全文获取类型
收费全文 | 9872篇 |
免费 | 2119篇 |
国内免费 | 1672篇 |
专业分类
化学 | 5036篇 |
晶体学 | 99篇 |
力学 | 595篇 |
综合类 | 117篇 |
数学 | 1168篇 |
物理学 | 6648篇 |
出版年
2024年 | 14篇 |
2023年 | 93篇 |
2022年 | 206篇 |
2021年 | 227篇 |
2020年 | 289篇 |
2019年 | 210篇 |
2018年 | 217篇 |
2017年 | 261篇 |
2016年 | 324篇 |
2015年 | 393篇 |
2014年 | 531篇 |
2013年 | 782篇 |
2012年 | 589篇 |
2011年 | 735篇 |
2010年 | 655篇 |
2009年 | 744篇 |
2008年 | 792篇 |
2007年 | 812篇 |
2006年 | 709篇 |
2005年 | 656篇 |
2004年 | 488篇 |
2003年 | 542篇 |
2002年 | 481篇 |
2001年 | 399篇 |
2000年 | 377篇 |
1999年 | 357篇 |
1998年 | 279篇 |
1997年 | 234篇 |
1996年 | 206篇 |
1995年 | 153篇 |
1994年 | 155篇 |
1993年 | 111篇 |
1992年 | 111篇 |
1991年 | 94篇 |
1990年 | 49篇 |
1989年 | 71篇 |
1988年 | 43篇 |
1987年 | 42篇 |
1986年 | 20篇 |
1985年 | 48篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 33篇 |
1981年 | 17篇 |
1980年 | 10篇 |
1979年 | 14篇 |
1977年 | 7篇 |
1976年 | 10篇 |
1974年 | 4篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
81.
P. E. M. Siegbahn 《Theoretical chemistry accounts》1994,88(6):413-424
Summary The ground state structures and bond energies have been obtained for the triatomic MHX systems where M is the entire sequence of second row transition metal atoms and X is a halide. The most interesting results of this study appear when these systems are compared to the triatomic MH2 and MX2 systems. It turns out that the structure of the MHX systems are quite similar to the corresponding MH2 systems in general. Most of the MHX systems to the right thus have bent low-spin ground states, indicating large covalent contributions to the bonding. RuHX is a special case and has a high-spin linear ground state. For the systems to the left ionicity dominates the bonding. An important result, with implications for halide ligand effects on carbonyl and olefin insertion into M-H and M-R bonds, is that the M-H bonds for the systems to the right have a different character and are significantly weaker for the MHX than for the MH2 systems. A similar effect is noted when the M-Cl bond strengths of MCl2 are compared to the ones in MHCl. Both these effects can be explained by a more cationic metal with mores
0-state character when halide ligands are present. 相似文献
82.
王守宇 马英君 T.Komatsubara 刘运祚 张玉虎 梁国栋 K.Furuno T.Hayakawa J.Mukai Y.Iwata T.Morikawa G.B.Hagcmann G.Sletten J.Nyberg D.Je 《中国物理 C》2004,28(5):491-494
利用融合蒸发反应116Cd(14N,4n)126Cs布居了126Cs的高自旋态.观测到了100多条新的γ跃迁和相应的能级,建立了双奇核126Cs由9个转动带构成的能级纲图.尝试性地指定了大部分能级的自旋和宇称以及各转动带的Nilsson单粒子组态.极大地丰富了已有的实验结果. 相似文献
83.
The question about the definition of the “internal pressure” concept is being discussed. It is shown that the previously found differential relation between the cohesion energy density and the internal pressure is one of the examples of an absolutely general interrelation between definitely connected differential functions. It is ascertained that the ratio (the internal pressure divided by the cohesion energy density) is a structuresensitive parameter inherent to the calorific (thermal) equation of a liquid state. 相似文献
84.
Sergey P. Gladchenko Yurii Z. Kovdrya Viktor A. Nikolaenko 《Journal of Molecular Liquids》2005,120(1-3):175-179
Conductivity of electrons in a quasi-one-dimensional (Q1D) system over liquid helium in narrow channels with the parabolic profile of the potential well has been investigated at temperature T, from 0.4 to 1.8 K, for different driving electric fields and radius of channel curvature. The interval of linear electron densities varied from 2.18×103 up to 1.7×106 cm−1.
The inverse mobility (1/μeff) in the electron-ripplon scattering region at the high linear densities of charges in the channel increases with temperature decreasing. This anomalous behavior of the electron transport in the low-temperature region has been explained by either the electron ordering or the polaronic effects in confined conducting channels. The nonlinear behavior of the electron velocity as a function of a driving electric field is supposed to be due to Breg–Cherenkov radiation of the ripplons. The radiation occurred if the velocity of electrons in the channel approaches to the critical value. 相似文献
85.
本文提出一种利用材料Hugoniot数据研究高压下离子晶体中微观离子状态及其离子间排斥作用势的新方法。对氢化锂晶体进行研究时,我们得到Li~+和H~-离子之间排斥作用势函数,结果表明文献〔1〕中提出的离子压缩效应具有客观性。 相似文献
86.
87.
88.
Nadya Dencheva Teresa G. Nunes M. Jovita Oliveira Zlatan Denchev 《Journal of Polymer Science.Polymer Physics》2005,43(24):3720-3733
The crystalline structure of polyamide‐12 (PA12) was studied by solid‐state 13C nuclear magnetic resonance (NMR) as well as by synchrotron wide‐ and small‐angle X‐ray scattering (WAXS and SAXS). Isotropic and oriented PA12 showed different NMR spectra ascribed to γ‐ and γ′‐crystalline modifications, respectively. On the basis of the position of the first diffraction peak, the isotropic γ‐form and the oriented γ′‐form were shown to be with hexagonal crystalline lattice at room temperature. When heated, the two PA12 polymorphs demonstrated different behaviors. Above 140 °C, the isotropic γ‐PA12 partially transformed into α‐modification. No such transition was observed with the oriented γ′‐PA12 phase even after annealing at temperatures close to melting. A γ′–γ transition was observed here only after isotropization by melting point. Various structural parameters were extracted from the WAXS and SAXS patterns and analyzed as a function of temperature and orientation: the degree of crystallinity, the d‐spacings, the Bragg's long spacings, the average thicknesses of the crystalline (lc) and amorphous (la) phases, and the linear crystallinity xcl within the lamellar stacks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3720–3733, 2005 相似文献
89.
We have studied the temperature dependence of the radiative deactivation of the Pd-porphine triplet states in Shpol’skii matrices
in the temperature range 1.2–210 K. A substantial transformation of the phosphorescence spectra is observed as the temperature
increases and is due to the inclusion of thermally activated Pd-porphine states in the radiative deactivation processes. The
activation energy Ea of these Pd-porphine states is measured in matrices of n-octane and n-nonane. The splitting of the lowest quasidegenerate
triplet state ΔE(T2−T1) is determined for planar and distorted conformations of the Pd-porphine macrocycle in the n-octane matrix as 40 and 57 cm−1, respectively. The ability to use the temperature dependence of the phosphorescence properties of Pd-porphine to fabricate
molecular thermometers for the low-temperature range is analyzed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 460–464, July–August, 2007. 相似文献
90.
LIANG Liang 《原子与分子物理学报》2003,20(4):575-578
By using the multichannel quantum defect theory(MQDT),we have evaluated the energy levels and lifetimes of 2sns ^3 S1,2snd ^3D(n=3-25)of BeI and 1 sns ^3s1,1snd ^3D(n=3-25)of BeⅢ,These energies and lifetimes that we have calculated not only agree with the recent measurements and theoretical calculation of Ref.4 and Ref.3, but also predict the lifetimes of 66 other highly excited states. 相似文献