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991.
Y. Choi J. H. Park B. M. Kim J. C. Choi B. H. Min 《Metals and Materials International》2000,6(2):111-116
It is already known that the hardness number of a cold-forged product is closely related to its effective strain. This paper
presents a method of predicting the relation between effective strains and hardness by using an FE- hardness test simulation
based on the concept that hardness indicates resistance to plastic deformation. The results of the FE-simulation for the materials
are compared with those of experiments and also with those of experiments purporting to show the feasibility of the proposed
method. 相似文献
992.
Hee Jung Kim Ji Eun Park Myung Gil Choi Sangdoo Ahn Suk-Kyu Chang 《Dyes and Pigments》2010,84(1):54-58
A novel, Hg2+-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg2+-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg2+ selectivity. The Hg2+ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg2+ ions was 4.3 × 10−6 mol L−1 and the conjugate dye could be used as a chemosensor for the analysis of Hg2+ ions in aqueous environments. 相似文献
993.
During the drying stage of the cyclic corrosion test on ferritic stainless steels in the NaCl environment, the current abruptly increased and then decreased to nearly zero, indicating that pits are initiated as the salt concentration is increased, which are then repassivated when the surface is completely dry. During the wet stage, the current remained high, suggesting that pits mainly propagate during the wet stage. In contrast, in the cyclic corrosion test in the CaCl2 environment, the current was highest during the drying stage, indicating that the electrolyte is not completely dried and corrosion mainly propagates during the drying stage. 相似文献
994.
Young-Ha Kim Won-Sub Chung Ho-Hwan Chun Inwon Lee Yong-Hwan Kim Do-Hyung Kim Hyun Park 《Metals and Materials International》2010,16(2):253-258
The pH variation induced electrochemical reactions for Zn, Mg, MgO and the mixture MgMgO (25 wt.% Mg and 75 wt.% MgO) fabricated
by high-energy mechanical ball milling in 3.5 wt.% NaCl have been investigated using the potentiodynamic method and electrochemical
impedance spectroscopy to control the rate of magnesium dissolution as cathodic protection. It is known that pH variation
is a good measurement of dissolution for cathodic protection materials. The pH of Zn was modestly increased because of the
formation of ZnO. Mg showed a relatively high pH value when forming as Mg(OH)2. Highly activated MgMgO showed the highest pH value, located between Mg and MgO, of equilibrium potentials and impedance.
This indicates that the electrochemical reaction in 3.5 wt.% NaCl has been changed by mechanical ball milling. This implies
that the dissolution rate can be controlled by high-energy mechanical ball milling. 相似文献
995.
A model based on anisotropic sintering shrinkage of silicon nitride with aligned silicon nitride whisker seeds was built in order to provide an easy way to obtain information on how the large elongated grains were aligned. The method requires a simple measuring device for the information. XRD analysis showed a good correlation with predictions of the model. Both predictions of the model and experimental results indicated that the fraction of aligned large elongated grains increased as the whisker content increased. 相似文献
996.
Yun Chan Kang Yun Seup Chung Seung Bin Park 《Journal of the American Ceramic Society》1999,82(8):2056-2060
Europium-doped yttrium aluminum garnet (YAG) phosphor particles were prepared from mixed nitrate solutions by the FEAG (filter expansion aerosol generator) process. The crystallinity, morphology, and luminescence of the YAG:Eu particles were investigated. The prepared particles had an amorphous phase, which turned into phase-pure YAG particles after annealing above 1000°C. A cubic-structure YAG phase was formed by the reaction of crystalline Y2 O3 and the aluminum component. The prepared particles had spherical morphology. The mean size of the YAG:Eu particles increased from 0.45 to 1.0 µm when the overall solution concentrations were increased from 0.02 to 1.2 mol/L. The optimum doping concentration of europium for the maximum brightness of phosphor particles was 1.3 at.%. The cathodoluminescence (CL) intensity was strongly affected by the annealing temperatures. The maximum CL value of the particles was 55 cd/m2 . 相似文献
997.
The sizable potential difference between the crevice mouth and the crevice tip is difficult to explain from theories mainly
based on the chemical changes in crevice solution. In this study, the IR drop theory was adopted to explain the initiation
of crevice corrosion in the framework of IR drop in the crevice electrolyte. Furthermore, the parameters linking the two components
of potential drop — one due to accumulated charges from chemical changes of ionic species by mass transfer and the physical
one caused by the current path through the crevice electrolyte — are examined. The mathematical model is constructed and the
IR drop in the crevice is calculated using the FVM method. The chemical composition change in the crevice solution can affect
the IR drop behavior through the intermediate parameter form of ion conductivity and viscosity, etc., together with the potential
difference generated by the electric charge of locally charged ions. Viewed in this light, it can be concluded that the initiation
mechanism only by IR drop is insufficient to explain the initiation of crevice corrosion in stainless steels that have very
strong passivity. 相似文献
998.
Design of Bulk metallic glasses with high glass forming ability and enhancement of plasticity in metallic glass matrix composites: A review 总被引:1,自引:0,他引:1
To overcome some of the limits of existing metallic alloys, a new alloy design concept has been introduced recently in order
to control the crystallinity, i.e. to utilize crystalline, quasicrystalline, and amorphous structures. In particular, bulk
metallic glasses (BMGs) receive great attention because of their unique properties due to their different atomic configuration.
Recently, significant progress in enhancing glass forming ability (GFA) has led to the fabrication of BMGs having potential
for application as structural and functional materials. Moreover, successful design of BMG matrix composite microstructure
suggests that the plasticity of BMGs can be controlled properly. In this review article, we introduce recent research results
on the design of BMGs with high GFA and on the enhancement of plasticity in metallic glass matrix composites. 相似文献
999.
In-Gyu Park Chang-Soon Lee Seong-Sik Hwang Hong-Pyo Kim Joung-Soo Kim 《Metals and Materials International》2005,11(5):401-409
In order to evaluate the stress corrosion cracking resistance for commercial alloys (C600MA, C600TT, C690TT) and Korean-made
alloys (K600MA, K690TT), C-ring tests were performed in a caustic environment of 4, 10, 20, 30, and 50% NaOH solution at 315°C,
for 480 h with an applied potential of 125 mV vs. OCP. Different stress corrosion cracking phenomena were observed according
to the NaOH concentration. The rate of caustic IGSCC attack did not appear to increase monotonically with caustic concentrations,
but peaked at a concentration between 4 and 50% caustic, or approximately 30% NaOH. Intergranular stress corrosion cracking
was found for C600MA in 10, 20, and 30% NaOH solutions, while no cracking was observed in the 4 and 50% NaOH solutions. In
30% NaOH solution, transgrnular stress corrosion cracking was detected in C690TT, which may be related with the large amount
of plastic strain (150% yield) and the applied potential (125 mV vs. OCP). The overall data clearly indicate that C600MA has
the worst SCC resistance while K690TT offers the best resistance. There is also fairly good correlation between the caustic
SCC susceptibility and some metallurgical parameters, particularly the grain size and the yield strength at room temperature.
Specifically, materials having larger grain size and lower yield strength exhibited higher caustic SCC resistance. 相似文献
1000.
Park Sangwon Nam Hyunbin Na Youngsang Kim Hyoungseop Moon Younghoon Kang Namhyun 《Metals and Materials International》2020,26(5):641-649
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of... 相似文献