全文获取类型
收费全文 | 307628篇 |
免费 | 2936篇 |
国内免费 | 1014篇 |
专业分类
化学 | 160805篇 |
晶体学 | 5106篇 |
力学 | 13569篇 |
综合类 | 10篇 |
数学 | 33519篇 |
物理学 | 98569篇 |
出版年
2020年 | 2380篇 |
2019年 | 2539篇 |
2018年 | 3236篇 |
2017年 | 3092篇 |
2016年 | 4867篇 |
2015年 | 3165篇 |
2014年 | 4738篇 |
2013年 | 13172篇 |
2012年 | 10035篇 |
2011年 | 12309篇 |
2010年 | 8281篇 |
2009年 | 7994篇 |
2008年 | 11114篇 |
2007年 | 11260篇 |
2006年 | 10947篇 |
2005年 | 10031篇 |
2004年 | 9191篇 |
2003年 | 8192篇 |
2002年 | 7977篇 |
2001年 | 9077篇 |
2000年 | 7037篇 |
1999年 | 5519篇 |
1998年 | 4544篇 |
1997年 | 4550篇 |
1996年 | 4273篇 |
1995年 | 4074篇 |
1994年 | 3721篇 |
1993年 | 3632篇 |
1992年 | 4119篇 |
1991年 | 4058篇 |
1990年 | 3968篇 |
1989年 | 3773篇 |
1988年 | 3828篇 |
1987年 | 3821篇 |
1986年 | 3573篇 |
1985年 | 4755篇 |
1984年 | 5055篇 |
1983年 | 4208篇 |
1982年 | 4597篇 |
1981年 | 4420篇 |
1980年 | 4324篇 |
1979年 | 4425篇 |
1978年 | 4603篇 |
1977年 | 4550篇 |
1976年 | 4635篇 |
1975年 | 4364篇 |
1974年 | 4227篇 |
1973年 | 4510篇 |
1972年 | 2862篇 |
1971年 | 2203篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
132.
133.
Arthur W. Apter 《Mathematical Logic Quarterly》2006,52(5):457-463
We construct models for the level by level equivalence between strong compactness and supercompactness in which for κ the least supercompact cardinal and δ ≤ κ any cardinal which is either a strong cardinal or a measurable limit of strong cardinals, 2δ > δ + and δ is < 2δ supercompact. In these models, the structure of the class of supercompact cardinals can be arbitrary, and the size of the power set of κ can essentially be made as large as desired. This extends and generalizes [5, Theorem 2] and [4, Theorem 4]. We also sketch how our techniques can be used to establish a weak indestructibility result. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
134.
A. D. English 《Journal of Polymer Science.Polymer Physics》1986,24(4):805-815
NMR spectroscopy has been used to characterize poly(p-phenylene terephthalamide) in the solid state and in solution in sulfuric acid. Solid-state 13C NMR spectra illustrate that the chain structure is highly ordered in the solid state and is of lower symmetry than in solution. Solid-state 13C and 1H NMR results show that only very limited motion takes place over the temperature range of ?170 to +200°C. High-resolution NMR spectra can be observed only in very dilute isotropic solutions because it is the overall rotational motion of the polymer, not segmental motion, that averages the nuclear spin interactions to their isotropic values. These results demonstrate that previous solution NMR studies that were interpreted as reflecting the presence of isotropic and anisotropic high-molecular-weight polymer phases over a wide range of concentrations actually are representative of polymer degradation. 相似文献
135.
使用美国甚大天线阵(VLA).对Markarian 8星系进行了多频观测.多频VLA观测表明,Markarian 8星系有三个主要的射电子成份,它们浸在一个弥漫的星系包层中.包层的射电谱是陡的非热谱.本文根据VLA观测确定了包层的物理参量,并讨论了包层中相对论性电子的可能起因.本文估计了包层非热辐射所要求的超新星爆发率. 相似文献
136.
M. D. Warren 《国际流体数值方法杂志》1983,3(3):217-225
This paper derives the convection–diffusion-reaction equation governing the reaction between the dissolved oxygen in sea-water and the steel walls of a pulsating crack. By the neglect of the diffusion term it is shown that an exact solution of the convection-reaction equation can be obtained. A numerical method for the solution of the complete convection–diffusion-reaction equation is derived by the use of finite differences. The numerical computation of the initial transient and the final periodic steady-state values is also discussed. 相似文献
137.
138.
Binding energy spectra of the valence electrons of the open shell molecule NO have been obtained up to 55 eV at azimuthal angles of 0° and 7° using binary (e, 2e) spectroscopy at an impact energy of 1200 eV. The momentum distribution has been obtained for the least tightly bound (unpaired) electron, removal of which leads to formation of the X 1Σ+ ground state of NO+. Momentum distributions have also been measured at 21.0 and 40.5 eV. The measured momentum distributions are compared with several literature wavefunctions of varying complexity. They are found to be in excellent agreement with those calculated using the natural spin orbital wavefunctions of Kouba and Ohrn. 相似文献
139.
140.
本文讨论圆形区域内芽虫分布模型,特别研究了芽虫与天敌接触时产生与避免outbreak状态的可能性。 相似文献