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491.
We report on the fluorous-assisted synthesis of oligosaccharides using a phenyl ether linker. The phenyl ether linker is stable under both acidic and basic conditions but can be cleaved under mildly acidic conditions after reduction to a vinyl ether. The utility of the method was demonstrated by the synthesis of a trisaccharide. A protected trisaccharide with a light-fluorous tag was directly prepared by one-pot glycosylation using three building blocks that contained a building block with a light-fluorous tag though a phenyl ether. A Birch reduction of the trisaccharide provided a fully deprotected trisaccharide with the fluorous tag attached through a vinyl ether, which was easily purified by solid-phase extraction. The tag was cleaved from the sugar portion by treatment with 3% TFA in MeOH. 相似文献
492.
The reaction of cyclobutylmagnesium carbenoids, which were generated from 1-chlorocyclobutyl p-tolyl sulfoxides with EtMgCl via the sulfoxide-magnesium exchange reaction at low temperature, with carbanions derived from vinyl sulfones with n-BuLi or LDA resulted in the formation of allylidenecyclobutanes in moderate to good yields. The actual reactive species of the sulfones in this reaction were proved to be the lithium α-sulfonyl carbanion of allyl sulfones derived from the vinyl sulfones by double bond migration with the bases used. Mono- and di-substituted allylidenecyclobutanes can be obtained by using a variety of vinyl sulfones. 相似文献
493.
Jun-Kai Zhang 《Journal of organometallic chemistry》2011,696(23):3697-3702
Two nickel(II) complexes (A and B) bearing β-iminoamine ligands, [2-(ArNCH)-C6H4-NMe2] (La, Ar = 2,6-i-Pr2C6H3; Lb, Ar = 2,6-Me2C6H3), were synthesized and characterized by elemental analyses and 1H NMR. X-ray crystal structure of complex B reveals that the six-membered chelate ring adopts a envelope conformation, with nickel(II) atom deviating from the plane of backbone aromatic ring by 1.164 Å. In the presence of methylaluminoxane (MAO), both complexes showed moderate activities of 105 g molNi−1 h−1 for norbornene polymerization. β-iminoamine Ni(II)/MAO catalysts gave unimodal polymers (Mw, 3.16-8.02 × 105 g/mol) with a relatively narrow MWD (Mw/Mn, 1.59-2.14), indicative of single-site catalyst behavior. The obtained polymers are vinyl-type polynorbornenes (PNBs), which are soluble in common solvents such as toluene, cyclohexane and dichlorobenzene. 相似文献
494.
利用沉积沉淀法制备出了La改性Al2O3催化剂,研究不同焙烧温度对La改性Al2O3催化剂用于乙炔气相氢氟化合成氟乙烯反应性能的影响.利用NH3-TPD、Pyridine-FTIR、XRD和Raman等技术对不同温度焙烧的催化剂进行表征,发现焙烧过程能改变催化剂结构的同时也能调变催化剂表面的酸量.经400 °C焙烧的催化剂显示出最高的乙炔转化率(94.6%)、最高的氟乙烯选择性(83.4%)和较低的积炭选择性(0.72%).催化剂的高活性与其表面的高酸量有关,同时积炭的选择性也与其表面的酸中心数量有关. 相似文献
495.
496.
Beatrice Lansbergen Srija Tewari Ireneusz Tomczyk Maik Seemann Henning Louis Buchholz Mike Rippegarten Daniel Chamier Cieminski Dr. Fabio Juliá Prof. Dr. Tobias Ritter 《Angewandte Chemie (International ed. in English)》2023,62(52):e202313659
We report the first reductive vinylation of alkyl iodides. The reaction uses a vinyl thianthrenium salt, a palladium catalyst, and an alkyl zinc intermediate formed in situ to trap the LnPdII(vinyl) complex formed after oxidative addition before it undergoes undesired homocoupling to form butadiene. 相似文献
497.
Xuedi Yuan Dr. Tao Dong Jiaxin Liu Dr. Yingyue Cui Haotian Dong Dr. Du Yuan Prof. Haitao Zhang 《Angewandte Chemie (International ed. in English)》2023,62(30):e202304121
The practical implementation of high-voltage lithium-rich manganese oxide (LRMO) cathode is limited by the unanticipated electrolyte decomposition and dissolution of transition metal ions. The present study proposes a bi-affinity electrolyte formulation, wherein the sulfonyl group of ethyl vinyl sulfone (EVS) imparts a highly adsorptive nature to LRMO, while fluoroethylene carbonate (FEC) exhibits a reductive nature towards Li metal. This interface modulation strategy involves the synergistic use of EVS and FEC as additives to form robust interphase layers on the electrode. As-formed S-endorsed but LiF-assisted configuration cathode electrolyte interphase with a more dominant −SO2− component may promote the interface transport kinetics and prevent the dissolution of transition metal ions. Furthermore, the incorporation of S component into the solid electrolyte interphase and the reduction of its poorly conducting component can effectively inhibit the growth of lithium dendrites. Therefore, a 4.8 V LRMO/Li cell with optimized electrolyte may demonstrate a remarkable retention capacity of 97 % even after undergoing 300 cycles at 1 C. 相似文献
498.
Rubén Miguélez Nina Semleit Carlos Rodríguez-Arias Dr. Pavel Mykhailiuk Prof. Dr. José M. González Prof. Dr. Gebhard Haberhauer Dr. Pablo Barrio 《Angewandte Chemie (International ed. in English)》2023,62(26):e202305296
Selective functionalization of non-activated C(sp3)−H bonds is a major challenge in chemistry, so functional groups are often used to enhance reactivity. Here, we present a gold(I)-catalyzed C(sp3)−H activation of 1-bromoalkynes without any sort of electronic, or conformational bias. The reaction proceeds regiospecifically and stereospecifically to the corresponding bromocyclopentene derivatives. The latter can be readily modified, comprising an excellent library of diverse 3D scaffolds for medicinal chemistry. In addition, a mechanistic study has shown that the reaction proceeds via a so far unknown mechanism: a concerted [1,5]-H shift / C−C bond formation involving a gold-stabilized vinylcation-like transition state. 相似文献
499.
M. Sc. Gerlis von Haugwitz B. Sc. Kian Donnelly M. Sc. Mara Di Filippo Dr. Daniel Breite Max Phippard Dr. Agnes Schulze Dr. Ren Wei Dr. Marcus Baumann Prof. Dr. Uwe T. Bornscheuer 《Angewandte Chemie (International ed. in English)》2023,62(18):e202216962
Poly(vinyl alcohol) (PVA) is a water-soluble synthetic vinyl polymer with remarkable physical properties including thermostability and viscosity. Its biodegradability, however, is low even though a large amount of PVA is released into the environment. Established physical-chemical degradation methods for PVA have several disadvantages such as high price, low efficiency, and secondary pollution. Biodegradation of PVA by microorganisms is slow and frequently involves pyrroloquinoline quinone (PQQ)-dependent enzymes, making it expensive due to the costly cofactor and hence unattractive for industrial applications. In this study, we present a modified PVA film with improved properties as well as a PQQ-independent novel enzymatic cascade for the degradation of modified and unmodified PVA. The cascade consists of four steps catalyzed by three enzymes with in situ cofactor recycling technology making this cascade suitable for industrial applications. 相似文献