全文获取类型
收费全文 | 173152篇 |
免费 | 15555篇 |
国内免费 | 12813篇 |
专业分类
化学 | 58303篇 |
晶体学 | 2067篇 |
力学 | 9544篇 |
综合类 | 1711篇 |
数学 | 65446篇 |
物理学 | 64449篇 |
出版年
2023年 | 1097篇 |
2022年 | 2144篇 |
2021年 | 3027篇 |
2020年 | 3145篇 |
2019年 | 3528篇 |
2018年 | 3176篇 |
2017年 | 3157篇 |
2016年 | 3581篇 |
2015年 | 3295篇 |
2014年 | 5342篇 |
2013年 | 9586篇 |
2012年 | 5623篇 |
2011年 | 7099篇 |
2010年 | 7006篇 |
2009年 | 12620篇 |
2008年 | 13710篇 |
2007年 | 12281篇 |
2006年 | 10788篇 |
2005年 | 8079篇 |
2004年 | 7427篇 |
2003年 | 7389篇 |
2002年 | 10012篇 |
2001年 | 6208篇 |
2000年 | 5891篇 |
1999年 | 5346篇 |
1998年 | 4557篇 |
1997年 | 3597篇 |
1996年 | 3117篇 |
1995年 | 3277篇 |
1994年 | 3084篇 |
1993年 | 2529篇 |
1992年 | 2015篇 |
1991年 | 1479篇 |
1990年 | 1293篇 |
1989年 | 1120篇 |
1988年 | 1071篇 |
1987年 | 812篇 |
1986年 | 612篇 |
1985年 | 1504篇 |
1984年 | 1131篇 |
1983年 | 779篇 |
1982年 | 1118篇 |
1981年 | 1263篇 |
1980年 | 1144篇 |
1979年 | 1025篇 |
1978年 | 922篇 |
1977年 | 770篇 |
1976年 | 734篇 |
1974年 | 457篇 |
1973年 | 618篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
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
4.
Dr. Jordan Donat Mr. Patrick Dubourdeaux Dr. Martin Clémancey Dr. Julia Rendon Clara Gervasoni Mr. Morgan Barbier Jessica Barilone Dr. Jacques Pécaut Prof. Dr. Serge Gambarelli Prof. Dr. Pascale Maldivi Prof. Dr. Jean-Marc Latour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202201875
Nitrene transfer reactions have emerged as one of the most powerful and versatile ways to insert an amine function to various kinds of hydrocarbon substrates. However, the mechanisms of nitrene generation have not been studied in depth albeit their formation is taken for granted in most cases without definitive evidence of their occurrence. In the present work, we compare the generation of tosylimido iron species and NTs transfer from FeII and FeIII precursors where the metal is embedded in a tetracarbene macrocycle. Catalytic nitrene transfer to reference substrates (thioanisole, styrene, ethylbenzene and cyclohexane) revealed that the same active species was at play, irrespective of the ferrous versus ferric nature of the precursor. Through combination of spectroscopic (UV-visible, Mössbauer), ESI-MS and DFT studies, an FeIV tosylimido species was identified as the catalytically active species and was characterized spectroscopically and computationally. Whereas its formation from the FeII precursor was expected by a two-electron oxidative addition, its formation from an FeIII precursor was unprecedented. Thanks to a combination of spectroscopic (UV-visible, EPR, Hyscore and Mössbauer), ESI-MS and DFT studies, we found that, when starting from the FeIII precursor, an FeIII tosyliodinane adduct was formed and decomposed into an FeV tosylimido species which generated the catalytically active FeIV tosylimide through a comproportionation process with the FeIII precursor. 相似文献
5.
《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
6.
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
7.
M. Amar D. Andreucci R. Gianni C. Timofte 《Journal of Mathematical Analysis and Applications》2021,493(2):124533
We prove a well-posedness result for two pseudo-parabolic problems, which can be seen as two models for the same electrical conduction phenomenon in heterogeneous media, neglecting the magnetic field. One of the problems is the concentration limit of the other one, when the thickness of the dielectric inclusions goes to zero. The concentrated problem involves a transmission condition through interfaces, which is mediated by a suitable Laplace-Beltrami type equation. 相似文献
8.
9.
Clemens G. Raab Georg Regensburger Jamal Hossein Poor 《Journal of Pure and Applied Algebra》2021,225(5):106564
A formal computation proving a new operator identity from known ones is, in principle, restricted by domains and codomains of linear operators involved, since not any two operators can be added or composed. Algebraically, identities can be modelled by noncommutative polynomials and such a formal computation proves that the polynomial corresponding to the new identity lies in the ideal generated by the polynomials corresponding to the known identities. In order to prove an operator identity, however, just proving membership of the polynomial in the ideal is not enough, since the ring of noncommutative polynomials ignores domains and codomains. We show that it suffices to additionally verify compatibility of this polynomial and of the generators of the ideal with the labelled quiver that encodes which polynomials can be realized as linear operators. Then, for every consistent representation of such a quiver in a linear category, there exists a computation in the category that proves the corresponding instance of the identity. Moreover, by assigning the same label to several edges of the quiver, the algebraic framework developed allows to model different versions of an operator by the same indeterminate in the noncommutative polynomials. 相似文献
10.