全文获取类型
收费全文 | 3339篇 |
免费 | 91篇 |
国内免费 | 8篇 |
专业分类
化学 | 2275篇 |
晶体学 | 11篇 |
力学 | 33篇 |
数学 | 638篇 |
物理学 | 481篇 |
出版年
2021年 | 29篇 |
2020年 | 36篇 |
2019年 | 38篇 |
2018年 | 26篇 |
2017年 | 20篇 |
2016年 | 68篇 |
2015年 | 75篇 |
2014年 | 70篇 |
2013年 | 116篇 |
2012年 | 138篇 |
2011年 | 146篇 |
2010年 | 93篇 |
2009年 | 79篇 |
2008年 | 122篇 |
2007年 | 142篇 |
2006年 | 101篇 |
2005年 | 89篇 |
2004年 | 102篇 |
2003年 | 67篇 |
2002年 | 91篇 |
2001年 | 71篇 |
2000年 | 43篇 |
1999年 | 36篇 |
1998年 | 37篇 |
1997年 | 44篇 |
1996年 | 52篇 |
1995年 | 46篇 |
1994年 | 46篇 |
1993年 | 35篇 |
1992年 | 37篇 |
1991年 | 31篇 |
1990年 | 43篇 |
1989年 | 30篇 |
1988年 | 31篇 |
1987年 | 34篇 |
1985年 | 56篇 |
1984年 | 48篇 |
1983年 | 43篇 |
1982年 | 22篇 |
1981年 | 46篇 |
1980年 | 41篇 |
1979年 | 26篇 |
1978年 | 41篇 |
1977年 | 38篇 |
1976年 | 31篇 |
1975年 | 35篇 |
1974年 | 32篇 |
1973年 | 26篇 |
1971年 | 19篇 |
1960年 | 19篇 |
排序方式: 共有3438条查询结果,搜索用时 31 毫秒
21.
TorstenLinB 《计算数学(英文版)》2003,21(4):401-410
We consider a singularly perturbed semilinear convection-diffusion problem with a boundary layer of attractive turning-point type. It is shown that its solution can be decomposed into a regular solution component and a layer component. This decomposi-tion is used to analyse the convergence of an upwinded finite difference scheme on Shishkin meshes. 相似文献
22.
Oriňák Andrej Arlinghaus Heinrich Frank Vering Guido Justinová Martina Oriňáková Renáta Turčániová L’udmila Halama Maroš 《平面色谱法杂志一现代薄层色谱法》2003,16(1):23-27
JPC – Journal of Planar Chromatography – Modern TLC - Two interfaces have been tested for coupling thin-layer chromatography (TLC) with time-of-flight secondary-ion mass spectrometry... 相似文献
23.
We study a model linear convection-diffusion-reaction problem where both the diffusion term and the convection term are multiplied by small parameters εd and εc, respectively. Depending on the size of the parameters the solution of the problem may exhibit exponential layers at both end points of the domain. Sharp bounds for the derivatives of the solution are derived using a barrier-function technique. These bounds are applied in the analysis of a simple upwind-difference scheme on Shishkin meshes. This method is established to be almost first-order convergent, independently of the parameters εd and εc. 相似文献
24.
We consider a quadratic eigenvalue problem such that the second order term is a Hermitian matrix of rank r, the linear term is the identity matrix, and the constant term is an arbitrary Hermitian matrix
. Of the n+r solutions that this problem admits, we show at least n-r to be real and located in specific intervals defined by the eigenvalues of A, whence at most 2r are nonreal occuring in possibly repeated conjugate pairs. 相似文献
25.
26.
CuAl2Cl8. Preparation and Crystal Structure. Crystals of CuAl2Cl8 have been prepared. Their remission spectrum agrees with that of gaseous CuAl2Cl8. The crystal structure (P21/c;a = 6.614, b = 7.376, c = 12.319 Å; β = 94.11°) shows a molecular lattice with Cu in square planar coordination, which is completed to a stretched octahedron (as in solid CuCl2) by two Cl atoms from neighbour molecules. Al has tetrahedral coordination. 相似文献
27.
28.
Unusual Formation and Structure of a O‐Sulfinato Zinc Complex Whereas the reaction between hydrotris[(N‐xylyl)‐thioimidazolyl]borato‐zinc perchlorate ([ L· Zn‐OClO3]) and ethanethiolate under an inert atmosphere leads to the thiolate complex [ L· Zn‐SC2H5], the same reaction in air produces the sulfinato complex [ L· Zn‐O‐S(O)‐C2H5] ( 1 ). 1 is the first fully characterized sulfinato‐zinc complex. Its structure determination has confirmed the unusual coordination of the sulfinato ligand via one of its oxygen atoms. 相似文献
29.
Torsten Küppers Martin Köckerling Prof. Dr. Helge Willner Prof. Dr. 《无机化学与普通化学杂志》2007,633(2):280-284
The new tetracyanoborate K[B(CN)4]·CH3CN was synthesized by dissolution of the solvent‐free K[B(CN)4] in acetonitrile and subsequent careful crystallization. The crystal structure has been determined by single‐crystal X‐ray diffraction. It crystallizes in the orthorhombic space group P212121 with Z = 4. Some comparisons with related structures are made, and the vibrational spectrum is discussed. 相似文献
30.