全文获取类型
收费全文 | 20404篇 |
免费 | 3873篇 |
国内免费 | 3367篇 |
专业分类
化学 | 15637篇 |
晶体学 | 365篇 |
力学 | 1284篇 |
综合类 | 241篇 |
数学 | 2386篇 |
物理学 | 7731篇 |
出版年
2024年 | 34篇 |
2023年 | 330篇 |
2022年 | 662篇 |
2021年 | 704篇 |
2020年 | 796篇 |
2019年 | 827篇 |
2018年 | 726篇 |
2017年 | 706篇 |
2016年 | 1037篇 |
2015年 | 1128篇 |
2014年 | 1265篇 |
2013年 | 1597篇 |
2012年 | 1930篇 |
2011年 | 2022篇 |
2010年 | 1513篇 |
2009年 | 1488篇 |
2008年 | 1516篇 |
2007年 | 1304篇 |
2006年 | 1230篇 |
2005年 | 1083篇 |
2004年 | 868篇 |
2003年 | 694篇 |
2002年 | 820篇 |
2001年 | 686篇 |
2000年 | 479篇 |
1999年 | 401篇 |
1998年 | 344篇 |
1997年 | 251篇 |
1996年 | 203篇 |
1995年 | 186篇 |
1994年 | 149篇 |
1993年 | 126篇 |
1992年 | 110篇 |
1991年 | 106篇 |
1990年 | 68篇 |
1989年 | 43篇 |
1988年 | 34篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 20篇 |
1984年 | 25篇 |
1983年 | 15篇 |
1982年 | 8篇 |
1981年 | 16篇 |
1980年 | 9篇 |
1979年 | 11篇 |
1978年 | 5篇 |
1974年 | 5篇 |
1971年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
该文给出了帐篷映射产生的迭代序列Cesaro平均收敛的条件.研究了它与实数二进展式度量性质之间的联系. 相似文献
52.
第一讲中子散射与散裂中子源 总被引:1,自引:0,他引:1
中子散射是研究物质微观结构和动态的理想工具之一,广泛地应用于凝聚态物质研究和应用的众多学科领域.散裂中子源能是新一代的加速器基脉冲中子源,能为中子散射提供高通量的脉冲中子.文章简明地介绍了中子散射的特点和它作为物质结构和动态探针的优越性,以及散裂中子源的基本原理、发展状况和多学科的应用优势.我国计划建设的散裂中子源CSNS中,靶站将由多片钨靶、铍/铁反射体和铁/重混凝土生物屏蔽体组成.质子束功率100kW下,脉冲中子通量约为2.4×1016n/cm2/s.第一期将设计建造高通量粉末衍射仪、高分辨粉末衍射仪、小角散射仪、多功能反射仪和直接几何非弹性散射仪等五台典型的中子散射谱仪,以覆盖大部分的中子散射研究领域. 相似文献
53.
54.
三种群食物链交错扩散模型的整体 总被引:1,自引:0,他引:1
本文应用能量估计方法和Gagliardo-Nirenberg型不等式证明了一类强耦合反应扩散系统整体解的存在性和一致有界性,该系统是带自扩散和交错扩散项的三种群Lotka-Volterra食物链模型.通过构造Lyapunov函数给出了该模型正平衡点全局渐近稳定的充分条件. 相似文献
55.
Tensile impact experiments of EC8.0−24×7 glass fiber bundles at different low temperaturesT(14°C, −40°C and −10°C) and strain rates ɛ were carried out, and complete stress-strain curves were obtained. Within the range
of the experiment temperatures and strain rates, it is found that the initial modulusE, the ultimate strength σmax and the unstable strain ɛ
b
of the glass fiber bundles all increase with ɛ at an identicalT. At an identical ɛ, with the decrease ofT, E and σmax increase; but ɛ
b
increases when 10°C>T>−40°C and decreases when −40°C>T>−100°C. The strain-rate- and temperature-dependent bimodal Weibull statistical constitutive theory was adopted for the statistical
analysis of the experimental results, and the Weibull parameters of single fiber were obtained. The results show that the
bimodal Weibull distribution function is suitable to represent the strength distribution of the glass fiber at low temperature
and different strain rates. The differences in the mechanical properties between EC8.0−24×7 and EC5.5−12 ×14 glass fiber bundles
were also discussed.
Project supported by the National Natural Science Foundation of China (No. 19772058). 相似文献
56.
For vertical-cavity surface-emitting lasers (VCSELs) with polarization-rotated feedback, there exist several synchronization
types such as synchronizations between total powers and synchronizations between separate polarization modes. Based on the
two-mode rate equations, we study and compare numerically the performances of different synchronization types. Our results
show that three synchronization types exhibit good performances when their synchronization conditions are satisfied. They
are the complete synchronization between total powers, complete synchronization between x-polarized modes, and generalized synchronization between x-polarized and y-polarized modes. The former two types are sensitive to the injection rate and spontaneous emission, while the third type
is contrary. Synchronization type with the best performance may switch from one to another, with changing of injection rate
and spontaneous emission factor. 相似文献
57.
Bing Yong HSIE 《数学学报(英文版)》2006,22(2):507-514
This paper gives a p-adic analogue of the Mackey theory, which relates representations of a group of type G - H × t A to systems of imprimitivity. 相似文献
58.
59.
We discuss the matrix model in a class of 11D time dependent supersymmetric backgrounds as obtained in [B. Chen, Phys. Lett. B 632 (2006) 393, hep-th/0508191]. We construct the matrix model action through the matrix regularization of the membrane action in the background. We show that the action is exact to all orders of fermionic coordinates. Furthermore we discuss the fuzzy sphere solutions in this background. 相似文献
60.
Shu Fen Wang Wen Guo Zou Su Wen Liu Dong Xu Duo Rong Yuan Guang Jun Zhou 《Journal of Physics and Chemistry of Solids》2004,65(7):1243-1245
The photoluminescence properties of the Bi3+ in sol-gel derived ZnTiO3 nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the 3P1-1S0 transition of Bi3+ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant. 相似文献