全文获取类型
收费全文 | 100498篇 |
免费 | 26692篇 |
国内免费 | 19888篇 |
专业分类
化学 | 65464篇 |
晶体学 | 1241篇 |
力学 | 6684篇 |
综合类 | 264篇 |
数学 | 12423篇 |
物理学 | 61002篇 |
出版年
2024年 | 453篇 |
2023年 | 1157篇 |
2022年 | 1263篇 |
2021年 | 1478篇 |
2020年 | 1871篇 |
2019年 | 2372篇 |
2018年 | 2158篇 |
2017年 | 2780篇 |
2016年 | 3245篇 |
2015年 | 3503篇 |
2014年 | 3479篇 |
2013年 | 5757篇 |
2012年 | 6364篇 |
2011年 | 8104篇 |
2010年 | 10625篇 |
2009年 | 10801篇 |
2008年 | 4937篇 |
2007年 | 4305篇 |
2006年 | 3893篇 |
2005年 | 4041篇 |
2004年 | 4605篇 |
2003年 | 3741篇 |
2002年 | 3544篇 |
2001年 | 3667篇 |
2000年 | 2808篇 |
1999年 | 3063篇 |
1998年 | 2625篇 |
1997年 | 2420篇 |
1996年 | 2774篇 |
1995年 | 3139篇 |
1994年 | 3178篇 |
1993年 | 3157篇 |
1992年 | 2703篇 |
1991年 | 2360篇 |
1990年 | 1936篇 |
1989年 | 2005篇 |
1988年 | 1966篇 |
1987年 | 1233篇 |
1986年 | 1281篇 |
1985年 | 938篇 |
1984年 | 1032篇 |
1982年 | 930篇 |
1981年 | 761篇 |
1980年 | 797篇 |
1979年 | 543篇 |
1978年 | 540篇 |
1977年 | 641篇 |
1976年 | 1047篇 |
1973年 | 441篇 |
1972年 | 536篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
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
102.
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
103.
104.
105.
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
106.
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
107.
Xuguang Lu 《Journal of statistical physics》2006,124(2-4):517-547
The paper considers macroscopic behavior of a Fermi–Dirac particle system. We prove the L
1-compactness of velocity averages of weak solutions of the Boltzmann equation for Fermi–Dirac particles in a periodic box with the collision kernel b(cos θ)|ρ−ρ
*|γ, which corresponds to very soft potentials: −5 < γ ≤ −3 with a weak angular cutoff: ∫0
π
b(cos θ)sin 3θ dθ < ∞. Our proof for the averaging compactness is based on the entropy inequality, Hausdorff–Young inequality, the L
∞-bounds of the solutions, and a specific property of the value-range of the exponent γ. Once such an averaging compactness is proven, the proof of the existence of weak solutions will be relatively easy. 相似文献
108.
109.
110.
In developing travel demand models it is generally assumed that the base-year data used in developing the parameters, as well as the forecasted data to be used as independent variables for the design year, are of acceptable quality. The purpose of this paper is to present the application of error propagation theory in assesing the predictive quality of one type of travel demand forecasting model (multinomial logit models) and to demonstrate how error considerations can be used as a tool for identifying the optimal model. The general conclusions of this study are that: (1) it is indeed possible to quantify errors in dependent variables in logit models as a consequence of errors in independent variables; and (2) error consideration can be used as a tool for identifying the optimal model from a set of candidate models. Further research is recommended to develop better insights into the phenomenon of error propagation so that the consideration of errors can be a factor in decisions on model selection. 相似文献