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排序方式: 共有106条查询结果,搜索用时 31 毫秒
81.
针对普通冷库冷藏系统存在排气温度过高、制冷性能较低等问题,研发了一套采用微通道换热器的变频转子压缩机新型冷藏系统,研究系统在不同压缩机转速情况下、采用不同补气形式对系统制冷性能的影响。结果表明:库外温度为32℃时,压缩机转速从3 000 r/min提升至5 000 r/min过程中,分别与不补气系统对比,低压补气系统时排气温度降低了20.54%~22.61%、压缩机功率提高了0.28%~9.19%、制冷量增加了1.15%~4.52%、COP增加了1.41%~3.43%;中压补气系统排气温度降低了18%~20.42%、压缩机功率提高了8.38%~17.29%、制冷量增加了7.86%~18.48%、COP增加了5.08%~8.97%。 相似文献
82.
Reversible boronate-catechol linkage was widely used to construct two-dimensional coatings and threedimensional nanostructures or hydrogels.The construction of these functional materials usually requires the pre-synthesis of macro molecular building blocks,and direct gelation between natural polyphenols and small molecule boranic acids is yet to be investigated.In this study,we fabricated a family of allsmall-molecule dynamic covalent gels consisting of tannic acid and boronic acids.Transparent and thixotropic gels were formed by boronate affinity towards catechol groups abundant on natural polyphenols.The gels showed multi-responsiveness,such as acid-,base-,reduction-and oxidantsensitive depending on the used boronic acid building blocks.The chemistry for gel formation and stimuli-responsiveness was characterized by11B NMR spectroscopy.The multi-stimuli responsiveness,green processing and facile modular design make the boronic acid-tannic acid gels promising candidates for the development of smart soft materials. 相似文献
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84.
本文用Lyapunov函数技巧对非线性无界延迟随机微分方程建立整体解的存在唯一性定理.利用半鞅收敛定理,研究零解的一般衰减速度的随机稳定性并给出判定定理. 相似文献
85.
Ying Zhang Lei Wang Xuejing Wang Guodong Qi Prof. Xiaojun Han 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(27):9059-9063
A novel method of forming lipid bilayer membrane arrays on micropatterned polyelectrolyte film surfaces is introduced. Polyelectrolyte films were fabricated by the layer‐by‐layer technique on a silicon oxide surface modified with a 3‐aminopropyltriethoxysilane (APTES) monolayer. The surface pKa value of the APTES monolayer was determined by cyclic voltammetry to be approximately 5.61, on the basis of which a pH value of 2.0 was chosen for layer‐by‐layer assembly. Micropatterned polyelectrolyte films were obtained by deep‐UV (254 nm) photolysis though a mask. Absorbed fluorescent latex beads were used to visualize the patterned surfaces. Lipid bilayer arrays were fabricated on the micropatterned surfaces by immersing the patterned substrates into a solution containing egg phosphatidylcholine vesicles. Fluorescence recovery after photobleaching studies yielded a lateral diffusion coefficient for probe molecules of 1.31±0.17 μm2 s?1 in the bilayer region, and migration of the lipid NBD PE in bilayer lipid membrane arrays was observed in an electric field. 相似文献
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Chemistry and Chemical Engineer School, Henan Institute of Science and Technology, Xinxiang, Henan 453003, China 相似文献
88.
Xiaoyan Wang Jin Li Xuejing Yang Xiu‐mei Gao Hui Wang Yan‐xu Chang 《Journal of separation science》2019,42(14):2426-2434
An industrial MCM‐41‐miniaturized matrix solid‐phase dispersion extraction coupled with response surface methodology was explored to determine L‐epicatechin, typhaneoside, isorhamnetin‐3‐O‐neohespeidoside, naringenin, kaempferol, and isorhamnetin in Pollen typhae by ultra‐high performance liquid chromatography connected to a photodiode array detection. Several variables were optimized in detail, including mesh number of sieve, type of adsorbent, mass ratio of sample to adsorbent, grinding time, methanol concentration, and elution volume. Central composite design was applied to optimize the best conditions for the maximum yields of the total flavonoids. The results displayed a good linear relationship (R > 0.9992) and the recoveries ranged from 92.9 to 103% (RSD < 4.53%) of the six flavonoids. The optimal method with high efficiency and low consumption was obviously better than heating reflux and ultrasonic extraction. It was proven that the developed industrial MCM‐41‐miniaturized matrix solid‐phase dispersion extraction coupled with simple ultra‐high performance liquid chromatography method could be a rapid and efficient tool for extraction and determination of flavonoids in natural products. 相似文献
89.
为了鉴别分析催化裂化待生剂上分子筛孔道内、外的有机吸附物种,提出了超声萃取提取待生剂上外表面的有机吸附物种方法,优化了萃取条件;对分子筛孔道内的有机吸附物种。采用HF处理待生剂,溶解催化剂分子筛骨架以释放孔内积炭,并用二氯甲烷作溶剂萃取。采用GC-MS分离并鉴别分子筛孔道内、外的有机吸附物种,实验结果显示:在催化剂外表面主要是二环和三环芳烃,而在分子筛孔道内解吸的则是从双环到七元环的多环芳烃。这些结果对研究催化裂化催化剂的性能和结炭的机理提供了重要信息。 相似文献
90.