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171.
Even if the first protein therapeutics are now for more than 20 years on the market the selection of suitable adsorbents for the preparative downstream processing (DSP) of these biomolecules as well as the method development towards process conditions are still based mainly on 'trial and error'. Therefore, theses processes are not perfectly efficient, but indeed very time consuming and laborious. In this study a novel systematic method is introduced to find a suitable adsorbent (not necessarily the best one) with appropriate separation parameters for a specific separation with reduced effort. Following this strategy, the adsorbents must first be packed into columns under preparative conditions and then characterized completely with regard to, e.g. pressure drop, k'-values, plate heights (HETP curves), selectivity and capacity by using test substances, which are similar in their characteristics (molecular mass, size, charge distribution, hydrophobicity) to the target proteins. With the database once determined, a preselection of most suitable adsorbents including separation parameters is made regarding chromatographic and also economical properties. After this, preparative experiments must be conducted with a reduced number of adsorbents to figure out the individual influence of side components. This approach is demonstrated for the separation of an exemplary industrial protein mixture using cation-exchange chromatography (CEX). Characterization of different weak CEX-adsorbents is illustrated. After comparing these phases with each other, a first preselection and a prediction of suitable adsorbents is made. In the following preparative separation conditions (load, velocity, gradient) are determined for the preparative separations using the database and results of some additional experiments. The final comparison of separation performance in preparative scale confirms this selection and so the applicability of the new method. 相似文献
172.
The solid–liquid equilibria of the ternary system H2O–Fe(NO3)3–Co(NO3)2 were studied by using a synthetic method based on conductivity measurements.
Two isotherms were established at 0 and 15 °C, and the stable solid phases which appear are the iron nitrate nonahydrate (Fe(NO3)3·9H2O), the iron nitrate hexahydrate (Fe(NO3)3·6H2O), the cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and the cobalt nitrate trihydrate (Co(NO3)2·3H2O). 相似文献
173.
Biodegradable polyurethanes are an interesting alternative to many applications that involve plastics since they can minimize environmental problems caused by the low rates of natural degradation of synthetic polymers. In addition, since waterborne polyurethanes are based on aqueous dispersions, they restrict the use of organic solvents during processing and application of the polymer, thus contributing furthermore to reduce environmental damage. In this work, aqueous anionic polyurethane dispersions (PUD) with tailorable susceptibility for hydrolysis were synthesized by progressively replacing polypropylene glycol (PPG) with a biodegradable polycaprolactone diol (PCL) as soft segments. The hard segments were formed by extending isophorone diisocyanate (IPDI) with hydrazine (HZ). Dimethylol propionic acid (DMPA) was used as ionic center and triethyl amine (TEA) as neutralizer. The degree of phase separation was evaluated mainly by infrared spectroscopy (FTIR) and small angle X-ray scattering (SAXS). The results indicated that phase separation between hard and soft segments of poly(ester-urethane) is more significant than that of poly(ether-urethane). Data obtained from SAXS experiments indicated that phase separation within soft domains can also be present in samples containing both polyester and polyether soft segments. Hydrolytic degradation of the polymers in buffer solution of pH 7.4 and alkaline solution was performed as an initial test. The results showed that the fraction of polyester soft segments in the polyurethanes can be used to tailor the susceptibility of the materials to hydrolytic attack. Polyurethanes having higher contents of polyester were more promptly hydrolytically degraded than polyurethanes containing only polyether segments. 相似文献
174.
175.
LiMnC2O4(Ac) precursor in which Li+ and Mn2+ were amalgamated in one molecule was prepared by solid-state reaction at room-temperature using manganese acetate, lithium hydroxide and oxalic acid as raw materials. By thermo-decomposition of LiMnC2O4(Ac) at various temperatures, a series of Li1+y[Mn2−xLix]16dO4 spinels were prepared with Li2MnO3 as impurities. The structure and phase transition of these spinels were investigated by XRD, TG/DTA, average oxidation state of Mn and cyclic voltammeric techniques. Results revealed that the Li-Mn-O spinels with high Li/Mn ratio were unstable at high temperature, and the phase transition was associated with the transfer of Li+ from octahedral 16c sites to 16d sites. With the sintering temperature increasing from 450 to 850 °C, the phase structure varied from lithiated-spinel Li2Mn2O4 to Li4Mn5O12-like to LiMn2O4-like and finally to rock-salt LiMnO2-like. A way of determining x with average oxidation state of Mn and the content of Li2MnO3 was also demonstrated. 相似文献
176.
Wayne W. Barrett 《Journal of statistical physics》1977,16(4):371-394
A one-parameter family of partition functions is considered which for zero value of the parameter reduces to the spherical model of a ferromagnet. The model for > 0 is closer to the usual discrete lattice spin model of a ferromagnet than is the spherical model. The first four terms in of the limiting value of the partition function are calculated above and below the critical temperature for arbitrary interactions using the saddle point method to calculate certain correlation functions for the spherical model. These calculations indicate that the critical temperature is independent of for small and certain interactions.Part of this research appeared in the author's doctoral thesis.(3) 相似文献
177.
响应性凝胶及其在药物控释上的应用 总被引:19,自引:1,他引:19
综述近年来在响应性凝胶材料研究方面的进展,介绍了能感应pH、温度、光、电场以及生化物质等外界因素变化的响应性凝胶的结构特点与响应机理,同时介绍了此类凝胶应用于药物控制释放方面的研究近况。 相似文献
178.
Langmuir trough methods and fluorescence microscopy were combined to investigate the phase behavior and microstructure of monolayer shells coating micron-scale bubbles (microbubbles) typically used in biomedical applications. The monolayer shell consisted of a homologous series of saturated acyl chain phospholipids and an emulsifier containing a single hydrophobic stearate chain and polyethylene glycol (PEG) head group. PEG-emulsifier was fully miscible with expanded phase lipids and phase separated from condensed phase lipids. Phase coexistence was observed in the form of dark condensed phase lipid domains surrounded by a sea of bright, emulsifier-rich expanded phase. A rich assortment of condensed phase area fractions and domain morphologies, including networks and other novel structures, were observed in each batch of microbubbles. Network domains were reproduced in Langmuir monolayers under conditions of heating–cooling followed by compression–expansion, as well as in microbubble shells that underwent surface flow with slight compression. Domain size decreased with increased cooling rate through the phase transition temperature, and domain branching increased with lipid acyl chain length at high cooling rates. Squeeze-out of the emulsifier at a surface pressure near 35 mN/m was indicated by a plateau in Langmuir isotherms and directly visualized with fluorescence microscopy, although collapse of the solid lipid domains occurred at much higher surface pressures. Compression of the monolayer past the PEG-emulsifier squeeze-out surface pressure resulted in a dark shell composed entirely of lipid. Under certain conditions, the PEG-emulsifier was reincorporated upon subsequent expansion. Factors that affect shell formation and evolution, as well as implications for the rational design of microbubbles in medical applications, are discussed. 相似文献
179.
C12-2-En-C12•2Br与SDS混合水溶液的胶团化研究 总被引:5,自引:0,他引:5
与[C12H25N+(CH3)2CH2]2•2Br-(简记为C12-2-C12•2Br)/ C12H25SO4Na(SDS)混合水溶液相比,随着联接链上乙氧基团(E)数目增加,[C12H25N+(CH3)2]2C2H4(OC2H4)n•2Br-(简记为C12-2-En-C12•2Br, n=2,3)与SDS混合水溶液澄清区域明显增大. C12-2-E3-C12•2Br/SDS混合胶团化过程中二组分产生了协同效应,理论预测在澄清区域所能达到的最小临界胶团总浓度(cmcT,min)= 0.0339 mmol•L-1,对应的SDS在溶液体相中的摩尔分数(x2*)=0.447.当水溶液体相中SDS摩尔分数(x2)=0.5时,混合胶团总聚集数(NT)=36,混合胶团中SDS的摩尔分数(x2M)=0.43. 相似文献
180.
Multiblock poly(ester-block-amide)s (PEA) elastomers comprising hard blocks of oligoamide and oligoester soft segments were prepared and their structure-property relations were analysed. The polycondensation reaction of oligoesters (prepared from 1,4-butanediol and dimerized fatty acid) with oligolaurolactam (PA12) gave copolymer series with variable blocks content (the soft segments content was varied from 24 to 60 wt.%). PEAs are the phase system composed of crystallised sequences of oligoamide (hard segment phase) as well as oligoesters (soft segment phase). Mixing between the hard and soft phases was studied by thermal and mechanical measurements (DSC, DMTA). These results have indicated on a multiphase structure of investigated materials. The relationship between the observed thermal and tensile properties and the soft/hard segments content indicated on an increase of the phase separation with soft segments content. 相似文献