全文获取类型
收费全文 | 22055篇 |
免费 | 641篇 |
国内免费 | 349篇 |
专业分类
化学 | 14310篇 |
晶体学 | 141篇 |
力学 | 597篇 |
综合类 | 30篇 |
数学 | 3028篇 |
物理学 | 4939篇 |
出版年
2023年 | 137篇 |
2022年 | 379篇 |
2021年 | 416篇 |
2020年 | 367篇 |
2019年 | 369篇 |
2018年 | 306篇 |
2017年 | 279篇 |
2016年 | 635篇 |
2015年 | 546篇 |
2014年 | 645篇 |
2013年 | 1156篇 |
2012年 | 1115篇 |
2011年 | 1323篇 |
2010年 | 885篇 |
2009年 | 798篇 |
2008年 | 1126篇 |
2007年 | 1165篇 |
2006年 | 988篇 |
2005年 | 953篇 |
2004年 | 920篇 |
2003年 | 842篇 |
2002年 | 836篇 |
2001年 | 525篇 |
2000年 | 475篇 |
1999年 | 396篇 |
1998年 | 277篇 |
1997年 | 257篇 |
1996年 | 304篇 |
1995年 | 290篇 |
1994年 | 286篇 |
1993年 | 219篇 |
1992年 | 222篇 |
1991年 | 216篇 |
1990年 | 216篇 |
1989年 | 178篇 |
1988年 | 152篇 |
1987年 | 153篇 |
1986年 | 141篇 |
1985年 | 242篇 |
1984年 | 253篇 |
1983年 | 182篇 |
1982年 | 195篇 |
1981年 | 162篇 |
1980年 | 169篇 |
1979年 | 157篇 |
1978年 | 116篇 |
1977年 | 172篇 |
1976年 | 148篇 |
1975年 | 122篇 |
1973年 | 115篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
11.
Zuo LIU Zhen De WU 《数学学报(英文版)》2005,21(5):997-1000
Let κ be non-negative integer. The unoriented bordism classes, which can be represented as [RP(ξ^κ)] where ξ^κ is a k-plane bundle, form an ideal of the unoriented bordism ring MO.. A group of generators of this ideal expressed by a base of MO. and a necessary and sufficient condition for a bordism class to belong to this ideal are given. 相似文献
12.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
13.
Michael De Castro 《Tetrahedron letters》2004,45(34):6501-6504
2-Deoxy-2-iodo-glycosylamides have been prepared from a variety of protected d-glucals by their reaction with N-iodosuccinimide and amides. Benzyl protected 2-iodoamides, when treated with sodium hydride and 15-crown-5, gave stable C1 N-linked 2-glycooxazolines as the major products. Silyl protected 2-iodoamides afforded the C1 O-linked 2-glycooxazolines; presumably by the rearrangement of unstable N-acylaziridine intermediates. 相似文献
14.
Emmanuel DardennesÁrpád Kovács-Kulyassa Andrea RenzettiJanos Sapi Jean-Yves Laronze 《Tetrahedron letters》2003,44(2):221-223
Chiral pyrano- and pyrrolidino-fused tryptamines were prepared by a diasteroselective trimolecular condensation between indole, Garner's aldehyde and Meldrum's acid, followed by selective functional group transformations. 相似文献
15.
16.
Alberto Mariani Simone Bidali Stefano Fiori Marco Sangermano Giulio Malucelli Roberta Bongiovanni Aldo Priola 《Journal of polymer science. Part A, Polymer chemistry》2004,42(9):2066-2072
By combining frontal polymerization and radical‐induced cationic polymerization, it was possible to cure thick samples of an epoxy monomer bleached by UV light. The effect of the relative amounts of cationic photoinitiator and radical initiator was thoroughly investigated and was related to the front's velocity and its maximum temperature. The materials obtained were characterized by quantitative conversion also in the deeper layers, not reached by UV light. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2066–2072, 2004 相似文献
17.
The basic features of a chemical measurement 总被引:2,自引:0,他引:2
18.
19.
20.
R. Grac M. Pugnet J.H. Collet B. Lambert C. De Matos H. L'Haridon A. Le Corre J.O. White 《Superlattices and Microstructures》1997,22(4):505-509
We report new results on the diffraction properties of photoinduced gratings in InGaAs/InGaAsP MQW structures. The original feature of this device is that the QWs are enclosed in an asymmetric Fabry–Perot microcavity in order to increase the diffraction efficiency. We observe oscillations in the diffraction efficiency due to resonant effects in the microcavity. The experimental spectra are compared with theory. Diffraction efficiency at 1.55 μm attains a maximum value of 2.7% at a write beam fluence of 260 μ J cm−2, and then decreases at higher fluences. We explain this phenomenon by an absorption saturation at high excitation. 相似文献