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81.
The desired performance characteristics of absorbent products such as diapers include a low number of leaks, adequate liquid absorption capacity, and high skin dryness. By measuring the absorption behavior of mixtures of cellulose fluff pulp and superabsorbent polymers in nonimmersed conditions, we identify four major parameters that affect the swelling of the polymer in a composite: the Donnan ion‐exclusion effects of limiting the amount of liquid in contact with the superabsorbent polymer, the restriction of swelling by the physical constraints of the fibrous network that surrounds the polymer particles, the restriction of swelling by the capillary tension provided by the pores between the cellulose fibers, and the osmotic pressure of extracted polyelectrolytes. Swelling of the superabsorbent polymer in composites is always smaller than the value measured by immersion of the polymer followed by centrifugation. Donnan exclusion of ions from the gel phase results in about 16% less swelling than when the polymers are swollen in excess liquid. The swelling restriction imposed by the fiber network, which surrounds the granules, reduces swelling a further 10%. In addition, the presence of small pores between the fibers exerts capillary tension on the polymer and lowers the swelling by another 10%. The external compression of the composite pads does not reduce the extent of swelling of the superabsorbent polymer because the stress is supported by the fibers. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2493–2507, 2005 相似文献
82.
William A. Boyle Richard F. Buchholz John A. Neal Joseph L. McCarthy 《应用聚合物科学杂志》1991,42(7):1969-1977
Flow injection analysis, often used for determination of diffusion coefficients of nonpolymeric substances, has now been applied to the characterization of pauci- and polydisperse polymers in solution. A relative method was found useful for obtaining moderate quality evaluations of diffusion coefficients and related parameters of polymers. The width at half-height W1/2 of the trace peak is found to be proportional to the number average molecular weight M?n of pauci- and polydisperse polymers, allowing estimation of M?r and diffusion coefficients. For sodium polystyrene sulfonates at substantially infinite dilution in 1.0 g L?1 Na2SO4, a linear relation has been observed between the logarithms of the molecular weight M?n and the mean diffusion coefficient D in the M?n range of 1000–90,000 g mol?1 or the D range of 30 × 10?7 to 2 × 10?7 cm2 s?1. 相似文献
83.
Frederico Buchholz Maciel Yoshikazu Miyanaga Koji Tochinai 《The Journal of VLSI Signal Processing》1993,5(2-3):273-282
The throughput of a parallel execution of a DSP algorithm is limited by the iteration bound, which is the minimum period between the starts of consecutive iterations. It is given byT
i=max (T
i/D
i), whereT
i andD
i are the total time of operations and the number of delays in loopi, respectively. The execution throughput of a DSP algorithm can be increased by reducing theT
is, and this reduction can be realized by taking as many operations as possible out of loops without changing the semantic of the calculation. Since many DSP algorithms extensively use the four basic arithmetic operations, a simple and effective way of doing this reduction is to apply commutativity, associativity and distributivity on these operations. This paper presents an optimization technique, calledLoop Shrinking, which reduces the iteration bound by using the above method. Loop Shrinking is based on a heuristic method which is time-efficient for simple cases but can also tackle complex examples. An implementation of Loop Shrinking is presented in this article. The results show that it can yield a reduction in the iteration bound near or equal to careful hand-tuning. 相似文献
84.
Adolescent mothers are typically depicted as inadequate parents. Their children are thought to be at significant risk for maltreatment. A review of the literature, however, reveals that a confluence of factors other than maternal age are implicated. Many studies make comparisons between teenage and older mothers without identifying the sample's socioeconomic group. The degree of risk to children of adolescent parents may well be determined by the financial, social, and emotional stresses these families face, with availability of resources which offer support and encouragement perhaps being the critical factor. The technique of "mapping" might be used to isolate these correlates. The authors suggest a reformulation of the question of adolescent parental ability, focusing on conditions under which adolescent parents may be at greater or lesser risk of maltreating their children. This approach could ultimately prove conducive to planning and implementing effective intervention programs. 相似文献
85.
86.
T. Rudolph P. Bühle J. Beck F. Pflücker K.-A. Reiffen H. Buchholz 《International journal of cosmetic science》2007,29(1):64-65
Ideally, anti-(photo)ageing concepts should provide maximum efficacy, perfect stability and cosmetic (formulation) elegance. The need for high efficacy paired with excellent stability appeared contradictive but was resolved by designing complete redox systems rather than antioxidants alone. We here introduce a new class of cosmetic redox pairs, each comprising the initial antioxidant plus its oxidation product. The chemical properties of the oxidation product are the key to enabling the system to maintain or even increase its initial efficacy. A series of antioxidant tests were used to carefully characterize single redox pair components for comparison with traditional antioxidants such as vitamin C and E derivatives (DPPH, lipid and TEAC assays). Kinetic studies on the photobehaviour of a selected redox pair were carried out in cosmetic emulsions with solar simulation and monitored by UV spectroscopy and high performance liquid chromatography. Hydroxy dimethoxybenzyl malonate (HDBM) is a pure transparent cosmetic oil. It shows excellent cosmetic stability coupled with extraordinary antioxidant properties. This controlled activity can be explained well by the presence of its oxidation product hydroxy dimethoxybenzylidene malonate (HDBM ox ), which provides ongoing antioxidant activity plus excellent UVA absorbing properties. The redox pair described here provides the advanced on-demand benefit of a non-UV-absorbing photoprotector that is converted into its UV-absorbing equivalent upon light exposure. 相似文献
87.
Maximilian Clausing Doreen William Matthias Preussler Julia Biedermann Konrad Grützmann Susan Richter Frank Buchholz Achim Temme Evelin Schrck Barbara Klink 《International journal of molecular sciences》2022,23(10)
The IDH1R132H mutation in glioma results in the neoenzymatic function of IDH1, leading to the production of the oncometabolite 2-hydroxyglutarate (2-HG), alterations in energy metabolism and changes in the cellular redox household. Although shifts in the redox ratio NADPH/NADP+ were described, the consequences for the NAD+ synthesis pathways and potential therapeutic interventions were largely unexplored. Here, we describe the effects of heterozygous IDH1R132H on the redox system in a CRISPR/Cas edited glioblastoma model and compare them with IDH1 wild-type (IDH1wt) cells. Besides an increase in 2-HG and decrease in NADPH, we observed an increase in NAD+ in IDH1R132H glioblastoma cells. RT-qPCR analysis revealed the upregulation of the expression of the NAD+ synthesis enzyme nicotinamide phosphoribosyltransferase (NAMPT). Knockdown of NAMPT resulted in significantly reduced viability in IDH1R132H glioblastoma cells. Given this dependence of IDH1R132H cells on NAMPT expression, we explored the effects of the NAMPT inhibitors FK866, GMX1778 and GNE-617. Surprisingly, these agents were equally cytotoxic to IDH1R132H and IDH1wt cells. Altogether, our results indicate that targeting the NAD+ synthesis pathway is a promising therapeutic strategy in IDH mutant gliomas; however, the agent should be carefully considered since three small-molecule inhibitors of NAMPT tested in this study were not suitable for this purpose. 相似文献
88.
Patrick C. F. Buchholz Dr. Constantin Vogel Waldemar Reusch Prof. Dr. Martina Pohl Prof. Dr. Dörte Rother Prof. Dr.‐Ing. Antje C. Spieß Prof. Dr. Jürgen Pleiss 《Chembiochem : a European journal of chemical biology》2016,17(21):2093-2098
The development of novel enzymes for biocatalytic processes requires knowledge on substrate profile and selectivity; this can be derived from databases and from publications. Often, these sources lack time‐course data for the substrate or product, and an unambiguous link between experiment and enzyme sequence. The lack of integrated, original data hampers the comprehensive analysis of enzyme kinetics and the evaluation of sequence–function relationships. In order to accelerate enzyme engineering, BioCatNet integrates protein sequence, protein structure, and experimental data for a given enzyme family. BioCatNet explicitly assigns the enzyme sequence to the experimental data, which consists of information on reaction conditions and time‐course data. BioCatNet facilitates the consistent documentation of reaction conditions, the archiving of time‐course data, and the efficient exchange of experimental data among collaborators. Data integration is demonstrated for three case studies by using the TEED (Thiamine diphosphate‐dependent Enzymes Engineering Database). 相似文献
89.
Mean relative gas hold up, slip velocity, bubble size distribution, and volumetric mass transfer coefficient of oxygen were measured in sparged columns of highly viscous non-Newtonian fluids (CMC solutions) as a function of the gas flow rate, and CMC concentration (fluid consistency index k, and flow behaviour index n).By comparison of the measured bubble swarm velocities with those calculated by relations for single bubbles the bubble swarm behaviour was investigated. It could be shown that small bubbles in swarm have higher rising velocities than single bubbles, expecially in highly viscous media. Large single bubbles rise with high velocity due to the change of their shape caused by the swarm of the smaller bubbles. No large bubbles with spherical cap shape could be observed. The volumetric mass transfer coefficient decreases rapidly with increasing CMC-concentration.A comparison of the volumetric mass transfer coefficients with those measured in mechanically agitated vessels indicates, that the performance of sparged columns is comparable with the one of agitated vessels. Because of their lower energy requirement sparged columns are more economical than mechanically agitated vessels. It is possible to improve the performance of sparged columns by the redispersion of large bubbles in a multistage equipment. 相似文献
90.
Reachability analysis is the most general approach to the analysis of Petri nets. Due to the well-known problem of state-space explosion, generation of the reachability set and reachability graph with the known approaches often becomes intractable even for moderately sized nets. This paper presents a new method to generate and represent the reachability set and reachability graph of large Petri nets in a compositional and hierarchical way. The representation is related to previously known Kronecker-based representations, and contains the complete information about reachable markings and possible transitions. Consequently, all properties that it is possible for the reachability graph to decide can be decided using the Kronecker representation. The central idea of the new technique is a divide and conquer approach. Based on net-level results, nets are decomposed, and reachability graphs for parts are generated and combined. The whole approach can be realized in a completely automated way and has been integrated in a Petri net-based analysis tool. 相似文献