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91.
Stephanie Camerlynck 《European Polymer Journal》2006,42(12):3286-3293
Branched polystyrenes have been prepared rapidly (within 15 min) and in good yields (40-99%) in dichloromethane solution at 0 °C via cationic copolymerisation of styrene (St) with divinylbenzene (DVB) using SnCl4 as the initiator. All reaction components were deliberately used as supplied to evaluate whether such a simple approach could provide a facile synthesis of branched polymers and this has proved to be the case. The only additional experimental precaution was to avoid condensation of atmospheric moisture during the reactions. No additional chain regulating species was required to avoid crosslinking providing the St/DVB mole feed ratio was ?100/5. The intrinsic chain transfer to monomer reaction seems to be sufficient to reduce the length of the primary polymer chains and hence inhibit crosslinking and gelation in the case of the above mole feed ratios. The branching architecture of the products has been evaluated by 1H NMR and MALS-SEC analyses. 相似文献
92.
S. Lengvinaite M. Sangermano A. Priola S. Grigalevicius V. Getautis 《European Polymer Journal》2007,43(2):380-387
New carbazole monomers were synthesized and their cationic photopolymerization investigated. The monomers contain in each molecule two pendant carbazole groups and two functional groups reactive towards cationic photopolymerization. The investigated reactive groups were epoxy, oxetane or vinyl ether. Each type of monomer contains a spacer group namely ethylene oxide segment. The UV curing kinetics of the different monomers was monitored by real time FT-IR (RT-FTIR) analysis and the thermal properties evaluated by DSC. 相似文献
93.
Norris JL Hangauer MJ Porter NA Caprioli RM 《Journal of mass spectrometry : JMS》2005,40(10):1319-1326
Although cleavable detergents were first synthesized a number of years ago, they have only recently been successfully applied to problems involving biological molecules. Recent reports have demonstrated that these compounds are useful for applications involving both 2D PAGE and mass spectrometry. However, most cleavable surfactants have utilized acid-labile functional groups to affect cleavage. In applications where extreme pH is required, acid cleavable detergents have limited usefulness. We report the synthesis of fluoride cleavable silane compounds and photolabile cinnamate esters as cleavable detergents having alternative cleavage chemistries than previously reported cleavable detergents. These compounds were applied to whole cell analysis using MALDI mass spectrometry, and it was demonstrated that their use results in an increase in the number of proteins analyzed by increasing protein solubility. 相似文献
94.
Katarzyna Szymczyk 《Applied Surface Science》2010,256(24):7478-231
Contact angle measurements on poly(tetrafluoroethylene) (PTFE) surface were carried out for the systems containing ternary mixtures of cetyltrimethylammonium bromide (CTAB) and p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycols), Triton X-100 (TX100) and Triton X-165 (TX165). The aqueous solution of ternary surfactant mixtures were prepared by adding the third surfactant to the binary mixture of the surfactants where the synergetic effect in the reduction of the surface tension of water was determined, to compare the influence of the third surfactants on the values of surface tension of this binary mixture and the values of the contact angle on PTFE. The obtained results and calculations indicate that the ternary mixtures of CTAB + TX165 (αCTAB = 0.2, γLV = 60 and 50 mN/m) + TX100 (C = 10−8 to 10−2 M) have the biggest efficiency of the reduction of contact angle of water on PTFE in comparison to aqueous solutions of the single surfactants and their binary and ternary mixtures. Also in the case of all studied ternary mixtures of surfactants at concentrations of the bulk phase corresponding to unsaturated monolayer at water-air interface the adsorption of surfactants at PTFE-water interface is different than that at water-air interface, but is the same at concentrations near the critical micelle concentration (CMC). Thus the linear dependences between γLV cos θ − γLV and cos θ − 1/γLV, in the range of concentration studied for all systems confirm the same adsorption at two interfaces only at C near the CMC. 相似文献
95.
《Comptes Rendus Chimie》2019,22(5):355-362
In this study, the effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in hydrochloric acid (HCl) solution was investigated by using dodecyl trimethyl ammonium chloride (DTAC), tetradecyl trimethyl ammonium chloride (TTAC), cetyl trimethyl ammonium chloride (CTAC), and octadecyl trimethyl ammonium chloride (OTAC) as corrosion inhibitors to uncover their structure–efficiency relationships. The effect of the alkyl chain of quaternary ammonium cationic surfactants on corrosion inhibition in HCl solution was studied under different conditions, such as corrosion inhibitor concentration, temperature, and acidity, and this was done using the weightlessness method. The results obtained show that these inhibitors have high corrosion inhibition effect on A3 steel, and the corrosion inhibition efficiency is dependent on the length of the alkyl chain. At the same concentration, the longer the alkyl chain, the weaker the corrosion inhibition effect. When the temperature was 50 °C and the concentration of corrosion inhibitor was 70 mg/L, the corrosion inhibition efficiency order of the four cationic surfactants was DTAC > TTAC > CTAC > OTAC. Besides, the experimental results obtained show that the adsorption of the inhibitor on the A3 steel surface conforms to the Langmuir type isotherm, and then the corresponding adsorption thermodynamic parameters were obtained according to these parameters. It was observed that ΔH, ΔS, and Ea increased with increase in the length of the alkyl chain. The adsorption of the inhibitor on the steel surface is an exothermic, spontaneous, entropy process. 相似文献
96.
《Electrophoresis》2018,39(14):1794-1801
In our previous work, it was found that the vesicles were formed spontaneously by mixing octyltriethylammonium bromide (C8NE3Br) with sodium dodecyl benzene sulfonate (SDBS), and the vesicles have been developed as a pseudostationary phase (PSP) in EKC. In the present work, the effects of the concentration and the molar ratio of cationic to anionic surfactant on the vesicle properties and the performances of vesicle PSP in EKC have been investigated. The aggregates at all mixing ratio were negatively charged regardless of which surfactant surplus. As C8NE3Br proportion increased, the microviscosity of the vesicle became larger. With the increase in the total surfactant concentration, the migration time window broadened at the molar ratio of C8NE3Br to SDBS of 3:7. Unexpectedly, the window became narrowed at molar ratio of 5:5 and 6:4. However, the methylene selectivity of vesicle PSP at all above‐mentioned molar ratios enhanced as the total surfactant concentration increased, no matter whether the migration time window enlarged or narrowed. It implied that the vesicle PSP at molar ratio of 5:5 and 6:4 made it possible to obtain a better separation in a shorter time. When the total surfactant concentration was fixed at 20 mM, the methylene selectivity of the vesicle PSP of molar ratio of 5:5 was comparable to that of 3:7, but the migration time shortened by a half. 相似文献
97.
98.
A simple and sensitive method was developed for the rapid analysis of cationic dyestuffs from river and industrial wastewater using functionalized-multiwalled carbon nanotubes (f-MWCNT) with atmospheric pressure-matrix assisted laser desorption/ionization mass spectrometry (AP-MALDI/MS). The separation and preconcentration of analytes from sample solution was based on electrostatic force of attraction between positive dyestuffs and negatively charged f-MWCNT. The optimum enrichment of the three dyestuffs was observed at pH 5.0 for 3 min contact time and using 1 mg f-MWCNT in 1 mL water sample. The developed method has been successfully applied for the determination of three cationic dyestuffs namely neutral red (NR), brilliant cresyl blue (BB), and methylene blue (MB) in real world samples including river and industrial wastewater. The relative recoveries of dyestuffs from water sample were in the range 88.6-98.4%, indicating that the matrix had little effect on enrichment of analytes. The LOD and LOQ for cationic dyestuffs in water were 0.5-1.9 and 1.6-6.0 microg/L, respectively. All the results indicated that the proposed method could be used for the simultaneous determination of the three cationic dyestuffs in river and industrial wastewater at trace levels without the need of any chromatographic separation techniques. 相似文献
99.
Review of structural design guiding the development of lipid nanoparticles for nucleic acid delivery
Lipid nanoparticles (LNPs) are the most versatile and successful gene delivery systems, notably highlighted by their use in vaccines against COVID-19. LNPs have a well-defined core–shell structure, each region with its own distinctive compositions, suited for a wide range of in vivo delivery applications. Here, we discuss how a detailed knowledge of LNP structure can guide LNP formulation to improve the efficiency of delivery of their nucleic acid payload. Perspectives are detailed on how LNP structural design can guide more efficient nucleic acid transfection. Views on key physical characterization techniques needed for such developments are outlined including opinions on biophysical approaches both correlating structure with functionality in biological fluids and improving their ability to escape the endosome and deliver they payload. 相似文献
100.
Bang-Sen Wang Dr. Qi Zhang Dr. Zhi-Qiang Wang Chen-Yu Shi Prof. Xue-Qing Gong Prof. He Tian Prof. Da-Hui Qu 《Angewandte Chemie (International ed. in English)》2023,62(11):e202300984
Poly(1,2-dithiolane)s are a family of intrinsically recyclable polymers due to their dynamic covalent disulfide linkages. Despite the common use of thiolate-initiated anionic ring-opening polymerization (ROP) under basic condition, cationic ROP is still not exploited. Here we report that disulfide bond can act as a proton acceptor, being protonated by acids to form sulfonium cations, which can efficiently initiate the ROP of 1,2-dithiolanes and result in high-molecular-weight (over 1000 kDa) poly(disulfide)s. The reaction can be triggered by adding catalytic amounts of acids and non-coordinating anion salts, and completed in few minutes at room temperature. The acidic conditions allow the applicability for acidic monomers. Importantly, the reaction condition can be under open air without inert protection, enabling the nearly quantitative chemical recycling from bulk materials to original monomers. 相似文献