全文获取类型
收费全文 | 7171篇 |
免费 | 187篇 |
国内免费 | 155篇 |
专业分类
化学 | 1234篇 |
晶体学 | 64篇 |
力学 | 39篇 |
综合类 | 17篇 |
数学 | 5444篇 |
物理学 | 715篇 |
出版年
2024年 | 5篇 |
2023年 | 32篇 |
2022年 | 38篇 |
2021年 | 51篇 |
2020年 | 66篇 |
2019年 | 159篇 |
2018年 | 142篇 |
2017年 | 85篇 |
2016年 | 79篇 |
2015年 | 105篇 |
2014年 | 199篇 |
2013年 | 334篇 |
2012年 | 230篇 |
2011年 | 453篇 |
2010年 | 365篇 |
2009年 | 423篇 |
2008年 | 436篇 |
2007年 | 494篇 |
2006年 | 373篇 |
2005年 | 245篇 |
2004年 | 195篇 |
2003年 | 207篇 |
2002年 | 192篇 |
2001年 | 141篇 |
2000年 | 135篇 |
1999年 | 178篇 |
1998年 | 195篇 |
1997年 | 167篇 |
1996年 | 162篇 |
1995年 | 208篇 |
1994年 | 157篇 |
1993年 | 163篇 |
1992年 | 154篇 |
1991年 | 92篇 |
1990年 | 92篇 |
1989年 | 112篇 |
1988年 | 63篇 |
1987年 | 49篇 |
1986年 | 53篇 |
1985年 | 76篇 |
1984年 | 72篇 |
1983年 | 55篇 |
1982年 | 66篇 |
1981年 | 43篇 |
1980年 | 40篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1974年 | 4篇 |
排序方式: 共有7513条查询结果,搜索用时 31 毫秒
81.
Michael J. Puls 《Archiv der Mathematik》2007,88(6):500-506
Let p be a real number greater than one. In this paper we study the vanishing and nonvanishing of the first L
p
-cohomology space of some groups that have one end. We also make a connection between the first L
p
-cohomolgy space and the Floyd boundary of the Cayley graph of a group. We apply the result about Floyd boundaries to show
that there exists a real number p such that the first L
p
-cohomology space of a nonelementary hyperbolic group does not vanish.
Received: 4 August 2006 Revised: 2 November 2006 相似文献
82.
Yuval Z. Flicker 《Mathematische Annalen》1993,297(1):199-219
83.
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
84.
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
85.
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
86.
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
87.
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
88.
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
89.
Baisheng Yan 《Bulletin des Sciences Mathématiques》2003,127(6):467-483
We study the solvability of special vectorial Hamilton-Jacobi systems of the form F(Du(x))=0 in a Sobolev space. In this paper we establish the general existence theorems for certain Dirichlet problems using suitable approximation schemes called W1,p-reduction principles that generalize the similar reduction principle for Lipschitz solutions. Our approach, to a large extent, unifies the existing methods for the existence results of the special Hamilton-Jacobi systems under study. The method relies on a new Baire's category argument concerning the residual continuity of a Baire-one function. Some sufficient conditions for W1,p-reduction are also given along with certain generalization of some known results and a specific application to the boundary value problem for special weakly quasiregular mappings. 相似文献
90.
We study the metrical theory of fibred systems, in particular, in the case of continued fraction mixing systems. We get the
limit distribution of the largest value of a continued fraction mixing stationary stochastic process with infinite expectation
and some related results. These are analogous to J. Galambos, W. Philipp, and H. G. Diamond–J. D. Vaaler theorems for the
regular continued fractions. As an application, we see that these theorems hold for Jacobi-Perron algorithm.
Received September 30, 2001; in revised form January 8, 2002 相似文献