全文获取类型
收费全文 | 20166篇 |
免费 | 891篇 |
国内免费 | 158篇 |
专业分类
化学 | 13884篇 |
晶体学 | 139篇 |
力学 | 522篇 |
数学 | 3353篇 |
物理学 | 3317篇 |
出版年
2023年 | 165篇 |
2022年 | 258篇 |
2021年 | 437篇 |
2020年 | 474篇 |
2019年 | 452篇 |
2018年 | 318篇 |
2017年 | 286篇 |
2016年 | 767篇 |
2015年 | 585篇 |
2014年 | 687篇 |
2013年 | 1128篇 |
2012年 | 1443篇 |
2011年 | 1676篇 |
2010年 | 872篇 |
2009年 | 734篇 |
2008年 | 1296篇 |
2007年 | 1227篇 |
2006年 | 1170篇 |
2005年 | 1114篇 |
2004年 | 935篇 |
2003年 | 685篇 |
2002年 | 669篇 |
2001年 | 233篇 |
2000年 | 199篇 |
1999年 | 182篇 |
1998年 | 158篇 |
1997年 | 158篇 |
1996年 | 235篇 |
1995年 | 133篇 |
1994年 | 141篇 |
1993年 | 159篇 |
1992年 | 105篇 |
1991年 | 122篇 |
1990年 | 106篇 |
1989年 | 93篇 |
1988年 | 106篇 |
1987年 | 100篇 |
1986年 | 82篇 |
1985年 | 126篇 |
1984年 | 124篇 |
1983年 | 73篇 |
1982年 | 132篇 |
1981年 | 132篇 |
1980年 | 110篇 |
1979年 | 98篇 |
1978年 | 119篇 |
1977年 | 98篇 |
1976年 | 76篇 |
1975年 | 73篇 |
1973年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
961.
962.
Daniel Tordera Andreas M. Bünzli Antonio Pertegás Dr. José M. Junquera‐Hernández Prof. Edwin C. Constable Dr. Jennifer A. Zampese Prof. Catherine E. Housecroft Prof. Enrique Ortí Dr. Henk J. Bolink 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8597-8609
A new approach to obtain green‐emitting iridium(III) complexes is described. The synthetic approach consists of introducing a methylsulfone electron‐withdrawing substituent into a 4‐phenylpyrazole cyclometalating ligand in order to stabilize the highest‐occupied molecular orbital (HOMO). Six new complexes have been synthesized incorporating the conjugate base of 1‐(4‐(methylsulfonyl)phenyl)‐1 H‐pyrazole as the cyclometalating ligand. The complexes show green emission and very high photoluminescence quantum yields in both diluted and concentrated films. When used as the main active component in light‐emitting electrochemical cells (LECs), green electroluminance is observed. High efficiencies and luminances are obtained at low driving voltages. This approach for green emitters is an alternative to the widely used fluorine‐based substituents in the cyclometalating ligands and opens new design possibilities for the synthesis of green emitters for LECs. 相似文献
963.
Dr. Daniel Müller Prof. Alexandre Alexakis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15226-15239
Alkenylaluminums undergo asymmetric copper‐catalyzed conjugate addition (ACA) to β‐substituted enones allowing the formation of stereogenic all‐carbon quaternary centers. Phosphinamine–copper complexes proved to be particularly active and selective compared with phosphoramidite ligands. After extensive optimization, high enantioselectivities (up to 96 % ee) were obtained for the addition of alkenylalanes to β‐substituted enones. Two strategies for the generation of the requisite alkenylaluminums were explored allowing for the introduction of aryl‐ and alkyl‐substituted alkenyl nucleophiles. Moreover, alkyl‐substituted phosphinamine (SimplePhos) ligands were identified for the first time as highly efficient ligands for the Cu‐catalyzed ACA. 相似文献
964.
Cristina García‐Simón Marc Garcia‐Borràs Dr. Laura Gómez Dr. Isaac Garcia‐Bosch Dr. Sílvia Osuna Prof. Marcel Swart Dr. Josep M. Luis Prof. Concepció Rovira Prof. Manuel Almeida Dr. Inhar Imaz Prof. Daniel Maspoch Dr. Miquel Costas Dr. Xavi Ribas 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(4):1445-1456
The metal‐directed supramolecular synthetic approach has paved the way for the development of functional nanosized molecules. In this work, we report the preparation of the new nanocapsule 3? (CF3SO3)8 with a A4B2 tetragonal prismatic geometry, where A corresponds to the dipalladium hexaazamacrocyclic complex Pd‐1 , and B corresponds to the tetraanionic form of palladium 5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrin ( 2 ). The large void space of the inner cavity and the supramolecular affinity for guest molecules towards porphyrin‐based hosts converts this nanoscale molecular 3D structure into a good candidate for host–guest chemistry. The interaction between this nanocage and different guest molecules has been studied by means of NMR, UV/Vis, ESI‐MS, and DOSY experiments, from which highly selective molecular recognition has been found for anionic, planar‐shaped π guests with association constants (Ka) higher than 109 M ?1, in front of non‐interacting aromatic neutral or cationic substrates. DFT theoretical calculations provided insights to further understand this strong interaction. Nanocage 3? (CF3SO3)8 can not only strongly host one single molecule of M(dithiolene)2 complexes (M=Au, Pt, Pd, and Ni), but also can finely tune their optical and redox properties. The very simple synthesis of both the supramolecular cage and the building blocks represents a step forward for the development of polyfunctional supramolecular nanovessels, which offer multiple applications as sensors or nanoreactors. 相似文献
965.
Prof. Dr. Luis Casarrubios Dr. María C. de la Torre Prof. Dr. Miguel A. Sierra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3534-3541
CuI‐catalyzed 1,3‐cycloaddition of azides and alkynes (CuAAC) is one of the most powerful synthetic methodologies known. However, its use to prepare well‐defined multimetallic structures is underdeveloped. Apart from the applications of this reaction to anchor different organometallic reagents to surfaces, polymers, and dendrimers, only isolated examples of CuAAC with metal–η1‐alkyne and metal–azide complexes to prepare multimetal entities have been reported. This concept sketches the potential of these reactions not only to prepare “a la carte” multimetal 1,2,3‐triazole derivatives, but also to discover new and unprecedented reactions. 相似文献
966.
Thibault Dutronc Dr. Emmanuel Terazzi Dr. Laure Guénée Kerry‐Lee Buchwalder Aurore Spoerri Dr. Daniel Emery Dr. Jiri Mareda Dr. Sébastien Floquet Prof. Claude Piguet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8447-8456
This work illustrates how minor structural perturbations produced by methylation of 4′‐(dodecyloxy)‐4‐cyanobiphenyl leads to enthalpy–entropy compensation for their melting processes, a trend which can be analyzed within the frame of a simple intermolecular cohesive model. The transformation of the melting thermodynamic parameters collected at variable temperatures into cohesive free‐energy densities expressed at a common reference temperature results in a novel linear correlation, from which melting temperatures can be simply predicted from molecular volumes. 相似文献
967.
Etienne Brachet Prof. Jean‐Daniel Brion Dr. Mouad Alami Dr. Samir Messaoudi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(45):15276-15280
Unprotected thioglycosides were effective nucleophiles for Ni0‐catalyzed C? S bond‐forming reaction with functionalized (hetero)aryl, alkenyl, and alkynyl halides. The functional‐group tolerance on the electrophilic partner was typically high and the anomeric selectivities of the thioglycosides were high in all cases. The efficiency of this general procedure was well‐demonstrated by the synthesis of 4‐methyl‐7‐thioumbelliferyl‐β‐D ‐cellobioside (MUS‐CB). 相似文献
968.
969.
970.
Josué Antonio Nescolarde‐Selva José Luis Usó-Doménech Miguel Lloret‐Climent 《Complexity》2015,21(2):47-65
The goal of this article is to build an abstract mathematical theory rather than a computational one of the process of transmission of ideology. The basis of much of the argument is Patten's Environment Theory that characterizes a system with its double environment (input or stimulus and output or response) and the existing interactions among them. Ideological processes are semiotic processes, and if in Patten's theory, the two environments are physical, in this theory ideological processes are physical and semiotic, as are stimulus and response. © 2014 Wiley Periodicals, Inc. Complexity 21: 47–65, 2015 相似文献