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排序方式: 共有1378条查询结果,搜索用时 937 毫秒
1.
Among various carbon materials, diamond stands out due to excellent physical and chemical properties. In this work, we designed Dia@SiO2@Ag composites combining diamond micropowder and Ag nanoparticles by a simple chemical method and obtained stable substrate for surface enhanced Raman scattering (SERS) owing to its high surface-to-volume ratio, low density, as well as close bond between diamond and Ag. As-prepared Dia@SiO2@Ag presented high activity to detect crystal violet and rhodamine 6G molecules, which was demonstrated by significantly enhanced SERS spectra and high enhancement factor values (108-109). Moreover, Dia@SiO2@Ag also showed desired sensitivity, which was investigated by detection limit. Therefore, our study provided more theoretical support and broadened the functional applications of diamond, particularly in Raman detection. 相似文献
2.
Ceramic matrix composites (CMC) are highly required in many fields of science and engineering. However, the CMC parts always have poor surface finish. This study attempts to improve cutting performance of CMC material by combing the advantages of ultrasonic assisted cutting and diamond wire sawing. Cutting force, surface roughness, machined edge and tool wear are analyzed based on experimental results. It shows that the oscillatory movement of tool edges provides positive effect on particle ejection and residual material reduction. Ductile chip formation can be achieved due to the small tip radius of grits. Obvious decrease in cutting force, surface roughness and tool wear are obtained. Moreover, burrs, fuzzing and fracture are reduced. Meanwhile, both the surface characteristics and shape accuracy are significantly improved. These results provide a valuable basis for application of ultrasonic assisted wire sawing and understanding of CMC cutting mechanisms. 相似文献
3.
《Ceramics International》2021,47(23):33259-33268
The demand for high-performance grinding wheels is gradually increasing due to rapid industrial development. Vitrified bond diamond composite is a versatile material for grinding wheels used in the backside grinding step of Si wafer production. However, the properties of the vitrified bond diamond composite are controlled by the characteristics of the diamond particles, the vitrified bond, and pores and are very complicated. The main objective of this study was to investigate the effects of SiO2–Na2O–B2O3–Al2O3–Li2O–K2O–CaO–MgO–ZrO2–TiO2–Bi2O3 glass powder on the sintering, microstructure, and mechanical properties of the vitrified bond diamond composite. The elemental distributions of the composite were analyzed using electron probe micro-analysis (EPMA) to clarify the diffusion behaviors of various elements during sintering.The results showed that the relative density and transverse rupture strength of the composite sintered at 620 °C were 91.7% and 126 MPa, respectively. After sintering at 680 °C, the glass powder used in this study exhibited a superior forming ability without an additional pore foaming agent. The relative density and transverse rupture strength of the composite decreased to 48.2% and 49 MPa, respectively. Moreover, the low sintering temperature of this glass powder protected the diamond particles from graphitization during sintering, as determined by X-ray diffraction and Raman spectrum. Furthermore, the EPMA results indicate that Na diffused and segregated at the interface between the diamond particles and vitrified bond, contributing to the improved bonding. The diamond particles can remain effectively bonded by the vitrified bond even after fracture. 相似文献
4.
《Ceramics International》2022,48(12):17335-17342
When diamond wire saw is used in machining silicon nitride ceramics (Si3N4 ceramics), the ultra-hardness of Si3N4 causes the saw wire to wear out, which leads to the saw wire cutting performance constantly changing during its life cycle, and thus the machined quality of Si3N4 ceramics is affected. Surface roughness and topography are important indicators of the quality of the machined surface. In this paper, the diamond wire saw cutting experiment of Si3N4 ceramics was carried out, the effect of the evolution of saw wire cutting performance on the surface roughness and topography of Si3N4 ceramics as-sawn slices was investigated based on the analysis of the changes of saw wire wear topography, breaking force, bow angle and kerf loss during the sawing process. The results show that the surface roughness along the saw wire motion direction and the workpiece feed direction tends to decrease and then increase with the evolution of the cutting performance of the saw wire, which accords well with the trend of the as-sawn slices surface morphology. The results of the study can provide experimental reference for the development of high precision diamond wire saw cutting technology for Si3N4 ceramics. 相似文献
5.
《Ceramics International》2021,47(23):32736-32746
Metal-bonded diamond tools are widely used for machining hard and brittle materials such as ceramic and stone. The metal bonds are normally based on alloys composed of Fe, Co, Ni, Cu, Sn, Zn, or Cr. However, high heavy metal concentrations are hazardous to the environment and tool operators. Furthermore, the high density of these metal bonds results in excessively heavy tools, requiring high energy and intensive labor during operation. Therefore, we propose two environmentally friendly and lightweight metal bonds based on NiAl and FeAl intermetallics for diamond tools by reactive hot-press sintering. The effect of sintering temperature on the microstructure and mechanical properties of NiAl and FeAl was examined and the tribological behavior of NiAl and FeAl on Si3N4 ceramic balls was investigated. Grinding performance of the sintered diamond tools on Si3N4 ceramic was also compared. Our results reveal that B2-ordered NiAl and FeAl are obtained at sintering temperatures in the range of 700–1100 °C. The relative density of sintered NiAl is higher than that of FeAl, while the Vickers hardness and flexural strength of NiAl are lower than that of FeAl. Compared with FeAl, NiAl demonstrates higher wear resistance in a friction test against Si3N4 ceramic, while FeAl-bonded diamond tools demonstrate a higher grinding ratio than NiAl-bonded diamond tools due to enhanced self-sharpening ability. Nevertheless, diamond tools based on both NiAl and FeAl can be used to grind Si3N4 ceramics. 相似文献
6.
Xinquan Zhang Rui Huang Kui Liu A.Senthil Kumar Hui Deng 《Ceramics International》2018,44(4):4142-4153
As an important ceramic material, tungsten carbide (WC) is utilized as the typical mold in precision glass molding, which has replaced conventional grinding and polishing to provide a highly replicative process for mass manufacturing of optical glass components. Ultra-precision grinding, which is time consuming and has low reproducibility, is the only method to machine such WC molds to high profile accuracy. Although diamond turning is the most widely used machining method for fabrication of optical molds made of metals, diamond turning of WC is still considered challenging due to fast abrasive wear of the diamond tool caused by high brittleness and hardness of WC. Ultrasonic vibration cutting has been proven to be helpful in realizing ductile-mode machining of brittle materials, but its tool life is still not long enough to be utilized in practical diamond turning of optical WC molds. In the current study, a hybrid method is proposed to combine electrochemical processing of WC workpiece surface into the diamond turning process. Cutting tests on WC using poly-crystalline diamond tools were conducted to evaluate its effect on improvement of tool wear and surface quality. Validation cutting tests using single crystal diamond tools has proven that the proposed hybrid method is able to significantly reduce the diamond tool wear and improve the surface quality of machined ultra-fine grain WC workpiece compared to ultrasonic vibration cutting without electrochemical processing. 相似文献
7.
The tribology behaviors of diamond and silicon dioxide (SiO2) nanoparticles were examined via molecular dynamics simulations; four cases were simulated. At low velocity and low load, the nanoparticles separated the two blocks from each other and acted as ball-bearings. The plastic deformation, temperature distribution, and friction force were all improved due to the action of the nanoparticles. However, the crushing of the SiO2 nanoparticles was accompanied by deformation-induced loss of the rolling effect, when the load was increased. Without nanoparticles, a transfer layer formed at high velocity and low load. The two nanoparticles provided support for a certain duration. However, at high velocity and high load, the support effect of these nanoparticles was lost in a short sliding time. 相似文献
8.
Shear deformation that dominates elementary chip formation in metal cutting greatly relies on crystal anisotropy. In the present work we investigate the influence of crystallographic orientation on shear angle in ultra-precision orthogonal diamond cutting of single crystalline copper by joint crystal plasticity finite element simulations and in-situ experiments integrated in scanning electron microscope. In particular, the experimental cutting conditions including a straight cutting edge are the same with that used in the 2D finite element simulations. Both simulations and experiments demonstrate a well agreement in chip profile and shear angle, as well as their dependence on crystallography. A series of finite element simulations of orthogonal cutting along different cutting directions for a specific crystallographic orientation are further performed, and predicated values of shear angle are used to calibrate an extended analytical model of shear angle based on the Ernst–Merchant relationship. 相似文献
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