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   730篇
  免费   40篇
  国内免费   3篇
耳鼻咽喉   3篇
儿科学   38篇
妇产科学   4篇
基础医学   112篇
口腔科学   8篇
临床医学   59篇
内科学   109篇
皮肤病学   22篇
神经病学   47篇
特种医学   10篇
外科学   145篇
综合类   5篇
预防医学   29篇
眼科学   4篇
药学   148篇
中国医学   3篇
肿瘤学   27篇
  2022年   8篇
  2021年   13篇
  2020年   12篇
  2019年   11篇
  2018年   17篇
  2017年   9篇
  2016年   18篇
  2015年   13篇
  2014年   19篇
  2013年   38篇
  2012年   36篇
  2011年   23篇
  2010年   22篇
  2009年   19篇
  2008年   32篇
  2007年   33篇
  2006年   43篇
  2005年   35篇
  2004年   36篇
  2003年   29篇
  2002年   36篇
  2001年   39篇
  2000年   31篇
  1999年   33篇
  1998年   13篇
  1997年   8篇
  1996年   4篇
  1995年   4篇
  1994年   4篇
  1993年   4篇
  1992年   5篇
  1991年   12篇
  1990年   10篇
  1989年   6篇
  1988年   4篇
  1987年   5篇
  1986年   5篇
  1985年   5篇
  1980年   3篇
  1978年   3篇
  1977年   3篇
  1970年   3篇
  1968年   3篇
  1966年   3篇
  1963年   4篇
  1961年   4篇
  1954年   4篇
  1948年   3篇
  1947年   3篇
  1944年   3篇
排序方式: 共有773条查询结果,搜索用时 15 毫秒
81.
We retrospectively evaluated predictors of conversion to multiple sclerosis (MS) in 357 children with isolated optic neuritis (ON) as a first demyelinating event who had a median follow‐up of 4.0 years. Multiple Cox proportional‐hazards regressions revealed abnormal cranial magnet resonance imaging (cMRI; hazard ratio [HR] = 5.94, 95% confidence interval [CI] = 3.39–10.39, p < 0.001), presence of cerebrospinal fluid immunoglobulin G oligoclonal bands (OCB; HR = 3.69, 95% CI = 2.32–5.86, p < 0.001), and age (HR = 1.08 per year of age, 95% CI = 1.02–1.13, p = 0.003) as independent predictors of conversion, whereas sex and laterality (unilateral vs bilateral) had no influence. Combined cMRI and OCB positivity indicated a 26.84‐fold higher HR for developing MS compared to double negativity (95% CI = 12.26−58.74, p < 0.001). Accordingly, cerebrospinal fluid analysis may supplement cMRI to determine the risk of MS in children with isolated ON. Ann Neurol 2015;77:1076–1082  相似文献   
82.
83.
Recently we validated the donor risk index (DRI) as conducted by Feng et al. for the Eurotransplant region. Although this scoring system is a valid tool for scoring donor liver quality, for allocation purposes a scoring system tailored for the Eurotransplant region may be more appropriate. Objective of our study was to investigate various donor and transplant risk factors and design a risk model for the Eurotransplant region. This study is a database analysis of all 5939 liver transplantations from deceased donors into adult recipients from the 1st of January 2003 until the 31st of December 2007 in Eurotransplant. Data were analyzed with Kaplan–Meier and Cox regression models. From 5723 patients follow‐up data were available with a mean of 2.5 years. After multivariate analysis the DRI (p < 0.0001), latest lab GGT (p = 0.005) and rescue allocation (p = 0.007) remained significant. These factors were used to create the Eurotransplant Donor Risk Index (ET‐DRI). Concordance‐index calculation shows this ET‐DRI to have high predictive value for outcome after liver transplantation. Therefore, we advise the use of this ET‐DRI for risk indication and possibly for allocation purposes within the Eurotrans‐plant region.  相似文献   
84.
BACKGROUND/AIMS: Transplantation of primary human hepatocytes and establishment of hepatitis B virus (HBV) infection in immunodeficient urokinase plasminogen activator (uPA) transgenic mice was shown. However, the availability of usable primary human hepatocytes is very limited. Therefore, alternative and more accessible sources of hepatocytes permissive for HBV infection are highly desirable. Here we investigated the potential of primary hepatocytes from the tree shrew Tupaia belangeri that were shown to be susceptible to HBV infection. METHODS: Freshly isolated or cryopreserved primary tupaia hepatocytes were transplantated via intrasplenic injection into immunodeficient uPA/RAG-2 mice. Engrafted mice were then infected with HBV and woolly monkey (WM)-HBV positive sera. RESULTS: Extensive proliferation of xenografted cells was demonstrated by the stable production of tupaia alpha1-antitrypsin in serum and liver of transplanted mice. Quantitative PCR assays demonstrated the presence of circulating viral particles as well as intracellular viral DNA, including covalently closed circular (ccc) DNA, in transplanted mice. Viral infection could be serially passaged in mice. Furthermore, viral replication was strongly inhibited by treating mice with adefovir dipivoxil. CONCLUSIONS: uPA mice repopulated with tupaia hepatocytes represent a useful and more accessible model for HBV infection studies, including the evaluation of antiviral therapy and cccDNA.  相似文献   
85.
86.
87.
Risk factors of smoking, drug and alcohol abuse, obesity, and sedentary lifestyle were related to health problems of clients at a walk-in clinic for the homeless. The sample of 1252 clients was predominately male (91.4%) and multiethnic, with a majority (65%) age 18 to 40 years. Data on diagnoses of health-related conditions were collected from clinic charts, coded into ICD categories, analyzed for relationships of risk factors to health problems, and compared with categories of diagnoses in a matched national sample of ambulatory care visits. Findings indicate that a larger proportion of homeless suffered from health problems in 24 of 27 diagnostic categories than the nonhomeless. Most prevalent were respiratory, dermal conditions, injuries, and digestive problems, in that order. Risk factors of alcohol abuse, smoking, sedentary lifestyle, drug abuse, and obesity were predictive of health problems in 18 of the categories analyzed. The findings suggest that immediate interventions such as education and rehabilitation to reduce risk factors, and provision of facilities for personal hygiene and cleaning of clothing could reduce some of the health-related conditions in this population while longer-term solutions of housing and employment are sought. The analysis model developed here appears to be a useful way of comparing relative effects of risk factors as a basis for establishing priorities for interventions.  相似文献   
88.
89.
OBJECTIVE: This study investigated the contribution of perceptual-motor dysfunction and cognitive planning problems to the quality or speed of handwriting in children with handwriting problems (HWP). METHOD: Twenty-nine children with HWP and 20 classroom peers attending regular schools (grade 2 and grade 3) were tested with regard to visual perception, visual-motor integration, fine motor coordination, and cognitive planning abilities. RESULTS: The HWP group scored significantly lower on visual perception, visual-motor integration, fine motor coordination, and cognitive planning in comparison with classroom controls. Regression analyses showed that visual-motor integration was the only significant predictor for quality of handwriting in the HWP group, whereas fine motor coordination (i.e., unimanual dexterity) was the only significant predictor of quality of handwriting in the control group. CONCLUSIONS: Results suggest that two different mechanisms underlie the quality of handwriting in children with and without handwriting problems. Poor quality of handwriting of children with HWP seems particularly related to a deficiency in visual-motor integration.  相似文献   
90.
A comparison of the bimolecular rate constants (ki) for inhibition of electric eel acetylcholinesterase (AChE) by the oxono (i.e., P=O) and thiono (i.e., P=S) analogues of parathion, methylparathion, leptophos, fonofos, sarin, and soman revealed that the oxono/thiono ratios of ki values varied from 14 for soman to 1240 for parathion. Analysis of the relative importance of the dissociation equilibrium constant and the phosphorylation rate constant in producing this variation in ki values indicated that the oxono analogues and the phosphorylation rate constant values that varied in a narrow range from 8- to 14-fold greater than their thiono counterparts, while the oxono/thiono ratios for dissociation constants varied widely from 1 for soman to 82 for fonofos. The lower affinities of thiono analogues for AChE probably resulted from differences in the hydrophobic binding of oxono and thiono analogues to the active site of AChE, inasmuch as the hydrophobicities (i.e., octanol/water partition coefficients) of thiono organophosphorus compounds were much greater than the hydrophobicities of their oxono analogues. Quantitative structure--activity analysis indicated that the hydrophobic effects of oxono and thiono moieties correlated with log ki for AChE inhibition to a greater extent (r2 = 0.79) than their electronic effects (r2 less than or equal to 0.48). These observations suggest that the differences in hydrophobicity of oxono and thiono analogues of organophosphorus compounds may be as important as their electronic differences in determining their effectiveness as AChE inhibitors.  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