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61.
M. Sherif El-Eskandarany M. Omori T. Hirai T. J. Konno K. Sumiyama K. Suzuki 《Metallurgical and Materials Transactions A》1998,29(7):1973-1981
Nearly equiatomic nanocrystalline titanium nitride (Ti56N44) powder with an average grain size of 5 nm has been synthesized by ball milling elemental Ti powder under nitrogen gas flow
at room temperature. During the first stage of reactive ball milling (RBM) (time <3.6 ks), the metallic Ti powder tends to
agglomerate to form powder particles with a larger diameter. At the second stage (3.6 to 22.0 ks), the agglomerated particles
of Ti fragment to form smaller particles. These smaller particles that have new or fresh surfaces begin to react with the
milling atmosphere (nitrogen) during the third stage of milling (22 to 86 ks) to form TiN powder coexisting with unreacted
Ti powder. Toward the end of milling (86 to 173 ks), a single phase of nanocrystalline TiN (NaCl structure) is obtained. The
powder of this end-product has a spherical-like morphology with an average particle size of about 0.4 μm diameter. A sintering
procedure using plasma activation has been employed to consolidate the powder particles at several stages of the RBM. The
as-milled and as-consolidated powders have been characterized as a function of the RBM time by means of X-ray diffraction
(XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical metallography, and chemical analyses.
Density measurements of the consolidated samples show that after 86 to 173 ks of the RBM time, the compacted samples are essentially
fully dense (above 96 pct of the theoretical density for TiN). The results also show that the consolidated TiN compacts still
maintain their unique nanocrystalline properties with an average grain size of about 65 nm. The hardness and some mechanical
properties of the consolidated TiN compacts have been determined as a function of the RBM time. 相似文献
62.
Kikuo Wakino Tsutomu Okada Norio Yoshida Kunisaburo Tomono 《Journal of the American Ceramic Society》1993,76(10):2588-2594
The dielectric constant of a compound consisting of two different materials was simulated using the Monte Carlo and finite element methods. In the high concentration range of the higher dielectric constant material, the simulated value of the dielectric constant showed a "parallel-model"-like tendency. On the other hand, in the low concentration range of the higher dielectric constant material, the compound showed a "serial-model"-like behavior. Around 65% content of the higher dielectric constant material, it exhibited results similar to the logarithmic mixing rule. After careful consideration of these results, a new equation to predict the dielectric constant of the compound was derived. The agreement between the dielectric constant calculated by the new equation and the measured values was better than in any other case reported before. 相似文献
63.
Summary The effect of initiating groups introduced onto silica surface on the molecular weight of grafted polystyrene chain was investigated. By the treatment of polystyrene-grafted silica with aqueous solution of alkali, surface grafted polystyrene was isolated from the surface. The molecular weight of polystyrene grafted onto the silica obtained from the radical graft polymerization initiated by peroxyester groups introduced onto the surface was found to be much larger than that from the cationic polymerization initiated by acylium perchlorate groups. The number of grafted polystyrene in the radical polymerization, however, was much less than that in the cationic polymerization. Furthermore, the effect of molecular weight of grafted polystyrene on the dispersibility of silica in tetrahydrofuran was examined. 相似文献
64.
Telecommunication Systems - 相似文献
65.
Surface treatment using alkaline solutions was attempted to enhance the surface hydrophilicity and enzymatic hydrolyzability of hydrophobic poly(L ‐lactide) [ie poly(L ‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL). The alkaline treatment was performed by immersing the PLLA and PCL films in 0.01 and 4 N NaOH solutions, respectively, for various periods of time. The effects of the alkaline treatment on the hydrophilicity of the films were monitored by dynamic contact angle measurements, while the enzymatic hydrolyzability of the PLLA and PCL films after the alkaline treatment were evaluated by weight losses in the presence of proteinase K and Rhizopus arrhizus lipase, respectively. With the alkaline treatment the hydrophilicity of the PLLA and PCL films was controllable in the advancing contact angle (θa) ranges of 84–108° and of 69–93°, respectively, by varying the alkaline treatment time. The enzymatic hydrolysis rates of the PLLA films became higher with decrease of the θa, irrespective of the crystallinity, strongly suggesting that the surface hydrophilicity or the surface molecular weight is crucial to determine their enzymatic hydrolyzability. In contrast, the enzymatic hydrolyzability of the PCL films remained unchanged even when the θa decreased from 93° to 73° by alkaline treatment for 4 h. However, prolonged alkaline treatment for periods of time exceeding 4 h, which insignificantly altered the θa but caused the formation of pores and cracks on the PCL film surface, accelerated the enzymatic hydrolysis of the PCL films. This indicates that the enzymatic hydrolyzability of the PCL film depends on the surface area per unit weight rather than the surface hydrophilicity. Copyright © 2003 Society of Chemical Industry 相似文献
66.
Debasish Chakraborty Goutam Chakraborty Norio Shiratori 《International Journal of Network Management》2003,13(5):321-335
In this paper we propose a QoS‐based routing algorithm for dynamic multicasting. The complexity of the problem can be reduced to a simple shortest path problem by applying a Weighted Fair Queuing (WFQ) service discipline. Using a modified Bellman–Ford algorithm, the proposed routing builds a multicast tree, where a node is added to the existing multicast tree without re‐routing and satisfying QoS constraints. With user defined life‐time of connection this heuristic algorthm builds multicast tree which is near optimum over the whole duration of session. Simulation results show that tree costs are nearly as good as other dynamic multicast routings that does not consider QoS. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
67.
Shin’ichi Konno Shigeo Kazama Maki Hiraoka Hirokazu Sakamoto Kenji Mizoguchi Hiromi Taniguchi Toshikazu Nakamura Kou Furukawa 《Journal of Low Temperature Physics》2006,142(3-4):621-624
β′-(BEDT-TTF)(TCNQ) is a compound of BEDT-TTF (=ET) and TCNQ molecules aligned orthogonally with each other, forming two-dimensional
sheets and one-dimensional columns of 1/4-filled π band, respectively. It is known that the metal-insulator transition occurs
at 330 K at ambient pressure. We have measured the electronic spin susceptibility by means of the EPR-NMR method at 50 MHz,
and the angular dependence of g-factor and line width of EPR both at Q (34 GHz) and W (94 GHz) band. We successfully confirmed
that the antiferromagnetic transition occurs in ET sheets and TCNQ columns, independently. 相似文献
68.
The so-called pseudo-orthogonal property of the eigenfunction expansion form is proved to be valid for the case of an antiplane interface V-notch and the corresponding path-independent integral is derived. The relation between the path-independent integral and the stress intensity factor of the notch is found. The influence of loads on the related integral is also presented. 相似文献
69.
Masaaki Miyamoto Hiroyuki Koike Toshio Sada Yasuteru Ijima Junichiro Fukushige Norio Nakamura 《Lipids》1991,26(12):1316-1319
Platelet-activating factor (PAF) is a potent inflammatory mediator which is released by various inflammatory cells and produced
by certain tissues, including the kidney. PAF has been shown to increase glomerular permeability to protein and to decrease
glomerular filtration rate (GFR) by contracting mesangium. On the basis of these observations, it has been suspected that
PAF may play a role as mediator of glomerular damage in glomerular nephritis. To examine this possibility, we studied the
effects of a specific PAF antagonist, R-75,317, on the development of an experimental model of anti-glomerular basement membrane
(anti-GBM) glomerulonephritis. Glomerulonephritis was initiated by injecting rabbit anti-rat GBM serum into rats. Proteinuria
gradually developed after serum injection, plateaued at week 2, and remained at the high level of week 2 throughout the experimental
period (6 wk). Chronic treatment with R-75,317 (10 mg/kg/day i.p.) tended to delay the onset of proteinuria and significantly
accelerated the recovery phase. Creatinine clearance (Ccr) fell to 40% at week 3. R-75,317 treatment completely prevented
this decline of Ccr. Histological changes in this model (glomerular hypertrophy, proliferation of mesangial matrix and interstitial
fibrosis) were also ameliorated by the R-75,317 treatment. The results suggest that PAF may play a role in the development
of glomerulonephritis and that PAF antagonists could be used in the treatment of human renal disease.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, May 1989. 相似文献
70.