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81.
The preparation of a series of mono-naproxen functionalised polyethylene glycol derivatives have been achieved. These compounds feature several different terminal functional groups, the identities of which have been chosen to facilitate conjugation of these hybrid molecules to nanomaterials. 相似文献
82.
This paper describes the synthesis and purification of two 22-residue cyclic peptides, cyclo{[(l-Val-d-Val)4-(l-Val-d-Pro-Gly)]2-} 3 and cyclo{[(d-Leu-l-Leu)4-(d-Leu-l-Pro-Gly)]2-} 4, that were designed to fold into double-stranded antiparallel β-helical structures. Due to intramolecular hydrogen bonding and the conformational constraints imposed by the two reverse-turn segments (d-Pro-Gly and l-Pro-Gly, respectively), the linear precursors to 3 and 4 (lin-3 and lin-4) were expected to adopt preorganized conformations that would bring the N and C termini close together and thereby favor ring closure. Precursors lin-3 and lin-4 were constructed by stepwise Boc solid-phase peptide synthesis using the commercially available alkanesulfonamide ‘safety-catch’ linker and cyclized head-to-tail via the method of cleavage-by-cyclization. The crude cyclic peptides were highly hydrophobic and contained minor impurities that could not be removed solely by reversed-phase HPLC (RP-HPLC); however, two-step purification—first by RP-HPLC with i-PrOH/water gradients, followed by gel-permeation chromatography (GPC) on Sephadex LH-20 with CHCl3/MeOH—afforded both peptides in pure form (≥95% by 1H NMR) and in acceptable yield (23%). Subsequent 1H NMR experiments supported the expected structures of 3 and 4. The successful formation of the 66-membered rings of 3 and 4 is consistent with the notion of conformational preorganization in the linear precursors; furthermore, the protocols for synthesis and purification described should prove useful for preparing additional cyclic β-helical peptides, including longer peptides and peptides having polar residues. 相似文献
83.
Marisa Spiniello Anton Blencowe Greg G. Qiao 《Journal of polymer science. Part A, Polymer chemistry》2008,46(7):2422-2432
A series of fluorescently labeled core cross‐linked star (CCS) polymers were synthesized via the “arm‐first” approach, employing atom transfer radical polymerization (ATRP) to control the resulting architecture. The initiator p‐toluenesulfonyl chloride (TsCl) was used to synthesize “living” poly(methyl methacrylate) (PMMA) macroinitiator, which was subsequently cross‐linked to generate the CCS polymers. Divinylbenzene (DVB) was used as the cross‐linker and 7‐[4‐(trifluoromethyl)coumarin] methacrylamide ( F1 , λex = 343 nm) was added as a fluorescent labeling monomer. A range of PMMA/DVB/ F1 based CCS polymers were synthesized with the core domain made selectively fluorescent by using varying amounts of monomer F1 . The core functionalized stars were characterized using gel permeation chromatography (GPC) equipped with multi‐angle laser light scattering (MALLS), refractive index (RI), and UV–visible detectors. The fluorescence quantum yield (ΦF) and the amount of fluorescent monomer incorporated into the core were quantified by UV–visible and fluorescence spectrophotometry. It was recognized that the overall molecular weights of the stars produced, along with their core molecular weight, decreased as the mol % of monomer F1 was increased relative to cross‐linker. Visual confirmation of F1 incorporation was obtained by fluorescence microscopy of thin polymer films cast on glass substrates. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2422–2432, 2008 相似文献
84.
The use of solid phase synthesis continues to expand as chemists identify methodology that enables complex reactions. Recent efforts in this area have focused on new carbon-carbon bond forming reactions as well as a variety of heterocyclic systems. These examples are described along with updates on new linking strategies for solid phase synthesis. 相似文献
85.
使用不同空间位阻的苯氧链接手臂修饰的聚(苯乙烯基-苯乙烯膦酸)-磷酸氢锆轴向固载手性MnⅢ(Salen)催化剂(Cat1-Cat3),随后在间氯过氧苯甲酸(m-CPBA)为氧化剂的体系中考察了固载催化剂的催化性能. 同时,在相同氧化体系下测试了一系列均相催化剂类似物(Cat4-Cat6). 结果表明,在非均相条件下,可调变苯氧链接手臂的邻位取代基对催化剂活性起着重要作用,环氧化产物的对映选择性随着取代基位阻的增加而增大,但产物转化率有一定程度下降. 此外,非均相催化剂即使在没有轴向助剂的参与下(通常需要添加,为了增大催化活性)仍然表现出非常高的催化活性,尤其对α-甲基苯乙烯反应,其对映选择性从6.8%增加到76.8%,转化率从19.8%上升到90.7%. 制备的非均相催化剂11次的循环使用实验表明,在前5次使用后催化剂活性与对映选择性没有明显变化. 相似文献
86.
An extremely easy and multigram scale synthesis of a new maleimide‐DTPA derivative is described. This bifunctional chelating agent finds application in bioconjugate chemistry because the maleimido group allows easy labeling of thiol‐containing molecules (e.g., proteins, peptides) and the DTPA moiety ensures a strong and stable coordination of metal and radiometal ions such as gadolinium, lutetium, indium, and yttrium. 相似文献
87.
A novel, facile, solid-phase, organic synthesis of 1-(E)-styryl-4-substituted-1,2,3-triazoles in good yields and purities via traceless sulfone linker has been developed. Key steps involved in this synthetic procedure include (i) sulfone alkylation of sulfinate resin with (2-azido-1-iodoethyl)benzene, (ii) [3 + 2] cycloaddition with terminal alkynes in the presence of CuI, and (iii) traceless product release by base-mediated elimination process. 相似文献
88.
89.
Matthias Lehmann Katrin Bahndorf Michael Ohnemus Sabine Roth Steffi Gloza 《Liquid crystals》2013,40(10):1444-1449
The solid-state assisted synthesis opens an easy access to oligobenzoates end-capped with gallic acid, protocatechuic acid or 4-hydroxybenzoic acid etherified with long flexible chains – which are important precursors for liquid crystalline materials. The latter may consist of aliphatic, oligoethyleneoxy and semiperfluorinated chains. The rapid preparation of oligoesters with different peripheries is demonstrated. 相似文献
90.
Dr. Takayuki Arai Keumhee Jang Dr. Yasuhito Koyama Dr. Shigeo Asai Prof. Toshikazu Takata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(19):5917-5923
A supramolecular cross‐linked cross‐linker, capable of introducing rotaxane cross‐links to vinyl polymers, has been developed for the rational synthesis of polyrotaxane networks. The experimental results reveal that the combination of an oligocyclodextrin (OCD) and a terminal bulky group‐tethering macromonomer (TBM) forms a polymer‐network structure having polymerizable moieties through supramolecular cross‐linking. Radical polymerization of a variety of typical vinyl monomers in the presence of the vinylic supramolecular cross‐linker (VSC) afforded the corresponding vinyl polymers cross‐linked through the rotaxane cross‐links (RCP) as transparent stable films in high yields under both photoinitiated and thermal polymerization conditions. A poly(N,N‐dimethylacrylamide)‐based hydrogel synthesized by using VSC, RCPDMAAm, displayed a unique mechanical property. The small‐angle X‐ray scattering (SAXS) results, indicating patterns characteristic of a polyrotaxane network, clearly suggested the presence and role of the rotaxane cross‐links. The confirmation of the introduction of rotaxane‐cross‐links into vinyl polymers strongly reveals the significant usefulness of VSC. 相似文献