全文获取类型
收费全文 | 3045篇 |
免费 | 540篇 |
国内免费 | 471篇 |
专业分类
化学 | 2254篇 |
晶体学 | 46篇 |
力学 | 134篇 |
综合类 | 44篇 |
数学 | 311篇 |
物理学 | 1267篇 |
出版年
2024年 | 13篇 |
2023年 | 80篇 |
2022年 | 160篇 |
2021年 | 147篇 |
2020年 | 176篇 |
2019年 | 166篇 |
2018年 | 159篇 |
2017年 | 155篇 |
2016年 | 180篇 |
2015年 | 194篇 |
2014年 | 192篇 |
2013年 | 237篇 |
2012年 | 240篇 |
2011年 | 272篇 |
2010年 | 198篇 |
2009年 | 191篇 |
2008年 | 193篇 |
2007年 | 140篇 |
2006年 | 129篇 |
2005年 | 92篇 |
2004年 | 84篇 |
2003年 | 93篇 |
2002年 | 74篇 |
2001年 | 70篇 |
2000年 | 51篇 |
1999年 | 57篇 |
1998年 | 62篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 30篇 |
1994年 | 25篇 |
1993年 | 21篇 |
1992年 | 15篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1968年 | 1篇 |
1957年 | 1篇 |
1936年 | 3篇 |
排序方式: 共有4056条查询结果,搜索用时 156 毫秒
21.
22.
The Hamiltonian formulation of the usual complex quantum mechanics in the theory of generalized quantum dynamics is discussed.
After the total trace Lagrangian, total trace Hamiltonian and two kinds of Poisson brackets are introduced, both the equations
of motion of some total trace functionals which are expressed by total trace Poisson brackets and the equations of motion
of some operators which are expressed by the without-total-trace Poisson brackets are obtained. Then a set of basic equations
of motion of the usual complex quantum mechanics are obtained, which are also expressed by the Poisson brackets and total
trace Hamiltonian in the generalized quantum dynamics. The set of equations of motion are consistent with the corresponding
Heisenberg equations.
Project supported by Prof. T.D. Lee’s NNSC Grant, the National Natural Science Foundation of China, the Foundation of Ph.
D. Directing Programme of Chinese University, and the Chinese Academy of Sciences. 相似文献
23.
The structures and stabilities of these still experimentally unknown CH_nCl_(3-n)O_(2-)Li~ and CF_nCl_(3-n)O_(2-)Li~ ionshave been theoretically investigated by ab initio molecular orbital theory and density functional theory(DFT)inconjunction with the 6-311G(d,p),6-311 G(d,p),6-311 G(2d,p)and 6-311 G(2df,2p)basis sets.The optimizedgeometries,chemical bonding and NBO analysis indicate that these complexes of CH_nCl_(3-n)O_(2-)Li~ and CF_nCl_(3-n)O_(2-)Li~ exist as ion-dipole molecules.The calculated affinity energies of these species exceed 41.9 kJ/mol,which arelarge enough to suggest the possibility that these title complexes could be detected as stable species in gas phase byLi~ ion attachment mass spectrometry. 相似文献
24.
JianXinPU JingFengZHAO XiaoDongYANG ShuangXiMEI HongBinZHANG LiangLI 《中国化学快报》2004,15(12):1454-1456
A new sesquiterpene lactone, Ainsliaolide A, was isolated from Ainsliaea bonatii. The structure was determined on the basis of spectral data. 相似文献
25.
26.
27.
28.
Shuang‐Jun Lin Chang‐Heng Tan Shan‐Hao Jiang Yi‐Ming Li Da‐Yuan Zhu 《Helvetica chimica acta》2006,89(11):2789-2793
Four new iridoids, buergerinins B–E ( 1 – 4 ), along with three known iridoids, were isolated from the roots of Scrophularia buergeriana. Their structures were identified on the basis of spectroscopic analysis. 相似文献
29.
TEM investigation of formation mechanism of monocrystal-thick b-oriented pure silica zeolite MFI film 总被引:3,自引:0,他引:3
Li S Li Z Bozhilov KN Chen Z Yan Y 《Journal of the American Chemical Society》2004,126(34):10732-10737
The first direct transmission electron microscopic (TEM) observation has been carried out on the continuous monocrystal-thick b-oriented pure silica zeolite MFI films produced by in situ crystallization. The self-supporting film samples for TEM study were fabricated by dissolving the steel substrate with acid. This TEM study is free of those artifacts that are typically associated with TEM sample preparations, and allows us to investigate the "true" structure and texture of a very large area of the film and at the same time to focus at will on each individual zeolite crystal in the film. Abundant TEM information including crystallographic orientation relationships among crystals in the film (both out-of-plane and in-plane), grain boundaries, and each crystal grain was obtained. This TEM investigation provides direct unambiguous new evidence to support the homogeneous nucleation mechanism, by which the films form through homogeneous nucleation and crystal growth in the bulk to form equal-sized disk-shape crystals, followed by self-assembly of these crystals onto the substrate to produce a two-dimensional close-packed structure. The last stage of the film formation involves simultaneous space-limited growth and rotation of the individual crystals to realize the in-plane crystallographic control within the film. 相似文献
30.