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131.
A simple, highly efficient synthetic protocol is developed for the synthesis of unsymmetrical diaryl vinyl selenides from diaryldiselenide and β-bromo styrene under transition-metal free conditions in N,N′-dimethyl propylene urea and 130 °C to afford high yields and excellent selectivities. This method provides a new strategy to fabricate a wide variety of important substituted molecular skeletons and an alternative to conventionally used metal salts, additives, and ligands. 相似文献
132.
Prof. Dr. Shigehisa Akine Masato Miyashita Prof. Dr. Tatsuya Nabeshima 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(6):1432-1435
A closed metallomolecular cage based on the tris(saloph) framework, in which its aperture can be opened by disulfide exchange, was designed. At the apertures of the molecular cage, bridging diamine ligands having a disulfide bond were introduced to close the cage structure. These bridging ligands efficiently blocked the uptake of a guest, Cs+, but the presence of a thiolate anion significantly accelerated the guest uptake. This clearly means that this cage complex became open by the addition of the thiolate anion, because the cage closure becomes more dynamic due to the disulfide exchange reaction. 相似文献
133.
MoS_2具有独特的二维层状结构,被广泛用于加氢脱硫过程以及HER反应,而且可以通过减少MoS_2的颗粒尺寸以及层数来进一步改善其催化活性.通过剥离方法得到的MoS_2纳米片虽然表现出优良的加氢脱硫活性,但容易团聚使其循环使用性能很差.如果通过引入纳米碳将单层的MoS_2纳米片进行有效"隔离",则可明显降低团聚的可能性,从而改善其催化性能和稳定性.本文通过一步水热法制备出了碳嵌入的MoS_2纳米颗粒(MoS_2@C),将其应用于硝基苯类化合物的氢转移反应中表现出了非常好的催化性能.进一步通过粉末X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)和在线质谱检测等手段研究了层间距增加的MoS_2催化剂在硝基苯类化合物的氢转移反应中催化性能提升的原因.XRD,SEM和TEM结果表明,通过引入碳材料可以明显增加MoS_2的层间距,同时减小其颗粒尺寸,而且使MoS_2表现出弯曲的(002)晶面.由于存在一定的曲率,这种(002)晶面也会表现出一定的催化能力.氮气物理吸附结果表明,这种MoS_2@C复合物具有较高的比表面积(89 m~2g~(-1))和明显的介孔结构(~20 nm),在催化反应中有利于底物扩散,进而改善催化性能.XPS结果显示,与体相的MoS_2相比,MoS_2@C表面暴露出更多的不饱和Mo原子(Mo/S=0.71(MoS_2@C)vs Mo/S=0.63(MoS_2)),形成了独特的S-Mo-O结构以及缺陷结构.在硝基苯类化合物的氢转移反应中,层间距增加的MoS_2@C由于暴露出更多的活性位和具有弯曲的(002)晶面,表现出了更高的催化活性–(TOF=3.66 s~(-1) vs 1.24 s~(-1)(MoS_2)).通过质谱对反应过程的追踪发现,在只有肼存在的条件下,MoS_2@C催化肼分解的主要气相产物是氨气.这说明MoS_2@C能够使肼发生N-N键的断裂.而当肼和硝基苯同时存在的条件下,质谱检测的气相产物主要是氮气,表明硝基苯的存在可以诱导肼逐步发生N-H键断裂,在催化剂表面形成活性的H物种,进而转移到硝基苯上使其还原得到苯胺.使用偶氮苯和氧化偶氮苯作为反应底物,发现MoS_2@C很难使其还原为苯胺,这说明在该催化体系中,硝基苯的还原过程主要是沿着直接路径(硝基苯-亚硝基苯-苯胺)进行的. 相似文献
134.
An efficient approach for S-methylation of diaryl disulfides with di-tert-butyl peroxide under metal-free and neutral conditions was established. The present protocol shows good functional group tolerance to afford aryl methyl sulfides in moderate to good yields. 相似文献
135.
Cyclic and linear amidines effectively catalyzed the reaction of carbon disulfide and episulfides under mild conditions, such as ordinary pressure and ambient temperature, to give the corresponding cyclic trithiocarbonates in high yields. 相似文献
136.
《Helvetica chimica acta》2018,101(1)
The glycosylation of cell‐penetrating poly(disulfide)s (CPDs) is introduced to increase the solubility of classical CPDs and to achieve multifunctional cellular uptake. With the recently developed sidechain engineering, CPDs decorated with α‐d ‐glucose (Glu), β‐d ‐galactose (Gal), d ‐trehalose (Tre), and triethyleneglycol (TEG) were readily accessible. Confocal laser scanning microscopy images of HeLa Kyoto cells incubated with the new CPDs at 2.5 μm revealed efficient uptake into cytosol and nucleoli of all glycosylated CPDs, whereas the original CPDs and TEGylated CPDs showed much precipitation into fluorescent aggregates at these high concentrations. Flow cytometry analysis identified Glu‐CPDs as most active, closely followed by Gal‐CPDs and Tre‐CPDs, and all clearly more active than non‐glycosylated CPDs. In the MTT assay, all glyco‐CPDs were non‐toxic at concentrations as high as 2.5 μm . Consistent with thiol‐mediated uptake, glycosylated CPDs remained dependent on thiols on the cell surface for dynamic covalent exchange, their removal with Ellman's reagent DTNB efficiently inhibited uptake. Multifunctionality was demonstrated by inhibition of Glu‐CPDs with d ‐glucose (IC50 ca. 20 mm ). Insensitivity toward l ‐glucose and d ‐galactose and insensitivity of conventional CPDs toward d ‐glucose supported that glucose‐mediated uptake of the multifunctional Glu‐CPDs involves selective recognition by glucose receptors at the cell surface. Weaker but significant sensitivity of Gal‐CPDs toward d ‐galactose but not d ‐glucose was noted (IC50 ca. 110 mm ). Biotinylation of Glu‐CPDs resulted in the efficient delivery of streptavidin together with a fluorescent model substrate. Protein delivery with Glu‐CPDs was more efficient than with conventional CPDs and remained sensitive to DTNB and d ‐glucose, i.e., multifunctional. 相似文献
137.
《Journal of polymer science. Part A, Polymer chemistry》2018,56(18):2080-2095
A pH and reduction dual‐stimuli‐responsive PEGDA/PAMAM injectable network hydrogel containing “acetals” as pH‐sensitive groups and “disulfides” as reducible linkages was designed and synthesized via aza‐Michael addition reaction between PAMAM and PEGDA diacrylates. The pore size and swelling ratio of hydrogels was varied from 14 ± 3 to 19 ± 4 μm and 214 ± 13 to 300 ± 19 μm, respectively, with varying ethylene glycol repeating units in diacrylates. The swelling ratio of PEGDA/PAMAM network hydrogel increased with increase in the molecular weight of PEG and with decrease in pH. The presence of different cationizable amino‐functionalities in PEGDA/PAMAM network hydrogel helped to enhance the swelling ability of hydrogel under the acidic conditions. The continuous increase in metabolically active live HeLa cells with time in MTT assay implied biocompatibility/noncytotoxicity of the synthesized PEGDA/PAMAM injectable network hydrogel. Furthermore, the prepared PEGDA/PAMAM hydrogel showed higher degradation at lower pH and at higher concentration of DTT. The burst release of doxorubicin from PEGDA/PAMAM hydrogel under the environment of the lower pH and in presence of DTT compared to the release at normal physiological pH and in absence of DTT suggested the potential ability of this model hydrogel system for targeted and selective anticancer drug release at tumor tissues. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2080–2095 相似文献
138.
《Macromolecular bioscience》2018,18(7)
The cyclic brush polymers, due to the unique topological structure, have shown in the previous studies higher delivery efficacy than the bottlebrush analogues as carriers for drug and gene transfer. However, to the best of knowledge, the preparation of reduction‐sensitive cyclic brush polymers for drug delivery applications remains unexplored. For this purpose, a reduction‐sensitive amphiphilic cyclic brush copolymer, poly(2‐hydroxyethyl methacrylate‐g‐poly(ε‐caprolactone)‐disulfide link‐poly(oligoethyleneglycol methacrylate)) (P(HEMA‐g‐PCL‐SS‐POEGMA)) with reducible block junctions bridging the hydrophobic PCL middle layer and the hydrophilic POEGMA outer corona is designed and synthesized successfully in this study via a “grafting from” approach using sequential ring‐opening polymerization (ROP) and atom transfer free radical polymerization (ATRP) from a cyclic multimacroinitiator PHEMA. The resulting self‐assembled unimolecular core–shell–corona (CSC) micelles show sufficient salt stability and efficient destabilization in the intracellular reducing environment for a promoted drug release toward a greater therapeutic efficacy relative to the reduction‐insensitive analogues. The overall results demonstrate the reducible cyclic brush copolymers developed herein provides an elegant solution to the tradeoff between extracellular stability and intracellular high therapeutic efficacy toward efficient anticancer drug delivery. 相似文献
139.
《Macromolecular bioscience》2018,18(7)
In two ABA type amphiphilic block copolymers (P1, P2), the hydrophobic B block consists of a bioreducible segmented poly(disulfide) (PDS), while poly‐N‐isopropylacrylamide (PNIPAM) or poly(triethyleneglycol)methylether‐methacrylate (PTEGMA) serve as the hydrophilic A blocks in P1 and P2, respectively, leading to the formation of polymersome and micelle, owing to the difference in the packing parameters. Both exhibit comparable doxorubicin (Dox) encapsulation efficiency, but glutathione (GSH) triggered release appears much faster from the polymersome than micelle owing to the complete degradation of the PDS segment in polymersome morphology unlike in micelle. Dox‐loaded polymers (P1‐Dox and P2‐Dox) exhibit minimum toxicity to normal cells like C2C12. By contrast, P1‐Dox shows excellent killing efficiency to the HeLa cells (cancer cell) (in which the GSH concentration is significantly higher). However, P2‐Dox reveals a rather poor activity even to HeLa cells. Fluorescence microscopy studies show comparable cellular uptake of P1‐Dox and P2‐Dox. But the polymersome entrapped dye escapes fast from the cargo and reach the nucleus, while the drug‐loaded micelle remains trapped in the perinuclear zone explaining the significant difference in the drug delivery performance of polymersome and micelle. 相似文献
140.
Fragmentation of intra-peptide and inter-peptide disulfide bonds of proteolytic peptides by nanoESI collision-induced dissociation 总被引:1,自引:0,他引:1
Mormann M Eble J Schwöppe C Mesters RM Berdel WE Peter-Katalinić J Pohlentz G 《Analytical and bioanalytical chemistry》2008,392(5):831-838
Characterisation and identification of disulfide bridges is an important aspect of structural elucidation of proteins. Covalent
cysteine-cysteine contacts within the protein give rise to stabilisation of the native tertiary structure of the molecules.
Bottom-up identification and sequencing of proteins by mass spectrometry most frequently involves reductive cleavage and alkylation
of disulfide links followed by enzymatic digestion. However, when using this approach, information on cysteine-cysteine contacts
within the protein is lost. Mass spectrometric characterisation of peptides containing intra-chain disulfides is a challenging
analytical task, because peptide bonds within the disulfide loop are believed to be resistant to fragmentation. In this contribution
we show recent results on the fragmentation of intra and inter-peptide disulfide bonds of proteolytic peptides by nano electrospray
ionisation collision-induced dissociation (nanoESI CID). Disulfide bridge-containing peptides obtained from proteolytic digests
were submitted to low-energy nanoESI CID using a quadrupole time-of-flight (Q-TOF) instrument as a mass analyser. Fragmentation
of the gaseous peptide ions gave rise to a set of b and y-type fragment ions which enabled derivation of the sequence of the
amino acids located outside the disulfide loop. Surprisingly, careful examination of the fragment-ion spectra of peptide ions
comprising an intramolecular disulfide bridge revealed the presence of low-abundance fragment ions formed by the cleavage
of peptide bonds within the disulfide loop. These fragmentations are preceded by proton-induced asymmetric cleavage of the
disulfide bridge giving rise to a modified cysteine containing a disulfohydryl substituent and a dehydroalanine residue on
the C-S cleavage site. 相似文献