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排序方式: 共有1321条查询结果,搜索用时 46 毫秒
931.
Damien Qumener Valrie Hroguez Yves Gnanou 《Journal of polymer science. Part A, Polymer chemistry》2006,44(9):2784-2793
Novel water‐soluble ruthenium carbene complexes with finely tuned structure and properties in solution are reported. These ruthenium‐based initiators were found to exhibit great catalytic activity in aqueous miniemulsion ring‐opening metathesis polymerization of norbornene. Stable particles of polynorbornene could be generated in the 200–250 nm size range stabilized with a nonionic surfactant (polystyrene‐b‐poly(ethylene oxide)). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2784–2793, 2006 相似文献
932.
A new type of Ind-NHC ligand precursor (Ind = indenyl), [C9H7-(CH2)3-(CH{NCHCHNiPr})]Br (HL·HBr, 1), was designed and prepared. The reaction of in situ generated anionic indenyl-functionalized NHC ligand LLi with (DME)NiCl2 affords a novel mono-ligand Ni(II) bromide, [C9H6-(CH2)3-(C{NCHCHNiPr})]NiBr (2), which was characterized by elemental analysis, NMR and X-ray crystal determination. Complex 2 in combination with NaBPh4 can catalyze the polymerization of styrene at 80 °C. 相似文献
933.
Dr. Jochen Kratsch Prof. Dr. Peter W. Roesky 《Angewandte Chemie (International ed. in English)》2014,53(2):376-383
Transition‐metal carbene complexes have been known for about 50 years and widely applied as reagents and catalysts in organic transformations. In contrast, the carbene chemistry of the rare‐earth metals is much less developed, but has attracted the research interest in the recent years. In this field rare‐earth‐metal alkylidene, especially methylidene, compounds are an emerging class of compounds with a high synthetic potential for organometallic chemistry and maybe in the future also for organic chemistry. 相似文献
934.
Dr. Florie Lavigne Dr. Aimée El Kazzi Yannick Escudié Dr. Eddy Maerten Dr. Tsuyoshi Kato Dr. Nathalie Saffon‐Merceron Prof. Vicenç Branchadell Prof. Fernando P. Cossío Dr. Antoine Baceiredo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12528-12536
The synthesis of a novel family of cyclic push–pull carbenes, namely, azavinylidene phosphoranes, is described. The methodology is based on a formal [3+2] cycloaddition between terminal alkynes and phosphine–imines followed by an oxidation/deprotonation step. Carbenes 6 , obtained by simple deprotonation, exhibit typical transient carbene reactivity like the intramolecular C?H insertion reaction and a pronounced ambiphilic character exemplified by [2+1] cycloaddition with electron‐poor methyl acrylate. Owing to the cyclic structure, carbenes 6 also exhibit an excellent coordination ability toward transition metals. RhI complex 10 was obtained in excellent yield and was fully characterized by multinuclear NMR spectroscopy and X‐ray crystallography. The corresponding RhI–carbonyl complex was also prepared; this indicates that carbenes 6 belong to the strongest σ‐donating ligands to date. DFT calculations confirmed the high σ‐donation ability of 6 and their classification as push–pull carbenes with a relatively small singlet–triplet energy gap of 23.2–24.3 kcal mol?1. 相似文献
935.
Synthesis of 3-acyl-5,6-dihydro-1,4-oxathiines has been achieved via reactions of thiiranes and α-diazo-β-1,3-dicarbonyl compounds under microwave and copper sulfate-assisted conditions. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-1,4-oxathiines from readily available thiiranes and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes. The reaction mechanism was also proposed. 相似文献
936.
Alexander Bechtoldt Hans‐Wolfram Lerner Michael Bolte 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(6):448-451
The aurophilicity exhibited by AuI complexes depends strongly on the nature of the supporting ligands present and the length of the Au–element (Au—E) bond may be used as a measure of the donor–acceptor properties of the coordinated ligands. A binuclear iron–gold complex, [1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene‐2κC2]dicarbonyl‐1κ2C‐(1η5‐cyclopentadienyl)gold(I)iron(II)(Au—Fe) benzene trisolvate, [AuFe(C5H5)(C27H36N2)(CO)2]·3C6H6, was prepared by reaction of K[CpFe(CO)2] (Cp is cyclopentadienyl) with (NHC)AuCl [NHC = 1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene]. In addition to the binuclear complex, the asymmetric unit contains three benzene solvent molecules. This is the first example of a two‐coordinated Au atom bonded to an Fe and a C atom of an N‐heterocyclic carbene. 相似文献
937.
A Dimetalloxycarbene Bonding Mode and Reductive Coupling Mechanism for Oxalate Formation from CO2 下载免费PDF全文
Albert Paparo Dr. Jared S. Silvia Dr. Christos E. Kefalidis Dr. Thomas P. Spaniol Prof. Dr. Laurent Maron Prof. Dr. Jun Okuda Prof. Dr. Christopher C. Cummins 《Angewandte Chemie (International ed. in English)》2015,54(31):9115-9119
We describe the stable and isolable dimetalloxycarbene [(TiX3)2(μ2‐CO2‐κ2C,O:κO′)] 5 , where X=N‐(tert‐butyl)‐3,5‐dimethylanilide, which is stabilized by fluctuating μ2‐κ2C,O:κ1O′ coordination of the carbene carbon to both titanium centers of the dinuclear complex 5 , as shown by variable‐temperature NMR studies. Quantum chemical calculations on the unmodified molecule indicated a higher energy of only +10.5 kJ mol?1 for the μ2‐κ1O:κ1O′ bonding mode of the free dimetalloxycarbene compared to the μ2‐κ2C,O:κ1O′ bonding mode of the masked dimetalloxycarbene. The parent cationic bridging formate complex [(TiX3)2(μ2‐OCHO‐κO:κO′)][B(C6F5)4], 4 [B(C6F5)4], was simply deprotonated with the strong base K(N(SiMe3)2) to give 5 . Complex 5 reacts smoothly with CO2 to generate the bridging oxalate complex [(TiX3)2(μ2‐C2O4‐κO:κO′′)], 6 , in a C? C bond formation reaction commonly anticipated for oxalate formation by reductive coupling of CO2 on low‐valent transition‐metal complexes. 相似文献
938.
Direct X‐Ray Scattering Evidence for Metal–Metal Interactions in Solution at the Molecular Level 下载免费PDF全文
Alba Vellé Dr. Manuel Iglesias Lauren B. Fullmer Dr. Sara Goberna‐Ferrón Dr. May Nyman Dr. Pablo J. Sanz Miguel 《Angewandte Chemie (International ed. in English)》2015,54(43):12762-12766
The study of the aggregation of small molecules in solution induced by metallophilic interactions has been traditionally performed by spectroscopic methods through identification of chemical changes in the system. Herein we demonstrate the use of SAXS (small‐angle X‐ray scattering) to identify structures in solution, taking advantage of the excellent scattering intensity of heavy metals which have undergone association by metallophilic interactions. An analysis of the close relationship between solid‐state and solution arrangements of a dynamic [Ag2(bisNHC)2]2+ (NHC=N‐heterocyclic carbene) system, and how they are complementary to each other, is reported. 相似文献
939.
Design,Synthesis, and Structural Analysis of Divalent NI Compounds and Identification of a New Electron‐Donating Ligand 下载免费PDF全文
Prof. Dr. Prasad V. Bharatam Minhajul Arfeen Neha Patel Priyanka Jain Sonam Bhatia Prof. Dr. Asit K. Chakraborti Dr. Sadhika Khullar Vijay Gupta Prof. Dr. Sanjay K. Mandal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):1088-1096
The dative‐bond representation (L→E) in compounds with main group elements (E) has triggered extensive debate in the recent past. The scope and limits of this nonclassical coordination bond warrant comprehensive exploration. Particularly compounds with (L→N←L′)+ arrangement are of special interest because of their therapeutic importance. This work reports the design and synthesis of novel chemical species with the general structural formula (L→N←L′)+ carrying the unusual ligand cyclohexa‐2,5‐diene‐4‐(diaminomethynyl)‐1‐ylidene. Four species belonging to the (L→N←L′)+ class carrying this unconventional ligand were synthesized. Quantum chemical and X‐ray diffraction analyses showed that the electronic and geometric parameters are consistent with those of already reported divalent NI compounds. The molecular orbital analysis, geometric parameters, and spectral data clearly support the L→N and N←L′ interactions in these species. The newly identified ligand has the properties of a reactive carbene and high nucleophilicity. 相似文献
940.
Novel ruthenium‐1,3‐dialkylimidazolin‐2‐ylidene complexes ( 2a–e ) have been prepared and characterized by C, H, N analysis, 1H‐NMR and 13C‐NMR. The ortho position of the aromatic ring of pyridyl group substituted aromatic compound was directly arylated with aryl bromides and chlorides in the presence of a catalytic amount of [RuCl2(1,3‐dialkylimidazolin‐2‐ylidene)] complexes. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献