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1.
《Ceramics International》2022,48(9):12209-12216
We report the structural, magnetic, electrical and broadband microwave absorption in La0.7Na0.3MnO3 sample synthesized by microwave (MW) irradiation (Na0.3LMO_MW) and compare them to the sample synthesized by solid-state (SS) reaction method (Na0.3LMO_SS). Single phase Na0.3LMO_MW was synthesized at 800 °C in 30 min, whereas, Na0.3LMO_SS sample was obtained by sintering at 1200 °C for 48 h. Although both these samples show ferromagnetic transition at TC ~324.8 K, the MW-synthesized sample shows distinct physical properties: broad ferromagnetic transition, smaller saturation magnetization, a large difference between the magnetic ordering and metal-insulator transition temperatures, a large high-field magnetoresistance, a table top-like magnetocaloric effect, and a large low-field microwave absorption compared to the solid state synthesized sample. These differences are suggested to arise from magnetic heterogeneity induced by smaller grain size and surface spin disorder in the MW synthesized La0.7Na0.3MnO3.  相似文献   
2.
田宁  刘晓娟  张大军  栾天 《化学试剂》2022,44(3):477-483
为开发高效低毒的抗肝癌天然产物衍生物,依据药物拼合原理设计并合成了一系列未见文献报道的熊果酸衍生物。将熊果酸与不同取代的N-苄基吲哚片段通过Claisen-Schmidt缩合反应得到目标化合物,其化学结构均经过核磁氢谱、核磁碳谱以及质谱的联合确证。采用噻唑蓝(MTT)法考察其体外抗肝癌活性,结果表明,2-{[1-(2-氟苄基)-1 H-吲哚基]-3-次甲基}-3-羰基熊果酸(4b)与2-{[1-(3-氟苄基)-1 H-吲哚基]-3-次甲基}-3-羰基熊果酸(4c)对HepG2及BEL-7402两种肝癌细胞株的抑制活性优于熊果酸及阳性对照药氟尿嘧啶,同时对正常肝细胞L02的毒性显著降低。化合物4c的体外抗肝癌活性最为理想(针对HepG2的IC50值为3.22μmol/L,选择性指数为6.89),分子对接实验模拟其作用靶标或为RNA聚合酶Ⅱ,可对其深入研究用以开发高效低毒的抗肝癌药物。  相似文献   
3.
《Ceramics International》2022,48(9):12118-12125
In this study, (Cu1/3Nb2/3)4+ complex cation and BaO–ZnO–B2O3 glass frit were adopted to solve the high sintering temperature and poor temperature stability of Ba3Nb4Ti4O21 ceramics. It is shown that pure Ba3Nb4Ti4O21 phase was formed when Ti site was partially replaced by (Cu1/3Nb2/3)4+ cation. The increasing number of dopants decreases the dielectric polarizability, correspondingly, the dielectric constant and temperature coefficient of the resonance frequency values are reduced consistently. The variation of the Q × f value is determined by internal ionic packing fraction and external sintering densification. The (Cu1/3Nb2/3)4+ cation effectively decreases the suitable sintering temperature from 1200 to 1050 °C while greatly improving the temperature stability. BaO–ZnO–B2O3 glass was used to further improve the low-temperature sintering characteristics of Ba3Nb4Ti4O21 ceramics. It is proven that the addition of glass frits effectively decreases the temperature to 925 °C with combinational excellent microwave dielectric properties: εr ~55.6, Q × f ~5700 GHz, τf ~3 ppm/°C, making the Ba3Nb4Ti4O21 ceramics promising in the applications of low-temperature cofired ceramic technology.  相似文献   
4.
Using spark plasma sintering (SPS), >98.5 % dense boron carbide (B4C) samples were made from commercially available and lab-synthesised powders made via a low temperature synthesis (LTS) process. The work showed that the LTS powder can be produced in batches of tens to hundreds of grams whilst maintaining a high purity material with lower levels of residual free carbon (20.6–21.3 wt.% C) than commercially available samples (22.4 wt.% C). The LTS material was seen to exhibit higher hardness values (37.8 GPa) than the commercial grade material (32.5 GPa) despite featuring a coarser average grain size (10.8 μm and 2.4 μm respectively). This is largely thought to be due to the influence of ZrO2 and AlB2 impurities introduced to the material during micronising milling of the powder after synthesis, as opposed to the influence of the materials lower carbon content.  相似文献   
5.
Higher alcohols synthesis (HAS) from syngas (CO/H2) has attracted widespread attention, while the low selectivity and poor stability of the catalysts mainly stumbled its industrial application. In the work, Ni–Co alloy nanoparticles (NPs) derived from Co1-xNixAl2O4 loaded on the SiO2 with large specific surface area were prepared; and during reaction, the highly dispersed Ni–Co alloys were self-optimized to Ni–Co alloy@Co–Co2C. Importantly, Ni–Co alloy@Co–Co2C can be regenerated through oxidation - reduction - self-optimization process. Characteristic results indicated that the structural liberalization during the reaction process inhibited the loss of Ni, regulated and balanced the dual active sites of the catalyst and the Ni–Co alloys were regenerated after the re-oxidation and re-reduction process. The optimized catalyst exhibited excellent catalytic performance, including a high total selectivity to alcohols of 39.3% and an excellent catalytic stability at 250 °C, 3.5 MPa (H2/CO = 2) and a space velocity of 6000 mL (gcat h)?1. In addition, the Ni–Co alloy@Co–Co2C catalyst after stability test could recover its original catalytic performance after re-oxidation and re-reduction. The renewable characteristics and superior catalytic performance of Ni–Co alloy@Co–Co2C made the catalyst to be one of the potential industrial catalysts for HAS.  相似文献   
6.
为解决五唑金属盐合成中分离纯化困难等问题,以芳基五唑C—N切断反应后处理所得五唑钠水溶液为研究对象,采用沉淀法对五唑金属盐进行了分离纯化研究。结果表明,五唑钠水溶液中含有大量有机酸盐,以及硝酸钠、氯化钠等无机盐杂质。与N5负离子相比,有机酸根更易与金属离子形成沉淀,从而影响五唑金属盐析出。将五唑钠水溶液调节为酸性,萃取除去有机酸盐后加入氯化钴,成功沉淀得到五唑钴金属盐。研究发现,pH值越低,有机酸盐的去除效率越高,五唑钴纯度越好。确定了五唑钴的适宜分离纯化条件:pH值为3,氯化钴与原料4-氨基-2,6-二甲基苯酚(1)的摩尔比为0.26∶1。离子色谱表明,所得五唑钴经简单重结晶后纯度高达97.9%。在此基础之上,研究了沉淀法对其它五唑金属盐的适用性。结果表明,沉淀法亦适用于五唑铁、五唑亚铁和五唑铜等金属盐的分离纯化。  相似文献   
7.
《Ceramics International》2022,48(10):14349-14359
The influence of heat-treatment temperatures (700 °C, 900°C, 1200 °C) on the phase, physical properties, crystallization rate, and in vitro properties of the solution combustion synthesized silicon-doped calcium phosphates (CaPs) were investigated. The thermodynamic aspects (enthalpy, entropy, and free energy) of the synthesis process and the crystallographic properties of the final samples were first predicted and then confirmed using density functional theory (DFT). Results demonstrated that the crystallization rate was controlled by the fuel(s) type (glycine, citric acid, and urea) and the amounts of Si4+ ions (0, 0.1, 0.4 mol). The highest calculated crystallization rate values of the un-doped, 0.1, and 0.4 mol Si-doped samples were 64%, 22%, 38%, respectively. The obtained results from the DFT simulation revealed that crystal growth in the direction of c-axis of hydroxyapatite (HAp) structure could change the stability of (001) surface of (HAp). Also, the computational data confirmed the adsorption of Si–OH groups on the (001) surface of HAp during the SCS process with an adsorption energy of 1.53 eV. AFM results in line with DFT simulation showed that the observed change in the surface roughness of Si-doped CaPs from 2 to 8 nm could be related to the doping of Si4+ ions onto the surface of CaPs. Besides, the theoretical and experimental investigation showed that crystal growth and doping of Si4+ ions could decrease the activation energy of oxygen reduction reaction (ORR). Furthermore, the results showed that the crystallized HAp structure could have great potential to efficiently reduce oxidative stress in human body.  相似文献   
8.
Heat-integrated water network synthesis (HIWNS) has received considerable attention for the advantages of reducing water and energy consumptions. HIWNS is effective in water and energy sustainability. Mixed integer non-linear programming (MINLP) is usually applied in HIWNS. In this work, a novel nonlinear programming (NLP) was proposed for HIWNS by considering wastewater reuse and wastewater regeneration reuse. Integer variables are changed to non-linear equation by the methods for identifying stream roles and denoting the existence of process matches. The model is tested by examples with single and multiple regeneration unit problems. The testing results showed that the NLP is an alternative method for HIWNS with wastewater reuse and regeneration reuse.  相似文献   
9.
Production of methanol, as a green energy, from syngas is coming into focus. However, natural gas based methanol plants, which are used steam reforming of methane for syngas production, have a high CO2 emission resulting in the global warming. In this study, a novel process for methanol synthesis is proposed to reduce CO2 emission. In this regard, natural gas and flue gas are fed to a parallel-series system with tri and dry reforming of methane for syngas production with the optimized stoichiometric number. Then, the produced syngas is converted to methanol in a reactor. Finally, the produced methanol is purified by two distillation towers. The proposed method is compared to a referenced method in the view of technological, economic and environmental metrics. The techno-economic-environmental analysis of the processes reveals that not only the proposed method, as compared to the referenced one, increases CO2 conversion from 20.93% to 99.22%, but also it is more economical and environmentally friendly. In addition, the global warming potential of the proposed method is almost 60% lower than that for the referenced method due to the lower CO2 emission. Therefore, the proposed method can save above MUS$ 8 a year by CO2 capture.  相似文献   
10.
To improve the fuel economy, it is crucial to promote the low-temperature performance in eliminating diesel emissions. The work investigates the impact of different MnO2/Mn2O3 phase ratio on the low-temperature performance of Pt-based monolithic diesel oxidation catalyst. Near equal ratio of MnOx phase could form the three-phase (platinum, MnO2, Mn2O3) interfacial structure, leading to the smaller platinum particle size and exhibiting the higher interface rate (1.6–11.1 times) than other mono-manganese oxide with platinum. Besides, the higher oxygen mobility and more active oxygen species could be contributed to the positive effect of Pt/MnOx interface, which are prevalent to activate the reactant and greatly enhance the TOF value (1.4–20.8 times). The results imply that the modification of multi-phase metal/oxide interface is potential in dispersing platinum for greatly enhancing the catalytic efficiency.  相似文献   
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