全文获取类型
收费全文 | 10047篇 |
免费 | 667篇 |
国内免费 | 1250篇 |
专业分类
化学 | 3403篇 |
晶体学 | 45篇 |
力学 | 199篇 |
综合类 | 146篇 |
数学 | 6675篇 |
物理学 | 1496篇 |
出版年
2024年 | 8篇 |
2023年 | 100篇 |
2022年 | 154篇 |
2021年 | 241篇 |
2020年 | 240篇 |
2019年 | 302篇 |
2018年 | 278篇 |
2017年 | 301篇 |
2016年 | 220篇 |
2015年 | 215篇 |
2014年 | 357篇 |
2013年 | 1052篇 |
2012年 | 337篇 |
2011年 | 480篇 |
2010年 | 405篇 |
2009年 | 569篇 |
2008年 | 621篇 |
2007年 | 788篇 |
2006年 | 601篇 |
2005年 | 549篇 |
2004年 | 480篇 |
2003年 | 504篇 |
2002年 | 450篇 |
2001年 | 369篇 |
2000年 | 354篇 |
1999年 | 337篇 |
1998年 | 317篇 |
1997年 | 280篇 |
1996年 | 199篇 |
1995年 | 116篇 |
1994年 | 136篇 |
1993年 | 84篇 |
1992年 | 83篇 |
1991年 | 59篇 |
1990年 | 44篇 |
1989年 | 43篇 |
1988年 | 41篇 |
1987年 | 43篇 |
1986年 | 24篇 |
1985年 | 43篇 |
1984年 | 23篇 |
1983年 | 16篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 10篇 |
1979年 | 7篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 4篇 |
1936年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
981.
In this paper, we introduce the concept of topological hypergroups as a generalization of topological groups. A topological hypergroup is a nonempty set endowed with two structures, that of a topological space and that of a hypergroup. Let (H, ○) be a hypergroup and (H, τ) be a topological space such that the mappings (x, y) → x ○ y and (x, y) → x/y from H × H to 𝒫*(H) are continuous. The main tool to obtain basic properties of hypergroups is the fundamental relation β*. So, by considering the quotient topology induced by the fundamental relation on a hypergroup (H, ○) we show that if every open subset of H is a complete part, then the fundamental group of H is a topological group. It is important to mention that in this paper the topological hypergroups are different from topological hypergroups which was initiated by Dunkl and Jewett. 相似文献
982.
SnO2 rods have been synthesized by using tin (II) chain‐like complexes as precursors in which oxalate and ethylene glycol act as co‐ligands. On the basis of experimental analysis, a reasonable formation mechanism of rods is discussed, which is further supported by Fourier transform infrared spectroscopy (FT‐IR). These results show that the synergistic effect of oxalate group and ethylene glycol plays an important role in the formation of long SnO2 rods. 相似文献
983.
984.
Rajoshree Bandyopadhyay 《Journal of organometallic chemistry》2010,695(7):1012-10984
The treatment of tin(II) trifluoromethanesulfonate with three differently-sized crown ethers [12]crown-4, [15]crown-5 and [18]crown-6 results in the formation of tin complexes that exhibit dramatically different structural features. The compounds are investigated using experimental techniques and density functional theory calculations. 相似文献
985.
986.
Michio Umino 《The Journal of mathematical sociology》2013,37(4):237-246
This paper examines Dawes (1975) model on commons dilemma (CD) situation and proposes an alternative model which formulates CD. Firstly, it makes clear that Dawes model does not have the characteristics of CD. Secondly, it specifies “resource unit condition” which models of commons dilemma must satisfy. Thirdly, it presents CD model, which is obtained by setting the condition in Dawes model. And lastly, it examines some nature of the proposed model and find that in CD situation, fine is distributed proportionally to each player's property. 相似文献
987.
988.
In this paper, a certain class of welded knots K_(2n) is considered. By calculating the commutators subgroup of fundamental group Gn of welded knot K_(2n),n ∈ Z~+, we show that these welded knots are not equivalent to each other and they are all not classical knots. Secondly, we study some properties of Gn and obtain that Gn is linear, residually finite and Hopfian. 相似文献
989.
《代数通讯》2013,41(11):5361-5376
Abstract We prove that when a countable group admits a nontrivial Floyd-type boundary, then every nonelementary and metrically proper subgroup contains a noncommutative free subgroup. This generalizes the corresponding well-known results for hyperbolic groups and groups with infinitely many ends. It also shows that no finitely generated amenable group admits a nontrivial boundary of this type. This improves on a theorem by Floyd (Floyd, W. J. (1980). Group completions and limit sets of Kleinian groups. Invent. Math. 57: 205–218) as well as giving an elementary proof of a conjecture stated in that same paper. We also show that if the Floyd boundary of a finitely generated group is nontrivial, then it is a boundary in the sense of Furstenberg and the group acts on it as a convergence group. 相似文献
990.
We show in the smooth category that the heat trace asymptotics and the heat content asymptotics can be made to grow arbitrarily rapidly. In the real analytic context, however, this is not true and we establish universal bounds on their growth. 相似文献