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941.
α,β‐Unsaturated Acyl Cyanides as New Bis‐Electrophiles for Enantioselective Organocatalyzed Formal [3+3]Spiroannulation 下载免费PDF全文
Sébastien Goudedranche Dr. Xavier Bugaut Prof. Thierry Constantieux Dr. Damien Bonne Prof. Jean Rodriguez 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):410-415
α,β‐Unsaturated acyl cyanides are key bis‐electrophile substrates for successful domino enantioselective organocatalyzed Michael‐intramolecular acylation domino sequences. This new reactivity has been applied to the synthesis of enantioenriched azaspiro[4,5]decanone ring systems by a formal [3+3]spiroannulation, constituting a rare example of synthesis of glutarimides in an optically active form. 相似文献
942.
An efficient and compact diode-pumped continuous-wave Yb:GdVO4 laser is demonstrated, generating an output power of 4.0 W with an optical conversion efficiency of 61% and a slope efficiency as high as 78%. With increasing pump power the polarization of the laser output changes from sigma to pi, while in a certain intermediate power range the two polarization states coexist with different emission wavelengths. 相似文献
943.
François‐Xavier Felpin Dr. Karinne Miqueu Dr. Jean‐Marc Sotiropoulos Dr. Eric Fouquet Prof. Oier Ibarguren Julia Laudien 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(17):5191-5204
The Pd(OAc)2‐catalyzed Heck reaction of aryl diazonium salts with 2‐arylacrylates led to cis‐stilbenes with good to excellent stereoselectivity. The environmentally friendly protocol developed in this work features low palladium loading in technical‐grade methanol at room temperature under base‐, additive‐, and ligand‐free conditions. The same protocol applied to simple Heck coupling of aryl diazonium salts with methyl acrylate allows astonishingly low palladium loading, down to 0.005 mol %. The stereoselectivity experimentally observed for the synthesis of cis‐stilbenes has been rationalized by DFT calculations. Moreover, the role of methanol in promoting the reaction has been clarified by a computational study. 相似文献
944.
Bizet V Pannecoucke X Renaud JL Cahard D 《Angewandte Chemie (International ed. in English)》2012,51(26):6467-6470
Transfer news: A synthetic approach to chiral β-CF(3)-substituted saturated carbonyl compounds has been developed in which ruthenium complexes efficiently catalyze the redox isomerization of CF(3)-bearing allylic alcohols by an intramolecular suprafacial enantiospecific 1,3-hydrogen transfer (see scheme). This method was used for the enantioselective synthesis of (S)-CF(3)-citronellol. 相似文献
945.
Magnetochemical Complexity of Hexa‐ and Heptanuclear Wheel Complexes of Late‐3d Ions Supported by N,O‐Donor Pyridyl–Methanolate Ligands 下载免费PDF全文
Dr. Kirill Yu. Monakhov Dr. Xavier López Dr. Manfred Speldrich Dr. Jan van Leusen Prof. Dr. Paul Kögerler Prof. Dr. Pierre Braunstein Prof. Dr. Josep M. Poblet 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(13):3769-3781
The scaffold geometries, stability and magnetic features of the (pyridine‐2‐yl)methanolate (L) supported wheel‐shaped transition‐metal complexes with compositions [M6L12] ( 1 ), [Na?(ML2)6]+ ( 2 ), and [M′?(ML2)6]2+ ( 3 ), in which M=CoII, NiII, CuII, and ZnII were investigated with density functional theory (DFT). The goals of this study are manifold: 1) To advance understanding of the magnetism in the synthesized compounds [Na?(ML2)6]+ and [M′?(ML2)6]2+ that were described in Angew. Chem. Int. Ed. 2010 , 49, 4443 ( I ‐{Na?Ni6}, I ‐{Ni′?Ni6}) and Dalton Trans. 2011 , 40, 10526 ( II ‐{Na?Co6}, II ‐{Co′?Co6}); 2) To disclose how the structural, electronic, and magnetic characteristics of 1 , 2 , and 3 change upon varying MII from d7 (Co2+) to d10 (Zn2+); 3) To estimate the influence of the Na+ and M′2+ ions (XQ+) occupying the central voids of 2 and 3 on the external and internal magnetic coupling interactions in these spin structures; 4) To assess the relative structural and electrochemical stabilities of 1 , 2 , and 3 . In particular, we focus here on the net spin polarization, the determination of the strength and the sign of the exchange coupling energies, the rationalization of the nature of the magnetic coupling, and the ground‐state structures of 1 , 2 , and 3 . Our study combines the broken symmetry DFT approach and the model Hamiltonian methodology implemented in the computational framework CONDON 2.0 for the modeling of molecular spin structures, to interpret magnetic susceptibility measurements of I ‐{Na?Ni6} and I ‐{Ni′?Ni6}. We illustrate that whereas the structures, stability and magnetism of 1 , 2 , and 3 are indeed influenced by the nature of 3d transition‐metals in the {M6} rims, the XQ+ ions in the inner cavities of 2 and 3 impact these properties to an even larger degree. As exemplified by I ‐{Ni′?Ni6}, such heptanuclear complexes exhibit ground‐state multiplets that cannot be described by simplistic model of spin‐up and spin‐down metal centers. Furthermore, we assess how future low‐temperature susceptibility measurements at high magnetic fields can augment the investigation of compound 3 with M=Co, Ni. 相似文献
946.
947.
948.
We report the first intermolecular NHC-catalyzed hydroacylation of electron-neutral olefins. Treatment of aromatic aldehydes with cyclopropenes under mild conditions affords valuable acylcyclopropanes in moderate to high yields with an excellent level of diastereocontrol. Preliminary mechanistic studies suggest that product formation occurs via a concerted syn hydroacylation pathway. 相似文献
949.
The definition of the inverse along an element was very recently introduced, and it contains known generalized inverses such as the group, Drazin and Moore–Penrose inverses. In this article, we first prove a simple existence criterion for this inverse in a semigroup, and then relate the existence of such an inverse in a ring to the ring units. 相似文献
950.