全文获取类型
收费全文 | 734篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 608篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 90篇 |
物理学 | 46篇 |
出版年
2023年 | 3篇 |
2022年 | 11篇 |
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 3篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 32篇 |
2012年 | 43篇 |
2011年 | 39篇 |
2010年 | 17篇 |
2009年 | 28篇 |
2008年 | 35篇 |
2007年 | 52篇 |
2006年 | 32篇 |
2005年 | 47篇 |
2004年 | 29篇 |
2003年 | 34篇 |
2002年 | 34篇 |
2001年 | 15篇 |
2000年 | 8篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 11篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 13篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1934年 | 3篇 |
1889年 | 2篇 |
排序方式: 共有755条查询结果,搜索用时 15 毫秒
81.
Rosita Diana Francesco Silvio Gentile Antonio Carella Luigi Di Costanzo Barbara Panunzi 《Molecules (Basel, Switzerland)》2022,27(18)
Advanced chromophoric tools, besides being biologically active, need to meet the expectations of the technological demands including stability, colour retention, and proper solubility for their target. Many coordination compounds of conjugated ligands are antibacterial dyes, able to combine a strong dyeing performance with a useful biological activity. Specifically, palladium (II) complexes of Schiff base ligands are known for their relevant activity against common bacteria. In this article, we report the synthesis and comprehensive experimental and theoretical characterization of two novel Pd(II) chromophore complexes obtained from a cyclopalladated Schiff base as two different chelating azo dyes. The antibacterial response of these two novel complexes was tested against the ubiquitous Escherichia coli bacterium in an aqueous medium and revealed a noteworthy antimicrobial activity, higher than when compared with their uncoordinated biologically active ligands. 相似文献
82.
Silvio Cinquini 《Annali di Matematica Pura ed Applicata》1932,10(1):233-254
Sunto Il presente lavoro contiene le condizioni necessarie per la semicontinuità, su una qualunque superficie definita da una funzionez=z(x, y) assolutamente continua (nel senso del prof.Tonelli), degli integrali doppi del Calcolo delle Variazioni.
Lavoro eseguito nel Seminario Matematico della R. Scuola Normale Superiore di Pisa nell'anno accademico 1930–31. 相似文献
83.
84.
85.
Rachele Stefania Dr. Lorenzo Tei Dr. Alessandro Barge Dr. Simonetta Geninatti Crich Dr. Ibolya Szabo Dr. Claudia Cabella Dr. Giancarlo Cravotto Prof. Silvio Aime Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(1):76-85
Three new magnetic resonance imaging probes that target glutamine transporters have been synthesized. They consist of a Gd‐DOTA‐monoamide moiety (DOTA=1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid) linked through a six carbon atom chain to a vector represented by a glutamine residue bound through α‐carboxylic, γ‐carboxamidic, or α‐amino functionalities. Their uptake by HTC (rat hepatocarcinoma) and healthy rat hepatocytes has shown that the system containing the glutamine vector bound through the α‐carboxylic group displays a markedly higher affinity for tumor cells. The observed behavior is rationalized in terms of the exploitation of an additional glutamine transporter active in hepatic tumor cells. 相似文献
86.
The stability constants of ternary copper(II) complexes with 2,2'-bipyridyl and a dicarboxylic acid (maleic and phthalic) have been determined by means of pH-titrations at 25 +/- 0.1 degrees and an ionic strength of 0.1M (Na,H)ClO(4). The stabilities of ternary complexes are compared with those of similar complexes and related to the size of the chelate rings and the nature of the dicarboxylic ligands. 相似文献
87.
The Role of Ligand Topology in the Decomplexation of Luminescent Lanthanide Complexes by Dipicolinic Acid 下载免费PDF全文
Dr. Federica Mian Dr. Gregorio Bottaro Dr. Roberta Seraglia Dr. Marco Cavazzini Dr. Silvio Quici Prof. Lidia Armelao 《Chemphyschem》2016,17(20):3229-3236
In this study, we present the aqueous solution behavior of two luminescent lanthanide antenna complexes (Eu3+? 1 , Dy3+? 9 ) with different ligand topologies in the presence of dipicolinic acid (DPA, pyridine‐2,6‐dicarboxylic acid). Macrocyclic (1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid, DO3A, 9 ) and acyclic (1,4,7‐triazaheptane‐1,1,7,7‐tetraacetic acid, DTTA, 1 ) ligands have been selected to form a ratiometric pair in which Dy3+? 9 acts as a reference and Eu3+? 1 acts as a probe for the recognition of DPA. The pair of luminescent complexes in water reveals the capability to work as a DPA luminescent sensor. The change of emission intensity of Eu3+ indicates the occurrence of a new sensitization path for the lanthanide cation through excitation of DPA. NMR evidence implies the presence of free 1 and mass spectrometry shows the formation of emitting [EuDPA2]? as a result of a ligand exchange reaction. 相似文献
88.
Bottamauro M Casellato U Scalco C Tamburini S Tomasin P Vigato PA Aime S Barge A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(17):3917-3926
Heterodinuclear lanthanide(III)-sodium(I) complexes [LnNa(L)(Cl)(2)(CH(3)OH)] (Ln=La[bond]Nd, Sm[bond]Lu), where H(2)L is a [1+1] asymmetric compartmental macrocyclic ligand containing a N(3)O(2) Schiff base and a O(3)O(2) crown-ether-like coordination site, have been prepared and characterized by IR, (1)H, (13)C, and (23)Na NMR spectroscopy, mass spectrometry, and electron microscopy. In the solid state, the lanthanide(III) ions coordinate the Schiff-base N(3)O(2) site, and the sodium ion occupies the O(3)O(2) crownlike cavity, as shown by the X-ray crystal structures of the Nd, Eu, Gd, and Yb derivatives. In these complexes, the lanthanide(III) ion is coordinated by two chlorine atoms in the trans position and by three nitrogen and two negatively charged phenol oxygen atoms of the Schiff base, and the ion is heptacoordinated with a pentagonal bipyramidal geometry. The sodium ion is coordinated by three etheric oxygen atoms and the two phenolic oxygens that act as a bridge. A methanol molecule is also coordinated in the apical position of the resulting pentagonal pyramidal polyhedron. A detailed (1)H and (13)C NMR study was carried out in CD(3)OD for both diamagnetic and paramagnetic heterodinuclear complexes [LnNa(L)(Cl)(2)(CH(3)OH)]. The complexes are also isostructural in solution, and their structures parallel those found in the solid state. Moreover, some significative distances determined in the solid state and in solution are comparable. Finally, the potential use of these complexes as molecular probes for the selective recognition of specific metal ions has been tested. In particular, their ability to act as shift reagents and the selectivity of the O(3)O(2) site towards Li(+), Ca(2+), and K(+) were investigated by (23)Na NMR spectroscopy. 相似文献
89.
90.