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991.
992.
Sequential addition of L-lactide(LA) followed by ε-caprolactone(CL), and simultaneous addition of both monomers, afforded random LA/CL copolymers in the presence of lanthanide aryloxides under mild conditions. Transesterification was proved to play a predominant role in random copolymer formation. Moreover, treatment of poly(L-lactide) with ε-CL led to random copolymer formation, which provides a new strategy not only to prepare random LA/CL copolymers, but also to directly modify PLLA. 相似文献
993.
Rational Fabrication of Anti‐Freezing,Non‐Drying Tough Organohydrogels by One‐Pot Solvent Displacement
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Fan Chen Dan Zhou Jiahui Wang Tianzhen Li Prof. Dr. Xiaohu Zhou Dr. Tiansheng Gan Dr. Stephan Handschuh‐Wang Prof. Dr. Xuechang Zhou 《Angewandte Chemie (International ed. in English)》2018,57(22):6568-6571
Tough hydrogels, polymeric network structures with excellent mechanical properties (such as high stretchability and toughness), are emerging soft materials. Despite their remarkably mechanical features, tough hydrogels exhibit two flaws (freezing around the icing temperatures of water and drying under arid conditions). Inspired by cryoprotectants (CPAs) used in the inhibition of the icing of water in biological samples, a versatile and straightforward method is reported to fabricate extreme anti‐freezing, non‐drying CPA‐based organohydrogels with long‐term stability by partially displacing water molecules within the pre‐fabricated hydrogels. CPA‐based Ca‐alginate/polyacrylamide (PAAm) tough hydrogels were successfully fabricated with glycerol, glycol, and sorbitol. The CPA‐based organohydrogels remain unfrozen and mechanically flexible even up to ?70 °C and are stable under ambient conditions or even vacuum. 相似文献
994.
Shun-ping Shi Xiao-feng Zhao Xiao-yu Liu Dan Lei Min Yan Gang Jiang 《Journal of Cluster Science》2018,29(5):909-919
The neutral, anionic, and cationic SnnTi(0, ±1) (n?=?1–10) units are researched computationally using a density functional theory. The optimized geometries of SnnTi(0, ±1) clusters illustrate that the most stable structures between the neutral, anionic, and cationic clusters keep the similar structures when n?=?1, 2, 4, 5, 9,10, however, we find that the obtained most stable clusters of the size n?=?3, 6, 7, 8 are different. From the optimized results a systematic analysis is carried out to obtain the relative stabilities, electronic properties, and natural population analysis of SnnTi(0, ±1) clusters. The relative stabilities are investigated by analyzing the binding energies, fragmentation energies, and the second order energies difference of SnnTi(0, ±1) clusters, the results show that the binding energies of anionic clusters are obviously larger than those of neutral and cationic clusters. The HOMO–LUMO gap, the adiabatic electron affinity, vertical electron detachment energy, adiabatic ionization potential energy, and vertical ionization potential energy respond the electronic property, we obtain that the Ti atom changes the electron structures of stannum clusters. To discuss reliable charge transfer information from SnnTi clusters to SnnTi? clusters and SnnTi+ clusters, the natural population analysis of neutral, anionic, and cationic SnnTi(0,±1) clusters are calculated. 相似文献
995.
Xinhua Cao Aiping Gao Dan Liu Na Zhao Qianqian Ding Yiran Li 《Supramolecular chemistry》2018,30(8):674-680
A new gelator 1 containing triphenylamine was designed and synthesized, and formed stable gel in ethyl acetate. The self-assembly process of molecule 1 was thoroughly investigated. The solid microsphere structure formed in gel 1 could be turned into nanotube in the transition process of gel to gel via sonication. At the same time, the intermolecular hydrogen bond of self-assembly system was obviously enhanced under sonication. The XRD and water contact angle experiments results of xerogel 1 before and after sonication showed great difference. The hydrophobicity of xerogel 1 film was obviously decreased with the change of contact angle from 142° to 129° after sonication at 100 W for one minute. From the results, it was possible that the solid microsphere was re-dissolved and further reassembled into nanotube. To our knowledge, it was the first example that the solid sphere structure was changed into nanotube in self-assembly system via sonication. 相似文献
996.
Wen-ting Li Dan Luo Jia-ning Huang Lin-lin Wang Feng-guo Zhang Tao Xi 《Natural product research》2018,32(6):662-667
One new alkaloid, named as acremolin C (1), was isolated from static culture of Antarctic fungus, Aspergillus sydowii SP-1, in an investigation of the antimicrobial constituents of this Antarctic microorganism, and its structure was determined by spectroscopic methods. Additionally, four known compounds, cyclo-(L-Trp-L-Phe) (2), 4-hydroxyphenylacetic acid (3), (7S)-(+)-hydroxysydonic acid (4) and (7S, 11S)-(+)-12-hydroxysydonic acid (5), were isolated and identified. Biological studies disclosed that compounds 2, 4 and 5 showed moderate inhibitions against methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE) as comparing to tigecycline, while compound 1 displayed weak inhibition activities against MRSA and MRSE. 相似文献
997.
The first-ever Diels-Alder reactions of 3-alkenyl indoles with a conjugated alkynyl ketone are reported. These reactions proceed in an atom-economic manner without a catalyst and give various substituted 1-acetyl carbazoles in moderate to excellent yields. These products can be converted to 1-hydroxyl carbazoles in high yields under mild reaction conditions. 相似文献
998.
In this paper we introduce Peano path derivatives as a natural extension of the notion of path derivatives. We give a sufficient condition on a system of paths to ensure the corresponding Peano path derivative is Baire 1. As consequences, we obtain that unilateral approximate and unilateral -approximate Peano derivatives are Baire one.
999.
I. W. Ellms S. I. Hauser L. W. Winkler H. Pecker V. Froboese A. T. Stuart F. Malméjac J. Tillmans O. Heublein H. Noll J. M. Kolthoff H. Klut Dietl L. Dede E. Hauser E. M. Chamot D. S. Pratt A. E. Johnson H. Silvester W. Vaubel G. Denigès E. H. Miller S. Rothenfusser M. Bornand L. Rosenthaler V. Jahn A. Dané L. v. Liebermann D. Acel E. B. Phelps H. L. Shoub Escaich H. Berger G. D. Elsdon N. Evers H. W. Brubaker F. W. Bruckmiller 《Analytical and bioanalytical chemistry》1922,61(4-5):196-205
1000.
This article deals with the solution properties of poly(vinylpyrrolidone) (PVP) in salt and surfactant environment. The cloud point (CP) of PVP has been found to be induced by the salts NaCl, KCl, KBr, Na2SO4, MgSO4, and Na3PO4. On the basis of CP values for a salt at different [PVP], the energetics of the clouding process have been estimated. The effect of the surfactant, sodium dodecyl sulfate (SDS), on the salt-induced CP has also been studied, and reduction in CP at low [SDS] and increase in CP at high [SDS] have been observed. The water vapor adsorption of PVP has been determined by isopiestic method. The results display a BET Type III isotherm whose analysis has helped to obtain the monolayer capacity of PVP and formation of multilayer on it. The solvation of PVP in a solution of water and a water-isopropanol mixture has been determined by conductometry from which contribution of the individual components were estimated. The interaction of PVP with SDS in solution led to formation of a complex entity, which has been studied also by conductometry adopting a binding-equilibrium scheme. SDS has been found to undergo two types of binding as monomers in the pre- critical aggregation concentration (CAC) range and as small clusters in the post CAC region. The stoichiometries of binding and binding constant were evaluated. 相似文献