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   1130篇
  免费   94篇
  国内免费   7篇
耳鼻咽喉   9篇
儿科学   21篇
妇产科学   40篇
基础医学   138篇
口腔科学   104篇
临床医学   126篇
内科学   249篇
皮肤病学   31篇
神经病学   69篇
特种医学   23篇
外科学   90篇
综合类   26篇
一般理论   1篇
预防医学   84篇
眼科学   38篇
药学   91篇
中国医学   15篇
肿瘤学   76篇
  2024年   2篇
  2023年   28篇
  2022年   72篇
  2021年   106篇
  2020年   54篇
  2019年   89篇
  2018年   70篇
  2017年   59篇
  2016年   67篇
  2015年   49篇
  2014年   68篇
  2013年   80篇
  2012年   95篇
  2011年   78篇
  2010年   34篇
  2009年   29篇
  2008年   56篇
  2007年   56篇
  2006年   39篇
  2005年   31篇
  2004年   21篇
  2003年   14篇
  2002年   19篇
  2001年   4篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
排序方式: 共有1231条查询结果,搜索用时 15 毫秒
991.
992.
Acrylamide is a chemical found in starchy foods that have been cooked at high temperatures. These include crisps, chips, bread and crisp breads. It was first discovered by scientists in Sweden in 2002. The Objective of this study is to determine the level of acrylamide in popular Iranian brands of potato crisps and corn products, produced by domestic food industrial factories. For this reason 7 brands of potato and 8 brands of corn products (10 each) were collected, crashed and after preparing the extracts of each sample, using LC–MS–MS spectrometry for measuring acrylamide amount. Results showed that in different brands of potato and corn products there were different amounts (244–1688 μg/kg) and (<30–410 μg/kg) of acrylamide, respectively. As acrylamide is a dangerous toxin for human health, so it needs to reduce the level of acrylamide in these products that are used extensively by people specially children.  相似文献   
993.
Association between attention deficit hyperactivity disorder (ADHD) and the 10-repeat allele of a polymorphism (a 40 bp variable number of tandem repeats) in the dopamine transporter gene (DAT1) has been reported by several groups. In this study, we examined whether either allele of the DAT1 core promoter -67 functional polymorphism is associated with ADHD in a case/control study. The allele and genotype frequencies of the polymorphism were studied in 110 patients and 120 controls, which were matched on the basis of sex, age and ethnicity. The genotype frequencies in the patients group were as follows: AA 19.2%; AT 65.2%; TT 15.4% vs. the genotype frequencies in the control group: AA 47.5%; AT 43.3%; TT 9.2% [chi2=20.73, df=2, P相似文献   
994.
Reversed-phase preparative high-performance liquid chromatography (HPLC) of the methanol extract of the aerial parts of Euphorbia petiolata Banks & Soland, an endemic Iranian medicinal plant, yielded ten free radical scavengers including eight flavonoid glycosides myricetin 3-O-glucoside (1), kaempferol 3-O-(2-O-galloyl)-glucoside (2), myricetin 3-O-rhamnoside (3), quercetin 3-O-glucoside (4), kaempferol 3-O-glucoside (5), quercetin 3-O-rhamnoside (6), kaempferol 3-O-rhamnoside (7), and quercetin 3-O-rutinoside (10), a coumarin esculetin (8) and a phenylpropanoid 2-hydroxydihydrocinnamic acid (9). The structures of these compounds were elucidated conclusively by spectroscopic means and also by direct comparison of their spectroscopic data with respective published data. The free radical scavenging properties of these compounds were assessed by the 2,2-diphenyl-1-picrylhydrazyl assay.  相似文献   
995.
Purpose: Cone-rod dystrophy (CRD) is an inherited retinal dystrophy that is transmitted via different modes of inheritance. Mutations in more than 30 genes have been identified to cause the disease. We aimed to investigate the genetic agents of two unrelated cone-rod dystrophy affected Iranian families with autosomal recessive inheritance patterns.

Methods: Whole-exome sequencing (WES) was performed for identification of the disease-causing mutations in the probands of both families. The candidate mutations were further confirmed by Sanger sequencing. Samples from five available members of each family were then sequenced for the mutations present in the probands. Comprehensive ocular examinations for all members of the families carrying the mutations were completed by ophthalmologists.

Results: We identified a novel premature stop codon c.310C>T in CRX gene in heterozygote form in two symptomatic and two non-symptomatic members of one family (family-A), and a known CRX mutation c.122G>A in homozygote form in another (family B). c.122G>A has been reported to cause late-onset autosomal dominant form of the disease in previous studies. However, the middle-aged heterozygous carriers of the mutation in this family showed normal phenotype.

Conclusion: The CRX gene has been previously linked to the autosomal dominant form of cone-rod dystrophy. We report incomplete penetrance of CRX gene for autosomal dominant form of the disease. Incomplete penetrance of the mutations may be partly caused by the influence of other genes in the complex genetic network underlying retinal regulation.  相似文献   

996.
997.
998.
999.

Background  

Infectious bursal disease (IBD) results in economic loss due to mortality, reduction in production efficiency and increasing the usage of antibiotics. This study was carried out to investigate the modulatory roles of dietary n-3 polyunsaturated fatty acids (PUFA) enrichment in immune response and performance of IBD challenged broiler chickens.  相似文献   
1000.
There have been attempts to find new approaches to the treatment of multivessel coronary artery disease without increasing adverse events. Deployment of drug-eluting stents (DES) for complex lesions and bare-metal stents (BMS) for simpler lesions, although already in wide use, has not been well supported by clinical study.A cohort of 1,658 patients who underwent multivessel percutaneous coronary intervention from March 2003 through June 2011 was studied for 1 year. These patients were divided into 3 groups: BMS only (599 patients); DES only (481 patients); and hybrid stenting (578 patients). Baseline characteristics were similar except for hyperlipidemia and moderate-to-severe mitral regurgitation, which were more frequent in the DES and hybrid groups, respectively. Lesion characteristics were more complex in the DES group, compared with the other groups: more B2/C type lesions, longer stents, and smaller reference-vessel diameters (P <0.001). The rates of major adverse cardiac events (MACE) at 1 year were similar between the groups (BMS=5.2%, hybrid=3.9%, and DES=3.4%; P=0.248). Subgroup analysis yielded no differences in death, nonfatal myocardial infarction, target-vessel revascularization, or target-lesion revascularization. On multivariable analysis, the strongest predictors of 1-year MACE were percutaneous intervention complicated by dissection, renal failure, left ventricular ejection fraction below 0.40, mean lesion length, reference vessel diameter, and percutaneous intervention on the left circumflex coronary artery. The latter two had inverse relationships with MACE.In conclusion, implanting the DES for more complex lesions and the BMS for simpler lesions seems more sensible than the exclusive use of the DES or the BMS.  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