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81.
We employ density functional theory with Hubbard U correction or hybrid functionals to study the series of magnetic 3d metal trifluorides MF3 (M = Ti-Ni). Experimental lattice parameters are reproduced with an error margin of 0.5%–4.3%. Cooperative Jahn–Teller distortions are reproduced for MnF3, but also found in TiF3 and CoF3 at smaller levels compared to MnF3. Trends in electronic structure with respect to positions of the d bands are linked to the magnetic properties where M = Ti-Cr are weak magnetic Mott–Hubbard insulators, M = Fe-Ni are strong magnetic charge-transfer insulators and MnF3 falls in between. Our work contributes to the characterization of the relatively unknown NiF3, since FeF3 and CoF3 have similar electronic and magnetic properties. However, NiF3 does not show a Jahn–Teller distortion as present in CoF3. © 2019 Wiley Periodicals, Inc. 相似文献
82.
Philipp Niermeier Sebastian Blomeyer Younes K. J. Bejaoui J. Louis Beckmann Beate Neumann Hans‐Georg Stammler Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2019,58(7):1965-1969
Bidentate boron Lewis acids based on 1,8‐diethynylanthracene were synthesised in two steps by initial stannylation of the terminal alkynes and subsequent tin–boron exchange with different chloroboranes. The reactions were very selective, and the target compounds were obtained in high purity and good to excellent yields. Complexation experiments of 1,8‐bis[(diphenylboranyl)ethynyl]anthracene with nitrogen bases (pyridine, pyrimidine, TMEDA) afforded three stable adducts, which were structurally characterised by X‐ray diffraction. Competition experiments demonstrated the selective exchange of guests, and quantum‐chemical calculations provided information on their energetics. NMR experiments at low temperature gave insight into the dynamic behaviour of the TMEDA adduct. 相似文献
83.
The solid-state structure of the triple-decker salt [Cp*Fe(-5:5-C4Me4P)RuCp*] · CF3SO3 shows orientational disorder for the pseudosymmetric cations. A chemically related compound was used to define a restrained structure model. Comparison of different refinement strategies proves that this restrained model is superior to an unrestrained treatment. 相似文献
84.
Variability of UV irradiance in Europe 总被引:1,自引:1,他引:0
Seckmeyer G Pissulla D Glandorf M Henriques D Johnsen B Webb A Siani AM Bais A Kjeldstad B Brogniez C Lenoble J Gardiner B Kirsch P Koskela T Kaurola J Uhlmann B Slaper H den Outer P Janouch M Werle P Gröbner J Mayer B de la Casiniere A Simic S Carvalho F 《Photochemistry and photobiology》2008,84(1):172-179
85.
Werner Uhl Prof. Dr. Michael Claesener Sima Haddadpour Beate Jasper Ines Tiesmeyer Sarina Zemke 《无机化学与普通化学杂志》2008,634(15):2889-2896
Hydrogallation Reactions Involving the Monoalkynes H5C6‐C≡C‐SiMe3 and H5C6‐C≡C‐CMe3 – cis/trans Isomerisation and Substituent Exchange Phenyl‐trimethylsilylethyne, H5C6‐C≡C‐SiMe3, reacted with different dialkylgallium hydrides, R2Ga‐H (R = Me, Et, nPr, iPr, tBu), by the addition of one Ga‐H bond to its C≡C triple bond (hydrogallation). The gallium atoms attacked selectively those carbon atoms, which were also attached to trimethylsilyl groups. The cis arrangement of Ga and H across the resulting C=C double bonds resulted only for the sterically most shielded di(tert‐butyl)gallium derivative, while in all other cases spontaneous cis/trans rearrangement occurred with the quantitative formation of the trans addition products. The diethyl compound Et2Ga‐C(SiMe3)=C(H)‐C6H5 ( 2 ) gave by substituent exchange the secondary products EtGa[C(SiMe3)=C(H)‐C6H5]2 ( 7 , Z,Z) and Ga[C(SiMe3)=C(H)‐C6H5]3 ( 8 ). Interestingly, compound 8 has two alkenyl groups with a Z configuration, while the third C=C double bond has the cis arrangement of Ga and H (E configuration). The reversibility of the cis/trans isomerisation of hydrogallation products was observed for the first time. tert‐Butyl‐phenylethyne gave the simple addition product, R2Ga(C6H5)=C(H)‐CMe3 ( 9 ), only with di(n‐propyl)gallium hydride. 相似文献
86.
Dr. Lucas Wickemeyer Prof. Dr. Israel Fernández Beate Neumann Dr. Hans-Georg Stammler Prof. Dr. Norbert W. Mitzel 《Angewandte Chemie (International ed. in English)》2023,62(11):e202216943
The reaction of the oxygen-bridged frustrated Lewis pairs (FLPs) tBu2P−O−Si(C2F5)3 ( 1 ) and tBu2P−O−AlBis2 ( 2 ) with azobenzene, promoted by UV irradiation, led to a selective complexation of the cis-isomer. The addition product of 2 is stable, while the adduct of 1 isomerizes in solution in an ortho-benzidine-like [3,3]-rearrangement by cleavage of the N−N bond, saturation of the nitrogen atoms with hydrogen atoms and formation of a new bond between two phenyl ortho-carbon atoms. Similar rearrangements take place with different para-substituted azobenzenes (R=Me, OMe, Cl) and di(2-naphthyl)diazene, while ortho-methylated azo compounds do not form adducts with 1 . All adducts were characterized by multinuclear NMR spectroscopy and elemental analyses and the mechanism of the rearrangement was explored by quantum-chemical calculations. 相似文献
87.
Dr. Jianing Xie Dr. Axel Pahl Dr. Adrian Krzyzanowski Anna Krupp Dr. Jie Liu Sandra Koska Beate Schölermann Dr. Ruirui Zhang Jana Bonowski Dr. Sonja Sievers Prof. Dr. Carsten Strohmann Dr. Slava Ziegler Dr. Michael Grigalunas Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2023,62(48):e202310222
Monoterpene indole alkaloids (MIAs) are endowed with high structural and spatial complexity and characterized by diverse biological activities. Given this complexity-activity combination in MIAs, rapid and efficient access to chemical matter related to and with complexity similar to these alkaloids would be highly desirable, since such compound classes might display novel bioactivity. We describe the design and synthesis of a pseudo-natural product (pseudo-NP) collection obtained by the unprecedented combination of MIA fragments through complexity-generating transformations, resulting in arrangements not currently accessible by biosynthetic pathways. Cheminformatic analyses revealed that both the pseudo-NPs and the MIAs reside in a unique and common area of chemical space with high spatial complexity-density that is only sparsely populated by other natural products and drugs. Investigation of bioactivity guided by morphological profiling identified pseudo-NPs that inhibit DNA synthesis and modulate tubulin. These results demonstrate that the pseudo-NP collection occupies similar biologically relevant chemical space that Nature has endowed MIAs with. 相似文献
88.
Christian Schramm Beate Rinderer Wolfgang H. Binder Richard Tessadri Heinz Duelli 《Journal of Sol-Gel Science and Technology》2008,45(1):83-88
(3-Triethoxysilylpropyl)succinic anhydride (TESP-SA) is an organo-functional silicon compound that can be converted into a
polysilsesquioxane when it is hydrolyzed and subsequently subjected to a condensation reaction at elevated temperatures (>160 °C).
If this process is performed without sodium hypophosphite (SHP), a hard solid material is obtained. In contrast, the condensation
reaction of TESP-SA in conjunction with SHP results in the formation of a foamed, brittle material with closed macro cells.
The foam was characterized by means of various analytical methods (FT-IR, 29Si MAS NMR, XRD, TG-MS, SEM).
相似文献
Christian SchrammEmail: |
89.
Nico Schwarze Dr. Simon Steinhauer Beate Neumann Dr. Hans‐Georg Stammler Prof. Dr. Berthold Hoge 《Angewandte Chemie (International ed. in English)》2016,55(52):16156-16160
Tris(pentafluoroethyl)silane, which is conveniently accessible by the treatment of Si(C2F5)3X (X=Cl, Br) with Bu3SnH, was successfully employed for hydrosilylation reactions. In the presence of a palladium catalyst, hydrosilylation of phenylacetylene with Si(C2F5)3H affords the product of an α‐addition whereas the reaction of trimethylsilylacetylene with the silane leads to the β‐trans product. Tris(pentafluoroethyl)silane can be deprotonated by sterically demanding bases such as lithium diisopropylamide at low temperatures to give the corresponding silanide ion. The addition of crown ethers or cryptands to this highly reactive species enabled the isolation and characterization of salt‐like tris(pentafluoroethyl)silanide at room temperature. 相似文献
90.
Nico Schwarze Dr. Simon Steinhauer Beate Neumann Dr. Hans‐Georg Stammler Prof. Dr. Berthold Hoge 《Angewandte Chemie (International ed. in English)》2016,55(52):16161-16164
The tris(pentafluoroethyl)silanide anion is accessible by the deprotonation of Si(C2F5)3H at low temperatures. Subsequent quenching of the resulting salt‐like compounds with suitable electrophiles, such as transition‐metal complexes or Group 14 element halides, leads to a plethora of novel tris(pentafluoroethyl)silane derivatives. This underlines the versatility of Li[Si(C2F5)3] as a powerful nucleophilic transfer reagent. 相似文献