全文获取类型
收费全文 | 87848篇 |
免费 | 1062篇 |
国内免费 | 240篇 |
专业分类
化学 | 48409篇 |
晶体学 | 1355篇 |
力学 | 3779篇 |
综合类 | 4篇 |
数学 | 9139篇 |
物理学 | 26464篇 |
出版年
2022年 | 827篇 |
2021年 | 1303篇 |
2020年 | 1331篇 |
2019年 | 1547篇 |
2018年 | 2049篇 |
2017年 | 2056篇 |
2016年 | 2764篇 |
2015年 | 1446篇 |
2014年 | 2292篇 |
2013年 | 4344篇 |
2012年 | 3720篇 |
2011年 | 4051篇 |
2010年 | 3205篇 |
2009年 | 3095篇 |
2008年 | 3505篇 |
2007年 | 3323篇 |
2006年 | 3086篇 |
2005年 | 2758篇 |
2004年 | 2436篇 |
2003年 | 2266篇 |
2002年 | 2301篇 |
2001年 | 2319篇 |
2000年 | 1680篇 |
1999年 | 1318篇 |
1998年 | 1167篇 |
1997年 | 1088篇 |
1996年 | 938篇 |
1995年 | 866篇 |
1994年 | 851篇 |
1993年 | 831篇 |
1992年 | 901篇 |
1991年 | 965篇 |
1990年 | 908篇 |
1989年 | 940篇 |
1988年 | 849篇 |
1987年 | 800篇 |
1986年 | 767篇 |
1985年 | 900篇 |
1984年 | 997篇 |
1983年 | 839篇 |
1982年 | 861篇 |
1981年 | 765篇 |
1980年 | 724篇 |
1979年 | 788篇 |
1978年 | 908篇 |
1977年 | 923篇 |
1976年 | 823篇 |
1975年 | 786篇 |
1974年 | 806篇 |
1973年 | 771篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
151.
Times of longitudinal T
1b
and transverse T
2b
magnetic relaxation of hexane and decane molecules in micropores of ZSM-5 silicalite were measured as functions of the content of these liquid n-alkanes in zeolite and of temperature. The stepwise changes in the T
1b
and T
2b
times were revealed in the region of 8% content of hydrocarbons. The observed changes in the concentration and temperature dependences of T
1b
and T
2b
times are explained by the rearrangement of silicalite crystal lattice under the action of adsorbed molecules. 相似文献
152.
We solve the de la Vallée Poussin problem for a functional-differential equation by the projection-iterative method. We construct an algorithm, establish conditions sufficient for the convergence of the method, and present a computational scheme. 相似文献
153.
A 2D HgII coordination polymer containing ligands 1,2,4‐triazole (Htrz) and thiocyanate, [Hg(μ3‐trz)(SCN)]n ( 1 ) has been synthesized and characterized by elemental analysis and IR spectroscopy. The single‐crystal X‐ray data show the coordination number of Hg atoms is four and the ligand trz? acts as a three‐fold donor. The thermal stability of compound 1 was studied by thermal gravimetric and differential thermal analyses. The composition and formation of the complex in methanol solution were found to be in support of its solid state structure. 相似文献
154.
The composite comprised of zinc oxide quantum dots and poly(amic acid) (PAAc) was prepared and studied by X-rays diffraction, X-ray photoelectron spectroscopy, light scattering, UV absorbance and UV fluorescence. The UV absorbance of the ZnO/PAAc composite was found to be much larger than that of its components taken separately. The fluorescence of the ZnO/PAAc composite was found to be shifted to longer wavelengthes in comparison with pure ZnO. The presence of the dopant dodecylbenzenesulfonic acid was found to affect the observed fluorescence. 相似文献
155.
O. Hölder 《Mathematische Annalen》1886,28(1):1-13
Ohne Zusammenfassung 相似文献
156.
157.
158.
Mohammed Ali Faya Ibrahim 《Czechoslovak Mathematical Journal》2004,54(2):303-313
It was shown in [7] that any right reversible, cancellative ordered semigroup can be embedded into an ordered group and as a consequence, it was shown that a commutative ordered semigroup can be embedded into an ordered group if and only if it is cancellative. In this paper we introduce the concept of L-maher and R-maher semigroups and use a technique similar to that used in [7] to show that any left reversible cancellative ordered L or R-maher semigroup can be embedded into an ordered group. 相似文献
159.
O. V. Koryakova V. V. Sattarova D. V. Sevenard O. G. Khomutov K. I. Pashkevich 《Russian Journal of General Chemistry》2003,73(1):141-144
The tautomeric equilibrium in substituted 5,6,7,8-tetrahydroquinazolines was studied by IR spectroscopy. The effect of various substitutents in the pyrimidine ring and the solvent on the state of the tautomeric equilibrium was evaluated. 相似文献
160.
O. Castaños 《Journal of Molecular Spectroscopy》2007,241(1):51-60
A simple algebraic approach to calculate general Franck-Condon overlaps is extended to evaluate non-Condon factors for two one-dimensional harmonic oscillators. The method is based on the use of eigenstates of the harmonic oscillator annihilation operator which allows to obtain in terms of a multi-dimensional Hermite polynomial the overlap of harmonic oscillator functions associated with different Born-Oppenheimer potentials. The presented approach is self-contained, only basic concepts of quantum mechanics associated with the harmonic oscillator system are needed. The obtained expression for the Franck-Condon overlaps is similar to the Ansbacher’s formula and equivalent to the one calculated by Malkin and Man’ko. However our final expression has the advantages that only real numbers are involved and it is straightforward to get the limit case of equal frequencies. Concerning the non-Condon factors two approaches leading to different formulas are considered, both of which reduce to triple sums of products of three Hermite polynomials. 相似文献