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   426篇
  免费   19篇
  国内免费   1篇
耳鼻咽喉   7篇
儿科学   8篇
妇产科学   1篇
基础医学   58篇
口腔科学   9篇
临床医学   29篇
内科学   37篇
神经病学   34篇
特种医学   36篇
外科学   59篇
综合类   32篇
预防医学   65篇
眼科学   1篇
药学   67篇
中国医学   1篇
肿瘤学   2篇
  2025年   2篇
  2024年   13篇
  2023年   11篇
  2022年   15篇
  2021年   19篇
  2020年   24篇
  2019年   15篇
  2018年   9篇
  2017年   11篇
  2016年   14篇
  2015年   20篇
  2014年   19篇
  2013年   35篇
  2012年   8篇
  2011年   23篇
  2010年   9篇
  2009年   17篇
  2008年   24篇
  2007年   17篇
  2006年   9篇
  2005年   19篇
  2004年   7篇
  2003年   5篇
  2002年   10篇
  2001年   6篇
  2000年   7篇
  1999年   7篇
  1998年   9篇
  1997年   4篇
  1996年   1篇
  1995年   8篇
  1994年   1篇
  1993年   7篇
  1992年   3篇
  1991年   7篇
  1990年   3篇
  1989年   2篇
  1988年   4篇
  1987年   2篇
  1986年   6篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1982年   2篇
  1980年   4篇
  1979年   1篇
  1978年   1篇
排序方式: 共有446条查询结果,搜索用时 9 毫秒
101.
         下载免费PDF全文
In this paper, we derive the frozen Gaussian approximation (FGA) for computing the solution to the Dirac equation in curved space in the semi-classical regime.The latter equation is used in particular for modeling electronic scattering on strainedgraphene surfaces. We present numerical comparisons of the Dirac solutions on curvedand flat spaces, illustrating the focusing effect of graphene surfaces, as well as qualitative comparisons with a tight-binding model. A CPU-time comparison shows thatFGA becomes more efficient than an IMEX pseudospectral method when the semiclassical parameter is small.  相似文献   
102.
         下载免费PDF全文
A second order accurate in time, finite difference numerical scheme is proposed and analyzed for the Cahn-Hilliard-Navier-Stokes system, with logarithmicFlory-Huggins energy potential. In the numerical approximation to the chemical potential, a modified Crank-Nicolson approximation is applied to the singular logarithmic nonlinear term, while the expansive term is updated by an explicit second orderAdams-Bashforth extrapolation, and an alternate temporal stencil is used for the surface diffusion term. Moreover, a nonlinear artificial regularization term is included inthe chemical potential approximation, which ensures the positivity-preserving property for the logarithmic arguments, i.e., the numerical value of the phase variable isalways between −1 and 1 at a point-wise level. Meanwhile, the convective term in thephase field evolutionary equation is updated in a semi-implicit way, with second orderaccurate temporal approximation. The fluid momentum equation is also computed bya semi-implicit algorithm. The unique solvability and the positivity-preserving property of the second order scheme is proved, accomplished by an iteration process. Amodified total energy stability of the second order scheme is also derived. Some numerical results are presented to demonstrate the accuracy and the robust performanceof the proposed second order scheme.  相似文献   
103.
    
  1. Download : Download high-res image (365KB)
  2. Download : Download full-size image
  相似文献   
104.
《Annals of epidemiology》2014,24(4):291-296
PurposeLow-to-moderate alcohol consumption is associated with decreased mortality. However, many aspects of this association are still debated. Our aim was to complement available information by conducting a dose-response analysis of the association between alcohol consumption and survival time.MethodsIn a Swedish population-based cohort of 67,706 middle-aged and elderly men and women, frequency and amount of drinking were assessed through a self-administrated questionnaire. During 15 years of follow-up, 13,323 participants died. Differences in survival (10th percentile differences, PDs) according to levels of alcohol consumption were estimated using Laplace regression.ResultsWe found evidence of nonlinearity between alcohol consumption and survival. Among women, we observed a rapid increase in survival up to 6 g/d of alcohol consumption (0.5 drinks/d) where survival was 17 months longer (PD = 17 months, 95% confidence interval, 10 to 24). After this peak, higher alcohol consumption was progressively associated with shorter survival. Among men, survival improved up to 15 g/d (1.5 drinks/d) where we observed a PD of 15 months (95% confidence interval, 8 to 22).ConclusionsLow alcohol consumption was associated with improved survival up to 1.5 years for women with an average consumption of 0.5 drinks per day and to 1.3 years for men with an average consumption of 1.5 drinks per day.  相似文献   
105.
赵众  顾幸生 《医学教育探索》1998,(2):192-197234
利用正交小波变换的时频分析及多工尺度特点,基于函数逼近以及函数奇性分析的原理,提出了化工生产过程数据压缩及害变信号检测算法,理论分析和仿真研究证实了所提算法的可行性和有效性。  相似文献   
106.
In this study, the nanosphere lithography (NSL) method was used to fabricate hybrid Au-Ag triangular periodic nanoparticle arrays. The Au-Ag triangular periodic arrays were grown on different substrates, and the effect of the refractive index of substrates on fabrication and optical properties was systematically investigated. At first, the optical spectrum was simulated by the discrete dipole approximation (DDA) numerical method as a function of refractive indexes of substrates and mediums. Simulation results showed that as the substrates had the refractive indexes of 1.43 (quartz) and 1.68 (SF5 glass), the nanoparticle arrays would have better refractive index sensitivity (RIS) and figure of merit (FOM). Simulation results also showed that the peak wavelength of the extinction spectra had a red shift when the medium’s refractive index n increased. The experimental results also demonstrated that when refractive indexes of substrates were 1.43 and 1.68, the nanoparticle arrays and substrate had better adhesive ability. Meanwhile, we found the nanoparticles formed a large-scale monolayer array with the hexagonally close-packed structure. Finally, the hybrid Au-Ag triangular nanoparticle arrays were fabricated on quartz and SF5 glass substrates and their experiment extinction spectra were compared with the simulated results.  相似文献   
107.
In this sequel, to an earlier article, we discuss the laws of Mechanics, Thermodynamics and Vectors as they apply to soft and bony tissues. These include the Laplace’s Law as applied to colonic perforation, compression therapy, parturition, variceal rupture, disc herniations etc. The Pascal’s Law finds use in hernia repair and the Heimlich maneuver. Trigonometrically derived components of forces, acting after suturing, show ways to reduce cut-through; the thickness and the bite of suture determines the extent of tissue reaction. The heating effect of current explains the optimum gap between the prongs of a bipolar cautery and the use of law of transfer of heat in determining relation between healthy wound healing and ambient temperature.  相似文献   
108.
In nonlinear mixed-effects models, estimation methods based on a linearization of the likelihood are widely used although they have several methodological drawbacks. Kuhn and Lavielle (Comput. Statist. Data Anal. 49:1020–1038 (2005)) developed an estimation method which combines the SAEM (Stochastic Approximation EM) algorithm, with a MCMC (Markov Chain Monte Carlo) procedure for maximum likelihood estimation in nonlinear mixed-effects models without linearization. This method is implemented in the Matlab software MONOLIX which is available at http://www.math.u-psud.fr/~lavielle/monolix/logiciels. In this paper we apply MONOLIX to the analysis of the pharmacokinetics of saquinavir, a protease inhibitor, from concentrations measured after single dose administration in 100 HIV patients, some with advance disease. We also illustrate how to use MONOLIX to build the covariate model using the Bayesian Information Criterion. Saquinavir oral clearance (CL/F) was estimated to be 1.26 L/h and to increase with body mass index, the inter-patient variability for CL/F being 120%. Several methodological developments are ongoing to extend SAEM which is a very promising estimation method for population pharmacockinetic/pharmacodynamic analyses.  相似文献   
109.
AIM: To study the relationship between quantitative structure and pharmacokinetics (QSPkR) of fluoroquinolone antibacterials. METHODS: The pharmacokinetic (PK) parameters of oral fluoroquinolones were collected from the litera- ture. These pharmacokinetic data were averaged, 19 compounds were used as the training set, and 3 served as the test set. Genetic function approximation (GFA) module of Cerius2 software was used in QSPkR analysis. RESULTS: A small volume and large polarizability and surface area of substituents at C-7 contribute to a large area under the curve (AUC) for fluoroquinolones. Large polarizability and small volume of substituents at N-1 contribute to a long half life elimination. CONCLUSION: QSPkR models can contribute to some fluoroquinolones antibacterials with excellent pharmacokinetic properties.  相似文献   
110.
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