全文获取类型
收费全文 | 9767篇 |
免费 | 236篇 |
国内免费 | 192篇 |
专业分类
化学 | 1459篇 |
晶体学 | 70篇 |
力学 | 55篇 |
综合类 | 21篇 |
数学 | 7562篇 |
物理学 | 1028篇 |
出版年
2023年 | 35篇 |
2022年 | 55篇 |
2021年 | 56篇 |
2020年 | 75篇 |
2019年 | 220篇 |
2018年 | 197篇 |
2017年 | 112篇 |
2016年 | 103篇 |
2015年 | 129篇 |
2014年 | 277篇 |
2013年 | 445篇 |
2012年 | 334篇 |
2011年 | 613篇 |
2010年 | 478篇 |
2009年 | 615篇 |
2008年 | 650篇 |
2007年 | 718篇 |
2006年 | 549篇 |
2005年 | 346篇 |
2004年 | 274篇 |
2003年 | 296篇 |
2002年 | 259篇 |
2001年 | 207篇 |
2000年 | 211篇 |
1999年 | 259篇 |
1998年 | 255篇 |
1997年 | 222篇 |
1996年 | 212篇 |
1995年 | 279篇 |
1994年 | 221篇 |
1993年 | 221篇 |
1992年 | 187篇 |
1991年 | 105篇 |
1990年 | 103篇 |
1989年 | 132篇 |
1988年 | 72篇 |
1987年 | 55篇 |
1986年 | 63篇 |
1985年 | 87篇 |
1984年 | 80篇 |
1983年 | 61篇 |
1982年 | 71篇 |
1981年 | 50篇 |
1980年 | 40篇 |
1979年 | 43篇 |
1978年 | 43篇 |
1977年 | 25篇 |
1976年 | 20篇 |
1975年 | 11篇 |
1974年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
111.
Yuval Z. Flicker 《Mathematische Annalen》1993,297(1):199-219
112.
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
113.
A. S. Peregudov L. N. Usatova E. I. Smyslova E. I. Fedin D. N. Kravtsov 《Russian Chemical Bulletin》1995,44(8):1513-1519
It has been shown by the19F NMR method that the relative polarities of nitrogenelement bonds in 2-(4-fluorophenyl)benzimidazole and its PhHg and PPh3Au derivatives increase in the order N-H19F NMR. It has been found that these reactions occur by a bimolecular associative mechanism and that the N-H bond is substantially less reactive than the N-Hg and N-Au bonds, which have identical reactivities within the limits of sensitivity of the method used.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1574–1580, August, 1995.This work was carried out with financial support from the Russian Foundation for Basic Research (Project No. 93-03-5528). 相似文献
114.
Flavio Previale 《Archive for Mathematical Logic》1994,33(3):213-241
The paper contains an axiomatic treatment of the intuitionistic theory of hereditarily finite sets, based on an induction axiom-schema and a finite set of single axioms. The main feature of the principle of induction used (due to Givant and Tarski) is that it incorporates Foundation. On the analogy of what is done in Arithmetic, in the axiomatic system selected the transitive closure of the membership relation is taken as a primitive notion, so as to permit an immediate adaptation of the theory to cases of restricted induction (in particular primitive recursive induction). At the end of the paper several different forms of induction, which play an important role in the development of the theory, are compared. An alternative axiomatization of the theory, which is of intrinsic interest, is also discussed. 相似文献
115.
Erkki Mäkinen 《BIT Numerical Mathematics》1987,27(3):330-339
The splay tree is a self-adjusting binary search tree which has a good amortized performance. This paper studies some properties of top-down splay trees. Different ways to charge for the primitive operations of top-down splaying are discussed. We also give some empirical results concerning the behaviour of different top-down restructuring algorithms.This work was supported by the Academy of Finland. 相似文献
116.
Partially finite convex programming,Part I: Quasi relative interiors and duality theory 总被引:6,自引:0,他引:6
We study convex programs that involve the minimization of a convex function over a convex subset of a topological vector space, subject to a finite number of linear inequalities. We develop the notion of the quasi relative interior of a convex set, an extension of the relative interior in finite dimensions. We use this idea in a constraint qualification for a fundamental Fenchel duality result, and then deduce duality results for these problems despite the almost invariable failure of the standard Slater condition. Part II of this work studies applications to more concrete models, whose dual problems are often finite-dimensional and computationally tractable. 相似文献
117.
本文用ab initio计算方法,采用STO-3G基组,对二硝基卤代甲烷CH_2(NO_2)_3(1),CF_2(NO_2)_2(2);CCl_2(NO_2)_2(3)等分子作了单点计算,研究其旋转势能.全构型优化研究了五个具有对称性构型的结构和稳定性,并作了理论分析和探讨. 相似文献
118.
119.
Etienne Sandier Itai Shafrir 《Calculus of Variations and Partial Differential Equations》1994,2(1):113-122
We study the uniqueness of minimizing harmonic maps to a closed hemisphere. We are able to describe the boundary data for which there are more than one minimizer, and to describe in these cases the corresponding set of minimizers. This is a limiting case for a former result of W.Jäger and H.Kaul.This article was processed by the author using the Springer-Verlag TEX PJourlg macro package 1991. 相似文献
120.
Jean Dolbeault Maria J Esteban Michael Loss Luis Vega 《Journal of Functional Analysis》2004,216(1):1-21
We prove some sharp Hardy-type inequalities related to the Dirac operator by elementary, direct methods. Some of these inequalities have been obtained previously using spectral information about the Dirac-Coulomb operator. Our results are stated under optimal conditions on the asymptotics of the potentials near zero and near infinity. 相似文献