全文获取类型
收费全文 | 48658篇 |
免费 | 3924篇 |
国内免费 | 4518篇 |
专业分类
化学 | 12837篇 |
晶体学 | 137篇 |
力学 | 2633篇 |
综合类 | 235篇 |
数学 | 12256篇 |
物理学 | 12656篇 |
综合类 | 16346篇 |
出版年
2024年 | 127篇 |
2023年 | 480篇 |
2022年 | 846篇 |
2021年 | 1009篇 |
2020年 | 1294篇 |
2019年 | 1177篇 |
2018年 | 1170篇 |
2017年 | 1379篇 |
2016年 | 1472篇 |
2015年 | 1469篇 |
2014年 | 2686篇 |
2013年 | 3826篇 |
2012年 | 2943篇 |
2011年 | 3255篇 |
2010年 | 2634篇 |
2009年 | 3133篇 |
2008年 | 3220篇 |
2007年 | 3071篇 |
2006年 | 2634篇 |
2005年 | 2313篇 |
2004年 | 1873篇 |
2003年 | 1748篇 |
2002年 | 1595篇 |
2001年 | 1242篇 |
2000年 | 1235篇 |
1999年 | 994篇 |
1998年 | 905篇 |
1997年 | 768篇 |
1996年 | 979篇 |
1995年 | 786篇 |
1994年 | 605篇 |
1993年 | 461篇 |
1992年 | 444篇 |
1991年 | 355篇 |
1990年 | 387篇 |
1989年 | 371篇 |
1988年 | 296篇 |
1987年 | 266篇 |
1986年 | 196篇 |
1985年 | 198篇 |
1984年 | 189篇 |
1983年 | 99篇 |
1982年 | 137篇 |
1981年 | 131篇 |
1980年 | 109篇 |
1979年 | 113篇 |
1978年 | 88篇 |
1977年 | 83篇 |
1976年 | 75篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Giang Truong Nguyen Prof. Dr. Liviu Ungur 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(30):e202200227
Employing radical bridges between anisotropic metal ions has been a viable route to achieve high-performance single-molecule magnets (SMMs). While the bridges have been mainly considered for their ability to promote exchange interactions, the crystal-field effect arising from them has not been taken into account explicitly. This lack of consideration may distort the understanding and limit the development of the entire family. To shed light on this aspect, herein we report a theoretical investigation of a series of N -radical-bridged diterbium complexes. It is found that while promoting strong exchange coupling between the terbium ions, the N -radical induces a crystal field that interferes destructively with that of the outer ligands, and thus reduces the overall SMM behavior. Based on the theoretical results, we conclude that the SMM behavior in this series could be further maximized if the crystal field of the outer ligands is designed to be collinear with that of the radical bridge. This conclusion can be generalized to all exchange-coupled SMMs. 相似文献
3.
为了寻找团簇Co3FeP的稳定性、结构和内部作用力等规律,利用密度泛函理论,在B3LYP/Lanl2dz的量化水平下对团簇Co3FeP进行理论计算,得到5种优化构型,并从化学反应热力学与动力学的角度对其异构化反应中的反应物、过渡态和生成物进行了讨论分析。结果表明,所有构型均为C1对称且构型的空间结构对其熵值有影响;构型的稳定性主要由金属原子与非金属原子所决定,并且在常温常压下构型1(3)、2(3)和3(3)可以稳定存在,是大部分异构化反应的最终产物。因此,在实际材料的开发中,不仅需要注意金属原子与非金属原子之间的作用力以确保构型的稳定性,还应首先考虑对稳定构型1(3)、2(3)和3(3)进行相关研究。 相似文献
4.
《Indagationes Mathematicae》2021,32(1):55-85
We show that the differential structure of the orbit space of a proper action of a Lie group on a smooth manifold is weakly reflexive. This implies that the orbit space is a differentiable space in the sense of Smith, which ensures that the orbit space has an exterior algebra of differential forms, that satisfies Smith’s version of de Rham’s theorem. Because the orbit space is a locally closed subcartesian space, it has vector fields and their flows. 相似文献
5.
Claudius Gros 《Entropy (Basel, Switzerland)》2021,23(2)
Human societies are characterized by three constituent features, besides others. (A) Options, as for jobs and societal positions, differ with respect to their associated monetary and non-monetary payoffs. (B) Competition leads to reduced payoffs when individuals compete for the same option as others. (C) People care about how they are doing relatively to others. The latter trait—the propensity to compare one’s own success with that of others—expresses itself as envy. It is shown that the combination of (A)–(C) leads to spontaneous class stratification. Societies of agents split endogenously into two social classes, an upper and a lower class, when envy becomes relevant. A comprehensive analysis of the Nash equilibria characterizing a basic reference game is presented. Class separation is due to the condensation of the strategies of lower-class agents, which play an identical mixed strategy. Upper-class agents do not condense, following individualist pure strategies. The model and results are size-consistent, holding for arbitrary large numbers of agents and options. Analytic results are confirmed by extensive numerical simulations. An analogy to interacting confined classical particles is discussed. 相似文献
6.
7.
A finite support product of clones of Jensen's minimal singleton forcing is used to define a model in which any non-empty analytically definable set of reals contains an analytically definable real (the full basis theorem), but there is no analytically definable wellordering of the reals. 相似文献
8.
《Journal of Pure and Applied Algebra》2022,226(8):107024
We solve a combinatorial question concerning eigenvalues of the universal intertwining endomorphism of a subset representation. 相似文献
9.
D-S证据理论可应用于多源数据融合领域,但在处理高度冲突的证据时,可能会出现反直觉的结果.为解决这一问题,本文提出了差异信息量的概念及融合方法.首先,通过信息熵表明证据的相对重要性,采用散度获取证据可信度.然后利用证据可信度优化证据差异度以得到差异信息量,经过计算获取数据的最终权重,并将其作为D-S证据理论中的基本概率分配进行决策.在处理冲突证据、一致证据及不同数量证据等方面的数据融合问题时与其他方法对比,所提方法收敛更快,准确度更高.故障诊断的应用实例表明,所提方法的不确定性更小,优于现存的其他方法. 相似文献
10.