全文获取类型
收费全文 | 239篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
管理学 | 14篇 |
人口学 | 8篇 |
丛书文集 | 14篇 |
理论方法论 | 3篇 |
综合类 | 110篇 |
社会学 | 20篇 |
统计学 | 78篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 1篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 16篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 7篇 |
2013年 | 23篇 |
2012年 | 22篇 |
2011年 | 14篇 |
2010年 | 16篇 |
2009年 | 10篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 16篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 14篇 |
2002年 | 5篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1989年 | 1篇 |
排序方式: 共有247条查询结果,搜索用时 15 毫秒
101.
Tatjana Pavlenko Anders Björkström Annika Tillander 《Journal of applied statistics》2012,39(8):1643-1666
Recent work has shown that the Lasso-based regularization is very useful for estimating the high-dimensional inverse covariance matrix. A particularly useful scheme is based on penalizing the ?1 norm of the off-diagonal elements to encourage sparsity. We embed this type of regularization into high-dimensional classification. A two-stage estimation procedure is proposed which first recovers structural zeros of the inverse covariance matrix and then enforces block sparsity by moving non-zeros closer to the main diagonal. We show that the block-diagonal approximation of the inverse covariance matrix leads to an additive classifier, and demonstrate that accounting for the structure can yield better performance accuracy. Effect of the block size on classification is explored, and a class of asymptotically equivalent structure approximations in a high-dimensional setting is specified. We suggest a variable selection at the block level and investigate properties of this procedure in growing dimension asymptotics. We present a consistency result on the feature selection procedure, establish asymptotic lower an upper bounds for the fraction of separative blocks and specify constraints under which the reliable classification with block-wise feature selection can be performed. The relevance and benefits of the proposed approach are illustrated on both simulated and real data. 相似文献
102.
103.
针对目前电子电器类产品的微小螺钉装配时存在装配精度和速度上的不足,提出一种新型微小螺钉输送和拧紧
装置,设计了输送和拧紧装置的组成结构,介绍了装置中主要部件的工作原理,并分析了输送过程中输送轨道的倾斜角
度和输送管道的弯曲程度,采用机械振动和气动传输相结合以实现微小螺钉的排序和输送。该装置可以实现微小螺钉
装配的自动化,与传统的手工装配或半自动化装配相比,具有工作效率高、产品装配质量高和装配成本低等特点,主要用
于工业生产流水线上微小螺钉的自动化装配过程中。 相似文献
104.
根据电火花加工的动作特点,对已有的PMLSM 电机的伺服驱动器进行二次开发,即利用MSComm通信控件对伺服驱动器进行控制,同时开发了控制界面。利用开发的系统进行了试运行,并对永磁直线同步电动机(PMLSM )直线驱动装置进行了定位精度和重复定位精度测试,结果表明PMLSM直接驱动具有非常高的定位精度与重复定位精度,最后分析了影响精度指标的原因及改进方法。 相似文献
105.
对提高学术期刊论文标题英译质量的思考 总被引:1,自引:0,他引:1
文章从介词的使用、英汉差异、专业术语的选择和修辞手段的运用等四个方面,分析了学术期刊论文标题英语翻译中存在的一些主要问题,并从英译的准确性、标题的简洁性、译文的传意性、表达的生动性等角度探讨了提高期刊论文标题英译质量的途径. 相似文献
106.
提高紫外分光光度法测定水中总氮方法精确度的研究 总被引:7,自引:0,他引:7
探讨了用紫外分光光度法测定水中总氮时,试剂质量、配制方法、消化温度与时间、冷却时间、所用水与玻璃器皿的纯净度等对测定结果的影响. 相似文献
107.
利用一阶微商和二阶微商的四阶紧致差分逼近公式,推导出了数值求解一维扩散方程的两种新的高精度隐式紧致差分格式,其截断误差分别为O(τ^2 h^4)和O(τ^4 h^4).通过Fourier分析方法证明了格式O(τ^2 h^4)是无条件稳定的,而格式O(r^4 h^4)是无条件不稳定的.并且由于每一时间层上只用到了3个网格点,所以差分方程可采用追赶法直接进行求解. 相似文献
108.
Yaeji Lim 《Pharmaceutical statistics》2020,19(1):59-70
In this paper, we provide a method for constructing confidence interval for accuracy in correlated observations, where one sample of patients is being rated by two or more diagnostic tests. Confidence intervals for other measures of diagnostic tests, such as sensitivity, specificity, positive predictive value, and negative predictive value, have already been developed for clustered or correlated observations using the generalized estimating equations (GEE) method. Here, we use the GEE and delta‐method to construct confidence intervals for accuracy, the proportion of patients who are correctly classified. Simulation results verify that the estimated confidence intervals exhibit consistent/appropriate coverage rates. 相似文献
109.
《Journal of Statistical Computation and Simulation》2012,82(10):1131-1150
Multivariate hypothesis testing in studies of vegetation is likely to be hindered by unrealistic assumptions when based on conventional statistical methods. This can be overcome by randomization tests. In this paper, the accuracy and power of a MANOVA randomization test are evaluated for one and two factors with interaction with simulated data from three distributions. The randomization test is based on the partitioning of sum of squares computed from Euclidean distances. In one-factor designs, sample size and variance inequality were evaluated. The results showed a high level of accuracy. The power curve was higher with normal distribution, lower with uniform, intermediate with lognormal and was sensitive to variance inequality. In two-factor designs, three methods of permutations and two statistics were compared. The results showed that permutation of the residuals with F pseudo is accurate and can give good power for testing the interaction and restricted permutation for testing main factors. 相似文献
110.
《Journal of Statistical Computation and Simulation》2012,82(7):1530-1542
In many real-life networks such as computer networks, branches and nodes have multi-state capacity, lead time, and accuracy rate. The network with unreliable nodes is more complex to evaluate the reliability because node failure results in the disabled of adjacent branches. Such a network is named a stochastic unreliable-node computer network (SUNCN). Under the strict assumption that each component (branch and node) has a deterministic capacity, the quickest path (QP) problem is to find a path sending a specific amount of data with minimum transmission time. The accuracy rate is a critical index to measure the performance of a computer network because some packets are damaged or lost due to voltage instability, magnetic field effects, lightning, etc. Subject to both assured accuracy rate and time constraints, this paper extends the QP problem to discuss the system reliability of an SUNCN. An efficient algorithm based on a graphic technique is proposed to find the minimal capacity vector meeting such constraints. System reliability, the probability to send a specific amount of data through multiple minimal paths subject to both assured accuracy rate and time constraints, can subsequently be computed. 相似文献