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61.
Mihael Erakovi Dominik Cin
i Kreimir Mol
anov Vladimir Stilinovi 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(44):15849-15853
The covalent nature of strong N?Br???N halogen bonds in a cocrystal ( 2 ) of N‐bromosuccinimide ( NBS ) with 3,5‐dimethylpyridine ( lut ) was determined from X‐ray charge density studies and compared to a weak N?Br???O halogen bond in pure crystalline NBS ( 1 ) and a covalent bond in bis(3‐methylpyridine)bromonium cation (in its perchlorate salt ( 3 ). In 2 , the donor N?Br bond is elongated by 0.0954 Å, while the Br???acceptor distance of 2.3194(4) is 1.08 Å shorter than the sum of the van der Waals radii. A maximum electron density of 0.38 e Å?3 along the Br???N halogen bond indicates a considerable covalent contribution to the total interaction. This value is intermediate to 0.067 e Å?3 for the Br???O contact in 1 , and approximately 0.7 e Å?3 in both N?Br bonds of the bromonium cation in 3 . A calculation of the natural bond order charges of the contact atoms, and the σ*(N1?Br) population of NBS as a function of distance between NBS and lut , have shown that charge transfer becomes significant at a Br???N distance below about 3 Å. 相似文献
62.
Zheng Wang Cheng‐Yi Zhu Shao‐Yun Yin Zhang‐Wen Wei Jian‐Hua Zhang Ya‐Nan Fan Ji‐Jun Jiang Mei Pan Cheng‐Yong Su 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3519-3523
Long persistent luminescence (LPL) materials have a unique photophysical mechanism to store light radiation energy for subsequent release. However, in comparison to the common UV source, white‐light (WL) and near‐infrared (NIR) excited LPL is scarce. Herein we report a metal–organic supramolecular box based on a D–π–A‐type ligand. Owing to the integrated one‐photon absorption (OPA) and two‐photon absorption (TPA) attributes of the ligand, the heavy‐atom effect of the metal center, as well as π‐stacking and J‐aggregation states in the supramolecular assembly, LPL can be triggered by all wavebands from the UV to the NIR region. This novel designed supramolecular kit to afford LPL by both OPA and TPA pathways provides potential applications in anti‐counterfeiting, camouflaging, decorating, and displaying, among others. 相似文献
63.
Xenia Engelmann Deesha D. Malik Teresa Corona Katrin Warm Erik R. Farquhar Marcel Swart Wonwoo Nam Kallol Ray 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(12):4052-4056
The generation of a nonheme oxoiron(IV) intermediate, [(cyclam)FeIV(O)(CH3CN)]2+ ( 2 ; cyclam=1,4,8,11‐tetraazacyclotetradecane), is reported in the reactions of [(cyclam)FeII]2+ with aqueous hydrogen peroxide (H2O2) or a soluble iodosylbenzene (sPhIO) as a rare example of an oxoiron(IV) species that shows a preference for epoxidation over allylic oxidation in the oxidation of cyclohexene. Complex 2 is kinetically and catalytically competent to perform the epoxidation of olefins with high stereo‐ and regioselectivity. More importantly, 2 is likely to be the reactive intermediate involved in the catalytic epoxidation of olefins by [(cyclam)FeII]2+ and H2O2. In spite of the predominance of the oxoiron(IV) cores in biology, the present study is a rare example of high‐yield isolation and spectroscopic characterization of a catalytically relevant oxoiron(IV) intermediate in chemical oxidation reactions. 相似文献
64.
Alexandria G. Mullins Nicholas K. Pinkin Joshua A. Hardin Marcey L. Waters 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(16):5336-5339
The methylation states of Lys and Arg represent a particularly challenging set of targets to distinguish selectively in water using synthetic receptors. To date, trimethyllysine (Kme3) is the only post translational modification (PTM) of the eight possible methylation states of Lys and Arg that can be recognized selectively. Here, we report the first synthetic receptor capable of selectively recognizing asymmetric dimethylarginine (Rme2a). This was achieved by using a biased dynamic combinatorial chemistry (DCC) library to generate a receptor mimicking the 5‐sided box‐like shape of Rme2 reader proteins, a feature that has been hypothesized to impart selectivity. Additionally, we synthesized a thioether‐linked analogue of the resulting receptor to provide a novel scaffold with maintained selectivity but greater stability. This work introduces strategies that can be applied towards achieving selectivity based on subtle differences in hydrophilic guests in aqueous solutions. 相似文献
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Richard C. Brewster Jack T. Suitor Adam W. Bennett Stephen Wallace 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12539-12544
Microorganisms can be programmed to perform chemical synthesis via metabolic engineering. However, despite an increasing interest in the use of de novo metabolic pathways and designer whole‐cells for small molecule synthesis, the inherent synthetic capabilities of native microorganisms remain underexplored. Herein, we report the use of unmodified E. coli BL21(DE3) cells for the reduction of keto‐acrylic compounds and apply this whole‐cell biotransformation to the synthesis of aminolevulinic acid from a lignin‐derived feedstock. The reduction reaction is rapid, chemo‐, and enantioselective, occurs under mild conditions (37 °C, aqueous media), and requires no toxic transition metals or external reductants. This study demonstrates the remarkable promiscuity of central metabolism in bacterial cells and how these processes can be leveraged for synthetic chemistry without the need for genetic manipulation. 相似文献
68.
Dian Niu Yuqian Jiang Lukang Ji Guanghui Ouyang Minghua Liu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6007-6011
Multiple noncovalent interactions can drive self‐assembly through different pathways. Here, by coordination‐assisted changes in π‐stacking modes between chromophores in pyrene‐conjugated histidine (PyHis), a self‐assembly system with reversible and inversed switching of supramolecular chirality, as well as circularly polarized luminescence (CPL) is described. It was found that l ‐PyHis self‐assembled into nanofibers showing P‐chirality and right‐handed CPL. Upon ZnII coordination, the nanofibers changed into nanospheres with M‐chirality, as well as left‐handed CPL. The process is reversible and the M‐chirality can change to P‐chirality by removing the ZnII ions. Experimental and theoretical models unequivocally revealed that the cooperation of metal coordination and π‐stacking modes are responsible the reversible switching of supramolecular chirality. This work not only provides insight into how multiple noncovalent interactions regulate self‐assembly pathways. 相似文献
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