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排序方式: 共有920条查询结果,搜索用时 15 毫秒
911.
NianXiaohong GaoJintai 《高校应用数学学报(英文版)》1999,14(2):239-244
The robust stability for some types of tlme-varying interval raatrices and nonlineartime-varying interval matrices is considered and some sufficient conditions for robust stability of such interval matrices are given, The main results of this paper are only related to the verticesset of a interval matrices, and therefore, can be easily applied to test robust stability of interval matrices. Finally, some examples are given to illustrate the results. 相似文献
912.
《Journal of membrane science》1997,123(2):281-291
In this work, the role played by surfactants in the formation of PMMA membranes was investigated. For a wet inversion process with PMMA as polymer, acetone as solvent, and water as coagulant, delayed demixing was observed and the resulting membrane possessed a sponge-like structure. Adding 1.8 vol% of Tween 80 in the casting solution (PMMA + acetone) could shift the PMMA/acetone/water system from delayed demixing to instantaneous demixing and could induce macrovoids with small pin-holes on the membrane surface. It was found that the affinity of surfactant for coagulant is crucial for the enhancement of the formation of macrovoids. When water was the coagulant, adding the surfactants with high water solubility in PMMA/acetone solution can enhance the formation of macrovoids while adding the surfactants with low water solubility has no effect. On the other hand, for a lipophilic coagulant such as n-hexane, lipophilic surfactants were more effective in changing membrane structure than hydrophillic surfactants. In addition, a mechanism describing the role of surfactants in the formation of macrovoids is proposed: the addition of appropriate surfactants can enhance the affinity between solvent and coagulant, resulting in a shift from delayed demixing to instantaneous demixing, and macrovoids can then be induced. 相似文献
913.
914.
《中国化学快报》2023,34(6):107956
As an attractive C1 synthon, carbon dioxide (CO2) has been extensively used in organic synthesis to produce carboxylic acids. In this research, stereoselective electrochemical carboxylation of α,β-unsaturated sulfones has been developed under transition-metal-free conditions. All the cinnamic acids and the derivatives are obtained selectively in the E-configuration. Besides, arylpropiolates also can be produced from alkynyl sulfones. 相似文献
915.
Zishao Zhao Xuanyi Zhou Biao Zhang Fenfen Huang Yan Wang Zengsheng Ma Jun Liu 《Angewandte Chemie (International ed. in English)》2023,62(39):e202308738
Lithium fluoride (LiF) at the solid electrolyte interface (SEI) contributes to the stable operation of polymer-based solid-state lithium metal batteries. Currently, most of the methods for constructing lithium fluoride SEI are based on the design of polar groups of fillers. However, the mechanism behind how steric hindrance of fillers impacts LiF formation remains unclear. This study synthesizes three kinds of porous polyacetal amides (PAN-X, X=NH2, NH-CH3, N-(CH3)2) with varying steric hindrances by regulating the number of methyl substitutions of nitrogen atoms on the reaction monomer, which are incorporated into polymer composite solid electrolytes, to investigate the regulation mechanism of steric hindrance on the content of lithium fluoride in SEI. The results show that bis(trifluoromethanesulfonyl)imide (TFSI−) will compete for the charge without steric effect, while excessive steric hindrance hinders the interaction between TFSI− and polar groups, reducing charge acquisition. Only when one hydrogen atom on the amino group is replaced by a methyl group, steric hindrance from the methyl group prevents TFSI− from capturing charge in that direction, thereby facilitating the transfer of charge from the polar group to a separate TFSI− and promoting maximum LiF formation. This work provides a novel perspective on constructing LiF-rich SEI. 相似文献
916.
Lijun Zhou Chongyang Yang Dr. Xiaohui Yang Prof. Jie Zhang Cong Wang Wei Wang Mengyan Li Xiangchao Lu Dr. Ke Li Huiping Yang Han Zhou Prof. Jiajia Chen Prof. Dongping Zhan Prof. Vladimir I. Fal'ko Prof. Jun Cheng Prof. Zhongqun Tian Prof. Andre K. Geim Prof. Yang Cao Prof. Sheng Hu 《Angewandte Chemie (International ed. in English)》2023,62(52):e202314537
In nature and technologies, many chemical reactions occur at interfaces with dimensions approaching that of a single reacting species in nano- and angstrom-scale. Mechanisms governing reactions at this ultimately small spatial regime remain poorly explored because of challenges to controllably fabricate required devices and assess their performance in experiment. Here we report how efficiency of electrochemical reactions evolves for electrodes that range from just one atom in thickness to sizes comparable with and exceeding hydration diameters of reactant species. The electrodes are made by encapsulating graphene and its multilayers within insulating crystals so that only graphene edges remain exposed and partake in reactions. We find that limiting current densities characterizing electrochemical reactions exhibit a pronounced size effect if reactant's hydration diameter becomes commensurable with electrodes’ thickness. An unexpected blockade effect is further revealed from electrodes smaller than reactants, where incoming reactants are blocked by those adsorbed temporarily at the atomically narrow interfaces. The demonstrated angstrom-scale electrochemistry offers a venue for studies of interfacial behaviors at the true molecular scale. 相似文献
917.
Wang Zehua Jiang Wenjuan Zhao Yazi Hu Longzhou Wang Yan Ma Zengsheng 《Journal of Solid State Electrochemistry》2023,27(1):245-253
Journal of Solid State Electrochemistry - Solid-state lithium metal batteries are one of the most promising next-generation high-energy–density storage devices. However, the continuous growth... 相似文献
918.
Lifen Peng Zhiwen Yuan Zilong Tang Chunling Zeng Xinhua Xu 《Chemical record (New York, N.Y.)》2023,23(12):e202300242
Organic cycles play an important role in chemistry, pharmacology and material science for their unique properties. Construction of organic cycles from thioalkynes attracted increasing attention due to the facile access of thioalkynes. 2H-Azirines were synthesized successfully from thioalkynyl oxime ethers. Cyclobutanes were formed through chiral titanium catalyzed cycloaddition of thioalkynes. Cyclopentenes were afforded by annulation of thioalkynes. Thioalkynes could be also applied to synthesize thiophenes, oxazoles, benzo[b]thiophenes, 2H-chromenes, 2-phenylbenzothiazoles, diazacyclobutene, etc. In this review, construction of organic cycles from thioalkynes were highlighted. Firstly, the property and application of organic cyclic compounds were simply introduced. After presenting the general methods to access organic cycles, applications of thioalkynes as synthons to prepare organic cycles were classified and presented in detail. Based on different kinds of organic cycles obtained from thioalkynes, organic reactions for synthesis of three-, four-, five-, six-membered as well as fused cycles would be summarized and the plausible reaction mechanisms could be presented if available. 相似文献
919.
分别在673。873和1073K分解Mg/Al摩尔经继3的水滑石生成Mg(Al)O复合物,XRD测定均MgO物相,873K以上焙烧的样品同时存在MgAl2O4尖晶石物相,微量吸附量热测定其表面酸碱中心的强度和密度,发现碱中心强度和密度顺序为MAO-2〈MAO-3≈MAO-1,而酸中心强度和密度顺序是:MAO-1〉MAO-3≈MAO-2,红外光谱表明,Mg(Al)O复合物表面酸碱中心主要存在L酸,碱 相似文献
920.
《中国化学快报》2023,34(6):107984
Trifluoromethylation/sulfonylation of alkynes from trifluoromethyl thianthrenium triflate and sulfur dioxide under extremely mild reaction conditions provides a facile access to trifluoromethyl-substituted vinyl sulfonohydrazides in moderate to good yields. These trifluoromethyl-substituted vinyl sulfonohydrazides are further evaluated for anti-bacteria activity. 相似文献