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81.
82.
The PbO2 and F−-doped PbO2 (F-PbO2) film electrodes have been prepared by an electrodeposition process onto platinum substrate. The changes of their electrochemical activity for oxygen evolution (OE) reaction with accelerated electrolysis time have been studied. The results show that the activity of the electrodes decreases with increasing electrolysis time. This can be attributed to the conductivity variations, which are caused by the decrease of the oxygen vacancy concentration in PbO2 films during OE. The mechanism of the decrease of the oxygen vacancies has been investigated. For F-PbO2 film electrodes, though its electrochemical activity is somewhat lower than that of undoped one, its activity stability is much higher in comparison with that of PbO2. The influence of F− doping on the activity of PbO2 film electrodes has been also discussed. 相似文献
83.
Effect of Acceptor and Donor Dopants on the Dielectric and Tunable Properties of Barium Strontium Titanate 总被引:1,自引:0,他引:1
Xiaofeng Liang Zhongyan Meng Wenbiao Wu 《Journal of the American Ceramic Society》2004,87(12):2218-2222
The effects of different concentrations of Mn2+ , Mg2+ , Al3+ , Fe3+ , La3+ , and Nb5+ on the dielectric and tunable properties of Ba0.6 Sr0.4 TiO3 ceramics were investigated. It was found that doping in small amounts with acceptor ions such as Mg2+ , Fe3+ , and Al3+ could meliorate the dielectric properties clearly. Decrease of dielectric loss was attributed to the formation of compensating defects originating from acceptor substitution. It was concluded that the tunability was linked to both the dielectric constant and the grain size. A higher figure of merit was obtained by doping the ceramics with smaller ions of Al and Fe, compared to Ti. 相似文献
84.
掺Tb3+钛酸铅粉末的制备和结晶行为 总被引:1,自引:0,他引:1
采用溶胶喂胶法制备了Tb^3 掺杂钛酸铅(PbTiO3,PT)超细粉末,分别用差热分析、透射电子显微镜、X射线衍射仪对其相结构、形貌特性以及晶粒粒径等进行了分析测试。结果表明:这种粉末在约600℃热处理温度下,由非晶基体转变形成钙钛矿相的过程已逐步完成,其晶粒平均尺寸约为18nm,比未掺Tb抖的PT粉末中的钙钛矿晶粒尺寸略小。形成的钙钛矿结构中,Tb^3 取代Pb^2 进入晶格位置,产生阳离子空位,诱发晶格畸变,使钙钛矿相的析晶能力比相同热处理条件下未掺杂Tb^3 的PT低。另外,掺Tb^2 的PT中钙钛矿相的晶轴比c/a比未掺Tb^3 的PT中的低,这类似于产生了赝立方结构,降低了从立方相向这种四方相转化的势垒,有效地抑制了较高温下焦绿石相的产生,使掺Tb^3 的PT中焦绿石相稳定存在的温度比未掺Tb^3 的PT中低约100℃。 相似文献
85.
Deyu Wang 《Electrochimica acta》2005,50(14):2955-2958
LiFePO4 doped by bivalent cation in Fe-sites show improved rate performance and cyclic stability. Under 10 C rate at room temperature, the capacities of LiFe0.9M0.1PO4 (M = Ni, Co, Mg) maintain at 81.7, 90.4 and 88.7 mAh/g, respectively, in comparison with 53.7 mAh/g for undoped LiFePO4 and 54.8 mAh/g for carbon-coated LiFePO4 (LiFePO4/C). The capacity retention is 95% after 100 cycles for doped samples while this value is only 70% for LiFePO4 and LiFePO4/C. Such a significant improvement in electrochemical performance should be partially related to the enhanced electronic conductivities (from 2.2 × 10−9 to <2.5 × 10−7 S cm−1) and probably the mobility of Li+ ions in the doped samples. 相似文献
86.
过渡金属离子掺杂纳米TiO2的相变与光催化活性 总被引:4,自引:0,他引:4
采用溶胶-凝胶法制备了掺杂Mo6+、Cr3+、Fe3+的改性纳米TiO2光催化剂,并分别在550℃和580℃下对其进行了热处理,考察了热处理温度对掺杂纳米TiO2相变和光催化活性的影响.通过光催化降解染料罗丹明B实验,对在不同热处理温度下Mo6+、Cr3+、Fe3+改性以及不同Mo6+掺杂量的TiO2光催化活性进行了评价,发现掺杂离子对TiO2光催化活性的影响与其对TiO2相转变的作用是一致的,即抑制相转变的同时也提高了光催化活性.实验结果也进一步表明,Mo6+掺杂量为0.05%(摩尔分数)时的TiO2具有最佳光催化活性. 相似文献
87.
Nd2O3掺杂BaTiO3陶瓷的结构和电性能研究 总被引:5,自引:0,他引:5
研究了组份为Ba1-xNdxTiO3(x=0.002-0.04)陶瓷的结构和电性能,实验结果表明:当0.002≤x≤0.004时,轻度Nd2O3掺杂的BaTiO3陶瓷呈半导体;而当0.012≤x≤0.04时呈绝缘性。BaTiO3陶瓷的室温电阻率ρv随Nd^3+含量的变化呈U型特曲线。组份为Ba0.9970Nd0.0030TiO3的材料具有最低的ρv和最佳的PTCR效应,相应于最大的平均晶粒尺寸和最 相似文献
88.
以盐酸胍为前驱体,硝酸锆为锆源,通过热聚合法制备了Zr掺杂的Zr/g-C3N4光催化剂。运用XRD、SEM、UV-Vis DRS、PL、XPS、BET等手段对催化剂的结构、形貌、光学性能进行了表征分析。结果表明:Zr掺杂改性的Zr/g-C3N4光催化剂拓宽了可见光的吸收,增大了比表面积,且降低了光生电子-空穴的复合率,具有较好的光催化活性。可见光照射下,在60 min内,5Zr/g-C3N4对罗丹明B(RhB)的光催化降解率达99.29%,光催化降解过程符合一级动力学方程,其速率常数k= 0.08647 min-1,是纯g-C3N4的8.3倍。捕获剂实验发现降解RhB的主要活性物种为超氧自由基,并推测了可能的反应机理。 相似文献
89.
This paper investigates the ability of a shear wave reflection (WR) method to monitor microstructural changes of Portland cement mortar during hydration. The wave reflection method measures the reflection loss of shear waves at an interface between a steel plate and mortar. Mortars with water/cement ratios of 0.35, 0.5 and 0.6 were tested at isothermal curing conditions of 25 °C. The numerical model HYMOSTRUC3D was used to simulate the evolution of microstructural properties of the cement paste phase of the tested mortars. The parameters obtained from the simulations were the volume fraction of the total and connected solid phase and the specific contact area of the hydrated cement particles. The investigations have shown that the wave reflection measurements are governed primarily by the degree of the inter-particle bonding of the cement particles as calculated from the specific contact area of a simulated microstructure. 相似文献
90.
Ki Soo ParkMyung Hun Cho Sang Ho ParkKee Suk Nahm Yang Kook SunYun Sung Lee Masaki Yoshio 《Electrochimica acta》2002,47(18):2937-2942
Layered Li0.7[M1/6Mn5/6]O2 (M=Li, Ni) was synthesized using a sol-gel method. P2-Na0.7[M1/6Mn5/6]O2 precursor was first synthesized by a sol-gel method, and then O2-Li0.7[M1/6Mn5/6]O2 was prepared by an ion exchange of Li for Na in P2-Na0.7[M1/6Mn5/6]O2 precursor. From charge/discharge curves, it was seen that Li0.7[Li1/6Mn5/6]O2 has two plateaus similar to those observed from a spinel structure, but Li0.7[Ni1/6Mn5/6]O2 holds a single plateau as observed from a typical layered structure. It was considered that Li0.7[Li1/6Mn5/6]O2 undergoes a phase transformation from layered to spinel structure during the charge/discharge cycle, but Li0.7[Ni1/6Mn5/6]O2 maintains O2-layered structure after the cycles. Li0.7[Ni1/6Mn5/6]O2 was higher in discharge capacity and retention rate than Li0.7[Li1/6Mn5/6]O2. 相似文献