全文获取类型
收费全文 | 141篇 |
免费 | 5篇 |
国内免费 | 2篇 |
专业分类
化学 | 9篇 |
力学 | 23篇 |
数学 | 65篇 |
物理学 | 31篇 |
综合类 | 20篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 18篇 |
2008年 | 13篇 |
2007年 | 5篇 |
2006年 | 13篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 4篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有148条查询结果,搜索用时 15 毫秒
1.
2.
Qing-Lun Wang Li-Na Zhu Dai-Zheng Liao Shi-Ping Yan Zong-Hui Jiang Peng Cheng Guang-Ming Yang 《Journal of Molecular Structure》2005,754(1-3):10-15
A new oxamato-bridged NiIICuIINiII species, [Ni(tacn)(H2O)]2[μ-Cu(pba)](ClO4)2·6H2O 1, (tacn=1,4,7-triazacyclononane; pba=1,3-propylenebis(oxamato)) has been synthesized and structurally as well as magnetically characterized. Complex 1 has a discrete trinuclear NiIICuIINiII structure: Two nickel(II) ions are bridged by [Cu(pba)]2− anion, macrocyclic ligand tacn works as terminal ligand of the nickel(II) center. The magnetic data of compound 1 was analyzed by means ofleading to gCu=2.19, gNi=2.18, J=−112.8 cm−1, D=±4.31 cm−1. The parameters are compared with the similar complexes and the irregular spin state structure of complex 1 is also described here. 相似文献
3.
Based on Galois Field (GF(q)) multiplicative group, a new coding scheme for Quasi-Cyclic Low-Density Parity-Check (QC-LDPC) codes is proposed, and the new coding scheme has some advantages such as the simpler construction, the easier implementation encoding, the lower complexity of the encoding and decoding, the more flexible adjustment of the code length as well as the code rate and so forth. Under the condition of considering the characteristics of optical transmission systems, an irregular QC-LDPC (3843,3603) code to be suitable for optical transmission systems is constructed by applying the proposed new coding scheme. The simulation result shows that the net coding gain (NCG) of the irregular QC-LDPC (3843,3603) code is respectively improved 2.14 dB, 1.19 dB, 0.24 dB and 0.14 dB more than those of the classic RS (255,239) code in ITU-T G.975, the LDPC (32640,30592) code in ITU-T G.975.1, the regular SCG-LDPC (3969,3720) code constructed by the Systematically Constructed Gallager (SCG) coding scheme and the regular QC-LDPC (4221,3956) code at the bit error rate (BER) of 10-8. Furthermore, all the five codes have the same code rate of 93.7%. Therefore, the irregular QC-LDPC (3843,3603) code constructed by the proposed new coding scheme has the more excellent error-correction performance and can be better suitable for optical transmission systems. 相似文献
4.
本文阐明了柴油机供油系统中油—汽两相流与不规则喷射的内在联系.分析了不规则喷射产生的机理,并指出在高速小负荷工况下,供油系统中的汽泡是产生不规则喷射的主要原因. 相似文献
5.
闻国椿 《烟台大学学报(自然科学与工程版)》1992,(4)
本文讨论n维空间区域上二阶完全非线性椭圆型方程的非正则斜微商边值问题的可解性,在某些自然结构的条件下,我们先给出了上述边值问题解的先验估计式,进而用参数开拓法证明了此边值问题的可解性。 相似文献
6.
本文论述柴油机供油系统中出油阀紧帽腔,高压油管,油嘴盛油槽汽泡产生及溃灭过程。供油系统中是否产生汽泡,可从压力波尾部的振荡情况来判断。并阐明汽泡对柴油机油耗及不规则喷射的影响机理。 相似文献
7.
Masafumi Yoshino 《Annali di Matematica Pura ed Applicata》2008,187(4):555-562
We study a C
∞-Liouville-integrable and analytic non-integrable Hamiltonian system. We will show that an irregular singular character plays
a crucial role in the analytic non-integrability of the system.
Partially supported by Grant-in-Aid for Scientific Research (No. 11640183), Ministry of Education, Science and Culture, Japan. 相似文献
8.
An important tool for the construction of tight wavelet frames is the Unitary Extension Principle first formulated in the Fourier-domain by Ron and Shen. We show that the time-domain analogue of this principle provides a unified approach to the construction of tight frames based on many variations of multiresolution analyses, e.g., regular refinements of bounded L-shaped domains, refinements of subdivision surfaces around irregular vertices, and nonstationary subdivision. We consider the case of nonnegative refinement coefficients and develop a fully local construction method for tight frames. Especially, in the shift-invariant setting, our construction produces the same tight frame generators as the Unitary Extension Principle. 相似文献
9.
We introduce a second-order solver for the Poisson–Boltzmann equation in arbitrary geometry in two and three spatial dimensions. The method differs from existing methods solving the Poisson–Boltzmann equation in the two following ways: first, non-graded Quadtree (in two spatial dimensions) and Octree (in three spatial dimensions) grid structures are used; Second, Neumann or Robin boundary conditions are enforced at the irregular domain’s boundary. The irregular domain is described implicitly and the grid needs not to conform to the domain’s boundary, which makes grid generation straightforward and robust. The linear system is symmetric, positive definite in the case where the grid is uniform, nonsymmetric otherwise. In this case, the resulting matrix is an M-matrix, thus the linear system is invertible. Convergence examples are given in both two and three spatial dimensions and demonstrate that the solution is second-order accurate and that Quadtree/Octree grid structures save a significant amount of computational power at no sacrifice in accuracy. 相似文献
10.
The main result of this paper establishes that the irregularity strength of any tree with no vertices of degree two is its number of pendant vertices. 相似文献