全文获取类型
收费全文 | 115561篇 |
免费 | 28738篇 |
国内免费 | 21134篇 |
专业分类
化学 | 75593篇 |
晶体学 | 1371篇 |
力学 | 7665篇 |
综合类 | 446篇 |
数学 | 14434篇 |
物理学 | 65924篇 |
出版年
2024年 | 553篇 |
2023年 | 1497篇 |
2022年 | 2049篇 |
2021年 | 2019篇 |
2020年 | 2460篇 |
2019年 | 2976篇 |
2018年 | 2683篇 |
2017年 | 3123篇 |
2016年 | 3961篇 |
2015年 | 4199篇 |
2014年 | 4417篇 |
2013年 | 6814篇 |
2012年 | 7875篇 |
2011年 | 9373篇 |
2010年 | 11463篇 |
2009年 | 11698篇 |
2008年 | 5718篇 |
2007年 | 5049篇 |
2006年 | 4523篇 |
2005年 | 4515篇 |
2004年 | 4999篇 |
2003年 | 4077篇 |
2002年 | 3881篇 |
2001年 | 3906篇 |
2000年 | 3060篇 |
1999年 | 3414篇 |
1998年 | 2867篇 |
1997年 | 2667篇 |
1996年 | 3050篇 |
1995年 | 3321篇 |
1994年 | 3324篇 |
1993年 | 3287篇 |
1992年 | 2827篇 |
1991年 | 2443篇 |
1990年 | 2035篇 |
1989年 | 2090篇 |
1988年 | 2017篇 |
1987年 | 1279篇 |
1986年 | 1324篇 |
1985年 | 999篇 |
1984年 | 1072篇 |
1982年 | 944篇 |
1981年 | 776篇 |
1980年 | 790篇 |
1979年 | 549篇 |
1978年 | 554篇 |
1977年 | 661篇 |
1976年 | 1065篇 |
1973年 | 450篇 |
1972年 | 549篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
The object of this note is to prove the followingTheorem Let{a_n}and{b_n}be sequences of real numbers such that0<∑∑a_n~2<+∞and0<∑b_n~2<+∞.Then we have the inequalitysum from m=1 to∞sum from n=1 to∞a_mb_n/m+n<{sum from n=1 to∞(π-θ/n~(1/2)a_n~2}~1/2{sum from n=1 to∞(π-θ/n~(1/2)b_n~2}~1/2 (1)whereθ=3/2~(1/2)-1=1.121320343. 相似文献
122.
123.
LI Yu-qiong SUN Zhen-rong ZHANG Shi-an YANG Xi-hua WANG Zu-geng. Key Laboratory of Optical Magnetic Resonance Spectroscopy 《光谱学与光谱分析》2006,26(8):1395-1395
The authors achieved the temporal coherent control in an Er^3+ doped telluride glass, one kind of disordered solids. The upconversion at 670 nm was modulated and the dephasing time was simulated as 300 fs. Moreover, the photon echo signal gave the dephasing time due to the phonon interaction. The agreement between the two data indicates that the interaction between the wavepacket and the phonon leads to the fast disappearance of wavepackets interference, which is helpful for the tech- nique to be applied to the disordered solids. 相似文献
124.
应用不可约张量理论构造了三角对称晶场中3d2/3d8态离子的45阶可完全对角化的微扰哈密顿矩阵,研究了CsNiCl3晶体的光谱精细结构、晶体结构、零场分裂参量、Jahn-Telller效应以及自旋单重态对Ni2+离子基态能级的影响,理论与实验相符合.在此基础上,进一步研究了以前工作中被忽略的自旋-自旋耦合作用和Trees修正对CsNiCl3晶体的光谱精细结构和零场分裂参量的影响,发现有四种机理会影响零场分裂参量:1)自旋-轨道耦合机理,2)自旋-自旋耦合机理;3)自旋-轨道与自旋-自旋联合耦合机理;4)自旋-轨道与Trees修正联合耦合机理,其中自旋-轨道耦合机理是最主要的,其他三种机理也是不可忽略的.
关键词:
基态能级
精细结构
零场分裂
自旋-自旋耦合 相似文献
125.
This paper reports that the growth of RuOx(110) thin layer growth on Ru(0001)
has been investigated by means of scanning tunnelling microscope (STM). The STM
images showed a domain structure with three rotational domains of RuOx(110)
rotated by an angle of 120℃.
The as-grown RuOx(110) thin layer is expanded from the bulk-truncated
RuOx(110) due to the large mismatch between RuOx(110) and the
Ru(0001) substrate. The results also indicate that growth of RuOx(110)
thin layer on the Ru(0001) substrate by oxidation tends first to formation
of the Ru-O (oxygen) chains in the [001] direction of RuOx(110). 相似文献
126.
127.
L. Tong Y. Tian Q. Y. Wang Y. S. Ling 《International Journal of Infrared and Millimeter Waves》2006,27(9):1307-1314
The paper introduces a special system calibration technology in s-parameters measurement of microwave and millimeter wave
devices. The 8-term errors module is built by analyzing the signals flowing in the measurement system. Then the calibration
technology using non-standard kits is designed on the base. Finally, the experiment using the calibration technology is introduced. 相似文献
128.
Maria Kordaki Athanasia Balomenou 《International Journal of Computers for Mathematical Learning》2006,11(1):99-135
This study focuses on the constructions in terms of area and perimeter in equivalent triangles developed by students aged 12–15 years-old, using the tools provided by Cabri-Geometry II [Labore (1990). Cabri-Geometry (software), Université de Grenoble]. Twenty-five students participated in a learning experiment where they were asked to construct: (a) pairs of equivalent triangles “in as many ways as possible” and to study their area and their perimeter using any of the tools provided and (b) “any possible sequence of modifications of an original triangle into other equivalent ones”. As regards the concept of area and in contrast to a paper and pencil environment, Cabri provided students with different and potential opportunities in terms of: (a) means of construction, (b) control, (c) variety of representations and (d) linking representations, by exploiting its capability for continuous modifications. By exploiting these opportunities in the context of the given open tasks, students were helped by the tools provided to develop a broader view of the concept of area than the typical view they would construct in a typical paper and pencil environment. 相似文献
129.
130.
关于四元数矩阵乘积迹的不等式 总被引:1,自引:0,他引:1
设 H~(m×n)为 m×n 四元数矩阵的集合,σ_1(A)≥…≥σ_n(A)为 A∈H~(mxn)的奇异值。本文证明了:1)设 A∈H~(mxm),B∈H~(mxm),r=min(m,m),则|tr(4B)|≤c r σ_i(A)σ_i(B).2)设 A_i∈H~(mxm),i=1,2,…,n,(A_1A_2…A_n)k为 A_1A_2…A_n 的任一个 k 阶主子阵,则|tr(A_1.A_2…A_n)_k|≤sun form i=1 to k σ_i(A_1)…σ_i(A_n).我们还得到四元数矩阵迹的其它一些不等式。这些结果推广和改进了文[1],[2]中的结果,进一步解决了 Bellman 猜想。 相似文献