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91.
Cyclodextrins (CyDs) complexes with vanadium-substituted heteropoly acids (PMoV n -β-CyDs, n = 1, 2) were prepared by simple mixing and their structures were characterized by FT-IR. Among various catalysts, PMoV1-β-CyDs, an efficient phase transfer catalyst, exhibited the highest yield (13.1%) of phenol without observing the formation of catechol, hydroquinone and benzoquinone in direct hydroxylation of benzene to phenol in 80 vol% aqueous acetic acid with molecular oxygen and ascorbic acid used as the oxidant and the reducing reagent, respectively. The influences of the reaction temperature, the pressure of oxygen, the amount of ascorbic acid, the amount of catalyst, and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation. 相似文献
92.
目的 观察三七总皂甙的新剂型——洛泰(血塞通粉针剂,主要成分为三七总皂甙)对大鼠急性心肌缺血的保护作用。方法 采用微量异丙肾上腺素(ISO)恒速静注造成大鼠急性心肌缺血的模型,动态观测Ⅱ导联心电图S-T段的变化,以ST段降低及ΣST为指标反映缺血程度。结果 静脉注射洛泰50,100mg·kg-1,对ISO诱导大鼠急性心肌缺血有一定程度的保护作用,呈剂量依赖性,其中以100mg·kg-1组对心电图的改善作用较明显。灌胃给予洛泰对ISO诱导大鼠实验性急性心肌缺血也有一定程度的减轻作用,但没有统计学差异。结论 采用改进的大鼠急性心肌缺血模型具有稳定性和重复性好、快捷有效、易掌握、耗费药品少等优点,适宜于初筛药物。同时实验结果提示静脉和灌胃两种途径给予洛泰对大鼠急性心肌缺血均具有一定程度的保护作用。 相似文献
93.
The conversion of palm oil to hydrocarbons using a shape selective zeolite catalyst is reported in this work. Palm oil was passed over HZSM-5 catalyst in a fixed bed micro-reactor and the reactor was operated at atmospheric pressure, a temperature range of 360 to 420°C and weight hourly space velocity (WHSV) of 2 to 4 h?1. The main objective was to study the effect of reaction temperature and oil space velocity on the conversion and selectivity of gasoline range hydrocarbons. The results show that 40 to 70wt% of the palm oil can be converted to aromatics and hydrocarbons in the gasoline, diesel and kerosene range, light gases, coke and water. The maximum gasoline range hydrocarbons yield of 40wt% of total product formed was obtained at 400°C and 2 h?1 space velocity. 相似文献
94.
95.
To measure miss distance for antiaircraft projectile,a radial velocity identification and positioning method with a single radar is proposed.By analyzing the spatial resolution of multi-frequency ranging radar,the discrimination and testing model of this radar for multi-targets (projectile and target) is established to analyze the systematic error of antiaircraft miss distance.Then through the aerial target flight test and contrast test with optical test equipment,the validity of the measurement method is verified.This new method has the potential to be used in the measurement of antiaircraft projectile miss distance. 相似文献
96.
97.
Chunhua Ma Zhiwen Lu Zhiguo Zhong Yumin Leng Tie Ye Yazhong Zhao Junbao He 《Journal of Phase Equilibria and Diffusion》2018,39(6):800-809
The phase equilibria and compositions in the magnesium (Mg) rich part of the Mg-Er-Si ternary system at 300 and 400 °C were systemically investigated through the equilibrated alloy method by using x-ray diffraction and scanning electron microscopy assisted with energy dispersive spectroscopy of x-ray. The results show that in the composition range of our study the equilibrium of Er2MgSi2 with the (Mg) solid solution, Er5Mg24, and Mg2Si exists at both temperatures. A certain amount of Mg atoms can be replaced by Er and Si element, but they cannot replace Mg atom simultaneously. The homogeneity ranges of Mg solid solution as well as the solid solubilities of the intermediate phases at different temperatures are reported. 相似文献
98.
Shape‐memory polymer (SMP) materials have several drawbacks such as low strength, low stiffness and natural insulating tendencies, which seriously limit their development and applications. Much effort has been made to improve their mechanical properties by adding particle or fiber fillers to reinforce the polymer matrix. However, this often leads to the mechanical properties being enhanced slightly, but the shape‐memory effect of reinforced SMP composites being drastically reduced. The experimental results reported here suggested that the mechanical resistive loading and thermal conductivity of a composite (with hybrid filler content of 7.0 wt%) were improved by 160 and 200%, respectively, in comparison with those of pure bulk SMP. Also, the glass transition temperature of the composite was enhanced to 57.28 °C from the 46.38 °C of a composite filled with 5.5 wt% hybrid filler, as determined from differential scanning calorimetry measurements. Finally, the temperature distribution and recovery behavior of specimens were recorded with infrared video in a recovery test, where a 28 V direct current circuit was applied. The effectiveness of carbon black and short carbon fibers being incorporated into a SMP with shape recovery activated by electricity has been demonstrated. These hybrid fillers were explored to improve the mechanical and conductive properties of bulk SMP. Copyright © 2010 Society of Chemical Industry 相似文献
99.
The purpose of this study is to investigate the mixture formation processes of a third-generation spray (TGCS), an impinging spray that is intended to be applied in mixture preparation for homogeneous charge compression ignition (HCCI) diesel combustion. The spray visualization is performed in a constant-volume vessel by high-speed photography, to investigate the characteristics of the TGCS, and also to provide a validation for numerical models. Then the behaviors of spray and mixture formation process in a constant-volume vessel and diesel in-cylinder conditions were examined numerically by FIRE v8.5 package. Results of the high-speed photography indicated that the TGCS is characterized by a flexible spray tip penetration and circumferential angle, depending on the impinging angle of the TGCS nozzle. Findings of the numerical simulations in a constant-volume vessel under the spray visualization conditions revealed that after the fuel jets had impinged on the guide wall, the TGCS has a much smaller fuel mass fraction compared with a free spray. Furthermore, simulation results under diesel engine conditions demonstrated that for the TGCS, the fuel-air mixture can achieve circumferential homogeneity at 2° CA after the start of injection (ASOI), and form a comparatively homogeneous lean mixture at 20° CA ASOI. 相似文献
100.
Yihan Liang Siqi Xiang Tongye Li Chong Yu Ke Leng Xinfang Zhang 《Journal of the American Ceramic Society》2021,104(12):6131-6143
Implementing pressure-assisted flash sintering of ZnO powder without pretreatment by a new experimental configuration is presented. Rapid and energy-concentrated heating of electrode-sample-electrode area by induction heating allows preheating and flash sintering of loose-pack powder in the die with pressure assistance. Using an insulated die enables the current to flow through the sample during flash sintering. ZnO ceramics with a relative density of 95.1% can be achieved in less than 3 min. The whole process includes 104 s of preheating by a low-power induction heating device and 30 s of flash sintering assisted by a pressure of 26 MPa using the pulsed direct current (DC). The process characteristics of pressure-assisted flash sintering using the pulsed DC are discussed. The effect of pressure on densification and grain size is analyzed in detail, and some potential mechanisms are provided. 相似文献