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A simple method is presented for the one-pot synthesis of monodisperse MnO nanoparticles (NPs) using bulk MnO as the starting material. In the proposed approach, bulk MnO powder is dissolved in hot oleic acid to form manganese oleate (Mn(RCOO)2) and a decomposition process is then performed to obtain MnO NPs. The proposed method is environmentally friendly in that the only by-product is water, which can be easily distilled out. Conceptually, the synthesis method can be viewed as a controlled dissolution recrystallization process. It is shown that the size of the NPs can be controlled over the range of 6–32 nm via an appropriate specification of the precursor-to-oleic acid ratio and the reaction temperature (by the choice of an appropriate high b.p organic solvent). Finally, the size-dependent magnetic properties of three different monodisperse MnO NPs (7.7 nm, 19.4 nm and 31.7 nm) are studied. It is shown that the monodisperse MnO NPs exhibit a weak ferromagnetic behavior due to uncompensated surface spins at low temperatures. 相似文献
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Chia YC Chang FR Wang JC Wu CC Chiang MY Lan YH Chen KS Wu YC 《Molecules (Basel, Switzerland)》2008,13(1):122-128
Using a bioactivity-guided fractionation method, two coumarins: minumicroline acetonide (1) and epimurpaniculol senecioate (2), were isolated from the leaves of Murraya omphalocarpa Hayata (Rutaceae). Compound 1 had been previously synthesized and was now isolated from natural sources for the first time, and compound 2, possessing a negative optical rotation value, is new. The structures and their stereochemistry were fully elucidated on the basis of spectroscopic and X-ray crystallographic techniques. Both compounds 1 and 2 are active in the antiplatelet aggregation assay. Interestingly, the possible acetonide artifact 1 displayed significant antiplatelet aggregation induced not only by AA and collagen but also by platelet activating factor (PAF). 相似文献
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Hsu YH Chiang WH Chen MC Chern CS Chiu HC 《Langmuir : the ACS journal of surfaces and colloids》2006,22(16):6764-6770
The effects of SDS on the structural changes of the thermally induced polymeric micelles from a graft copolymer comprising poly(acrylic acid) (PAAc) as the backbone and poly(N-isopropylacrylamide) (PNIPAAm) and monomethoxy poly(ethylene glycol) (mPEG) as the grafts in aqueous solution are studied. At low temperature, SDS micelles form via the hydrophobic association of SDS molecules with the PNIPAAm grafts at a critical aggregation concentration of SDS (cac(SDS)) much lower than its critical micelle concentration. Consequently, the critical aggregation temperature of the graft copolymer is elevated. The corresponding structure of the thermally induced polymeric micelles is characterized by an abrupt reduction in the particle size and an increased tendency toward formation of the monocore structure with a more compact and hydrophobic PNIPAAm microdomain being developed. On the other hand, upon the polymeric micelle formation at high temperature, the copolymer-bound SDS micelle structure is disrupted and the dissociated SDS molecules migrate to the core-shell interface with their alkyl chains residing in the liquidlike region of the hydrophobic PNIPAAm microdomain. The correlation between the polymeric particles and copolymer-bound micelles is further substantiated by showing the change of the colloidal particle size in response to changes in cac(SDS) via adjusting the pH of the aqueous copolymer/SDS solutions. 相似文献
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Chunlan Song Xin Dong Zhongjie Wang Kun Liu Chien‐Wei Chiang Aiwen Lei 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(35):12334-12338
The [4+2] annulation represents an elegant and versatile synthetic protocol for the construction of benzene rings. Herein, a strategy for visible‐light induced [4+2] annulation of thiophenes and alkynes, to afford benzene rings, is presented. Under simple and mild reaction conditions, the ready availability and structural diversity of thiophenes and alkynes permit the facile synthesis of several substituted aromatic rings. Valuable drugs and amino acids are also well tolerated. Moreover, DFT calculations explain the high regioselectivity of the reaction. 相似文献
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Gemini表面活性剂是通过联接基团将两个具有亲水亲油性质的两亲结构单元在其亲水头基上或靠近亲水头基处以共价键方式连接而成的一类表面活性剂。这类表面活性剂由于联接基团的引入具有比传统单链表面活性剂更高的表面活性,同时分子结构中更多的可调控因素使其在水溶液中表现出更为丰富的自聚集行为,而且分子不同部位结构的改变对分子内或分子间相互作用产生不同的影响,可实现通过分子结构的设计有效调控其自聚集能力和聚集体结构。本综述将从联接基团、烷基链、亲水头基、反离子和其它功能性基团这五个方面概述近些年Gemini表面活性剂水溶液中聚集行为方面的研究进展,总结人们对Gemini表面活性剂分子间相互作用规律的认识,期望对于进一步发展这类高效的表面活性剂体系提供有益的帮助。 相似文献
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Efrem Braun Dr. Joseph J. Chen Dr. Sondre K. Schnell Dr. Li‐Chiang Lin Dr. Jeffrey A. Reimer Dr. Berend Smit 《Angewandte Chemie (International ed. in English)》2015,54(48):14349-14352
Molecular simulations and NMR relaxometry experiments demonstrate that pure benzene or xylene confined in isoreticular metal–organic frameworks (IRMOFs) exhibit true vapor–liquid phase equilibria where the effective critical point may be reduced by tuning the structure of the MOF. Our results are consistent with vapor and liquid phases extending over many MOF unit cells. These results are counterintuitive since the MOF pore diameters are approximately the same length scale as the adsorbate molecules. As applications of these materials in catalysis, separations, and gas storage rely on the ability to tune the properties of adsorbed molecules, we anticipate that the ability to systematically control the critical point, thereby preparing spatially inhomogeneous local adsorbate densities, could add a new design tool for MOF applications. 相似文献