres were investigated for their size and morphology (light microscopy and scanning electron microscopy analysis), cation content and MRI properties. The lanthanide-ams formulations, with a uniform size of 250 μm and a cation content between 0.72–0.94%, showed promising results for MR imaging. This was further demonstrated for Ho3+-cross-linked alginate microspheres (Ho3+-ams), the most potent microsphere formulation with respect to MR visualization, allowing single sphere detection and detailed microsphere distribution examination. Intravascular infusion of Ho3+-ams by catherization of ex vivo rabbit and porcine liver tissue and assessment of the procedure with MRI clearly showed accumulation and subsequently embolization of the targeted vessels, allowing accurate monitoring of the microsphere biodistribution throughout the tissue. Therefore, the different alginate–lanthanide microsphere formulations developed in this study show great potential for utilization as image-guided embolotherapy agents.  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