全文获取类型
收费全文 | 4271篇 |
免费 | 727篇 |
国内免费 | 358篇 |
专业分类
化学 | 2832篇 |
晶体学 | 57篇 |
力学 | 308篇 |
综合类 | 22篇 |
数学 | 443篇 |
物理学 | 1694篇 |
出版年
2024年 | 9篇 |
2023年 | 114篇 |
2022年 | 93篇 |
2021年 | 163篇 |
2020年 | 177篇 |
2019年 | 168篇 |
2018年 | 164篇 |
2017年 | 130篇 |
2016年 | 236篇 |
2015年 | 201篇 |
2014年 | 243篇 |
2013年 | 324篇 |
2012年 | 403篇 |
2011年 | 421篇 |
2010年 | 278篇 |
2009年 | 253篇 |
2008年 | 262篇 |
2007年 | 251篇 |
2006年 | 236篇 |
2005年 | 185篇 |
2004年 | 140篇 |
2003年 | 108篇 |
2002年 | 87篇 |
2001年 | 76篇 |
2000年 | 87篇 |
1999年 | 75篇 |
1998年 | 69篇 |
1997年 | 57篇 |
1996年 | 65篇 |
1995年 | 53篇 |
1994年 | 29篇 |
1993年 | 45篇 |
1992年 | 42篇 |
1991年 | 25篇 |
1990年 | 23篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 1篇 |
1983年 | 6篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有5356条查询结果,搜索用时 250 毫秒
991.
Spectroscopic analysis of asymmetric top free radicals 总被引:1,自引:0,他引:1
Yuyan Liu Xiaoyong Liu Hongping Liu Yuanqing Guo Guangming Huang Jieli Lin Hui Gao Chuanxi Duan 《中国科学B辑(英文版)》2001,44(1):7-16
Several key problems involved in the analyses of spectra of asymmetric top molecules, i.e., the effective Hamiltonian, the
representation and basis vector, identification of energy levels, the selection rules, the relative intensity, and Zeeman
tuning rate, were elucidated systematically. Introducing the high-order centrifugal distortion terms into the effective Hamiltonian,
the precision for calculation has been improved substantially, which allows us to analyze the high-lying rotational transitions.
A global analysis of all available spectra of14N16O2 in the ground vibronic state has been made to obtain a set of molecular constants of14N16O2 in the ground vibronic state which is the most precise and extensive so far. Using the improved parameters, some FIR LMR
lines left unassigned hitherto have been identified successfully. 相似文献
992.
Ren Xiaoming Duan Chunying Zhu Huizhen Meng Qingjin Hu Chuanjiang Lu Changsheng Liu Yongjiang 《Transition Metal Chemistry》2001,26(3):295-299
Interesting complexes containing a mnt2– bridge, based on the reaction of [M(mnt)2]2– [M = Ni or Cu] with [Cu(LH)]+, have been prepared and characterized by e.s.m.s., i.r and u.v–vis. spectroscopic techniques and by electrochemistry. The complexes show weak antiferromagnetic interactions between magnetic centers. The X-ray analysis of the molecular structure of [Cu(LH)]2[Ni(mnt)2] has been completed. It structurally features the CN group of mnt2– which can act as a bridging ligand between two transition metals. 相似文献
993.
994.
用分子图形学方法设计出26种P10模型,并对其进行了分子力学、PM3半经验量子化学和Hartree-Fock从头算优化。在P10原子团簇模型设计中,磷原子采用一、二、三或四配位。大部分P10的模型是在P9+和P8的模型上分别增加1、2个原子生成的。这些模型包括15种在势能面上局域极小点和11种鞍点(或过渡态)。从模型优化后的能量比较可知,2个四面体P4与1个P2通过4个单键连接的桥式结构最稳定。从最稳定楔状P8可以派生多种构型,其中有一种的能量也相当低。由正四面体P4和楔状P8派生出的结构具有能量优势,它们是构造大分子磷原子团簇的重要的结构基元。在模型几何优化中,得到了带有2个一配位原子的特殊结构,它含有2个三键(1.95A)。 相似文献
995.
The problem of a Griffith crack in an unbounded orthotropic functionally graded material subjected to antipole shear impact was studied. The shear moduli in two directions of the functionally graded material were assumed to vary proportionately as definite gradient. By using integral transforms and dual integral equations, the local dynamic stress field was obtained. The results of dynamic stress intensity factor show that increasing shear moduli’s gradient of FGM or increasing the shear modulus in direction perpendicular to crack surface can restrain the magnitude of dynamic stress intensity factor. 相似文献
996.
4th-order spline wavelets on a bounded interval 总被引:1,自引:0,他引:1
IntroductionWaveletanalysishasexperiencedanenormousdevelopmentinrecentyears.Oneoftheimportantfieldsisthenumericalanalysisofdifferentialequations.Theadvantageofadoptingwaveletshasbeenreported[1~ 4].Classicalapproachestowaveletconstructiondealwithmultireso… 相似文献
997.
998.
999.
D. Y. Pan D. R. Yuan H. Q. Sun S. Y. Guo X. Q. Wang X. L. Duan C. N. Luan Z. F. Li 《Crystal Research and Technology》2006,41(3):236-238
A study of growth of barium hydrogen phosphate (BaHPO4) crystal from solution is reported. The raw materials of barium hydrogen phosphate were successfully synthesized through chemical reaction in water. The solubility in HCl and H3PO4 solution were studied. It increased when acid concentration and temperature become higher, and the fitted curve of solubility is nearly a line. The acid concentration affects crystalline morphology of BaHPO4 crystal. The crystallization is well when the acid solution ranges from 0.5 to 0.8M. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
1000.
In this paper, the Fisher equation is analysed. One of its travelling wave solution
is obtained by comparing it with KdV--Burgers (KdVB) equation. Its amplitude, width
and speed are investigated. The instability for the higher order disturbances to the
solution of the Fisher equation is also studied. 相似文献