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1.
Satoshi Nogami Katsuhiko Minoura Nao Kiminami Yui Kitaura Hiromasa Uchiyama Kazunori Kadota Yuichi Tozuka 《Advanced Powder Technology》2021,32(5):1750-1756
Although curcumin is considered to have various therapeutic effects, its use as a functional food or supplement is restricted owing to its low water solubility and bioavailability. To increase the solubility of curcumin in water, the use of polyvinylpyrrolidone (PVP) and vinylpyrrolidone-vinyl acetate copolymers with a pyrrolidone skeleton was noted to be promising. In particular, the bi-component formulations of curcumin/PVP prepared through spray drying exhibited an amorphous state in powder X-ray diffraction observations and temporally increased the apparent solubility of curcumin to over 5000 times that of untreated curcumin; nevertheless, after 24 h, the solubility decreased owing to the unstable supersaturated state of curcumin. The addition of α-cyclodextrin (α-CyD) in the bi-component curcumin/PVP formulation helped maintain the supersaturated state of curcumin, whereas the addition of β- and γ-CyD led to the collapse of the supersaturated state. The addition of α-CyD can likely help inhibit the nucleation and crystal growth of curcumin, through the interaction among the solubilized units of curcumin/PVP and α-CyD. 相似文献
2.
本文利用现场同步加速X-射线衍射、等温量热仪和膨胀测量等手段,研究了在20℃,100%相对湿度下,由25%(重量比)的铝酸钙水泥、12.5%的硅酸盐水泥、12.5%的β-半水石膏和50%的水组成的浆体的水化。水化伊始,首先形成了石膏和钙矾石,同时半水石膏也相应消耗(0-45min内)。随后石膏继续消耗,钙矾石持续形成,2h45min后石膏消耗完毕,铝酸盐-AFm开始形成,同时钙矾石的数量在7h内保持不变。热曲线的第一个峰源自机械搅拌、初始润湿和溶解,还有钙矾石和石膏的形成,第二个峰为石膏被钙矾石所替代,第三个对应于铝酸盐-AFm的形成。石膏被钙矾石替代伴随着0.7%平均线性膨胀。 相似文献
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本文利用X射线衍射仪与差示扫描量热仪(DSC)分别研究某地原油加剂前后的蜡晶结构和结晶动力学。X射线衍射研究表明:某地原油加剂前后的蜡晶均为斜方晶体,但加剂原油的晶体体积要比未加剂原油的晶体体积大。DSC用于结晶动力学研究,首先测量正二十三烷(C23)、正二十四烷(C24)在不同降温速率下的DSC谱图,得出结晶放热峰值随降温速率升高而线性减少的关系;随后研究某地原油、分离出的蜡、加剂原油在不同降温速率下的DSC谱图,计算出相应的结晶动力学常数。 相似文献
5.
Nanocrystalline anatase was obtained from ionic liquid-like precursors containing hexafluorotitanate-organic salts and less than 25 wt.% of water, and using boric acid as fluoride scavenger. Two alternative heating methods were explored using either a conventional oven or a domestic microwave apparatus. A significant reduction in the reaction time from 24 h to only few minutes was obtained using the microwave route. The as-prepared materials were characterized by X-ray diffraction, transmission electron microscopy, nitrogen sorption analysis, and attenuated total reflectance Fourier transformed infrared, X-ray photoelectronic and Raman spectroscopes. The convenience of using the microwave heating option was a function of the organic cation present in the precursor. Thus, organic ammonium cations containing only hydrocarbon substituents, such as diethylammonium, phenylammonium and benzyltrimethylammonium led to the precipitation of nanocrystalline anatase powder with high specific surface area (up to 120 m2 g−1) in a short processing time (1-3 min). Otherwise, alcohol and carboxylate functionalized cations decomposed under microwave treatment. Moreover, the choice of the organic cation allowed tuning several properties of the end material, such as particle size and pore morphology. 相似文献
6.
Preparations of PbS-coated titanium dioxide (TiO2) and lead sulfide (PbS) nanoparticles under ultrasonic field at the multibubble sonoluminescence (MBSL) conditions were tested in water solutions. Under the optimal MBSL conditions (20 kHz and 220 W power input), PbS nanoparticles (diameter = 40-50 nm) were prepared by treating lead nitrate and thioacetamide for 20 min in water solutions. The size of PbS nanoparticles was found to be easily increased to about 90 nm in diameter by increasing the reactant concentration twice. A similar sonochemical reaction with TiO2 nanoparticles (about 20-30 nm in diameter) gave rise to PbS-coated TiO2 nanoparticles with a core/shell structure. The PbS thin film coating was quite uniform and the average coating depth of PbS on the TiO2 nanoparticles was about 2-3 nm under the described conditions. It is interesting to note that the coating depth was found to be controlled to 2-10 nm range by increasing the amounts of reactants for Pb and S twice with a sonication time of 30 min. 相似文献
7.
Jiaxiong XuRuohe Yao 《Thin solid films》2011,520(1):515-518
Boron-doped or phosphorus-doped β-FeSi2 thin films have been prepared on silicon substrate by magnetron sputtering. Effects of Si/Fe ratio on the boron and phosphorus doping efficiencies have been studied from the resistivities of doped β-FeSi2 thin films and current-voltage characteristics of doped β-FeSi2/Si heterojunctions. The experimental results reveal that the carrier concentration and doping efficiency of boron or phosphorus dopants at the Fe-rich side are higher than that at the Si-rich side. The effect of Si/Fe ratio can be deduced from the comparison of the formation energies under two extreme conditions. At the Fe-rich limit condition, the formation energy of boron or phosphorous doping is lower than that at the Si-rich condition. Therefore, the activation of impurities is more effective at the Fe-rich side. These results demonstrate that the boron-doped and phosphorous-doped β-FeSi2 thin films should be kept at the Fe-rich side to avoid the unexpected doping sites and low doping efficiency. 相似文献
8.
LaMnO3+δ and La0.7Ca0.3MnO3 were synthesized from La2O3(La(OH)3), CaCO3 and MnO2 powder mixture with solid-state reaction technique. X-ray diffraction and thermal analysis were employed in the present study on the process of synthesizing of the two compound powders. The kinetic study on solid-state reaction between La2O3 and MnO2 in the powder mixture was isothermally carried out for LaMnO3+δ formation. The result showed that the reaction process was controlled by three-dimensional solid-ionic diffusion. Both Jander and Ginstling-Brounstein model can be used to describe the reaction kinetics satisfactorily. The relevant apparent activation energy values obtained were as great as 205 ± 11 and 189 ± 8 kJ/mol. The reaction process of La0.7Ca0.3MnO3 preparation from La2O3, SrCO3 and MnO2 powder mixture was also studied using X-ray diffraction and thermal analysis. The result indicated that the following steps composed the overall reaction: the decomposition of the reactant; the formation of La1−xCaxMnO3+δ; La2O3 and Mn3O4 reacted with La1−xCaxMnO3 to form final La0.7Ca0.3MnO3 phase. The latest step was the most time-consuming one among others in the overall reaction. 相似文献
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Cold working processes due to inhomogeneous and strong plastic deformations result in the formation of residual stresses and texture within the components. The texture evolution has a strong influence on the residual microstresses and produces non-linear d vs. sin2 ψ-curves. The texture evolution and the resulting non-linear d vs. sin2 ψ-curves are calculated here using the Taylor–Bishop–Hill theory and an elastic unloading model. Examples are given for the inverse pole figure and non-linear d vs. sin2 ψ-distributions due to cold torsion of an austenitic steel. 相似文献