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51.
As superconducting generators have a number of advantages, the investigations for such machines have actively been carried out throughout the world. In the superconducting generator, it is very important to support the field winding and to protect it from quenching. On the other hand, since the armature winding is of air core, the evaluation of eddy current loss in the winding and the way it is supported arc inevitable. Thus, the magnetic fields and the electromagnetic forces acing on both the field and the armature windings at the early stages of the machine design should be known. In previous papers the transient behavior of magnetic fields and electromagnetic forces acting on the windings of a superconducting generator based on a computer simulation for a sudden 3-phase fault have been discussed in part. However, the behavior of magnetic fields and electromagnetic forces during transient period is very complicated and many calculations are required to determine their maximum values. In this paper, for practical use at the early stages of the machine design, approximate expressions are derived to calculate the maximum values of the magnetic fields and electromagnetic forces on the windings in the case of a 3-phase fault. To check these expressions numerically, a 1000-MVA superconducting generator was conceptually designed. The numerical results obtained by using these expressions agree well with the computer simulation results. 相似文献
52.
Naoki Kameoka Hiroyuki Kita Eiichi Tanaka Jun Hasegawa Ken-Ichi Nishiya 《Electrical Engineering in Japan》1995,115(1):22-34
This paper presents a method for obtaining preventive control strategies based on nonlinear optimization for power systems which will incur voltage instability when load demand increases. An algorithm is proposed to determine an appropriate and effective control action taking into account the operating constraints to widen the margin between the present operating point and a voltage collapse point, thereby improving the system state. The method proposed here is based on a complex-valued load-flow technique using the Newton-Raphson method which has been developed already by the authors. Consequently, the preventive control algorithm also can evaluate the voltage instability in the event the present operating point becomes closer to the critical point and the system state becomes unfeasible at increased loading point. Further, in optimization, two-types of objective functions are introduced so that voltage stabilization and dissolution of constraint violation can be attained simultaneously. In addition, this paper discusses the extension of the proposed preventive control to the successive control method which carries out the control action to avoid voltage collapse while the load demand is increasing. Numerical examples for various model systems demonstrate the effectiveness of the proposed method. 相似文献
53.
The interaction of water with wood, such as bamboo and cedar, is investigated by measuring their complex piezoelectric, dielectric, and elastic constants between -150 and 150°C at 10 Hz. Bamboo and cedar are found to have two hydration-dependent elastic loss peaks; one is observed at about -100°C and the other at about -40°C. The former loss peak is due to the adsorbed water in the hydration range between 0 and 4% moisture content (MC) and the latter to the adsorbed water above 4% MC. These two types of water are considered bound on different sites in the regions around crystalline cellulose, where molecules of one type associate with each other and molecules of the other are unassociated. We consider that the piezoelectric polarization of wood is attributed to the rotation of hydroxyl groups in the crystal lattice of cellulose. The piezoelectric constants are observed to decrease but the elastic and dielectric constants to increase with increasing hydration. The effect of adsorbed water on elastic losses in bamboo and cedar are found to be similar to that in collagenous substances. 相似文献
54.
55.
Microscopic observation of carbons obtained from pure aromatic hydrocarbons by the aid of carbonization catalysts was carried out to clarify the microstructure of these carbons of different features. Reflected polarized-light microscopy distinguished needle, mosaic and isotropic cokes, former two of which were produced with aluminum chloride and the last with potassium. High resolution microscopy revealed that these carbons calcined at 1250° had different degree of layered structure, corresponding to the crystallographic parameters of these samples graphitized at 2500°C. The reasons for the carbons produced with potassium to be non-graphitizable are discussed from the macro- and micro-features of the carbons. 相似文献
56.
Ohmic contacts to Si-implanted, n+ layers on semi-insulating InP are investigated on the basis of the transmission line model. It is found that Au/Ni/AuGeNi/InP system shows a good ohmic behaviour with the specific contact resistance and the minimum contact resistance for a Si-dose higher than 2 × 1014 cm?2 at 100 or 200 keV. The results indicate that, in the FET fabrication, at least 120 μm in length is necessary in order to obtain source and drain electrodes with the minimized resistance. 相似文献
57.
58.
Ryo Watanabe Yasushi Sekine Masahiko Matsukata Eiichi Kikuchi 《Catalysis Letters》2009,131(1-2):54-58
We investigated novel LaMnOx perovskite-oxide (ABO3) catalysts for effective catalytic dehydrogenation of ethylbenzene to produce styrene monomer. Comparison with industrial Fe–K catalyst, our La0.8Ba0.2Mn0.6Fe0.4O3-δ catalyst showed higher activity. Results show that the A-site in perovskite-type oxides affected catalytic dehydrogenation activities and that the B-site affected stability of the activities. 相似文献
59.
Tarahomjoo S Katakura Y Satoh E Shioya S 《Journal of Bioscience and Bioengineering》2008,105(2):116-121
With the aim of constructing an efficient protein display system for lactic acid bacteria (LABs), the effect of fusion direction on the cell-surface binding activity of the C-terminal region of the peptidoglycan hydrolase (CPH) of Lactococcus lactis IL1403 was studied. CPH fused to the alpha-amylase (AMY) of Streptococcus bovis 148 either at its C-terminus (CPH-AMY) or at its N-terminus (AMY-CPH) was expressed intracellularly in Escherichia coli. This domain was able to direct binding of AMY to the surface of L. lactis ATCC 19435 in both constructs. However, the number of bound molecules per cell and the specific activity for starch digestion in the case of CPH-AMY were 3 and 14 times greater than those in the case of AMY-CPH, respectively. Of the LABs tested, L. lactis ATCC 19435 showed the highest binding capability for CPH-AMY, up to 6 x 10(4) molecules per cell, with a dissociation rate constant of 5.00 x 10(-5) s(-1). The binding of CPH-AMY to the surface of Lactobacillus delbrueckii ATCC 9649 cells was very stable with a dissociation rate constant of 6.96 x 10(-6) s(-1). The production of CPH-AMY in the soluble form increased 3-fold as a result of coexpression with a molecular chaperone, trigger factor. The results of this study suggest the usefulness of CPH as a bidirectional anchor protein for the production of cell-surface adhesive enzymes in E. coli. Furthermore, the importance of the fusion direction of CPH in determining cell-surface binding and enzymatic activities was shown. 相似文献
60.
Chika Takashima Yasuhiro Kosuge Masahisa Inoue Shin-Ichi Ono Eiichi Tokuda 《International journal of molecular sciences》2021,22(8)
Superoxide dismutase 1 (SOD1) is a metalloenzyme with high structural stability, but a lack of Cu and Zn ions decreases its stability and enhances the likelihood of misfolding, which is a pathological hallmark of amyotrophic lateral sclerosis (ALS). A growing body of evidence has demonstrated that misfolded SOD1 has prion-like properties such as transmissibility between cells and intracellular propagation of misfolding of natively folded SOD1. Recently, we found that SOD1 is misfolded in the cerebrospinal fluid of sporadic ALS patients, providing a route by which misfolded SOD1 spreads via the extracellular environment of the central nervous system. Unlike intracellular misfolded SOD1, it is unknown which extracellular misfolded species is most relevant to prion-like properties. Here, we determined a conformational feature of extracellular misfolded SOD1 that is linked to prion-like properties. Using culture media from motor neuron-like cells, NSC-34, extracellular misfolded wild-type, and four ALS-causing SOD1 mutants were characterized as a metal-free, disulfide oxidized form of SOD1 (apo-SOD1S-S). Extracellular misfolded apo-SOD1S-S exhibited cell-to-cell transmission from the culture medium to recipient cells as well as intracellular propagation of SOD1 misfolding in recipient cells. Furthermore, culture medium containing misfolded apo-SOD1S-S exerted cytotoxicity to motor neuron-like cells, which was blocked by removal of misfolded apo-SOD1S-S from the medium. We conclude that misfolded apo-SOD1S-S is a primary extracellular species that is linked to prion-like properties. 相似文献