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101.
High-energy NdFeB magnets and their applications 总被引:3,自引:0,他引:3
In sintered NdFeB magnets, additive elements for increasing coercivity decrease residual magnetization. Also, fine magnetic
powder oxidization prevents identification of the stoichiometry composition (Nd
2Fei14B).To improve the magnetic properties of a sintered NdFeB magnet, the authors have developed a method involving two alloys. Magnetic
Nd
2Fei14Balloy and a rare- earth- rich alloy (including richer dysprosium content) are melted individually and mixed together after
coarse pulverization. After the sintering process, dysprosium in the sintered body is enriched in each grain region near the
grain boundary. The two- alloy method minimizes the liquid phase necessary to keep the coercive force at a useful level, and
thus results in compositions closer to stoichiometry. The energy product of magnets having an inhomogeneous dysprosium distribution
is typically 360 kj - m
- 3
(45 MG.Oe) at production level. The corrosion characteristics of cobalt- substituted NdFeB magnets also were investigated.
These magnets are now used in voice coil motors for hard disk drives and contribute to shortening access time and hard- drive
downsizing. 相似文献
102.
镍对热镀锌耐蚀性的影响 总被引:1,自引:0,他引:1
对Q235和Q345两种材料表面热浸镀纯Zn和Zn-Ni合金,研究Ni对热镀锌耐蚀性的影响。采用中性盐雾试验对镀层耐蚀性测试,将纯Zn镀层和Zn-Ni合金镀层进行对比,并用电子天平称量试样重量变化。结果表明Zn-Ni合金镀层比纯Zn镀层更耐腐蚀。 相似文献
103.
104.
电沉积法制备纳米晶材料 总被引:9,自引:0,他引:9
电沉积法是制备完全致密的纳米晶体材料最有前途的方法之一。本文综述了电沉积法制备纳米晶镍及其合金的研究现状及制备方法对纳米晶材料性质的影响。 相似文献
105.
106.
PAN Ximiao JIN ZhanpengPhase Diagram Materials Design Center School of Materials Science Engineering Central South University Changsha China 《稀有金属(英文版)》2003,22(3)
The phase equilibrium relations of the ternary Ni-Ta-Zr system at 1223 K were investigated by means of diffusion triple and electron probe microanalysis (EPMA) techniques. Two ternary compounds were found and a series of tie lines and tie triangles have been determined. The maximum solubility of Ta in NiZr2 is about 13.5% (atom fraction). The corresponding tentative isothermal section at this temperature was constructed based on current experimental information. 相似文献
107.
本文提出了铝箔-磷酸·硼酸混合液组成的除氯、除氟体系,有效地消除氟、氯等元素对硫的电导法测定的干扰;系统地研究了铝箔的用量、燃烧温度、燃烧时间、氧气流速对除氯、除氟和二氧化硫的析出及测定的影响。提出了采用燃烧-电导法测定电解镍粉中硫含量的最佳条件。本法测定含硫量为0.0020%的镍粉试样时,相对标准偏差为0.0002%,硫的回收率为98.38%,检测下限为0.0002%,该法操作简便,测量下限低,结果准确可靠,经济实用。 相似文献
108.
高镍球铁的球化、孕育工艺的热分析 总被引:1,自引:0,他引:1
采用热分析的方法分析高镍球铁的球化、孕育效果及球化衰退过程中温度-时间曲线特征点的变化;对高镍球铁的球化衰退时间进行具体的试验分析.结合金相组织照片对石墨形态变化过程进行观察和验证.结果表明:MgNi球化剂球化效果良好,在4~6 min内浇注不会产生球化衰退. 相似文献
109.
The effects of long-term aging on microstructures and their influence on tensile and stress-rupture behavior of a corrosion
resistant nickel-base superalloy are investigated. Samples are aged isothermally at 1073, 1123, or 1173 K for different times
of up to 10,000 h and mechanical tests are performed on samples in both standard heat treatment (SHT) and aged conditions.
Scanning electron microscopy (SEM) studies reveal that the coarsening kinetics of γ′ follows a linear law at different temperatures
with the calculated activation energy, i.e., 255 kJ/mol, for γ′ growth according to Lifshitz-Slyozof-Wagner (LSW) theory.
After long-term aging for more than 1 khours, σ phase appears in the alloy. The kinetics of σ formation can be described by
the Johnson-Avrime-Mehl equation. Tensile experiments at room temperature and 1173 K and endurance experiments at 1173 K/274
MPa are performed to test the effect of σ phases on these properties and no remarkable harmful effect is found. γ′ coarsening
can be used to explain the reduction of yield stress, which is tested by the Labusch-Schwarz hardening theory. Although the
presence of the σ phase clearly does affect the fracture process, the σ phase does not embrittle the alloy. 相似文献
110.
Reconstructed exit waves are useful to quantify unknown structure parameters such as the position and composition of the atom columns at atomic scale. Existing techniques provide a complex wave in a flat plane which is close to the plane where the electrons leave the atom columns. However, due to local deviation in the flatness of the exit surface, there will be an offset between the plane of reconstruction and the actual exit of a specific atom column. Using the channelling theory, it has been shown that this defocus offset can in principle be determined atom column-by-atom column. As such, the surface roughness could be quantified at atomic scale. However, the outcome strongly depends on the initial plane of reconstruction especially in a crystalline structure. If this plane is further away from the true exit, the waves of the atom columns become delocalized and interfere mutually which strongly complicates the interpretation of the exit wave in terms of the local structure. In this paper, we will study the delocalization with defocus using the channelling theory in a more systematic way. 相似文献