全文获取类型
收费全文 | 16614篇 |
免费 | 1508篇 |
国内免费 | 1332篇 |
专业分类
化学 | 3192篇 |
晶体学 | 44篇 |
力学 | 1235篇 |
综合类 | 310篇 |
数学 | 11679篇 |
物理学 | 2994篇 |
出版年
2024年 | 11篇 |
2023年 | 146篇 |
2022年 | 184篇 |
2021年 | 240篇 |
2020年 | 358篇 |
2019年 | 413篇 |
2018年 | 398篇 |
2017年 | 496篇 |
2016年 | 505篇 |
2015年 | 404篇 |
2014年 | 741篇 |
2013年 | 1217篇 |
2012年 | 709篇 |
2011年 | 888篇 |
2010年 | 793篇 |
2009年 | 955篇 |
2008年 | 1052篇 |
2007年 | 1123篇 |
2006年 | 950篇 |
2005年 | 831篇 |
2004年 | 690篇 |
2003年 | 708篇 |
2002年 | 676篇 |
2001年 | 594篇 |
2000年 | 537篇 |
1999年 | 497篇 |
1998年 | 480篇 |
1997年 | 404篇 |
1996年 | 343篇 |
1995年 | 307篇 |
1994年 | 239篇 |
1993年 | 214篇 |
1992年 | 172篇 |
1991年 | 152篇 |
1990年 | 115篇 |
1989年 | 88篇 |
1988年 | 84篇 |
1987年 | 84篇 |
1986年 | 73篇 |
1985年 | 88篇 |
1984年 | 71篇 |
1983年 | 41篇 |
1982年 | 72篇 |
1981年 | 70篇 |
1980年 | 47篇 |
1979年 | 53篇 |
1978年 | 45篇 |
1977年 | 27篇 |
1976年 | 25篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
1.
The row iterative method is popular in solving the large‐scale ill‐posed problems due to its simplicity and efficiency. In this work we consider the randomized row iterative (RRI) method to tackle this issue. First, we present the semiconvergence analysis of RRI method for the overdetermined and inconsistent system, and derive upper bounds for the noise error propagation in the iteration vectors. To achieve a least squares solution, we then propose an extended version of the RRI (ERRI) method, which in fact can converge in expectation to the solution of the overdetermined or underdetermined, consistent or inconsistent systems. Finally, some numerical examples are given to demonstrate the convergence behaviors of the RRI and ERRI methods for these types of linear system. 相似文献
2.
Given a graph sequence denote by T3(Gn) the number of monochromatic triangles in a uniformly random coloring of the vertices of Gn with colors. In this paper we prove a central limit theorem (CLT) for T3(Gn) with explicit error rates, using a quantitative version of the martingale CLT. We then relate this error term to the well-known fourth-moment phenomenon, which, interestingly, holds only when the number of colors satisfies . We also show that the convergence of the fourth moment is necessary to obtain a Gaussian limit for any , which, together with the above result, implies that the fourth-moment condition characterizes the limiting normal distribution of T3(Gn), whenever . Finally, to illustrate the promise of our approach, we include an alternative proof of the CLT for the number of monochromatic edges, which provides quantitative rates for the results obtained in [7]. 相似文献
3.
《Operations Research Letters》2022,50(3):274-280
The minimum k-enclosing ball problem seeks the ball with smallest radius that contains at least k of m given points. This problem is NP-hard. We present a branch-and-bound algorithm on the tree of the subsets of k points to solve this problem. Our method is able to solve the problem exactly in a short amount of time for small and medium sized datasets. 相似文献
4.
SHI Wanlin 《应用概率统计》2021,37(1):37-46
We study the moderate deviation probability of the position of the rightmost particle in a branching Brownian motion and obtain its moderate deviation function. Firstly, Chauvin and Rouault studied the large deviation probability for the rightmost position in a branching Brownian motion. Recently, Derrida and Shiconsidered lower deviation for the same model. By contrast, Our main result is more extensive. 相似文献
5.
This work is concerned with the extension of the Jacobi spectral Galerkin method to a class of nonlinear fractional pantograph differential equations. First, the fractional differential equation is converted to a nonlinear Volterra integral equation with weakly singular kernel. Second, we analyze the existence and uniqueness of solutions for the obtained integral equation. Then, the Galerkin method is used for solving the equivalent integral equation. The error estimates for the proposed method are also investigated. Finally, illustrative examples are presented to confirm our theoretical analysis. 相似文献
6.
The purpose of this article is to investigate high‐order numerical approximations of scalar conservation laws with nonlocal viscous term. The viscous term is given in the form of convolution in space variable. With the help of the characteristic of viscous term, we design a semidiscrete local discontinuous Galerkin (LDG) method to solve the nonlocal model. We prove stability and convergence of semidiscrete LDG method in L2 norm. The theoretical analysis reveals that the present numerical scheme is stable with optimal convergence order for the linear case, and it is stable with sub‐optimal convergence order for nonlinear case. To demonstrate the validity and accuracy of our scheme, we test the Burgers equation with two typical nonlocal fractional viscous terms. The numerical results show the convergence order accuracy in space for both linear and nonlinear cases. Some numerical simulations are provided to show the robustness and effectiveness of the present numerical scheme. 相似文献
7.
8.
9.
针对架空输电线路铁塔中常用的四地脚螺栓塔脚板进行了抗拉承载力试验和理论计算方法研究。首先,选取8个试件进行塔脚板抗拉承载力试验研究,分析塔脚底板板厚及有无加劲板对塔脚板抗拉承载力的影响;其次,通过有限元模拟塔脚板的应力分布情况,并结合“塑性分析,弹性设计”的思想,提出了一种基于屈服线理论的四地脚螺栓塔脚板抗拉承载力计算公式;最后,与试验结果、有限元仿真结果、已有技术规定中的计算结果进行了对比。结果表明:建议公式与试验结果和仿真结果较为吻合,相关技术规定中的计算结果偏于保守,验证了本文建议公式的精确性;底板厚度和加劲板的作用对塔脚板承载力影响较大。研究结果可为输电铁塔四地脚螺栓塔脚板结构设计提供参考。 相似文献
10.