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   3560篇
  免费   299篇
  国内免费   7篇
耳鼻咽喉   45篇
儿科学   117篇
妇产科学   54篇
基础医学   565篇
口腔科学   41篇
临床医学   438篇
内科学   668篇
皮肤病学   66篇
神经病学   312篇
特种医学   74篇
外科学   483篇
综合类   26篇
一般理论   2篇
预防医学   436篇
眼科学   103篇
药学   209篇
中国医学   7篇
肿瘤学   220篇
  2023年   43篇
  2022年   63篇
  2021年   153篇
  2020年   100篇
  2019年   149篇
  2018年   146篇
  2017年   107篇
  2016年   102篇
  2015年   115篇
  2014年   177篇
  2013年   220篇
  2012年   318篇
  2011年   300篇
  2010年   148篇
  2009年   117篇
  2008年   180篇
  2007年   192篇
  2006年   164篇
  2005年   140篇
  2004年   128篇
  2003年   114篇
  2002年   116篇
  2001年   50篇
  2000年   65篇
  1999年   36篇
  1998年   28篇
  1997年   22篇
  1996年   15篇
  1995年   17篇
  1994年   12篇
  1993年   10篇
  1992年   32篇
  1991年   16篇
  1990年   11篇
  1989年   21篇
  1988年   27篇
  1987年   19篇
  1986年   14篇
  1985年   27篇
  1984年   14篇
  1983年   16篇
  1982年   10篇
  1981年   11篇
  1979年   15篇
  1977年   6篇
  1976年   8篇
  1974年   11篇
  1973年   7篇
  1969年   6篇
  1966年   6篇
排序方式: 共有3866条查询结果,搜索用时 31 毫秒
71.
72.
AIDS and Behavior - A robust evidence-base describes the beneficial association between opioid agonist therapy (OAT) and HIV-related outcomes among people living with HIV and opioid use disorder....  相似文献   
73.
Delineation of neural mechanisms involved in reflex cough is essential for understanding its many physiological and clinical complexities, and the development of more desirable antitussive agents. Brainstem networks that generate and modulate the breathing pattern are also involved in producing the motor patterns during reflex cough. Neurones of the ventrolateral medulla respiratory pattern generator mutually interact with neural networks in the pons, medulla and cerebellum to form a larger dynamic network. This paper discusses evidence from our laboratory and others supporting the involvement of the nucleus tractus solitarii, midline raphe nuclei and lateral tegmental field in the medulla, and the pontine respiratory group and cerebellum in the production of reflex cough. Gaps in our knowledge are identified to stimulate further research on this complicated issue.  相似文献   
74.
OBJECTIVE: To examine the association of elderly onset rheumatoid arthritis (RA) with health related quality of life in a population based cohort of older women. METHODS: A nested case-control study of elderly onset RA within the Iowa Women's Health Study (IWHS), a prospective cohort established in 1986 of 41,000 women aged 55 to 69 years. A supplemental questionnaire was mailed to 122 RA cases and 1132 frequency matched controls from the cohort. We used unconditional logistic regression and linear regression to examine the association of elderly onset RA with self-reported measures of functional disability and quality of life. RESULTS: Elderly onset RA was associated with a 6-fold risk (OR 6.0, 95% CI 3.6-10.1) of significant functional disability (Health Assessment Questionnaire score (3) 1). Similarly, elderly onset RA was significantly associated with lower physical component scores of the Medical Outcome Study Short Form-12 (37.2 +/- 10.9 vs 43.6 +/- 11.6; p < 0.001). CONCLUSION: Among a community based cohort, elderly onset RA was strongly associated with functional disability and reduced quality of life. These associations were independent of other age associated factors including depression, recent fracture, and multiple comorbidities.  相似文献   
75.
Within a 2.5-year period between 1985 and 1988, long coronary arteriotomy, endarterectomy and reconstruction (principally left anterior descending artery) and multiple bypass grafting (mean graft rate was 9) were performed in 130 of 329 patients (40%) with severe diffuse coronary artery disease to ensure complete myocardial revascularization. Ninety-two percent of the patients who underwent exercise testing had abnormal (greater than 1 mm ST) depression and/or positive results on scintigraphy. Long coronary arteriotomy (5 to 12 cm), endarterectomy and reconstruction of the left anterior descending artery and its branches, were performed in 121 patients; of the left circumflex artery and its branches in 13 patients; and of the right coronary artery and its branches beyond the crux in 18 patients. Single endarterectomy and reconstruction was performed in 109 patients, double in 20 and triple in 1. The operative mortality was 2.3% and the perioperative infarction was 1.5%. Twenty-four patients (among them 38% who had undergone greater than 1 previous bypass operation) were randomly selected and studied within 20 days after surgery. This group comprised a total of 69 coronary conduits of which 68 (99%) were patent, and a total of 206 coronary anastomoses of which 202 (98%) were patent. Thirty-two of 33 conduits (97%) to endarterectomized and reconstructed arteries were patent. One hundred and twenty-six of 127 patients were followed up for a mean of 20 months; 120 of the 121 patients (99%) were in angina class I by Canadian Cardiovascular Society classification, and 63 of 71 patients (89%) had a normal treadmill exercise stress test.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
76.
OBJECTIVE: Vitamin D is a potent regulator of calcium homeostasis and may have immunomodulatory effects. The influence of vitamin D on human autoimmune disease has not been well defined. The purpose of this study was to evaluate the association of dietary and supplemental vitamin D intake with rheumatoid arthritis (RA) incidence. METHODS: We analyzed data from a prospective cohort study of 29,368 women of ages 55-69 years without a history of RA at study baseline in 1986. Diet was ascertained using a self-administered, 127-item validated food frequency questionnaire that included supplemental vitamin D use. Risk ratios (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards regression, adjusting for potential confounders. RESULTS: Through 11 years of followup, 152 cases of RA were validated against medical records. Greater intake (highest versus lowest tertile) of vitamin D was inversely associated with risk of RA (RR 0.67, 95% CI 0.44-1.00, P for trend = 0.05). Inverse associations were apparent for both dietary (RR 0.72, 95% CI 0.46-1.14, P for trend = 0.16) and supplemental (RR 0.66, 95% CI 0.43-1.00, P for trend = 0.03) vitamin D. No individual food item high in vitamin D content and/or calcium was strongly associated with RA risk, but a composite measure of milk products was suggestive of an inverse association with risk of RA (RR 0.66, 95% CI 0.42-1.01, P for trend = 0.06). CONCLUSION: Greater intake of vitamin D may be associated with a lower risk of RA in older women, although this finding is hypothesis generating.  相似文献   
77.
Transforming growth factor-β (TGFβ) is a secreted cytokine implicated as a factor in cancer cell migration and invasion. Previous studies have indicated that TGFβ isoforms may exert differential effects on cancer cells during different stages of the disease, however very little is known about the expression patterns and activity of the three isoforms in prostate cancer. Non-traditional signaling pathways including the PI3-Kinase have been associated with TGFβ-mediated effects on cancer cell invasion. In the present study, we have carried out expression analysis of TGFβ isoforms and signaling components in cell line models representing different stages of prostate cancer and studied the differential effects of specific isoforms on migratory and invasive behavior and induction of the PI3-kinase pathway. TGFβ1 and TGFβ3 were expressed in all cell lines, with TGFβ3 expression increasing in metastatic cell lines. Both TGFβ1 and TGFβ3 induced motility and invasive behavior in PC3 cells, however, TGFβ3 was significantly more potent than TGFβ1. TGFβRI and Smad3 inhibitors blocked TGFβ1 and TGFβ3 induced motility and invasion. TGFβ3 caused a significant increase in pAKTser473 in PC3 cells and PI3-kinase inhibitor LY294002 blocked TGFβ3 induced migration, invasion and phosphorylation of AKT. Both TGFβRI and Smad3 inhibitors blocked TGFβ3 induced pAKTser473. Based on these results, we conclude that TGFβ3 is expressed in metastatic prostate cancer cell lines and is involved in induction of invasive behavior in these cells. Furthermore, these effects of TGFβ3 are TGFβRI and Smad3 dependent and mediated via the PI3-kinase pathway.  相似文献   
78.
79.
80.
Collection of saliva for DNA extraction has created new opportunities to recruit participants from the community for genetic association studies. However, sample return rates are variable. No prior study has specifically addressed how study design impacts sample return. Using data from three large‐scale genetic association studies we compared recruitment strategy and sample return rates. We found highly significant differences in sample return rates between the studies. In studies that recruited retrospectively, overall returns were much lower from families with a self‐limiting condition who provided samples at a research centre or home visit, than adult elderly individuals with a chronic disease who provided samples by post (59% vs. 84%). Prospective recruitment was associated with high agreement to participate (72%), but subsequent low return of actual saliva samples (42%). A telephone call had marginal effect on recruitment in a retrospective family study, but significantly improved returns in a prospective family study. We found no effect upon DNA yield comparing observed versus unobserved sample collection, or between male and female adult participants. Overall, study design significantly impacts upon response rates for genetic association studies recruiting from the community. Our findings will help researchers in constructing and costing a recruitment protocol.  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