全文获取类型
收费全文 | 1454篇 |
免费 | 79篇 |
国内免费 | 201篇 |
专业分类
化学 | 139篇 |
晶体学 | 1篇 |
力学 | 116篇 |
综合类 | 27篇 |
数学 | 1338篇 |
物理学 | 113篇 |
出版年
2024年 | 2篇 |
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 25篇 |
2020年 | 26篇 |
2019年 | 38篇 |
2018年 | 50篇 |
2017年 | 57篇 |
2016年 | 38篇 |
2015年 | 39篇 |
2014年 | 53篇 |
2013年 | 190篇 |
2012年 | 55篇 |
2011年 | 57篇 |
2010年 | 60篇 |
2009年 | 83篇 |
2008年 | 113篇 |
2007年 | 94篇 |
2006年 | 85篇 |
2005年 | 72篇 |
2004年 | 66篇 |
2003年 | 77篇 |
2002年 | 76篇 |
2001年 | 46篇 |
2000年 | 51篇 |
1999年 | 39篇 |
1998年 | 48篇 |
1997年 | 35篇 |
1996年 | 17篇 |
1995年 | 18篇 |
1994年 | 20篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有1734条查询结果,搜索用时 140 毫秒
991.
用拉压不同模量理论分析弯曲板 总被引:12,自引:0,他引:12
材料的拉压不同弹性模量性对结构计算的影响是一个不容忽视的问题,本文对不同模量弯曲板进行了较系统的分析,构造了相应的有限元算法,通过算例分析,得出了一些较有价值的结论。 相似文献
992.
Peng Lin Nan-Xiang Zhang Jing-Jing Li Jing Zhang Jia-Hui Liu Bao Zhang Jian Song 《中国化学快报》2017,28(4):771-776
The gelation behaviours of low molecular weight gelators 1,3:2,5:4,6-tris(3,4-dichlorobenzylidene)-D-mannitol(G1)and 2,4-(3,4-dichlorobenzylidene)-N-(3-aminopropyl)-D-gluconamide(G2)in 34 solvents have been studied.We found that sample dissolved at low concentrations may become a gel or precipitate at higher concentrations.The Hansen solubility parameters(HSPs)and a Teas plot were employed to correlate the gelation behaviours with solvent properties,but with no success if the concentration of the tests was not maintained constant.Instead,on the basis of the gelation results obtained for the G1 and G2 in single solvents,we studied the gelation behaviours of G1 and G2 in 23 solvent mixtures and found that the tendency of a gelator to form a gel in mixed solvents is strongly correlated with its gelation behaviours in good solvents.If the gelation occurs in a good solvent at higher concentrations,it will take place as well in a mixed solvent(the good solvent plus a poor solvent)at a certain volume ratio.In contrast,if the gelator forms a precipitate in a good solvent at higher concentrations,no gelation is to be observed in the mixed solvents.A gelation rule for mixed solvents is thus proposed,which may facilitate decision making with regard to solvent selection for gel formation in the solvent mixtures in practical applications. 相似文献
993.
《Mathematische Nachrichten》2017,290(11-12):1830-1839
The aim of this short note is to give an alternative proof, which applies to functions of bounded variation in arbitrary domains, of an inequality by Maz'ya that improves Friedrichs inequality. A remarkable feature of such a proof is that it is rather elementary, if the basic background in the theory of functions of bounded variation is assumed. Nevertheless, it allows to extend all the previously known versions of this fundamental inequality to a completely general version. In fact the inequality presented here is optimal in several respects. As already observed in previous proofs, the crucial step is to provide conditions under which a function of bounded variation on a bounded open set, extended to zero outside, has bounded variation on the whole space. We push such conditions to their limits. In fact, we give a sufficient and necessary condition if the open set has a boundary with σ‐finite surface measure and a sufficient condition if the open set is fully arbitrary. Via a counterexample we show that such a general sufficient condition is sharp. 相似文献
994.
Yanyong Hong 《代数通讯》2017,45(7):2821-2836
In this paper, two classes of Schrödinger-Virasoro type Lie conformal algebras TSV(a,b) and TSV(c) which are non-simple are introduced for some a, b, c∈?. Moreover, central extensions, conformal derivations and free conformal modules of rank 1 of TSV(a,b) and TSV(c) are determined. 相似文献
995.
996.
In this paper, purity of S-posets over a pomonoid S is investigated. We first study some basic properties of absolutely po-pure S-posets. Among other results, it is proved that every regular injective S-poset is absolutely po-pure, and every absolutely po-pure inequationally compact S-poset is regular injective. Then, using the notion of semi-finitely presented S-poset based on the finitely induced S-poset congruence, we find an equivalent condition for an S-poset to be 1-po-pure in a regular extension. Finally, a characterization of an absolutely 1-po-pure S-poset is presented. 相似文献
997.
998.
In this expository article, the authors discuss the connection between the study of non-local operators on Euclidean space to the study of fractional GJMS operators in conformal geometry. The emphasis is on the study of a class of fourth order operators and their third order boundary operators. These third order operators are generalizations of the Dirichlet-to-Neumann operator. 相似文献
999.
Jing Lin 《Journal of Mathematical Analysis and Applications》2007,329(1):51-64
This paper solves the following form of normalized eigenvalue problem:
1000.
Kai WANG 《数学年刊B辑(英文版)》2007,28(3):321-326
Let M be an invariant subspace of Hv2. It is shown that for each f∈M⊥, f can be analytically extended across (?)Bd\σ(Sz1,…, Szd). 相似文献