全文获取类型
收费全文 | 31708篇 |
免费 | 6284篇 |
国内免费 | 7678篇 |
专业分类
化学 | 23617篇 |
晶体学 | 839篇 |
力学 | 2122篇 |
综合类 | 983篇 |
数学 | 4248篇 |
物理学 | 13861篇 |
出版年
2024年 | 62篇 |
2023年 | 447篇 |
2022年 | 1062篇 |
2021年 | 1035篇 |
2020年 | 1206篇 |
2019年 | 1218篇 |
2018年 | 1097篇 |
2017年 | 1231篇 |
2016年 | 1328篇 |
2015年 | 1574篇 |
2014年 | 1937篇 |
2013年 | 2486篇 |
2012年 | 2739篇 |
2011年 | 3018篇 |
2010年 | 2406篇 |
2009年 | 2516篇 |
2008年 | 2736篇 |
2007年 | 2474篇 |
2006年 | 2292篇 |
2005年 | 1919篇 |
2004年 | 1560篇 |
2003年 | 1189篇 |
2002年 | 1254篇 |
2001年 | 1174篇 |
2000年 | 1064篇 |
1999年 | 800篇 |
1998年 | 525篇 |
1997年 | 460篇 |
1996年 | 406篇 |
1995年 | 353篇 |
1994年 | 341篇 |
1993年 | 284篇 |
1992年 | 220篇 |
1991年 | 197篇 |
1990年 | 179篇 |
1989年 | 147篇 |
1988年 | 137篇 |
1987年 | 118篇 |
1986年 | 88篇 |
1985年 | 68篇 |
1984年 | 67篇 |
1983年 | 59篇 |
1982年 | 51篇 |
1981年 | 39篇 |
1980年 | 23篇 |
1979年 | 24篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1971年 | 5篇 |
1959年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
ZHU Yabin ZHOU Yueliang LIU Zhen WANG Shufang CHEN Zhenghao U Huibin YANG Guozhen XlAO Ling Ren Hongtao JIAO Yulei Zheng Minghui 《中国科学G辑(英文版)》2004,47(2):165-172
The irreversibility field (Hirr) of Y-based superconductor is much higher than that of Bi-based superconductor. Y-based superconductor is capable of maintaining stable electrical currents in high magnetic field and electric field, so it is a better suited mate-rial for electric-current applications. Commonly, the Y-based tapes comprise a YBCO thick film deposited on a flexible substrate, typically with an intermediate buffer layer, and an overcoat of noble metal. In this process, the interm… 相似文献
52.
通过重离子核反应与在束γ谱的实验技术, 对A=130缺中子核区的双奇核136La的高自旋态进行了研究, 所用核反应为130Te(11B,5n). 实验结果扩展了136La的能级纲图, 包括3个集体转动带, 最高自旋态达20h. 对于\uppi h_{11/2}\otimes \upnu h_{11/2}$~带, 观测到了旋称反转与集体回弯现象. 通过系统学比较, 对旋称反转特性进行了讨论. 由推转壳模型的计算指出, 此集体回弯是由一对中子的角动量顺排引起的. 另外两个集体带为具有~$\gamma\approx -60^\circ$~的扁椭形变带, 其可能的组态为: $\uppi h_{11/2}\otimes \upnu g_{7/2}h_{11/2}^2$~与~$\uppi g_{7/2}\otimes\upnu g_{7/2}^2 d_{5/2} h_{11/2}^2$. 相似文献
53.
Yan WANG Rong Quan FENG 《数学学报(英文版)》2005,21(4):773-778
A Cayley map is a Cayley graph embedded in an orientable surface such that. the local rotations at every vertex are identical. In this paper, balanced regular Cayley maps for cyclic groups, dihedral groups, and generalized quaternion groups are classified. 相似文献
54.
Oriented 2-factorable graphs are reduced to bouquets by permutation voltage assignment in this paper. Introducing the concept ofk-class index of a permutation group, various oriented 2-factorable graphs are enumerated in this paper. 相似文献
55.
56.
Nanograins are characterized by a typical grain size from lto 100 nm.Mclecular dynamics aimubations have been carried out for the nanograin sphere with the diameters from 1.45 to 10.12 nm.We study the influence of grain size on structure and diffusion properties of the nanograins.The results reveal that as the grain size is reduced,the fraction of grain surface increases significantly,and the surface width is approximately constant;the diffusicn coefficlent is increased sharply,and the relation of the diffusion coefficient and the grain size is close to exponential relation below 10nm. 相似文献
57.
58.
Resistivity-temperature characteristics of sol gel YBa2Cu3Oy samples synthesized in flowing oxygen atmosphere 下载免费PDF全文
The relationship of resistivity versus synthesizing temperature of sol gel YBa_2Cu_3O_y samples was studied when prepared under flowing oxygen conditions. A set of high-temperature ρ-T curves was obtained for the whole process. After the sample finished the test measuring, its resistivity was ρ_{300}=9.83×10^{-3 }Ω·cm at room temperature. The ρ-T curve also showed that the orthorhombic-tetragonal phase transformation of sol-gel YBa_2Cu_3O_y sample occurred at 581℃ for the sample in the rising temperature process, but at 613℃ in the cooling process, lower than that of the samples made by using the conventional powder metallurgy methods. 相似文献
59.
In this paper, we use weighted modules ω(?)(f,t)w to study the pointwise approximation on Szasz-type operators, and obtain the direct and converse theorem, as well as characterizations of the pointwise approximation of Jacobi-weighted Szasz-type operators. 相似文献
60.
Current methodologies used for the inference of thin film stress through curvature measurement are strictly restricted to stress and curvature states that are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to a single layer of thin film deposited on a substrate subjected to the non-uniform misfit strain in the thin film. Such methodologies are further extended to multi-layer thin films deposited on a substrate in the present study. Each thin film may have its own non-uniform misfit strain. We derive relations between the stresses in each thin film and the change of system curvatures due to the deposition of each thin film. The interface shear stresses between the adjacent films and between the thin film and the substrate are also obtained from the system curvatures. This provides the basis for the experimental determination of thin film stresses in multi-layer thin films on a substrate. 相似文献