全文获取类型
收费全文 | 3163篇 |
免费 | 85篇 |
国内免费 | 83篇 |
专业分类
化学 | 151篇 |
晶体学 | 1篇 |
力学 | 38篇 |
综合类 | 65篇 |
数学 | 329篇 |
物理学 | 104篇 |
综合类 | 2643篇 |
出版年
2024年 | 7篇 |
2023年 | 34篇 |
2022年 | 40篇 |
2021年 | 56篇 |
2020年 | 64篇 |
2019年 | 47篇 |
2018年 | 49篇 |
2017年 | 59篇 |
2016年 | 50篇 |
2015年 | 113篇 |
2014年 | 159篇 |
2013年 | 151篇 |
2012年 | 202篇 |
2011年 | 224篇 |
2010年 | 183篇 |
2009年 | 177篇 |
2008年 | 218篇 |
2007年 | 237篇 |
2006年 | 212篇 |
2005年 | 172篇 |
2004年 | 149篇 |
2003年 | 137篇 |
2002年 | 117篇 |
2001年 | 86篇 |
2000年 | 63篇 |
1999年 | 56篇 |
1998年 | 32篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 32篇 |
1994年 | 24篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 21篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有3331条查询结果,搜索用时 15 毫秒
151.
A. J. van der Merwe P. C. N. Groenewald C. A. van der Merwe 《Annals of the Institute of Statistical Mathematics》1988,40(4):747-767
In this paper hierarchical Bayes and empirical Bayes results are used to obtain confidence intervals of the population means in the case of real problems. This is achieved by approximating the posterior distribution with a Pearson distribution. In the first example hierarchical Bayes confidence intervals for the Efron and Morris (1975, J. Amer. Statist. Assoc., 70, 311–319) baseball data are obtained. The same methods are used in the second example to obtain confidence intervals of treatment effects as well as the difference between treatment effects in an analysis of variance experiment. In the third example hierarchical Bayes intervals of treatment effects are obtained and compared with normal approximations in the unequal variance case.Financially supported by the CSIR and the University of the Orange Free State, Central Research Fund. 相似文献
152.
Jnos Csirik Gerhard
J. Woeginger 《Journal of Algorithms in Cognition, Informatics and Logic》2002,44(2):1016
We study online bounded space bin packing in the resource augmentation model of competitive analysis. In this model, the online bounded space packing algorithm has to pack a list L of items in (0,1] into a small number of bins of size b1. Its performance is measured by comparing the produced packing against the optimal offline packing of the list L into bins of size 1.We present a complete solution to this problem: For every bin size b1, we design online bounded space bin packing algorithms whose worst case ratio in this model comes arbitrarily close to a certain bound ρ(b). Moreover, we prove that no online bounded space algorithm can perform better than ρ(b) in the worst case. 相似文献
153.
The Isoenergetic KAM-Type Theorem at Resonant Case for Nearly Integrable Hamiltonian Systems 下载免费PDF全文
In this paper, we study the persistence of resonant invariant tori on energy surfaces for nearly integrable Hamiltonian systems under the usual R$\ddot{u}$ssmann nondegenerate condition. By a quasilinear iterative scheme, we prove the following things: (1) The majority of resonant tori on a given energy surface will be persisted under R$\ddot{u}$ssmann nondegenerate condition. (2) The maximal number about the preserved frequency components on a perturbed torus is characterized by the smaller of the maximal rank of the Hessian matrices of the unperturbed system and the nondegeneracy of resonance. (3) If unperturbed systems admit subisoenergetic nondegeneracy on an energy surface, then the majority of the unperturbed resonant tori on the energy surface will be persisted and give rise to a family of perturbed tori with the same energy, whose frequency ratios among respective ''nondegenerate'' components are preserved. 相似文献
154.
新疆区域农业品牌价值最大化及其评价指标与模型 总被引:2,自引:0,他引:2
基于对区域农业品牌和新疆区域农业品牌发展的研究综述,应用产品整体概念理论探讨了新疆农产品多层面产品要素的品牌化和综合品牌价值最大化,分析了支撑新疆农产品品牌价值最大化的产业链管理与创新,构建了新疆农业品牌价值最大化评价指标体系,并请新疆的11位农业专家进行评分,应用AHP方法得到了各指标的权重,构建了定量评价模型,以库尔勒香梨为案例,应用模糊综合评价方法测度了特定农产品品种的区域品牌价值,明确了新疆区域农业品牌发展面临的薄弱环节,为新疆政府和企业的品牌农业决策提供了理论依据. 相似文献
155.
给出指数2情形下阶数为2l_1~(r1)l_1~(r2)的高斯和的显式计算公式.证明方法直接利用Stickelberger理想分解定理,进而结果独立于其他指数2情形高斯和的结果而成立. 相似文献
156.
本文讨论了极限圆型Hamilton算子乘积的自伴性,利用Calkin方法及奇异Hamilton系统自伴扩张的一般构造理论,给出了在极限圆型时判定Hamilton算子乘积自伴的一个充要条件. 相似文献
157.
经济数学是财经类专业的重要基础课程,在经济数学教学中讲授数学的基本概念和定理的同时,怎样引入数学模型进行教学,培养和激发学生学习数学的兴趣,是我们从事经济数学教学的教师都应该探讨的问题.本文结合经济数学教学的实践,介绍了经济数学教学中的几个经典经济模型案例,将数学与经济学有机地联系起来,让数学变得既生动又符合实际,取得了很好的教学效果. 相似文献
158.
对于产品寿命服从Weibull分布或对数正态分布的情形,针对几种不同类型的数据(例如随机截尾,定数截尾情形出现的数据),分别给出了可靠性参数(可靠度、可靠寿命)的点估计或置信下限。特别是在定时截尾出现零失效情形,给出了可靠性参数的置信下限的计算公式。 相似文献
159.
J. Galen Buckwalter Brian Castellani Bruce Mcewen Arun S. Karlamangla Albert A. Rizzo Bruce John Kyle O'donnell Teresa Seeman 《Complexity》2016,21(Z1):291-306
Allostatic load (AL) is a complex clinical construct, providing a unique window into the cumulative impact of stress. However, due to its inherent complexity, AL presents two major measurement challenges to conventional statistical modeling (the field's dominant methodology): it is comprised of a complex causal network of bioallostatic systems, represented by an even larger set of dynamic biomarkers; and, it is situated within a web of antecedent socioecological systems, linking AL to differences in health outcomes and disparities. To address these challenges, we employed case‐based computational modeling (CBM), which allowed us to make four advances: (1) we developed a multisystem, 7‐factor (20 biomarker) model of AL's network of allostatic systems; (2) used it to create a catalog of nine different clinical AL profiles (causal pathways); (3) linked each clinical profile to a typology of 23 health outcomes; and (4) explored our results (post hoc) as a function of gender, a key socioecological factor. In terms of highlights, (a) the Healthy clinical profile had few health risks; (b) the pro‐inflammatory profile linked to high blood pressure and diabetes; (c) Low Stress Hormones linked to heart disease, TIA/Stroke, diabetes, and circulation problems; and (d) high stress hormones linked to heart disease and high blood pressure. Post hoc analyses also found that males were overrepresented on the High Blood Pressure (61.2%), Metabolic Syndrome (63.2%), High Stress Hormones (66.4%), and High Blood Sugar (57.1%); while females were overrepresented on the Healthy (81.9%), Low Stress Hormones (66.3%), and Low Stress Antagonists (stress buffers) (95.4%) profiles. © 2015 Wiley Periodicals, Inc. Complexity 21: 291–306, 2016 相似文献
160.
A new two‐phase structure‐preserving doubling algorithm for critically singular M‐matrix algebraic Riccati equations 下载免费PDF全文
Tsung‐Ming Huang Wei‐Qiang Huang Ren‐Cang Li Wen‐Wei Lin 《Numerical Linear Algebra with Applications》2016,23(2):291-313
Among numerous iterative methods for solving the minimal nonnegative solution of an M‐matrix algebraic Riccati equation, the structure‐preserving doubling algorithm (SDA) stands out owing to its overall efficiency as well as accuracy. SDA is globally convergent and its convergence is quadratic, except for the critical case for which it converges linearly with the linear rate 1/2. In this paper, we first undertake a delineatory convergence analysis that reveals that the approximations by SDA can be decomposed into two components: the stable component that converges quadratically and the rank‐one component that converges linearly with the linear rate 1/2. Our analysis also shows that as soon as the stable component is fully converged, the rank‐one component can be accurately recovered. We then propose an efficient hybrid method, called the two‐phase SDA, for which the SDA iteration is stopped as soon as it is determined that the stable component is fully converged. Therefore, this two‐phase SDA saves those SDA iterative steps that previously have to have for the rank‐one component to be computed accurately, and thus essentially, it can be regarded as a quadratically convergent method. Numerical results confirm our analysis and demonstrate the efficiency of the new two‐phase SDA. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献