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   4798篇
  免费   352篇
  国内免费   12篇
耳鼻咽喉   62篇
儿科学   192篇
妇产科学   111篇
基础医学   582篇
口腔科学   177篇
临床医学   543篇
内科学   829篇
皮肤病学   84篇
神经病学   510篇
特种医学   196篇
外科学   541篇
综合类   87篇
一般理论   5篇
预防医学   554篇
眼科学   109篇
药学   290篇
  2篇
中国医学   6篇
肿瘤学   282篇
  2024年   20篇
  2023年   58篇
  2022年   101篇
  2021年   174篇
  2020年   100篇
  2019年   162篇
  2018年   184篇
  2017年   153篇
  2016年   136篇
  2015年   155篇
  2014年   168篇
  2013年   251篇
  2012年   337篇
  2011年   364篇
  2010年   221篇
  2009年   135篇
  2008年   249篇
  2007年   211篇
  2006年   167篇
  2005年   191篇
  2004年   154篇
  2003年   115篇
  2002年   118篇
  2001年   58篇
  2000年   68篇
  1999年   62篇
  1998年   42篇
  1997年   58篇
  1996年   44篇
  1995年   42篇
  1994年   37篇
  1993年   51篇
  1992年   41篇
  1991年   44篇
  1990年   50篇
  1989年   57篇
  1988年   58篇
  1987年   46篇
  1986年   58篇
  1985年   39篇
  1984年   24篇
  1983年   25篇
  1981年   25篇
  1980年   16篇
  1979年   36篇
  1978年   30篇
  1977年   21篇
  1976年   21篇
  1974年   15篇
  1969年   18篇
排序方式: 共有5162条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
95.
96.
Introduction: Common yew (Taxus baccata) is a common decorative evergreen shrub with potentially fatal toxicity hallmarked by seizure, arrhythmia and cardiovascular collapse if ingested. Taxine B has been identified as one of the most cardiotoxic taxine alkaloids in Taxus spp, and another alkaloid, 3,5-dimethoxyphenol (3,5-DMP), is used as a marker of ingestion. We present a fatal case of ingestion of yew with perimortem serum and gastric taxine B, and 3,5-DMP concentrations.

Case presentation: A 22-year-old woman was brought to the emergency department (ED) from a nearby botanical garden after she was found apneic and pulseless after a witnessed generalized tonic clonic seizure. The patient was found to have a wide complex rhythm with persistent cardiovascular collapse and expired despite maximal supportive care in the ED. A baggie of plant material was found on the patient, identified as Taxus baccata. Perimortem serum and gastric samples were analyzed to quantify serum and gastric taxine B and 3,5-DMP concentrations.

Results: Perimortem serum showed a 3,5-DMP concentration of 86.9 ng/mL, and taxine B of 80.9 ug/mL.

Conclusion: We report a perimortem serum and gastric taxine B and 3,5-DMP concentrations in a fatal case of T. baccata toxicity.  相似文献   

97.
Lifelong cognitive stimulation is associated with a lower risk of Alzheimer's disease (AD), but causality is difficult to prove. We therefore sought to investigate the preventative potential of environmental enrichment (EE) using mice expressing both human mutant presenilin-1 and the amyloid precursor protein (PS1/PDAPP). At weaning, mice were placed into either an enriched or standard housing environment. Behavioral testing at 4.5-6 months showed that environmentally enriched PS1/PDAPP mice outperformed mice in standard housing, and were behaviorally indistinguishable from non-transgenic mice across multiple cognitive domains. PS1/PDAPP mice exposed to both environmental enrichment and behavioral testing, but not to EE alone, showed 50% less brain beta-amyloid without improved dendritic morphology. Microarray analysis revealed large enrichment-induced changes in hippocampal expression of genes/proteins related to Abeta sequestration and synaptic plasticity. These results indicate that EE protects against cognitive impairment in AD transgenic mice through a dual mechanism, including both amyloid dependent and independent mechanisms.  相似文献   
98.
Although some previous studies have reported that genetic and immunologic factors play important roles in the pathogenesis of Kawasaki disease (KD), the etiologic factors of this enigmatic pediatric disease are still poorly understood. The purpose of this study was to investigate whether polymorphisms of the human leukocyte antigen DRB1 (HLA-DRB1) gene are associated with KD and the development of coronary artery lesions (CAL) in Taiwanese children. Genomic DNA was extracted from whole blood samples from 145 children with KD and 331 healthy controls. The HLA-DRB1 gene was genotyped by polymerase chain reaction (PCR) and sequence-based typing assays. We found that the distribution of HLA-DRB1 allele families and alleles in children with KD did not differ from that in healthy controls. Stratified analysis did not demonstrate any association between particular HLA-DRB1 allele families or alleles and the development of CAL in children with KD. These findings suggest that susceptibility to KD and CAL is not associated with the HLA-DRB1 gene in a Taiwanese population. If immunogenetic determinants are involved in this disease and its complications in Taiwanese children, they must involve genes other than HLA-DRB1.  相似文献   
99.

Background

In 2016, the US Department of Agriculture (USDA)’s Supplemental Nutrition Assistance Program (SNAP) Retailer Rule proposed several changes for SNAP-authorized retailers, including: requiring retailers to have at least 85% of their food sales come from items that are not cooked or heated on site before or after purchase; requiring stores to stock seven varieties of qualifying foods from four staple food groups; requiring stores to carry perishable foods in three of the four staple groups; requiring stores to carry six units of qualifying foods at all times (depth of stock); disqualifying multiple ingredient foods and accessory foods from counting toward depth of stock requirements.

Objectives

To better understand arguments used to support or oppose the USDA’s proposed rule that all SNAP-authorized retailers carry more nutritious foods.

Design

We conducted a qualitative content analysis of a random sample of public comments posted to the US Federal Register (a publicly available database) in response to the USDA’s proposed rule.

Participants/setting

A random sample of 20% of all public comments submitted by individuals and organizations to the US Federal Register were analyzed (n=303) for this study.

Results

Three main themes were discussed: 1) arguments used in opposition to the rule; 2) arguments used in support of the rule; and 3) facilitators to assist stores in implementing the rule. Some of the subthemes included focusing on definitions used in the rule, reduced food access caused by stores leaving the SNAP program, lack of space and equipment for healthy foods, and the potential for increasing healthy food access.

Conclusions

Nutrition and dietetics practitioners may be tasked with working with stores to implement healthy changes. Nutrition and dietetics practitioners must understand the role that the USDA has in food policy. In addition, understanding how federal food policy influences the environments in which dietetics professionals’ clients are making food choices is important.  相似文献   
100.
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