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991.
Experimental behaviour of a full-scale timber-concrete composite floor with mechanical connectors 总被引:1,自引:1,他引:0
Massimo Fragiacomo 《Materials and Structures》2012,45(11):1717-1735
The timber-concrete composite (TCC) beam is a construction technique that can be used for upgrading of existing timber floors without the need of demolition. This possibility has been investigated through full-scale tests on a 6-storey experimental building with light-frame timber walls and platform construction, where the existing timber floor for domestic use was upgraded for reuse as an office building. The acoustic flooring was replaced with a 60?mm lightweight concrete slab, connected to the existing joists with inclined shear connectors (SFS screws) to form the TCC floor. The floor and environmental conditions were monitored during the concrete pouring and hardening, and during the application of the live load. Two different types of construction, propped and unpropped, were compared, and an extensive experimental investigation was performed on material components (lightweight concrete, timber, and connection system) with the aim to fully characterise the behaviour under short- and long-term loading. The unpropped floor was then tested to failure under monotonic loading, and two different boundary conditions, namely the actual joist-to-wall joint and a perfectly pinned support, were investigated. An advanced FE model was validated on the test results and used to predict the deflection in the long-term. The composite floor achieved the target stiffness and the design load for satisfying ultimate and serviceability limit states for office loading in the UK. The actual joist-to-wall restraint was characterized by a low degree of fixity, however it produced early longitudinal crack formation in the proximity of the support. The final collapse of the floor as a whole occurred progressively under increasing load after failure for fracture in tension of an individual joist. The higher drying shrinkage of lightweight concrete raised the deflection during concrete curing and hardening. 相似文献
992.
“(今天)我们被限定的居住空间,与祖先生活在岩洞中或屋檐下、围着篝火的空间截然不同,后者的许多独特品质是建筑无法替代的,其中首要的就是自由与变化。”——雷纳·班纳姆,《家不是一座房子》,1965年 相似文献
993.
994.
Hydrogen desorption from hydride matrix is still an open field of research. Extensive, density functional theory based, ab-initio molecular dynamics simulations of MgH2–Mg interface catches the atomic level structural mechanism leading to hydrogen desorption. The numerical model estimates the desorption temperature for an interface with Fe catalyst in excellent agreement with experimental results. Formation energies and the analysis of the structural data reveal the role played by the catalysts to lower the desorption temperature. 相似文献
995.
Massimo Boninsegni 《Journal of Low Temperature Physics》2011,165(3-4):67-77
Extensive Monte Carlo simulations of 4He monolayer films adsorbed on weak substrates have been carried out, aimed at ascertaining the possible occurrence of a quasi-two-dimensional supersolid phase. Only crystalline films not registered with underlying substrates are considered. Numerical results yield strong evidence that 4He will not form a supersolid film on any substrate strong enough to stabilize a crystalline layer. On weaker substrates, continuous growth of a liquid film takes place. 相似文献
996.
Chemical and physical properties of polymeric species in solution strongly depend on their structure, which can be modulated by covalently linking substituents of different solubility. In this work, the effect of changing the interaction strength and fractional loading of hydrophobic substituents on semi-flexible hydrophilic polymers of varying chain length is studied by means of Monte Carlo simulations and coarse grained model potentials. The latter are chosen in order to provide a more factual representation of a chain in diluted solution, introducing substituent flexibility and realistic torsional and bending potentials. Upon increasing the number and the interaction strength of the substituents, our results indicate a less steep rise of the chain gyration radius and “end to end” distance for the chain length than predicted for an unsubstituted polymer in an almost good solvent. Moreover, a “disordered to compact” structural transition appears. In parallel, the formation of hydrophobic nuclei and the consequent appearance of flexible polymer loops grafted to the semi-rigid cores is witnessed. The core formation resembles a nucleation phenomenon, where the change in the interaction between the substituents modulates the free energy surface for the aggregation process similarly to the change in chemical potential. Interestingly, it has been found that a single chain containing a sufficiently high number of interacting substituents may give rise to the formation of multiple cores, suggesting that the chain stiffness may play a role in defining the structure of the free energy minimum. 相似文献
997.
Pierluigi Magagnini Maria S. Tonti Marco Masseti Massimo Paci Lilia I. Minkova Tsenka T. Miteva 《Polymer Engineering and Science》1998,38(9):1572-1586
Poly(ethylene terephthalate) (PET) was melt blended with several liquid-crystalline polymers (LCPs), both with and without Ti(OBu)4 catalyst. The LCPs, referred to as VA, LC5, LC3, and SBH, respectively, were Vectra-A950, Rodrun LC-5000, Rodrun LC-3000, and a laboratory copolyester of sebacic acid (S), 4,4′-diacetoxybiphenyl (B), and 4-acetoxybenzoic acid (H). Their degree of aromaticity decreases in that order. The phase behavior and the morphology of the blends were studied by differential scanning calorimetry and scanning electron microscopy. All the LCPs retard the dynamic crystallization of PET. The lower the LCPs degree of aromaticity, the more pronounced was the effect. It was not possible to obtain any evidence of ester exchange reactions by the reactive blending of PET with VA. On the contrary, appreciable changes of phase behavior and morphology were observed under comparable conditions for the other blends. With LC5 and LC3, the transesterification process predominantly involved the ET-rich phase of those polymers. Extensive transesterification occurred between PET and SBH, as proven by the gradual formation of a quasi homogeneous material, with lowered temperatures and enthalpies of fusion and crystallization. For blends with more than 25% SBH, homogenization is followed by the segregation of a new, highly aromatic phase. 相似文献
998.
Luana Palazzi Benedetta Fongaro Manuela Leri Laura Acquasaliente Massimo Stefani Monica Bucciantini Patrizia Polverino de Laureto 《International journal of molecular sciences》2021,22(11)
The interplay between α-synuclein and dopamine derivatives is associated with oxidative stress-dependent neurodegeneration in Parkinson’s disease (PD). The formation in the dopaminergic neurons of intraneuronal inclusions containing aggregates of α-synuclein is a typical hallmark of PD. Even though the biochemical events underlying the aberrant aggregation of α-synuclein are not completely understood, strong evidence correlates this process with the levels of dopamine metabolites. In vitro, 3,4-dihydroxyphenylacetaldehyde (DOPAL) and the other two metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylethanol (DOPET), share the property to inhibit the growth of mature amyloid fibrils of α-synuclein. Although this effect occurs with the formation of differently toxic products, the molecular basis of this inhibition is still unclear. Here, we provide information on the effect of DOPAC on the aggregation properties of α-synuclein and its ability to interact with membranes. DOPAC inhibits α-synuclein aggregation, stabilizing monomer and inducing the formation of dimers and trimers. DOPAC-induced oligomers did not undergo conformational transition in the presence of membranes, and penetrated the cell, where they triggered autophagic processes. Cellular assays showed that DOPAC reduced cytotoxicity and ROS production induced by α-synuclein aggregates. Our findings show that the early radicals resulting from DOPAC autoxidation produced covalent modifications of the protein, which were not by themselves a primary cause of either fibrillation or membrane binding inhibition. These findings are discussed in the light of the potential mechanism of DOPAC protection against the toxicity of α-synuclein aggregates to better understand protein and catecholamine biology and to eventually suggest a scaffold that can help in the design of candidate molecules able to interfere in α-synuclein aggregation. 相似文献
999.
The paper reports the results of a comprehensive experimental test performed on a 6 m span timber-concrete composite beam
with glued re-bar connection. The beam had first been subjected to sustained load in unsheltered outdoor conditions for 5
years. Eventually a ramp loading test up to failure was performed. The long-term test showed an increase in deflection mainly
during the first two years, while the slip rose during the whole testing period. Thermo-hygrometric variations of environment
caused an important fluctuation of all quantities on both yearly and daily scale. By comparing experimental and analytical
results, it is highlighted that composite beams in outdoor conditions should be assigned to the 3rd service class according
to the Eurocode 5 (EC5). Analytical predictions based on approximate formulae suggested by such regulation are found to be
not conservative for the long-term behaviour and fairly accurate for the collapse behaviour. Since the simplified formulae
proposed by the latest versions of the EC5-Parts 1.1 and 2 largely underestimate the actual connection stiffness and strength,
it is recommended that realistic values of these properties, such as those obtained through push-out tests, be used when designing
timber-concrete composite beams. 相似文献
1000.
Delle Chiaie Roberto; Salviati Massimo; Fiorentini Samantha; Biondi Massimo 《Canadian Metallurgical Quarterly》2007,15(6):563
The development of therapeutic strategies for cognitive dysfunction remains one of the primary goals in the treatment of schizophrenia. The pharmacodynamic profile of mirtazapine, an antidepressant that enhances noradrenergic and serotonergic transmission, is based on a presynaptic α? antagonism and postsynaptic 5-HT? and 5-HT? antagonism. Mirtazapine shares some pharmacological similarities with that of clozapine. This 8-week open label trial aimed to discover whether the addition of 30 mg mirtazapine could potentiate the effects on cognition of an ongoing stabilized clozapine therapy in 15 persons who met the criteria for chronic schizophrenia in the Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; American Psychiatric Association, 2000). Mirtazapine adjunction was well tolerated and induced a significant improvement in cognitive performance, as measured by the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS; Randolph, 1998) total score and by the subscales for immediate and delayed memory (p 相似文献