全文获取类型
收费全文 | 8127篇 |
免费 | 365篇 |
国内免费 | 37篇 |
专业分类
化学 | 5687篇 |
晶体学 | 20篇 |
力学 | 203篇 |
数学 | 1398篇 |
物理学 | 1221篇 |
出版年
2023年 | 77篇 |
2022年 | 112篇 |
2021年 | 135篇 |
2020年 | 189篇 |
2019年 | 190篇 |
2018年 | 115篇 |
2017年 | 115篇 |
2016年 | 357篇 |
2015年 | 314篇 |
2014年 | 296篇 |
2013年 | 472篇 |
2012年 | 554篇 |
2011年 | 652篇 |
2010年 | 378篇 |
2009年 | 321篇 |
2008年 | 515篇 |
2007年 | 462篇 |
2006年 | 438篇 |
2005年 | 409篇 |
2004年 | 347篇 |
2003年 | 315篇 |
2002年 | 288篇 |
2001年 | 169篇 |
2000年 | 122篇 |
1999年 | 120篇 |
1998年 | 93篇 |
1997年 | 102篇 |
1996年 | 103篇 |
1995年 | 85篇 |
1994年 | 59篇 |
1993年 | 62篇 |
1992年 | 53篇 |
1991年 | 35篇 |
1990年 | 36篇 |
1989年 | 29篇 |
1988年 | 34篇 |
1987年 | 26篇 |
1986年 | 31篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 14篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 21篇 |
1977年 | 13篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1970年 | 8篇 |
排序方式: 共有8529条查询结果,搜索用时 0 毫秒
991.
J. Henrique Teles Johann-Peter Melder Klaus Ebel Regina Schneider Eugen Gehrer Wolfgang Harder Stefan Brode Dieter Enders Klaus Breuer Gerhard Raabe 《Helvetica chimica acta》1996,79(1):61-83
Stable carbenes derived from thiazole, 1H-imidazole, and 4H-1,2,4-triazole are efficient catalysts for benzointype condensations of formaldehyde. Catalysts derived from N-substituted thiazolium salts trimerize formaldehyde to dihydroxyacetone ( II ). Catalysts based on 1,4-disubstituted 4H-1,2,4-triazol-1-ium salts give glycolaldehyde ( I ) as the main product and no II , whereas N,N′-disubstituted 1H-imidazol-3-ium salts yield mixtures of both products. The isolation of several intermediates in the catalytic cycle provide a better insight into the reaction mechanism. 相似文献
992.
Stefan E. Schmidt 《Results in Mathematics》1993,23(3-4):384-386
This note presents a proof of Wedderburn’s theorem concerning the classification of semisimple rings within the conceptual frame of projective lattice geometry. 相似文献
993.
The vinylation of 9H-carbazole ( 1 ), 1H-indole ( 3a ), and 1H-pyrrolo[2,3-b]pyridine ( 3b ) with propiolic acid ethyl ester resulting in N-acrylic esters is reported here. 相似文献
994.
Stefan Wojciechowski 《Reports on Mathematical Physics》1975,8(3):387-390
The relation between the geometry and the statistics of the quantum theory is most explicit in the convex models of quantum mechanics. A class of models is investigated where the manifold S of all states is a convex set with a smooth boundary. It is shown that for these models the simple assumption about symmetry of the transition probability implies an ellipsoidal shape of S, thus leading to the “spherical” geometries described in [7]. 相似文献
995.
If S is an arbitrary sequence of positive integers, let P(S) be the set of all integers which are representable as a sum of distinct terms of S. Call S complete if P(S) contains all large integers, and subcomplete if P(S) contains an infinite arithmetic progression. It is shown that any sequence can be perturbed in a rather moderate way into a sequence which is not subcomplete. On the other hand, it is shown that if S is any sequence satisfying a mild growth condition, then a surprisingly gentle perturbation suffices to make S complete in a strong sense. Various related questions are also considered. 相似文献
996.
997.
Stefan Marinov 《Foundations of Physics》1979,9(5-6):445-460
In the light of our recently performed experiments, revealing the anisotropy of light velocity in any frame moving with respect to absolute space, we show that the Lorentz transformation, where the relativity of light velocity is given implicitly through the relativity of the time coordinates, must be treated from an absolute point of view if one seeks to preserve its adequacy to physical reality. Then we propose a new transformation (which is to be considered as a legitimate companion of the Lorentz transformation) wherein the relativity of light velocity is given explicitly and the time coordinates are absolute. 相似文献
998.
Stefan Berger 《Magnetic resonance in chemistry : MRC》1980,14(1):65-68
A series of alicyclic compounds with dihedral angles of 0°, 60°, 90°, 120° and 180° between a 13C-labelled carbon atom and a carbon atom separated by three bonds from the label has been synthesized. The vicinal 13C13C spin coupling constants were measured, and from the results a Karplus-type relationship between 13C13C spin coupling and dihedral angle is proposed. 相似文献
999.
1000.