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排序方式: 共有184条查询结果,搜索用时 343 毫秒
71.
Dr. Sandip Murarka Zhi‐Jun Jia Dr. Christian Merten Dr. Constantin‐G. Daniliuc Dr. Andrey P. Antonchick Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(26):7653-7656
We report a rhodium(II)‐catalyzed highly enantioselective 1,3‐dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α‐diazoketone‐derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. 相似文献
72.
为支持在并行设计过程中设计特征模型到加工特征模型的逐步转换,提出了局部特征识别的方法.在并行设计中,设计特征模型和加工特征模型通过面名历史图共享零件的实体模型,设计特征的变动通过局部特征识别自动地转换为相应的加工特征.局部特征识别是由基于最小条件子图特征识别方法改进来的,它以零件的局部区域为识别对象,通过搜索匹配局部区域构成的边界模式,识别出该局部区域中所包含的加工特征.局部特征识别方法的特点是只对设计中发生变动的区域进行识别. 相似文献
73.
Kronig S Theuergarten E Holschumacher D Bannenberg T Daniliuc CG Jones PG Tamm M 《Inorganic chemistry》2011,50(15):7344-7359
A variety of Lewis acid-base pairs consisting of tris(pentafluorophenyl)borane, B(C(6)F(5))(3), in combination with sterically demanding five- and six-membered N-heterocyclic carbenes (NHCs) of the imidazolin-2-ylidene, imidazolidin-2-ylidene, and tetrahydropyrimidin-2-ylidene types were investigated with respect to their potential to act as frustrated Lewis pairs (FLP) by reaction with dihydrogen (H(2)) and tetrahydrofuran (THF). A sufficient degree of "frustration" was usually established by introduction of a 1,3-di-tert-butyl or 1,3-diadamantyl carbene substitution pattern, which allows an unquenched acid-base reactivity and thus leads to heterolytic dihydrogen activation and ring-opening of THF. In contrast, 1,3-bis(2,6-diisopropylphenyl)-substituted carbenes showed ambiguous behavior, and the corresponding five-membered imidazolin-2-ylidene formed a stable carbene-B(C(6)F(5))(3) adduct, whereas fast C-F activation and formation of a zwitterionic pyrimidinium-fluoroborate was observed for the six-membered tetrahydropyrimidin-2-ylidene. A stable adduct was also isolated for the combination of the acyclic carbene bis(diisopropylamino)methylene with B(C(6)F(5))(3), and consequently no reactivity toward H(2) and THF was observed. To rationalize the reactivity of the carbene-borane Lewis pairs, the thermodynamics of adduct formation with B(C(6)F(5))(3) were calculated for 10 different carbenes; the stability (or instability) of these adducts can be used as a good measure of the degree of "frustration". 相似文献
74.
Alain C. Tagne Kuate Swagat K. Mohapatra Constantin G. Daniliuc Peter G. Jones Matthias Tamm 《Journal of organometallic chemistry》2012,696(26):4281-4292
Cp-functionalized monotroticenes [(η7-C7H7)Ti(η5-C5H4E)] (2, E = Ph2SiCl; 3, E = tBu2SnCl; 12, E = I) and bitroticenes [(η7-C7H7)Ti(η5-C5H4)]2E′ (5, E′ = PPh; 6, E′ = BN(SiMe3)2; 7, E′ = Cp2Ti) were prepared by salt elimination metathesis between the monolithiated troticene [(η7-C7H7)Ti(η5-C5H4Li)]·pmdta (1b) (pmdta = N,N′,N′,N″,N″-pentamethyldiethylene-triamine) and the appropriate electrophile. The troticenyl-substituted zirconocene monochloride [(η7-C7H7)Ti(η5-C5H4ZrClCp*2)] (Cp* = η5-C5Me5) (8) and hafnocene ethoxide [(η7-C7H7)Ti{η5-C5H4Hf(OEt)Cp2}] (Cp = η5-C5H5) (11), and the heterobimetallic μ-oxo complexes [(η7-C7H7)Ti(η5-C5H4MCp2)]2O (9, M = Zr; 10, M = Hf) were obtained instead of the expected zircona- and hafna[1]troticenophanes by reaction of the dilithiated troticene [(η7-C7H6Li)Ti(η5-C5H4Li)]·pmdta (1a) with [Cp2MCl2] (M = Zr, Hf) or [Cp*2ZrCl2] in stoichiometric amounts. These compounds were characterized by single crystal X-ray diffraction analyses and, in the case of 2, 3, 5–7, 9, 10 and 12, also by elemental analyses and 1H, 13C and 119Sn NMR spectroscopy. Exposure of the troticenyl organotin chloride 3 to moisture resulted in its partial hydrolysis and formation of the organostannoxane-bridged bitroticene 4, while palladium-catalyzed Negishi C–C cross-coupling reaction between the troticenylzinc chloride [(η7-C7H7)Ti(η5-C5H4ZnCl)] (13) and the iodotroticene 12 or iodobenzene (PhI) led to the fulvalene complexes [(η7-C7H7)Ti(η5-C5H4)]2 (14) and [(η7-C7H7)Ti(η5-C5H4Ph)] (15). Compound 4 displays an unsymmetrical structure with the troticenyl fragments cis with respect to the Sn–O–Sn core, whereas compound 14 is centrosymmetrically trans oriented. 相似文献
75.
Glöckner A Daniliuc CG Freytag M Jones PG Tamm M 《Chemical communications (Cambridge, England)》2012,48(52):6598-6600
The complex [(η(7)-C(7)H(7))Zr{N(SiMe(3))(2)}(thf)] (2) loses THF upon sublimation to afford a chain polymer consisting of [(η(7)-C(7)H(7))Zr{N(SiMe(3))(2)}] (3) units; they are connected by cycloheptatrienyl ligands in an unprecedented antifacial η(7):η(2)-bridging mode. The basicity of the bis(trimethylsilyl)amido ligand can also be used to introduce other ligands by acid-base reactions. 相似文献
76.
77.
SK Podiyanachari R Fröhlich CG Daniliuc JL Petersen C Mück-Lichtenfeld G Kehr G Erker 《Angewandte Chemie (International ed. in English)》2012,51(35):8830-8833
Let's split: Reaction of the zirconium complex A with Piers' borane [HB(C(6) F(5) )(2) ] yields the unusual borylalkyne zirconocene complex B which reacts with dihydrogen, activating it to give the doubly hydrido bridged alkyne zirconium complex C. 相似文献
78.
79.
Volker Wedek Ruben VanLommel Constantin G. Daniliuc Frank DeProft Ulrich Hennecke 《Angewandte Chemie (International ed. in English)》2019,58(27):9239-9243
The use of a new class of unsymmetrical cinchona‐alkaloid‐based, phthalazine‐bridged organocatalysts enabled the highly enantioselective dichlorination of unfunctionalized alkenes. In combination with the electrophilic chlorinating agent 1,3‐dichloro‐5,5‐dimethylhydantoin (DCDMH) and triethylsilyl chloride (TES‐Cl) as the source of nucleophilic chloride, 1‐aryl‐2‐alkyl alkenes were dichlorinated with enantioselectivities of up to 94:6 er. Initial mechanistic investigations suggest that no free chlorine is formed, and by replacement of the chloride by fluoride, enantioselective chlorofluorinations of alkenes are possible. 相似文献
80.
Jan Phillip Lemmerhirt Andreas Isaak Rongfang Liu Max Kock Constantin G. Daniliuc Kenneth A. Jacobson Laura H. Heitman Anna Junker 《Molecules (Basel, Switzerland)》2022,27(7)
The adenosine A3 receptor is a promising target for treating and diagnosing inflammation and cancer. In this paper, a series of bicyclo[3.1.0]hexane-based nucleosides was synthesized and evaluated for their P1 receptor affinities in radioligand binding studies. The study focused on modifications at 1-, 2-, and 6-positions of the purine ring and variations of the 5′-position at the bicyclo[3.1.0]hexane moiety, closing existing gaps in the structure–affinity relationships. The most potent derivative 30 displayed moderate A3AR affinity (Ki of 0.38 μM) and high A3R selectivity. A subset of compounds varied at 5′-position was further evaluated in functional P2Y1R assays, displaying no off-target activity. 相似文献