全文获取类型
收费全文 | 11664篇 |
免费 | 562篇 |
国内免费 | 1412篇 |
专业分类
化学 | 11235篇 |
晶体学 | 138篇 |
力学 | 72篇 |
综合类 | 43篇 |
数学 | 853篇 |
物理学 | 1297篇 |
出版年
2024年 | 12篇 |
2023年 | 141篇 |
2022年 | 225篇 |
2021年 | 247篇 |
2020年 | 349篇 |
2019年 | 318篇 |
2018年 | 269篇 |
2017年 | 345篇 |
2016年 | 317篇 |
2015年 | 263篇 |
2014年 | 498篇 |
2013年 | 1248篇 |
2012年 | 499篇 |
2011年 | 537篇 |
2010年 | 455篇 |
2009年 | 606篇 |
2008年 | 718篇 |
2007年 | 759篇 |
2006年 | 690篇 |
2005年 | 747篇 |
2004年 | 702篇 |
2003年 | 582篇 |
2002年 | 397篇 |
2001年 | 362篇 |
2000年 | 354篇 |
1999年 | 315篇 |
1998年 | 248篇 |
1997年 | 154篇 |
1996年 | 166篇 |
1995年 | 154篇 |
1994年 | 185篇 |
1993年 | 149篇 |
1992年 | 126篇 |
1991年 | 99篇 |
1990年 | 39篇 |
1989年 | 46篇 |
1988年 | 41篇 |
1987年 | 36篇 |
1986年 | 31篇 |
1985年 | 31篇 |
1984年 | 31篇 |
1982年 | 22篇 |
1981年 | 27篇 |
1980年 | 17篇 |
1979年 | 24篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 7篇 |
1973年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
T. Riesterer J. G. Bednorz K. A. Müller B. Reihl 《Applied Physics A: Materials Science & Processing》1987,44(1):81-82
We have measured ultraviolet and inverse-photoemission spectra of the novel superconductor Sr02La1.8CuO4. Our results compare favorably with recent band-structure calculations for La2CuO4.A full account of this work will be published elsewhere [1] 相似文献
42.
43.
A new formulation derived from thermal characters of inclusions and host films for estimating laser induced damage threshold has been deduced. This formulation is applicable for dielectric films when they are irradiated by laser beam with pulse width longer than tens picoseconds. This formulation can interpret the relationship between pulse-width and damage threshold energy density of laser pulse obtained experimentally. Using this formulation, we can analyze which kind of inclusion is the most harmful inclusion. Combining it with fractal distribution of inclusions, we have obtained an equation which describes relationship between number density of inclusions and damage probability. Using this equation, according to damage probability and corresponding laser energy density, we can evaluate the number density and distribution in size dimension of the most harmful inclusions. 相似文献
44.
Donald Craig 《Tetrahedron: Asymmetry》1991,2(12):1177-1180
The synthesis and thermally-induced intramolecular Diels-Alder (IMDA) reaction of (S)s-(+)-S-[(1E,7E)-1,7,9-decatrienyl]-S-phenyl-N-(p-tolylsulphonyl)sulphoximine 4 is described. A model is proposed for the cis-selectivity of the cycloaddition based on previous results from the reactions of sulphonyl-substituted trienes. The stereochemistry of the major cis-fused cycloadduct is determined by single-crystal X-ray analysis of that obtained from reaction of racemic 4. 相似文献
45.
R. Souzy B. Ameduri B. Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2004,42(20):5077-5097
The radical co‐ and terpolymerization of 4‐[(α,β,β‐trifluorovinyl)oxy]bromo benzene (TFVOBB) with 1,1‐difluoroethylene (or vinylidene fluoride, VDF, or VF2), hexafluoropropene (HFP), perfluoromethyl vinyl ether (PMVE), and chlorotrifluroroethylene (CTFE) is presented. Although TFVOBB could be thermocyclodimerized, it could not homopolymerize under radical initiation. TFVOBB could be copolymerized in solution under a radical initiator with VDF or CTFE comonomers, while its copolymerization with HFP or PMVE were unsuccessful. The terpolymerization of TFVOBB with VDF and HFP, or VDF and PMVE, or VDF and CTFE also led to original fluorinated terpolymers bearing bromoaromatic side‐groups. The conditions of co‐ and terpolymerization were optimized in terms of the nature of the radical initiators, and of the nature of solvents (fluorinated or nonhalogenated). Various monomer concentrations in the co‐ and terpolymers were assessed by 19F and 1H‐NMR spectroscopy. The thermal and physico chemical properties were also studied. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5077–5097, 2004 相似文献
46.
Ajay K. Saini Clifford M. Carlin Howard H. Patterson 《Journal of polymer science. Part A, Polymer chemistry》1992,30(3):419-427
New model compounds for poly[N,N′-bis(phenoxyphenyl)pyromellitimide] have been synthesized in order to investigate the formation of imine bonds which are proposed to form during the curing process and lead to crosslinking in the bulk polymer. Raman studies show that terminal amines can react with imide carbonyls during curing to form C?N bonds. The Raman band due to C?N appears at 1656 cm?1 and the band due to C?O closest to the imine bond is observed at 1742 cm?1. These results are in agreement with previously published results on vapor deposited polyimide films. 相似文献
47.
We discuss basic statistical properties of systems with multifractal structure. This is possible by extending the notion of the usual Gibbs-Shannon entropy into more general framework—Rényi’s information entropy. We address the renormalization issue for Rényi’s entropy on (multi)fractal sets and consequently show how Rényi’s parameter is connected with multifractal singularity spectrum. The maximal entropy approach then provides a passage between Rényi’s information entropy and thermodynamics of multifractals. Important issues such as Rényi’s entropy versus Tsallis-Havrda-Charvat entropy and PDF reconstruction theorem are also studied. Finally, some further speculations on a possible relevance of our approach to cosmology are discussed. 相似文献
48.
49.
设G是一个图 .设g和f是两个定义在V(G)上的整值函数使得对V(G)所有顶点x有g(x) ≤f(x) .图G被称为 (g ,f,n) 临界图 ,如果删去G的任意n个顶点后的子图都含有G的 (g ,f) 因子 .本文给出了图是 (a ,b ,n) 临界图几个充分条件 ,即度和邻域条件 .进一步指出这些条件是最佳的 . 相似文献
50.
I. Mohammed-Ziegler B. Por M. Kubinyi A. Grofcsik A. Grün I. Bitter 《Journal of Molecular Structure》2003,650(1-3):39-44
The complex formation between chromogenic capped calix 4 arene derivatives comprising indophenol indicator group(s), and aliphatic amines has been studied by UV/Vis spectroscopy. The equilibrium constants have been determined in ethanol, and—for one ligand—also in dimethylsulfoxide. The results have been interpreted in terms of various types of host–guest interactions and of steric effects. 相似文献