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   978篇
  免费   50篇
  国内免费   3篇
耳鼻咽喉   1篇
儿科学   12篇
妇产科学   39篇
基础医学   204篇
口腔科学   8篇
临床医学   61篇
内科学   90篇
皮肤病学   9篇
神经病学   362篇
特种医学   3篇
外科学   69篇
综合类   3篇
预防医学   91篇
眼科学   7篇
药学   48篇
中国医学   2篇
肿瘤学   22篇
  2023年   4篇
  2022年   11篇
  2021年   21篇
  2020年   9篇
  2019年   19篇
  2018年   14篇
  2017年   19篇
  2016年   17篇
  2015年   18篇
  2014年   40篇
  2013年   31篇
  2012年   66篇
  2011年   63篇
  2010年   28篇
  2009年   29篇
  2008年   56篇
  2007年   72篇
  2006年   67篇
  2005年   47篇
  2004年   58篇
  2003年   55篇
  2002年   48篇
  2001年   31篇
  2000年   28篇
  1999年   28篇
  1998年   12篇
  1997年   3篇
  1996年   5篇
  1995年   2篇
  1993年   7篇
  1992年   14篇
  1991年   8篇
  1990年   8篇
  1989年   6篇
  1988年   8篇
  1987年   5篇
  1986年   6篇
  1985年   14篇
  1984年   5篇
  1983年   2篇
  1982年   5篇
  1980年   2篇
  1979年   9篇
  1977年   3篇
  1976年   2篇
  1975年   9篇
  1974年   6篇
  1971年   2篇
  1968年   2篇
  1966年   1篇
排序方式: 共有1031条查询结果,搜索用时 15 毫秒
21.
22.
There is a broad range of patient travel distances to reach a lung transplant hospital in the United States. Whether patient travel distance is associated with waitlist outcomes is unknown. We present a cohort study of patients listed between January 1, 2006 and May 31, 2017 using the Scientific Registry of Transplant Recipients. Travel distance was measured from the patient's permanent zip code to the transplant hospital using shared access signature URL access to Google Maps, and assessed using multivariable competing risk regression models. There were 22 958 patients who met inclusion criteria. Median travel distance was 69.7 miles. Among patients who traveled > 60 miles, 41.2% bypassed a closer hospital and sought listing at a more distant hospital. In the adjusted models, when compared to patients who traveled ≤60 miles, patients who traveled >360 miles had a 27% lower subhazard ratio (SHR) for waitlist removal (SHR 0.73, 95% confidence interval [CI]: 0.60, 0.89, P = .002), 16% lower subhazard for waitlist death (SHR 0.84; 95% CI 0.73-0.95, P = .07), and 13% increased likelihood for transplant (SHR 1.13, 95% CI: 1.07, 1.20, P < .001). Many patients bypassed the nearest transplant hospital, and longer patient travel distance was associated with favorable waitlist outcomes.  相似文献   
23.
OBJECTIVE: To evaluate the role of active and passive muscle forces in the failure mechanism of stimulated muscle. DESIGN: An in vivo rabbit model. BACKGROUND: Eccentric contractions can result in a greater incidence of muscle injury. However, the relative role of the active and passive muscle force in the failure mechanism of the activated muscle is not well elucidated. METHODS: After anaesthesia, New Zealand white rabbits were fixed in a frame on a materials testing machine. The triceps surae muscle-tendon units were passively stretched to rupture with our without continuous nerve stimulation. The force and muscle length were simultaneously recorded. Active muscle force, passive muscle force, and ratio of the active to passive muscle were calculated and depicted against strain. RESULTS: The results showed that the mean maximal passive force of triceps surae muscle was 293.1 N at a strain of 38%. The mean peak active muscle force was 21.5 N at a strain of 21%. The ratio of active to passive muscle force reached its peak first, followed by the active muscle force, and then the passive muscle force. The ratio of active to passive muscle force at the peak total force was only 3.3%. CONCLUSIONS: The stimulated muscle can exert its maximal response at extreme physiological extension. Injury of the stimulated muscle is caused mainly by passive muscle force.  相似文献   
24.
The value of consolidation therapy in advanced epithelial ovarian carcinoma patients is controversial. The aim of the present study was to assess the long-term survival of patients with a pathologically confirmed complete remission who had consolidation by single-dose, whole-abdominopelvic radiotherapy. Of 96 histologically confirmed stage II-IV epithelial ovarian carcinoma patients who underwent cytoreductive surgery followed by high-dose, platin-based chemotherapy, 57 were in complete clinical remission at the end of therapy and 50 underwent a second-look laparotomy. The study group comprises 32 consecutive patients who had no pathological evidence of disease and who received 800 cGy single-dose, whole-abdominal radiotherapy by an 8 MEV linear accelerator in a single fraction. The absolute 5-year survival and the actuarial 10-year survival were 78.7 and 63.3%, respectively. The survival was significantly better in patients who had < or =2 cm residual disease at the completion of the original operation. No severe postradiation complications were encountered. Mild complications were seen in three (9.4%) patients. Our data indicate a favorable long-term survival of patients with a negative second-look laparotomy who had consolidation with single-dose, whole-abdominal radiotherapy. These results seem to suggest that a collaborative, prospective, randomized multiarm study is indicated to solve the controversial issue of consolidation therapy.  相似文献   
25.
Psychiatric epidemiology is considered one of the main scientific foundations of psychiatry. This article reviews methodological issues and major studies in psychiatric epidemiology. Methods such as measures of frequency and association are discussed. Selection, observation, and confounding, the main sources of bias in epidemiological studies, are described. Types of study designs, such as cross-sectional, cohort, and case-control, are detailed. A historical perspective of major population-based and clinical studies is presented. Major findings of the Epidemiologic Catchment Area Study and the National Comorbidity Survey are also included. Finally, future directions in the field are discussed.  相似文献   
26.
Objectives: Visual media influence the general public's perceptions and attitudes regarding people with mental conditions. This qualitative study investigates the depiction accuracy of dementia's clinical features in motion pictures.Method: Using the search terms ‘dementia’, ‘Alzheimer's disease’ and ‘senility’ movies with release dates between January 2000 and March 2012 were sought on the Internet Movie Database. Based on four selection criteria 23 movies were included. Independently, three researchers watched all movies, scored symptoms, capacities, and behaviors. Scores were discussed and refined during consensus meetings, resulting in a taxonomy of clinical features.Results: Various features are found, most often cognitive symptoms. Behavioral features are also shown – retiring behavior more than agitation – and various emotions, but physical symptoms are rarely depicted. Capacities are infrequently presented and are unrealistic in several of the movies.Conclusion: The clinical picture of dementia portrayed in fictional movies is mild and may be misleading.  相似文献   
27.
28.
Genetic associations involving both rare and common alleles have been reported for schizophrenia but there have been no systematic scans for rare recessive genotypes using fully phased trio data. Here, we use exome sequencing in 604 schizophrenia proband–parent trios to investigate the role of recessive (homozygous or compound heterozygous) nonsynonymous genotypes in the disorder. The burden of recessive genotypes was not significantly increased in probands at either a genome-wide level or in any individual gene after adjustment for multiple testing. At a system level, probands had an excess of nonsynonymous compound heterozygous genotypes (minor allele frequency, MAF ⩽1%) in voltage-gated sodium channels (VGSCs; eight in probands and none in parents, P=1.5 × 104). Previous findings of multiple de novo loss-of-function mutations in this gene family, particularly SCN2A, in autism and intellectual disability provide biological and genetic plausibility for this finding. Pointing further to the involvement of VGSCs in schizophrenia, we found that these genes were enriched for nonsynonymous mutations (MAF ⩽0.1%) in cases genotyped using an exome array, (5585 schizophrenia cases and 8103 controls), and that in the trios data, synaptic proteins interacting with VGSCs were also enriched for both compound heterozygosity (P=0.018) and de novo mutations (P=0.04). However, we were unable to replicate the specific association with compound heterozygosity at VGSCs in an independent sample of Taiwanese schizophrenia trios (N=614). We conclude that recessive genotypes do not appear to make a substantial contribution to schizophrenia at a genome-wide level. Although multiple lines of evidence, including several from this study, suggest that rare mutations in VGSCs contribute to the disorder, in the absence of replication of the original findings regarding compound heterozygosity, this conclusion requires evaluation in a larger sample of trios.  相似文献   
29.

Background

In humans, in utero exposure to ionising radiation results in an increased prevalence of neurological aberrations, such as small head size, mental retardation and decreased IQ levels. Yet, the association between early damaging events and long-term neuronal anomalies remains largely elusive.

Methods

Mice were exposed to different X-ray doses, ranging between 0.0 and 1.0 Gy, at embryonic days (E) 10, 11 or 12 and subjected to behavioural tests at 12 weeks of age. Underlying mechanisms of irradiation at E11 were further unravelled using magnetic resonance imaging (MRI) and spectroscopy, diffusion tensor imaging, gene expression profiling, histology and immunohistochemistry.

Results

Irradiation at the onset of neurogenesis elicited behavioural changes in young adult mice, dependent on the timing of exposure. As locomotor behaviour and hippocampal-dependent spatial learning and memory were most particularly affected after irradiation at E11 with 1.0 Gy, this condition was used for further mechanistic analyses, focusing on the cerebral cortex and hippocampus. A classical p53-mediated apoptotic response was found shortly after exposure. Strikingly, in the neocortex, the majority of apoptotic and microglial cells were residing in the outer layer at 24 h after irradiation, suggesting cell death occurrence in differentiating neurons rather than proliferating cells. Furthermore, total brain volume, cortical thickness and ventricle size were decreased in the irradiated embryos. At 40 weeks of age, MRI showed that the ventricles were enlarged whereas N-acetyl aspartate concentrations and functional anisotropy were reduced in the cortex of the irradiated animals, indicating a decrease in neuronal cell number and persistent neuroinflammation. Finally, in the hippocampus, we revealed a reduction in general neurogenic proliferation and in the amount of Sox2-positive precursors after radiation exposure, although only at a juvenile age.

Conclusions

Our findings provide evidence for a radiation-induced disruption of mouse brain development, resulting in behavioural differences. We propose that alterations in cortical morphology and juvenile hippocampal neurogenesis might both contribute to the observed aberrant behaviour. Furthermore, our results challenge the generally assumed view of a higher radiosensitivity in dividing cells. Overall, this study offers new insights into irradiation-dependent effects in the embryonic brain, of relevance for the neurodevelopmental and radiobiological field.

Electronic supplementary material

The online version of this article (doi:10.1186/1866-1955-7-3) contains supplementary material, which is available to authorized users.  相似文献   
30.
Among men who have sex with men (MSM), sexual compulsivity has been associated with higher frequencies of sexual behaviors that may increase risk for transmission of HIV and other sexually transmitted infections (STI). In a Midwestern region where social and community resources for MSM are relatively diffuse, the patterns of partner-seeking and sexual behavior, and their relations to sexual compulsivity, may be different than findings from most other assessments of men in large urban areas. Using a community-based participatory approach (CBPR) and a cross-sectional survey, quantitative data were collected between November 2006 and January 2007 from 504 men related to sexual compulsivity, sexual partner-seeking, and sexual behavior. We sought to explore sexual behaviors in venues where men reported meeting sexual partners, based on their level of compulsivity. Venues that could be characterized as "sexualized" were better predictors of higher sexual compulsivity scores among men than those that are "social" in nature. Men who were higher in compulsivity reported patterns of saturating sexualized venues in order to find sexual partners. Given the unique patterns of sexual partner-seeking in this area, interventions to decrease sexual risk-taking should take into account that men who have a higher propensity for sexual compulsivity are visiting multiple venues, and prevention messages need to be tailored to be consistent across these contexts. In addition, these may need to be differentially designed based on the specific environment in which they are to be delivered.  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